A Guide to Bass Management (Part II)

[Big Daddy]

Please review A Guide to Bass Management (Part I).

A GUIDE TO BASS MANAGEMENT (PART II)

It is generally accepted among professional poker players that you do not play and bet with the cards that you have, but rather you play and bet against the other players. As far as bass management and setting the crossovers are concerned, it is pretty much the same. The room perhaps plays a bigger role than your speakers in determining how the bass should be played in your room.

There are normally several reasons why bass management should be performed and send the low frequency waves to the subwoofer. The reasons are as follows:

1. Even if you are using tower speakers with good low frequency extension, they will not have as much box volume as a dedicated subwoofer and as a result, they will not necessarily go down to the lowest frequencies as linearly and free of compression as your subwoofer.
2. In most cases, the quality and the low frequency extension of subwoofer drivers is better than the woofers inside the majority of speakers. Therefore, it makes sense for better and more capable driver to generate the more difficult bass frequencies.
3. By blocking the lower frequency waves from the regular speakers, you will indirectly protect them from any possibility of distortion or damage to their drivers.
4. You have flexibility in placing your subwoofer(s). As far as the front, center, and the surround speakers are concerned, you normally have very little flexibility in positioning them properly.
5. If the subwoofer and the front speakers play the same bass frequencies, there will be a possibility of phase cancellation of certain bass frequencies. Subwoofers have phase control and flexibility in placement. Speakers don't.
6. As most subwoofers are powered and have their own dedicated amplifiers, by redirecting the relatively power-hungry lower frequencies from the speakers, you will free up the receiver/amplifier from powering these frequencies and as a result it will have better dynamics, greater headroom, and less distortion.
7. Audio calibration programs such as the Audyssey MultEQ apply more filters to subwoofers and you will get much better bass performance. The MultEQ subwoofer filters have 8x higher resolution than the filters for the other speakers.
8. Finally, and perhaps most importantly, there are solid scientific reasons why it is best to separate the low frequency drivers from the rest of the speaker drivers and place them in a more appropriate location to avoid the problems associated with standing waves and room modes. It highly recommended that you read and review A Guide to Subwoofers (Part II): Standing Waves & Room Modes.

Small Versus Large:

If you have a capable subwoofer or multiple subwoofers in the room, all your speakers become SMALL by default. This rule applies to multi-channel speaker systems as well as stereo speakers. The reasons have absolutely nothing to do with the physical size of your speakers or the low frequency extension of your front or surround speakers. It has everything to do with the source of bass waves in the room and their interaction with the room boundaries. In most cases, you do not have that much flexibility with the placement of the front or surround speakers. However, a subwoofer can be placed almost anywhere out of the way for the most optimum bass response.

The most important research about speakers and subwoofers have been done by Dr. Floyd Toole and his associates (Sean Olive, Allan Devantier, Todd Welti, etc.) at the National Research Council of Canada (NRC) and at Harman International. They did multiple studies in anechoic chambers and real rooms to study the behavior of low frequency waves. They also ran many simulation models. One of the most important things that they found was that when all your speakers are running full-range in the room, you will experience a huge difference in the level of bass that is generated by each speaker. It is best to quote Dr. Toole from one of his scientific articles.

http://www.harman.com/EN-US/OurCompa...ndRoomsPt3.pdf

When a full-range signal is panned to each of the loudspeakers in turn, and measurements are made at the listening position, we find hugely different bass responses for each of the loudspeakers. The differences are as large as 40dB in this room, and the biggest ones are all at low frequencies. The reason, the woofers each have very different acoustical “coupling” to the room resonances because they are in different locations. This will be different for every different room. Again, referring back to the “circle of confusion” the bass that was heard in the control room will not be the same as that heard at home. It cannot be.

BassManagement.jpg
We have five very different bass sounds, one for each channel!

Attempting to improve the situation by panning the bass to pairs of loudspeakers changes things, but does not remove the problem. Anybody think that an “ideal” room can help this? An anechoic room would, but none of us would wish to live in one.

And this is why bass management and subwoofers make sense. Now we can place the woofers where they perform optimally for a specific room with a specific listening position. We can place the satellites (a term that seems inappropriate for some of the large capable loudspeakers that we use in the high-passed channels) where they need to be for directional and imaging effects. In other words, we design the low-frequency portion of the system separately because rooms force us to do so. This is the only way that we can get good bass in any room, and have any hope of having similarly good bass in different rooms. Remember about preserving the art?

Why Don’t People Like to Set Their Speakers to Small?

People have a psychological difficulty with the word SMALL. They have spent good money on their front speakers and get insulted when the AVR sets them to SMALL. Remember that this is not a personal insult against you or your speakers. Small does not refer to any part of your anatomy. My Definitive Technology front speakers have 15" built-in subwoofers with built-in 300 watt amplifiers. Their low frequency extension is around 15Hz. When I set the front speakers to SMALL and let the 4 external subwoofers handle the lower frequencies, the quality of the sound (both 2-channel music and multi-channel movies) improves significantly.

It is helpful to redefine the words SMALL and LARGE to:

LARGE = No Bass Management
SMALL = Speakers are Bass Managed

Many audiophiles and worshipers of two-channel music are dead set against subwoofers. To them, the idea of 2.1 system is analogous to blasphemy. Perhaps, they should open their minds a little and realize that we are just replacing and separating the low frequency generators out of the speakers and positioning them in a more appropriate location because the room modes force us to do this.

Double Bass

When you use these options, Bass management becomes enabled for Large (Full Band) speakers. The frequency below which the signals from the LARGE (FULL-BAND) speakers are sent to the subwoofer is set automatically in the Onkyo or can be changed to any number you like in Denon's implementation.

• If all the individual speakers are set to SMALL and the subwoofer is set to LFE only in the A/V receiver's menu, all the LFE + Redirected Bass from the Small speakers will go to the subwoofer.
• If all the individual speakers are set to SMALL and the subwoofer is set to Double Bass, LFE + Main, or Both, the LFE + Redirected Bass will go to the subwoofer.
• If all speakers are set to LARGE (FULL BAND) and the subwoofer output is set to LFE in the AV receiver's menu, you will only get the discrete .1 LFE signals directed to the sub woofer. There will be no redirected bass from the other speakers.
• If any speaker such as the front speakers is set to LARGE and the subwoofer is set to Double Bass , LFE+Main, or BOTH in the AV Receiver's menu, the LFE + Redirected Bass From Small Speakers + Bass from the Large Speakers will be sent to the subwoofer.
• If the subwoofer is set to NO in the AV receiver's menu, on many receivers such as Denon, the front speakers will automatically becomeLarge by default and all the LFE + Redirected Bass from the Small speakers will go to the front speakers.

As I explained in A Guide to Bass Management (Part I), using Double Bass (Onkyo) or LFE+Main (Denon) or Both (Yamaha) is not a good idea. There are several problems with this option:

1. There possibility of phase cancellation when the LARGE speakers and the Subwoofer play the same bass frequencies.
2. In the overlap frequency region between the subwoofer and the Large speakers, the bass frequencies are doubled and tend to become bloated, boomy, and a bit exaggerated.
3. When you use two or four subwoofers, the level of each one can be controlled independently and the total level can also be controlled. However, there is no way to only lower the level of those same bass frequencies in the LARGE speaker. If you lower their level in the receiver, the level of all the frequencies going to the those speakers will be lowered.
4. As I have mentioned several times before, calibration programs such as Audyssey apply more correction filters to the subwoofer frequencies. If the same frequencies are sent to the large speakers and the subwoofer at the same time, you will apply higher resolution filters to the same frequencies in the subwoofer and lower resolution filters to the same frequencies going to the front speakers. When the two low frequency sources are combined, we will have no idea what quality of low frequency sound we will be hearing.

Chris Kyriakakis of Audyssey has discouraged people from using Double Bass numerous times in his own blogs on Audyssey's website or in Audyssey's thread on the AVS Forum. Read Small vs Large and Subwoofer Setup & MultEq.

According to Chris (he heard it directly from a receiver manufacturer), the Double Bass option was adopted by the manufactures because too many people were upset and offended that the receiver set their expensive and what they thought to be excellent speakers to SMALL. As a result, Double Bass (LFE+Main) was created to redirect the lower frequencies to the subwoofer without setting the speakers to SMALL.

http://www.avsforum.com/avs-vb/showp...ostcount=10768

LFE+Main should not even be an option because it just causes duplication of bass content by sending it to both the sub and any speakers set to Large (Full Range).

A "high ranking" official in a "well-known" AVR company told me that LFE+Main was invented to appease customers that were upset when their speakers were being set to Small. These customers had a complete lack of understanding of what Small means (i.e. turn on bass management and redirect the bass to the subwoofer) and felt... inadequate. LFE+Main allows them to set their speakers to a more manly Large and still have bass management. But it's a compromise that can cause boomy bass if the speaker and subwoofer overlap in the lower frequencies.
__________________
Chris

http://www.avsforum.com/avs-vb/showp...ostcount=32160

LFE+Main will indeed send bass to the sub even from Large speakers. But, it is also not recommended because you end up overlapping a certain region of the bass and that usually causes muddy bass.
__________________
Chris

Phase Cancellation

Phase cancellation is a type of wave interference. Wave interference occurs in all small home theater rooms. Even when we use one subwoofer, it will suffer from wave interference because the lower frequencies emanating from the subwoofer will interfere with their reflection from the room boundaries and create standing waves and room modes. There are other types of interference that we call comb filtering or lobing.

Phase interference can generally occur because of timing differences in the frequency waves. The following diagrams demonstrate different type of phase interference.

When two sound waves are combined together, they will form a resultant wave that we hear. At a given point of observation, the combination of the two waves will result in some in-phase (synchronous) frequencies that are added constructively and cancellation of some out-of-phase (asynchronous) frequencies. Between these two extremes there are many intermediate cases. This can produce uneven sound coverage over an audience area.

When similar independent waves are combined, the result can be either constructive or destructive interference, depending on whether the waves are in phase or out of phase. This interference occurs when the waves have the same or nearly the same frequency. Constructive interference will enhance sound. Destructive interference will weaken sound. If two identical waves are 180 degrees out of phase, they will cancel out. Whether the interference is constructive or destructive, the individual waves continue to exist separately. The interference itself is merely the effect of the waves together at one point in space.

Source: Headwize.com


Two waves in phase and two waves 180° out of phase.
Source: Wikipedia

The animation in the following shows two waves traveling in the same direction. The phase difference between the two waves varies with time so that we see constructive interference when maximum points are aligned (peak) and destructive interference when minimum and maximum points are aligned (null). This illustrates the problem with horizontal center channel speakers and also why it is important to adjust the subwoofer’s phase control with respect to the main speakers so that we obtain maximum output.

Animation courtesy of Dr. Dan Russell, Kettering University

Lobing:

Single Source, Single Frequency



Two Sources, Single Frequency



Two Sources, Single Frequency (Larger Picture)
Source: Live Sound International

Comb Filtering:

Demonstration of Comb Filtering
Source: Live Sound International

Solutions to Phase Cancellation:

There are basically several types of solutions to wave interaction:

1. Move the sources of the frequency waves around in order to create the best frequency response in the main listening area and increase the size of the sweet spot. This means moving the speakers or the subwoofers around. As I have mentioned before, you have limited ability to move the 5 speakers around. Subwoofers are a lot more flexible and can be placed in different locations in the room for better bass response. It is very difficult or almost impossible to localize lower frequencies so it should not make any difference where the subwoofer is placed.
   
   
2. Adjusting the Subwoofer’s Phase control may work in some situations, but may have no effect in other situations.
   
   When the woofer on the sub and the woofers of the front speakers move in and out in sync with each other, the system is said to be in phase. When the speakers and the subwoofer are moving out of sync with each other, the subwoofer and the front speakers’ bass overlap and cancel each other. In this case the system is said to be out of phase, resulting in less bass.
   
   Unfortunately, there may be another problem between the main speakers and the subwoofer. If the main speakers are producing bass at the same time as the subwoofer, at some points the bass will reinforce each other. At other points the bass will cancel each other. The solution is to allow only the subwoofer to reproduce bass by setting the front speakers to small in the receiver’s setup menu. This can yield a smoother bass response throughout the entire room.
   
   To get the best bass response, you should set the phase (polarity) of the subwoofer(s) to deliver the highest output at the listening position. This can be achieved with the help of a test signal at the crossover frequency and an SPL meter. You should run this test several times by changing the polarity of the subwoofer and measuring the bass response on the SPL meter. Select the phase option that results in the highest bass response. If you don’t have an SPL meter, you will have to trust your ears.
   
   Fortunately, most subwoofers have a switch to change their polarity. If the subwoofer does not have a phase switch, you can change the polarity of the main speakers by switching the positive with the negative speaker wires (the black wire goes to the red terminal and the red wire to the black terminal). Some subwoofers have a “variable phase control”. This control can be set continuously between 0 and 180 and allows for a more precise phase control of the subwoofer.
   
   When setting the subwoofer phase by ear, play some music (not a movie) that has a repetitive bass line. Switch the polarity several times and choose whichever setting sounds “faster” or “fuller”. If you do not hear any difference, leave the phase switch at “0" or “normal”.
   
   If you are using two subwoofers, position them properly and adjust the phase of one of the subwoofers for optimum results.
   
   
3. Equalization and calibration is another option that people use to smooth out the frequency response of the speakers. The built-in calibration/equalization programs inside the AV receivers such as Audyssey have higher resolution correction filters to deal with the lower frequencies coming out of the subwoofers. However, it is important to understand that equalizers can only do limited things. They are generally better for lowering the peaks than filling the troughs.
   
   
4. The last option is room treatment. Wall treatments such as foams are generally more effective in controlling reflections of higher frequencies from the room boundaries. Lower frequencies are much more difficult to contain. Many bass traps may be effective to deal with higher bass frequencies above 120Hz. Most of them may be ineffective in dealing with ultra low frequencies below 120Hz.

Is there a Standard Low Pass Cutoff Frequency such as 80Hz?

Over the years, many experiments have been performed to determine our ability to localize lower frequencies. One of the most extensive surveys was conducted in Europe. These experiments demonstrated the following:

1. The mean frequency that the vast majority of humans began to distinguish the subwoofer directionality was 185 Hz.
2. 80 Hz was the minimum frequency below which no one heard directionality. For more information, check the exercises below.

After analyzing the results, they concluded that that 80Hz crossover is the best choice for receivers with fixed-frequency filters.

If you believe that you can localize the frequencies below 80Hz in your room, it is most likely that you are hearing the the upper harmonics of those bass frequencies and those can clearly be localized. The solution is better room treatment and bass traps.

There really isn't a standard low pass cutoff frequency that applies to all situations. The THX suggestion to use 80Hz applies only to THX Certified Speakers. These speakers are required to have low frequency extension down to 80Hz. It is not a blind recommendation that applies to all speakers. It doesn't make much sense to set the HPF to 80Hz, for example, if the other speakers are small satellites and their frequency responses do not go below 100Hz. Even though bass frequencies above 100Hz may become directional, a higher high pass filter such as 120Hz may be required.

Furthermore, look at the following table and check the wavelengths of the bass frequencies. You will notice that below 80Hz to 120Hz, these long wavelengths can create havoc in a small home theater room. I don't believe any one of you has an HT room as large as a movie theater. As long as you are a normal human being and live in a normal house, you should let the lower frequencies below 80Hz to 120Hz be handled by strategically placed subwoofers in the room. If you don't listen to me, I shall strike you with the 14ft wavelength of the 80Hz frequency.

As far as subwoofers are concerned, most of them cannot handle the frequencies above 120Hz to 150Hz and tend to distort. They are not suitable for higher crossover filter points. It is important that we block these higher frequencies away from the subwoofers. In addition, some people complain and believe that they can localize 100 Hz. It is possible that the crossover filters in their surround processor or receiver are not fast enough in their transition. Although 100Hz is very difficult to localize, the frequencies above that are easier to localize. Keep in mind that the slope of the crossover filter is the real issue. There is no doubt that 400Hz and 800Hz can easily be localized. See how these two frequencies are attenuated by a 12dB filter when the crossover is set at 100Hz and 50Hz.

Example 1. Set the LPF to 100Hz. Assume the slope is -12dB.

100Hz: -0dB
200Hz: -12dB
400Hz: -24dB
800Hz: -36dB

Example 2. Set the LPF to 50Hz. Assume the slope is -12dB.

50Hz: -0dB
100Hz: -12dB
200Hz: -24dB
400Hz: -36dB
800Hz: -48dB

If you compare the results of Example 1 with the results of Example 2, you will notice that if the crossover filter slope is 12dB, the 50Hz crossover setting is more effective than 100Hz in blocking the higher frequencies from the subwoofer. It will make the location of the subwoofer more invisible.

Now, let’s redo the above examples by setting the crossover filter’s slope to 24dB.

Example 3. Set the LPF to 100Hz, Assume the slope is -24dB.

100Hz: -0dB
200Hz: -24dB
400Hz: -48dB
800Hz: -72dB

As you can easily see, a subwoofer with a 12 dB/octave crossover filter is not suitable for a higher crossover frequency. Fortunately, most modern high end AVR receivers and processors have low pass filters with fourth order (24dB) slope. The high pass filters generally have second order (12dB) slope. Let's see what happens when you set the HPF of the front or center to 80Hz or 100Hz.

Example 4. Set the HPF filter to 80Hz. Assume the crossover slope is -12dB.

80Hz: -0dB
40Hz: -12dB
20Hz: -24dB

Example 5. Set the HPF filter to 100Hz. Assume the crossover slope is -12dB.

100Hz: -0dB
50Hz: -12dB
25Hz: -24dB

As you can see, even if the crossover is set to 100Hz, the lower frequencies are not completely cut off from the front sound stage.

In most cases, it is best to set all speakers to SMALL and set their crossovers to the same point. If the crossover values are not the same, there may be some phase issues when the processor has to add different frequencies and sum them with the LFE channel before it sends them all to the subwoofer.

SUMMARY AND CONCLUSIONS

1. In a small home theater room, it makes sense to separate the low frequency drivers (subwoofers) from the main speakers and place them in a more appropriate and optimal position. This has absolutely nothing to do with the quality, design, or low frequency extension of the main speakers. The main reason is because the room forces us to do this and not because the speakers are deficient.
2. The low frequency sound waves have very large wavelengths. These waves will interact with the room boundaries and create standing waves and room modes. As a result, bass will become very uneven across the room. These modes occur in all small rooms and for all speakers/subwoofers and depend on the dimensions of the room and not the quality or design of the speakers/subwoofers.
3. The location of the bass generator and the location of the listener determine whether certain low frequencies are energized or cancelled. If your chair or sofa happens to be located in one of the troughs of the standing waves, you are not going to hear much deep bass. But if you get up and walk a few feet back, or to the left, or to the right, chances are you will hit one of the peaks and the bass will be very strong, perhaps too much of a good thing.
4. Standing waves in small rooms is a problem associated with low frequency waves and not high frequencies. All small rooms are subject to standing waves. It is a well-known fact that cubic rooms are the worst as far as bass performance is concerned. First of all, such a room will have a very high ceiling and will be impractical. Secondly, even if we make the ceiling height half of the other two dimensions, the room resonant frequencies will all line up together like Pawns on a chessboard with big gaps between them. As a result, some frequencies will be overly accentuated, and others not adequately represented. A room is normally better if its resonant frequencies are more uniformly distributed.
5. Standing waves occur even in non-rectangular rooms. However, their location becomes unpredictable and difficult to calculate. The advantage of a rectangular room is that you can easily calculate the location of the room modes. This is what Dr. Toole has to say about non-rectangular rooms:
   

   NonRectangular Rooms.jpg

6. The most appropriate solution to even out the bass performance across the room is to place 2 or 4 subwoofers in the room and set the other speakers to small with appropriate crossover frequencies. Some bass equalization is generally required. However, remember that an equalizer will solve some problems, primarily those related to peaks. A null is an entirely different situation and no amount of boost can fill a room-induced null. Think of it as a water drain. No amount of water can fill a drain.
   If you own one or more capable subwoofers, all the other speakers in the room become small by default. Again, this is not because your main speakers are deficient. As I said before, the room is the real culprit.
7. Depending on the capabilities of your speakers and their location in the room, a crossover frequency between 60Hz to 120Hz is appropriate for the vast majority of people.
8. In large halls, such as movie theaters, large auditoriums, large indoor stadiums, or outdoors, we don’t generally worry about low frequency standing waves.
9. Room treatment is effective to control the higher frequencies. However, they are generally very ineffective for frequencies below 100Hz. Although an anechoic chamber has better acoustics than even a well-treated room, manufacturers and researchers tend to go outdoors to perform tests on very low and deep frequencies.
10. The laws of physics do not stop working in your room because you feel a certain way or believe your speakers/subwoofers are designed a certain way or they are too good and too expensive to be subject to the effects of room modes.
11. Tower speakers made sense in the past in the era of stereo. However, they have become almost obsolete because of three reasons:
    1. The availability of advanced receivers/processors and their sophisticated calibration programs and crossover settings.
    2. The availability of very good powered subwoofers with excellent low frequency extension at very reasonable prices.
    3. The increase in the level of knowledge and availability of information as far as wave interaction, room modes, and bass performance are concerned.
12. Instead of wasting too much money on big tower speakers, it makes more sense for the vast majority of home theater users to spend their money on mid-sized front speakers that have excellent mid-range and high frequency performance and spend the additional funds that they will save on 2 or 4 quality subwoofers. In the majority of cases, the bass will be more even across the room and superior to the bass generated by tower speakers only.

For additional information, read the following:

http://www.hometheaterhifi.com/techn...equencies.html
http://www.hometheaterhifi.com/techn...und-sound.html

[Big Daddy]

PORT CHUFFING

Port Chuffing is a term used to describe the sound created by the port/vent during periods of high excursion of a bass driver. This can happen to any ported speaker system, not just subwoofers. Chuffing is created by large quantity of air moving at high speed within a speaker port tube.

Air moving below 10 meters/sec in a port generally will have no problems with compression, turbulence and noise. As the velocity of air is increased beyond this point (e.g., 20 meters/sec), turbulence occurs as air exiting the port is forced to slow down quickly as it encounters the surrounding still air. Chuffing usually occurs at or below the tuning frequency of the port.

The solution is to slow down the speed at which the air is moving. This can be done by one of the following methods:

1. Modify Port Dimensions: Increase the length of the port. If there is no room, the port can be bent
2. Flared Ports: Another solution is to flare the ends of the port tube to slow down the movement of the air. Flared ports cause the airflow to expand and loose speed, allowing higher speeds without turbulence. This method targets the air close to the walls of the port.
3. Passive Radiator: A passive radiator is basically a driver without the magnet or coil assembly. A passive radiator can be used instead of a port to avoid problems associated with port design and port chuffing. To prevent over-excursion of the passive radiator, it is recommended that you have twice the displacement of the driver. For example, a 10-inch driver would require a pair of 10-inch passive radiators with the same excursion, or a 12-inch driver with higher excursion.
4. Polyfill: Add polyfill to the enclosure. Polyfill has the indirect effect of making the subwoofer appear to be bigger by slowing down the movement of air and may help reduce port chuffing.

As you can see, the first three options are only available to DIY subwoofers/speakers builders. The fourth option can be used by all.

The only other solution that does not require modifying the sub enclosure has to do with lowering the level on the back of the subwoofer and/or the receiver. Port chuffing is generally a sign of a subwoofer/speaker being over-driven. When a subwoofer is placed in a a poor location in the room or your listening sofa/seat is placed in a poor location, the bass will be weak. As a result, one tends to overcompensate this by turning up the volume on the subwoofer. This causes the subwoofer to work much harder than it should, causing it to chuff and possibly damage the driver or the amplifier.

1. Placement: Good placement can help. For most rooms, corner placement is a possible solution. A subwoofer in a corner excites all room modes and play louder without needing additional amplifier power. The best part is that it is for free. Alternatively, you can use the Subwoofer Crawl Technique to find the best location for your subwoofer.
2. Multiple Subwoofers: Use multiple (2 or 4) subwoofers. Multiple subwoofers will give you additional output and allow you to turn down the level of each subwoofer. Moreiver, multiple subwoofer can even out the bass in the room and get rid off the peaks and valleys associated with standing waves and room modes.
3. Subsonic filter: It is highly recommended that you use a subsonic filter for all ported subwoofers. Some subwoofer amplifiers have this option. The Velodyne SMS-1 subwoofer equalizer/analyzer offers this option. Depending on the capabilities of your subwoofer, you should set the subsonic filter to 25Hz, 20Hz, 18Hz, or 15Hz to cut out the lower frequencies.
4. Use a Limiter Amplifier. A Llimiter Amplifier is an amplifier which uses a protection circuit to limit its output power to a predetermined level, regardless of input.

Subwoofers with large slotted ports should not have any port noise. There is a misconception that ported subwoofers are "slower" that sealed subwoofers. That is a myth. A properly designed ported subwoofer will offer greater efficiency and higher output when compared to a sealed subwoofer. Nonlinearity and distortion are more functions of the quality of the driver, not the cabinet.

Remember that a subwoofer driver can unload and lose control below the port frequency of the enclosure. Most normal human beings cannot hear frequencies below 25H-30Hz and only feel them. If you think you are hearing these lower frequencies, you are not. You are hearing the upper harmonics of these frequencies in your room. Go to an anechoic chamber and see if you can still hear 15Hz. If you want to feel these lower frequencies, Bass Shakers/Buttkickers/Tactile Transducers are much cheaper and do a much better job of shaking your butt.

POWER RATINGS FOR POWERED SPEAKERS/SUBWOOFERS

Amplifier ratings for powered speakers and subwoofers are meaningless. They only have a meaning for the designers. They should not even be published.

The amplifier power that you need for a particular powered speaker/subwoofer depends on two major factors:

1. Sensitivity of the drviers.
2. Design and size of the cabinet (smaller and/or sealed subwoofers need more power).

On some very small subwoofers such as the Sunfire True Subwoofers, the amplifiers are extremely powerful to compensate for the small size of the sealed cabinets. For example the amplifier's power output on the True Subwoofer EQ 12 Signature - TS-EQ12 is rated 2,700 Watts, RMS and the size of the cabinet is only 13.5" x 13.5" x 13.5". You cannot simply look at the power rating of this amplifier and conclude that this subwoofer is better than a comparable subwoofer from another manufacturer.

These are some other examples of subwoofers that are small sealed or with passive radiators that require very high output amplifiers.

http://www.definitivetech.com/Produc...s/default.aspx

Definitive Technology SuperCube® Reference:
List Price: $1,799
16-3/4” W x 16-3/4” D x 16-15/16” H
Amplifier Power :1800 watts

Definitive Technology SuperCube® I:
$1,199
14-1/4” W x 14-1/4” D x 14-1/10” H
Amplifier Power :1500 watts

Definitive Technology SuperCube® II:
List Price: $899
12” W x 12” D x 12-1/2” H
Amplifier Power :1250 watts

Definitive Technology SuperCube® III:
10-1/4” W x 10-1/4” D x 10-1/4” H
List Price: $699
Amplifier Power :650 watts


http://www.sunfire.com/products.asp

Sunfire True Subwoofer TS-EQ12:
13.5” W x 13.5” D x 13.5” H
Amplifier Power :2700 watts

Sunfire True Subwoofer TS-EQ10:
11.5” W x 11.5” D x 11.5” H
Amplifier Power :2700 watts

Sunfire True Subwoofer TS-SJ8:
9” W x 9” D x 9” H
Amplifier Power :1500 watts


Here is a good article from Harman International.

http://www.harmanaudio.com/all_about...werratings.asp

Most separate subwoofers, on the other hand, do incorporate their own amplifiers. When a speaker does include amplification, the manufacturer usually will give a power rating for that amplifier–which you should simply ignore. If power is so important a specification for separate amplifiers and receivers, why isn't it for a powered speaker or subwoofer? Actually, it is important, but only to the designer. He's the one who has to figure out what combination of speaker sensitivity and amplifier power will yield the desired sound output capability, which is what really matters. What you need to know is how loud the speaker or subwoofer can play over what frequency range and with how much distortion. In other words, you need to know what's coming out of the speaker, not what's going into it. It is entirely possible, for example, that a subwoofer with a 100-watt amplifier could outperform one with a 200-watt amp in every respect. For a consumer, the power rating of an amplifier built into a speaker is an absolutely useless number. In addition, there is the matter of the accuracy of such ratings. Because amplifiers built into speakers or subwoofers are inaccessible, it is rare that anybody checks how much power they can really deliver. Power numbers sell, which creates a temptation to–how shall we put this delicately–exaggerate that some companies find irresistable. Just one more reason to ignore them.

To help you understand this, let me give you the example of the horn-loaded speakers with full-range drivers that I built a while ago. Let's start by looking at the sensitivity of the drivers.

Fostex FE206E 8" Full Range Driver:

Frequency response: 39Hz to 20kHz
Sensitivity: 96dB
Impedance: 8 ohms

FostexFrequency.jpg

Fostex Fostex T90A Horn Super Tweeter:

Frequency response: 5kHz to 35kHz
Sensitivity: 106 dB

FostexHornTweeterFreqResponse.jpg

The sensitivities are way above average. This means that with only a few watts, you can make the speakers very loud.

Now, let's look at the cabinets. The cabinets are medium size horn-loaded. Horn-loaded cabinets are very efficient.

Folded Horn Design
Folded horn design enables the enclosure to contain a longer sound path which amplifies the bass frequencies while keeping the cabinet small in size. These horns, with the rear of the driver loaded by a bass horn, help a full range driver produce more bass with less work.

I use these speakers in my two-channel room with an old school two-channel preamp and a Carver two-channel amplifier rated at 375 watts RMS per channel. When I listen to these speakers, the preamp volume control is turned up about 10% and the sound is still extremely loud. If I were to make these speakers powered, I would add a single mono amp to each that is rated about 20 watts to a maximum of 50 watts. If you compare these speakers with another set of speakers that are made by other manufactures and have a standard bass reflex cabinet with sensitivity of 87dB, you would probably need about 200 watts to make them sound as loud and still have enough reserve power. Although the horn-loaded speakers may sound louder and better with 20-watt amplifiers than other speakers with 200 watt amplifiers, many people will automatically assume 200 watts must be better than 20 watts. Unfortunately, unethical manufacturers will promote the idea for marketing reasons.

I realize that the very powerful two-channel amplifier that I currently use is totally wasted. But I can brag that my amplifier is rated 375 watts per channel.

The moral of the story: Amplifier ratings for powered speakers/subwoofer have no meaning.

Here are some pictures for you.

[Istoc]

Thanks for the info BD. Always well layed out and accurately written . Interesting to read.

[Big Daddy]

Originally Posted by Istoc

Thanks for the info BD. Always well layed out and accurately written . Interesting to read.

Thanks Istoc. I spent a great deal of time doing the research and preparing these sticky threads.

[-DLS-]

Thanks for all the work - some great info Big Daddy! Since I recently got the new Hsu sub I have been hangin out more in the subwoofer forum and find your stickies very informative!

I have been looking at room EQ and reading about different equalizers - BFD, SMS-1 and the Antimode. I have been playing around with my sub(s) settings (phase, EQ, Q control, Ported, Unported) and took some measurements with my Scosche SPL1000 using the snapbug test tones link you provided in another thread. I used the REW Radioshack SPL meter correction worksheet and removed the corrections for my Scosche SPL meter. I am gonna try again using a Radioshack SPL meter(33-4050) later this week to see how different the measurements are from the two SPL meters.

So far this is what I've got. Can that peak at 18Hz do any damage to the subs when I listen at louder volumes. I have the sub level matched to 75db with the rest of the speakers. Here's a picture of my graph.




I can't really move my sub to any other location and have no room for bass traps. Do you have any other suggestions? Does it look that bad and is an EQ the only way to fix this. So far I like the way it sounds but if I can make it better then I will try but I just wanna know if $400-500 is worth it by looking at this picture. Thanks Big Daddy!!

[Big Daddy]

Originally Posted by -DLS-

Thanks for all the work - some great info Big Daddy! Since I recently got the new Hsu sub I have been hangin out more in the subwoofer forum and find your stickies very informative!

I have been looking at room EQ and reading about different equalizers - BFD, SMS-1 and the Antimode. I have been playing around with my sub(s) settings (phase, EQ, Q control, Ported, Unported) and took some measurements with my Scosche SPL1000 using the snapbug test tones link you provided in another thread. I used the REW Radioshack SPL meter correction worksheet and removed the corrections for my Scosche SPL meter. I am gonna try again using a Radioshack SPL meter(33-4050) later this week to see how different the measurements are from the two SPL meters.

So far this is what I've got. Can that peak at 18Hz do any damage to the subs when I listen at louder volumes. I have the sub level matched to 75db with the rest of the speakers. Here's a picture of my graph.




I can't really move my sub to any other location and have no room for bass traps. Do you have any other suggestions? Does it look that bad and is an EQ the only way to fix this. So far I like the way it sounds but if I can make it better then I will try but I just wanna know if $400-500 is worth it by looking at this picture. Thanks Big Daddy!!

Thanks for the compliments.

That peak at 18Hz is created by the room and not the driver. So it should not damage the driver. You have two options in dealing with that peak. The first option is to move the sub. Although you may get rid of the 18Hz peak, it may create another problem. The second option is to use an equalizer and lower the peak. One reason I prefer my Velodyne SMS-1 to BFD is the ease in which you can use it. Once you install it and connect all the wires, it is always hooked up and no additional setup is needed. You can see the graph on the TV screen and immediately lower the problem frequency.

[aces high]

Originally Posted by -DLS-

Thanks for all the work - some great info Big Daddy! Since I recently got the new Hsu sub I have been hangin out more in the subwoofer forum and find your stickies very informative!

I have been looking at room EQ and reading about different equalizers - BFD, SMS-1 and the Antimode. I have been playing around with my sub(s) settings (phase, EQ, Q control, Ported, Unported) and took some measurements with my Scosche SPL1000 using the snapbug test tones link you provided in another thread. I used the REW Radioshack SPL meter correction worksheet and removed the corrections for my Scosche SPL meter. I am gonna try again using a Radioshack SPL meter(33-4050) later this week to see how different the measurements are from the two SPL meters.

So far this is what I've got. Can that peak at 18Hz do any damage to the subs when I listen at louder volumes. I have the sub level matched to 75db with the rest of the speakers. Here's a picture of my graph.




I can't really move my sub to any other location and have no room for bass traps. Do you have any other suggestions? Does it look that bad and is an EQ the only way to fix this. So far I like the way it sounds but if I can make it better then I will try but I just wanna know if $400-500 is worth it by looking at this picture. Thanks Big Daddy!!

What is the crossover point your using, 80hz, 60hz?

[-DLS-]

Originally Posted by Big Daddy

Thanks for the compliments.

That peak at 18Hz is created by the room and not the driver. So it should not damage the driver. You have two options in dealing with that peak. The first option is to move the sub. Although you may get rid of the 18Hz peak, it may create another problem. The second option is to use an equalizer and lower the peak. One reason I prefer my Velodyne SMS-1 to BFD is the ease in which you can use it. Once you install it and connect all the wires, it is always hooked up and no additional setup is needed. You can see the graph on the TV screen and immediately lower the problem frequency.

Wow that was quick Thanks!! So other than that peak do you see a need for an equalizer. So far I'm not even sure how to tell how that peak affects my movie watching. Does that chart tell you anything else about my room? Just not sure if I wanna spend on an EQ yet. I 'm wondering by those measurements how much of a listening improvement I will get.

[-DLS-]

Originally Posted by aces high

What is the crossover point your using, 80hz, 60hz?

Using 80 right now.. would 60 make a difference?

[Big Daddy]

Originally Posted by -DLS-

Wow that was quick Thanks!! So other than that peak do you see a need for an equalizer. So far I'm not even sure how to tell how that peak affects my movie watching. Does that chart tell you anything else about my room? Just not sure if I wanna spend on an EQ yet. I 'm wondering by those measurements how much of a listening improvement I will get.

All subwoofers create standing waves and room modes in small home theater rooms. As a result, placement and equalization are absolute necessities.

If you don't want to worry about equalization, move to some open space in the Northwest Territories. Your subwoofer will have a great time as there will be no standing waves, but you will freeze to death.

[-DLS-]

Originally Posted by Big Daddy

All subwoofers create standing waves and room modes in small home theater rooms. As a result, placement and equalization are absolute necessities.

If you don't want to worry about equalization, move to some open space in the Northwest Territories. Your subwoofer will have a great time as there will be no standing waves, but you will freeze to death.

Eventually I will get an EQ. Just can't do it right now with Christmas and a Cruise vacation in 2 weeks..

Well.. I actually do live close enough to the NWT I'm already used to the cold it was -30 C here just last week!!

[aces high]

Originally Posted by -DLS-

Using 80 right now.. would 60 make a difference?

No 80 is good, I would look for an eq that will allow you to try and boost the valley that starts at 63hz. You may not be able to boost it all the way but I would try 3db. If your going to go to the trouble of getting an eq you might as well try to make it perfect. Big Daddy will be able to tell you if the SMS is right for the job better than I, I've never used one before. You have a lot of room gain down low which is not a bad thing, it's easier to cut peaks than boost valley's.

[-DLS-]

Originally Posted by aces high

No 80 is good, I would look for an eq that will allow you to try and boost the valley that starts at 63hz. You may not be able to boost it all the way but I would try 3db. If your going to go to the trouble of getting an eq you might as well try to make it perfect. Big Daddy will be able to tell you if the SMS is right for the job better than I, I've never used one before. You have a lot of room gain down low which is not a bad thing, it's easier to cut peaks than boost valley's.

I don't know maybe the peak at those levels is what I'm liking.. I'm really feeling it but not so bad that I ever have to reach for the remote. From what I've read so far there's not much you can do about dips and most EQ will only help bring down peaks to level level it out with everything else. I will play around with it more moving the sub in and out a few inches. I found adjusting the phase knob on the SVS affects levels much more but where some levels are brought down others are brought way up..

[lDlisturb3d]

I have a huge question that i need answering. I have my LPF for lfe set to 180 on my reciever as you stated but there's another selection on the back of my sub. 180-35hz. What am i suppose to set it too. I had it at 35 for a while but 180 seems to give me more overall base. I have towers and they are set to small. The regular crossover is set to 60hz.

[frogmort]

Originally Posted by lDlisturb3d

I have a huge question that i need answering. I have my LPF for lfe set to 180 on my reciever as you stated but there's another selection on the back of my sub. 180-35hz. What am i suppose to set it too. I had it at 35 for a while but 180 seems to give me more overall base. I have towers and they are set to small. The regular crossover is set to 60hz.

I am definitely no Big Daddy, but from what I've read, the low pass filter(LPF) for the low frequency effect(LFE) channel should always be set to 120hz in your AVR. Since your receiver is doing the crossovers and bass management, you do not want to redundantly use the built in crossover on your subwoofer, so it should be set to wide open (180hz in your case), so as not to interfere with the crossovers and bass management being done by your receiver.

Some subwoofers also have an LFE input that automatically bypasses the built in crossover in the sub. If yours has this, it would be the preferred way to hook it up. If not, just set the subwoofers crossover wide open to let the receiver handle it.

As far as the 120hz LPF on the LFE, I posted something about this last night, so I'll just slightly edit it and paste it in here for reference if you're interested:

Originally Posted by frogmort

From Chris Kyriakakis(inventor and CTO of Audyssey): "It's a filter that is applied to the content of the separate LFE track found in 5.1 content. That content is authored up to 120 Hz and so the only correct setting is 120 Hz."

https://audyssey.zendesk.com/entries/321931-lpf-on-lfe


From Big Daddy: "What is LFE (Low Frequency Effects)?
The LFE (.1) provides a dedicated channel for the low bass that is used in theaters to add impact to the movies. The LFE signal is band-limited to frequencies below 120 Hz.

The LFE channel is an independent channel and has no effect on the other speakers. The information that is in the LFE channel extends up to 120Hz regardless of whether you have bookshelf speakers or full-range super tower speakers. It is important to distinguish between the LFE channel and what goes to a subwoofer. The LFE is a production channel, whereas the subwoofer is a playback channel."

https://forum.blu-ray.com/showthread...ighlight=120hz

[lDlisturb3d]

Originally Posted by frogmort

I am definitely no Big Daddy, but from what I've read, the low pass filter(LPF) for the low frequency effect(LFE) channel should always be set to 120hz in your AVR. Since your receiver is doing the crossovers and bass management, you do not want to redundantly use the built in crossover on your subwoofer, so it should be set to wide open (180hz in your case), so as not to interfere with the crossovers and bass management being done by your receiver.

Some subwoofers also have an LFE input that automatically bypasses the built in crossover in the sub. If yours has this, it would be the preferred way to hook it up. If not, just set the subwoofers crossover wide open to let the receiver handle it.

As far as the 120hz LPF on the LFE, I posted something about this last night, so I'll just slightly edit it and paste it in here for reference if you're interested:

Thats what i thought. To be correct my sub can be set from 120 to 35hz. Im just gonna leave it at 120 because thats what my receiver is putting out.

[JOMV]

Hi to all!!!

First of all, I made all this post on my iphone, so please forgive me for any spelling mistake. Also, SORRY for the LOOONG post, but I try to be as much precise as I can so you can have a better understanding about my room!!!

As a side note, your sticky threads about surround speakers (PART 1 -https://forum.blu-ray.com/showthread.php?t=66471) & (PART 2 -https://forum.blu-ray.com/showthread.php?t=170720), helped me decide to go with bipole speakers in the corners. Case closed, thanks to you!!!

Now, I'm in the process of getting ready when the time comes to deal with the worst of all:...... Mr. subwoofer and its LFE!!!.... I have already read all your 3 sticky threads about bass:

A GUIDE TO SUBWOOFERS
PART 1:
https://forum.blu-ray.com/showthread.php?t=43669

A GUIDE TO SUBWOOFERS
PART 2:
https://forum.blu-ray.com/showthread.php?t=48286

A GUIDE TO BASS MANAGEMENT:
https://forum.blu-ray.com/subwoofers...anagement.html

I must say, those threads are a work of art!!!. But I still have questions as every room is different and I have some limitations. Ihope you remember me as we have talked about my room a couple of times this past week. I will add some pics to help you remember my setup.

Now, to my particular case:
My room is 10' wide x 11' long x 9' tall. I wanted to improve my room's performance, so I decided to make some changes to the original layout.

First of all, forgive all the crapy pics. I made those in Paint and took photos of them with my cel, so none of them look professional but they do serve the purpose.

At the beginning of my project, this is how I wanted it to look with 2 shelves towers:
This is the drawing I made:


This is how it looks in real life (I think I got it to look pretty close to what I drew the first time):



Now, after reading all your threads, I believe that those furniture towers make the bass to sound boomy because it is "caged" between those towers. Maybe giving the subwoofer more open space will help reduce that issue. Of course, it is just a theory I have.

So, in order to deal with that issue, and to improve the room's acoustics overall performance, I decided to replace the original furniture for two separate adjustable shelves like these ones:


Now, this is how it should look when I replace those furniture towers: (but with the acoustic foam layout shown on the 1st picture).


Even with that change, the subwoofer will still be under the center speaker and on the very middle of the front wall. I'm trying to figure out some other possible options if I have to move it. Another thing to point out is the couch location, which is against the back wall - (which I know is bad for LFE). I wouldn't want to move the couch closer to the screen, or at least not much if I can prevent it since it is only 9' from the screen. In any other case, another option would be to put the subwoofer on the back corners - this is where my limitations don't help. The door opens just under the left surround, so I can't move the subwoofer to that left corner. And I can't move couch to the left to put the subwoofer on the right corner because the door won't open. So, I guess I'm stuck to work on the front wall.

Remember this photo???


What I have on the left, are 2 mirror doors (closet doors). The front wall is going to be covered with acoustic foam to prevent reflection. I was also thinking about rising the sub a little, or putting a small carpet under its cabinet, and also separating it a couple of aditional inches from the wall........... Etc. Maybe you can give me some more pointers.

A little info about the subwoofer - (I know it is not the best sub, but at least is better than nothing until I can afford a better one)

- Old 12" Amplified MTX, (Model PSW 101B)
- 38hz - 150Hz.

Dimensions:
Wide - 18.75"
Height - 17.5"
Deep - 18.5"
Woofer - 12"

Front view:


Back view:


Complete view at the amp controls:


A closer look at the crossover amp controls:



I HAVE 5 QUESTIONS:

- ABOUT THE BUILT- IN CROSSOVER: (Please take a look to the crossover controls photo)
According to one of your threads, I should set the crossover on the sub all the way up to its maximum or at least 120Hz when doing the calibration with Audyssey MultiEQ XT on my Denon receiver. This sub lets you set it up to 150Hz.

1-A) Should I leave it at 120Hz or go up to 150Hz???

1-B) What about the gain??? - (was thinking half way)

1-C) What about the polarity, Normal or Reverse??? - I really don't know what they mean or do.

2) I expect to have more space on the front when I replace the furniture. That will allow me move the main speakers around 1 foot from the side walls which is good. Now that I know that LARGE & SMALL has nothing to do with speaker size, should I set them as SMALL on the receiver as stated on some of your threads?

3) I'm curious about buying a SPL but don't know how to use it and the real benefits of using one. I always thought that having a receiver with Audyssey MultiEQ XT was more than enough. Do you have a link to one of your super threads about how to use the SPL and its benefits??? Is it this one?
https://forum.blu-ray.com/showthread.php?t=38765


Thanks, to everyone and specially Big Daddy who has been kind enough since I joined this forum!!!

[Big Daddy]

Originally Posted by JOMV

I HAVE 5 QUESTIONS:

If you read A Guide to Bass Management (Part I) more carefullay, you will notice that all your questions are answered there. The following a section from that thread:

Subwoofer Setup and Crossover Settings:

1. You need a realtively long (12ft or longer) sub cable to experiment with the position of the sub in the room. Get a long RG6 subwoofer cable from Monoprice.com or any other source. RG6 cables with RCA connectors at both ends have good shielding and work better than regular RCA cables.
2. You may also need a Y adapter (2 male, 1 female).
3. Connect one end of the sub cable to LFE out (sub out or sub pre-out) on the back of the receiver.
4. Connect the other end of the sub cable to the Left channel input (on some subs, the Right channel can also work) of the subwoofer. If you use a Y adapter (2 male, 1 female) and connect the subwoofer cable to both the Left and Right inputs on the back of the sub, you may get between 3db to 6db more output from the subwoofer. Refer to the footnote.
5. Turn the sub to on and set it to Auto.
6. On the back of the sub, turn the crossover all the way up to the maximum level or turn it off. You set the crossovers in the receiver's menu.
7. On the back of the sub, turn the level (gain) to 50%-65%. You can adjust that a little later during calibration. However, it is a good idea not to exceed the 3/4 (75%) point.
8. In the receiver's menu, make sure the subwoofer is turned to ON.
9. In the receiver's menu, set all the speakers to SMALL.
10. In the receiver's menu, set the high pass filter (HPF) crossover frequencies of all your speakers to at least 10Hz or 15Hz above the minimum frequency extension of the speakers. If you can't find the frequency response of your speakers, consult the table at the beginning of this thread.
11. In the receiver's menu, set the low pass filter (LPF) of the subwoofer to 120Hz.
12. If your receiver does not allow you to set the crossovers of the individual speakers, set the (HPF/LPF) crossover to somewhere between 80Hz to 120Hz according to the low frequency extension of your speakers. If you can't find your speakers frequency response, consult the table at the beginning of this thread.
13. In the receiver's menu, set the subwoofer to LFE and not LFE+Main or Double Bass..
14. Run the calibration program. The Audyssey calibration program works best if you run it for multiple listening positions.
15. If the calibration program changes the above settings, you can change them manually to above values. In general, increasing the crossover is ok. If you lower the crossover below the level that Audyssey calibration has set, Auddyssey will not apply its filters to those lower frequencies below the crossover point.

Note: The phase control on the back the subwoofers is a usually a simplistic analog control that only changes the phase at one frequency. Proper phase alignment requires that the phase change is different at every frequency. Unfortunately, that is not possible with an analog control. As a result, Audyssey recommends that you leave the phase control at zero.

My answers to your questions are in red.

1-A) Should I leave it at 120Hz or go up to 150Hz???

Turn the crossover all the way up to 150Hz.

1-B) What about the gain??? - (was thinking half way)

Initially, turn the level of the subwoofer on its back to around 60%. Run Audyssey for multiple positions. If Audyssey sets the subwoofer's gain in the receiver's menu to a large negative number like -10dB, go back and turn the level on the back of the subwoofer to 40% and repeat. If Audyssey sets the subwoofer's gain in the receiver's menu to a large positive number like +12dB, go back and increase the level of the subwoofer on its back or move it to a better position in the room. You should not increase this level higher than 75%. If your bass is still not adequate, you need to find a better position for your subwoofer and also think about adding a second one.

1-C) What about the polarity, Normal or Reverse??? - I really don't know what they mean or do.

Read the quote at the beginnig of this post from A Guide to Bass Management (Part I). Also, I have a section on this topic in A Guide to Subwoofers (Part I). Finally, go back and read post #1 of this thread. I have section there on phase and polarity.

The short answer to your question is to set the phase to Zero or Normal.

2) I expect to have more space on the front when I replace the furniture. That will allow me move the main speakers around 1 foot from the side walls which is good. Now that I know that LARGE & SMALL has nothing to do with speaker size, should I set them as SMALL on the receiver as stated on some of your threads?

If you have a subwoofer in the room, all your speakers become small by default. Set them all to SMALL and let the subwoofer handle the lower frequencies.

3) I'm curious about buying a SPL but don't know how to use it and the real benefits of using one. I always thought that having a receiver with Audyssey MultiEQ XT was more than enough. Do you have a link to one of your super threads about how to use the SPL and its benefits??? Is it this one?
https://forum.blu-ray.com/showthread.php?t=38765

Yes, you found the correct thread on SPL meters.

Finally, there is nothing wrong with puting the subwoofer in the back of the room. Generally speaking, a subwoofer will sound louder in the corner of the room as opposed to the middle of the wall. If you put the subwoofer in the corner, make sure it is a foot or so away from the side walls. Also, puting a subwoofer on a riser may help.

If you decide to have two subwoofers, go to Post #2 of A Guide to Subwoofers (Part II): Standing Waves and Room Modes. There are diagrams there that will hep you with positioning of two subwoofers.

[BillyMM]

Good Day.

I have some questions about the setup of my subwoofer (a Polk PSW505) with my AVR (an Onkyo TX-SR508):

My AVR only has one Crossover selection option - no other fine tuning is available for what is sent to the sub... So, should I set the Crossover to 120 in order to get the full LFE as well as the bass from the other speakers? Or does the AVR automatically 'know' to send the full LFE signal, so I can therefore drop my Crossover setting down to 80?

Also, when using the Audyssey 2EQ program, my Onkyo continues to drop my sub down to a -15db setting no matter where I place it or how low I drop the volume on the sub (currently down to about 30% volume)... So, how low is TOO low for the volume level on the sub? Or does it not matter? Should I drop the volume all the way down to say 10%, or will I be losing too much of the subs 'power' or functioning? Along those same lines - will I be messing up the Audyssey functions if I just go ahead and up the sub setting in the AVR to say -5db?

Thank you very much in advance for any assistance!

[Big Daddy]

Originally Posted by BillyMM

Good Day.

I have some questions about the setup of my subwoofer (a Polk PSW505) with my AVR (an Onkyo TX-SR508):

My AVR only has one Crossover selection option - no other fine tuning is available for what is sent to the sub... So, should I set the Crossover to 120 in order to get the full LFE as well as the bass from the other speakers? Or does the AVR automatically 'know' to send the full LFE signal, so I can therefore drop my Crossover setting down to 80?

Also, when using the Audyssey 2EQ program, my Onkyo continues to drop my sub down to a -15db setting no matter where I place it or how low I drop the volume on the sub (currently down to about 30% volume)... So, how low is TOO low for the volume level on the sub? Or does it not matter? Should I drop the volume all the way down to say 10%, or will I be losing too much of the subs 'power' or functioning? Along those same lines - will I be messing up the Audyssey functions if I just go ahead and up the sub setting in the AVR to say -5db?

Thank you very much in advance for any assistance!

Turn the crossover on the back of the subwoofer to 120Hz.

Something is strange about your receiver. Do you hear the subwoofer at all? Does the subwoofer's driver move when you touch it?

You are probably better off purchasing an SPL meter from Radio Shack and checking the levels of the speakers and the subwoofer.

It may not be a bad idea to save money and replace your receiver. Make sure you buy a receiver that allows for different crossover settings and has a better Audyssey than 2EQ. Onkyo and Denon have many options. Sell the old receiver on Ebay.