A Guide to Bass Management (Part I)

[Big Daddy]

It is highly recommended that you also read the following threads:

• A Guide to Bass Management (Part II).
• Calibrating Your Audio With an SPL Meter.
• A Guide to Crossover Networks.
• Using Test Tones to Calibrate Speakers/Subwoofers.
• A Guide to Subwoofers.
• A Guide to Subwoofers (Part II).

A GUIDE TO BASS MANAGEMENT (PART I)

Prepared by Big Daddy

Why Do I need A Subwoofer?
Building full-range speakers is expensive and difficult. Re-creating low frequencies cleanly and effectively requires large drivers, large enclosures, and a great deal of power. That is the reason why low frequency duties are directed to a subwoofer. This enables manufacturers to build speakers more easily and economically.

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 goal of the LFE channel is to store very loud low frequency effects, which would not fit inside the dynamic range of the other speakers. That is why LFE is recorded -10dB lower in the relations to the other 5 or 7 channels to leave enough headroom to help follow the equal loudness contours. This means that it takes more energy in the low bass to sound equally as loud as the midrange. LFE is boosted by +10dB in playback to compensate for this.

When the player is connected to the receiver/processors digitally through the HDMI, Optical, or Digital Coaxial cables, the +10dB is added automatically. When the connection is through analog cables, we may have to add this +10dB boost manually.

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. The sound engineers determine what goes to the LFE channel, and the users of the home-theater systems determine what ends up coming out of the subwoofer.

What Are Low Pass and High Pass Filters?
Low-Pass Filter: A low-pass filter blocks (attenuates) high frequency signals above the cutoff frequency and passes low-frequency signals. It is sometimes called a high-cut filter, or treble cut filter. Low-pass filters are generally used on subwoofers to block high frequency signals that they cannot reproduce. The low pass filters in most high quality receivers have a 24 dB / octave slope.

High-Pass Filter: A high-pass filter blocks (attenuates) the low frequency signals below the cutoff frequency, but passes high frequency signals. It is sometimes called a low-cut filter. The high pass filter in most modern receivers have a 12 dB / octave slope.

Small and Large Speakers
In the bass management setup menu, setting speakers to "Small" and "Large" does not refer to the physical size of your speakers. It refers to the low frequency extension of your speakers or whether your speakers are capable of reproducing powerful deep bass below 80 Hz.

You should consult the manual of your speakers or the Website of the manufacturer to get information about the frequency response of your speakers. The following table is an approximation guideline as suggested by OutLaw Audio.

What is Bass Management?
Bass management takes the low frequency signals from the satellites, bookshelf speakers, or bass-limited directional speakers, and combines them with the LFE signal to be played through the subwoofer.

There are several types of Bass Management systems within the AV receivers or processors:

Fixed: These systems merely ask you whether your speakers are Large or Small and do not offer the option to change the crossover frequency. Generally, the crossover frequency on most of these systems is set somewhere between 80Hz-120Hz and cannot be changed.

Variable Crossover: These systems allow you to set your speakers to Large or Small, but also allow you to change one crossover frequency that applies to all speakers and the subwoofer(s). Setting the crossover frequency between 80Hz-100Hz can work for most people.

Variable Crossovers for all Speakers: The most modern AVR's and processors allow you to set different crossover frequencies for the front, center, side surround, and rear surround speakers. In addition, they allow you to set a low pass filter (LPF) for the LFE (.1) channel. Although these systems are more flexible and complex, they are not necessarily better and need some degree of expertise to be set properly.

Normally you set the LPF of LFE to 120Hz to make sure you receive all the information that the audio engineers put in the LFE channel. At the same time, you want to make sure that frequencies above 120Hz will not go to your subwoofer as it is possible that some discs, particularly older DVDs, may have a full-range LFE channel due to poor and careless engineering.

As far as the LFE boost is concerned, bass management complicates matters slightly. The player still sends the LFE signal with a -10dB reduction. The receiver/processors reduces the LFE signal another -5dB. It also reduces the redirected bass from the other speakers -15dB, mixes the two signals together, and then adds another +15dB boost to the signal before sending it to the subwoofer. With analog connection, we may have to do this +15dB boost manually. More information on analog LFE boost can be found HERE.

Double Bass or LFE+Main:
Manufacturers have different names for this option.

Double Bass On (Onkyo) = LFE + Main (Denon) = Both (Yamaha)

When you use these options, Bass management becomes enabled for Large (Full Band) speakers. The frequency below which the signals from the main 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. Onkyo and Denon use Audyssey and this information is verified by Audyssey.

Double Bass or LFE+Main is an option that was created by AVR makers as a compromise to customers who were personally “offended” when their speakers were designated Small in the AVR's menu. In such modes, the mains run full-range AND the subwoofer is lowpassed at a specified frequency. So both the main speakers and the subwoofer are receiving bass signals. The problem is that in the overlap frequency region between the sub and the front speakers, the bass frequencies are doubled and tend to become bloated and boomy.

One of the most important factors in receiving good bass sound in a small HT room is placement of the low frequency sources. Although the subwoofer can be moved around the room in order to find the optimum position, the front speakers cannot be moved to other spots in the room. In addition, when the bass frequencies are directed to both the front speakers and the subwoofer, there may be some phase cancellation problem for some of these frequencies.

Using a separate subwoofer and sending all bass frequencies to it is beneficial. The proper way of distributing the bass sound across the room correctly is with more than one subwoofer. An even number of subwoofers, 2 or 4, is preferred.

Bass Management in Multi-Channel Systems
In a modern 5.1 system, the signals from the five speakers are sent through a high pass filter so that only frequencies above the cutoff frequency are sent to the corresponding speakers. At the same time, a lowpass filter redirects frequencies below the cutoff frequency from each channel to the subwoofer. Meanwhile, the LFE passes through its own built-in lowpass filter (this frequency does not depend on the low pass frequency between the main loudspeakers and the subwoofer) and are passed to the subwoofer. The low frequencies of all other channels are summed together with the LFE channel and sent to the subwoofer. Different receivers perform bass management differently. The following diagrams demonstrate different options for Bass Management when speakers are set to "Large" or "Small". Although many new AVR's follow the bass management depicted in the first diagram, it is important to be aware of the other alternatives.

Diagram Created by Big Daddy



Diagram Created by Big Daddy



Diagram Created by Big Daddy



Diagram Created by Big Daddy



Diagram Created by Big Daddy

Should I Set My Speakers to Large or Small?
People always ask this question. The answer is very simple. If you own a subwoofer that outputs good bass sound, you should set all your speakers to SMALL. In general, if you own a subwoofer, it may be wise to set all your speakers to small for several reasons:

1. When there is an overlap of bass sound from the front speakers and the subwoofer, you will get bloated and boomy bass.
2. A subwoofer can play low frequencies all the way down to 20Hz or lower. Even relatively large front speakers cannot go that low.
3. The placement of a sub in a room is the primary factor in receiving good bass sound. You cannot adjust the position of the front speakers and move them to the side or back.
4. If the subwoofer and the front speakers play the same bass frequencies, there will be a possibility of phase cancellation of certain bass frequencies.
5. Redirecting the bass to the subwoofer relieves the receiver/amplifier from having to work on reproducing the low frequencies and this greatly improves the headroom.
6. If you are using the Audyssey MultEQ calibration, you will get much better bass performance because the MultEQ subwoofer filters have 8x higher resolution than the filters for the other speakers.

People have a psycological 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. My Definitive Technology front speakers have 15" built-in subwoofers with built-in 300 watt amplifiers. In addition to those, I have six external subwoofers in my HT room. When I set the front speakers to SMALL, the quality of the sound (both music and movies) improves.

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

LARGE = The speakers are not Bass Managed.
SMALL = The speakers are Bass Managed.

Read these blogs from Audyssey: Small vs Large and Subwoofer Setup & MultEq.

SPEAKER AND SUBWOOFER SETUP

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.

After calibration, the actual dB settings are totally meaningless. Each room is different. The same speakers may sound completely different in another room and may require different dB settings. For example, you may have two identical front speakers and set their levels equally. However, it is possible for one of the speakers to sound louder. This is because the location of each speaker with respect to the boundaries is not the same and they interact with boundaries differently.

The most important thing about calibration is that you want the level of all speakers to be the same at your primary listening position. The actual positive or negative dB levels are not that important.

Subwoofers are the problem children. The low bass frequencies have very long wavelengths that are sometimes several times the dimensions of the room. These frequencies interact with the boundaries (walls, ceiling, floor) and create standing waves. Because of this, you need to move your subwoofer around to get better performance for your primary listening position. Each time you move your subwoofer, you need to re-calibrate the speakers again. Don't be surprised if your dB levels, particularly for the subwoofer, change drastically.

After calibration, if the level of the subwoofer is set to +12dB, it usually means that your subwoofer is not in a good location or the level on the back of the sub is set too low. Move the sub around and experiment. If the subwoofer's port is in the back, make sure it has enough breathing room and keep it away from the walls. If you decide to increase the gain on the back of the sub, do not go beyond 75%.

Standard Low Pass Cutoff Frequency
An extensive survey conducted in Europe showed that 80Hz is the best choice for receivers with fixed-frequency filters. The mean frequency that the vast majority of humans began to distinguish subwoofer directionality was 185 Hz, and 80 Hz was the minimum frequency below which no one heard directionality.

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 response 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.

Avoid an Audio Hole
A low-pass crossover frequency will block high frequency sound above the cutoff level. A high-pass crossover frequency will block frequencies below the cutoff level.

Typically, on many new recievers, the LPF ONLY affects the LFE channel (the ".1" channel), not the bass redirected from the other 5 or 7 channels. That is why you normally set it to 120Hz to make sure you receive all the information that the producers intended to put in the LFE channel. However, if the implemented LPF in the receiver affects the redirected bass from the other SMALL speakers, do not adjust the low-pass frequency too far below the high-pass frequency. You could end up with an audio hole in between the low-pass and high-pass frequencies.

It is important to remember that crossover networks cut frequencies progressively. As a result, if, for example, the high-pass frequency for the small speakers is set at 100Hz, and you set the low pass frequency around 80Hz or 90Hz, you will most likely be ok. If, however, you set the low-pass frequency around 60Hz to 70Hz, then you would most likely end up with an audio hole. Can you really hear the difference? I will leave the decision up to you.

Subwoofer Placement
Subwoofer placement in the room is by far the most important factor in the performance of the sub. Wear a tight belt, buy a long sub cable, and experiment to get the best location for your subwoofer. Most people start with the corner of their room. Subwoofers tend to use the corner walls and increase their output in the room. If you are going to put it in a corner, move a foot or so away from the walls so that the subwoofer does not become too boomy. The other option is to use the Subwoofer Crawl technique. Move the subwoofer to the position you normally sit. Play test tones or music with heavy bass. Walk (crawl) around the room slowly, preferably with an SPL meter, and listen or measure the bass sound. The location with the best bass performance is the perfect location for your sub. Mark it and move your sub there. Generally you hear louder bass sound closer to the walls. The worst place is in the middle of the room.

The following video by Axiom Audio demonstrates the subwoofer crawl technique.

USING MULTIPLE SUBWOOFERS

The low frequency sound waves interact with the room boundaries (walls, celing, and floor) and create standing waves and room modes. The effect of these standing waves is that the bass sound in the room will be very uneven and depending on the sub's position and your listening position, you will get very hot and cold spots. An easy solution to this problem is to use multiple subwoofers.

Extensive research has been performed on subwoofers at the National Research Council of Canada and at Harman International. These are some of the conclusions:

1. The placement of a subwoofer is the most important factor in determining the level of bass output in a home theater room.
2. Multiple subwoofers will always perform better than one. Although you can get more bass output with multiple subwoofers, the real reason you should use multiple subwoofers is to smooth out the bass response across the room for all positions.
3. An even number of subwoofers is the best choice.
4. Studies also showed that the optimum number is 4 subwoofers. Increasing the number of subwoofers to more than 4 will not give you any additional benefit.
5. The use of identical subwoofers is the easiest choice for setup and calibration. This does not mean that you cannot use different subwoofers. It simply means that it may take longer to adjust the levels of two different subwoofers.
6. Placement of two or four subwoofers is even more important than placement of one subwoofer.

Connecting and Setting Up Two Subwoofers:

1. To add a second subwoofer, buy a Y adapter (1 male, 2 female) and two sub cables. Insert the male side of the Y adapter into the LFE out (sub out or sub pre-out) on the back of the receiver. Attach the two sub cables to the female sides of the Y adapter and connect each cable to the back of each subwoofer.
2. With two subs, you will have to experiment to get good bass sound. The end result will be better than one subwoofer as you can create more uniform bass across the room for all listening positions.
3. Remember that our ears are not as sensitive to very low frequency sound. As a result, deeper and lower frequency bass sound does not sound as loud as upper frequency bass sound. A subwoofer that does not go as low may sound louder, but it lacks the low frequency extension. It is possible that you are used to that from your previous subwoofer and your brain needs some time to adjust.
4. If you are planning to use two subwoofers, you must carefully match their levels at your primary listening position. You may have to turn one off and adjust the other one until you get it right.
5. Also when you run two subs, there is possibility of phase cancellation. You need to experiment with their position and phase.
6. Once all the placements are finalized, don't forget to re-calibrate your speakers again as different subwoofers and different placements will interact differently with the room boundaries.

Placement of two Subwoofers:
You need to place the two subs properly for the best bass performance. You can try three options:

1. Put one in the middle of the right wall and one in the middle of the left wall.
2. Put one in the middle of the front wall and one in the middle of the rear wall.
3. Put one sub in the front right corner and the other sub in the front left corner.
4. Put one in the front corner and the other in the corner in the the rear of the room.
5. If you have two different subs, put the larger sub with better lower frequency extension in the front corner and put the smaller sub close to your listening area. The sub up front will provide you with deeper and lower frequency bass and sub near you will provide you with upper frequency bass sound.

In all cases, move the subs at least a foot away from the walls and adjust their levels so that one does not overpower the other.


Adjustment of Two Subwoofers

1. On the back of the subs, turn their levels to 50%-60%, no higher than 75%.
2. On the back of the subs, turn their crossovers all the way up to their maximum point. You set the crossover in the receiver.
3. In the receiver's menu, set all speakers to SMALL.
4. In the receiver's menu, set the crossovers of all the speakers to 80Hz. You can deviate from 80Hz depending on the low frequency extension of your speakers. Make sure the crossover is always set at least 10Hz-15Hz higher than the minimum frequency response (+-3dB) of your speakers.
5. In the receiver's menu, set the crossover frequency of the LFE channel to 120Hz.
6. In the receiver's menu, set the level of the subwoofers to zero.
7. Turn off one subwoofer.
8. Play the test tones through the subwoofer that is on and measure its response with an SPL meter. Adjust its level on its back (not the receiver) so that you get approximately 73dB.
9. Turn on the other subwoofer and turn off the previous subwoofer.
10. Run test tones through it and adjust the level on its back so that you get approximately 73dB.
11. Now, turn on both subwoofers and do not touch the levels on their back.
12. After you adjust the level of each subwoofer independetly, it is a good idea to run the calibration program inside the receiver. In addition to checking the level of the combined output of both subwoofers, the receiver will also equalize them. Alternatively, you can use an external parametric equalizer.
13. Double check the settings with your SPL meter. Run the test tones again and adjust the levels of all the speakers. Make sure the SPL meter is held steady at a 45 degree angle at the primary listening position. Don't stand directly behind the SPL meter. Stand on the side. It is best for the SPL meter to be on a tripod.
14. When the time comes to adjust the subwoofers, move the SPL meter slightly to the right and slightly to the left and average the dB level that it registers.

Hopefully this will work. If you move the subwoofers or move your listening position, don't be surprised if the level of the subwoofers change drastically.

FOOTNOTE

Using a Y adapter on most, but not all, subwoofers will increase the sound level from 3 to 6 db.

Aperion Audio Subwoofer Y Cable
"Why, oh why do you need a subwoofer Y cable? Most AV receivers come with a single sub output while most powered subwoofers come equipped with left & right inputs. By using a subwoofer Y cable for both the left and right subwoofer input, you can increase the bass output of your subwoofer by about 3dB."

HDMI cable for home theater and high-performace audio video cables.
"Attach this cable to an existing subwoofer cable to split the signal into two inputs.
Instantly improves your home theater or home audio experience.
Many subwoofers have increased clarity and bass response when both inputs are fed with a mono signal."

Wye Y Cable
"Typically, powered subwoofers will come equipped with either a single RCA connector, or double RCA connectors. However, both connections typically only require a mono (single) connection. Therefore, if you have both right and left inputs, a single cable connected to the "left" input will probably work just fine. However, you can get anywhere from a 3dB to 10 dB gain from your subwoofer by plugging into both stereo inputs. To plug into both inputs with a single cable, simply purchase our Y adapter Cable along with your subwoofer cable."

This is the science behind it:

There are two formulas used to find the db ratio between sound levels.

The first is used ONLY FOR POWER (watts): 10 . log (P2/P1). This formula is used when comparing Sound Intensity, measured in watts.

The second is used ONLY FOR VOLTAGES (and SPL levels): 20 . log (V2/V1). This formula is for voltage relationships and Sound Pressure Levels.

Using a Y adapter will add two correlated signals. When you sum two equal correlated audio signals (i.e., mono sources from sub output on the receiver/preamp), you will get twice the signal level (A1 + A2 = 2A1, since A1=A2).

Therefore , since V2 = 2 V1 and the log (2) = 0.30103, it follows

20 . log (2V1/V1) = 20 . log (2) = 6dB gain in voltage.

For power, it will be

10. log (2P1/P1) = 10 . log (2) = 3dB increase in power.

These are a few advantages (some real and some claimed) to using a Y adapter:

• If you leave one of the RCA inputs open, dirt may get in there.
• Using a Y adapter may add a few dbs to the subwoofers's output.
• Some claim that the subwoofer works better at lower levels with the Y-cable.
• The auto-off mode of some older subwoofers (e.g, Velodyne CH-12) may not come on at lower levels without the use of a Y-cable.
• Some older subwoofers may actually need a Y cable because the left channel L may not default to mono signal.
• Another benefit of using a Y-cable at the sub input jacks may be for reducing the amount of Radio Frequency (RF) and Electomagnetic (EM) interference, because you are not leaving the other input open and active. Subwoofers can be affected by annoying buzzes and hums.

Conclusion: Since Y adapters cost a few dollars and there is no significant risk involved, I would recommend using a Y adapter (2 male, 1 female) at the subwoofer's RCA input jacks. Make sure you use a good quality Y adapter that is shielded. Otherwise, you may hear hum and noises.

ADDITONAL INFORMATION AND REFERENCES

Check post #2 of this thread.

[Big Daddy]

CABLE REQUIREMENTS FOR DIFFERENT CODECS

The HDMI classifications refer to the transmitter and receiver chips in the players and receivers/processors. They do not refer to HDMI cables.

As far as cables are concerned, they are tested as Standard (Category 1) or High Speed (Category 2). Just because a cable is not tested, it does not mean that it cannot perform as a high speed cable. You do not need to spend a lot of money to get good HDMI cables. There are plenty of inexpensive HDMI cables that can perform perfectly. All HDMI cables from Monoprice are high speed (Category 2) cables.

This information is from HDMI.org:

Q. What is the difference between a “Standard” HDMI cable and a “High-Speed” HDMI cable?

A. Recently, HDMI Licensing, LLC announced that cables would be tested as Standard or High-Speed cables.

• Standard (or “category 1”) HDMI cables have been tested to perform at speeds of 75Mhz or up to 2.25Gbps, which is the equivalent of a 720p/1080i signal.
• High Speed (or “category 2”) HDMI cables have been tested to perform at speeds of 340Mhz or up to 10.2Gbps, which is the highest bandwidth currently available over an HDMI cable and can successfully handle 1080p signals including those at increased color depths and/or increased refresh rates from the Source. High-Speed cables are also able to accommodate higher resolution displays, such as WQXGA cinema monitors (resolution of 2560 x 1600).

1. Any version of HDMI can transmit and receive LPCM signals. Also, note that the information on DVD-A discs is encoded in PCM.
2. You need HDMI 1.2 or above to output SACD in its native DSD format.
3. You need HDMI 1.3 or above to bitstream HD audio (Dolby TrueHD, DD+, DTS-HD HR, and DTS-HD MA) from the player to the receiver/processor.
4. The HDMI 1.4 standard is for 3D and has optional features for both TV and source component makers, including an audio return function and Ethernet connectivity. The Ethernet feature allows an Ethernet signal to be carried to other components via HDMI. HDMI Ethernet functionality is only available if both the player and the receiver/processor are HDMI Ethernet-enabled. Ethernet is the only HDMI 1.4 function that requires buying a new cable. If you do not care for Ethernet connectivity, any Category 2 HDMI cable should work fine for passing 3D signals.

Dolby Digital, DTS Digital, and All Variants
HDMI, Toslink (Optical), Coaxial S/PDIF (Sony/Philips Digital Interconnect Format), and Multi-Channel Analog Cables.

Dolby Digital Plus (+), DTS HD HR, LPCM, Dolby TrueHD, And DTS HD MA
HDMI and Multi-Channel Analog Cables. If the player decodes the signal to PCM, any version of HDMI (transmitter and receiver) can work. If the player transmits the signal in bitstream, HDMI 1.3 connection at both ends (player and receiver/processor) will be needed. Optical and coaxial cables can transmit two-channel stereo LPCM signal.

DVD-A
HDMI (version 1.1 or above), Multi-Channel Analog Cables, I-Link (IEEE 1394, Firewire), and proprietory connections such as Denon Link.

SACD
HDMI (version 1.2 or above), Multi-Channel Analog Cables, I-Link (IEEE 1394, Firewire), and proprietory connections such as Denon Link.

Bass Management When Analog Cables Are Used
When a disc player is connected to a receiver with multi-channel analog cables, the player must perform digital to analog decoding and send the analog signals to the receiver. In this case, calibration and bass management adjustments such as speaker sizes and channel levels should be done in the player's setup menus or the receiver must have bass management for the 5.1, 6.1, or 7.1 ANALOG inputs. If the player lacks calibration adjustments or the receiver cannot perform adjustments for analog inputs, bass management cannot be performed.

CONNECTING TWO SUBWOOFERS TO A RECEIVER/PROCESSOR

Using a Y adapter and connecting two subwoofers to a single subwoofer (LFE) output on the back of a receiver/processor may be preferred to daisy chaining the two subwoofers. These are my reasons:

1. If one subwoofer passes the signal to a second subwoofer, you may have difficulty with setting the distance and having the processor compensate for it. The second subwoofer would be milliseconds after the first depending on the relative distance of the lsitener. This can definitely be an issue, especially if the distance between the two subwoofers is very far from each other.
   
2. Although this issue can partially be solved if you have variable phase control on the two subwoofers, adjusting the phase of 2 subwoofers in two different locations and at two different distances is not something that is an easy thing to accomplish, particularly for a novice.
   
3. According to Chris Kyriakakis, CTO of Audyssey, 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.
   
4. Moreover, the subwoofer distance setting often needs to be adjusted to a setting that is different form the subwoofer's actual measured distance.
   
5. There may be some concern that you may lose some signal when you connect two or more subwoofers to a receiver/preamp. First of all, the line-level input impedance of most subwoofers is high enough that connecting two or more in parallel will not cause any problems with signal level. Secondly, any loss due to a Y splitter or cable will be mostly in the higher frequencies. Moreover, subwoofers have variable level control that can be adjusted and in order to compensate for any cable loss. As long the level of your speakers and your subwoofers are set to 75dB, you are set. In most cases, dealing with losses due to room modes is a much bigger problem than any insignificant cable loss.
   
6. Another very important issue is that two subwoofers can increase the output anywhere from 3 to 6dB, depending upon whether they are co-located or not. If two subwoofers are collocated (e.g., stacked in a corner), their combined output can increase by ~ 6dB's. If they are placed in different locations, the combined output would increase by ~ 3dB's or more. In most cases, placing two subwoofers in two different locations (e.g., the middle of two sides against the wall) will deal with room modes more effectively and will give you a more even bass across the room for all listening positions.
   
7. The line level outputs on many subwoofers have a fixed high pass filter (usually 12 dB/octave and at at 80, 90, 100, or 120Hz) that cannot be defeated. That is another reason why subwoofers should never be daisy-chained unless the high pass can be defeated.
   
8. On subwoofers that have two inputs (typically the left and right inputs), you can use a Y splitter (two male, one female) and connect the subwoofer cable coming out of the back of the processor to both inputs on the back of the subwoofer. This will increase the output level by 3 to 6dB's.
   
9. A subwoofer in the corner will use all room modes and will have significantly much more output. The best part is that it is for free and does not cost anything.
   
10. In case of a problem with the first subwoofer's amplifier (a very common problem) in the chain, the second subwoofer will also become affected.
    
11. To summarize, the first subwoofer in the chain may send dirtier output to the second sub than it would receive if you simply use a Y-adapter and send independent signals to each one. Using a Y adapter accomplishes the exact same thing as daisy-chaining, but it avoids any potential pitfalls or problems that the first subwoofer may impart on the signal.

Cable loss is more of an issue with video as opposed to audio. For additional information, you can read the following thread:

https://forum.blu-ray.com/home-theat...gnal-loss.html

CABLES NEEDED TO CONNECT ONE OR TWO SUBWOOFERS TO A RECEIVER

Subwoofer Cables
The placement of a subwoofer in the room is perhaps the most important factor in determining the quality and level of bass in a home theater room. Because you need to experiment with the position of the subwoofer in the room, you should buy a relatively long calble (12 ft or higher).

http://www.monoprice.com/products/su...02&cp_id=10236
http://www.bluejeanscable.com/store/subwoofer/index.htm
http://store.audioholics.com/section...bwoofer-cables
http://www.amazon.com/s?url=search-a...ubwoofer+cable

Y Adapters
You can buy the solid type Y adapter or the cable Y adapter.

Y Adapter (2 male, 1 female): This Y adapter is used to connect the sub cable from the back of the receiver to both the Right and Left inputs on the back of the subwoofer. On many subs, this will give a few additional dB's of sound output.

http://www.monoprice.com/products/pr...seq=1&format=2

http://www.cablesimple.com/index.php...oducts_id=4529


Higher quality Y adapter (2 Male, 1 Female) from Monoprice: $2.90 + Shipping:

http://www.monoprice.com/products/pr...seq=1&format=2


Higher Quality Y Adapter (2 Male, 1 Female) from Radio Shack, $3.59 + Free Shipping:

http://www.radioshack.com/product/in...ductId=3232744


Higher Quality Y Adapters (2 Male, 1 Female) from Pro Satellite Supply, $3.99 + Shipping:

Mediabridge Y Adapter from Amazon (2 Male, 1 Female), $5.99 from Amazon, Qualifies for free shipping for orders over $25:

Mediabridge_Adapter.jpg

http://www.amazon.com/Mediabridge-Ul...851189&sr=1-41


Higher quality Y adapter (2 Male, 1 Female):

http://store.audioholics.com/product...dapter-y-cable, $6.03 + Free Shipping
http://www.cablesimple.com/index.php...oducts_id=5001, $4.48 + Shipping
http://store.cablesplususa.com/2214-29122-001.html, $4.71 + Shipping (maybe lower shipping cost)


High-End Y Adapter (2 Male, 1 Female) from Radio Shack, $11.29 + Free Shipping:

http://www.radioshack.com/product/in...ductId=2102978


High-End (Silver-plated twisted-pair copper conductors with 2 layers of copper shielding and 1 layer of foil shielding):

http://www.parts-express.com/pe/show...number=184-226, $12.32 + Shipping
http://store.audioholics.com/product...a-male-y-cable, $16.99 + Free Shipping:


Y Adapter (1 male, 2 female): This Y adapter is used for connecting two subwoofers to the receiver. You insert the male side to the LFE out (sub out or sub pre-out) on the back of the receiver and connect two sub cables to the female sides (one for each sub).

http://www.monoprice.com/products/pr...seq=1&format=2

http://www.monoprice.com/products/pr...seq=1&format=2


Higher Quality Y Adapter (1 Male, 2 Female) from Radio Shack, $3.59 + Free Shipping:

http://www.radioshack.com/product/in...ductId=3909665
http://www.radioshack.com/product/in...ductId=2102977
http://www.radioshack.com/product/in...ductId=2103638
http://www.radioshack.com/product/in...ductId=2104065
http://www.radioshack.com/product/in...ductId=2103709


Higher Quality Y Adapters (1 Male, 2 Female) from Pro Satellite Supply, $3.99 + Shipping:

Higher Quality Y adapter (1 Male, 2 Female):

http://store.audioholics.com/product...dapter-y-cable, $6.03 + Free Shipping
http://store.cablesplususa.com/2214-29121-001.html, $4.71 + Shipping
http://www.cablesimple.com/index.php...oducts_id=5000, $4.48 + Shipping


High-End Y Adapter (1 Male, 2 Female) from Radio Shack, $11.29 + Free Shipping:

http://www.radioshack.com/product/in...ductId=3237128


High-End (Silver-plated twisted-pair copper conductors with 2 layers of copper shielding and 1 layer of foil shielding):

http://www.parts-express.com/pe/show...number=184-224, $12.32 + Shipping
http://store.audioholics.com/product...female-y-cable, $16.99 + Free Shipping

ADDITONAL INFORMATION AND REFERENCES

http://www.aes.org/technical/documents/AESTD1001.pdf
http://www.aes.org/technical/documen....cfm?docID=248
http://www.ultimateavmag.com/content...nd-lfe-channel
Band-pass filters : FILTERS
http://www.digido.com/subwoofers.html
Low-pass filter - Wikipedia, the free encyclopedia
High-pass filter - Wikipedia, the free encyclopedia
http://www.audioinfo4u.com/Crossover_Network_Basics.htm
Bass Management Basics – Settings Made Simple — Reviews and News from Audioholics
Bass Management: The Right Stuff — Reviews and News from Audioholics
Basics of Bass Management - Axiom Audio
Bass management - Wikipedia, the free encyclopedia
http://www.tmhlabs.com/products/bassmanager.pdf
Low-frequency effect - Wikipedia, the free encyclopedia
UltimateAVmag.com: Bass Management and the LFE Channel
Feature Article
Product Review - Anthem Statement D1
http://www.cerwin-vega.com/themes/th...nding_Bass.pdf
The Misunderstood 0.1 LFE Channel in 5.1 Digital Surround Sound Secrets of Home Theater and High Fidelity
How To Set Up a Subwoofer (or Subwoofers) for Home Theater: BigPictureBigSound
My Apologies to ComfyCurt and Others Who Helped in the Past: "R" Series Crossovers? - Page 2 - Club Polk
http://www.yamahaproaudio.com/downlo...rs/m2tb_en.pdf
Kelly Industries - Bass Manager VST Plug-in

[crazyBLUE]

Wow BD ! that was vary interesting . Deffinatly going to be playing around to see if I have A audio hole . THX ~ You've done it again !!

[got rice]

Another great post Big Daddy... hate to sound like a broken record, but you have taught me a tremendous amount of knowledge about the basics of how things interelate.
Thank you.

[Big Daddy]

It is my wife's fault. She leaves me alone on a Sunday afternoon to go visit her mother and I get bored discussing Bass Management. Don't tell her, but it beats visiting your Mother in Law.

[rpatt]

Thanks Big Daddy. Great information. My receiver sets my front & center speakers as "Large" when I run the auto set up. I want to force them to "Small". What other setting do I need to change if I do this?

[Big Daddy]

Originally Posted by rpatt

Thanks Big Daddy. Great information. My receiver sets my front & center speakers as "Large" when I run the auto set up. I want to force them to "Small". What other setting do I need to change if I do this?

Depending on the low frequency extension of your front speakers, set their high pass frequency to 60Hz or 80Hz. Also make sure the crossover on the back of your subwoofer is turned all the way up to its maximum point.

[rpatt]

The low frequency extension of the front speakers & center is 50Hz.

[Big Daddy]

Originally Posted by rpatt

The low frequency extension of the front speakers & center is 50Hz.

In the receiver, set them to 60Hz to allow for the roll off of the crossover frequency.

[rpatt]

Thanks Big Daddy. I'll give that a try.

[liquidice]

hooray!...another thread from BD to play around in! Really though, excellent guide. When first setting up my newest receiver several months back, this was a hard thing for me to wrap my head around at first, especially the seperate x-over setting for the LFE channel. Actually, I wonder why they even have an option to mess with the x-over of the .1 setting? With all this being said, I feel I should once again go through my settings to see whats-what.

[neos_peace]

I didn't really understand alot of it, BUT I have learned what the LFE stands for. My God I swear everytime you put up a new learning tool. I feel dumber and dumber eveytime. But I Do learn stuff even though most of it comes in greek to me.

[Blu Titan]

Great explanation Big Daddy. I have learned quite a bit from you.

[Johnny Vinyl]

Although you've tried in the past BD, I'm still not buying a sub-woofer just yet!

John

P.S. Another great article and thank you!

[Fors*]

Great guide BD! Always appreciate the info you provide in a layman's version, which makes it easily understandable. I'm still working on the riser leg thing, but I'll get there. Thanks as always!

[Blaumann]

Great thread! Thanks for the info.

[Big Daddy]

Thank you Liquidice, Blu Titan, Neos Peace, Forsberg, and Balumann for all your compliments. I hope you find the thread useful.

As for you John, the turntable nut, I will stick a Grado cartridge and a stylus in your head. You have a limited time to buy a subwoofer. I am waiting.

A man without a subwoofer is a man without love.

Originally Posted by John72953

Although you've tried in the past BD, I'm still not buying a sub-woofer just yet!

John

P.S. Another great article and thank you!

[Johnny Vinyl]

Originally Posted by Big Daddy

As for you John, the turntable nut, I will stick a Grado cartridge and a stylus in your head. You have a limited time to buy a subwoofer. I am waiting.

A man without a subwoofer is a man without love.

I promise you BD, when I'm ready you'll be the person I turn to for advice on the matter.

All kidding aside, I have had a few problems with my turntable and at the moment am without one. With music being the priority over movies, I need to resolve this first before I can even consider a sub. With a little luck I might be searching out that advice by year's end.

John

[mrpink134]

Big Daddy = The Man! He gave me helpful suggestions to make my HT sound great!

[Big Daddy]

Originally Posted by mrpink134

Big Daddy = The Man! He gave me helpful suggestions to make my HT sound great!

You can refer to him as "His Royal Subwooferness".