adjusting phase variable 0-180?

[PoorSignal]

How do you adjust it? or is it even needed when using one subwoofer alone?

I turned the phase knob and check the SPL meter at listening position, but doesn't seem to make too much difference

Thanks

[McGarnigal]

What sub do you have? I have the Klipsch SW-10 and never noticed a differance in either position...

[mtbkr]

i maybe wrong but i thought that phase control is off when LFE is active

[Fors*]

Originally Posted by mtbkr

i maybe wrong but i thought that phase control is off when LFE is active

I believe most just leave it at zero, as with one sub its impact is minimal if anything at all. I'm pretty sure it comes more into play when you have 2 subs, as you have to deal with them being in or out of phase, this would be when you would need to adjust this setting.

[StimpsonJCat]

Originally Posted by forsberg21

I believe most just leave it at zero, as with one sub its impact is minimal if anything at all. I'm pretty sure it comes more into play when you have 2 subs, as you have to deal with them being in or out of phase, this would be when you would need to adjust this setting.

It does make a difference with a single sub. If you have an AVR with EQ (Audyssey for example) you just leave it at zero and calibrate. But if you don't have an EQ then I would just try it at 0 and 180 and see which gives you the loudest response. Of course with REW or manual measurements you can find out the best phase position. I'm sure Big Daddy's bass management thread has some information on phase.

[McGarnigal]

My manual said it has to do with location, more if ur sub is in a corner positiion or not.. etc..

[Big Daddy]

Phase setting is covered in A Guide to Subwoofers". I copied the following from there. I hope Big Daddy doesn't kick my a$$.

Setting the Subwoofer’s Phase (Polarity)
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, you have to position them properly and possibly set the phase of one of the subwoofers to 180.

Importance of Polarity (Phase)
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 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

[PoorSignal]

Originally Posted by Big Daddy

Phase setting is covered in A Guide to Subwoofers". I copied the following from there. I hope Big Daddy doesn't kick my a$$.

I have read that before I posted my question
I used test tone but I don't find the phase have much detectable effect on the SPL?

[coolmilo]

Originally Posted by PoorSignal

I have read that before I posted my question
I used test tone but I don't find the phase have much detectable effect on the SPL?

I've never heard of using a SPL meter to adjust phase.

Go here: http://www.soundoctor.com/testcd/ Barry explains how to correctly adjust the phase of subs. Barry's Test CD is well worth $10.

"TRACK 11: 80 Hz, 2 min @ -1dBfs Using 80 Hz is an easy way to set the relative phase of the JL Audio subwoofers to match the "mains", especially if you are using 80 Hz as the crossover freq, such as when connecting to a Home Theater receiver. However, whether or not you are using a bass managed HT system, a separate crossover, or NO crossover, this method is still very useful.

Method A (easier, but less accurate) After you have placed the sub where you want it, put YOUR HEAD equidistant between the sub and the speaker it is CLOSEST TO (for example the RIGHT FRONT). Play the 80 Hz tone and adjust the POLARITY SWITCH of the sub and the PHASE CONTROL until the bass is loudest and cleanest - in other words, the peak.

Method B (more accurate, and more work...) Invert the polarity of the MAIN speaker the sub is CLOSEST TO. Disconnect all the other speakers in the room. Place your head equidistant between the sub and the speaker it is closest to. Play the 80 Hz tone. Adjust the phase control until you hear a distinct NULL. If you can't get a null then flip the POLARITY switch on the JL sub and adjust the phase control again. There should be some setting of the two controls on the JL sub which will provide a rather sharp null - in fact you might be amazed at how easily and completely the bass cancels. Now put the wiring back the correct way to that one speaker.

If you have 2 subs repeat either of the above procedures with the mains speaker the 2nd sub is closest to.

The REASON? When 2 waveforms are IN PHASE and they sum they may get 6dB louder, but when 2 signals are OUT OF PHASE and they sum, theoretically they cancel completely therefore It is much easier to hear the NULL."

[PoorSignal]

if I set my crossover to 80 does that mean right at 80 it plays on both speakers and sub?

and I have found some generated sound files on the internet I can use that instead of a test CD right?

[coolmilo]

Originally Posted by PoorSignal

if I set my crossover to 80 does that mean right at 80 it plays on both speakers and sub?

and I have found some generated sound files on the internet I can use that instead of a test CD right?

Well you can use whatever test files that you want. The Soundoctor's Test CD is the result of 20 years of work according to Barry. Plus, the CD comes with a detailed "how to" docment. The Soundoctor test CD is a real value at $10. I recommend that if you buy it to read the instructions carefully. There is a possibility of the equipment or hearing damage if you are not careful. Most of the recordings are at reference. You will be able to determine the full capability of your sub with this disk.

[BLindsay]

Funny i just saw this, i was just playing with my switch and realized my sub has been out of phase for months

[PoorSignal]

I am curious, does the sub and speaker both play at the cross over frequency?

Or do you have to set the speaker to "large" temporary to allow both the sub and the speaker to play at the same time?

[Big Daddy]

Originally Posted by PoorSignal

I am curious, does the sub and speaker both play at the cross over frequency?

Or do you have to set the speaker to "large" temporary to allow both the sub and the speaker to play at the same time?

Yes, they do. Remember that the crossover filters are not precise cutoff points. They have a gradual slope where the frequencies above or below the filters are gradually cut out.

For example, at 80Hz high pass filter for the front speakers, the filter gradually sends the information over from the speakers to the subwoofer. Depending on the slope of the filter, some information below the crossover frequency will still get to the speakers.