I do not have any fancy meters etc, just my ears.

I have two Polk audio PSW505 in the front of the theater, on a stage. One in each corner.

Should the phase setting for boths subs be the same? Example both set to zero.

Or

Should one be set to Zero and the other set to 180?

You need a spl meter. With a meter you put one @0 and the other you start @0 and dial it to the loudest db. You can't tell by ear but you can try. That's the cheapest way without using an EQ

If you can get someone to switch the phase while you are sitting in the prime listening position you will hear which sounds better.

You will want the two subs set the same. Whether they should both be 0 or 180, you will need to determine.

You will want the two subs set the same. Whether they should both be 0 or 180, you will need to determine.

I agree. Trying using your receivers test tones when making the adjustment. Pink noise is more sensitive to your ears and will make it a lot easier. ;)


Ian

Should one be set to Zero and the other set to 180?maybe

maybe

And you would want to cancel the bass at whatever freq the phase is "set" for what reason?

When you have two signals that are 180° out, they will cancel.

But since that is a phase control and not a polarity control, the cancellation would be freq specific. If it was a polarity control, then you would have across the band cancellation.

And you would want to cancel the bass at whatever freq the phase is "set" for what reason?I wouldn't. That's why I would not simply set them to the same phase setting and be done with it.


When you have two signals that are 180° out, they will cancel.Throwing 2 subs in a room and setting their phase identically does not at all ensure that they are in phase with one another. Because the OP said ".....in the front of the theater.......... One in each corner" setting them identically may indeed be the correct setting. Or it may not.


But since that is a phase control and not a polarity control, the cancellation would be freq specific. If it was a polarity control, then you would have across the band cancellation.I do not know what these subs are equipped with. The OP's post hints that they may just have a switch that can be set to 0° or 180°. If that is the case, then the switch simply flips the polarity. But if the OP's subs have continuously variable phase knobs, then they should most definitely be used as such, and not simply set to identivcal settings.

The two subs are both on the front stage in the left and right corner. It would be impossible for them to be set up properly with the phase reversed from each other.

The Polk psw505 only has a switch, so the phase is eather 0 or 180. There is no knob to vary the phase setting. The input is the LFE both on the receiver and the Sub.

i have 2 velodyne splr200's in front myself--i ezperimented a bit--for me 90 degrees is best and the second one set the same was best. hope it helps--in your case id start with one try 0 and 180 and whichever is audibly best (it should be fairly obvious) and set the 2 identically.

i have 2 velodyne splr200's in front myself--i ezperimented a bit--for me 90 degrees is best and the second one set the same was best. hope it helps--in your case id start with one try 0 and 180 and whichever is audibly best (it should be fairly obvious) and set the 2 identically.

I agree, using the same setting in most cases makes sence. However you can't always assume that it will. I have 2 identical subs. They are on opposite walls in front of my mains in the same location. One is set to 180, the other to zero, regardless of whether I use just one or both. I can only assume that the polarity on one of them is reversed.

Ian

what do people with 2 MFW's normally do? The phase can be adjusted from 0-180 with the knob. I have 2 of them maybe only 6 feet apart....the audio stand is in between them. Right now I have one at 180 and one at 0 but I'll try the test tone on the receiver and have someone adjust them while i listen like someone said!

Yeah if the are stacked or on the front stage they should be the same. But if they are opposite corners or not symmetrical placed then phase or distance need to be adjusted.

Thank for all the input. I have them both set at 0 phase and that sound great. Thanks.

I can only assume that the polarity on one of them is reversed.Why? :confused:

I have 2 of them maybe only 6 feet apart....the audio stand is in between them. Right now I have one at 180 and one at 0 but I'll try the test tone on the receiver and have someone adjust them while i listen like someone said!

Set both to zero phase and measure the output at the listening position using an SPL meter. Both subwoofers are within a 1/4 wavelength distance at most frequencies which should ensure proper coupling power.

Attempting to find the correct phase by ear is a complete waste of time in most cases as the frequencies being reinforced (or canceled) may fall outside the bandwidth in the source material.

Regards,

If I were to purchase a SPL meter (Rat shack sell for $50) I would be waisting my money as I do not know the first thing about using one? Or if even the Rat Shack one is worth $50?

If I were to purchase a SPL meter (Rat shack sell for $50) I would be waisting my money as I do not know the first thing about using one?

It doesn't require a PHD to use an SPL meter. I've seen senile people use these things with success.

All that you want to do is observe the results when both phase controls are set to the same value. This is very easy to do. If identical phase values give you the greatest output at and around the crossover region then you know that both subwoofers are in phase. An out of phase condition will show a reduction in output at this point.

Besides checking phase, with an SPL meter you can level match all speakers within a system for a balanced result. It is your best friend.

Regards,

It doesn't require a PHD to use an SPL meter. I've seen senile people use these things with success.

All that you want to do is observe the results when both phase controls are set to the same value. This is very easy to do. If identical phase values give you the greatest output at and around the crossover region then you know that both subwoofers are in phase. An out of phase condition will show a reduction in output at this point.

Besides checking phase, with an SPL meter you can level match all speakers within a system for a balanced result. It is your best friend.

Regards,
Exactly. You can read the correction sticky above also. But even if you don't correct the db you still can level match all your speakers to whatever db. As long as they are all the same from your listing position. Maybe the sub a few db hot. The time it took you to post and read this bboard you should be able to learn how to use a spl meter.

I don't think I can make this any clearer. An spl meter is a must if you want to accurately balance out your system. However, if you can't tell if a sub is in phase at moderate sound levels, when using pink noise, it's time to go to the ear doctor. ;)

Ian

If I were to purchase a SPL meter (Rat shack sell for $50) I would be waisting my money as I do not know the first thing about using one? Or if even the Rat Shack one is worth $50?

Go to th is site and all of yhour questions can be answered: http://www.avsforum.com/avs-vb/showthread.php?t=824554.

Bill

It doesn't require a PHD to use an SPL meter. I've seen senile people use these things with success.

All that you want to do is observe the results when both phase controls are set to the same value. This is very easy to do. If identical phase values give you the greatest output at and around the crossover region then you know that both subwoofers are in phase. An out of phase condition will show a reduction in output at this point.

Besides checking phase, with an SPL meter you can level match all speakers within a system for a balanced result. It is your best friend.

Regards,
The ONLY thing a SPL meter looks at is SPL. There is NO freq content whatsoever-assuming a flat response.

It will respond to the HIGHEST level it reads-without regard to the freq that is producing it.

Assuming a variable phase control, that means that it is simply adjusting the time relationship at the crossover freq. A switch is a TOTALLY different animal and is actually a polarity control NOT a phase control. A phase control indicates a particular freq is involved. A polarity switch flips the polarity of ALL freq 180°, but they get mislabeled all the time as phase switches-even in the pro world-that should know better:eek:

If you get the time off between two different arrivals you will have what is known as comb filtering. That is a series of PEAKS and DIPS that occur at regular intervals.

Read this for a better idea of what is happening. http://www.dbasi.com/files/resource/loudspeaker_placement_rev041021.pdf

This was written by me for a higher freq, but the same math applies.

It is very possible to have a messed up freq response and STILL have an increase in level, due to the peaks that occur.

So it may be louder, but does it SOUND any BETTER?

so it's a waste of time to set phase with pink noise and my spl meter right?

so it's a waste of time to set phase with pink noise and my spl meter right?
You will get "results" but are they the correct results? In all honesty you are not using the right tool for the job. But if it gets you results you are happy with, then no big deal. If you are looking for an increase in SPL, then all that means is that you now have a "hump" somewhere at some unknown freq.

The only way you can set it correctly is to use a time blind type instrument. Those are not cheap and all carry a steep learning curve.

There are many factors that will affect the "correct" phase adjsutment. Settings (such as loudspeaker size-level-delay etc) within the processor, physical location of mains and subs in relation to a particular listening position, crossover and eq settings and so forth.

Remember that phase is time and phase shift is a time/distance shift. As you move around the absolute phase is shifted also and the distance between arrival times changes also.

Well last night my daughter and her husband watched the new Batman move and they both said there was a little too much Base. And that some times the base over shadowed the the entire audio track.

I watches two non action movies and the base was fine.

So did my second Sub cause the problem or is it the Batman movie audio track....

I hear you loud and clear, however i've done nothing but set the spl level and left the phase @ 0, didn't try anything else, it is variable from 0 to 180*, so maybe it's worth a shot to see if it makes it any better as i'm probably just moving the hump anyway

You will get "results" but are they the correct results? In all honesty you are not using the right tool for the job. But if it gets you results you are happy with, then no big deal. If you are looking for an increase in SPL, then all that means is that you now have a "hump" somewhere at some unknown freq.

The only way you can set it correctly is to use a time blind type instrument. Those are not cheap and all carry a steep learning curve.

There are many factors that will affect the "correct" phase adjsutment. Settings (such as loudspeaker size-level-delay etc) within the processor, physical location of mains and subs in relation to a particular listening position, crossover and eq settings and so forth.

Remember that phase is time and phase shift is a time/distance shift. As you move around the absolute phase is shifted also and the distance between arrival times changes also.

Well last night my daughter and her husband watched the new Batman move and they both said there was a little too much Base. And that some times the base over shadowed the the entire audio track.

I watches two non action movies and the base was fine.

So did my second Sub cause the problem or is it the Batman movie audio track....

Maybe your system levels were not set up properly.

Well I tried all variations and saw no difference in output from the listening position, *shrug* left it @ 0 degrees.

I did however calibrate the sub with the AVR @ 0db instead of -5 or -10db though, just to try, since the AVR goes from -10 to +10db on the sub.

I did calibrate about 6db hot though, I don't listen at "reference" levels and any less and it's like the sub isn't there

Remember that phase is time............Phase is NOT time. :rolleyes:

What is phase? I thought if you adjust your distance it would do the same as phase? So that to me means something other than time. Unless it the time it take the sound to travel to your seated area?? Dunno

Guess phase could be time
http://en.wikipedia.org/wiki/Phase_(waves)

The ONLY thing a SPL meter looks at is SPL. There is NO freq content whatsoever-assuming a flat response.

I use a real time analyzer to observe phase changes over the entire frequency spectrum. Otherwise observing phase changes will demonstrate either a depression in the response over a portion of the frequency range or an elevation in the same (or different) range due to phase shifts.

It will respond to the HIGHEST level it reads-without regard to the freq that is producing it.

Usually an in phase condition would signify an output increase at and around the crossover region. Using an SPL meter can at least monitor the changes but I prefer to use more accurate instrumentation. Those with Room EQ wizard can monitor these changes too with much success.

Assuming a variable phase control, that means that it is simply adjusting the time relationship at the crossover freq.

Time and frequency are inversely related, yes ? Adjusting the "time relationship" at the crossover frequency can cause a dip over a small section of the frequency curve or create peaks somewhere else as the two are intimately intertwined.

If you get the time off between two different arrivals you will have what is known as comb filtering. That is a series of PEAKS and DIPS that occur at regular intervals.

I understand full well what comb filtering is.

It is very possible to have a messed up freq response and STILL have an increase in level, due to the peaks that occur.

An out of phase condition will show a pretty big reduction in output at and around the crossover region and especially below at frequencies whose wavelengths interact at 180 deg. Flipping the switch or changing the phase control continuously until you have minimized this interaction is key. Using an SPL meter can still be beneficial in some ways but I wouldn't say it's the best device to monitor these changes.

So it may be louder, but does it SOUND any BETTER?

Who knows. If frequencies are louder at the crossover point which allow a better splice between main speaker and subwoofer then the integration should be better (ie no holes in response). It should sound better.

Pleasuring talking with you Ivan.

Regards,

Lets assume just an SPL meter for this discussion. Let's say you have adjusted the phase control for a maximum reading. Lets also assume that you no longer have a hole in the response.

But what IF you now have a hump in the response? There is no way of knowing without better measurement.

It is also VERY possible that adjustment of the phase control has resulted in the "hole" being filled in. BUT it is also just as possible that you have now created other holes on either side of the intended one being created.

It is just not as simple as adjusting for a peak iwth a SPL meter-that is all I am trying to say.

As the saying goes "For every complicated question, there is a simple-easy to understand-WRONG answer".

Most of this thread has been discussing the "phase" setting. There are two parts of setting phase with multiple subs. The first is to get the two subs in phase with each other. The second is to get the combined output of the two subs in phase with the main speakers at the crossover point, (relative phase is only really important at, and around, the crossover frequency; above and below that, it is "relatively" unimportant.)

For the first part, (getting the two subs in phase with each other), if the two subs are equidistant from the primary listening position, in general, they should be set to the same phase. This will ensure that the positive waves from both subs arrive at the LP *together* and augment each other, (and vise versa with the negative waves.)

If the two subs are not equidistant from the LP, then you almost certainly need some sophisticated measuring equipment, as well as a continuously variable phase selection to optimize the phase settings. If all you have is a simple polarity switch, then play around with it and see which sounds better. If you can perceive a difference, go with it.

For the second part, (getting the combined output in-phase with the speakers), you'll need a frequency sweep like that on the Avia disc. Play the sweep through the crossover frequency. Adjust the combined phase of the two subs to optimize the output at the crossover frequency.
Well last night my daughter and her husband watched the new Batman move and they both said there was a little too much Base. And that some times the base over shadowed the the entire audio track.

I watches two non action movies and the base was fine.

So did my second Sub cause the problem or is it the Batman movie audio track....
Regarding the above issue, your main problem is not phase; it is the relative "level" settings between the mains and subs. Since you have no way of measuring level, (i.e., SPL or Sound Pressure Level), you have no idea if the sub levels are set properly relative to your mains. Until you get this setting correct, the phase setting is immaterial.

Get an SPL meter, play some broadband noise through the speakers and through the subs and ensure that they are at the same levels. THEN, play around with phase to improve the response at the crossover frequency.

Craig

What is phase? I thought if you adjust your distance it would do the same as phase? So that to me means something other than time. Unless it the time it take the sound to travel to your seated area?? Dunno

The distance setting in the receiver/pre/pro is used to time the speakers and subwoofer(s) so that they all arrive at the central listening position at the same time. The receiver/pre/pro can add delays to one or more speaker signals, or the subwoofer signal to effect this. This delay affects the entire bandwidth of the speaker or subwoofer.

The phase control on the sub is used to adjust the relative phase of the subwoofer at the crossover point only.

Craig

Get an SPL meter, play some broadband noise through the speakers and through the subs and ensure that they are at the same levels. THEN, play around with phase to improve the response at the crossover frequency.

Craig

So for the absolute beginer... using the SPL meter too set the volume level of the two front mains to the exact same reading on the SPL meter as the Sub-Woofer?

So for the absolute beginer... using the SPL meter too set the volume level of the two front mains to the exact same reading on the SPL meter as the Sub-Woofer?
Correct. Play some broadband noise, either from a test DVD like Avia, or the test tones in your receiver/pre/pro. Place the SPL meter at ear level at your listening position, pointed straight up, set to "Slow" and "C-Weighting". Using the level trims i the receiver, set all the levels (speakers and subwoofer), to 85 dB if using Avia, or 75 dB is using the receiver's test tones. This will "calibrate" the levels of all speakers/subwoofers in the system.

Before doing this, I suggest you set the outputs of both subwoofer to be exactly the same, (or run them in Master/Slave if they have that capability.) Set their volume controls so that they are exactly the same and so that the combined output is between 70 and 80 dB. Set their phases to "0", (if they are equidistant to the listening position.)

Craig

OK so I need to buy the Radio shack SPL meter and the Avia disk. Is the digital or analog meter better?

What is phase? I thought if you adjust your distance it would do the same as phase? So that to me means something other than time. Unless it the time it take the sound to travel to your seated area?? DunnoGuess phase could be time
http://en.wikipedia.org/wiki/Phase_(waves)Phase is NOT time. They are related, but they are not the same thing.

The distance setting in an AVR is for time management. Adjusting the distance settings changes the timing of the speakers and sub relative to one another. And that is all that it does.

The distance setting affects the relative timing which affects the phasing.

OK so I need to buy the Radio shack SPL meter and the Avia disk. Is the digital or analog meter better?
What receiver do you have? Does it have any kind of auto-cal feature? Does it have test tones?

Craig

Well last night my daughter and her husband watched the new Batman move and they both said there was a little too much Base. And that some times the base over shadowed the the entire audio track.

I watches two non action movies and the base was fine.

So did my second Sub cause the problem or is it the Batman movie audio track....

It can be a number of things. Sub placement, SPL setting, Phase or improper calibration.

We tend to think distorted bass is normal so accurate bass some time seems too low. If our sub plays down low enough, the crossovers are set right for your satellites and they are placed correctly, you are on the right track.

Recent research suggests two subs should be placed mid wall opposite each other.

Also, a Sound Pressure Level meter is ESSENTIAL to properly calibrate your speakers.

What receiver do you have? Does it have any kind of auto-cal feature? Does it have test tones?

Craig

It is a Sony DA777ES and yes it does have test tones, but it does NOT have any automatic setup features.

I'm contemplating upgrading to the new Outlaw 997 and 5 channel power amp, Outlaws 7500. The Outlaw also has the Trinnov Optimizer, so it should be easer to set up. The current Sony receiver does not decode Dolby TruHD on any of the newer audio.

Plus my LSi series speakers are 4ohm. Which makes it hard to find a receiver as i really liked the Denon 3808. But the Denon on does 8ohm.

It can be a number of things. Sub placement, SPL setting, Phase or improper calibration.

We tend to think distorted bass is normal so accurate bass some time seems too low. If our sub plays down low enough, the crossovers are set right for your satellites and they are placed correctly, you are on the right track.

Recent research suggests two subs should be placed mid wall opposite each other.

Also, a Sound Pressure Level meter is ESSENTIAL to properly calibrate your speakers.

I'm kind of stuck the the sub placement. They are on the sand filled stage and in the front right and left corners, behind the screen wall.

So my first objective is to get the levels correct, by using a SPL meter. Thats step one. The other option is to hire a Pro to adjust the tune the audio. I did that with the projector and Doug made a 100 times better picture then I ever did.

It is a Sony DA777ES and yes it does have test tones, but it does NOT have any automatic setup features.
Then you don't necessarily need Avia. You just need the SPL meter. However, Avia will give you a lot of other excellent information and testing capability.

And with that receiver, I hope you are using the Bass Management, (i.e., using the crossovers.)

Craig

Found the test tone option on the receiver and purchased a SPL meeter at Radio Shack. Here was the first go round:
Front left: 68 Center:65 Right:68
RearLeft: 70 Right:69
LFE Left: 83 Riight: 80

So my guess is that all these need to be the same. So I will use the equalization setting to adjust everything to 69.

Found the test tone option on the receiver and purchased a SPL meeter at Radio Shack. Here was the first go round:
Front left: 68 Center:65 Right:68
RearLeft: 70 Right:69
LFE Left: 83 Riight: 80

So my guess is that all these need to be the same. So I will use the equalization setting to adjust everything to 69.It isn't an "equalization setting". It is simply the individual channel level trim settings. And most people calibrate to 75dB. 69dB will work, though.

And how are you going to calibrate the subs? ;) :D

It isn't an "equalization setting". It is simply the individual channel level trim settings. And most people calibrate to 75dB. 69dB will work, though.

And how are you going to calibrate the subs? ;) :D

My mistake i did set the level for each channel. I have not done any of the equalization setting or changes any of the crossover setting, do not know what to set them too or how to measure.

The sub levels and be adjusted on the receiver by using the levels or to volume know on the back. For now I will use the level settings on the receiver as i can not get to the subs without taking down the screen.

Oh i did correct the distant settings the center was too far 16 vs 11 and the sides were 4 and should be 7 and the sub was 4 and should be 12.

My mistake i did set the level for each channel. I have not done any of the equalization setting or changes any of the crossover setting, do not know what to set them too or how to measure.

The sub levels and be adjusted on the receiver by using the levels or to volume know on the back. For now I will use the level settings on the receiver as i can not get to the subs without taking down the screen.

I have a condensed explanation of how to do so here.

http://www.hometheatershack.com/forums/rew-forum/13662-can-i-use-rew.html#post121981