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One better sub or two subs - Page 3

post #61 of 757
Quote:
Originally Posted by braveheart123 View Post

If I were in your shoes, I'd keep RW-12D in the spot where you had it before (rear wall behind the couch) and put the dual XV-15s in the middle of side walls (one along each wall) such that it becomes an inverted pyramid with each corner holding one sub. There will be an issue of matching the phase, but XV-15s have continuously variable phase knobs, so, you can easily adjust the correct delay. I'd reckon you give this a try and check how your system sounds with 3 subs laid out that way.

Phase and delay are not the same thing. Phase is used to integrate the sub(s) with the mains at the crossover frequency between the mains and sub(s). Most recommend leaving the phase at 0 and letting audyssey do its thing. Otherwise you can really mess things up adjusting the phase.
post #62 of 757
Quote:
Don't forget one of the best sources for answering your sub questions is PSA.

I wonder why Ferrari Company owner is not one of the best drivers of Ferrari.rolleyes.gif Nothing against Tom though
post #63 of 757
Quote:
Phase and delay are not the same thing. Phase is used to integrate the sub(s) with the mains at the crossover frequency between the mains and sub(s). Most recommend leaving the phase at 0 and letting audyssey do its thing. Otherwise you can really mess things up adjusting the phase.

Continuously variable phase knobs cause a certain degree of shift in response, which induces delay. Couple it with sub distance setting in avr and you can easily integrate the sub with mains at whatever the crossover frequency you wish to use.
post #64 of 757
Thread Starter 
Quote:
Originally Posted by braveheart123 View Post

If I were in your shoes, I'd keep RW-12D in the spot where you had it before (rear wall behind the couch) and put the dual XV-15s in the middle of side walls (one along each wall) such that it becomes an inverted pyramid with each corner holding one sub. There will be an issue of matching the phase, but XV-15s have continuously variable phase knobs, so, you can easily adjust the correct delay. I'd reckon you give this a try and check how your system sounds with 3 subs laid out that way.

Ok here is my current setup.


braveheart: Is this what you are proposing? You mentioned to place them in the middle of side walls. Unfortunately this is not possible if I were to go with room length. Total Room Length = 27. Couch placement = (16-14 feet). Half of 27 = 13.5. This makes subs touch the couch. If I were to move them further away from center point say about 6 feet, I ended up like this. (note they are 6 feet away from front walls).

Edited by SherazNJ - 9/19/13 at 8:58am
post #65 of 757
Yeah that's right, go with the layout in the second pic. Mid position does not become very important as now you have a third sub also in the mix that is behind you. The idea is to get max + balanced sub response over a wider listening area near your MLP
post #66 of 757
Some pictures of the entire room would be very helpful for sub placement.
post #67 of 757
Thread Starter 
Quote:
Originally Posted by braveheart123 View Post

Some pictures of the entire room would be very helpful for sub placement.
Will post when I get home. By that time I'm sure you'll be slepping (time difference)
post #68 of 757
Thread Starter 
Quote:
Originally Posted by braveheart123 View Post

Yeah that's right, go with the layout in the second pic. Mid position does not become very important as now you have a third sub also in the mix that is behind you. The idea is to get max + balanced sub response over a wider listening area near your MLP

Just in case if wifeee starts giving hard time, what would be best placement if I were to go with 2 XV15s
post #69 of 757
Quote:
Originally Posted by braveheart123 View Post

Continuously variable phase knobs cause a certain degree of shift in response, which induces delay. Couple it with sub distance setting in avr and you can easily integrate the sub with mains at whatever the crossover frequency you wish to use.

You don't get it. When you change the phase, you're changing the delay so it's different at every frequency. You can get the delay right at one frequency and the trade off is it's guaranteed to be wrong at every other frequency. If the goal is to get the delay setting right between subs, using phase to do so is a really bad idea.

The phase knobs are vestiges of when people only had a single sub and fronts. The knob was to setup a smooth transition between the subs and mains. Since the mains and subs played different frequencies, having the delay being off between the sub and mains wasn't a big deal. But it is a big deal if you're trying to integrate 2 subs together since they play the same frequencies.

The general recommendation is to not mess with the phase if you have two or more subs. Set it to 0 and use other means to integrate the subs.

I've read that on some amps, the phase knob is really a delay knob, it that's the case, then you can use it to integrate two or more subs, but if it is a true phase knob, I would leave it at 0.
post #70 of 757
Quote:
Originally Posted by braveheart123 View Post

Continuously variable phase knobs cause a certain degree of shift in response, which induces delay. Couple it with sub distance setting in avr and you can easily integrate the sub with mains at whatever the crossover frequency you wish to use.

So is it possible to use the continuous variable phase to help time align a near field sub with the "far field" subs? My thought so far is to set the distance setting correctly for the main subs and then play with the phase setting on the near field sub until it sounds right. It seems to be working well, but how do you know when the time alignment is best? Is it simply when overall output is highest? I have an SMS-1 for measurement, but no miniDSP...
post #71 of 757
Quote:
Originally Posted by 5mark View Post

So is it possible to use the continuous variable phase to help time align a near field sub with the "far field" subs? My thought so far is to set the distance setting correctly for the main subs and then play with the phase setting on the near field sub until it sounds right. It seems to be working well, but how do you know when the time alignment is best? Is it simply when overall output is highest? I have an SMS-1 for measurement, but no miniDSP...

If you're using the phase to align two subs, what will happen is it will sound sharp at one frequency and as you move from that frequency, the sound will become more and more blurry. Adjusting the phase may or may not make it sound better or louder to you, but if you want to do the best job possible of integrating subs, I wouldn't use phase to do so. You really need to adjust delay instead,
post #72 of 757
Quote:
I've read that on some amps, the phase knob is really a delay knob, it that's the case, then you can use it to integrate two or more subs, but if it is a true phase knob, I would leave it at 0.

That requires shooting an email to Tom to get it straight off the horse's mouth. I think it is the delay knob.
Unless it is a purpose-built HT room, we cannot have multiple subs placed equidistant from MLP for an avr to phase align with the mains when it has distance setting for only one subwoofer.
post #73 of 757
Quote:
So is it possible to use the continuous variable phase to help time align a near field sub with the "far field" subs?

Yes if the continuously variable phase knob delays the signal. It is same as adding distance to sub in the electrical domain i.e. adding to distance setting in AVR.
Quote:
My thought so far is to set the distance setting correctly for the main subs and then play with the phase setting on the near field sub until it sounds right. It seems to be working well, but how do you know when the time alignment is best? Is it simply when overall output is highest? I have an SMS-1 for measurement, but no miniDSP.

Does your sub has a continuously variable phase knob? You cannot simply do it with a 0/180 phase toggle switch, which simply reverses the polarity that is applied to the entire passband. You can monitor the effects of CVPK in REW if it actually is a delay knob.
post #74 of 757
Quote:
Just in case if wifeee starts giving hard time, what would be best placement if I were to go with 2 XV15s

The sub must go in the room where it sounds best and sonically disappears not where it looks best. Wives yell; take it like a man like me biggrin.gif post some actual pictures and let's see if we are able to work something out. But having said that, a room is the biggest enemy of sound. Acoustics and aesthetics don't go hand in hand unless it is a purpose-built dedicated HT room.
post #75 of 757
Quote:
Originally Posted by braveheart123 View Post

Does your sub has a continuously variable phase knob? You cannot simply do it with a 0/180 phase toggle switch, which simply reverses the polarity that is applied to the entire passband. You can monitor the effects of CVPK in REW if it actually is a delay knob.

The SMS-1 is hooked just to the nearfield sub which gives it continuous phase settings ranging from 0 to 180 (another basic eq is connected to the main subs). The SMS manual mentions a delay is involved with the phase settings. I just need to know how to tell when they are best time-aligned by looking at the measurements of all the subs together. Does a continuous setting work simply that 0 has no delay and the delay increases as the setting increases? Thanks!
post #76 of 757
Quote:
I just need to know how to tell when they are best time-aligned by looking at the measurements of all the subs together.

Where they sound at their loudest. The task becomes cumbersome when you have more than one sub coz they have to be in phase with the mains, as well as, with each other wrt MLP.
Let's say you have 3 subs and you cross them at 80hz with the mains; disconnect all the speakers, put the SPL meter at MLP, and run an 80Hz test tone so that it is played back by the subs only. Then adjust the variable phase knobs where all the subs collectively sound at their max. Now without touching the phase knobs hook up your mains and phase align all subs with mains by changing the sub distance setting in avr, which will collectively adjust phase of all the subs with your mains.
It all depends on your room acoustics, you may or may not have to induce delay on all the subs by changing the continuously variable phase knob.
Quote:
Does a continuous setting work simply that 0 has no delay and the delay increases as the setting increases? Thanks!

Yes. It causes the phase to shift by a certain number of degrees commensurate with where the phase knob is. That induces delay.
post #77 of 757
Quote:
Originally Posted by 5mark View Post

Quote:
Originally Posted by braveheart123 View Post

Continuously variable phase knobs cause a certain degree of shift in response, which induces delay. Couple it with sub distance setting in avr and you can easily integrate the sub with mains at whatever the crossover frequency you wish to use.

So is it possible to use the continuous variable phase to help time align a near field sub with the "far field" subs?

Maybe yes, maybe no.

There is a mathematical relationship between phase and time delay, but in general this relationship holds for just one frequency.

Furthermore, most phase adjusters on subwoofers have a limited range with a maximum that is less than 360 degrees and many are limited to 90 degrees or less. Time delays (usually implemented digitally) generally aren't nearly as limited in terms of frequencies or maximum effects.

Phase controls on subwoofers are usually designed to match the L & R speakers with the subwoofer at just one frequency - the crossover frequency. So, their limitations aren't a problem in that application. But, if you want to time align two subwoofers within their bandpass and they might be sitting across the room from each other, then their limitations can be become stumbling blocks.
Quote:
My thought so far is to set the distance setting correctly for the main subs and then play with the phase setting on the near field sub until it sounds right. It seems to be working well, but how do you know when the time alignment is best? Is it simply when overall output is highest? I have an SMS-1 for measurement, but no miniDSP...

It might work, especially if the subwoofers aren't all that far apart. I believe that tools like the MiniDSP have digital delays that are more flexible, better designed for the purpose, and generally more useful. As others have mentioned some of the more sophisticated automated system tuning facilities particularly Audyssey XT32 have real time delay features that are on-target but most are limited to one subwoofer.
post #78 of 757
Quote:
Originally Posted by 5mark View Post

So is it possible to use the continuous variable phase to help time align a near field sub with the "far field" subs? My thought so far is to set the distance setting correctly for the main subs and then play with the phase setting on the near field sub until it sounds right. It seems to be working well, but how do you know when the time alignment is best? Is it simply when overall output is highest? I have an SMS-1 for measurement, but no miniDSP...

Some more reading on phase vs delay and adjustable phase controls.

http://www.avsforum.com/t/1457414/phase-vs-delay

http://www.avsforum.com/t/1359330/changing-pase-control-on-subwoofer

http://www.avsforum.com/t/600230/exactly-what-does-an-analog-continuously-variable-phase-control-do

http://www.seaton-sound-forum.com/post/is-the-distance-setting-in-a-preamp-the-same-as-a-continuous-phase-control-4780172

http://sound.westhost.com/pcmm.htm
post #79 of 757
Thread Starter 
Ok here are the Pics. I tried to capture all the aspects of room including open area.









post #80 of 757
I would try turning the front sub so the port is firing into the wall...also you might need to run the phase 180 out on one of them.
post #81 of 757
Thread Starter 
Quote:
Originally Posted by basshead81 View Post

I would try turning the front sub so the port is firing into the wall...also you might need to run the phase 180 out on one of them.

Can you please explain what you mean by running the phase 180 out? Also why do I need to do that?
thx.
post #82 of 757
its pretty simple, you turn the phase to 180 on one of the subs...just try it and see if it sounds better or worse.
post #83 of 757
Is your screen fixed or can you roll it up and down?
post #84 of 757
Thread Starter 
The screen is fixed. the sub won't foot even I move the screen all the way up manually.
post #85 of 757
OK in that case, bring the subs closer to your seats along the wall and place each at right angles to the walls i.e. let the port fire into the side wall. Keep about 6" clearance between the port and the wall. Then keep the third one (RW-12D) on the rear wall (behind the middle chair). Keep the phase of all subs at zero for now. You may have to change later. Run audyssey and post your findings. If audyssey sets the sub trim level close to -8/-9dB, bring it up to within +/-3dB of the mid point (00). Change all the speakers to small and cross them at 80hz. Check how your system sounds.
post #86 of 757
Ideal is to first dial all the three subs properly and then run audyssey. But since you are not conversant with REW, it becomes difficult. To get things going without REW for now, all you need is the ISO frequencies test tones from 20Hz-100Hz. Copy them on a flash drive, disengage all the speakers, and play them with only the subs hooked up to your avr. Just write down the spl against the frequencies in excel, and it will plot your in-room response. The test tones and RS analog spl meter correction files are available on the web. We can then adjust the phase between all three subs.

Once we are done removing the dips and peaks from the subs' raw response, audyssey will perform a lot better integrating your subs with the mains during calibration.
post #87 of 757
Shoot me your email address. I will send you ISO frequencies test tones.
post #88 of 757
I understand the need to take measurements and get the highest SPL and frequency etc, but ain't these subs powerful to pressurize your room? At least from the review I read they suppose to.
post #89 of 757
Quote:
I understand the need to take measurements and get the highest SPL and frequency etc, but ain't these subs powerful to pressurize your room? At least from the review I read they suppose to.

A powerful sub is not a a huge hose that can fill up a swimming pool in no time. Bass frequencies are large enough to bounce back and forth several times in a room before they finally dissipate. And every room has certain spots where these frequencies collide constructively creating peaks and certain spots where they meet destructively creating dips and nulls. This is regardless of how powerful a sub is. If you are sitting in a null, you will have very weak or no bass. Sitting in peaky response area gives boomy bass.

The idea to spread your subs across the room is to deal with the room modes effectively in order to have balanced sound over a larger listening area with as less peaks and dips as possible.
post #90 of 757
^well said! I still think he should try setting the phase @ 180 on the rear sub just to see if it makes any difference. I run 2 of my XV15's nearfield at 0 on the phase and the 3rd XV15(mid room on adjacent wall) @ 180... it really smooths the bass out. I suppose I could leave them all at 0 and use the mini dsp to adjust the delay, but the response is pretty good this way. At this time I am doing more listening and less tweaking which tells me it must be close. smile.gif
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