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post #1 of 95 Old 07-03-2013, 02:32 PM - Thread Starter
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What's the difference between switching the phase(0/180) vs manually adjusting the subwoofer distance? I finally got around to tuning the sub. I've always relied on my towers(klipsch kg 3.5's) to handle the bass. During the living room remodel last year I picked up an original Hsu vtf-2(the old 10 incher), which i assume is the same as the current vtf-1?, for $150. I threw it where I put the in-wall wiring, which was nearfield. Today I performed the subwoofer crawl and found where I'd like to finally put it. I put on a cd to tune it, but i could tell the timing of the bass was off in the new location, so I switched the phase which improved it, but it still wasn't right. Then I remembered the sub distance setting, which was set by YPAO from the previous location, and I adjusted the distance to liking. Is there any difference in setting the distance vs. switching the phase? Is that what "phase alignment" is, timing?
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post #2 of 95 Old 07-03-2013, 03:21 PM
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Not the same thing. You could place the sub in many locations around the room, and all could be the same distance from the seat. Lets say 12 ft.
But only when the sub location is near the mains (preferably in between) the phase is 0.
If the sub is along one of the side walls or in back, then the phase most likely needs to be 180.
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post #3 of 95 Old 07-03-2013, 07:29 PM
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Originally Posted by Tstan7777 View Post

What's the difference between switching the phase(0/180) vs manually adjusting the subwoofer distance?
0/180 swaps polarity. The distance control precisely time aligns the sub to the mains at the crossover frequency, giving exactly the number of degrees of phase shift required.

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post #4 of 95 Old 07-03-2013, 09:48 PM - Thread Starter
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So one is just a more precise way of doing the same thing? When i switched polarity the timing improved but was still off. I went back to 0 and tried changing the distance, which worked better.
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post #5 of 95 Old 07-04-2013, 06:46 AM
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So one is just a more precise way of doing the same thing?
Being able to adjust the phase/time align by increment is a lot more precise than just having two settings. A two position polarity switch is better than nothing, but just.

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post #6 of 95 Old 07-04-2013, 07:35 AM
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Originally Posted by Tstan7777 View Post

So one is just a more precise way of doing the same thing? When i switched polarity the timing improved but was still off. I went back to 0 and tried changing the distance, which worked better.

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Originally Posted by Bill Fitzmaurice View Post

Being able to adjust the phase/time align by increment is a lot more precise than just having two settings. A two position polarity switch is better than nothing, but just.

Its not the same thing. The distance setting for a sub is no different than setting the distance for other speakers. Those distance settings are so the sound from each speaker reach the seat at the proper interval of time. The phase switch 0,180, or a rotary 0~180 is to set the piston action of the sub driver to the same polarity of the main drivers.
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post #7 of 95 Old 07-04-2013, 08:03 AM
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Originally Posted by 4DHD View Post


Its not the same thing. The distance setting for a sub is no different than setting the distance for other speakers. Those distance settings are so the sound from each speaker reach the seat at the proper interval of time. The phase switch 0,180, or a rotary 0~180 is to set the piston action of the sub driver to the same polarity of the main drivers.
That's exactly what I said in my first post. Your point is? rolleyes.gif
From a technical standpoint a polarity change and a time align change will both result in a 180 degree phase shift, the difference being that a polarity change will result in 180 degrees of phase shift at every frequency, while a time align change will result in 180 degrees of phase shift at one frequency, with varying degrees of shift at other frequencies, based on their wavelengths.

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post #8 of 95 Old 07-04-2013, 08:07 AM - Thread Starter
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So, 4DHD, you're saying they are totally independent? In which case the sub can be in time but out of phase, or vice versa, out of time but in phase? So lets go back. I moved the sub and it was clearly out of time. Which should you go about setting first? Try to find the correct phase or set the distance and get the time right? I would assume you want to get the time right first. Of course you could let room correction set all this stuff, but I'd like to know how to do it manually. What if room correction was wrong or you wanted to tweak from there?
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post #9 of 95 Old 07-04-2013, 08:34 AM
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Originally Posted by Tstan7777 View Post

In which case the sub can be in time but out of phase, or vice versa, out of time but in phase?
Both are possible. It would be unusual where you'd need to both reverse the polarity and time align to get it right, but not out of the question, the most common instance being with a sub that's in the back of the room and it happens to be separated from the mains and subs in the front of the room by 1/2 wavelength at the crossover frequency.

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post #10 of 95 Old 07-04-2013, 08:36 AM
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I always set the distance first, then if it sounds off, then I toggle the phase switch. And yes, they are independent of each other.
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That's exactly what I said in my first post. Your point is?
I stated in MY first post the two were not the same thing. But even after our combined 3 posts, 7777 was still thinking the two were doing the same thing. I was stating again, that distance and phase are not the same thing.
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post #11 of 95 Old 07-04-2013, 09:35 AM - Thread Starter
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Ok, i think we're all in agreement phase and time alignment(distance setting) are not the same. I researched a little more so let me make this statement......they're both about time. But one, phase, is about timing when the woofers fire so that sub/sats are not fighting each other and cacelling. Distance is more about timing when the soundwaves reach us, so that multiple woofers are not reaching us at different times. Is this the answer i was looking for?
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post #12 of 95 Old 07-04-2013, 09:46 AM
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^^^^YES. lol
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post #13 of 95 Old 07-04-2013, 09:56 AM
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Quote:
Originally Posted by Tstan7777 View Post

Ok, i think we're all in agreement phase and time alignment(distance setting) are not the same. I researched a little more so let me make this statement......they're both about time. But one, phase, is about timing when the woofers fire so that sub/sats are not fighting each other and cacelling. Distance is more about timing when the soundwaves reach us, so that multiple woofers are not reaching us at different times. Is this the answer i was looking for?
Nope. First, ignore the 0/180 label on the polarity switch, it only confuses the issue. Many refer to that as a phase control, but it isn't, other than by reversing polarity it also happens to change the phase of that source by 180 degrees. Second, in the subwoofer frequencies it doesn't matter all that much if different sources are reaching us at different times, as we can't hear that unless the time differentials are longer than the size of most rooms will allow for. What we can hear is when that time differential results in two or more sources being in the vicinity of 180 degrees out of phase at the crossover frequency, and that's what time align compensates for. We can't hear the time differential, we hear the phase sourced cancellations associated with it. One could dial in the correct amount of phase shift without altering the time align, but using time align is easier as far as the circuitry goes.

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post #14 of 95 Old 07-04-2013, 10:02 AM
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Quote:
Originally Posted by Tstan7777 View Post

Ok, i think we're all in agreement phase and time alignment(distance setting) are not the same. I researched a little more so let me make this statement......they're both about time. But one, phase, is about timing when the woofers fire so that sub/sats are not fighting each other and cacelling. Distance is more about timing when the soundwaves reach us, so that multiple woofers are not reaching us at different times. Is this the answer i was looking for?

It is best to leave the phase toggle switch to 0. I always set the physical distance of the sub from MLP first, and then time align it wrt mains obviously for one particular frequency. IMO it is useless to set a continuously variable phase dial. Because you can only set phase for ONE particular xo frequency. At some other frequencies, the sub may be exactly out of phase coz of differing wavelengths but it will still be time aligned for one seating location.

There are 3 variables; distance of sub from MLP, distance of sub from the mains, and the distance of mains from MLP. So, if you perfectly time align a sub keeping all the other things constant; that will only be valid for that very listening position and for that very crossover frequency. You move a foot either side, you may find the sub out of phase wrt to mains and the MLP for the crossover frequency set earlier.

It's always better to have subs in pair and both set equidistant from the MLP and mains; but of course added cost is the opposing factor. That way you can get away with being out of phase by a large margin and MLP area extends beyond money seat.

It is far easier to tame the sub in time domain than the frequency domain. Multiples is the way to go or else you may have to make compromises if you stick with one sub.

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post #15 of 95 Old 07-04-2013, 10:23 AM
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I believe the answer is the following -

Phase/Delay are both about time but when you adjust delay you are adjusting a given amount of delay in milliseconds across the frequency range, this affects the phase of each frequency differently, some getting less degrees of shift and some getting more but all of them getting the same amount of delay in ms. When you adjust phase you do this across the frequency range as well here the phase degree change is constant but the time delay in milliseconds is different for each frequency.

You want all the frequencies to arrive at basically the same time or as close as possible, naturally the low end tends to be delayed a bit. Phase/delay are two different tools to approach the same problem, one delaying in absolute time (milliseconds) across frequency and the other delaying in relative time (phase degrees) in respect to a given frequency.

To clarify each frequency has different wavelengths, this means that an absolute time delay will delay each frequency to different degrees, phase instead maintains a constant delay in respect to frequency but not absolute time, as in lower frequencies have longer wavelengths and higher frequencies have shorter wavelengths. Example -

One cycle at 1000Hz is 1 ms while at 100Hz is 10 ms, this corresponds to a 360 degree phase shift (one cycle) at each of these frequencies so if you delay using 10 ms then 1000Hz is delayed by ten cycles but 100Hz is delayed by 1 cycle, if you use phase and set it to 360 degrees phase shift (one cycle) then 100Hz is delayed 10ms but 1000Hz is delayed 1 ms but they are both delayed by one cycle. It might be easier to think of phase as "constant cycle delay across frequencies".

That is my understanding of it, if I made an error hopefully someone can point it out.
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post #16 of 95 Old 07-04-2013, 11:19 AM
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More precisely phase matching has two parts; one is the time domain and second the frequency domain. Time alignment is very easy to achieve; while the later is always a trade off.

You can only match the phase in frequency domain for one particular frequency and that's what we all do while setting the crossover frequency on AVR. On other frequencies there is always a phase shift unless of course somebody comes up with a live feedback system in either the sub or AVR or any device between the sub and avr that adjusts the phase in real-time by a certain number of degrees for the frequency being played and also injects the correct delay to time align the whole system. Though difficult to achieve; but very much possible wink.gif

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Quote:
Originally Posted by braveheart123 View Post

Time alignment is very easy to achieve

Most home systems are actually not aligned correctly but we think they are because we are used to the sound.
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post #18 of 95 Old 07-04-2013, 12:08 PM
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Most home systems are actually not aligned correctly but we think they are because we are used to the sound.

When are we going to actually enjoy our HT systems? rolleyes.gif

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post #19 of 95 Old 07-04-2013, 12:14 PM
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Originally Posted by braveheart123 View Post

More precisely phase matching has two parts; one is the time domain and second the frequency domain.
They're the same thing. You cannot separate the one from the other.
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You can only match the phase in frequency domain for one particular frequency and that's what we all do while setting the crossover frequency on AVR. On other frequencies there is always a phase shift
It doesn't matter. You can only hear the effect of phase when there are two or more sources reproducing the same frequency, and then only when sum of the shift totals in the vicinity of 180 degrees. When there is only one source you can't hear phase, and a good thing too, as speakers do not have constant phase, it varies across their band width. That complicates the entire time/phase alignment issue. For instance, at 80Hz the sub may have 20 degrees of phase lead, while the mains may have 30 degrees of phase lag, so there's a 50 degree offset even before distance enters the equation.
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a live feedback system in either the sub or AVR or any device between the sub and avr that adjusts the phase in real-time by a certain number of degrees for the frequency being played and also injects the correct delay to time align the whole system.
Unnecessary, as it would be fixing something that isn't broken. This is a phase response chart of a single driver, and the swings from plus to minus 180 degrees are perfectly normal and totally inaudible.

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post #20 of 95 Old 07-04-2013, 12:30 PM
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When are we going to actually enjoy our HT systems? rolleyes.gif

Whenever we want wink.gif
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post #21 of 95 Old 07-04-2013, 12:39 PM - Thread Starter
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Lol, well, I currently am. My daughter is re-watching Oz as I speak. To roll things back, I bought a new cable so that I could move the sub to more locations. It was nearfield between the cubbyhole created by the intersections of the couch and love seat about 3/4 down the long wall(20x14 room). My wife pretty much hates the sub. It's not so much the look as it is the sound. Apparently she hates deep bass. Well I moved it closer to the front. I tried to corner load the sub first, it is a 10" incher after all, but that was just too boomy. Yesterday I was home alone and tried the sub crawl. I was close moving the sub to the front corner, but it needed to bee moved out about 3ft along the long wall to loose the boominess. Anywhere along the rear of the room was way too uneven. I had run YPAO from the previous position and never had trouble with the "timing" of the sub. After finding the position I liked I sat down for some critical listening. It was obvious that the sub was not firing in time with the mains, which produce a fair amount of bass being 8" woofers. In addition, I have found the sub is not able to produce acceptable bass above 60hz when listening to music so I cross over at 60z.. I tried the phase switch and moving it to 180 degrees helped but was not sufficient. I switched it back to 0 and changed the sub distance until the kick drum seemed in time(I was listening the 3 Doors Down). It made me wonder what the difference was, because I thought that phase is what adjusted when the woofer fired which in turn would adjust the timing. I was able to get the sub to an acceptable setting and enjoy it last night and now today. But it brought up the question of what was the difference. So how about this statement......Switching the phase will adjust the timing of the sub across all frequencies and adjusting the delay will adjust the timing of the sub at the xover frequency? Or do I have that backwards, lol?
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post #22 of 95 Old 07-04-2013, 12:54 PM
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So how about this statement......Switching the phase will adjust the timing of the sub across all frequencies and adjusting the delay will adjust the timing of the sub at the xover frequency? Or do I have that backwards, lol?
Switching the polarity changes phase by 180 degrees globally. Adjusting delay changes phase of every frequency as well, but each by a different amount. For instance, 180 degrees shift at 80Hz is 7 feet. That same 7 feet is 90 degrees at 40Hz, 45 degrees at 20Hz.
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My wife pretty much hates the sub. It's not so much the look as it is the sound. Apparently she hates deep bass.
Women are genetically predisposed to not like low sounds, as in the wild they tend to warn of potential dangers, as in lightning and stampeding herds. Men are genetically predisposed to go towards low sounds, as those stampeding herds might represent dinner.

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post #23 of 95 Old 07-04-2013, 01:01 PM
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If you are using YPAO or other room correction, the phase and timing issues are generally done for you. If the bass is boomy you may need to play with the XO on the avr, avr and sub. There most likely is a bass bump around the XO. PEQ is one of the easiest ways to correct this type of problem It can be difficult to get the roll off of the main to blend with the XO . Phase changes has frequencies are lowered. The system has an absolute phase and a relative phase.

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post #24 of 95 Old 07-04-2013, 09:43 PM
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Originally Posted by Bill Fitzmaurice View Post

For instance, 180 degrees shift at 80Hz is 7 feet. That same 7 feet is 90 degrees at 40Hz, 45 degrees at 20Hz.

How did you figure this out??rolleyes.gif

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post #25 of 95 Old 07-04-2013, 10:30 PM
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Originally Posted by braveheart123 View Post

How did you figure this out??rolleyes.gif

Speed of sound / Frequency = Wavelength

1126 ft/s / 80 Hz = 14 feet

Phase shift / full cycle (360 degrees)

180 degrees / 360 degress = 2

14 feet / 2 = 7 feet

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post #26 of 95 Old 07-04-2013, 10:40 PM
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Originally Posted by kwarny View Post

Speed of sound / Frequency = Wavelength

1126 ft/s / 80 Hz = 14 feet

Phase shift / full cycle (360 degrees)

180 degrees / 360 degress = 2

14 feet / 2 = 7 feet

I know the wavelength bit, but why divide 80Hz wavelength by 2? Could you explain?

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post #27 of 95 Old 07-05-2013, 08:59 AM
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you are 180 degrees out of phase at 1/2 cycle.theoretically, complete cancellation.
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post #28 of 95 Old 07-05-2013, 09:13 AM
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theoretically, complete cancellation.
Only if the level from the two sources is exactly the same and in an anechoic environment. As soon as you add a floor, ceiling and walls to the equation there will be reflections off each of them, and all will arrive at the listening position at various degrees of phase. In general the worst case cancellation notch would be about 24dB deep, not that 24dB isn't serious.

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post #29 of 95 Old 07-05-2013, 12:21 PM
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My appologies to the OP is this is inappriate, but I figured my question fit with the discussion.

Like the OP, I also was unclear about the difference between the phase control and distance control.

I'm considering going from a single sub setup, currently located just behind the left speaker, and a multisub setup with one or two subs added near the prime LP. My processor has two sub outputs, but they share the same settings. Is it possible to properly set up the additional subs using their phase controls or do I also need to be able to adjust distance for each?

Thanks. smile.gif

PS - Please let me know if it would be more appropriate to start a new thread. redface.gif

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post #30 of 95 Old 07-05-2013, 12:34 PM
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My processor has two sub outputs, but they share the same settings. Is it possible to properly set up the additional subs using their phase controls or do I also need to be able to adjust distance for each?

Your AVR cannot calibrate two subs separately if they share the same distance/level setting. Two sub outs are similar to having one sub out and using a y-adapter to split the signal for 2 subs.

Anyway, why do you want to add another sub?

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