Who can explain Phase to me? (1 Viewer)

Anthony_I · Oct 24, 2003

I still have no real idea what phase is, how it changes hte sound or why. and anything ive found on the net has either been not clear enough or simply far far too technical for me to understand.

So what is phase and how does it work/what does it do?

GrahamT · Oct 24, 2003

Phase is like the polarity, hope this helps

If the speakers are out of phase (polarity), one will move in, while the other moves out. The displaced air from one is sorta cancelled out by the other moving in at low frequencies. It is kind of like one speaker in free air. It will produce almost no bass.

Anthony_I · Oct 24, 2003

so what does adjusting the phase on my amp do?

I mean i understand it as far as moving in/out goes.... but thats about it, and your explination actually told me a little more than i already knew.

But im talking about my subwoofer, a single speaker with a continusly adjustable phase.

Wayne A. Pflughaupt · Oct 24, 2003

Phase is like the polarity...

Mmm... nope. Polarity and phase are not the same thing.

Phase has to do with time alignment – i.e., the sound waves from various sources arriving to the ear at different times.

For instance, in most of the speakers we use the woofer cone is deeper than the tweeter. Thus the woofer’s point source is behind the tweeter, which means the sound from the tweeter will reach the ear a few milliseconds before the sound of the woofer. While the effects of this may not be readily apparent, some manufactures go to some lengths to make their speakers phase coherent – that is, the smaller drivers are slightly recessed to align them with the larger drivers, to make sure the overall output is time-aligned.

Home theater has some built-in time alignment problems with the popular outboard sub, which is typically some distance away from the main L/R speakers. This is why subs have phase controls, to help restore time alignment. Obviously, a continuously variable phase control is much more useful than one with fixed settings. But even then, the best you can hope to do generally is align the sub with only one of the speakers.

The sub’s crossover also electronically introduces phase issues as well, but that’s a discussion for another day. However, a continuously-variable phase control can help compensate for that, too.

By the way, ever notice how when you move closer to one speaker, it seems to get louder that the other? What most people don’t know is that this has to do with time alignment, not proximity. If you electronically delay the signal from the closer speaker so that it is time-aligned with the other one, they will both sound like the same volume again!

Regards,
Wayne A. Pflughaupt

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GrahamT · Oct 24, 2003

I understand. I just meant that if he reversed the polarity of one of the two speakers that they would be out of phase with each other. I thought that this was his question. Sorry if I wasn't clear.

Anthony_I · Oct 24, 2003

That makes a little more sense.

I guess i would hear a difference more if i had speakers other than a sub and some VERY VERY VERY VERY horrible mains (im actually using 2 "surround" speakers from a mini stereo system. simply to get some treble, until i got money to get my mains)

Ted Lee · Oct 24, 2003

some manufactures go to some lengths to make their speakers phase coherent – that is, the smaller drivers are slightly recessed to align them with the larger drivers, to make sure the overall output is time-aligned.

a really good example of this is the kef uni-q speakers.

take a look at the tweeter - it's actually "recessed" into the woofer cone. this allows for both point sourcing (all the sound is coming from the same "spot") and time-alignment (since the tweeter is slightly recessed).

you'll see other speaker brands where the tweeter is put "behind" the front plane of the speaker. or, they'll tilt the speaker slightly..in effect pushing the tweeter back just a touch.

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John Garcia · Oct 24, 2003

I auditioned the Q1s with some very nice gear, and I was not impressed. My friend has some Q5s and they sounded pretty good, in a less than optimum room, so I was surprised that the Q1s did not hold up. The Q1s had depth and imaging, but no "life" to them.

The crossover can also be used to "align" the phase of the drivers.

Ted Lee · Oct 24, 2003

oh...i actually agree with you john. i had some older uni-q's that were floor-standing (can't remember model number). they sounded much better than the bookshelf model.

i was just using that link as an addendum to explain wayne's post.

Allan Jayne · Oct 26, 2003

Speaker phasing is most important for bass, and in this context polarity and phase go hand in hand. So long as all the speakers are connected the same way, for example red or plus terminal on the amp to red or plus terminal on the speaker, the system should be properly phased.

For middle range and treble, the phase of the sound waves as they reach your ears can vary depending on where you are sitting in the room. Because this is a very complex acoustical topic, I do not think that setting back the tweeter in the speaker cabinet to make it sonically in phase with the woofer has any importance.

Speakers in general do not have flat frequency response. Also, resonances in the room will alter the frequency response as you hear it. Even your ear may be more sensitive to certain frequencies than others. Therefore to you certain speakers may sound much better than others and other folks may disagree. I believe that these differences are much greater than any time matching or phasing of the mid range or tweeter speakers could possibly accomplish.

If you have a different brand amp for your rear speakers versus your front speakers, it is possible that the audio arriving at the speaker terminals of one amp is partially out of phase so that connecting the speakers all with the same polarity does not work well for bass.

Video hints:
http://members.aol.com/ajaynejr/video.htm

John Garcia · Oct 26, 2003

I do not think that setting back the tweeter in the speaker cabinet to make it sonically in phase with the woofer has any importance.

I completely disagree with this. Phasing between the midrange and tweeter can be one of the most important aspects of a speaker's design. Phase compensation done by the correct relationship of the tweeter to the midrange to create a seemless blend, and doing this without playing crossover tricks for phase, makes for a better sounding speaker, IMO. A less complicated x-over alters the signal less. This has to do not only with the phase of the drivers, but specific frequency merging. This is far more common on speakers intended for music use than HT and the majority of big name mass market speakers.

Thiel is a very good example of some amazing speakers that are designed this way.

Click to expand...

Ted Lee · Oct 26, 2003

b&w are another good example of time alignment considerations. take a look at this link.

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