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A Question About Time Alignment

I was reading a review of the Wilson Alex V on Stereophile recently. (Published just in time. I’m thinking about picking up a pair. Maybe a couple for the bedroom, too.) And it raised a long-standing question of mine, one that I hope the wiser minds on this site can answer. 
 

Wilson’s big selling point is aligning the different frequencies so they all reach your ear simultaneously. As I understand it, that’s why they have minute adjustments among the various drivers. The woofers put out bass notes that move slowly thanks to their long sound waves while the tweeters are playing faster moving, high frequency notes with short waves. Wilson lets you make adjustments so that they all arrive at the ear at once. 
 

It seems to me, however, that live music isn’t time aligned. Suppose I’m playing the piano and you’re sitting across the room. When I stretch out my left hand to hit the low notes, those notes travel along the same long, slow wavelengths as the notes from Wilson’s woofers. Similarly, the treble notes I play with my right hand move quickly through the short wavelengths. The notes from the piano are naturally out of alignment. If Wilson’s goal is to achieve a lifelike sound, aligning the frequencies doesn’t seem like the way to do it. 
 

Wilson has been selling lots of zillion dollar speakers for lots of years and people continue to gobble ‘em up. Something must be wrong with my line of reasoning. Would someone please point out where I’ve gone wrong? Nicely?

paul6001
holmz's avatar
holmz
2,328 posts
 

The time it takes for the low notes to arrive at your ears is slower than the highs no t because they are inherently long but because the voice coil of the woofer is mounted behind the baffle whereas for the tweeter it is mounted almost about the same level as the baffle hence the tweeter is closer to yours ears than the woofer.

 

Maybe instead of “slower”, do you mean “delayed”?

The former is speed/velocity, and later seems more like time/distance.

kenjit
1,771 posts
 

in colloquial speech fast or slow refers to time. For example fast food refers to food that is prepared quickly. There is no mention of distance in that.

nrenter's avatar
nrenter
765 posts
 

There is so many partial truths and misinformation in this thread about time and phase aligned speakers. I strongly suggest digging through past threads here on AudioGon on the subject. 

timlub
2,039 posts
 

I have read through this thread over the past few days and have purposely stayed out.  There are some reasonable explanations in this thread and others that don't show a real understanding of time & phase..... I will try to provide an accurate and very simple explanation.   

Over all time alignment is addressed.  All frequencies travel at the same speed,  Just because one frequencies wave length is longer, does not mean that the frontal wave of one frequency will reach you at a different time as another.  

On speaker design what we align is the portion of each driver where the sound is emitted, which is normally, aligning the front of each voice coil.  This allows all drivers sound to reach the ear at the same time. .... drivers can be staggered or sloped.   

Phasing.... fairly simple actually.... If it were possible to have a PERFECTLY phased speaker, which does not exist, 2 way, 3 way 4 way does not matter.  In each of these speakers, perfect phasing means all speakers cone movement would operate in unison.  This really cannot happen, so perfect phase cannot happen.  What we normally do is to get phase alignment at the crossover frequency.  When each driver is in phase at the crossover frequency, you normally get a quite good sound stage.  Each crossover type will cause some sort of phase shift, normally 60 to 180 degrees out of phase.  With alot of work, I have seen some drivers as close as 15 degrees of absolute phase with another, but normally achieving near phase alignment at the crossover point works very well. If you think about it in frequency, its fairly easy to understand why you cannot achieve absolute phase alignment. a tweeter may produce 3000 hz and up, well its obvious that the tweeter is moving at 3000 cycles per second, so a woofer moving at 60 cycles, obviously cannot produce sound waves in perfect unison.  Each driver does its job and we do the best that we can to produce time and phase alignment.  The better that alignment the better soundstage and imaging are produced.   If you think about it in the deepest sense,  Phase really is time, if drivers are out of phase with each other, frequencies are leaving the drivers at different times, thus effecting time alignment.  I hope this all makes sense and helps in some way.  Tim

 

kenjit
1,771 posts
 

Phase really is time, if drivers are out of phase with each other, frequencies are leaving the drivers at different times, thus effecting time alignment.  I hope this all makes sense and helps in some way.  Tim

No you are just confusing the issue even more. Phase and time are two different things. time cohesion implies phase cohesion but not vice versa. So not equivalent at all. Time coherence between two drivers is about aligning the start of the waves coming out of each driver. You can have phase aligned yet time non aligned. 

On speaker design what we align is the portion of each driver where the sound is emitted, which is normally, aligning the front of each voice coil.  This allows all drivers sound to reach the ear at the same time. .... drivers can be staggered or sloped.   

This is also nonsense. 90%  of speakers are not sloped or staggered and nobody is complaining. Time alignement has never been proven to be beneficial let alone audible it is only for marketing. 

I am very disappointed in you Tim. Was waiting for your custom tuned circuits and they never materialized.

~Master Kenjit, speaker tuner and master audiophile.

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