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Should we pay more attention to delays in sound?

https://www.aalto.fi/en/news/the-human-ear-detects-half-a-millisecond-delay-in-sound
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mijostyn's avatar
mijostyn
8,225 posts
 
millercarbon, you need to make up your mind. In regard to subwoofers you have stated that "time does not matter." 

When it comes to crossovers it matters a lot. Group delays can be caused by positional factors and electronic factors. You can adjust any set of group delays to be exactly the same. This can be done by moving the slow drivers towards the listener or digitally delaying the early drivers to match the late ones. 1 ms = 1 foot (at sea level). I can usually tell something is wrong by 0.2 ms at low frequencies but have never blinded myself to this so it could be longer. I can tell the difference in bass impact but I am the one adjusting the delay. Of course I set them all to zero.
The vast majority of audiophiles do not have this capability which IMHO is a shame. It is vital for proper subwoofer management and imaging in general. It is the difference of hearing one vs two voices. 
millercarbon's avatar
millercarbon
12,531 posts
 
I waited a couple weeks to get my Herron, almost two months to get my Moabs, and now waiting on DHL to deliver my Origin Live Sovereign turntable. Oldhvymec waited even longer on his Decware ZP-3. And that is nothing, after saving for more than a year for a Raven Reflection when finally ready to order was told it will be more than a year! So yes someone somewhere definitely needs to pay more attention to delays in sound!
ditusa's avatar
ditusa
1,738 posts
 
What mijostyn said about group delays and time delays is correct. It was discovered in the 1930's, by MGM studio.

Below article from The Klipsch Audio Community:

This entire thing goes back to the Eleanor Powell "double tap" incident at MGM studios in the early 1930s. When monitoring playback of Powell tapdancing an echo was noticed on the taps. John Hilliard, subsequently the greatest of all horn designers, was a young sound engineer at MGM and traced the problem to the 8 foot difference in the path lengths of the horns in the 2-way Western Electric monitor speaker.

Hilliard did experiments that showed that the effect was time and frequency dependent and that a delay of less than 3 milliseconds (about 3 feet) was inaudible using crossovers between 350 to 800hz.

A result of this incident and WE's refusal to market their improved Fletcher loudspeaker was the decision of MGM sound honcho Douglas Shearer for MGM to design their own improved system which would among other things minimize time delay. Hilliard was put in charge of the project which then developed the famous Shearer Horn. An entire galaxy of talent worked on this system including Hilliard, James Lansing, Bob Stephens and even RCA's Harry Olson.

Note that though the folded bass horn of the Shearer cut time delay compared to the WE snail horns it didn't eliminate it totally but Hilliard's later Altec Voice of the Theatre did. So it seems that even though Hilliard thought some delay was inaudible the existence of any at all still nagged at him.

Which brings us back to the present day. Is the time offset of the big Ks a problem? Theoretically the distance falls under the distance Hilliard thinks was undetectable. Might it still be a problem? Perhaps. But keep in mind that all loudspeaker designs make compromises, given a choice, as PWK was with his design, between lower distortion and time delay which would you choose? I'd take the lower distortion of the horn system.

Photo of Shearer Horn from Lansing Heritage site

 https://www.tnt-audio.com/casse/altec_a7_clones2_e.html
bifwynne
2,206 posts
 
Isn't this thread really talking about a speaker design issue that is inherent in most if not all speakers: namely time coherence.  A couple of manufacturers address this issue by careful placement of the drivers and using first order crossovers. For example, .... Thiel, Vandersteen and Green Mountain audio.  

The late, great Roy Johnson of Green Mountain audio wrote some pretty impressive white papers on the subject.  Not sure if Roy's white papers are still available.

And DEQX sells a digital device that can correct for time delays in speakers.  I used to own a DEQX. The unit was inserted between my preamp and amp.  Although the DEQX added quite a bit to the SQ, I found, on balance, that there was a net subtraction because the DEQX added a lot of processing and manipulation to the signal. 

If there were more brick and mortar stores around that carried a lot more speakers brands, I would love to spend some time educating my ears to learn just how much better time coherent speakers sound as compared to those which are not time coherent.  John Rutan at Audio Connection, located in Verona, NJ, is a Vandy dealer and stalwart.  Perhaps John would let me burn some time one day in his shop.  

BIF      
jdbsi
35 posts
 
There is also Enhanced Bass Alignment (EBA) developed by Meridian to address group delay.
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