Thanks for the link to what seems to be a great tool.

Dave

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http://www.libinst.com/Audio%20DiffMaker.htm

Excellent, thanks for posting that link. I've seen the program before, but forgot about it because I can easily do this manually.

--Ethan

I know a guy who uses that software.

His trouble with it is that every cable differs, even varying between the same model from the same maker.

Perhaps we can get accurate to the point where everything measures differently but sounds the same!

I also forgot about this. I've never played with it.

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Perhaps we can get accurate to the point where everything measures differently but sounds the same!

We were there 20 years ago. One device might measure -0.1 dB at 20 KHz and another isn't down to -0.1 dB until 40 KHz. Or one has distortion at 0.005 percent and the other is 0.01 percent. Or one D/A has jitter at -110 dB and another at -120 dB. We can easily measure those differences but they're all way too small to hear. Comb filtering my friend, comb filtering. That, and the frailty of human perception.

--Ethan

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We can easily measure those differences but they're all way too small to hear. Comb filtering my friend, comb filtering. That, and the frailty of human perception.

Anyone who has ever done in room measurements, pro or novice knows if you move a microphone just an inch or so you will get different frequency response readout. But Ethan, the same argument can be made that the actual differences one hears when moving ones head the max of 18" or so as I sit in my listening chair are too small to hear, so I hardly see how comb filtering can account for claims of heard differences in whatever! I wish you'd get over it already. Human frailty...OK!

RG

Using headphones disproves Ethan's claim that comb filtering accounts for most differences heard by audiophiles.

Dave

Quote:

Quote:

We can easily measure those differences but they're all way too small to hear. Comb filtering my friend, comb filtering. That, and the frailty of human perception.

Anyone who has ever done in room measurements, pro or novice knows if you move a microphone just an inch or so you will get different frequency response readout. But Ethan, the same argument can be made that the actual differences one hears when moving ones head the max of 18" or so as I sit in my listening chair are too small to hear, so I hardly see how comb filtering can account for claims of heard differences in whatever! I wish you'd get over it already. Human frailty...OK!

RG

I agree with Ethan up to a point. Also consider this:

1ms = 1foot

Quote:

...The audible effect of comb filtering is easy to experience using a
delay line. If you combine a signal with a delayed version, you will
experience various effects...

...Shorter delays have wider bandwidth notches and thus
remove more power than longer delays. This is why microsecond and
millisecond delays are so audible.

-- F. Alton Everest - Master Handbook of Acoustics Fourth ed.

Microsecond delays are audible? I'm still trying to get my head around that.

It would seem to suggest(to me anyway) that digital clock oscillation (Low-frequency correlated phase jitter) can also contribute to this effect. I envision it as the doppler effect rapidly shifting back and forth between red and blue causing a subtle smearing at high frequencies.

I don't know, maybe I had to much of that bomber that was going around awhile ago.

Quote:
the same argument can be made that the actual differences one hears when moving ones head the max of 18" or so as I sit in my listening chair are too small to hear, so I hardly see how comb filtering can account for claims of heard differences in whatever!

I'm sure the response changes drastically in your room over a distance of 18 inches, and the main culprit is nulls. The reason the sound doesn't change as much as a microphone response test shows is because each ear receives a different response. Nulls in one ear are not present in the other so you still hear those frequencies. But the different response in each ear accounts for the "subtle changes in imaging and clarity" you often hear reported after changing speaker wires and power cables.

Quote:
Human frailty...OK!

Yes, and that's the larger reason IMO.

--Ethan

Quote:
Using headphones disproves Ethan's claim that comb filtering accounts for most differences heard by audiophiles.

Headphones do indeed avoid the comb filtering, which then leaves frail perception, buyer's remorse, placebo effect, and wishful thinking. These are at least as important as comb filtering!

After I wrote my "Believe" article showing the effect of comb filtering, my genius friend Bill Eppler said I was being too kind to "audiophile believers" by giving them a legitimate reason to claim they hear differences in wire. He said the main reason for such beliefs is placebo effect and frail hearing, and I agree. But comb filtering is real too, and it explains why talented audiophiles who are not foolish suckers might really hear changes after swapping wires.

--Ethan

Quote:
1ms = 1foot

Yes, but that doesn't mean distances of one foot affect only frequencies higher than 1 kHz. The response at any given location in a room is the sum of the direct sound from the speakers plus many competing reflections. This is why even a few inches away the response can change quite a bit below 100 Hz and even lower.

--Ethan

Quote:

Quote:
1ms = 1foot

Yes, but that doesn't mean distances of one foot affect only frequencies higher than 1 kHz. The response at any given location in a room is the sum of the direct sound from the speakers plus many competing reflections. This is why even a few inches away the response can change quite a bit below 100 Hz and even lower.

--Ethan

Agreed.

This is the part I struggle with:

Quote:
Comb filtering my friend, comb filtering. That, and the frailty of human perception.
--Ethan

Comb filtering is a big problem. Probably one of the most difficult to tame. But I think phase problems also contribute and many can be solved electronically. For example; linear phase crossovers.

Phase distortion my friend, phase distortion.

http://www.dolby.com/uploadedFiles/zz-_S...sWhitePaper.pdf

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I think phase problems also contribute and many can be solved electronically. For example; linear phase crossovers.

Agreed, but that to me is a different issue, and is still the same core issue as comb filtering. Phase problems in a crossover manifest audibly as - you guessed it - peaks and nulls that occur when the output from two drivers combine acoustically in the air. This is not exactly comb filtering, but it's a first cousin. Phase shift alone is not audible in usual amounts, but the frequency response errors when signals combine are certainly audible.

--Ethan

Quote:

Headphones do indeed avoid the comb filtering, which then leaves frail perception, buyer's remorse, placebo effect, and wishful thinking. These are at least as important as comb filtering!

Luckily I wasn't subject to any of those at RMAF.

Dave