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Benchmark...first watt....ABX...facepalm!

Blumlein 88

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#81
I have a question, from a scientific perspective. The best testing would be using test equipment, but lacking such tests or equipment, why wouldn't it be "proper" to use a test frequency (or frequencies) as a listening test to evaluate an amplifier (or system)?

Scientific testing in many cases require a system to be broken into individual smaller systems to provide usable information. In this case a specific frequency test appears to be valid to evaluate the response of the amplifier over a specific (narrow) frequency range. It would seem the argument should be that many additional frequencies should be tested. When music is used, it would seem that evaluating individual frequencies....

Well evaluating the capabilities of something you want to have a margin or a safety factor. If I am stressing a beam I want to stress it with a little bit more than I think I will ever apply to it to see if it breaks. I want to flesh out the envelope of performance. In audio there may not be the safety issue, but you do want some margin beyond your requirements.

Despite what most people imagine, test tones can lay bare the limits of performance in ways music usually doesn't. One of the very toughest test tones is the twin tone IMD test. Two high frequency signals combined to maximum level. One can imagine having 20 tones instead of 2 would be more stressful, but that is not normally the case with amplifiers. One may wish to use a sweep or a series of spot tones to flesh out flatness of frequency response.

So if music is a lesser stressor test tones can give you a margin of performance. Do well on the test tones, and you don't even need to test it with music most of the time. Nor is this unusual in designing products. Many things are designed and tested in sensible ways that don't require use of the product as it will be used to confirm. Sometimes there are gotchas, but more often than not there are none.

As for the idea never have blind tests been done with test tones, well of course they have. People can detect marginally audible distortion at lower levels with tones than they can music. They can more readily detect and detect at smaller levels of difference frequency response differences in gear with pink or white noise. So if listening tests of tones are clean, and wideband noise are clean, you'll be able to use the gear for music knowing all is well. Wideband noise has all the frequencies all the time.
 

Wayne

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#82
As for the idea never have blind tests been done with test tones,
@Blumlein: Thank you, I think we are in agreement.

Just a comment concerning "blind tests." from a "scientific" perspective, a sighted (non-blind) test would not be objective, but subjective to individual biases. So IMHO, all listening tests must be double blind to be of maximum value and in addition, the higher the number of participants (n) the better.
 

RayDunzl

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#83
Wideband noise has all the frequencies all the time.
Wideband noise contains all frequencies within a range of bandwidth, with randomly changing amplitude for individual frequencies.

Here's about 50ms of some white noise, with an attempt to observe only the 5khz component within it:


upload_2017-9-18_18-7-20.png

This has high and low pass filters at 5khz applied multiple times, so the amplitude shown is meaningless, but the range of amplitude could be of interest.
 
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amirm

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#84
Why don't we see peer reviewed DBTs of people listening to test tones? I've never heard of such a thing.
They are done pretty routinely in research. Here is a Dolby paper for example on impact of jitter:

DolbyJitterStats.PNG


dolbyjitter.png


When they switched to testing music, they found that jitter was far, far less audible than in tones:

upload_2017-9-18_19-19-3.png



So test tones did provide a worst case scenario compared to music (as expected due to effects of masking).
 

Nightlord

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#85
Amps are used primarily for playback of music/drama signals, not test tones. The test conditions here are pathological. A real world test using music would have been more representative of how amps are actually used. They decided against this and for good reason.

So who cares if the amp can be distinguished by listening to a test tone? Do you listen to test tones?
If the music I listen to happen to be a tone only, then yes. But it's beside the point... if there's a test tougher than the usecase to use in designing, then the issues will be so much less in the actual use case.... I prefer having something 10x unhearable than 1x unhearable if I can choose... as it's not the only gear used and distortions may combine until hearable if the happen to match.

Any time it's distinguished, there's room for improvement.
 
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#86
They are done pretty routinely in research. Here is a Dolby paper for example on impact of jitter:

View attachment 8762

View attachment 8763

When they switched to testing music, they found that jitter was far, far less audible than in tones:

View attachment 8764


So test tones did provide a worst case scenario compared to music (as expected due to effects of masking).
Sorry, lack of communication on my part. I didn't mean to say that people don't listen to test tones in DBTs, but it came across that way. What I meant to say and failed to articulate is that people rarely perform DBT's of amplifiers and use test tones as a source. They use music as the source.

Virtually every amp or DAC or cable DBT that I've read about is done using music. If you fail to distinguish a difference using music (ie the intended usage), but succeed with a 1 kHz test tone, what useful information can be taken away from that exercise?
 
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RayDunzl

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#87
If you fail to distinguish a difference using music (ie the intended usage), but succeed with a 1 kHz test tone, what useful information can be taken away from that exercise?
That your ears are rather forgiving little devices when presented with complex information?

---

I know I like my Krell/MartinLogan setup at higher volume levels, where my little JBL LSR 308s have higher distortion (as measured with tones).

See https://audiosciencereview.com/forum/index.php?threads/jbl-lsr-308-in-the-house.1066/#post-28025

At more casual levels, where the harmonic distortion readings are lower, and I'm not staring blindly at the sweet spot, I can't say I prefer one over the other, and use the JBLs as my daily econo drivers now.
 
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