Why Some Audiophiles Fear Measurements

[Orb]

Originally Posted by Ethan Winer
There are four parameters that affect audio reproduction:

Frequency response
Distortion
Noise
Time-based errors

Do you also have a similar set of parameters to measure rooms? Something we will look at and say immediately "My room sounds excellent!" without listening?

To be fair professional room modelling software and acoustic articles suggest the answer is yes with the right parameters-test-measurements, if you can also measure the boundary characteristic (reflections-absorption characteristic/etc) as well.
However I know next to nothing on this subject.

Cheers
Orb

 

[Ethan Winer]

I dislike quoting someone's lengthy post and break it down with each debate point back.

LOL, that's my favorite way to have a dialog because then it's perfectly clear what is being said and replied to.

Can you expand on the IMD and show me anyone who has done that test-measurement as a full measurement test where it is not low.

I don't have typical specs for THD versus IMD in front of me. They generally go together, so a circuit that has high THD will likely have high IMD too. But I can imagine circuits where THD is low but IMD is high enough to be audible. Years ago I accidentally designed such a circuit. Really, my main point is that the idea that two devices can "measure the same yet sound different" is fundamentally flawed. If they measure the same but truly sound different, as proven in a blind test, then the wrong things are being measured.

--Ethan

 

[Ethan Winer]

I can not stop from asking if it is so simple why all the others kept us waiting so long, telling us that we need experts to analyse rooms ...

I agree. With luck, there will soon be a letter from me printed in a major audio magazine taking them to task for suggesting that people need to spend $5k and up to hire an expert to visit in person. I help people all the time for free in forums, and paying customers get detailed advice for free with placement drawings etc if needed. You don't even need to measure anything to make a big improvement. For a professional recording or mastering studio, or someone rich enough to pay a consultant with their pocket change, sure, hire a pro to visit in person. But just adding bass traps and reflection absorbers at key places will make a huge improvement.

--Ethan

 

[Orb]

LOL, that's my favorite way to have a dialog because then it's perfectly clear what is being said and replied to.



I don't have typical specs for THD versus IMD in front of me. They generally go together, so a circuit that has high THD will likely have high IMD too. But I can imagine circuits where THD is low but IMD is high enough to be audible. Really, my main point is that the idea that two devices can "measure the same yet sound different" is fundamentally flawed. If they measure the same but truly sound different, as proven in a blind test, then the wrong things are being measured.

--Ethan

hehe yeah as I say sorry about not doing a quote breakdown.
Where you say

Really, my main point is that the idea that two devices can "measure the same yet sound different" is fundamentally flawed. If they measure the same but truly sound different, as proven in a blind test, then the wrong things are being measured.

This is the crux of my debate in response to you, because I am trying to reach a conclusion where it is highlighted there is a flaw somewhere in what is being presented as a hypothesis by both of us
The flaw in your case that if the FR and distortions are marginally different (below audibility) and yet multiple reviewers come back with similar perception parameters (similar in the more to FR opinion-article I linked) showing there are audible difference.
The flaw in my case that it is quite plausible there has been DBT ABX showing no difference in the context we are debating between such products ( I tend to wonder if the right tests are being done to focus on this but I agree that it should be measurable), but then thats a minefield for a totally different thread, thankfully we can focus on your hypothesis in this one

Cheers
Orb

 

[FrantzM]

BTW the way I have measured the in room frequency response form the listening position in my room using a spectrum analyzer on real music It is reasonably flat with the expected roll off in the bass you would expect for the ML/CLS.

That has to be a typo .. How did you perform this??? ... "on real music"? I?????

 

[Ethan Winer]

The flaw in your case that if the FR and distortions are marginally different (below audibility) and yet multiple reviewers come back with similar perception parameters (similar in the more to FR opinion-article I linked) showing there are audible difference.

That's why I said early on that I freely dismiss sighted subjective reviews. They are all but worthless, especially any review that includes the word "palpable." Now, if you show me some reviews where the reviewer compared one product with another while blind, and there were enough back and forth switches to state clearly a meaningful difference, that'd be a different story. I've read a lot of hi-fi reviews in my 60+ years, and I can't recall even one that was done like that.

--Ethan

 

[Gregadd]

Now there's a logical flaw if I ever saw one. Who said that one's allocation of funds should follow the same proportions as importance to sound quality?

--Ethan

It is near impossible to sustain in its current form and anything you tranform it into.

 

[Gregadd]

That has to be a typo .. How did you perform this??? ... "on real music"? I?????

Real music as a opposed to just test tones. Is that the best argument you can come up with?

I don't measure I'm subject to ridicule. I measure and I am subject to ridicule. It is my mistake for taking you guys seriously. I use this device which comes with test cd and is used at live concerts by professionals to check among other things frequency response. It cost around between 300 to 500 dollars so I could afford it. It is also easy for the lay person to use.

 

[Gregadd]

The one I own.

 

[Ethan Winer]

Real music as a opposed to just test tones. Is that the best argument you can come up with?

But what sort of graph do you get measuring music? How do you relate that to anything useful given that music constantly changes?

I use this device which comes with test cd and is used at live concerts by professionals to check among other things frequency response.

That's great for large venues, but third-octave resolution is not useful for bass frequencies in domestic size rooms. An RTA also shows only raw response, but not individual reflections or modal ringing which are just as damaging as a skewed response. A much better choice for home use is REW (Windows, free) or Fuzzmeasure (Macs, $150). Both of those programs use a sweep tone where the level stays constant as the frequency sweeps. And both are described in the Room Measurement series in my own forum section.

BTW, I don't ridicule anyone for measuring or for not measuring. Heck, I never ridicule anyone at all unless they ridicule me first. Or call me wrong but fail to say why I'm wrong and what is right. Personally, I'm pleased that you have a measuring tool!

--Ethan

 

[kareface]

I have a spectrum analyzer too, I think the problem people have with it is it provides no benefit to using it when listening to music, lol.

Edit: Damn you ethan! You beat me out.

 

[DonH50]

On THD vs. IMD: There is a relatively simple mathematical relationship that relates the two. It does take some effort using some algebra and trig identities to derive, however. Rather than delve into that here, I'll just provide a couple of examples for two equal-amplitude tones:

2nd-order IMD (dB) = 2nd-order HD (dB) + 6.021 dB
3rd-order IMD (dB) = 3rd-order HD (dB) + 9.542 dB

That is, IMD is worse by 6 dB/9.5 dB than the 2/3-order HD term. With a lot of conditions thrown in, natch, but hopefully this gives you the idea for an "ideal" system.

FWIW - Don

 

[FrantzM]

There were no ridicule implied you stated something that I thought is not correct. I honestly wondered. It's now confirmed your statement was incorrect.

 

[Ethan Winer]

IMD is worse by 6 dB/9.5 dB than the 2/3-order HD term.

Awesome, thanks for that Don! I'm not a math guy, but this matches my empirical experience when I did circuit design stuff years ago.

So this is yet more evidence that specs giving only THD are incomplete, especially when said incomplete specs are used to suggest that two devices can measure the same yet sound different.

--Ethan

 

[Gregadd]

Ethan I guess that's where we part company. I think you have to show me where you are right. You have not done it yet. I guess we are just on diufferent paths. this is doing nothing but causing me aggravation.

I think personaly it's time to close this thread.

 

[kareface]

I'm still curious what use a spectrum analyzer is when listening to music.

 

[Old Listener]

... this is doing nothing but causing me aggravation.

I think personaly it's time to close this thread.

You might just stop posting to the thread. Others may have something to say.

Bill

 

[Randall Smith]

You might just stop posting to the thread. Others may have something to say.

Bill

I agree

 

[cjfrbw]

I don't get involved much in these thankless types of threads. Reminiscent of the AVS days. However, it has been fun watching Greg take it in the chin and keep on ticking. He reminds me of Jet Li at the end of "The One,", or maybe one of those guys getting mobbed by zombies.

 

[Ethan Winer]

I think you have to show me where you are right. You have not done it yet.

I have shown an awful lot over these pages! If there's something you don't follow, tell me what parts you don't understand and I'll try again.

this is doing nothing but causing me aggravation. I think personaly it's time to close this thread.

So a productive and educational thread should be closed because you can't understand our explanations? I have to agree with Bill. If participating causes you aggravation, perhaps it is you who should stop posting. I'm being as nice as possible in saying this because I'd much prefer to help you understand, rather than alienate you and have accomplished nothing.

--Ethan