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arnyk

Re: True RTA and VA analyzer software
« Reply #20 on: October 19, 2016, 09:37:17 PM »
You are the master of stuffing false claims ...
If by that you mean that I frequently  stuff false claims into the waste heap, then thank you!

 
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I mentioned Sam Berkow in another post. Do you know who he is?

The Sam Berkow I know of is a principle of SIA Acoustics. 


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Sure, you can find articles supporting pretty much anything. Does RTA provide useful information? Yes, if the user understands what he's getting.

Thank you for correcting your previous statement which was unfortunately stated in an entirely global way.  As a global truth, it fails. With suitable qualifications which were absent, it does not.

I am unaware of an acoustics analysis program that does not depend on the user understanding what he is getting.

Do you know of one?


« Last Edit: October 19, 2016, 10:26:16 PM by arnyk »


arnyk

Re: True RTA and VA analyzer software
« Reply #21 on: October 19, 2016, 10:23:10 PM »
Then why do the guys like Sam Berkow use dual-channel transfer-function measurement systems, which absolutely give phase information, when setting up studios and performance spaces?

I don't know how or why Sam Berkow does what he does, so the mention of his name is gratuitous and potentially misleading. In the spirit of trying to be helpful, I'll ignore it.  Note that his name does not appear here: http://www.aes.org/awards/ which will be explained shortly.

I've been tuning rooms and speakers and doing other acoustic measurements for at over 40 years .  I've learned a lot on the subject from well known internationally recognized authorities  including   Dr. Earl Geddes and David Clark  (both AES Fellows and lifelong close friends and in one case for a  time a business associate) and I have followed their leadership in terms of best practices for audio engineering including these areas. 

There is in fact an active audio engineering community in my home town Detroit, based on what is now called Automotive Infotainment. It  includes quite a bit of acoustical measurement experience and expertise, and many of these people are my friends and associates.

All  two-channel programs are not the same. For example True RTA operating in swept mode is a two-channel program, but there appear to be significant differences between it and say, Room Eq Wizard and Holme Impulse.  In particular they have different (from each other and True RTA) post-processing features that True RTA seems to lack the equivalent of. 

BTW Holme Impulse has fractional octave noise (and other signal)  measurement features that may eliminate the need to buy a RTA-type program.

Just because a program provides a result, does not mean that particular result is required for every use of that program. So the statement  "Then why do the guys like Sam Berkow use dual-channel transfer-function measurement systems, which absolutely give phase information, when setting up studios and performance spaces?" proves nothing.

I suspect that they use the analysis tools they use because they give the results they need. But the programs give many other results that are not needed for the specific purpose and are ignored. Phase angle can easily be one of these things. It is all about the right tool for the job.

I have explained why phase measurments in a real world room can be misleading. I have explained how to tune rooms and speakers without actually performing phase measurements and illustrated it with a real world practical example.  IME most people such as myself  who have actually done this kind of work know  how to tune a room or a speaker without always getting involved with the complexities of phase measurements.

Phase measurements can be very helpful to look at while designing crossovers, for example.

http://www.gedlee.com/downloads/directivity.pdf descrbes some fairly recent work that Dr. Geddes obviously finds to be useful for the purpose of evaluating speakers and their performance in rooms. Please note that while there are measurements in the paper quantified in degrees, the degrees refer to physical geometric angles and not electrical or acoustic phase angles at all.

Since I have on occasion assisted  him with these measurements, I know for sure that  that Dr. Geddes does these tests with several acoustical measurement tools including Holme Impulse. Obviously, he is not referring to that program's phase angle measurement facilities in these tests.

I'm not knocking phase measurements.  I've used them myself but for other purposes.  I wouldn't use them to look for peaks and dips in a room's response to a speaker because the amplitude variations are very obvious and useful.  It is no coincidence that Sia brochure http://static1.1.sqspcdn.com/static/f/487725/27268815/1475159945297/SIA_Brochure_2016.pdf  contains a number of amplitude plots, but  seems to have no phase plots.

audiomixer

Re: True RTA and VA analyzer software
« Reply #22 on: October 20, 2016, 04:00:40 AM »
this is getting weird....

I do know sam - the company I work for had had a long relationship with him and with smaart - and some of his portfolio pictures come from work we have been involved with or actually designed. 
that aside I would not assume I could say with authority how sam measures a room!
both methods have their merrit, and may be used to achieve good results if adequatly used. smaart does perform a transfer function from any noise source, revealing phase if you are inclined to check it. actually that was it's major feature in my opinion.

cheers - michael