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RE: programs for testing speaker response

Posted by Paul Eizik (A) on May 18, 2016 at 10:52:36

In Reply to: programs for testing speaker response posted by floydandrews on May 17, 2016 at 11:50:52:

F.

I have used REW and it works quite well, but there was a learning curve going from the old school way of making freq. resp. graphs using the warble oscillator test tracks on the Stereophile Test CD, test mic with a VU meter and graph paper.

Good news: You can generate a lot of data very quickly on your laptop with REW.
Bad news: You can generate a lot of data very quickly etc.

Interpreting all the data is still the difficult part. It took me awhile to understand why the measurements were quite different between REW and my old graph paper data. The reason is largely due to the tendency of the warble oscillator and VU meter to average out and smooth the response. You will need to select an averaging option with the graph REW creates, and 6 dB per octave is a good start as Atkinson usually uses this in his frequency response graphs in Stereophile (when this is specified). Using no smoothing will provide a graph that looks like a field of grass with too much micro information. Using a high order of smoothing, like 24 dB per octave, will make the results unrealistically smooth (read: too good to be true). What you want to look for is a signature, or the lay of the forest rather than overly focusing on particular trees in it. I have obtained similar results to Atkinson's measurements when measuring the same speakers he has tested in Stereophile

Make a paper copy of the REW instructions as you'll need it while your laptop is running REW. Also there's a good instructional video on Youtube about using REW. The Home Theater Shack website (where you can download REW for free) is mainly concerned with measuring room response which can be addressed with active EQ, and not so much with what the speakers themselves are doing without what the room is adding.

A bit of history: Richard C. Heyser invented Time Delay Spectrometry which he used to test speakers in Audio magazine back in the day. The first TDS unit cost $30,000 to cobble together out of various computer and pieces of scientific equipment. Nowadays a functional facsimile program is a free download, but we're still scratching our heads about the data! Heyser saw similarities among the discrepancy between what we hear and the measurements we obtain, and similar discrepancies between measurement data in Quantum mechanics.

Good Luck!

Paul

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