Measuring Frequency Response

[Wally]

I brought this up in my earlier post regarding freq response and flat energy response.

Those of you who have done your own freq res testing, what equipment do you use and how/where do you do this.

I'm assuming few of you have anechoic chambers.... LOL Any time I have done any measurements, the curves were wild and did not look anything like published curves and had huge peaks and valleys.

I have a couple of Radio Shack SPL meters and a Panasonic SPL meter with a warble tone frequency generator. Have HP and Heath Sine wave generators, pink and white noise generators, 10 and 31 band eq's and a couple of grahic eq displays but unfortunately they are only 10 band so inadequate for doing freq response. Is this stuff adequate to measure speaker freq response and do I measure close up...like 1 inch from the drivers or from 1 meter away as I have been doing and getting readings that don't correlate with published curves.

Is there computer software and hardware (reasonably priced) to generate sweep signals and display measured frequency response?

[kkantor]

There are many good cheap/free software tools available for measuring speakers. Almost none use sine sweeps, since this method is very prone to influence from the room. (There are mathematically equivalent processes.) They range from simple and user-friendly, such as:

www.trueaudio.com,

to fairly complex and sophisticated:

www.purebits.com

www.fesb.hr/~mateljan/arta/.

In addition, you will need a decent microphone, such as:

http://www.zzounds.com/item--BEHECM8000,

and a power supply/preamp/soundcard, such as:

http://www.zzounds.com/item--BEHECM8000.

All told, it is difficult to get meaningful data for less than $300 or $400. If you aren't concerned about some innaccuracy at the frequency extremes, you can try and run the RCA output of your RS meter into your soundcard, and use one of the software packages above. This will be cheap, but you will be at the mercy of the filters that are built into the RS and the your soundcard.

[Pete B]

http://www.classicspeakerpages.net/dc/dcbo...&mode=full#5456

http://www.classicspeakerpages.net/dc/dcbo...&mode=full#5359

Here's a link to another discussion about speakers and crossovers where we discuss inexpensive microphones, and free analysis/simulation software, these things are discussed on many message boards, see post #9 in that thread:

http://www.diyaudio.com/forums/showthread.php?threadid=51514

Pete B.

Wallin links that work:

http://mysite.verizon.net/tammie_eric/audio/SW/SW.html

http://www.vikash.info/audio/sw_jig/measurements.asp

[Wally]

Thanks very much Pete and Ken.

I have checked out those sites and downloaded the freeware software and will play with that. If I get at all serious I'll spend some money on one of the commercial programs.

I just want to do some basic measurements that will tell me that speakers are working reasonably within say a 3db range across their effective range.

Measurement technology has come a long way since the 60's and 70's.

I find it interesting that a lot of expensive highly magazine rated speakers and some electronic components don't publish specifications and even more astounding, to me, is that the golden eared reviewers don't do any measurements of frequency response, noise, distortion etc. They claim their hearing is more accurate than any test equipment. They must have very linear and distortion sensitive ears!

Anyway, thanks much guys.

[Pete B]

Keele's papers online:

http://www.dbkeele.com/papers.htm