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Old 27th May 2005, 02:00 AM   #1
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Default speaker measuement questions

So I finally got my Radio Shack dB meter, and Rives test CD and have started a little testing. I've certainly got some results already. However I noticed a bit of discrepancy between measureing the two different speakers (as much as 4-5dB difference), even with speaker and meter in exactly the same places. I then noticed that the meter can really change depending on where I'm standing. This obviously happens to a greater extent at higher frequencies, but it seems to be effected as low as 250Hz. Is there any one place that is best to stand in a situation like this? I try and stand diagonally back behind the meter so as not to stand directly behind or to the side. Also my "listening" room is pretty small and also serves as my kitchen, dinning room, living room,and chicken brooding house for a couple of weeks. In other words, a little clutered. Would I get better results if I took them out onto the back deck? I live in the country and it is ussually pretty quiet. Obviously this would remove any room gain, but would it also be more accurate in the upper octaves as well. Thanks in advance.
Joe
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Old 27th May 2005, 02:22 AM   #2
SY is offline SY  United States
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You're trying to do electron microscopy with the magnifying glass attached to your Swiss Army knife.

To do what you want to do, you need to make the small investment for a good sound card (if you don't already have one), an electret-based test mike, an easy-to-build test jig, and free software like Speaker Workshop. Figure a $200 budget and a few weekends getting it all hooked up and working. But you'll have a great and versatile tool.

Search "Speaker Workshop" on the forum and you'll have tons of info to start sifting through.
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Old 27th May 2005, 03:45 AM   #3
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Yeah, I thought about getting it all set up on my computer, but I ended up cheaping out. I'm running a Mac right now and I checked out Fuzz Measure, and mics and what not, but ended up cheaping out and getting the RS dB meter and test CD. So maybe I'll eventually have to break down and get a real measurement system, but for now I want to get the most out of what I have.
Joe
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Old 27th May 2005, 04:20 AM   #4
SY is offline SY  United States
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You can use the RS meter for near-field bass measurements. And you can get a rough idea of spectral balance by waving it around while you run warble tones.

But it's stone knives and bear skins. The proper tools don't cost much more than many decent woofers and less than quite a few more, so put it in perspective.
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Old 27th May 2005, 05:05 PM   #5
soongsc is offline soongsc  Taiwan
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When you're using just a meter and continouse sound, you also get reflections, standing waves, noise, etc. that cannot be filtered.
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Old 27th May 2005, 05:53 PM   #6
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Lacking an anechoic chamber, the old timers used to take the speaker outside, away from structures, and bury it in the ground, face up. Suspend your meter over it and play the CD test tones.
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Old 27th May 2005, 10:18 PM   #7
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Well, I guess I didn't make the best purchase ever with the dB meter, but what are ya going to do? I'll probably not bury my speakers, but I'll certainly take them outside, lay them down and see what I can come up with. Thanks for all the advice everyone.
Joe
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Old 28th May 2005, 01:52 AM   #8
soongsc is offline soongsc  Taiwan
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Hope it's not concrete ground.
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Old 28th May 2005, 02:06 AM   #9
SY is offline SY  United States
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Actually, concrete ground is a great way of doing it- the speaker is laid on its side and the mike is placed near the ground a couple of meters away. "Ground plane" is the jargon term.
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Old 28th May 2005, 02:17 AM   #10
bzdang is offline bzdang  Canada
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I think that I read somewhere that the RS spl meter has an output jack and can be used as a microphone.
?
If so, then get a cable and some software and go!
I use audiotester because I am able to make it work without overheating my brain.
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