speaker measurement questions

Josephjcole · 27th May 2005, 01:00 AM

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

SY · 27th May 2005, 01:22 AM

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.

Josephjcole · 27th May 2005, 02:45 AM

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

SY · 27th May 2005, 03:20 AM

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.

soongsc · 27th May 2005, 04:05 PM

When you're using just a meter and continouse sound, you also get reflections, standing waves, noise, etc. that cannot be filtered.

Bill Fitzpatrick · 27th May 2005, 04:53 PM

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.

Josephjcole · 27th May 2005, 09:18 PM

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

soongsc · 28th May 2005, 12:52 AM

Hope it's not concrete ground.

SY · 28th May 2005, 01:06 AM

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.

bzdang · 28th May 2005, 01:17 AM

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.

27th May 2005, 01:00 AM	#1
Josephjcole diyAudio Member Join Date: Jun 2004 Location: Wisconsin	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

27th May 2005, 01:22 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	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. __________________ If there's a sucker born every minute, where do the rest of them come from?

27th May 2005, 03:20 AM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	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. __________________ If there's a sucker born every minute, where do the rest of them come from?

27th May 2005, 04:05 PM	#5
soongsc diyAudio Member Join Date: Mar 2005 Location: Taiwan	When you're using just a meter and continouse sound, you also get reflections, standing waves, noise, etc. that cannot be filtered. __________________ Hear the real thing!

28th May 2005, 12:52 AM	#8
soongsc diyAudio Member Join Date: Mar 2005 Location: Taiwan	Hope it's not concrete ground. __________________ Hear the real thing!


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27th May 2005, 02:45 AM	#3
Josephjcole diyAudio Member Join Date: Jun 2004 Location: Wisconsin	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

27th May 2005, 04:53 PM	#6
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	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.

27th May 2005, 09:18 PM	#7
Josephjcole diyAudio Member Join Date: Jun 2004 Location: Wisconsin	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

28th May 2005, 01:06 AM	#9
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	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. __________________ If there's a sucker born every minute, where do the rest of them come from?

28th May 2005, 01:17 AM	#10
bzdang diyAudio Member Join Date: Apr 2004 Location: Pickering, Ontario	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. __________________ Benford's law of controversy - Passion is inversely proportional to the amount of real information available.

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