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Old 23rd November 2009, 11:19 PM   #1
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Default Software to tune up and measure subs?

Hi all. I could not find any good threads on how to measure the response of subs. The threads on this forum seem to be geared toward full-range measurement, which may or may not work down low. The reason I come to this conclusion.. is that I have a Radio Shack analog SPL meter, which seems to do fine at full-range, but can't pick up lows for anything. I was trying it out in my car earlier, where I've probably got 120db worth of LF power, but it barely sees 100db. The only thing I can do to make it read 110db is to get some highs going concurrently.. and I'm quite certain I've got well in excess of 110db in my car. The only time I've found this thing to be "accurate" is when looking directly into one of my JBL 2480-series horns and seeing 125ish db when running 20 watts.

I've read about the preferred test apparatus of those on this forum - half-space or grass, no obstructions for 50 feet, etc. But I haven't seen anything about measurement devices or software. Recommendations are appreciated
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Old 23rd November 2009, 11:29 PM   #2
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I use:

Modified RS meter (Eric Wallin's Mods, remote Panasonic mic capsule)
E-Mu UCA-202 USB Sound Card
My old Dell laptop
and RoomEQ Wizard (free @ hometheatershack.com)

for most of my sub measurements. I also use some other programs, but not as often as I use RoomEQ Wizard.

I think I wrote up a more detailed explanation of how I measure things on DIYaudio some time ago.

Edit:

Here is a link:
LIVE SOUND Specific Tapped Horn thread...

Here is another:
Shopping list for RTA

Last edited by littlemike; 23rd November 2009 at 11:43 PM. Reason: Found my links...
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Old 24th November 2009, 01:26 PM   #3
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Thanks. What about a program to generate specific tones, as to avoid breaking out a precision generator?
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Old 24th November 2009, 05:53 PM   #4
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Quote:
Originally Posted by letsbangout View Post
Thanks. What about a program to generate specific tones, as to avoid breaking out a precision generator?
Play with the software I suggested. Specific tones can be generated with RoomEQ Wizard, Praxis, or FreqResPlot, as well as dozens of other programs. RoomEQ Wizard, Praxis, and FreqResPlot all generate and measure the tones for you, I know that REW and FRP use a swept sine measurement.

This is just how I do it, I am sure that there are other, better methods.
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Old 24th November 2009, 06:30 PM   #5
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you can spend thousands on this stuff if you got into the heavy analysis ones like TEF/TDS, MLSSA or SMAART.

What separates the men from the boys in sound system analysis regards ignorance of reflections through a technique called windowing. IOW, how to get an anechoic result while in reverberant (real) space. Software like TrueRTA are power response systems and measure total energy -- direct combined with reverberant. IOW, the peak you see @ 160Hz is being caused by the wall 6 feet away. At least, as far as I'm aware, their swept sine doesn't follow with measured filtering to ignore the non-direct contribution.

The Behringer ECM8000, for as cheap as it is, is well regarded as a good reference microphone. REW can even load correction plots for it and the radshack meter.

Sorry for being a bit off-topic.
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Old 24th November 2009, 06:48 PM   #6
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+1 for Room Eq Wizard.

I use my laptop built in mic for measurements. No extra equipment necessary. My laptop works great. Yours might not...

If I need to measure a speaker (or sub) response alone, I measure outside when possible. If I need to know what response looks like at the listening position, I measure ungated from the listening position. I don't see any need for gating.

Here's a link to the projects page on my new website. http://sites.google.com/site/amateuraudio/projects-1 There are several project pages showing the finished project, predicted simulations and measured response. If you look around these project pages a bit you will see that my measurements match predicted response quite well. (Only about half the project pages are complete with measurements so far)

It's not the most accurate measurement system money can buy but it does just fine for what I use it for.

Last edited by just a guy; 24th November 2009 at 06:55 PM.
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