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Author Topic: how important is the SPL meter when using RoomEQWizard  (Read 1682 times)

brett

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how important is the SPL meter when using RoomEQWizard
« on: November 20, 2008, 02:19:20 pm »

After not being able to get Room EQ Wizard working with my Mac Apogee drivers, I bought the needed cables to use the internal sound card of my mac or pc to do acoutic measurements. I have a behringer measurment mic. It looks like in the directions you also hook up an SPL meter to calibrate the mic input. But it sounds like it is an optional item. Am I missing somthing? Because there is a built in SPL meter in REW on the input. Can I just play the test tone and use the behringer mic into the REW SPL meter to do the calibration?
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andrebrito

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Re: how important is the SPL meter when using RoomEQWizard
« Reply #1 on: November 20, 2008, 07:00:46 pm »

No, you will need a sound level meter calibrator to have real SPL values.

But you can check the frequency response of the room, RT60 etc without the need of real SPL values.
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brett

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Re: how important is the SPL meter when using RoomEQWizard
« Reply #2 on: November 21, 2008, 05:27:45 pm »

it worked fine with my measuremnt mic and using the spl meter in REW to calibrate the mic. I had a huge null from 50-100 with a deep valley that peaked down at 70. another one at 250hz about 20 db deep and a small one at 850hz about 10db deep. Tried moving things around and reshot about 30 times. these nulls were consistant.  Over 1k The mids and top are within 6db
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andrebrito

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Re: how important is the SPL meter when using RoomEQWizard
« Reply #3 on: November 22, 2008, 05:55:58 am »

A type II sound level meter has a error of usually +/- 2 dB. A Type I SLM, which is quite expensive gives you much less error in the readings

Actually you need a calibrator for the SPL meter. These calibrators that are used in environmental acoustical measurements, where measuring Leq levels need to be as accurate as possible, are mandatory and both the calibrator and the SLM need to be check each year on a specific lab.

So this Radio Shack SLM don't show real SPL values, there might be an error of 2 dB, maybe 5 dB, maybe 10... who knows...

The good thing is that you don't need real SPL values for room frequency response, impulse response or RT60 measurements.

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franman

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Re: how important is the SPL meter when using RoomEQWizard
« Reply #4 on: November 23, 2008, 12:15:57 pm »

absolute value measurments are nice, and necessary for some types of issues as listed by Andre, but relative measurments are what we are most often talking about here... ie: +/- x dB over the range of frequency... Smaart, Fuzzmeasure, etc.. non of these 'require' calibration to make room response measurements.. FYI, we use TEF-20 and TEF-USB PRE for most of our room measurements and the interface is calibrated to your reference microphonse sensitivity. We use B&K and Earthworks test microphones. I have been experimenting with Fuzzmeasure as it provides some great test displays. It looks very interesting but I dread carrying any more hardware around (FW Interface) to a testing session.... I've also used Smaart for years, since it was JBL Smaart (ver 2)... great program. Goldline is working on a very similar 2-channel RTA package that will do Source Independant Measurements as we speak.... all very interesting.
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Chris Liscio

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Re: how important is the SPL meter when using RoomEQWizard
« Reply #5 on: November 23, 2008, 07:05:11 pm »

franman wrote on Sun, 23 November 2008 12:15

absolute value measurments are nice, and necessary for some types of issues as listed by Andre, but relative measurments are what we are most often talking about here... ie: +/- x dB over the range of frequency... Smaart, Fuzzmeasure, etc.. non of these 'require' calibration to make room response measurements.. FYI, we use TEF-20 and TEF-USB PRE for most of our room measurements and the interface is calibrated to your reference microphonse sensitivity. We use B&K and Earthworks test microphones. I have been experimenting with Fuzzmeasure as it provides some great test displays. It looks very interesting but I dread carrying any more hardware around (FW Interface) to a testing session.... I've also used Smaart for years, since it was JBL Smaart (ver 2)... great program. Goldline is working on a very similar 2-channel RTA package that will do Source Independant Measurements as we speak.... all very interesting.


You may be able to use FuzzMeasure with the TEF-USB PRE if it shows up on your Mac as a general USB audio device. I'm the developer of FuzzMeasure, and I'd be glad to talk to you offline (chris at supermegaultragroovy.com) to help you see if we could get things working together.

Chris
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