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Discussion Starter #1
Hey.

For some reason I am unable to measure above around 96db on my REW setup.

I have a ECM8000 and behringer USB card hooked up to a vista laptop. I use a little behringer mixer as phantom power.

When I tried, for fun, to read out some high SPL readings it seems my system insists it can only play to 96db....I get the clipping message.

How do you guys set your REW/other equipment, so you can read 110db+ etc?

I've been using REW for quite a while now, but just got a 2nd subwoofer so wanted to test my systems overall basoutput and was dissapointed to only get 96db from a maelstrom and LMS driver with 2 x 2000 watts!:rubeyes:

When viewing starwars II, the radioshack meters hits 105db+ during the startscene...so I know it can play loud!
 

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In my experience - it's just very hard to measure very high SPL levels (say 90/95+ like you're trying to do).

In fact, I believe that it's a challenge to record high SPL levels in general. It tends to overwhelm microphones. So, it's possible that very high levels may just be too much for the ECM8000.

Most people use REW for calibration and testing frequency response rather than testing with max SPL.

What are you trying to do exactly? Most people I've seen who are trying to measure peak SPLs just use a SPL meter than has a peak hold option (yours might, I'm not sure. I know a couple do).
 

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Discussion Starter #3
I was also going to test THD in my system and that seems to clip also.

I'll try some of the settings and ideas I got from reading as many posts about it as I could find.

Tomorrow I'll get the gear out and attempt to get some higher SPL readings somehow!:)
 

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I was also going to test THD in my system and that seems to clip also.
I'll try some of the settings and ideas I got from reading as many posts about it as I could find.
Tomorrow I'll get the gear out and attempt to get some higher SPL readings somehow!:)
I think with such high levels...... you'll probably get some distortion from the mic itself..

Let us know what you get from further testing.. :)
 

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You will be clipping either the mic preamp or the soundcard input. Remember that when setting up to make measurements the input to the soundcard is around -12 to -20 dB FS with a signal at around 75dB, which is to ensure that your measurement makes good use of the soundcard input range. If you look at the "Headroom" figure when making a measurement that shows you how much louder the measurement could get before it reaches the point of clipping the soundcard input. If you need to make high SPL measurement, go through the SPL meter calibration routine and adjust the input volume (or mic preamp gain) to ensure the input level at whatever calibration level you are using gives you enough headroom. For example, if you want to measure up to 105dB and you cal the meter with a 75dB signal, you need the input level to be no higher than -30 dB FS (75dB + 30dB = 105dB). When you cal the SPL meter in V5 it tells you the maximum SPL that can be measured with the current input volume setting.
 

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Discussion Starter #6
Thanks, I played around with it this morning.

I wasn't really able to get the THD measurements above 99.9db, but my radioshack said 110 at one point during a 40hz test tone.

I got around 100db at 20hz with under 5% THD, before when I measured it was 30%+! So something was wrong hehe.

Playing a 15hz testtone I stopped the test around 92db with around 10% THD.

25hz was 105db and 2.8% THD. I ended up using the radioshack as the REW didnt seem to get passed 99.9db, but the radioshack showed more. Before changing settings, the REW db numbers during the THD test was turning red around 93db and THD was through the roof!

Sub setup is new so I didnt feel like pushing it too hard. Excursion on either sub wasn't at x-max at all. Getting to know them still:)

Not very scientific, just wanted to show myself that my setup can atleast do [email protected] with low distortion!
 
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