Anyone try a TermLab yet? - AVS | Home Theater Discussions And Reviews
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post #1 of 10 Old 03-05-2013, 06:24 PM - Thread Starter
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I was thinking of buying one, I want accurate SPL readings, I just don't trust my CM-140 and external condenser mic.

Similar to what this guy is doing. He is only running dual 12" SVS's and a RE-15 SX powered by a XTi-2k in a small room. (He said it was ~3kW.)


Here is what I get with 9 subs, powered with two XTI-4k's, one iTech 8000 and one EP4000, and two 1kW B&O monos (~21kW)


Something doesn't seem right. I'm running almost 10 times the gear.
At the time my EP4000 was fully clipping trying to power 6 of my 9 subs. (I've since added a second EP4000 and a Lab clone, bumping me up to ~35kW; but I haven't attempted a retest yet.)

Is it because my room was 3700cubic feet, and that other dudes was only like 800cuft. Could that be why the difference is so large, or is it the meter lying to me? eek.gif
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post #2 of 10 Old 03-05-2013, 06:33 PM
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No way in hell that guy is getting 142db with that gear.
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post #3 of 10 Old 03-05-2013, 06:43 PM
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I was in the upper 120s in my office/similar to that guys bedroom with 2 mal 21s and two amps. One plx3602 and one 2450. Don't remember exact numbers but with music it was 125-127 or so if remember correctly. No way your mic is right or room is just so big that is killing it. But at same time my theater is over 5000cuft and reading 140s so willing to bet your mic is off.
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post #4 of 10 Old 03-05-2013, 07:31 PM - Thread Starter
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Here's my clone doing 5-10-15hz. Seems to be making the power. No boost applied, just DCX HPF disabled and lots of gain.
Woofer is at xmech here on those 10hz pulses.


TermLab it is then wink.gif
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post #5 of 10 Old 03-05-2013, 07:47 PM
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notice where he placed the meter. i don't know what the precise number would be, but he has placed the microphone in the pressure zone for pretty much all the room modes.

just as placing a sub in a corner excites all the room modes, so it provides the most spl, it also works the other way around. the loudest point in the room is right in a corner.

nobody ever sticks his head where this guy stuck his microphone. <-- i suppose that says it all. :-)

his measurement is probably overstating normal in room spl by 20db or more.


Listen. It's All Good.
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post #6 of 10 Old 03-06-2013, 09:03 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

notice where he placed the meter. i don't know what the precise number would be, but he has placed the microphone in the pressure zone for pretty much all the room modes.

just as placing a sub in a corner excites all the room modes, so it provides the most spl, it also works the other way around. the loudest point in the room is right in a corner.

nobody ever sticks his head where this guy stuck his microphone. <-- i suppose that says it all. :-)

his measurement is probably overstating normal in room spl by 20db or more.


LP, what is that? I thought everyone listened at their window-sill and with their ear suctioned onto their car's front windshield corner; especially while texting and driving around bends at 100mph while watching long LOTR movies on the dash LCD biggrin.gif
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post #7 of 10 Old 03-06-2013, 11:51 PM
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Lmao. Easy now as I was proud of each .5db my installer could gain on my dash in the comp setup I had back in the day. I spent more money on that setup than my home theater audio sadly lmao. Broken windshields and hair tricks back in late 90's were rather impressive to say the least though. I didn't have any LCDs and DVDs cause they used too much precious power that was needed for more dbs. Another sad thing is I still have all the amps, mids, highs, processing, altinators, and power supplies so get tempted to see what could do with today's high excursion drivers. The truck doesn't run well enough to go out of town but still tempting as it looks good and wouldn't cost anything more than the drivers and new interior.

Too bad I can't sit in a window seal in my theater! Might just have to cut a hole a put one in for mic placement though! Sadly it would probably be easier to tame than my LP was. It's not as good as your previous rew sweep but pretty close.
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post #8 of 10 Old 03-07-2013, 07:33 AM
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Main reason for buying a Termlab sensor, iirc, is the higher SPL operating range. Once you get to a certain SPL, not only are the condenser mic based sensors not useful, you can damage them. We used a Termlab sensor when testing the original Dodecasub. Had to. >>130dB would have killed a normal measurement mic.
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post #9 of 10 Old 03-07-2013, 08:43 AM
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Quote:
Originally Posted by cptomes View Post

We used a Termlab sensor when testing the original Dodecasub. Had to. >>130dB would have killed a normal measurement mic.
Just measure outdoors at 10 meters as Tom Danley does.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
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post #10 of 10 Old 03-07-2013, 09:26 AM
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Quote:
Originally Posted by stormwind13 View Post

No way in hell that guy is getting 142db with that gear.

Maybe with the sensor in a port. tongue.gif Edit: I got a second to watch the placement. I am not sure if he has the capability in that small spot.

I have never used the Term Lab, however I know many who do use it in the car audio world and praise it for accuracy at higher SPL levels. I remember reading somewhere that NASA used them to measure the shuttle.
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