# External signal for REW?



## neumei626 (Feb 8, 2010)

Hello. I've tried to find the answer to this on google, but with no luck. 

My computer is in a room about 45 feet away from my system, and I can't disconnect it and bring it in there. I thought I only needed one 50 ft cable, but have recently found that I need two. I have a RAT shack digital SPL meter, and PLENTY of test tones including sine sweeps, and pink noise. Is there any way I can use external sounds to use REW, or must I use two cables, one going to my processor to play the sounds REW is telling it to play, and the other obv. going from my meter to the soundcard input?

And another thing, I have searched the internet trying to find the actual data correction value files for my SPL meter to download onto REW, but I can't find those either. Any help would be GREATLY appreciated! :bigsmile:

EDIT!

OK, Just kidding about those things, I got solutions to the problems. Found the cal files and used about 5 barrel connectors to stretch about 6 cables together to make it the 45 feet. Barely!

But.... another issue.

My graphs appear to be too 20 hz heavy compared to my manual SPL reading in front of my system. I have the BFD purposely about 15db down at 20hz so my MFWs won't bottom. However, my graph says it is louder in the 15-25 range than the rest of the frequencies. But my SPL meter tells me there is less when I take the readings in fron of my system. Way less. Way more less even than the correction values could explain. The graph is basically the opposite of what I think it should say. Any ideas? Thanks!


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## neumei626 (Feb 8, 2010)

Anyone have any ideas?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to toe Forum, neumei!


> Is there any way I can use external sounds to use REW,...


Sure, but you’re limited to using REW’s RTA feature. Also – I have an RTA which can generate a pink noise signal, but I found I got a somewhat different reading at the lowest frequencies using it vs. REW’s pink noise signal.



> And another thing, I have searched the internet trying to find the actual data correction value files for my SPL meter to download onto REW, but I can't find those either. Any help would be GREATLY appreciated!


Sure – but we would greatly appreciate it if you would tell us the make and model. 



> My graphs appear to be too 20 hz heavy compared to my manual SPL reading in front of my system. I have the BFD purposely about 15db down at 20hz so my MFWs won't bottom. However, my graph says it is louder in the 15-25 range than the rest of the frequencies. But my SPL meter tells me there is less when I take the readings in fron of my system. Way less. Way more less even than the correction values could explain. The graph is basically the opposite of what I think it should say. Any ideas? Thanks!


I’m afraid you’ll have to explain further, ‘cause this doesn’t make much sense. The SPL meter can only “tell” a 20 Hz tone from any other if you’re playing a 20 Hz sine wave or filtered pink noise signal. Yet, you can’t generate an intelligible subwoofer graph with nothing but a 20 Hz signal... :scratch:

Regards,
Wayne


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## neumei626 (Feb 8, 2010)

Haha sorry, I am using a BFD, the 1124, and my meter is the new digital rat shack meter.

I actually got REW hooked up with one wire from the meter TO the soundcard and one wire going FROM the soundcard to my processor. So I did run the REW sweep I was supposed to. It was playing through my system, and I ran it from 10-120 hz. I wasn't just playing a 20hz signal and expecting to see my frequency response across the bass spectrum, haha. My question was this; the REW graph is showing there is way too much output below 25 hz. That seems to be the only inaccurate part of the graph, as all the other above frequencies match what my meter says when I take readings in front of my system. I am wondering what is responsible for the innacuracy of REW below around 25 hz. Thanks!


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## Wayne A. Pflughaupt (Apr 13, 2006)

Well, a couple of things jump out at me. For one, your REW reading is only as good as the calibration file for your meter. I suggest using the one from our Downloads Page instead of whatever you found on the internet.

Second, when you take an SPL reading with the meter – let’s say using a 20 Hz sine wave - there is no calibration file added to what the meter’s display reads. The meter is several dB down @ 20 Hz when switched to “C” weighting, and off the scale when using “A” weighting. So, that’s why REW graphs will show higher signals in that frequency range. After you take your REW reading you can go back into the “Settings” window, “Mic/Meter” tab and remove the calibration file. That way you can compare your readings with and without the file.

Regards,
Wayne


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