How to use REW to analyze the acoustics of your room...

Hi there, I purchased the Extech 407730 for this test as it was recommended as one of the devices in the instructions. However I noticed after going through all the subsequent postings that the 407730 only has frequency response down to 300hz. I have a subwoofer in my studio setup and was wondering if I should get a different one that has a lower frequency response? I see someone already posed that question, however I wanted to know if it makes a difference with me having a subwoofer. Also I have a couple questions about testing with the subwoofer in the setup: - When we are doing the tests of the L/R speakers for their own separate tests, should they go through the subwoofer (with subwoofer volume at 0)? Or should I bypass the subwoofer for those tests and wire them directly to my soundcard? I assume they should go through the subwoofer as the crossover would affect the volume of the monitors even at 0 volume? - In your additional instructions about calibrating the volumes when having a subwoofer, are you saying that in step 3 we should play around with the volumes of L/R/S at around 77db each, and keep adjusting until all 3 are giving out combined 86db? Thanks!

However I noticed after going through all the subsequent postings that the 407730 only has frequency response down to 300hz.

That's as low as C weighting calls for. This meter is more than adequate. Greg

Hi Greg, that 300Hz comment caught my attention. I'd guess you meant A? Also, I think it odd that any SLM would be restricted to measurements over 300Hz. On a General REW note. Calibrating the Soundcard was perhaps necessary, or desirable for critical timing measures, in some distant past. But no longer afaik. REW, FuzzMeasure, etc. work perfectly well with single channel USB mics.

Sorry, yes. My meter is "flat" only down to 125Hz as well. Greg

Thanks Greg for the reply. And sorry, just read the posting rules and of course didn't have my location entered, which is now there. I'm still not clear about how I should set the volume on my subwoofer when doing the testing. I'd like to get as accurate measurements as possible before posting the results on the site, so want to make sure I'm doing it correctly. If the subwoofer is only playing frequencies less than 80hz (which is what my crossover is set at), and the SPL doesn't pickup these low frequencies, how would I set the subwoofer volume? I'm using two KRK rokit 8's and a KRK 10s subwoofer in my studio setup. Thanks!

I'm still not clear about how I should set the volume on my subwoofer when doing the testing.

I would just use my ears to get a balanced sound between your mains and your sub. After that, do some measurements with REW and check the SPL. It'll be pretty clear on the graph if your sub is too loud or too quiet. Greg

Hello, 1st post here and wanted to thank you for the elaborate guide, I am a studio owner.musician who knows the bare basics of acoustics and build some bass traps/ER traps in the past. I have some free time now and i thought i'll take the plunge into the measurements world (i have always hired some one in the past for that and now i wish to expand my knowledge in the subject of REW). So i started by not getting the behringer ecm 8000 because of your thread and so i went and got the presonus you recommended. I would appreciate it if you could elaborate on why an app like decibel x for the iphone wont be as efficient as a db meter? I would also appreciate it if you could explain whether the presonus will need calibration and if so how do i calibrate it. Thanks!

Welcome. We have not heard from Stuart in some time, so I guess I could help you here. dB or Sound Level Meters come in a very wide range of price and quality. Indeed you may still see mention of the original Radio Shack one, which was a truly awful POS. Over time things change. Now iPhones can become really decent fully featured SLM. The free and cheap ones are fine, I have tried most, but I do appreciate the more Pro nature of Faber SoundMeter and this also this company https://studiosixdigital.com/audio-hard ... phone.html I use my iPhone all the time when doing safety surveys in clubs and venues. One wouldn't want to wander about on a busy saturday night with a Bruel and Kjaer or other big conspicuous mega buck meter. If your Mic has a Cal file, then REW should be able to read it and become a 'free' SLM. The accuracy will be equal to that of the Cal file. I have found the UMIK-1 to be 1.8dB off in two samples from different years. I have found iOS apps to be closer than that. Comparative Calibration is very simple. REW, SoundMeter etc. can be calibrated against a trusted exterior SLM, or a dedicated Calibrator Device if using an external 1/2" Mic You just play a steady Pink Noise, adjust the level to some convenient number on your borrowed, ideally Calibrated, but in any case trusted SLM. Say 75dB. Then use the Cal trimmer in your app to get it to read the same.

DanDan wrote:

Welcome. We have not heard from Stuart in some time, so I guess I could help you here. dB or Sound Level Meters come in a very wide range of price and quality. Indeed you may still see mention of the original Radio Shack one, which was a truly awful POS. Over time things change. Now iPhones can become really decent fully featured SLM. The free and cheap ones are fine, I have tried most, but I do appreciate the more Pro nature of Faber SoundMeter and this also this company https://studiosixdigital.com/audio-hard ... phone.html I use my iPhone all the time when doing safety surveys in clubs and venues. One wouldn't want to wander about on a busy saturday night with a Bruel and Kjaer or other big conspicuous mega buck meter. If your Mic has a Cal file, then REW should be able to read it and become a 'free' SLM. The accuracy will be equal to that of the Cal file. I have found the UMIK-1 to be 1.8dB off in two samples from different years. I have found iOS apps to be closer than that. Comparative Calibration is very simple. REW, SoundMeter etc. can be calibrated against a trusted exterior SLM, or a dedicated Calibrator Device if using an external 1/2" Mic You just play a steady Pink Noise, adjust the level to some convenient number on your borrowed, ideally Calibrated, but in any case trusted SLM. Say 75dB. Then use the Cal trimmer in your app to get it to read the same.

Thanks for the replay, i guess ill stick with the iphone then. Unfortunately the presonus calibration mic does not have a calibration file, neither can i find one online, maybe it does not need one?

Hello everybody! Thank you Stuart for the extremly useful information. Im about to start with my measurements. I would like to know if you are still available to receive my data and give some kind of feedback. If not, does anybody know any member with the expertise and the kindness to help me analyse my data? Regards! D.

Hello everybody! Thank you Stuart for the extremly useful information. Im about to start with my measurements. I would like to know if you are still available to receive my data and give some kind of feedback. If not, does anybody know any member with the expertise and the kindness to help me analyse my data? Regards! D.

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