REW Forum

**Mark DuBerry** · **02-13-08, 02:09 AM**

I have a very small home recording studio which I acoustically treated last year with DIY rockwool panels according to Ethan Winer's and others' guidelines. The room is 10'x6.5'x8'.

I recently bought a Radio Shack 33-4050 SPL meter in order to measure the rooms acoustics / frequency response using REW. I have since discovered through reading some posts on this forum that this meter is only good for measuring the low frequencies. I presume that is not enough for my room and that I need something that will cope with the whole spectrum(?). As you can tell, I haven't used REW before.

I have a Rode NT 1 which is a good quality cardioid capacitor mic with a frequency response of 20Hz-20kHz. Will this suffice for taking the measurements or do I need to go out and buy a special measuring mic?

Thank you.

**brucek** · **02-13-08, 06:08 AM**

Do you have a calibration file or graph of the microphone? If so, you can create a calibration file that will work with REW.

brucek

**Mark DuBerry** · **02-13-08, 08:49 AM**

Hi brucek. Thanks for your reply. That's good news but no, I don't have the file or graph. Is that something I can generate myself or do I have to get one from somewhere? How do I go about doing that? I will try and find this out myself by looking at the help files etc. but I would be grateful for any further help if possible.

Mark

**brucek** · **02-13-08, 09:28 AM**

Well, a calibration file something is that will come with a microphone to show it's frequency response.
If you use a mic or meter that we have tested on the site, then you can get away with using those calibration files (if you own one of those), with an assumption that they're accurate enough for home use. We have cal files for all the Radio Shack meters, Galaxy CM-140 meter and the ECM8000 microphone. The Radio Shack meters shouldn't be used much beyond 1000Hz as it seems as they aren't accurate past that. The ECM and Galaxy are full range. The ECM requires a preamp though.

If you don't have a cal file for the microphone you own, then you have no way of knowing its accuracy I'm afraid.

brucek

**Mark DuBerry** · **02-13-08, 09:50 AM**

Hmm. I'll see if I can locate a cal file through Rode. Alternatively, I may pick up an ECM8000. I want to measure the room mainly to see how effective the treatment I have used is but also to find if there are any problem frequencies needing further attention, particularly in the lower end. I have a lot of bass trapping as it stands. Would you happen to know how necessary it would be to measure beyond the 1000Hz or would the fact that the RS meter will give me a good idea of what's happening in the lower frequencies be a good enough test for my purposes?

Thanks again.

**brucek** · **02-13-08, 10:47 AM**

Well, my understanding is that treatment doesn't do much above ~500Hz and does little for modal problems below ~80Hz (where eq is usually employed), so I see no reason not to use the Radio Shack meter. They're suitable for that area..........

brucek

**Mark DuBerry** · **02-13-08, 11:04 AM**

That's great brucek. I'll do that and maybe post the results to get some help interpreting them. Meanwhile, I'll try and hunt down a file / graph for the NT1 to maybe compare the results obtained with both the mic and the meter.

many thanks,
Mark

**Mark DuBerry** · **02-13-08, 01:00 PM**

Actually, I'm having a bit of a job finding a fre. resp. graph or a cal file for the NT1. The Rode website has one for the NT1A but it's a different design with an improved response so I don't think it's any good re. the NT1. I wonder if anyone knows where I can find one?

I will use the RS meter as brucek suggests but I would like to test a wider fre. band if possible as well without buying another mic.

Thanks, Mark

**brucek** · **02-13-08, 01:13 PM**

You can always have your microphone calibrated if you feel it's a decent mic. It can be expensive though. I suspect you could get a Galaxy meter for the same price. Sometimes stage mics don't make great measurment mics if the response is set for voice. I guess it needs external biasing, so some type of preamp is needed?

brucek

**Mark DuBerry** · **02-13-08, 03:37 PM**

I don't think it's an option to get the mic calibrated. I could buy the Behringer or the Galaxy at that rate. The NT1 is a very good mic and is regarded as fairly flat; not sure what you mean by a 'stage' mic except it is of course a recording mic and is not specifically for vocals; it works well with most applications. I imagine it would do the job well if I could get a cal file together.

I'm going to contact Rode by phone just as soon as the time zone brings them into opening hours and do my best to get a graph. If not, I may have to work within the limitations of the RS meter.

Thanks brucek. I do appreciate your help with this.

Regards,
Mark

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