Measuring room frequency response

[Bucketfoot]

What do most of you use (hardware & software) to measure the frequency response of your rooms?

I probably see the most references for the Radio Shack handheld soundmeter. But frankly I'd prefer being able to do a sweep, instead of manual plotting.

Does anyone have experience with either the Behring ECM8000 or the Dayton EMM-6 (are these the same device, just relabeled)? And what software (preferably free or cheap) can I use along with something like one of these?

I actually have a handheld meter (Sper Scientific 840028) that I used to use for measuring HDD noise (back in the days before fluid bearings), but given it's limited frequency response (32Hz to 8KHz) and not having any clue how accurate it is, I don't know that even want to play around with any measurements using it.

[Bass Addiction]

I use the OmniMic....

I have used Room EQ Wizard Software with a ECM8000...

Both work fine but for me, I prefer the OmniMic for very fast set-up and readings.

[HopefulFred]

I don't (yet) have any experience with using them, but I bought a calibrated ECM8000 (which I believe is different from the other mic Dayton EMM-6) and an ART USB dual pre to run it. This was a setup recommended to me by one of the regular posters at HTS. I've plugged it up and gotten through the calibration, but don't have anything to measure just yet. It was a little bit of a fight to find the right cables and figure out a few weird things (like you have to use the left channel sometimes and the right other times, even though there seems to be no clear reason). I'm sure I'll have to figure it out again when I finally get around to measuring anything, but hopefully this time it won't take more than 10 or 15 minutes. I have about $200 into it, including cables and premium plus calibration (I figured, why cheap out on calibration, when it's only 10 or 20 dollars more?). I still have to get an SPL meter, since the ECM8000 and REW setup has so many gain settings built into it, there's no way to know what actual SPL you've got without an extra meter to calibrate the system.

I was tempted to buy the omnimic, but there are more functions built into REW (so I'm told). If I'm going to do it, do it all the way, right? I could see the reasons to get it, but overall, it wasn't the choice for me. The strength of the forum at hometheatershack made REW seem like the way to go, to me.

Fred

[fitzwaddle]

I use an ECM8000, M-AUDIO Mobile Buddy pre-amp, Behringer UCA202 USB audio "card", and el cheapo used laptop running REW.

[HAL]

The Behringer ECM8000 with calibration data, a balanced mic preamp and laptop PC Sound card (an Echo Digital Audio Indigio IO pcmcia card) and REW work well.

[Bucketfoot]

Do you just use REW with a standard built in soundcard? It would just seem to me that the performance of these is probably questionable at best. I guess I should add that I already have a Focusrite 8i6 preamp (with USB output) to use with the mic to get the measurement into the pc.

Would I be better off using a test disc of some sort?

I guess I should start by doing a little reading up on REW ;)

[HopefulFred]

Most of the time you end up with an external sound card because the onboard doesn't have the right features. For condenser mics like the Behringers, you need phantom power (I still don't understand what that actually means) and onboard sound cards can't provide that (in any variation I have seen, though i don't know a lot). Second, most onboard sound doesn't have the right outputs/inputs, especially in laptops - the headphone jack won't cut it. The actual quality of the components isn't really the problem, because you'll calibrate that out anyway.

REW generates it's own sounds - and I think that's only the sine wave sweep. And white or pink noise... I think that's all it uses. I haven't done it yet, but I think if you want a sustained sine wave or something, you'd need another source.

[Bucketfoot]

OK, so it sounds like I will want to use my Behringer UCA202 to get the output via USB rather than using the headphone jack.

The Focusrite takes care of the phantom power and the input for me.

[tesseract]

Maybe this can help with setup.

http://www.youtube.com/watch?feature=player_embedded&v=e4uSR3cUUSY

[cel4145]

I just ordered dual SS 18.1s from Craig, and so I'm wanting to figure out best placement in the room to smooth the frequency response. I have an analog Radio Shack meter. It seems like a lot of money to spend on a condenser mic and preamp setup for the convenience of using REW. I don't need the room measurements for setting an EQ as I have Audyssey MultiEQ and just picked up a used Anti-Mode 8033B.

Would it really be that much of a time save to get the new equipment considering I only need to measure a few positions? Or wouldn't manual plotting and RS SPL meter work fine for such limited use? It's a living room HT setup, so only a few placement options.

Thanks for any thoughts on this.

[tesseract]

Congrats on your new SS 18.1 purchase, cel4145. The Anti-Mode you purchased will help greatly with dialing the subs into your room. Getting placement correct first will help you get the most out of the Anti-Mode and the sub amplifier.

I have the older CS-18.T Duos, essentially the same setup. I started out with test tones, a Radio Shack meter (minding the correction at low frequencies), and manual plotting. I am very happy with the results. In fact, I have a Cross Spectrum Premium+ calibrated ECM8000 mic, Tascam US-122L mic pre, REW and a laptop that I haven't pressed into service, yet. Been too busy with work and just enjoying the sound as is!

For more info on placing your duals, check out this thread, Improved Bass Through Multi Subs.

Have a look at what other members have done in our User Review Forum.

And most of all... have fun!

[cel4145]

Thanks, Tesseract.

With all the research I put into looking at condenser mic solutions the last few days, I bet I could have run three or four manual plots ;)

Then it seems like it can take a while getting REW up and integrated the first time one does it. I think I'll save myself about $150 bucks for mic, cables, preamp or mixer (I have a sound card that has a line in), and mic stand and do it by hand.

And it seems like this would also tell me enough to know if I need a the bass boost on the Dayton amp. And then the Anti-Mode and MultiEQ should take it from there. Does that make sense?

[tesseract]

Makes sense to me. :applause:

[sbdman]

I have used a first generation - meter, not digital - RS meter with REW, and loaded in the calculated filters to a DSP-1124 with fair success - sounds better than just Audyssey XT. It is possible with what you've got now, to get better results with many many more measured points than by hand with a few downloaded sine waves, and see any narrow peak/valley room problems using REW. Just looked at my test - there were over 560 test points between 20 and 200 Hz, and they started down below 5 Hz. All this for a ~5 second sweep? Gives a very detailed response.

REW is a pita to me to get set up. I've bought two external sound cards and think I've found the real problem was in the long RCA cable RS mic out to sound card had a short in it. Even the "simple" job of doing a loop back test on the sound card has given me fits. But, if it falls in place for you, it will definetly shorten the time to test for multiple sub locations. It's great to have a detailed curve

Testing by hand and adding in the RS correction factors (it's 0 dB at 1K hz, down about 3 dB at 100 and curves up to -17 dB at 20 Hz - MKtheater would argue this drop for the meter) takes maybe 10-20 minutes to measure per position - boober could probably tell you better the time it takes.

Probably best to start with the first sub, check for the flatest location, then add the second sub and sometimes the opposite wall/corner will yeild the smoothest result? Look at tesseracts link - he's got the best suggestions of most.

[cel4145]

I have the newer RS analog meter.

Home Theater Shack has a downloads page in the EQ section that has an Excel spreadsheet already setup for the different RS meters. I just have to plug in my SPL readings at certain frequencies, and it will generate a curve. And they have links to the necessary test tones. Seems easy :)