Measurement gear for room EQ

Hi,

I visited Nick (Brionbiovizier) the other day and was watching him and Simon (Tenson) measure and correct the room using a DEQ2496, I have a couple of questions about what to use to do the same with my system.

I plan on using a DEQ as the EQ, but I know I can get better results by using PC software to do the measurement then feed the results into the DEQ.

I'm planning on using ETF software for measurement, a Behringer ECM8000 mic and MIC100 mic preamp.

Simon was using a unidirectional mic to measure each speaker individually at one point, is this essential or can I get reasonable results using just the ECM8000? I mean can I usefully measure each speaker individually with a omni mic? I know measuring each speaker individually first is the right way to go about this, then once they are individually corrected I will then correct both together at the listening position.

As for PC hardware, I presume the ADC and input stages in a laptop have a ropey and pretty useless response, I looked at Behringer UCA202 and FCA202 which are USB and firewire (respectively) IO boxes, basically USB soundcards as far as I can gather. Would these suit my purposes? The USB one is half the price of the firewire version, would I need the faster firewire connection or would USB do? I'm guessing it will as sampling 16/44 is about 690kbps/86kBps which is easily handled over USB.

The only thing that occurs to me about using these is that it may be better to use the DAC and ADC in the Behringer DEQ2496 (which will be the DAC in use in the system when playing music) to do the measurements - would this be significantly better? If so, since the UCA202 only has digital out, I presume I need some sort of USB or firewire SPDIF I/O box which can take a digital in from the DEQ and feed it to the PC - any suggestions for cheap and reasonably good boxes that serve this purpose?

Thanks.

Paul

 

Paul, I was only using a cardioid mic and doing close, gated measurements of each speaker to get the Xover set-up. As you don't have external Xovers you don't need to do that.

What you can do is get a soundcard that can record and play at the same time (full duplex). Send the output to the DEQ inputs, the DEQ's main outputs to your hi-fi and one channel of its aux outputs set to bypass the EQ sections (what comes in goes right out again) to one of the soundcards input channels. The microphone then goes to the other input channel.

Doing this the computer can take into account the effects of the DAC's and ADC's in its measurements.

Use the ECM8000 at your listening position. EQ both channels to match each other (above about 200Hz just EQ the general trend, not any sharp peaks or dips). Once they match each other (they don't need to measure flat) you can EQ them both together for a flat response, or whatever you like.

First of all I would just try the DEQ with its automatic EQ to see if you like it. It take quite a bit of practice to get used to doing it manually, taking what you see on the screen and knowing how it will sound.

You may find that if all you want to EQ is the bass (in a well controlled room you shouldn't need much else) then you can simply use a program like CoolEdit (Adobe Audition) to play white noise through the system and record it back in again. Compare the recorded signal to the output and adjust the EQ accordingly. The cleverness of ETF is not so necessary for just the bass region, though it is useful to see the waterfall plot.