I have used several. What's your system and what's your problem?
Kal and Eldartford : thanks; I was looking at the Behringer. I am not necessarily addressing a particular problem, Rather, my interests are in objectively evaluating the response of my system and correcting, if indicated, any deficiencies. What I am looking for is an efficient way of inputting a signal of known frequency content and measureing the response at a point in the room. Then inserting the filtering and seeing if I like the result. One box that does both of the above is what I am after. System consists of Marantz CDP - Mcintosh C45 preamp - Mcintosh MC 402 amp - B&W 803S speakers.
That's cool... you're going to objectively evaluate the results from a subjective viewpoint.
Given that no room is "perfect" and that most have serious flaws, there is a likely benefit to EQ... it just might not turn out to be the curve you think it ought to be.
But a unit like the aforementioned Behringer can analyze your room and show you what frequency bands have the most deviation from flat. It can also correct across the full audio spectrum and provide various filtering effects.
However, just like some amps sound better than other amps, some EQ's sound a lot better than other EQ's. They're not all created equal.
I've gotten very good results using a dbx 14/10, which can store up to 10 curves... in effect you can equalize each of your source components to your taste, or use different curves to tame down bright recordings, or recordings with too little, or too much bass. However you must be sensible when applying bass boost.
I'd say start with the Behringer, because at least that will show you where the peaks and dips are...and it probably has the widest variety of settings and filters and the ways it can be adjusted. What complicates matters is that in addition to the different EQ's sounding "different," they all have different features and settings.
I use Fuzzmeasure with a Behringer ECM8000 and E-Mu 0404 USB Mike amp - it is a very similar setup to Room Eq Wizard. Measurement plots are displayed on my virtual system. I use it for bass calibration to the sub only - speakers are run full range without any EQ. Fuzzmeasure uses a chirp or sweep which I prefer for running tests (very quick).
I suspect something like this is essential once you have done all the acoustic treatments that you can accept aesthetically. It certainly helped me correct for what was too much bass and too much room modal response at certain frequencies.
Sarcher30- Try one of the TacT Audio systems(with a MauiMods power supply). If you are not opposed to actively bi-amping: the RCS 2.2's are transparent enough not to lose a bit of ambience, timbre, soundstaging(width/depth) or image information, while providing a beautifully clean mid/high response. I own a DEQ 2496 to test/verify my steady-state freq. response. You can't beat the price for a 6th octave RTA. It's never IN the system though, for the same reasons you've stated.
I'm using E-Mu 0404 USB. It is nothing special - although it does have 24 bit capability - but honestly you really don't need anything special for in room bass measurements and the ECM8000 microphone is good enough. I am not sure is if the room EQ wizard allows averaging but a useful feature of Fuzzmeasure is the long 10 second sweeps which you can also average as many times as you want. If you want to get accurate RT60 measurements down to 20 Hz then you need a quiet room to begin (all AC's, furnaces, dishwashers, laundry off and nobody moving around the house) AND you'll likely need to do some averaging (noise level goes down as the square root of the number of repeated measurements and remember that RT60 is the time to decay to -60 db SPL and that is very very low when dealing with bass frequencies that tend to hang around as well as pass through walls).
Remember that your analysis plots cannot see below the noise floor - although our evolutionary honed ears/brain can usually pick out harmonic structures about 15 to 30 db below the same noise floor.