It depends on if you have a measuring microphone that is flat enough to do the measurements. The RealRTA does give 1/24th octave resolution which is basically as good as a frequency response plot. It also has a "chirp" function where you can do a frequency response sweep quickly across the entire frequency band. For $99 it is a bargain I think. Personally, I like software implementations because they are more upgradable. And in addition, the RealRTA program does have a function to calibrate for the deficiencies of your soundcard in frequency response.

I have used a Panasonic condenser microphone capsule available from Digikey electronics (www.digikey.com) part # P9959ND that is accurate to less than 2db in the extreme high end. In the low end and midrange, it is within 1db, even down to below 20Hz. Of course you will need to power it but this involves nothing more than a 9 volt battery, a 2k2 ohm resistor and a 220uf capacitor (to isolate the DC from the sound card input). You will also need a 100k ohm resistor after the capacitor to discharge the DC, so the input of your soundcard doesn't have to do this!


[This message has been edited by soundhound (edited August 24, 2003).]