Assid,

Setting up a solution with a mic/soundcard/rta is a "life time" solution to audio measurement. The alternate that Dundas came up with I see as more an one off FBD solution for say, tweaking your sub for your HT.

If you interests are in audio measurement for improving any speaker (or building them) than you need a good quality sound card (high signal/noise, etc) and at least 96khz sample rate to be able to properly sample 20khz signals. Plus a flat Mic, and software to generate and analyze signals.

Before picking up an external USB soundcard, do some research on who delivers the best "audiophile" solution at a resonable price. Also, sample rate is very important for higher frequencies.

If you just want to measure your sub, there is lots of solutions out there. I have heard some people have resonable luck with the Transit $99, but I have never used one: http://www.m-audio.com/products/en_us/Transit-main.html

The big difference between a SPL meter like the ones sold a Radio Shack and buy a quality measurement mic is the accuracy and sample rate you will be able to obtain with the mic solution. Some of the SPL meters do have a jack for connecting them to audio in, (I have one) but at lower freqencies are not that accurate.

Eric Wallin had done some work to try and improve the various Radio Shack SPL meters, but by the time you are done, you could have bought the EMC8000.. http://mysite.verizon.net/tammie_eric/audio/audio.html

Here is a link site for the major soundcard manufactures, but do your research before buying.. http://www.synthzone.com/sndcard.htm

Lastly, remember that the FBD is a perminent solution for your Sub, don't get caught up in buying something that is for sound measurement in that spot, unless don't mind disconnecting it from your HT every time you want to measure some sound. Thats what the rest of the equipment is for...

Good luck..