I just purchased an RTA program that allows analysis down to 10Hz. The previous RTA software I had had a lower limit of 20Hz. Since I could now see what exactly was going on in the region between 10Hz and 20Hz, I decided to see what improvements I could make to my four JBL 18" subs. I did modifications to the electronic crossover's extreme low end active EQ frequency and slope, lowering it from 20Hz to 10Hz and increasing the "Q" of the circuit so it would be more selective.

The result? Well, using pink noise and the spectrum analyzer, and measuring at the listening position, at 10Hz the in-room response is absolutely dead flat relative to the higher frequencies! Not 10db down, not 3db down, but dead flat. I don't know what the actual lower limit is since the RTA software only goes down to 10Hz, but I shudder to think

How does it sound? Well.... I played some organ music I recorded of an organ that has a genuine 32 foot rank of pipes which yields a 16Hz lowest pitch, with "beat" frequencies of even lower pitch. The difference was remarkable. I didn't expect that opening up the low end from just below 20Hz down to below 10Hz would make that much difference - I was wrong, it makes a huge difference.

This could get scary

[This message has been edited by soundhound (edited August 14, 2003).]