Experiments in Home Theatre Frequency Testing

[dortamur]

As most of you have probably figured out, I'm a bit of an Audio enthusiast. The quest for audio nirvana is never-ending, and my latest foray into improving my home theatre was to delve into the guts of system testing and tuning! I recently acquired a SPL Sound Level Meter, and armed with the Bink Audio Test CD to play certain frequencies, set out

Comments

[dannipenguin]

Have you ensured that you have oxygen-free copper, biwired speaker cables with ceramic plinths to prevent corruption from any ground noise. Also make sure that they're not a quarter wavelength of ANY frequency, so that they don't set up standing waves inside the cable and attenuate the signal.

[dortamur]

Ahahaha!

And always buy Monster cables - so expensive they MUST be better!

And gold-tipped fibre-optic cables for better connectivity!

[dannipenguin]

My point is that transfer functions are rarely flat. Neither amplifiers nor speakers provide a flat transfer function even in their passband. If your room was 4.1m wide, it would just be resonant at a new frequency. I wouldn't stress so much.

Otherwise I have a mica mat I can sell you to put on top of your compact discs that helps ensure the least significant bits are read from the disc surface and processed by the DAC.

[dortamur]

Of course. Except that because our room is 4x8, it's even worse, since either way affects the same frequencies. I already knew square rooms were a no-no for theatres (but didn't consider it when we first built), but recording samples, noticing a trend, doing the math and finding the theory corroborate the results was pretty cool.

And it's not an unsolvable problem - the symptoms can be reduced to approach the ideal. I don't expect perfectly flat response. I'd rather not have 10dB spikes at certain frequencies or positions in the room, if I can.