From: Martin Baird
Dear Bob,
First of all I wanted to thank you for your great web site. I have learned a great deal from reading your articles and I know that I am a better studio engineer because them. Currently, I am using your article on Sub Woofers to balance my system. I have the Rebecca Pidgeon CD you suggested. It revealed a room node peak at 125 Hz and a dip at 90 Hz so I am getting some bass traps to help solve that problem. My set up includes a pair of Tannoy PBM-8 mkII Limpets (powered) and a BagEnd InfraSub 18 (powered). I want to pull the Tannoys away from the 135 degree angle corners they are currently placed near. How far from the walls is far enough, as to monitor speaker placement, in regards to bass build up? I know placing monitors near walls or corners will cause the bass freqs. to increase. I want to pull mine out a bit but I don’t want to eat up any more of the room than I must. Is there a point (distance) typically at which the bass build up problem ceases to be an issue? Any advice or direction is much appreciated.
Sincerely,
Martin Baird
Hi, Martin. There are some scientific references that I have not at my hand which purport to guide you into knowing the exact best place to put your woofers. But I think before you do the bass traps, unless they are very specifically tuned, that you should do some work with positioning. Get an excellent time-delay-based FFT analyser, and armed with the knowledge you already have (that you have a peak at 125 and dip at 90), try to relocate the woofers in the room until those particular problems are lessened on the FFT. Don’t try to remove them completely, as the ear is the final judge and the analyser gives much too much detail. Then listen again and see how much it is improved. Finally, then go with the bass traps.
By using the combination of objective and subjective (but semi-objective) analysis in my article and outlined above, you should end up with a much more satisfactory experience. But your resonance frequencies indicate that your room may be too small and special treatment is probably advised. You might also consider a diagonal placement of your system to avoid corner-induced room nodes. This is not an uncommon solution in rooms that are so small that there are resonances at 125 Hz.
Hope this helps,
Bob