Correcting the Room
Meridian, one of the leaders in digital audio solutions for home and studio, has overhauled its 861 surround pre-pro to include room correction functionality. Version 4 of the 861 ($14,740) uses the EF20 DSP card with Motorola processors running in 48-bit mode. Up to 60 filters can be applied to a multichannel profile. The correction concentrates on low-frequency room correction because — and here I am vastly oversimplifying Meridian's position on this issue — that's where problems can be most easily fixed without causing undesirable side effects.
The Krell Showcase ($4,000) offers several types of EQ filtering with four memories. There are six crossovers for subwoofers (from 40 Hz to 120 Hz) plus high- or low-pass filtering for speaker or room correction. Peak and notch filters correct frequency bulges (the width of the peak or notch is adjustable). And for more subtle correction, you can use bass and treble shelving. The filters can apply to any one speaker, or all speakers, and can be overlapped to provide truly comprehensive room correction.
Infinity has made integrated room correction technology a part of several of its speaker lines. The most affordable example of the Infinity RABOS (Room Adaptive Bass Opt-imization System) is built into the $799 Alpha 1200s subwoofer.
To implement it, you need the $60 RABOS kit, which includes a test CD with bass tones and a sound pressure level meter designed especially to measure bass tones. Run the tones, measure them with the meter, log the numbers on a frequency response chart, connect the dots, and you have a quick-and-dirty picture of the room's primary (and probably secondary) bass peaks. Lay the plastic Q-Finder, made of hinged sheets of plastic, over the chart to calculate the frequency width of the needed correction.
If you'd rather not do the calculations, the Infinity Web site has a RABOS calculator (located at infinitysystems.com/homeaudio/webrabos/rabos1.aspx). Then use the parametric EQ controls built into the sub to dial in the center of the peak frequency that needs correcting, the level of the cut, and the width. I've tried it and it works.