The Room Resonance Remover(tm) from Lonnie Bedell Electronics is a new audio notch filter that uses subtractive equalization to cut in the 125-540hz range to counteract room resonances that degrade sound quality in Home Stereos.
At first glance professional sound reinforcement and home stereo may seem worlds apart, but they both suffer from the same room resonances that amplify certain frequencies as the walls vibrate sympathetically. This causes the sound system to feedback prematurely at those frequencies, as well as sounding "muddy" as the low mids are amplified by both sound system and the room itself.
While the immediate goal for a PA engineer may be to get more gain before feedback, by "ringing out the room" they also inadvertently gain the additional benefit of flattening out the frequency response of the listening environment by working with the room's natural characteristics instead of against them.
Home stereo and other consumers can benefit from the same subtractive equalization as well. Instead of boosting high frequencies, for example, they may find a cut in the the low mids they are amplifying might yield them all the high end they desire.
The Room Resonance Remover(tm) cuts up to 30db in the 125-540hz range on 2 separate channels. The RRR has variable settings for frequency, Q (filter width), and depth (amount of cut). Inputs & outputs are line level, and can be configured as RCA or 1/4" jacks. It is available in 9 Volt battery or AC powered versions. High performance 5532AP op amps are used throughout for low noise.
More info on the The Room Resonance Remover(tm) is available at www.roomresonanceremover.com