Von Schweikert Audio VR-4jr Von Schweikert Audio, Armorlite Drive, San Marcos, CA

Von Schweikert Audio

World Class Reference Speaker Systems for Music and Film

GENERAL TUNING INFORMATION: Both the volume level of the bass and the frequency response of the woofer system can be altered easily by several methods in order to equalize the room’s influence on the bass response. Although the VR bass systems measure ruler flat in larger rooms that have good dimensional ratios, (using both gated sine wave and maximum length sequence FFT signals), smaller rooms tend to have bass anomalies and overloading problems with low frequencies due to the long wavelengths involved.

STANDING WAVE PHENOMENA: Standing waves are dips and peaks in the bass response caused by the room boundaries. Although many people have heard the term, many don’t actually know what causes standing waves and what to do about them. Since all speaker systems radiate bass almost omni-directionally, there are many path lengths that the waves take before arriving at the listening position. Although the first arriving bass wave will have flat frequency response, fractions of a second later the same waves have bounced off of the front wall, rear wall, side-walls, and the floor. These reflections both reinforce and cancel the original direct wave, depending on the wave-length vs. the path length. If the path length is an even multiple of the direct wave at any one given frequency, the reflection will reinforce the first wave since it will be mathematically additive and will cause a peak in the response at this frequency. However, if the path length is such that the reflected wave is out of phase with the main wave, there will be a cancellation in the frequency response. Researchers have found that the dips and peaks in the response can be very powerful, with 18dB variances across the bass range! Note that this effect occurs with ANY speaker design: no speaker system can overcome the law of physics.

When playing a recording with plenty of deep bass, a listener can walk around the room, finding that every foot or two, there is flat response, a peak, or a dip. By walking around the room, you can ‘map’ the response, finding the places where the pressure alternates from high to low. These alternating pressure zones are a natural part of room acoustics and must be dealt with by correct speaker placement.

THEORY OF RECIPROCITY REGARDING BASS RESPONSE: Since standing waves are not easily amenable to correction by equalizing the speaker passively, it is necessary to place both the speakers and listener/s in neutral zones. According to the mathematics of the pressure zones, the flattest response occurs when both the speakers and listener are at opposing ends of the room, directly against the wall surfaces. Since against-the- wall placement is not a prime location for soundstage ‘openness’ and imaging focus, we recommend placing the speakers out into the room, at least 12" from the back wall to start. Then, playing a repeating bass line, walk around the room in the general vicinity of the intended listening position. If you find that the smoothest bass response does not occur where you would like to place the listening seat, you can use the Law of Reciprocity to find the optimum spot.

930 Armorlite Drive,	San Marcos, CA 92069	11
Ph (760)410-1650	Fax (760)410-1655

E-mail:albertvonn@aol.com ~ Website:www.vonschweikert.com