Historical

Editor: Thank you for offering us the opportunity to get a "second opinion" on the subjective performance of our TC-50/Servo combination. While I find AHC's impressions to be much more akin to our own than were JGH's in Vol.9 No.5, I do not experience the lack of dynamics in the upper bass/lower midrange. I have experienced this when the Servo placement was incorrect, which is why I treated this subject in great detail in the manual. And we have received no comments regarding this apparent lack from our dealers, nor from the 700+ owners of the Servo.

Indeed, integrating a subwoofer into any system is problematical, primarily because the frequency range over which it operates and crosses over to the satellites falls right in the middle of the frequency equivalent of the dimensions of typical listening rooms, at 10-25'. Because the phase relationship of the Servo and satellite throughout the crossover region is a nearly constant 0 degrees, the power response in the room is 3dB less than a system with no crossover. A typical system would exhibit a more linear power response, but would consequently have a greater degradation in transient purity. This is one of those situations where one cannot have one's cake and eat it, too.

On the positive side, however, this means that there is less ambient energy in the crossover region bouncing around the room (assuming the walls are suitably massive enough to contain it!), resulting in a decrease of standing wave problems. This is helped by the fact that we are "driving" the room from four sources instead of two in a subwoofer-less system. On the negative side, the constant phase relationship creates a situation where the Servo and TC-50s never sum to greater than unity, that is, there are no "bumps" in the total response, and off-axis energy decreases slightly in the mid-bass. This gives a slightly lean flavor to the upper bass, but contributes significantly to the impression of taughtness and control, and assists in the perception of all the musical subtleties that live in between orchestral swells and kick drum thumps.

In medium to small rooms, these characteristics have proved to be beneficial; in larger rooms, not so. As always, it is left to the end user and his intelligent dealer to determine the suitablity in each instance.—W. John Bau, Santa Fe, NM