Instruction manual

78 THE ABSOLUTE SOUND n FEBRUARY 2006
equipment report
Trying the 20.1s with the Pass Active Crossover
T
he stock Magnepan crossover works well enough, but I have always
wanted to try an active crossover with the 20.1. Pass Laboratories
was kind enough to oblige by sending me its XVR1. This is a serious
piece of gear, consisting of two beautifully finished chassis (the crossover
network itself and a separate power supply). The crossover has only four con-
trols on the front panel—separate volume pots for left and right high pass
and for left and right low pass. The back panel offers balanced and single-
ended inputs and balanced and single-ended outputs for high and low pass.
A great deal of thought went into the design of this $5000 crossover.
Depending on the internal settings chosen, between 6dB and about 17dB of
gain (single-ended Class A circuitry) is available in each channel. This should
let you match the gain of almost any amplifiers chosen for high- and low-fre-
quency use. Internal jumpers allow the user to use an enormous number of
crossover frequencies. More interestingly, each high- and low-pass filter is
user-configurable at a 6-, 12-, 18-, or 24dB-per-octave slope, with the choice
of three independent Q (sharpness) controls for each filter. Thus, the XVR1
offers almost unlimited crossover flexibility. Additional XVR1s can be added
for tri-amp, quad-amp, or even more complex setups. The only things missing
for the intrepid speaker-builder is some type of equalizer.
When I initially installed the XVR1, I chose crossover settings almost iden-
tical to the Magnepan factory settings. (I subsequently experimented with
other settings but ended up preferring the factory ones.) High pass was set at
290Hz with a simple 6dB slope, while low pass was set at 110Hz with an
18dB slope. The Q setting was at “medium” for each. The VTL 450s were
used for high-pass amplification and a Sunfire Signature stereo amplifier was
used for low-pass duty. The volume controls on the Pass unit allowed precise
matching of volume for each amplifier, after a few hours of trial and error on
very familiar musical material. My goal was to set the bass level, relative to
the mid/highs, as close as possible to the stock Magnepan crossover.
The most immediate effect of the Pass was a greater sense of headroom
and dynamics. And while I was using a second amplifier of higher power, I don’t
think the results were due solely to the additional amp. Even the mids and
highs, driven by the VTLs, were more dynamic and alive than before, which
could be attributable to one or both of two factors: The VTLs no longer had to
reproduce bass frequencies, and they no longer had to drive the Magnepan
external crossover. Using an active crossover, you may well be able to drive the
mid- and high-frequency sections of the 20.1 with lesser power, and you could
also choose a less expensive but still-sufficient amp for the bass.
The P
ass unit operated fla
wlessly and w
as dead silent. Though trans
-
parency through the XVR1 was excellent, I can’t really say that the sound was
more transparent than though the factory crossover.
So,
what’
s the best way to cross-over the Maggies? The overall sound
through the XVR1 was somewhat more open and dynamic than the stock
crossover, but I am not talking orders of magnitude. It was ever-so-slightly brighter than the stock unit, but never objectionably so. I also
seemed to gain an extra octave of low-frequency extension when using the XVR1, but this was probably a result of substituting the
Sunfire amp for the VTLs for bass reproduction. On the other hand, the sound through the factory crossover and the VTLs run full-range
was slightly more full-bodied and warm than the bi-amp setup, which is nothing to sneeze at. Overall, I would give a slight nod to the
active crosso
ver
,
especially insofar as it allows you to use separate,
and possibly less pow
erful,
amplifiers in a bi-amp setup.
Yet the performance of the Maggies with the stock crossover is always satisfying, and once the cost of the Pass is factored in
(as well as the need for an extra set or two of interconnects), the stock setup is by far the most economical way of experiencing
the 20.1 magic.
DS