Bass Management - Active Crossovers
The challenge
The challenge used to be that most processors did not handle bass
management correctly or that external boxes like DVD-A or SACD
players wanted to do it and feed analog signals to the preamps.
But now, after nearly a decade, we finally have fully digital
pathways between universal players and preamps. using DenonLink 3,
I'm able to feed SACD DSD streams or DVD-A PCM streams digitally to
my preamp.
And while my new Denon AVP-A1 does an awesome job on bass
management, there is still the small issue of crossovers and signal
redirection from them.
Therefore, my current bass management scheme is more focused on
crossovers and post crossover bass management.
The Solution
Since I use an external
active crossover for my
Monoliths, the powerful
and ultra-clean DBX
DriveRack 4800. It
handles the signal from the sources first, passing all signals from
314hz up to the panels of the Monoliths.
All signals below 314hz and above 80Hz
are routed to the woofer amplifier for the Monoliths, the signals
below 80hz are then routed to the
Subwoofer.
The center channel SL3XC is
also handled by the DriveRack 4800, and it routes
all signals above 314hz to the SL3 panel element, all frequencies
between 80Hz and 314Hz are routed to the mid-bass Line Array and
finally, all frequencies below 80Hz are routed to the Subwoofer.
Since the 4800 is a single box, all the low frequencies for the
subwoofer are summed in the box and routed to the IB along with the
summed LFE inputs from the preamp.
The rear surround channels are also processed through a different
speaker processor, a
DBX
DriveRack 260 in this case. It also applies
time delays and EQ to the Sequels.
The subwoofer signal is fed from the output of the 4800 after
going through
parametric equalizer and limiters (to protect the drivers). This provides the fine-grained control over the
inevitable low-frequency room anomalies that affect any subwoofer in
most any room.
Notice that the LFE output from the preamp is also processed to
provide 13ms of time delay for the tactile transducers. This keeps
the butt-shaking time-aligned with the acoustic output of the
subwoofers. A limiter and compressor also protect the couch as well
as the sensitive listeners backsides.
Further details on my DriveRack setup are at this
thread on the ML owners club.
While I am a firm believer in the benefits of active crossovers
and multi-amping, it also introduces complexity into the equation.
I calculate I have more than 95 controls per channel I can adjust.
Just for the speakers along the front, we are facing more than 300
adjustable parameters. And the interesting thing is that many of
them interact a good bit.
On the right is the high-level connection diagram (click on it
for a full size image)