Jonathan's Site

Audio / Video / Cars / Gadgets

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)


DriveRack 4800MX882

System diagram
Click for full size image