I'm doing pretty much what you describe with my SHD. My current speakers are a bit unusual, which made it a bit easier. They're Acoustic Reality Tetra 3D speakers, which are in 2-pieces. A top M/T module which is sold as a standalone speaker, and then a base woofer which also includes additional xover components to high-pass the top M/T. This arrangement made it easy to bypass all of the xover components in the woofer module, and use the SHD as the xover to driver the woofer and M/T module separately.
I have a couple of questions...
My VR-4 Gen III HSE speakers have acoustic fourth order crossovers at 150 Hz and 2.6 kHz. As there are separate binding posts on each cabinet I assume the bottom "crossover" is simply a 24db per octave low pass filter and the upper crossover incorporates a 24db per octave high pass filter along with the 2.6 kHz crossover between the midrange and tweeter. Is my assumption correct?
The miniDSP SHD can be used as an active crossover. Is there any benefit to using a 150 Hz 24db low pass filter to the ICEpower monoblocks feeding the lower cabinets and a 150Hz 24db per octave high pass filter to the PSET monoblocks powering the upper cabinet? And, if I do this, could I modify the upper cabinet/remove the lower cabinet passive crossovers in the speakers? Would I need to?
Thanks,
Martin
Some points:
- it's unlikely that a 4th order acoustic xover actually uses a 4th order electrical circuit. The natural roll-off of the driver is usually included as part of the acoustic filter. this is more true of high-passes than low-passes though, as 150 Hz might be low enough that the woofer's top-end roll-off doesn't help much. The upshot though is that you almost certainly want to measure or at least model the transfer function of the xover circuit - both the high-pass and low-pass.
- it may not be possible to simply bypass the high-pass section of the midrange crossover. there is no universal way of designing an xover filter, and if it's wired so that the low-pass elements come first in the circuit, you can't simply remove the later high-pass elements as they will interact.
- obviously, bypassing the xover requires physical modification of the speakers. The woofer is probably the easier piece, and might simply involve running wires directly from the binding posts to the driver, which is easily reversible. You'll have to evaluate the potential impact on resale etc on this type of mod.
- the benefits of doing this include 1) efficiency gains by bypassing the insertion loss in the passive xover (more typically realized in the M/T section as they are padded down to match the woofer) 2) ability to rework the xover into something that may work better (i.e sometimes commercial speakers use higher xover frequencies than ideal to provide better power handling).
Taken on balance, for what is likely a well-designed speaker like the VR-4, I'm not sure I'd find the potential advantages all that compelling. Global EQ and Dirac provide most of the benefits, and unless the W to M xover was mis-designed for some reason, I'd expect the benefits to be of the incremental nature.
In my case, I was pretty unimpressed with the performance of my speakers, despite the pedigree of what were at the time top-end Scan Speak drivers - muted and veiled would be how I'd describe them. (I got them really cheap 2nd hand, and got WAF approval to have 6' tall pyramids in our living room, so jumped on them). After bypassing all the passive components in the woofer module, the speakers were completely transformed - they now sound fantastic. They really exhibit that 'classic Scan-Speak sound' - which is usually described as warm, rich and musical, with the added benefit of being able to more easily/directly tailor the bass response.
