I went to the HiFi show at Heathrow and was very impressed with a demo of a system by Overkill. There were three main technologies used in the system that I believe made it sound great:
1) A digital cross-over by DEQX
2) Bi-amping
3) Speakers using Manger drivers
An entry-level system with these core components from Overkill costs about £13,400 (Angel speakers £8000, DEQX £3000, 5 channel Butler tube amp £2400) - well over my budget.
I've since done quite a lot of research on all three of these technologies trying to think of how I could advance my own home hifi. In this post, I just want to blog about how cool the DEQX PDC 2.6 is. There's a detailed review over at 6Moons.
The core idea is to seperate the audio signal while in the digital domain and to send each driver it's own signal and drive it with it's own dedicated power amplifier. It's not a new idea. I believe Meridian pioneered digital speakers quite a long time ago.
What's great here is that you can attach a measurement microphone to the DEQX box and do some clever tailoring of each driver signal. You can perfectly phase align all the drivers and flatten the frequency response. You can then add digital room correction to compensate for, say, a room resonance mode. Very cool!
This is the future! Using a feedback loop to do some clever digital processing, you can make some average equipment sound fantastic. It's possible to do this with a lot of fiddling using something like Smaart Live and a Behringer DCX2496 but it's not nearly as flexible and as well integrated.
Another alternative is to do all the digital processing on a standard PC. A good place to start reading about it is Duff Room Correction. However, to do all the things DEQX does will require cobbling together lots of little bits. Could be fun but not as usable.
One suprisingly difficult issue is volume control. Ideally, you want to control the volume after the DAC. Digital volume control leads to higher noise and a loss of dynamics. The problem is that DAC's are usually designed to be attached to a preamp or mixer and don't usually offer volume control. Some audiophile DACs do like the Benchmark DAC1 but they're only two channel products.
So what's needed is a DAC with a PC interface (like a firewire connection and a 6 channel ASIO driver) and a volume knob that controls op-amps across all the analogue outputs. So far, I haven't found such a beast to exist. The only alternative is to use some of kind passive volume control after the DAC but before the power amp. For now, there's not much choice.
Or you just get the DEQX PDC2.6P which does indeed have an analogue volume control via a remote. It's one cool little piece of kit I would love to own. I've exchanged some email with DEQX and they're even considering adding a USB audio connection for connecting directly to a PC music source in a subsequent release. That would make it just about perfect.