The next step was to buy a SGR EL30S power amp and a DEQX. The idea was to provide seperate amplification for the midrange/tweeter via the Cary, with the SGR solid state amp looking after the bass cabinet, with the DEQX working as a digital crossover, but also with the ability to provide room correction, speaker correction, group delay, etc.
Sadly, despite my best efforts I could not get the DEQX to sound good. There is something about redigitizing the sound which is horribly destructive for resolution and dynamics. It is without doubt a powerful development tool, but not something I could leave in my system long term.
I used the DEQX to simulate ideal crossover points, then ordered a Marchand XM-44 crossover. This was MUCH better - so much more transparent. But despite all this, the bass was still not right. So we decided to open up the speaker to have a look.
As you can see, there is an internal woofer mounted at 45 degrees, firing into the back of the external woofer which is mounted on a baffle (not shown). Strangely, the internal woofer comes off the binding posts FULL RANGE, while the external woofer goes through the crossover. The crossover appears to be a 1st order low pass with a couple of notch filters in place. This bizarre arrangement was responsible for muddying up the bass!
At least I could see where they had spent the money. The construction of the cabinet is incredible - double ply, then lined with lead, then stuffing material.
The obvious step would be to disconnect and remove the internal woofer, and bypass the crossover so that the bass cabinet is fully active. By this stage I had complete independent control over each driver in my system, so it was a simple matter of adjusting the crossover and taking new sims with the DEQX to get it to sound right. The system gained another useful step in resolution, but there was something that was still nagging me.
This is a shot of the backside of the external woofer. It is a SEAS CA 25 ACA, which you and I can buy as a replacement part for USD$70-80. Note the shallow voice coil, the stamped metal basket, and the generally flimsy construction. The Xmax can't be more than 10mm! Another bizarre design choice - why put such cheap woofers on a speaker that retails for USD$60k, especially when you have gone through the effort of building an incredibly solid cabinet for it?