I was using a REL/CLS setup to test out the process, whilst I was restoring the Apogee speakers. The REL allows you to run it using it's own xover, or in bypass mode for situations like home theatre, where the signal has already been digitally split; hence, no analog xover is needed.
In order to keep the original message from becoming too complicated, I ommitted my setup scenarios and the resulting speaker interactions. Originally, I used an analog preamp with the REL and CLS running in parallel, as I did not want a xover-effected signal going to the CLS for purity reasons.
Here is the setup and results:
In my case I set the first FA to 56hz or less, 96db slope, and had it output via SE to the REL, which was set to bypass it's own analog xover and amplify the signal directly. The second FA was set at 56 hz and above, 96 db slope, and had it output XLR to the Rowland amps, driving the CLSs.
When I fired it up, it actually worked! But, there were some problems. The CLS and REL were completely out of sync and the sound had a hard, metalic quality that I did not like. When I read the RDP manual, I discovered the problem. It defaults to 20-bit words to work with typical processors, but recommends 24 bit words for more advanced (hi-rez) processors, like the DF-35. The RDP also has dither (noise that smoothes out the quantization noise caused by converting high-bit signals (24 or higher) to low-bit (16) during the recording process) and an excellent parametric equalizer.
I set the RDP to 24-bit word and the sound changed so dramatically for the better for reasons that I am still not sure of. I then instucted FA #2 (controlling the CLS) to delay the signal by 6 cm. It worked perfectly - the CLS and REL were now playing in sync - amazing!
Also, one of the CLS speakers plays a little louder than the other. I first instructed the RDP to compensate for this (digitally!) and it also worked - the image was centered. However, I realized that the subwoofer was also getting the same adjustment AND that each FA in the DF-35 could also do the same thing! So, I reset the balance on the RDP-1 and instructed FA #2 to decrease the louder (left) speaker and the image was still centered!
Also, each Filter Amplifier (FA) in the DF-35 has a neat feature for subwoofers; if you set the switch on the back of any FA to "sub" position, it will actually generate a mono version of the stereo digital signal.
This is especially ideal for those who use one subwoofer with only one corresponding input, or those who use one mono amp for a single sub and don't want to fork out the money for another amp/sub, or those who want to use two subs and want identical signals sent to each one. If you still want stereo sub ops, just set the switch back to normal - it's that simple!
So, the digital xover (even with a xover-less CLS) did make a big difference. With the multi-driver Apogees, these differences should be more dramatic.