EW:
Flip's question and my explanation goes back to his post regarding the BA-5000/B&W speakers, perhaps you didnt read it:
Basically, you can either vertically biamp of horizontally biamp. As I mentioned before, you can do a search Online to read more info on it, pros & cons etc...
If you were to use two different amps to biamp, its preferable to use the higher wattage amp to drive the woofers of both speakers and the lower wattage amp drives the tweeter/midrange in both speakers. This would be an example of horizontal biamping.
If you were to use two amps that were identical, such as two 9090DB's, then in my opinion, vertical biamping is the preferred configuration. One 9090DB drives the left speaker, the other 9090DB drives the right speaker. The 9090DB is a receiver but its preamp/power amp section are separable, so switch both 9090DB's into power amp mode and then a Sansui preamp with two pairs of outputs would connect to each 9090DB. (otherwise, you'd have to adjust the volume two times- the 9090DB volume on the right spkr and the 9090DB volume on the left spkr, and turn them up equally so the volume coming from each speaker is the same and one isnt louder than the other, comprende'? The preamp with two pairs of Outs takes care of that problem nicely, one single volume control on the preamp controls the overall volume. If you use a preamp with only one pair of outputs, then you'd need to get a splitter cable to send the output signal of the preamp to each 9090DB. Not a big deal to do that, but a preamp with two outs is certainly a very useful feature- and now you have a good justification to treat yourself to buying a nice CA-2000 preamp on Ebay (as well as a 2nd 9090DB)
Note the difference between the two types of biamping. With horizontal, one amp has to do the work of driving the woofers in BOTH speakers. But with vertical, each amp just handles the woofer in the one speaker theyre driving
When you connect each amp to the speaker in VB, it can look tricky because your amp has a left & right channel BUT, the amp is only driving the one speaker, so... how to connect the amp's right channel terminals when its driving the left speaker and vice versa for the other amp's left terminals driving the right speaker??
The connection is made as follows:
9090DB Left channel + to Speaker Left woofer terminal. Then 9090DB left channel - to Speaker Left's right woofer terminal. Then 9090DB right channel + to Speaker left's tweeter/midrange terminal. Then 9090DB right channel - to Speaker left's right tweeter/midrange terminal.
You then repeat this connection for the other 9090DB thats connected to the right speaker.
I imagine if you do a search Online, there will be diagrams of the connections which make it alot easier to visualize instead of writing it all out which I have nonetheles graciously done for you.
B/F