Passive bi-amping works ?

I have a pair of Legacy Classics I am driving with a Sunfire Cinema. I have tried driving them with single channels then biwiring and then passive bi-amping and there was a steady improvement in the sound. More highs and lows with each change and better clarity and definition. A rather interesting thing, which I can't explain is that the speakers response got much flatter when I went to vertical biamping (as confirmed by my SPL meter). I had a +3 to +5 dB boost over much of the bass range and after the vertical biamp, it's now +-1.5 dB down to 40 Hz. Now I'm just waiting for the funds to go with Active crossovers...

Ivanj
Thank you for that explanation. I have done quite a bit of reading up on the web on passive biamping and most of the discussions of improvements seemed to focus on the benefits to the higher frequencies due to lessened intermodulation distortion with the lower frequencies, so I really wasn't expecting the result to be apparent in the bottom end. (Although I'm very, very happy with the response I got).

Greg