My system consisted of Cambridge audio c500, 2 p500 (biamped) and b&w 602 s3. I was completely happy with it but read so much about how nad's are ideal w/ b&w's that when i saw a used one for sale that i snapped it up.
I notice when i biwired the nad i hear an unbelievable difference. More so than when i bi-amped my ca's. THere's way more bass... It's so noticable that i didn't even have to do an A-B comparison test to notice it.
Left channel: A speaker wire connected to the left "Speaker A" binding posts, and a speaker wire connected to the left "Speaker B" binding post, both speaker wires connected to my left speaker's 4 speaker posts with the binding posts taken off. So "Speaker A" is powering the high and mids, and "Speaker B" is powering the lows.
Right Channel: same as above, but with right instead of left
NAD: Turn on both "Speaker A" and "Speaker B"
I'm thinking that there's more behind this unbelievable difference. I asked an engineer/audiophile friend of mine about this and he told me that he thinks because when i turn both my speaker A and B on, it's running in parallel, and therefore my 8ohms speakers basically turn into 4 ohms speakers, thus making the c370 send more current through, thus giving me this huge bass improvement. I know the NAD is supposed to have ISC which is suppose to defeat this, but maybe since its running in parallel, ISC isn't working properly? Anyways, he warned me that i was overextending the nad by doing this and this would lead to a shorter lifespan.
This is embarassing but i came back home to hear the difference one more time b/w normal wiring and biwiring, and i don't hear such a big difference anymore.... i'm not sure what happened... i'm afraid i might be imagining things.
On another note, i'm willing to give my take on the Cambridge Audio's versus the NAD if anyone will still trusts my ear....
The first day i was comparing NAD to the Cambridge Audio, i wasn't blown away. I noticed that the music coming out of the NAD was more defined and had more depth, but i was still seduced by the CA's brightness and detail (maybe wrong terms?). THe NAD sounded better w/ rock, but the CA's just sounded more intimate with small jazz. Jazz on the NAD sounded like i was listening in a concert hall, while on the CA"s fuller sound made it more like a small club. As well it just seem to me the NAD lacked the bass of the CA's.
Day 2, i tried a jazz track with just piano and bass.... perfect cause i can just concentrate on sound with these kind of tracks, not be distracted with too many instruments. And suddenly i noticed that the CA actually was not as defined/tight on the bass, it was boomy, while the bass from the NAD was actually really tight and defined. In addition, The instruments just sounded more real on the NAD. I started listening to the tracks from the day before, and with my new revalation, i started to prefer the nad much more.
Now, just for kicks, i tried the Cambridge Audio C500 preamp with the NAD, using the c370 just as power amp. All i can say is wow! Voices with this combination are just more natural. On the NAD alone, voices sound like the singers are singing through a filtered microphone, i think this is why the nad sounded like i was in a concert hall vs a small club in day 1.
I'm definitely keeping this setup! Huge improvement! I just love the sound of my system now.
If I understand you correctly one channel drives one speaker. You have effectively moved the jumper that parallels the woofer and mid sections from the back of the speaker to inside the amplifier (The A and B speaker posts are internally driven from the same amplifier channel).
So there is no change in load, no change in impedance you have just bi-wired. There is no damage possible if I have described your set-up correctly.
As to improved sound, many people think bi-wiring is a good thing, myself included. I have listened to several systems that were auditioned with and without bi-wiring. On some it had next to no effect on others it made things quite a bit better. I have never heard anything get worse when bi-wired so the only risk is to your wallet.
As to changes from one day to the next:
1. Are these things broken in? Pieces that have been un-used for a while often need to break in again.
2. Is there a possible difference in power line voltage or noise? My system just sounds better late at night when all the electrical industrial activity has stopped.
3. In each case had the equipment been turned on for the same amount of time? Many pieces change their character when warmed up.