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Question for 'Anxious' (Ken)

Discussion in 'Pro Audio Equipment' started by Cucco, Feb 15, 2007.

  1. Cucco

    Cucco Distinguished Member

    Ken -

    I'm curious about something regarding my 2.5i's. For a while, I had them bi-amped using 4 of the 5 channels from a Rotel Amp. I recently purchased a B&K amp (2 Channel) to complement my setup and went to bi-wire. I really prefer the sound of the biamping however (it seems to have a more present/full mid/low-mid that way).

    Given that the B&K has roughly 10% more power than the Rotel, would it be better suited to drive the low frequencies?

    I normally wouldn't concern myself with which amp to drive which, but the B&K is smoother than the Rotel and I could see where the top end amplified by the B&K would be beneficial. In otherwords, do you see any issues running it this way, electrical or otherwise?


  2. anxious

    anxious Guest

    Hey Jeremy... how things?

    I should start off with a caveat: I've never been blessed/cursed with the ability to hear big differences between comparably-powered amps. (This is the subject of considerable self-loathing, but I have to be honest....) So, you should take my comments in that context.

    I can't think of any reason why what you propose wouldn't work fine. The obvious issues of matching gain and polarity apply, but that is all. (I'm saying that for other readers... I know you know!) I don't believe there is a common ground, or anything internal signal interaction that will give you any trouble.

    Drop me a line to let me know it works out, and catch me up on life.


  3. Cucco

    Cucco Distinguished Member

    I'm glad to hear your admission about amps! I generally am not one to be able to pick out large differences either. To me, the difference between the Rotel and the B&K are pretty plain though. The Rotel tends to be a tad exposing (much like the 2.5i's) and the B&K seems a tad smoother (almost like a warm yet extremely powerful tube amp).

    I'll try it with the Rotel on bottom and the B&K on top despite the power differential and see. If worse comes to worse, it would make the mid-bass sound lean. I do have a REL sub to go along with it, so that should keep that bottom end there.

    Thanks for the info and the reassurance! I'll let you know how it turns out.

  4. anxious

    anxious Guest

    Yeah, power allocation between woofers and tweeters is a funny thing... to me, it doesn't so much matter what the averages are, it's those peaks that count. (OK, in sound reinforcement, you need to be concerned with heating issues, but that should never be the case in an audiophile situation, eg- music with even a few dB of dynamic range.) So, I agree with you... put each amp where it works best.

    But, I will add a gratuitous propellerhead comment: when amps DO sound different, (or wires or whatever), I'm pretty sure that its all about interaction with the actual load. Thus, one amp might be grainy with one type of impedance curve, while another will be smooth as silk. Reverse the loads, the character changes.

    Impedance curves are the dirty little "secret" in many situations. For example, the frequency response of, oh say, a SM57 looks totally different working into a 600 Ohm input vs. a 3K Ohm input. Add the rollercoaster bumps of a speaker's Z, and you have endless possibilities.


  5. Cucco

    Cucco Distinguished Member

    Good point. I didn't even think about that. I'm assuming the impedence curve will actually change if driving the speaker with 2 amplifiers versus one. I would assume that the overall curve would be skewed down a fraction of an ohm for the very reason that there's at least a few less pieces of metal that the signal needs to travel through.

    I just need to actually give it a try now. Of course, the big problem is I just dropped some serious money on a pair of Tara Labs bi-amp cables and now need to look at a quad pair of regular cables now...oh well, it's just money. :wink:
  6. anxious

    anxious Guest

    Usually, each amp in a bi-amp situation sees a slightly higher impedance than a single amp would. This is because the non-bi-amped crossover has multiple electrical sections in parallel, while the bi-amped does not. Not always the case, and varies by frequency, but its a fair bet.



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