bi-amping question

Discussion in 'AV Receivers' started by Jantzen, Aug 15, 2003.

  1. Jantzen

    Jantzen Stunt Coordinator

    Joined:
    Mar 8, 2001
    Messages:
    97
    Likes Received:
    0
    Trophy Points:
    0
    I currently have an older Sony 333DA ES receiver rated at 80W / channel.

    I will be getting a used Rotel 976 amp to power my front soundstage. This amp is rated at 6x60W but it can also be bridged to 3x150W or 5x70W.

    I currently have a pair of Energy e:XL-26 floorstanding speakers as mains that are bi-amp/bi-wire capable and an e:XL-C center that is not. The mains are currently bi-wired from the Sony receiver...

    My original plan was to run the new Rotel amp at 3x150W and wire from the amp to the speakers like I have it now, i.e., mains bi-wired and a single cable run to center speaker.

    But I was wondering if there is a benefit in doing this...

    Since the amp can also run at 5x70W - I was thinking of bi-amping my mains instead. The problem is (1) I don't know if this will be better/worse/or the same as just bi-wiring the mains at 150W a piece and (2) I only have one set of preouts for the main L/R fronts and I'm not sure if it's ok to split the signal with a y-adapter,etc. from the preouts on the receiver to the inputs on the amp.

    I hope this makes some sense...

    thanks
     
  2. RichardHOS

    RichardHOS Second Unit

    Joined:
    Mar 11, 2003
    Messages:
    454
    Likes Received:
    0
    Trophy Points:
    0
    Are you sure that amp can run 5x70W? I thought it could only run in 6x60, 4x60 + 1x150, 2x60 + 2x150, and 3x150 (assuming all channels are used).
     
  3. Jantzen

    Jantzen Stunt Coordinator

    Joined:
    Mar 8, 2001
    Messages:
    97
    Likes Received:
    0
    Trophy Points:
    0
    The 976 brochure says...

    In six channel mode, the RB-976 will deliver 60 watts RMS each (20 Hz to 20 kHz @ 0.03% THD into 8 ohms). In five channel mode (one channel quiescent), power increases to 70 watts RMS each measured by the same standards. Amplifier pairs can be bridged to develop 150 watts x 3 for almost half a kilowatt of output power.
     
  4. Jantzen

    Jantzen Stunt Coordinator

    Joined:
    Mar 8, 2001
    Messages:
    97
    Likes Received:
    0
    Trophy Points:
    0
    UPDATE:

    Ok I found this info at the Rotel site...

    So it looks like I can use the "link" feature of the amp to duplicate the inputs from the A input to the B and/or C inputs. So the Y-adapter question is a non-issue if I bi-amp (I think).

    FYI - The mains are 8 ohm rated up to 200W and are bi-wire/bi-amp capable. The center is 8 ohm rated up to 100W and can NOT be bi-wired/bi-amped.

    So if I read that info from Rotel correctly then the question now becomes... Would you run the amp???

    1. 5x70W w/ bi-amped mains - I would run the L/R pre-outs to A and set the link switch at B to duplicate the A L/R inputs. I would then run 4 seperate spaker cables from the amps A and B outputs to the main speakers high / low binding posts, i.e., bi-amped.

    I would then just run the center off of one channel of the amps C section at 70W since the center is only rated to 100W anyways.

    or

    2. 3x150W w/ bi-wired mains - Bi-wire mains and single run to center, since the center can't be bi-wired.

    Sorry I'm new to seperates - so I don't know which way to go and if there are issues with the amp in either config since I have 8 ohm speakers...

    Thanks again.
     
  5. RichardHOS

    RichardHOS Second Unit

    Joined:
    Mar 11, 2003
    Messages:
    454
    Likes Received:
    0
    Trophy Points:
    0
    Interesting, so I guess the limitation on power output is due to the power supply then. Probably means any one channel has a fair amount of headroom under normal listening conditions... which is always a good thing.


    A couple of short comments. If you're going to biamp, then you'll receive the most benefit from active biamping, which means removing all or part of the speakers' internal passive crossover components and in their place adding an active crossover upstream of the amplifier. Passive biamping will increase power, and might have some limited benefits, but generally isn't much more useful than simply using a single channel of equivalent power to the combined biamp channels.

    As for biwiring, my opinion is that it doesn't do anything other than lower the DC resistance of the cable (assuming you use two of whatever you would have been using anyway). Other than that, I see no benefits.

    So, my suggestion would be to aim for active biamping if you are serious about getting the most out of your speakers. Otherwise, I'd suggest running it in 3 x 150 and biwire only if you have extra wire or are bored one day. [​IMG]
     
  6. Dave Milne

    Dave Milne Supporting Actor

    Joined:
    Jul 2, 2001
    Messages:
    568
    Likes Received:
    0
    Trophy Points:
    0
    Richard,
    I agree that active biamping provides the most benefit. However, converting from the factory passive crossovers to active is a serious engineering task. Just knowing the crossover frequencies and slopes isn't enough. Often passive crossovers contain elements for driver impedance compensation, baffle step correction, response shaping, etc. Even an apparently textbook passive filter can have other effects due to the interaction among driver impedance, coil DCR, capacitor ESR, etc.

    Unless you have good modeling software and access to the precise driver characteristics (or the tools to measure them) you're probably wasting your time. Personally, if I'm going to put that much effort into a speaker, I'll start from scratch.
     
  7. Jantzen

    Jantzen Stunt Coordinator

    Joined:
    Mar 8, 2001
    Messages:
    97
    Likes Received:
    0
    Trophy Points:
    0
    I think the active bi-amping is a little beyond what I was looking to so - so I'll go with the 3x150W approach.

    Thanks for the input.
     

Share This Page