Sub power/bass mgt with speaker level connection.

Discussion in 'Archived Threads 2001-2004' started by Steve_Ma, Mar 4, 2002.

  1. Steve_Ma

    Steve_Ma Second Unit

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    I plan on experimenting with switching to the speaker level connection rather than the LFE out, in order to play with my sub's x-over settings and placement. The sub is a powered (120W) B&W ASW1000. AVRec is a Marantz SR7000.

    1. In my AVR, if I set my mains to large and sub to no...What happens to any bass material with the surrounds/center? DO I leave them to small and does their bass get re-routed to the mains/sub?

    2. MY AVR puts out 100W per ch. If my sub now drives my sub and my mains, will this be too much for my 120W sub? Is there any benefit derived from using the power coming from my AVR and the sub together or does the AVR's power simply get wasted?

    Thanks,

    --Steve
     
  2. John Kotches

    John Kotches Cinematographer

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    Steve,

    If you define the speakers as large, you will be "wasting" the portion of the receivers power that is used for amplification of frequencies below whatever crossover point you select on the subwoofer.

    For example, if you set the subwoofer crossover to 80Hz, and run the speakers large, your receivers amplifier will still amplify below 80Hz, and the subs crossover will also amplify from crossover frequency and below after a stepdown from speaker level to line level.

    The lower the frequency, the more power is required for driving to a given SPL. As such, running speakers full range, you might very well find that your receiver has less "usable power" than with the speakers running bandwidth limited aka small.

    It's certainly a worthwhile experiment to see if it gives you pleasing results, if you don't like them you've learned something. If you like them, you've learned something.

    Also, test levels carefully with a disc like Stereophile's Test CD or a VE or AVIA frequency sweep. Be warned you will see peaks and dips from room interactions.

    Hope this helped.

    Regards,
     
  3. Steve_Ma

    Steve_Ma Second Unit

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    Thanks John,

    So the Rec will still be amplifying the mains above the X-over, and the sub will amplify below? Which makes me wonder about having less juice for the mains, and placing more of a load on the sub's amp. Not sure that I like that as I'm happy with the power the SR7000 sends to the mains (for now).

    Maybe I'm over thinking/over tweaking. I suspect that any change I'll experience with regard to a lower x-over (the SR7000 = 100), will probably be minimal compared to the change due to placement alone (for better or worse).

    Thanks again,

    --Steve
     
  4. BruceD

    BruceD Screenwriter

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    Steven,

    I don't know how the B&W ASW1000 sub handles a high-level speaker cable input with respect to your mains and the xover frequency, or a low-level input and output with xover.

    Does the sub manual explain this well? see below.

    Your sub might also support low-level interconnect cable pass-thru in your setup if the Marantz SR7000 AVR provides main L&R pre-out and main L&R amp-in jacks.

    Here is how:

    1) Main L&R pre-out from AVR -> sub L&R input (RCA low-level)

    2) Sub L&R output (RCA low-level)-> AVR L&R amp-in (xover set on sub)

    3) Main L&R AVR speaker out (high-level) -> main L&R speakers

    Anyway, I use this same setup scheme as you, except with low-level interconnect cables between the processor, an electronic xover, and the amp channels.

    You could also use low-level interconnect cables with an electronic xover in your setup if the Marantz SR7000 AVR provides main L&R pre-out and main L&R amp-in jacks.

     
  5. John Kotches

    John Kotches Cinematographer

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    Steve,

    In your wiring scenario, speaker level to sub, sub internal crossover to subwoofer and speakers, the receiver will amplify a full range signal for the mains.

    Your reply (receiver handling above crossover (maybe it's a typo?) is not correct.

    Regards,
     
  6. Steve_Ma

    Steve_Ma Second Unit

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    Thanks Bruce/John,

    I think I'm getting there. John, I was looking at the following quote when I made my previos mistake:

     

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