set up question

Discussion in 'Hi-Fi Stereo Systems & Separates' started by st170dan, Feb 12, 2014.

  1. st170dan

    st170dan
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    hi, been wondering something out of curiosity. if i take the preamp on my hifi amp and connect the left channel to one sub and the right channel to a second sub will i have double the "output" (using the term loosely to mean volume/bass/power). or will i have the same output but with half going to each sub?
     
  2. BlueWizard

    BlueWizard
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    It depends on what you mean by DOUBLE. Twice as loud, no, but definitely louder with more weight and impact at any given volume.

    What amp do you have? Is this a Stereo or Surround Sound system? Does the Amp have a SUB OUT connection on it.

    Most Sub Outs are Mono, the left and right amp channels have been merged together. In your case you will have Stereo Subs. Generally, it is the nature of deep bass to sound like Mono even when it is not. In your case you might get a bit more Stereo Imaging in the deep bass, but the effect will likely be minor.

    Also consider that in movie sound tracks, there is a specific channel for the deep bass, the LFE (Low Frequency Effects). Those deep bass effects will not be present in the Stereo portion of the sound track. Now, I listen to movies all the time in Stereo, they sound fine, but you don't get the LFE. However, if you have Surround Sound, then the LFE is sent to the Sub Out. I would be possible to split the Sub Out between two Subs, and that would not likely to be a problem.

    Most likely the Inputs on the Subs are 47k ohms, if you put two in parallel, then the combined impedance drops to 23.5k ohms, that is still sufficiently high, but if you add more inputs, or more loads, the combined impedance starts to drop pretty low. Generally speakers, one output does have the capability to drive two inputs. But that is about the limit.

    So, if you have an AV Receiver, the likely the SUB OUT can drive two Subs, simply get a splitter "Y" connector.

    If you have a stereo system, then, yes, very likely the pre-amp could drive two Subs. However, it depends on how the Pre-Amp is configured. If the Pre-amp to Power Amp has a jumper joining them, then you are actually driving three load - 2x Sub and 1x Power Amp. I'm not sure how that would work unless I had detailed specifications on the amp and the various inputs. Other types of Pre-Amp outs, are a separate buffer. The signal branches off through the buffer, and the other brand simply feed the power section internally. So, the Power amp load is not added to the External Pre-Amp outs.

    Again, there are a lot of missing details and a lot of assumptions I've made. Tell us specifically what amp and speaker and sub you have (or are planning to have) and we can perhaps give you more accurate details.

    Steve/bluewizard
     
  3. st170dan

    st170dan
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    Hi, the amp is a Cambridge audio amp, part of a hifi separates system. It doesn't have sub out, just a pre amp. I don't know much about AV electronics so was curious if it was worth doing.
     
  4. BlueWizard

    BlueWizard
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    Which Cambridge Amp?

    Steve/bluewizard
     
  5. wilco1uk

    wilco1uk
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    Without knowing what amp (and the manual should tell you this anyway), you may find that by plugging something into the pre-out it might disable the integrated amp (the cambridge) power amps, so you could lose your stereo speakers output from the cambridge.
     
  6. st170dan

    st170dan
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    Not sure I get that. It's an a5 integrated amp.
     
  7. wilco1uk

    wilco1uk
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    Yep, but I'm guessing that you are hoping to use the Cambridge to feed the main speakers and use the pre-outs to feed the subs at the same time.
     
  8. st170dan

    st170dan
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    for donkeys years now i have been using the amp to power the speakers and using the pre out to power the sub. i used to have it set up biwire but after reading on here i changed it to normal. i did have a play the other night and hooked up another sub - it worked but i couldn't tell much difference tbh.
     
  9. BlueWizard

    BlueWizard
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    The Pre-Out does not appear to use a Jumper -

    http://i639.photobucket.com/albums/uu113/hendie1806/ampback.jpg

    So, assuming when you plug into the amp, the internal amps are kept on-line, then likely you can use the Pre-Amp out to drive two Subs. Notice I said Likely. To some extent it depends on whether the Pre_amp outs are buffered. If, internally, separate Op-Amps drive the Pre-Amp out, you should have no problem. Even if the Pre-Outs are not buffered, each channel will only drive two loads, one the internal amp and the other the Subwoofer, likely that is not going to be a problem ...Likely.

    Look at the specs or at the manual for those subwoofer, or look it up on-line. If the input impedance is rated at the very common 47k ohms, then likely you are OK. If it is rated at 10k ohms, then I can't be sure. Likely it will still be OK .... likely, but I can't know for sure.

    The standard Line Level input is most commonly 47k ohms, but I can't say in your specific case because I don't know what Subwoofers you have.

    Steve/bluewizard
     
    Last edited: Feb 15, 2014

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