Can I Attach Sub to HiFi when watching DVD?

Discussion in 'Subwoofers' started by Chris23, May 16, 2004.

  1. Chris23

    Chris23
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    My stereo hi fi amp has outputs for 2 sets of speakers that I can drive at the same time.
    We listen mainly to music but want to be able to play home cinema DVD's with the heaviness that only a sub gives. I have a DVD connected to my HiFi amp.
    Is there some way that I can connect a sub to my second set of speaker outputs for when we are watching home cinema & thus leave my stereo system uncompromised?
    I am not allowed any surround speakers due to wiring & siting issues. I admit that at the moment the use level would not justify rears & centre speakers and I could not match the sound of my existing stereo pair.
     
  2. Ian J

    Ian J
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    Assuming by your comments that you don't watch many DVDs, why not keep the sub switched off until you want to use it.
     
  3. Nimby

    Nimby
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    Chris23

    I cannot imagine listening to music without my subwoofer and you can certainly augment DVD film watching with a subwoofer in a stereo system.

    I'll presume you have (or intend to buy) an active subwoofer.

    I'd connect your subwoofer using speaker cable to the high level input terminals of your subwoofer. (Assuming it has them) You can use your second set of amplifier speaker terminals to connect the subwoofer.

    It is very important that your subwoofer only covers the frequencies below your main speakers. Or the sound will become muddled and muddy due to the overlap in output from both speakers and subwoofer competing with each other. Most active subwoofers should have a frequency cut-off setting to avoid this overlap.

    I find we watch films with a couple of notches higher on the subwoofer gain (volume) control than the normal 'flat' position for music.

    Ideally the subwoofer crossover (or cut-off filter) should be set to achieve a flat responce with your main speakers using a RadioShack SPL meter and test tones. Though with patience you can achieve satisfactory results setting the subwoofer by ear. It can never be quite as good as checking it with an SPL meter.

    All the above depends on the quality of your subwoofer and your speakers for satisfactory sound quality. By "satisfactory" I mean your own satisfaction. If something works for you then that's certainly good enough. :)

    Nimby
     
  4. Chris23

    Chris23
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    Thanks. I hoped the above is what you would say.
    Is it safe for me to assume that as low frequency sound is not directional it does not matter which channel I take the 2nd speaker feed from? I can't put both left & right high level into the subs that I have seen as they only have a one channel input.
     
  5. Nimby

    Nimby
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    If you feed the subwoofer with only one steeo channel (L or R) you will only get the bass from that channel. There is a surpising variation (particularly in films) between the bass signal coming from each stereo channel. For example when a tank rolls across the battlefield scene. If the stereo speakers are capable of enough depth they may help the sound to pan across. But if not there might be odd effects from feeding the subwoofer with only one channel.

    Normally (for AV/HT surround sound purposes) subwoofers are fed by a single mono phono cable to a single phono socket. But this (bass only) signal is derived from something other than the normal stereo (left and right) channels.

    Ignoring the fact that a single subwoofer can only provide mono sound. There are subwoofers out there with two sets of high level terminals. (Left and Right) If your purpose is to use a subwoofer with a stereo system I think it would be worth finding a sub with both L & R speaker terminal inputs. Subwoofers with L & R high level inputs do not mono the two signals. But keep them seperate until after the amplification stages. After which they become mono to drive the subwoofer's single loudspeaker drive unit.

    An expensive alternative for stereo systems would be to have two single channel subwoofers. One for the Left channel and one for the Right. But it adds to the complication and doubles the expense. As well as needing further permissions from your better half. Many here would agree that one good sub beats two lesser ones hands down.

    Nimby
     
  6. Chris23

    Chris23
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    Thank you.
     

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