Hooking up a sub with only RCA and XLR

Discussion in 'Subwoofers' started by thatMikeguy, Dec 19, 2006.

  1. thatMikeguy

    thatMikeguy
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    I have a Slim Devices Transporter that has two RCA outputs and two XLR outputs. I use an Arcam AV8 on analogue direct mode to pass through the Transporter signal. However, I do not know how to get my sub to play in this configuration. Can anyone help? Is there an easy way to do this? I am likely going to be picking up the new JL Audio Fathom 113 in the near future and it has an XLR input and an RCA input but does not have a high level input. In the meantime (presently) I only have an LFE option on an old sub. Any help would be great!!
    M.
     
  2. Nimby

    Nimby
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    Why on earth would you want to use a high level sub connection with gear at this level? Do you drive your sports car with the handbrake on?
     
  3. thatMikeguy

    thatMikeguy
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    Nimby,
    Come on man you're killing me. If you are gonna fire off a comment like that at least educate me. I know virtually nothing about subwoofers (obviously) and am asking for help not ridicule. By your comment I assume you can explain why a high level connection is bad? Irrespective of that do you have an answer to my question. Please!
    Mike
     
  4. Nimby

    Nimby
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    Mike

    Let's assume that you know nothing about subwoofers then, despite your expensive tastes in these things. :)

    A subwoofer can be used in two ways. It can underpin a set of speakers using high level connections. The speakers play fullrange and the sub just plods along underneath the deepest bass that the speakers can manage. There is bound to be some overlap in frequency in the bass.

    The second option is to feed the sub and speakers a filtered signal. A crossover in the AV Receiver stops the deep bass going to the speakers and the higher stuff from going to the subwoofer.

    This second option has several advantages. By reducing the bass going to the speakers they lose a lot off their muddy bass. The muddy bass usually obscures the better qualities of a speaker. So now your speakers have moved well up the quality scale. They sound clearer and more dynamic and detailed.

    The speakers start to sing but now they lack the bottom end. So the subwoofer does what it is designed to do. It plays the bass for the speakers. It does so with incredible extension, dynamics, headroom and very low distortion compared with any affordable speaker.

    Connect your sub to the AV8 using the balanced XLR sockets. I found a fuzzy rear shot of the AV8 online and assume those are balanced XLR sockets?
    Now bypass the low pass filter in the sub and set the AV8 to a suitable crossover frequency in the menu. Usually around 80Hz but this will depend on the size and bass power handling of your speakers.

    If your original request was only asking how to run a sub in stereo (rather than surround mode) then you'll need the help of someone who knows something about the AV8. Which I certainly don't. If the AV8 lacks bass management in stereo then forgive this rambling waste of your time and mine. ;)

    If the AV8 lacks bass management in stereo mode then the only option I can think of is a stand-alone, active, line level, stereo crossover. To do what the AV8 can't. Cheap active crossovers exists. I use one myself in my stereo system. (click on my sig below) I use the Behringer CX2310. There are others working their way up to and well beyond your present expenditure level. The Behringer has balanced XLR sockets but no RCA.

    BTW: Don't you have dealer support? At this price level you certainly should have in order to maximise your returns on your large investments in AV gear.

    An experienced dealer could set up your system to make the most of its potential. Rather than the limited result you'll probably get just fiddling around on your own and hoping for the best. Some of the high price of this high-end gear goes into the expectation of dealer support for the purchaser. An ounce of experience is worth a ton of magazine learning.
     
  5. phurst

    phurst
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    The AV8 does contain bass management in Stereo mode. In the stereo setup options you can select 'Large + Sub' which feeds pure stereo to the left and right speakers and extracted bass to the subwoofer.

    You can also set the sub stereo level to trim the subwoofer output for stereo music.

    The only consideration when using the AV8 bass management is that the signal needs to pass through the processor's DSP and so the sound quality might be worse than in Direct mode. In Direct mode then no signal will be sent to the sub if using the LFE connection.

    Phil
     
  6. thatMikeguy

    thatMikeguy
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    Thanks to both Nimby and Phil. Unfortunately my question is exactly what you ended with Phil. I want to be running in Direct mode. The question then is if the source has both XLR and RCA outputs can I use the RCA to the AV8 (in Analogue Direct mode) and the XLR from the source directly to the sub? It means I would be using both XLR and RCA at the same time. As a general rule can I run like that? I don't see another way.
    Mike
     
  7. phurst

    phurst
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    Mike

    This does sound like it might be possible as long as you are prepared to run your main speakers 'full range' and not filter out the bass frequencies. As Nimby suggests it would probably be worth getting some dealer support on this one.

    The other option, again from Nimby's suggestion, would be to connect an active crossover but you'd then need to convert the XLR to RCA to input to the AV8.

    Phil
     

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