Sharing a sub with AVR and IA - HT Bypass

Discussion in 'Subwoofers' started by Rambles, May 2, 2018.

  1. Rambles

    Rambles
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    I am sure I am not the first person to come up with this, but I haven't seen it mentioned on the forums so thought I'd share my findings.

    Although I don't think I specifically need to use the sub for music, I thought it would be nice to have the option, and as my sub won't allow dual inputs simultaneously, and is on the other side of the room to the amps, so tricky to run more cables, I have come up with a workaround, that seems to work.

    The connection is to use the pre-outs from the integrated amp, back into an input on the AVR (eg cd input) and set that input to run in stereo mode only, with the sub in use, and set a crossover (I went for 60hz). I know that Marantz and Denon AVR's allow specific settings for 2 channel listening, not sure about other AVR's.

    Then, when listening to music with the integrated amp, if you turn on the AVR, select the cd input, and turn the volume up (for me -5 seemed to be about right) the subwoofer starts thumping away in time to the music :)

    I am actually using the sub out of my graphic equaliser to achieve the same thing, as I am already using the pre-outs of my IA into a power amp. But, the principle should be the same.

    @gibbsy @dollag @exponential - thought you might like the info.
     
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  2. dollag

    dollag
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    That's really interesting.

    Did you set crossover on the sub or the avr? I take it the avr?

    will defo give this a go for future ventures.
     
  3. Rambles

    Rambles
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    I didn't touch the sub, as I didn't want to mess up the AVR configuration.

    In my AVR, and should be the same for you, if you go to Speakers - Manual Setup - 2ch Playback, you can configure different settings for when listening in stereo. That is, add in the sub and set a different crossover to what you use for multi channel listening. I had a listen and thought that 60hz sounded best, as less 'double bass' with the main speakers than if using a higher crossover.
     
  4. gibbsy

    gibbsy
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    Interesting.
     
  5. dollag

    dollag
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    I thought as much, I done something similar back when i had my q500's as the lower frequencies needed some support.
     
  6. exponential

    exponential
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    That's a brilliant idea Rambles.

    When my Yamaha AS2100 comes on Saturday, i'll hook it up just so and see if I can replicate your plan.

    Saves me selling the SVS SB2000 for a sub with simultaneous high and low frequency inputs....:smashin:
     
  7. gibbsy

    gibbsy
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    I've been through my junk draw to try and find some old RCA interconnects, I knew I had a fairly long one, but no only short ones that I used with my old Technics. With my Rega being one side of my cabinet and the Denon on the other I need an RCA of 2m. My 300s, especially now with the addition of the Rega goes deep enough for my personal taste but I'm very interested in how the experiment turns out.

    PS. Why do we keep sooo much rubbish in a draw. I mean, who is going to use a scart cable in this day and age and a HDMI to DVI? On the bright side I did find an instruction manual for a Philips 26" CRT.:rolleyes:
     
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  8. Khazul

    Khazul
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    Interesting. Personally I would find that at a typical AVR cross over of 80Hz and with the signal delay through most AVRs that it would put the bass timing out just enough to start to mess up a groove.

    Also be REALLY careful not to select the input that is being fed from the amp's pre-out when the amp is in AV mode otherwise you could trigger a potentially damaging (to equipment and ears) feedback loop - so be really careful when switching back to AV mode on the amp.

    One advantage however is that you will not need to switch or mix inputs to sub - doing so without setting your fronts to large on the AVR tends to badly compromise the sub sound.
     
  9. exponential

    exponential
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    I've got a tesco bag full of AV leads... wouldn't mind, some of the cables cost me a fair few quid due to me succumbing to snake oil salesmen..:laugh::facepalm:
    Also, a half a manual for a Bush vcr/dvd combi in Japanese....:eek:
     
  10. Rambles

    Rambles
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    Yes, I was concerned about that, and I tried a different method first, which did sound ever so slightly wrong. That was to use the two digital outputs from my cd player, one to the AVR and one to the DAC. But, that didn't sound quite right, probably because the digital signal was going through two different DAC's. But using the current method, of going analogue into the AVR seems to be okay, and timing seems good. It is probably going to be very much individual set-up dependant though.

    Also, is this not the recommended way to bi-amp speakers, by using pre-outs to drive another external amp, similar principle maybe, so in theory the timing should be good?

    I don't know about that one. I know that there are tape loops and rec out and in which work on the principle of looping sound out and back in to the same amplifier. Apparently that's how they used to hook up graphic equalisers in the olde times. I can't test the theory as I use the integrated amp pre-outs to go into a power amp. I have a cd player and PC going into a DAC, then that goes into a graphic equaliser, and that then goes into the integrated amp. The equaliser has a sub out, so that is now in use to route the sub signal through the AVR and into the sub. It's got a bit complicated my system, I am not adding any more to it!

    Yes, exactly - the sub is just there and springs to life if the AVR is switched on, and to the correct input whilst music is playing via the integrated amp.

    I don't understand what that means, but I am interested.
     
  11. exponential

    exponential
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    Killer of dreams....:laugh::D:rotfl::rotfl:
     
  12. Khazul

    Khazul
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    That is different - a pure analog signal introduces no delays, so perfectly fine for bi-amping. As soon as you introduce DSP, then there is some delay and in the case of an AVR that can be quite considerable on top of the DSP processing in a sub as well. The VAR DSP will be one as you need the bass management active for what you propose - pure direct or equivalent will not do.


    (Re feedback)
    You may get saved a bit by the DSP delay through the AVR (unless of course you engage pure direct as well - in which case it will be instant full on howl and pray you get to the volume/mute in time), but even with the delay, the result may sound like a granular delay effect and may or may not not self damp depending on the AVR volume level and hence signal gain through the feedback loop.


    (Re small vs large setting for front)
    If you set to small, then the in AV mode sub ends up with a mix of 40Hz (or whatever you set the sub crossover to) sub signal and 80Hz (or whatever the AVR is set to) which may or may not sound a bit odd, but at least the front feed may be reduced by the subs over crossover so maybe not so bad. I didn't like it when I tried it. I'm sure some people might actually like the little low frequency bump you would get in AV mode - after all that is kind of what the music/switch does anyway.

    Maybe its just me - I'm less fussy about sub low frequency response extension (so long as below 30Hz), but timing and odd frequency behaviour really bugs me or at least just stops music from having the desired effect :)
     
  13. Rambles

    Rambles
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    Okay, I see what you're saying. It is a pure analogue signal, but the AVR will apply some DSP (digital signal processing) by applying Audyssey (I'd forgotten that would happen, which is actually a good thing, as my sub sounds better with Audyssey) and expanding the 2.0 input to a 2.1 output, and applying the selected crossover.

    It all sounded in time to me , when I tried it earlier, so I guess people's mileage may vary. Have you tried it in your set-up?
    A quick google search suggests that a feedback loop needs a microphone in the chain to pick up the output and feed it back in as an input, which isn't the case here.

    If the AVR and the integrated amp was switched on, and the integrated amp was switched to the HT bypass input, and the AVR was switched to the cd input mode (where the pre-outs of the integrated amp were connected) there would a loop but there would be no signal being input into the system at that point to create any feedback. You would either have to switch the integrated amp to the cd input to get the music input into the system. Or, you would need to switch the AVR to another input to get sound from the TV (for example) into the system. So, I don't think there is any risk. Is there?

    Oh, okay. I must admit i thought we all set our speakers to small in AV mode, with a crossover around 80hz (although I use 60hz for my front three) but I suppose everyone doesn't do that. With the Denon / Marantz AVR's though, you can configure bass management completely differently for 2 channel playback, than you do for AV playback. I don't know if Yamaha offer that? I actually have a Yamaha RXA810 in a separate room, but I never use it for music so cant't remember if it has that option.

    Yes, absolutely. As i said, I don't think I *need* the sub for music listening, as the R300's do go very low, but I am a bit of a fiddler, and just thought if there was a quick, cheap and easy way to add in the sub for music, seeing as it is just sitting there doing nothing, it might be nice to have that option. :)
     
  14. Rambles

    Rambles
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    Just found this advice from Denon on how to connect an EQ to the system. They advise taking the pre-outs of the AVR into the EQ then back out of the EQ and into a spare input on the AVR. So, I think it must be okay to create a loop in this way:

    Connecting an external EQ to the AVR
     

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