Subwoofer connection (line level vs speaker wire)

Discussion in 'Speakers & Subwoofers' started by PaulDA, Feb 24, 2004.

  1. PaulDA

    PaulDA Cinematographer

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    If I set my receiver to no sub, and wire my front mains to my sub, then sub back to speaker terminals in receiver, will LFE go to sub (assuming proper crossover setting) or to both sub and mains? My receiver has a two channel bypass that I'd like to use but it won't digitize low frequencies and reroute them to the sub like some other receivers and pre/pros (at least I don't think it will, I'm still waiting to receive it). I'd prefer not to have to constantly change the type of connection I have to my sub when switching from music to movies.

    Thanks.
     
  2. ScottCHI

    ScottCHI Screenwriter

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    the LFE signal in a speaker-level set-up like that will be "shared" (along with any signal re-reouted from the center and/or surrounds) by both the mains and the sub. how much is "shared" with the mains will depend upon whether the sub's speaker-level outputs are unfiltered or crossed-over (most subs utilize a crossover for the speaker-level output) and at what frequency the crossover is set (could be fixed or variable on your particular sub). to me, there's nothing "wrong" with some of the LFE signal "bleeding" into the mains, with that setup, however an HT purist might consider it undesirable. it actually can provide a nice top-end to your LFE signal, add some presence, and aid in blending.
     
  3. PaulDA

    PaulDA Cinematographer

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    Thanks, Scott.

    A follow-up. What kind of Frequency response rating should I be looking at in order to make this kind of setup workable? Floorstanders? Bookshelves?
     
  4. ScottCHI

    ScottCHI Screenwriter

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    well, i guess that would depend upon whether the sub's crossover to the speaker-level outputs is variable or not. if not, it's probably fixed at 80z, like most. so, in that case, any speaker capable of reproducing sound accurately down to 80Hz (lil lower, really) or so should work fine. unless the sub's speaker-level output's crossover (high-pass filter) is adjustable, then steer away from main speakers that are too small. otherwise, just about anything, bookshelf or floorstanding, that would work nicely with a "traditionally" wired set-up should work fine.

    just to let you know, you can also wire the mains directly to the same front R&L speaker outs that you plan to wire the sub to if you'd like to get full-range audio from them. but based upon your initial question, it sounds like this is NOT what you're seeking. of course, with that set-up, the mains would attempt to play ALL of the LFE signal (that they could), along with the sub.

    what receiver do you have, btw? are you certain that the speaker-level set-up is what you need? most current receivers will re-route the bass to the sub for you during standard 2-channel audio playback.
     
  5. PaulDA

    PaulDA Cinematographer

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    I have an Arcam AVR200 and it doesn't seem to have that ability. It's on order, so I'll have it in few days. The literature and dealer suggest that in audio bypass mode, the sub is ignored in 2 channel (not in 5.1 analogue, however).
     
  6. Michael__M

    Michael__M Stunt Coordinator

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    Which receiver are you referring to?
     
  7. ScottCHI

    ScottCHI Screenwriter

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    taken directly from the AVR200 product manual:

    so, it appears that your receiver IS capable of rerouting the low end to the sub during stereo music playback

    manual is available here, btw:
    arcam.co.uk/downloads/AVR200.pdf
    sorry, i'm unable to post links here until i have more posts, so put the prerequisite http//.....yadda in front of that link

    [​IMG]
     
  8. PaulDA

    PaulDA Cinematographer

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    Thanks for the info. Really looking forward to playing with my new toy.
     
  9. ScottCHI

    ScottCHI Screenwriter

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    hehe. that "playing" will quickly turn into endless, obsessive, compulsive twiddling

    [​IMG]
     
  10. PaulDA

    PaulDA Cinematographer

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    I know, I'm already doing it and I don't even have the toy yet.
     
  11. Edward J M

    Edward J M Cinematographer

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    The Arcam manual is unclear as to what the actual xo will be when the speakers are set to small. It implies the xo will be 100 Hz, but it is not specifically listed in the specs section.

    It also does not list the the slopes of the high and low pass filters, nor does it fully explain what the Stereo Subwoofer setting actually accomplishes.

    Regardless, I would shy away from a speaker level connection for myriad reasons. I would set all the speakers to small and the subwoofer to yes. I suspect doing so will give you a 100 Hz xo with a 12 dB/octave high pass on the surrounds, and a 24 dB/octave low pass on the sub.

    When you connect to the subwoofer, make sure you use an unfiltered input at the sub. If your sub does not have an unfiltered input, it may have a filter enable/disable switch. In this case the switch should be set to disable. If the sub has neither an unfiltered input, nor a filter disable switch, then set the sub's low pass filter to its highest setting to prevent cascading the Arcam's and the subwoofer's low pass filters.

    The Stereo Sub feature will give you one of two things:

    1) It will retain the bass management circuit used for DD/DTS and give you a 100 Hz xo with 12/24 high/low slopes - i.e., a true 2.1 arrangement. This is the preferred scenario obviously.

    2) It will send a full range signal to the mains, and it will also send a filtered signal to the sub, low passed at 100 Hz with a 24 dB/octave slope. This scenario is less preferred, since the mains are not true full range and you will be hearing your bass twice, to the extent the mains can also play it.

    When you get the Arcam and hook it up, it will be easy to tell which of the two above scenarios is true by setting the Stereo Sub feature to On and then manually powering off the sub and listening to just the L/R mains. If they are truly being high passed at 100 Hz, you won't hear much bass from them at all, and the cone excursion will be minimal. If they are being sent a full range signal, you will hear more bass and the cone excursion will be obvious on bass passages.

    Let's be eternal optimists and bet on #1. [​IMG]

    Ed
     
  12. ScottCHI

    ScottCHI Screenwriter

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    many people will prefer the latter scenario in their receiver's direct or pure direct modes, particularly if it means maintaining an all-analog signal and bypassing bm circuitry
     
  13. Edward J M

    Edward J M Cinematographer

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    Yes, my AVR-3803 will retain an all analog full range signal path to the mains in Direct or Pure Direct IF the subwoofer is set to off. Enable the subwoofer, and it still retains the full range signal to the mains, AND sends the sub a low passed signal, in my case filtered at 80 Hz. This results in an exaggerated bass response below 80 Hz, as the mains and the sub are both playing the same bass signals and the mains are capable to around 40 Hz in my system.

    I consider the inherent capabilities of the subwoofer vs. the mains to be far more important than maintaining a completely analog signal path (the benefits of which may or may not be audible), so I retain a 2.1 digital BM scheme for 2 channel music.

    I can electronically lower the xo down to 40 Hz with the AVR3803 if I want to, so I don't subscribe to that particular school of thought that a speaker level connection to the sub is preferable for 2 channel.

    A speaker level connection wastes amplifier power, almost always has a fixed 1st order high pass (usually at 100 Hz), and the variable low pass xo is typically only 2nd order. Thanks, but no thanks - I'll stick with digital BM for 2 channel any day.
     
  14. ScottCHI

    ScottCHI Screenwriter

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    how do you ensure this on the denon, btw? set the speakers as SMALL and/or don't use the direct and pure direct modes? i just got a 3803 and i've been wondering about this, myself. as you know, the manual is a bit inadequate in it's bm explanation.
     
  15. Keith Hyde

    Keith Hyde Stunt Coordinator

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    I contemplatd the same since I lean towards music over HT, but I opted to stick with the dedicated sub out (no speaker wire) so my HT would have a dedicated channel all to itself. I tend to like it just fine this way.

    And just because you may have a dedicated sub cable instead of speaker wire doesn't mean you lose the ability to mess with crossovers, either. My Denon AVR can send bass signal to the Sub only, or to the Sub and Mains together. I've selected the Sub and Main option, and tweeked the SVS's crossover whenever I felt a need to have a little "more" or "less" bass (but I don't have good bass Mains either). Generally it sounds fine with the SVS crossover disabled - the bass coming across both mains and sub on music playback, leaving all the bass crossover up to the Denon's built-in setting.

    When the Denon AVR does the Dolby decoding, you get your stand alone LFE channel back. So you save speaker cable and plugs, and get the better of both music and HT worlds. It's just easier for me that way but to each their own, you know.
     
  16. ScottCHI

    ScottCHI Screenwriter

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    in a speaker-level set-up, if you use the sub's crossover, most of the LFE channel will come out of the sub only

    you mean LFE signal, don't you?
     
  17. Edward J M

    Edward J M Cinematographer

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    Yes, if you will be using the Denon to decode 2 channel material via the digital coax input and you want to retain digital BM (2.1), you must use the "Stereo" mode, and not the Direct or Pure Direct mode.

    Another option is to use a player with onboard BM and send the Denon an analog signal via the External Inputs - this is how I listen to all my music - 2 channel, DVD-A, SACD, and DTS-A. I only use the 3803 to decode DVD movies via the digital coax.

    Ed
     
  18. ScottCHI

    ScottCHI Screenwriter

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    ok, thanks edward, this has been a helpful discussion. i posted these exact sorts of questions HERE very recently. hope i don't seem too argumentative; i'm just both very curious and puzzled about this whole denon bm thing, and want to get to the bottom of it (no pun intended!)

    flaw? maybe.

    but, isn't someone who sets their front speakers up as LARGE, always listening to 2-channel music with that same redundancy, that you shun, in the low end frequencies?

    and 25 years ago almost every sub set-up i ever saw did have that redundancy. speakers were connected to an amp or channels of an amp, and run full-range. the sub was connected to another amp or channels and a low-pass filter/crossover was utilized at some point in the connection, initially NOT being built into the subs themselves. they were called SUB woofers for a reason and were supposed to augment the bass output of your full-range speakers. high-pass filter/crossover utilization for the speakers did of course enter the scene, eventually being incorporated into the subs themselves, offering speaker-level connections, but even as little as 10 years ago, the dogma among music audiophiles and purists was to NOT use the speaker level connection and the sub's crossover, but to run the speakers full-range. i think that's still true, today. most really high-end systems built and used for 2 channel music reproduction today, do it this way as well. they may have a powered sub on a pre-amp level output, but the main speakers are usually run full-range. what you're describing above as a "traditional" set-up is really a present-day speaker-level set-up, utilizing a sub's built-in cross-over.

    btw, do you know exactly what comes out of the sub output during 2 channel music playback when the fronts are set to LARGE? it doesn't sound unfiltered to me, but seems to utilize the same crossover that'd be used for any speakers set to SMALL, which makes me wonder what would come out of there during 2 channel music playback if none of the speakers were set to SMALL, thereby not having a crossover setting at all on the receiver.
     
  19. Edward J M

    Edward J M Cinematographer

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    Yeah, I see what you are saying about the "sub" woofer - years ago they were really only used to augment below the natural roll-off of the "woofer" in a speaker.

    But in that application, there was not much overlap/duplication of frequencies, which is what happens with the Denon Direct and Pure Direct modes if you enable the subwoofer and leave the xo set to say 80 Hz.

    As an aside, it is easy to shut off the sub in Direct and Pure Direct with the remote - just use the large center button and scroll through the channel levels on the AVR display until you get to the sub and then reduce it to below -12 and it will say "OFF" on the AVR display.



    Again, if you set the mains to Large and the sub to Off, the mains will get a full range signal and the sub will be silent.

    If you set the mains to Small and the sub to On and select an xo frequency, in Stereo mode you will get a true 2.1 digital BM circuit with a 12 dB/octave high pass and a 24 dB/octave low pass at the selected xo frequency.

    Ed
     
  20. ScottCHI

    ScottCHI Screenwriter

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    oh, trust me, i have been toggling between the modes! and yeah. i guess it is a flaw, or aberration. i thought that's what was going on in direct mode. but many people obviously do have mains that are quite capable of full range sound reproduction and do run them as large, along with a subwoofer, albeit perhaps with a lower crossover setting than 80Hz. most HT receivers' default, out-of-the-box setting is a LARGE front speaker with the sub ON. personally, i like the fact that my speakers, even though set to SMALL, are running full-range when i'm playing music in the direct modes. that's the way most music was meant to be played; on full-range speakers. i don't really want to run it as 2.1. it wasn't recorded with an LFE channel. if only i could set a lower crossover on the 3803 for 2 channel playback that would be "remembered", thereby reducing that low-end redundancy when i listened to music in direct modes, and still run the speakers as SMALL with the 80Hz crossover, in my 5.1 mode.

    but i think what we see here in this discussion is support for or at least a basis for why some people advocate speaker-level hook-up of the sub and the bypassing of the receiver's bass management altogether; bass management is still not perfected and has these "flaws". i'm not advocating speaker-level connection, necessarily, although i have been seriously considering it, as i've been struggling with fully understanding and managing this whole bass management thing for a few weeks, now. i learn something new every day, and i've learned some more from this discussion (no, it's not an argument!) with you today. thanks.

    btw. do you have any idea whether the LFE signal, when you tell the receiver that you are running NO subwoofer, might, by chance, end up rerouted to the front pre-outs similarly to the way it's rerouted to the front speaker-level outputs?

    and i still want to know what's coming out of that sub output during 2 channel direct playback when all the speakers are set to LARGE.
     

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