Surround subs? Who uses them?

Discussion in 'Archived Threads 2001-2004' started by Craig Ball, Feb 24, 2002.

  1. Craig Ball

    Craig Ball Second Unit

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    I jsut sold my 20-39CS And Samson S700 amp, And i'm currently waiting for my 20-39CS+ and Samsom S1000 to arrive[​IMG] I was wondering about adding one or two more subs to my surrounds as i've read several articles of how surround channels go down below 50hz, I know my surrounds won't go that low. Do you think adding a sub or two to the surrounds and setting them to large would help?
    Craig
     
  2. Alex_Hutton

    Alex_Hutton Extra

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    each of my surrounds has a 6.5" sub and i like it.

    Dunno though, probably isn't that important
     
  3. Craig Ball

    Craig Ball Second Unit

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    Thanks Alex, but what I mean is a true subwoofer to the surrounds. Each of my surrounds have two 6.5 inch woofs built in to them, but these aren't subs.

    Craig
     
  4. Mike Ilano

    Mike Ilano Extra

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    Craig
    I have my rears (B&W cdm1se) passing thru an old Klipsch powered sub and it seems to do the trick.There is quite a lot of movies with bass content for the rears,specially "Saving Private Ryan" [​IMG]
    MIKE
    Our HT!
     
  5. MikeKaz

    MikeKaz Stunt Coordinator

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    I know of a high end installer who did installations with subs in the surround locations. He ran the surround speaker wire to the subs, and used the sub's crossover to output to the surrounds. He said this worked great and that customers were really happy with it. There are a couple of other things to look at too though. First, professionals don't mix tracks with individual subs at each surround. None of the mixing studios that I know of and no movie theaters have that setup, instead using the smaller surrounds with subs placed elsewhere. But there is another issue of multiple subwoofer placements in a system. If you have several (3 or more) you can place them so there will be no cancellation of bass in any areas of the room and have a very even response throughout. You have to place them pretty specifically however, and this is assuming you're using them in their normal role as subs with each one getting the full low freq signal and your other speakers in low bass roles. In a lot of rooms this optimal placement is like one sub near the middle of the front wall, one halfway up the left wall, and then one 1/4 the way from the right on the back wall. This will give outstanding response throughout the room with basically no dips in response at all. Also, having a lot of subs running the same signal and turning down the volume on each means each one only has to put out a fraction of its total output, and people who have done that have said you can get unbelievable realism with ridiculously low distortion running like that.

    A big reason that you WOULD want to have a sub on each surround (or each speaker depending on how you set it up) is for Multichannel, hi-quality music like SACD and DVD-Audio. Most players on the market now don't have bass management and just send the full range output to each speaker irregardless of where it is. You can get amazing sound if you get a SACD player and are able to hear the full bandwidth of each of the channels.

    In the real world, movie soundtracks are meant to be played with subs taking care of the low bass for all the channels. They are mixed with low bass in the surrounds because that’s how that channel would actually sound in real life. There would be low rumbling from that explosion behind you, and it goes into the surround channel. They don’t want to make any decisions for the user as to what the best speaker/frequency range setup is, that would be very Dolby pro-logic like. They know your digital processor will take care of it.

    So basically, if you had a sub on your surround for an action movie, it might help add presence and would sound good. But, having the speakers run as small with a sub doing the bass wouldn’t be inferior to that method either. Having subs take tare of all of the channels is just how it’s done. The most just ridiculously big movie theater speaker ever made, the JBL 5674 with four 15” woofers, and a mid and high frequency section, 400lbs, 5300watts, is set up with a regular bass crossover frequency and its bass supplied by separate subs located elsewhere in the theater. And the best mixing studios in the world have small surrounds with a bunch of subs pumping out the same signal.

    However, if you think you would be seriously interested in creating a system for SACD, then subs for each channel would be a good thing. But more SACD players are coming out with bass management now, so this might not be an issue soon.

    So- subs for each surround, might be pretty cool but would not necessarily be better than splitting the common bass signal into several subs, depending on their placement. Also, good for multichannel audio without bass management.

    Multiple subs in locations chosen by the layout of the room would give great response throughout, get rid of bass nodes and dips etc, would give very low distortion. Even if you think there's no distortion now, if you ran your system like this it would sound even more effortless and just "real". It would also be good for mulitchannel music if you have a player with bass management.

    So for most practical applications I would say definitely get the extra one or two subs, and id recommend doing the staggered kind of layout mentioned so you have awesome, even response throughout the room. And you can also certainly go ahead and hook them up to each surround individually and see which way you like. Whatever works best for you.
     
  6. Craig Ball

    Craig Ball Second Unit

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    Thanks, MikeKaz Great reply.

    Craig
     
  7. BruceD

    BruceD Screenwriter

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    I seriously doubt most users have the sophisticated acoustic measurement software necessary to tune multiple subs correctly in most rooms.

    The method descibed below may work in a room with ideal dimensions, but sadly that's not what many of us have.

     
  8. Richard Greene

    Richard Greene Stunt Coordinator

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    This statement is not correct:

    "If you have several (3 or more) you can place them so there will be no cancellation of bass in any areas of the room and have a very even response throughout."

    RG replies:

    Standing waves are a function of room dimensions.

    They are caused by surface-to-surface reflections.

    Standing waves can ONLY be eliminated by eliminating the room reflections that cause them.

    Standing waves can not be cancelled by some magical placement of three or more subwoofers.

    It is possible to place two subwoofers on opposite walls to avoid exciting a specific standing wave (there are many other standing waves in a room) but the resulting frequency response deviations in a rectangular room, when measured at the listening position, are almost always worse than using one subwoofer located in a room corner.

    For further reading:

    Audio Engineering Society reprint #4558 titled:

    "Multiple Subwoofers for Home Theater" by Tom Nousaine

    or "Subwoofer Secrets" in the January 1995 Stereo Review

    magazine
     
  9. Andy Anderson

    Andy Anderson Second Unit

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    Craig-
    There's a member here who's username is Legairre, he uses subs on each of his surrounds--and he loves it. I emailed back and forth with him a while ago when I was considering a similar setup. His HT page is here:
    Radden Home Theater
    You might want to email him directly if you have questions, unless he finds this thread on his own. He's a nice guy--very helpful. (I seem to remember making a similar recommendation sometime ago. Yup--here it is:
    Surround sub
    [​IMG]
    Andy
     
  10. MikeKaz

    MikeKaz Stunt Coordinator

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    random quotes-

    "Furthermore, multiple subwoofers, properly placed, can work wonders in reducing nulls that would otherwise occur in the listening room." - audiorevolution.com

    Kim Wilson- some audio reviewer

    "Multiple subs greatly reduce the propagation of standing waves."

    Use Two Subwoofers-

    "Using two asymmetrically placed subs will minimize the effects of standing waves in your room, yielding smoother bass response (as well as better dynamic range)." Paul DiComo, Richard Hardesty and Robert Harley, for a Polk newsletter.

    Dips in bass response can definately be reduced by proper, asymmetrical placement of subs, which is very dependant on the shape of the room. Im not talking absolutely level frequency response with perfect elimination of standing waves, but a big reduction in the amount and severity of null zones as you move throughout the room.

    BruceD-

    who says he's looking for "correct" tuning. that involves 92 band digital EQ's and computers controllers etc like you hinted at. I beleive this setup would be for increased bass response overall and in the rear of the room, not for reference flat response curve for a $300,000 system. In that case, if im not missing something here, wouldn't a single spl meter reading with all of the subs running at the same time at their lower levels be sufficient to set the bass level.

    as for "If all the subs are running the same signal, as was stated, then it seems you may not be getting any surround only bass." - if youre talking about say, a digital receiver where all the speakers are set to small, and then all of the bass is sent to one output and then that output is split and sent to the subs, then yes, that's what im talking about.

    plus there's a multitude of people out there who are against corner sub placement, and since output level isnt an issue since there are several subs running the bass signal, placement for maximum output shouldnt be a priority. you will have less of those obnoxious peaks the farther away from a corner and wall you are. corner placement is probably the best for single sub setups (mines in the corner) but the reasons to put subs in the corner are fewer when you have multiple subs that can manage to output a sufficient level without help from the room.
     
  11. BruceD

    BruceD Screenwriter

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    MikeKaz,

    Why don't we talk about the real world, OK?

     
  12. Wayne A. Pflughaupt

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  13. MikeKaz

    MikeKaz Stunt Coordinator

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    Bruce- I frankly dont care about the whatever thing octave charts etc.

    and wayne- thinking symmetrical placement for regular speakers is directly relatable to subwoofers is just incorrect. the propogation and interaction of long wavelength bass output from subs in a room follow very different rules than whats coming out of speakers pointed at your head. 1 sub corner placement is asymmetrical by the way.

    This high end professional custom audio installer was the one who intitially told me about the specific placement i mentioned. There's a bunch of people out there who beleive in and use this type of setup. You apparently hate it. Oh well. We don't all have backissues of Audio Engineering Society to reference. Im done on this thread.
     
  14. BruceD

    BruceD Screenwriter

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    Mike,

     
  15. BruceD

    BruceD Screenwriter

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    Craig,

    What is the crossover set at in your processor? What are the -3dB low frequency specs for your speakers; mains, center, surrounds? What are the length, height, and width of your HT room? Any large openings in this room?

    This will provide a clearer picture of what benefits you will get with additional subs.

    I believe you will get plenty of bass effect from your surrounds with just the re-directed bass to the sub-out of your processor. It is well known that frequencies
     
  16. Craig Ball

    Craig Ball Second Unit

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    Bruce.

     
  17. BruceD

    BruceD Screenwriter

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    Craig,

    Here's my read on your setup:

    Your total room volume is approx 3120+ cuft (not counting hall and staircase) which is not large. The 2 CS+ should provide more than enough capacity.

    Since your mains go to 36Hz and one octave above that is 72Hz (one octave typically allows for the smoothest xover transition), one option is to set all speakers to small with an @80Hz xover to multiple subs in a corner.

    Setting main speakers to Large, the rest to small and using the 60Hz xover means the surrounds are missing full output in the 60Hz-75Hz range (not good).

    Improving your sub(s) overall bass output in your room may require the use of a parametric EQ on the sub-out channel to reduce specific room peaks and allow you to properly calibrate the SPL levels of the entire 2 lower bass octaves (20Hz-80Hz). I think this is a superior choice to subs in multiple locations.
     
  18. Steve Morgan

    Steve Morgan Second Unit

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    I have to agree with Wayne and Brucek on this one.After spending the last 3 months or so trying to get the best response and greatest output in a 4800cubic ft room, the best soulution was to corner load the subs for the best response and output.I initially had 1 sub(Servo 15a) about 1/4 along the back wall and the other sub(Von Schweikert S/3)in the front corner, after moving them to different locations the readings with an SPL meter and Test tone generator proved the corner to be the best location.This is still a work in progress but could not be accomplished with out Test tones,SPL meter,and Parametric equalizer.[​IMG]
    Steve M.
     

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