Surround subwoofers?

Discussion in 'Speakers & Subwoofers' started by Vaughan Odendaal, Aug 8, 2003.

  1. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    I'm wondering if there are any articles based on surround subwoofers.I'm mostly interested in understanding if subwoofers in the surround channels actually benefit or heightens the realism.Can you percieve low bass in the surround channels when a surround subwoofer is active?

    Regards
     
  2. Tom_Es

    Tom_Es Auditioning

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    I'm definitely not an expert on the subject, but as long as you get speakers that go down to about 80hz, without losing to much db, and let the sub handle sounds below that - it seems few people think that it is a problem having a single sub.
     
  3. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Perhaps someone has an answer?

    Regards
     
  4. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Hi Tom,

    Its just that all channels have a 20hz low frequency bandwidth, so that should mean that material should be in those channels, correct? But specifically, for those with surround subwoofers, are there any benefits? Can you percieve low bass waves in surround channel effects? Or more specifically, would I be able to percieve low bass pan over from the right surround channel to the left? Most importantly, is it possible to feel bass within those surround channels? Sorry for all the questions, but i'm intrigued.[​IMG]

    Regards
     
  5. Lew Crippen

    Lew Crippen Executive Producer

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    There are two concepts that are helpful to understand when considering the merits of a ‘surround subwoofer’: our ability to perceive directions for low frequencies and the nature of 5.1 encoding and reproduction.

    As a general statement our ability to perceive direction in sound is directly related to the frequency of the sound. We easily distinguish (in a relative sense) high frequency sounds and are mostly unable to locate the direction of low frequency sounds. It follows that the very low sounds typically reproduced by subwoofers are almost impossible to locate. This is why the placement of a subwoofer is not too important in terms of directionality (although there are some reasons dealing with accurate sound reproduction on why the physical location of the subwoofer is important). And why having more than one is not too important (with the exception of those who have large rooms and desire the extra volume that multiple subs can provide).

    Leading us to conclude that so long as we do not attempt to reproduce sounds with frequencies just a little too high, the number of subs and their location is not important. Put another way, this argues against any reason to have a sub associated with surround channels.


    There are only two types of use for subwoofers. One is to reproduce the Low Frequency Effects (LFE) channel of 5.1 sound (the LFE channel is the .1 portion of 5.1). LFE channel is typically used to reproduce explosions, crashes and other items of this nature. When you connect your sub to your receiver via the sub output and set the sub option to ‘yes’, this means that all of the LFE sound goes to the sub and none goes to any other speaker. And this is exactly how the audio guys doing the sound mixes intend you to hear their mix—they have nothing inherent in their design for physical location of LFE sound.

    This also argues against any reason to have a subwoofer for surround speakers.

    The other use of a sub is to reproduce the very lowest notes of the spectrum for some or all of the other five channels, bypassing the main and surround speakers altogether. This is what happens for the speakers that you set to ‘small’. The receivers crossover sends all sounds below a certain frequency (90hz for example) to the subwoofer, regardless of where the sound designers intended it to go. Here, the idea goes to the difficulty in our ability to determine the location of very low frequencies—since we can’t tell where these sounds are coming from anyway, it make sense to send them to the one place where they will be reproduced the best.

    Mostly there is not a lot of low frequency sonic information assigned to the surround channels, but you can get it in those speakers by setting them to ‘large’. Although most surround speakers are not great at reproducing very low sounds—mine drop off at about 60hz and I have by sub crossed over at 90hz in any case.

    This too, argues against a sub for surround speakers.

    How then, you may ask, do I hear the direction of the depth charges in my favorite submarine movie? The answer lies in the portions of the depth charge explosions (there are a lot of reasons for this including harmonics, but I’ve written too much already) that are above 150hz or so (more or less where we begin to be able to tell the direction of sound). This part of the sound goes to one of the other five speakers so we can tell the sound location.
     
  6. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Lew,

    Thanks for the good points[​IMG] Are there any websites or articles that you know of, that goes into more detail? I know that there are some members on this forum that have multiple subwoofers for different channels, and i'm just curious to know if there really is material within those channels that make it all worthwhile.Eg. Tanks moving from behind you, and cannon blasts in your right surround channels.I guess that not many own surround subwoofers.

    Regards
     
  7. Armand G

    Armand G Stunt Coordinator

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    Hi Vincent,

    I own one for the surround channels. It has improved my system quite a bit. My rears extend to below 20 Hz now. Actually there is a lot of movie material with < 25hz bass in the surround channels. Especially SW Episode 1. I have connected my Rel Strata III with the High level input (Neutrik speakon)directly from my loudspeaker terminals of my amp. I have a Rel Storm on the .1 Channel.
     
  8. MingL

    MingL Stunt Coordinator

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    Might want to consider sonic cancellation issues too if the 2 subs are placed in different places of the room. More harm might be done than good when freq response becomes uneven.
     
  9. DonnyD

    DonnyD Screenwriter

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    I kinda went through this same thing when I began to collect HT stuff several years ago and tried out all sorts of configs including using surround subs.

    I acquired 2 sets each of the JBL Sat 2 and Sat 1 surround series. One was small satelites and 2 small subs. The other was 2 larger sats with one larger sub. We messed around with this stuff until my GF must have thought we were crazy. I must add that this was before I ever heard of SVS!

    My main sub was one of the older JBL 12s and we placed the larger Sat subs at the ends of the couch. It did make quite a difference to the movie experience and added to the fullness in the low end. No I don't have a bunch of numbers or data to share but several of us experienced this and all agreed that it did make a considerable difference. And this was back when we were just hooking it up and turning it on. No calibration disc or anything else.

    As my collections grew more intense, of course I went with SVS for my main sub and changed out everything else. Those old JBL Sat subs weren't the cats meow but they did add something. My brothers small HT setup still utilizes them as mains tied to each of his front speakers with surprising results. My son still has the smaller sat subs tied to his rear surround and while they don't do much at all, it is a small difference although barely noticeable.

    I always liked the larger of the JBL Sats and they are still being used in my big system as front effects. We moved a couple of years ago and my config of furniture didn't allow me to ustilize any rear surround subs but with a SVS and butt shakers in the couch too and as loud as we like our movies, they might not make any difference anymore. BUT, dadgum it, this thread reminds me of the fun we had messing with all this and had me in my HT room looking for options again.

    Once again, no data or anything.... just what several of us thought about things. I have certainly moved through several variations of equipment since then and I end up setting up a lot of my friends HT systems.

    So I say, try it and you just may like it. It is fun and if you look around you'll find some subs on the cheap to play around with. To me, it was a worth while exercise if it only fed my need to learn from the seat of my pants back when there wasn't a lot of info floating around. As a matter of fact, it was before I discovered Home theater forum and just as Dolby Digital receivers were released. I muct add that I am still having just a much fun so beware, this stuff is very additive hence, my sig......
     
  10. Andrew Pezzo

    Andrew Pezzo Second Unit

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    You will find that more movies today have a lot more bass info in the surround/rear channels than in the past. I have been thinking about adding a sub to my rear channels as my front 3 main speakers all have built-in subs and I dont have a seperate sub. I know that if the speakers are set to large that the .1 will also go to that channel but I feel that I am missing some bass from the surrounds even though I have not compared with and without a sub connected directly to them.

    I did watch one movie with a pair of Def Tech BP2006TL's for surrounds and I was suprised at the amount of bass in the surround channels. Mostly because of that I really want to add a sub to my surrounds. Once I can find a decent inexpensive sub on ebay I will try it out.
     
  11. DavidES

    DavidES Stunt Coordinator

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    Mr. Price, Here is an excellent white paper along the lines you are asking about.
     

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