Multiple subwoofers? How to and is it worth it?

Discussion in 'Archived Threads 2001-2004' started by StevenB, Mar 30, 2002.

  1. StevenB

    StevenB Agent

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    Hello,

    I have a Pioneer VSX-810S receiver. The sub I am currently using is a Boston Acoustics PV-600. I am considering something from the SVS series. If I decide to go that route, is it worth having 2 subs going? If so, can anyone tell me how I would connect 2 subs to this receiver? Would I be better off just auctioning off the BA sub and go with one SVS? Any useful advice would be appreciated. Thanks.

    Steve
     
  2. Elbert Lee

    Elbert Lee Supporting Actor

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    Steve - I'm running 2 subs and have asked a few questions myself. Cancellation is a huge problem and the best way to avoid it is to STACK the SUBS (one on top of the other). Theoretically, there is only ONE optimal place in a room to place a sub, so if you do have 2, you should probably stack them.

    However, if stacking is not an option (as it seems with SVS), I was told that placing them as far apart as possible is the next best thing. The only way to make sure is to get a spectrum analyzer and measure yourself.

    I don't know if changing the phase on one of the subs will be of any use as it might defeat the phase switch if it was originally designed to work so that the sub will not cancel out bass from your mains.

    I would definitely like to hear some other opinions on this subject again since I have 2 subs (M&K MX200 and NHT SUB 2) on the far right and far left front of my ht setup and I haven't had a chance to test it yet.

    Elbert
     
  3. brucek

    brucek Second Unit

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    Steve,
    Connecting a second sub is as simple as splitting the "sub out" signal of your receiver with "Y' cable that you can purchase at any Radio Shack. Then run an audio cable to each sub.
    There are a few problems associated with using two subs.
    As Elbert has indicated there is a possibility of cancellation because of phasing, but this can usually be overcome by co-locating the subs so they effective act as one. Corner positioning is considered the best location for a sub. Some people get away with separating two subs, but most don't (or don't realize the problem). [​IMG]
    Your big problem will come from mixing two very different types of subs. I'm afraid to say, your PV-600 might be considered challenged if used with most SVS models. Two subs doesn't make your subs any louder, it simply gives you headroom when you need it.
    Consider a sub that has a response from 20Hz - 100Hz and it produces a certain SPL in my room. If I add a second similar sub with the same response and have the level controls set the same, the two will reinforce each other and be "louder". To compensate for this, I will be able to turn both subs down to reach the same level I had with one. But now I have increased my headroom for the same SPL output. I can handle bigger explosions etc without compression of the signal because my sub isn't overloading and can handle the transient.
    So two subs are a good thing - but here's the rub.
    Take the same scenario and use a second sub such as the PV-600 that has a response that is already down 3db at 29Hz. The common areas where the response of the lesser and greater sub overlap will re-inforce and you will be required to turn both down to a calibrated listening level. This unfortunately will also lower the un-common areas of the great sub, and this will be the all important under 30Hz area. You will be holding the great sub back by mixing it with a lesser sub.
    This is a common mistake when someone has a sub and wants to add a second. They step up several notches in the food chain and don't want to get rid of the first sub, thinking it will add to the mix. In your case, my advice would be to not use the PV-600 with an SVS, use a single SVS or get two SVS's if you're feeling rich. There are also lots of other good subs such as the HGS or Servo-15 models etc...
    brucek
     
  4. Marvin E

    Marvin E Stunt Coordinator

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  5. brucek

    brucek Second Unit

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    Weird article, Marvin. I don't think the author has heard of bass management yet. He seems to only know about LFE.
    He also has no doesn't seem to have a grasp on phasing or localization. Interesting stuff......... [​IMG]
    brucek
     
  6. Wayne A. Pflughaupt

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    This statement from the article is patently false:
     
  7. Chris PC

    Chris PC Producer

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    Yeah, sounds like good advice. Use one subwoofer and determine the best location. If you want to use two subs, use two identical subwoofers and place them as close together as possible. Don't use two different subs together, because whichever subwoofer has the lower bass extention, you will not be able to benefit unless you EQ'd your subs separately for flat room response.

    I'm really playiung with bass response so I have to comment, aren't two tower speakers with low extention similar to two subwoofers? What does that mean in terms of placement? Even when you take into consideration the crossover between towers as SMALL and a subwoofer, wouldn't it be wisest to place any subwoofer as close to the two towers for optimum blending and minimized cancelations and standing waves?
     
  8. Wayne A. Pflughaupt

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  9. Marvin E

    Marvin E Stunt Coordinator

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    The following are excerpts from a Wide Screen Review Article:
    http://www.robertmargouleff.com/publ...creen_1299.htm "The following conversation took place at Mi Casa, the post production mastering studio owned by producer/engineer Robert Margouleff and co-proprietor engineer Brant Biles. The Mi Casa team was joined by Jesse Torres, New Line Cinema Post Production DVD Technical Operations Manager. Together, these gentlemen are responsible for pioneering the work of mastering motion picture soundtracks for optimum playback on home theatre systems. Widescreen Review Editor and Publisher Gary Reber asked the questions during a recent visit to Mi Casa.
    WSR Reber: I have seven subwoofers in one of my primary reference systems, the Mirage M1si system. I have a subwoofer capable of below 25Hz bass at full scale SPL electronically mated to each full range speaker, that on their own, are capable of bass down to 25Hz.
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    Margouleff: I like the guys that face the subwoofers to the wall. That's another one of my pet peeves
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    Biles: And also there's the issue of low frequency localization, which people say you just don't localize low frequencies.
    WSR Reber: That's not true.
    Biles: That's very untrue.
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    Biles: And if you have an event that occurs in the rear channels that is low-end oriented and you chop it and throw it to your subwoofer, which is more times than not going to be in the front of your room, you're going to get this frequency pulling effect, where you'll hear the top-end of whatever the event is occurring behind you and, in a strange way, hear the low frequencies sucking down to the subwoofer in front of you. To me that is most annoying. It makes my hairs on my arms stand on end.
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    WSR Reber: I don't use any bass management, but I'm just saying that I really know when things are deeply moving. I recently reviewed the Dolby Digital Saving Private Ryan LaserDisc. There is an absolutely perfect demonstration of why you need total full range loudspeaker capability in the surround channels. We're talking about deep bass that is at pounding full scale SPL, with such low level frequency intensity and directionality that you can never optimally reproduce that soundfield without full range deep bass capability to below 25Hz in each vector including the two, or three, if you're using a center back surround channel, surrounds."
     
  10. brucek

    brucek Second Unit

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    Marvin,

    Very interesting stuff. I'm sure that in their properly designed studio these guys have been successful in eliminating bass management and use a subwoofer per 5.1 speaker. Seven subs is a lot.

    No doubt through an abundant knowledge of acoustical principles and bottomless pockets they've somehow solved the subwoofer EQ problem. Good for them.

    The problem we mortals have is that we have a finite budget and in my case a limited knowledge of sound interaction in a room. To eliminate cancellation problems "most" people have found that using processor level bass management on all speakers and a single or co-located sub generally works well. This allows then for parametric EQ to be used on the subs to alleviate problems created by our crappy rooms at low frequencies.

    To use a sub with every speaker usually requires the use of speaker level connections which eliminates the possibility of line level sub EQ. So not only would it difficult to smooth a single non-EQ'd sub, you would have to deal with the interaction of five plus LFE subs. The only ammo in your arsenal for this task would be room placement or the room itself. I know I wouldn't have the patience for such a task. Sure anyone at home can hook up 7 subs and say they like the sound, but have they heard what a single, capable, properly placed EQ'd sub sounds like in comparison at a fraction of the cost..... The other option would be a wholesale split of all line outputs from the preamp and individually EQ each channel before it went to the seven subs. That's a lot of EQ amps and a lot of cabling. Not everyone's cup of tea. Then you would have to match each full range speaker and its natural roll off with the low pass of each sub. Not an easy task.

    I'm not sure how these articles relate to Steves question though...

    brucek
     
  11. Ken Stokes

    Ken Stokes Agent

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    Just to give another perapective, I am running two Aerial SW12s and love them. There were some placement issues but they were resolved without a great deal of effort.

    There are those that encourage multiple subs that at the very least deserve respect for their opinions. Richard Hardesty, former editor of widescreen review and industry expert, offers that any system with less than two subs operating in stereo mode is not complete.

    Mike Kelly, owner of Aerial Acoustics, recommends at the minimum one sub each for the front R&L. You could say that his motivation is business but if you have ever talked to the man you know that is not the case. He lives for perfection in sound reproduction and is more ethical than anyone I have met.

    With my two subs operating apart from each other and matched with the R&L speakers I get a much fuller sound production than with one. Notice I didn't say louder, that was not an issue, but fuller. There is some bass that is directional and adds greatly to the track.

    If I had unlimited resources I would run five subs. One in both the front and rear R&L positions and one just for the LFE track, but that is for another day.

    I suppose all that this offers is encouragement to experiment and try things for yourself. Your results may just delight you.

    Good Luck

    Ken
     
  12. Dzung Pham

    Dzung Pham Second Unit

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  13. StevenB

    StevenB Agent

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    Wait a second. I probably came across it somewhere before, but with the plethora of info on this site, I somehow forgot the answer to this question....Hooking up subs to your surrounds and rear channels? Worth it? Are there really that many LFE's emitted through the surround and rear channels that it would be worth dumping another half a grand into each of those channels via more subs?



    I am actually quite happy with my setup now, my two main towers (4ways) each house a 12" woofer, 12" super bass cone (sub?), 4.5" mid range, 2" tweeter, and 2" super tweeter. Sanwiched inbetween is my Boston Acoustic PV-600 sub which fills in those LFE's that the towers can't quite reach. The surrounds are also Kenwood JL 4-ways with nearly the same setup as the mains, but only 120 Watts as opposed to the 180 watt mains. In other words, the more I consider, the more I relize that I probably don't need any more bass, but an upgrade to an SVS would be nice over the next few months. If anyone may have interest in the BA sub I am using now which is just starting to get broken in and obvioulsy well taken care of, let me know and we can work something out in the very near future.

    Steve
     
  14. StevenB

    StevenB Agent

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    Wait a second. I probably came across it somewhere before, but with the plethora of info on this site, I somehow forgot the answer to this question....Hooking up subs to your surrounds and rear channels? Worth it? Are there really that many LFE's emitted through the surround and rear channels that it would be worth dumping another half a grand into each of those channels via more subs?
    I am actually quite happy with my setup now, my two main towers (4ways) each house a 12" woofer, 12" super bass cone (sub?), 4.5" mid range, 2" tweeter, and 2" super tweeter. Sanwiched inbetween is my Boston Acoustic PV-600 sub which fills in those LFE's that the towers can't quite reach. The surrounds are also Kenwood JL 4-ways with nearly the same setup as the mains, but only 120 Watts as opposed to the 180 watt mains. In other words, the more I consider, the more I relize that I probably don't need any more bass, but an upgrade to an SVS would be nice over the next few months. If anyone may have interest in the BA sub I am using now which is just starting to get broken in and obvioulsy well taken care of, let me know and we can work something out in the very near future.
    Steve
     
  15. Wayne A. Pflughaupt

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  16. Doug Smith

    Doug Smith Second Unit

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    I have become convinced that the way to go is to have one down firing and one side firing sub. Both music and HT are complimented. Don/t know why?
     
  17. Marvin E

    Marvin E Stunt Coordinator

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  18. joe logston

    joe logston Stunt Coordinator

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    i think that you should have one sub per channel, wend the satilites rolloff at the bottom and wend the subs take over the lows, right at the rolloff point it gives a dirertional sound singal, and you get a dementional sound feild with subs at each speaker and it makes a fuller enhanced experiance, for movies & music, cost & set up is a bitch though
     
  19. Chris PC

    Chris PC Producer

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    Wayne,

    SMALL and not LARGE. No sweat. I caught that too since it was in reply to my comment.

    Well, here in lies the ultimate problem that we all face when blending subwoofers with speakers.

    1) Subwoofers are best used singlely or placed together.

    2) Towers with low extension act at least similarly like subwoofers in their lowest octave in that they (2 full towers) interact and interfere with the subwoofer such that its messes with response causing peaks, standing waves and valleys and near nulls.

    Here is where I need some help. advice or comments from the audience:

    Using one sub and 2 towers set to SMALL in a room as an example:

    3) The higher the frequencies coming from 3 speakers in different locations, the fewer problems you have with response, ie peaks, standing waves and valleys or even nulls. The lower the frequencies, the more problems you will have with the sub and towers causing the above unwanted freq response. Even with a crossover. Remember, the ouput is lower because its rolled off, but its still there.

    4) The higher the frequency (80-100 hz or higher) the more directional it is. I have tested this blind folded many times and 90-100 hz becomes directional for me personally.

    So for many of us who have full range towers and one subwoofer, we're left with this:

    1) You should crossover the subwoofer low to avoid directionality.

    2) The lower you crossover the sub, the more interaction you're going to have between the sub and the two towers. Essentially, apart from the bottom octave that your towers cannot produce, there is going to be an overlap of frequencies at, above & below the xover which creates ragged response there.

    This leads me to believe that:

    1) Use a steep crossover. Not the only solution, as interactions at the crossover point will still need to be tweaked, especially considering each room is different.

    2) EQ your subwoofer

    3) Try to place the subwoofer closer to your towers

    What do you think?
     
  20. Steve Morgan

    Steve Morgan Second Unit

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    I have to agree with the corner loaded theory.I ran 2 very well thought of subs(Servo 15a/Von Schweeikert S/3)in different locations in a very large room (5000 cubic ft.)I always felt I was missing something on Bass intensive material even though the Servo was 3 ft. from listening position.I began reading the forum and with help from Wayne and other members I experimented with SPL's with 2 locations and corner loaded.I took readings with the subs seperated (opposite corners)and co-located (corner loaded)every time the corner loaded configuration gave a smoother, flatter response with a significant increase in spl at the prime listening position.After eq'ing with a BFD my bass response is about 75% improved in my HT area.If I had the shekels I would run full range speakers at each location and a dedicated LFE sub but WSR I ain't.

    Wayne YGM. Should I retake readings with the new pre/pro?
     

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