Setting Up Multiple Subs - An interesting read...

Discussion in 'Speakers & Subwoofers' started by MikeNg, Aug 31, 2004.

  1. MikeNg

    MikeNg Second Unit

    Joined:
    Jan 22, 2004
    Messages:
    440
    Likes Received:
    0
    Trophy Points:
    0
    Hi all,

    I ran across this white paper issued by Harman (as in HK, JBL, Infinity, Lexicon, etc.).

    Though a couple of years old, I thought it was an interesting read. For those who appreciate a methodical, logical approach to sound, I think you'll like it.

    The author's conclusion regarding number of subs and optimal location was interesting. What do you think?

    Mike
     
  2. MikeNg

    MikeNg Second Unit

    Joined:
    Jan 22, 2004
    Messages:
    440
    Likes Received:
    0
    Trophy Points:
    0
    50+ reads, but no one has an opinion?
     
  3. Jon W.

    Jon W. Stunt Coordinator

    Joined:
    Jul 31, 2004
    Messages:
    121
    Likes Received:
    0
    Trophy Points:
    0
    Well I found it very interesting. I kinda run 4 subs now. My NHT VT-2.4 mains are being bi-amped with a NHT SA-3 sub amp and I have 2 Klipsch KSW-15 subs all running from the LFE output. My Klipschs set in front of my mains now but I want to set them in the back corners for experimentation. The problem is I want to upgrade the subs soon and hate to go through the trouble.

    Here's a picture of my small room...
    http://home.earthlink.net/~whiplush/...omeTheater.jpg
     
  4. Brian L

    Brian L Cinematographer

    Joined:
    Jul 8, 1998
    Messages:
    2,918
    Likes Received:
    15
    Trophy Points:
    610
    This link gets posted and quoted from time to time....maybe every has said their bit?

    Interesting reading nonetheless.

    BGL
     
  5. Kevin C Brown

    Kevin C Brown Producer

    Joined:
    Aug 3, 2000
    Messages:
    5,712
    Likes Received:
    0
    Trophy Points:
    0
    Old news for a lot of us... [​IMG]
     
  6. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Not only old news, but not necessarily correct assumptions for most HT rooms.
     
  7. dave alan

    dave alan Second Unit

    Joined:
    Aug 30, 2002
    Messages:
    256
    Likes Received:
    0
    Trophy Points:
    0
    I agree with BruceD (on more issues than the sited white papers, BTW).

    I feel the same about these white papers as I did when I read them about a year and a half ago.

    It's an ideally sealed room, no satellites to integrate with, which means filter slopes, phase, placement in relation to the sats, calibration, configurations, etc., etc., are missing from the equation.

    I wish I had the equipment, room and dough that study cost.
     
  8. BruceD

    BruceD Screenwriter

    Joined:
    Apr 12, 1999
    Messages:
    1,220
    Likes Received:
    0
    Trophy Points:
    0
    Dave, thanks for the kind comments.

    Yea, I'd be like a kid in a candy store with all that test equipment too.

    I have just enough test equipment, but at least it serves me well.
     
  9. Wayne A. Pflughaupt

    Joined:
    Aug 5, 1999
    Messages:
    6,123
    Likes Received:
    40
    Trophy Points:
    6,610
    Location:
    Katy, TX
    Real Name:
    Wayne
    I’m with Dave and Bruce on that paper. Any study of this kind is only relevant in the room it was performed in, and it’s beneficial to you only if your room is identical. But even that might not be enough - Dave’s points about the missing satellites, crossover slopes etc. make it even less relevant to the rest of us.

    Regards,
    Wayne A. Pflughaupt
     
  10. Richard_M

    Richard_M Second Unit

    Joined:
    Feb 8, 2001
    Messages:
    265
    Likes Received:
    0
    Trophy Points:
    0


    Bruce, at least you use your test gear, I bet some of these organisations have test gear bought on a whim, sitting around as a paper weight.
     
  11. Richard Greene

    Richard Greene Stunt Coordinator

    Joined:
    Mar 5, 2001
    Messages:
    148
    Likes Received:
    0
    Trophy Points:
    0
    The white paper appears to be based on scientific principles but the science is faulty and the conclusions almost worthless to the average home theater owner.

    The paper should be deleted from the Harman website because it detracts from the excellent Floyd Toole papers at that website.

    The purpose of the paper is to determine how to create a consistent frequency response from seat-to-seat within a large section of a large room. This might apply to a real theater too. Consistent does not mean flat.

    What we really want to know is how to create a relatively flat bass frequency response at our seating position (and at nearby seats). That's not a goal of the paper.

    The recommendation of four subwoofers does not account for the difficulty of integrating subwoofers all around the listener with the sound coming primarily from the front three speakers.

    Finally the worst fauilt of this so-called "white paper" is that it is based entirely on a finite element model and the RECOMENDATIONS WERE NEVER TESTED IN A REAL LISTENING ROOM. That's incredibly bad "science".

    In a Usenet post, subwoofer tester Tom Nousaine wrote that he tested the four-subwoofer recommendation in a real room and found it inferior to a subwoofer in a corner.

    I'll add that a subwoofer in a corner is easily outclassed by a subwoofer placed near one of the main speakers with large bass traps in all the corners and a parametric EQ used to cut bass peaks at your listening position.
     
  12. Kevin C Brown

    Kevin C Brown Producer

    Joined:
    Aug 3, 2000
    Messages:
    5,712
    Likes Received:
    0
    Trophy Points:
    0
    I have also talked with a number of experts, and they seem to agree that *most* (not all, but most) of the time, a single sub in the corner is better than multiple subs. ??

    Theory does suggest that multiple subs can even out freq response problems due to room effects, but in reality, it's just too difficult to integrate everything together. ??
     
  13. Brian L

    Brian L Cinematographer

    Joined:
    Jul 8, 1998
    Messages:
    2,918
    Likes Received:
    15
    Trophy Points:
    610
    Science be damned[​IMG]

    Right now I am experimenting with my HSU 1225 behind my couch, and a older Klipsch 8" sub in the front corner.

    I have EQ'd them separately, and played around with the individual levels and crossovers to make it so I can not localize the sub behind me, even with 2CH music.

    However, I have not been brave enough to actually measure the summed output at the listening position.

    Having the HSU behind the couch is providing me with the most intense, room shaking bass I have ever had...I am having too damn much fun to whip out the test tones to find out how hosed my room response really is!

    BGL
     
  14. dave alan

    dave alan Second Unit

    Joined:
    Aug 30, 2002
    Messages:
    256
    Likes Received:
    0
    Trophy Points:
    0
    Brian,

    NOW you're talkin'.

    Put THAT in your white papers!! [​IMG]

    Fun is something you rarely see anymore...Great Post!

    Dave
     
  15. dave alan

    dave alan Second Unit

    Joined:
    Aug 30, 2002
    Messages:
    256
    Likes Received:
    0
    Trophy Points:
    0
    BTW...I've used 2 subs for 2 years. I have a response of +4/-3 to 14 Hz at the LP...no EQ.

    Must be a magic room.
     
  16. Kevin C Brown

    Kevin C Brown Producer

    Joined:
    Aug 3, 2000
    Messages:
    5,712
    Likes Received:
    0
    Trophy Points:
    0
    Dave and Brian- But ... Have you used an RTA to look at the response around the room? I'm not after subjective impressions, I'm after quantitative info. [​IMG]
     
  17. Rutgar

    Rutgar Second Unit

    Joined:
    Jan 17, 2004
    Messages:
    495
    Likes Received:
    0
    Trophy Points:
    0
    I have also used two subs for years, and have had wonderful results. Not once, when turning one of them off, has the bass gotten better. The two subs together have always been an improvement. I recently got a Velodyne Digital Drive 18. It has a built-in RTA, and comes with a microphone. After setting it up, my bass sounded great, and I had a fairly smooth response. I also kept one of my older Velodyne ULD-15's. So, I decided to bring it into the mix as well. As usual, turning on the ULD-15 improved the sound. And the response curve from the DD-18's RTA, reflected this as well. My Conclusion: Two Subs is almost always better than one. I only say "almost" because I'm sure someone, somewhere can and will find an instance where one sub is better than two. However, I have never experienced this instance.
     
  18. Brian L

    Brian L Cinematographer

    Joined:
    Jul 8, 1998
    Messages:
    2,918
    Likes Received:
    15
    Trophy Points:
    610


    Seriously, I do intend to take measurements of the summed output, and if they are crap, I will tell you all about it (honest!).

    But I am not kidding when I say that I am having a blast with this arrangement. The low end when watching a film like U571 is astounding.....I have never had it this good in my room. Dr.Hsu is on to something when he suggests trying sub placement close to your listening position.

    As for the fact that my impressions are all just questionable, subjective, BS....guilty as charged! But, it sure seems to be producing pleasing results in my room.

    I was initially having problems localizing the sub behind the couch (using an ICBM at 80 hz, standard 12dB/12dB symmetrical crossover). I could live with it for films, but not MC or stereo music.

    So, taking a suggestion from another recent thread about using the sub crossover in conjunction with the crossover in your AVR (in my case, the ICBM), I engaged the crossover in the HSU amp, and dialed it back to an indicated 60Hz.

    Bingo. I can no longer localize the sub behind me, but the tactile affect of having it that close to me is incredible with the right content (again, U571, Titan AE, T3.....).

    So, maybe the ticket for close proximity sub placement is a lower than 80Hz crossover, or maybe a super steep slope, or both? Don't know, but I do know what seems to be working at the moment.

    But its a great blend for music as well. I am just not hearing anything objectionable, and I have been chasing this sort of subjective low end response for a long, long time.

    It is possible (maybe even likely) that my low end response is not as flat as it was with one EQ'd sub in the front of the room. But I will say this....no matter what the measurements show, I am right now inclined to leave things where they are...I am having that much fun with it this way.

    BGL
     
  19. Kevin C Brown

    Kevin C Brown Producer

    Joined:
    Aug 3, 2000
    Messages:
    5,712
    Likes Received:
    0
    Trophy Points:
    0
    I think about it this way. *Maybe* things can be set up with mulitple subs so that everything is in phase at one position in the room. But as soon as you move away from that one position, bam, because of the long wavelengths involved, you are instantly out of phase between the two subs at any other location. Here's the other way I think about it:

    a) each speaker interacts with every other speaker
    b) each speaker interacts with each sub
    c) each speaker interacts with the room
    d) each sub interacts with the room

    And now another sub is added? So all the interactions increase again (degrees of freedom kind of thing, to potentially make things *worse* [​IMG] ). And all that has to be optimized. Kind of like a system with many equations *and* with many variables, and the only solution is trial and error. Which is not impossible, but I still kind of believe that with the placement limitations most of us have, *and* with real live rooms, it is almost always easier to use a better single sub than to divide up that money in between two subs.

    Brian- Let me know if you ever do measurements. My problem with subjective impressions is that hey, if one sub is really good, human psychology says that, Hey! Two must be even better. But I have a feeling that measurements don't bear that out in most cases. And I *have* an RTA, and I am having enough problems trying to properly characterize my room with just one sub...

    My latest try was this:

    a) 80 Hz x-over compared to 60 Hz
    b) 5 different locations

    At each location

    c) left speaker and sub
    d) right speaker and sub
    e) L & R speaker and sub
    f) all speakers and sub

    If you add all those up, that's 40 measurements to look at and combine in different ways to look at overall response. And *then*, after I had done all this, I decided I *also* needed to do:

    At each location:

    g) left speaker alone
    h) right speaker alone
    i) sub alone
    j) L & R speakers (no sub)
    k) all speakers (no sub)

    I have two dips, one at 51 Hz and one at 134Hz. I kind of figure the first is due to mostly sub interaction with the room, but the second is not primarily due to the sub (so it probably won't be fixed by adding another sub anyway). And then once you figure out that each location can be *changed* to try and optimize things (speakers and subs and seating locations can be moved), the whole thing gets very big very fast.

    So anyway, I gave up and figured if I have $X money to spend, it's better spent on one sub in the corner. [​IMG]

    So then you could say: measurements be damned, I'm going to do what sounds best to me. And that is obviously just as valid an approach. But that's not me. [​IMG]
     
  20. Rutgar

    Rutgar Second Unit

    Joined:
    Jan 17, 2004
    Messages:
    495
    Likes Received:
    0
    Trophy Points:
    0


    I've heard many people put this view forward, and in theory it sounds like it makes sense. However, in practice, it doesn't really hold. In all of the years of running two subs, I've never ran into a problem with the subs canceling each other out, and creating a "hole" in the bass. If anything, just the opposite happens. The two subs reinforce each other, and actually help smooth things out. As I said before, my experience has always been positive when adding a second sub. And, my DD-18 proves what I've been experiencing.
     

Share This Page