Sub Placement & Setup by Tom Nousaine

Discussion in 'Speakers' started by Chu Gai, May 7, 2004.

  1. Chu Gai

    Chu Gai Lead Actor

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    According to Tom Nousaine, corner placement of a sub is generally the best position. This can be flush against a corner or out a few inches so long as we're not talking about a couple of feet. This is not to say that all corners are equal. For example, it should not be in a corner that is symetrically opposite (kitty corner) a room opening. In the one example that Nousaine found where direct corner placement wasn't the best (an open loft), the best response was obtained 2 feet out from either one of the two closed corners. A closed corner was taken to mean one that had 5 feet of more of solid wall to either side of the subwoofer.

    In terms of what might be considered the best listening postion, Nousaine has found that is generally between the long walls and about 5 to 6 feet from the wall located behind the listener. Further, the subwoofer should be crossed over below 100 Hz. The goal, as TN sees it, is to obtain the flattest frequency response.

    He bases his opinion on measurements that he has done on a variety of rooms over 3 years. His finding, after measuring a variety of rooms (low frequency response maps in 2 foot intervals) with different subwoofers, supports the general statement that placing a subwoofer in such a postion provides the following benefits.

    1) excites all the modals in the room which gives the flattest freqency response at all listening positions. A consequence of this is that phase response and signal timing are also optimised. While some may take issue with that of signal timing by arguing that arrival time can be affected by placement, consider that studies have shown that approximately 100 milliseconds is needed @ 100 Hz which is about 100 feet. If you consider the room you're putting your subwoofer in, unless you're dealing with distances that long, then you haven't a problem.

    Other positions will cause some room modes to be not excited and this results in suckouts which are holes in the frequency response.

    2) provides the deepest extension

    3) maximizes output

    As a side note, he also found that many mapping programs, such as CARA, gave erroneous results and predictions when dealing with low frequencies. They correlated poorly, if at all, to the actual experimentally measured results. Consequences of using such programs blindly might suggest placement of subwoofers in decidedly non-optimum locations.

    Further reading, if anyone chooses can be found in the following 2 publications. They may be available at your local library through the inter-library loan program.

    January 1995...Stereo Review..."Subwoofer Secrets"
    June 1996...Audio..."Placing the Bass"

    As an additonal resource, I've taken the liberty to quote from an article that was published in Sound & Vision by TN.

     
  2. Ned

    Ned Supporting Actor

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    Good info. You'd be surprised how many people still believe the corner=boomy myth.
     
  3. Kevin C Brown

    Kevin C Brown Producer

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    Chu- Awesome. But...


    To include absolute numbers like "5 to 6 feet" I don't think works. I'd rather see something like "1/3 down the length of that wall."

    The modes, and *where* they are excited in the room are based on the room dimensions, so distances wrt room dimensions (i.e., ratios or fractions thereof) would be the best way of putting it.

    I would think, anyway. [​IMG]
     
  4. Chu Gai

    Chu Gai Lead Actor

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    What I wrote about was what TN determined and those numbers are his findings or thoughts Kevin. He also stated that if for some reason one couldn't use corner placements that the next best position was literally 'in your face'. I wanted to present this largely because many people ask this question and also not many will go to the extent that he did insofar as mapping a room. While I think one can't say with 100% assurance that this will always work, it's TN findings that it does so in the vast majority of cases. Consider it like an 'odds' thing. The odds are overwhelmingly in your favor for corner placement. Hopefully there was enough information presented about corners that people can look at their own rooms and get a better feel if they've got it just about right.
     
  5. Richard_M

    Richard_M Second Unit

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    Thanks for the post Chu [​IMG]

    Can someone explain this sentence to me please?



    I am curious as to why spikes are useless.
     
  6. NickSo

    NickSo Producer

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    Whoa... so corner loading doesnt really produce boomier bass?
     
  7. dave alan

    dave alan Second Unit

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    I guess this passed as informative 9 years ago.

    Credit where it's due, but Tom might consider an update to this article.
     
  8. Kevin C Brown

    Kevin C Brown Producer

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    I don't believe an update is necessary. The behavior of low frequency waves and interations with rooms hasn't changed, unless someone changed the laws of physics. [​IMG]

    Chu- Touche. Yes, I have heard that the next best place for a sub, is as close to the listening position as you can get.

    The "old" recommendation for how to place a sub: put it *at* the listening position. Then walk (crawl) around the room and walls, and listen for the deepest, strongest, cleanest bass. Then put the sub there. You sit at the listening position. Or, just put the sub as close to you as you can.

    I read *another* article once about spikes. Statistical test with speakers (not subs) to test the effect of spikes vs just sitting on the carpet. Conclusion: no effect. The presumption was: better "conduction" to the floor with spikes helps in low frequencie response. But with real listening tests, nobody could hear the difference. Speakers not subs, but that's what they found.
     
  9. Chu Gai

    Chu Gai Lead Actor

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    Well the issue of spikes being beneficial insofar as sound is a debateable topic Richard_M. Perhaps it would serve better as a separate thread however if you feel like doing it then by all means do so. The only thing I'll say about it is that it gets rather amusing reading how Company A's unique proprietary formulation is audibly superior to those which may be provided by the manufacturer.

    TN is still saying the same thing dave alan and as far as I know, still does periodic measurements on subs and rooms to map things. He is a fairly meticulous and thorough person who calls them as he sees them. Kind of like ongoing research in the sciences that confirms previous work. As Kevin pointed out, a sub is a sub and low frequencies are low frequencies. While the rooms that we all have are different that does not change the fact that optimum excitement of modals occurs in corners. This doesn't mean your room is going to have a perfectly flat FR. For most of us, placements of speakers are compromises. This approach seeks to make the best of a situation. 2+2=4 That was the answer millenia ago and it is now. Except for some places in Wisconsin I think where they've implemented fuzzy math. In that case 4.2 is close enough. Oy!
     
  10. Richard_M

    Richard_M Second Unit

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    Thanks for the reply Chu...



    I was just curious that was all, as I had not heard that spikes were an issue with subs before reading Tom Nousaine's article.
     
  11. dave alan

    dave alan Second Unit

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    I certainly wasn't meaning to say that low frequency physics has changed in the past decade.

    I mean that adjusting a subwoofer's low pass filter to full range mains using a stereo pink noise disc and your ears is a bit dated.

    I haven't 'found that the phase control functions like a 2 position switch, suddenly changing and staying that way through the rest of the settings'.

    I also haven't found that optimal settings regarding sub setup results in the sub measuring 3-6 dB hot when checking the levels with an SPL meter (which we all know now is more like 6-10 dB hot in reality).

    And...if the notes on recordings of acoustic bass vary in ways that don't correspond with the music, try turning the sub's crossover up or down a little, or if it tends to boom, turn the level down a little.

    In fact, this setup guide would be of little use today...it needs to be updated.
     
  12. Chu Gai

    Chu Gai Lead Actor

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    Well I don't know how to answer that dave. Nousaine's email address (a matter of public record) is nousaine@aol.com and he frequently posts on USENET. Sign up and direct your inquiries with a posting to his name on something like rec.audio.high-end and maybe he or others will comment on your observations.
     
  13. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    >>>I don't believe an update is necessary. The behavior of low frequency waves and interations with rooms hasn't changed, unless someone changed the laws of physics
     
  14. Brian L

    Brian L Cinematographer

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    Just the other day, I was re-reading hard copy of an article I downloaded in '95 that Tom wrote in Stereo Review...probably one of the articles mentioned here.

    Damn good stuff. IIRC, when discussing adding a second sub, he mentioned placing it right near the prime listening spot, perhaps behind the couch if possible.

    I think he also offered the same advice that Dr. Hsu offers; even with 1 sub, place it in a corner behind the listener, or again behind the couch.

    I have been wanting to try that, but just have not gotten around to it.

    BGL
     
  15. Andrew Testa

    Andrew Testa Second Unit

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    I can believe that spikes aren't as important for subs. The cabinet mass is usually fairly significant, so you'd expect good coupling to the floor just from the weight. Spikes would be even less useful on downfiring subs, since the drivers produce no lateral motion in the cabinet. The only thing that may have changed since this article was written is the introduction of the 15 and 18 inch large excursion drivers. In some implementations these may produce enough reaction force that spikes would help. And his advice to not apply spikes until after you've decided on a final position is merely common sense: you can't shove that heavy box all over the room once the spikes are attached.

    I plan on adding spikes to my Adire Tempest, mostly because the box isn't as aggressively built as some I've seen, and it's sitting on a very thick carpet where I can get some rocking of the box by pushing on it. Spiking my Adire Kit281s was mandatory. They were very wobbly on that carpet, and had to be coupled rock solid to the concrete to perform their primary duty as cat perches.

    Andy
     
  16. Bill Blank

    Bill Blank Stunt Coordinator

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    Andrew,

    Spiking your sub, your speakers, your stands, your equipments racks, etc. for the reason you gave (stability) is perfectly fine and I doubt anyone would argue with that. Tom was just stating that spiking a sub (and SVS has confirmed this in their own tests) provides no audible benefits.

    I like Tom because he never gave into a lot of the audio voodoo that plagues this hobby. I'd love to meet the guy that came up with those metal "beaks" you see on the top of some speaker cabinets. He must be laughing all the way to the bank!

    Bill
     
  17. Dan Stone

    Dan Stone Stunt Coordinator

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    Floyd Toole provides quite a bit of data with his research and also makes for an interesting read in additon to studying Tom Nousaine's material:

    http://www.harman.com/wp/index.jsp?articleId=default

    He recommends starting with the sub in the corner, but also provides some thoughts and data as to why this may not always be the best.
     
  18. Chu Gai

    Chu Gai Lead Actor

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    This is true. However the rub is, will the individual be prepared to go through the same lengths as TN and map the room in say 2 foot intervals to determine the optimum location? Or will the significant other say something like...'Don't even think of putting that 'thing' over there...I told you that you could get it, now stick it in the corner for Crist's sake'?
     
  19. Andrew Testa

    Andrew Testa Second Unit

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    Bill,

    I may not have expressed it clearly, but I was actually agreeing with this:



    I meant that the relatively huge mass of most sub cabinets is going to make spiking redundant, combined with lowered ability to hear distortion at low frequencies. I wouldn't expect spiking to be audible for subs unless a really wimpy cabinet was used with a Maelstrom, where the cabinet danced across the floor like an old washing machine.

    Andy
     
  20. Wayne A. Pflughaupt

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    Hear, hear.

    I’ve used Nousaine’s writings from Audio and Stereo Review as reference material to many of my posts here over the years, for precisely that reason: He’s about the only one who conducts anything resembling scientific testing in real-world environments, usually with response plots. Others offer lots theory, often very plausible, but no measurements.

    Case in point: In weeding through my old hi-fi mags yesterday, I came across an Audio article from February 1994 advocating the benefits of stereo subs. Not a response plot to be found.

    Regards,
    Wayne A. Pflughaupt
     

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