Subwoofer Placement

Discussion in 'Archived Threads 2001-2004' started by Matthew Perry, Apr 2, 2002.

  1. Matthew Perry

    Matthew Perry Stunt Coordinator

    Joined:
    Feb 28, 2001
    Messages:
    85
    Likes Received:
    0
    Trophy Points:
    0
    Hey

    Another question about placement.

    Just wondering, is it a bad thing to place you're subwoofer in the front of you're home theater?

    Any specific location in the front range?

    Any input would be greatly appreciated.

    If it helps my subwoofer is the Energy e:XLS10.

    Regards,

    Matt
     
  2. Jeff Pounds

    Jeff Pounds Second Unit

    Joined:
    Jun 6, 2000
    Messages:
    385
    Likes Received:
    0
    Trophy Points:
    0
    Matt,

    I think it will depend on your room.

    Since low frequencies cannot be localized, you should be able to place the sub anywhere in the room.

    However, there are external room factors that may cause some low frequencies to be localized.

    Also, in sub placement, there are also things like how the room is set up, aesthetics (if you have a spouse or significant other "approval factor").

    If you have no placement barriers, the best thing to do is set the sub in the primary listening position and then play a soundtrack with heavy, contiuous bass.

    Then walk around the room and find where you get the best bass response...that's where you should place your sub.

    Good luck!
     
  3. Matthew Perry

    Matthew Perry Stunt Coordinator

    Joined:
    Feb 28, 2001
    Messages:
    85
    Likes Received:
    0
    Trophy Points:
    0
    Thanks for the tip.
    I will find a good tone CD tonight and walk around the room in circles and find the best spot [​IMG].
    Perfect.....
    Regards,
    Matt
     
  4. Chris PC

    Chris PC Producer

    Joined:
    May 12, 2001
    Messages:
    3,975
    Likes Received:
    1
    Trophy Points:
    0
    Where will you find a "good tone CD"? I'm looking for one and I'm not keen on ordering one over the internet. Where will you pick up yours?
     
  5. Paul Clarke

    Paul Clarke Supporting Actor

    Joined:
    Jan 29, 2002
    Messages:
    998
    Likes Received:
    0
    Trophy Points:
    0
    Chris,
    You can buy them safely off of Ubid for less or you can order them safely direct from the makers themselves. You choose the payment method if you're leary of info disclosure. Go to www.Ubid.com or www.Testdisc.com
    I have bought and sold a zillion things off of the web without a single problem.
     
  6. ling_w

    ling_w Second Unit

    Joined:
    Sep 3, 2001
    Messages:
    426
    Likes Received:
    0
    Trophy Points:
    0
    You can't use test tones to do the walking around. It has to be something with a complex series of bass notes such as plucked bass moving up and down the scale. If you don't have suitable music, you might be able to try pink noise.

    The point is not to bet the most bass, but the most even bass. With the plucked bass note, the different notes should sound equally loud. With pink noise, there should be not freq sticking out or lacking.

    Also, you would have to crawl around, since you are trying to find locate the optimal sub position, and the sub is usually located near the floor.
     
  7. Steve Zimmerman

    Steve Zimmerman Second Unit

    Joined:
    Dec 6, 2001
    Messages:
    347
    Likes Received:
    0
    Trophy Points:
    0
    I respectfully disagree with part of what ling_w is saying. You need to measure (using a meter) the *entire* range of 1/3 octave frequencies in question from each spot in your room (and thus end up with a bunch of response graphs) and not simply a track of music.

    I agree that you're looking for the flattest response, not the loudest single note.

    --Steve
     
  8. ling_w

    ling_w Second Unit

    Joined:
    Sep 3, 2001
    Messages:
    426
    Likes Received:
    0
    Trophy Points:
    0
    Steve,

    I was only clarifying what Jeff was saying since it seems that the follow ups were moving toward test tones. Also, heavy continuous bass might be interpreted as bass drum, which only has 1 note.

    I personally do 1/3 octave warble tone measurements from various places in my room, but even that is not accurate at frequencies below first room mode. The true way is to move the sub to the new spot and re-measure. You could take measurement every 12" along the length of one wall and plot it in 3-D graph. This would show you how the peaks and nulls gradually build up as the sub moves along the wall and give you an better understanding of how freq, sub position and room size all interact with each other.
     
  9. Chris Tsutsui

    Chris Tsutsui Screenwriter

    Joined:
    Feb 1, 2002
    Messages:
    1,865
    Likes Received:
    0
    Trophy Points:
    0
    I've been putting my subs in the front left corner of the room with success.

    To me it would be inconvenient letting the sub orchestrate the room layout. (My room is pretty small and compact)
     
  10. Richard Greene

    Richard Greene Stunt Coordinator

    Joined:
    Mar 5, 2001
    Messages:
    148
    Likes Received:
    0
    Trophy Points:
    0
    The only test tones that fully excite room modes are

    steady state sine waves or a very slow sine wave frequency sweep such as Track 5 on the excellent Stryke.com Basszone test CD.

    Slow frequency sweeps also allow you to locate resonating objects in your listening room (including walls and floors).

    These room noises are responsible for easily audible distortion that is usually more important than harmonic distortion when it comes to your listening pleasure.

    Some people use steady state sine waves 1/6 octave apart to measure their subwoofers -- this usually smooths the frequency response deviations somewhat, especially if a room mode frequency happens to be located half way between two 1/6 octave test tones ... but the results are directionally correct.

    Warble tones and pink noise barely excite room modes because they don't stay at one frequency long enough.

    They are the test tones to use for frequencies above 100Hz. where room modes tend to be so dense that our ears "smooth" them away and they are not serious problems as they often are below 80Hz.

    My goal at home is the smallest bass frequency response deviations measured from my listening position using a slow sine wave frequency sweep. Without parametric equalization the bass frequency response deviations are usually greater than +/-10dB. Sometimes +/- 15dB. With parametric equalization the frequency response deviations can usually be reduced to the neighborhood of +/-4dB. to +/-6dB.

    My own listening room has a very broad room mode from below 40Hz. to above 50Hz. Because this loud "boom" covers such a broad range of frequencies, I am able to equalize it with the 40 and 50Hz. controls of a 30-band equalizer. But most

    room booms are narrow and need an equalizer band narrower than 1/3 octave, so a parametric equalizer is usually needed.

    I personally recommend placing a mono subwoofer in the corner in rectangular rooms. This results in maximum volume and no cancellations. All room modes are fully excited by a corner subwoofer ... but then you can use a parametric equalizer as a notch filter for the one (or two or three) room modes that are audible at the listening position.

    Some rooms have just one annoying room mode and there are ways to fight a single room mode without an equalizer:

    -For example, if your room has one annoying room mode, it is possible to use two subwoofers placed on opposite sides of the room to cause (partial) cancellation at that specific frequency. The result tends to be a narrow hole in the frequency response at the room mode frequency rather than a sharp peak (because the two subwoofers are out of phase at that specific frequency and there is cancellation

    at that frequency). As a result, the frequency response deviations tend to MEASURE larger than with a single corner subwoofer ... but the sound quality is BETTER ... because you've replaced an easy-to-hear narrow frequency peak with a difficult-to-hear narrow frequency trough in the frequency response. In some rooms it may be possible to eliminate two room modes through clever positioning of one or two subwoofers but this result will tend to apply to one seating position -- bass frequency response may deteriorate at other seating positions (but who cares about those folks?).

    In general, you can get a smoother bass frequency response and eliminate frequency peaks better with a parametric equalizer than with clever subwoofer positioning. But if you can get the frequency response deviations down to

    +/-6dB or better measured with a slow sine wave frequency sweep, the bass usually sounds good no matter how you obtained the results.

    Within the +/- 6dB. ... broad frequency peaks are easiest to hear, followed by narrow frequency response peaks, broad frequency response troughs and finally, the most difficult deviations to hear are narrow frequency response troughs.

    So its possible that a room that measures +/-5dB, but has a broad frequency response peak within that +/-5dB, will sound WORSE than a room that measures +/-8dB, but has well distributed narrow peaks and troughs within that +/-8dB.

    Measurements usually work, but not always.

    However, measurements almost always work better than ears

    if you apply the Theory of Recipriocity (place subwoofer on your chair and crawl around the room to place your ears at alternative subwoofer positions). I recommend a microphone rather than ears. If you want to use your ears for this methodology, listen to music, not test tones. Test tones are designed for microphones. not for ears!

    In addition to frequency response deviations, also important are satellite speaker - subwoofer integration

    and slow sound decay at room mode frequencies (bass traps can address the slow decay problem -- equalizers only affect the attack of a bass frequency).

    Room corners (or any subwoofer location that places the subwoofer more than a few feet from the satellite speakers) are at a disadvantage for subwoofer-satellite integration.

    Corner subwoofers work best with crossover frequencies of 80Hz. or lower, steep 24dB/octave crossover slopes, and parametric equalization. This type of set-up using parametric equalization has the potential to outperform the bass from a pair of non-equalized full-range speakers located well away from walls and corners (this is rarely an optimum location for subwoofer bass frequencies, but great for above 100Hz.). Even if the full range speakers cost $100,000/pair and the subwoofer cost less than $1000.

    That's how importnat the room is for bass frequencies.

    In the end all that matters is that the bass instruments sounds realistic without any annoying frequency peaks, the subwoofer is sonically invisible, and you don't even know a subwoofer is in the room until you turn it off. Most owners of A/V systems probably won't agree with me but I think many two-channel audiophiles would agree.
     

Share This Page