Sub placement and standing wave help please.

Discussion in 'Speakers & Subwoofers' started by Arthur S, Jul 5, 2003.

  1. Arthur S

    Arthur S Cinematographer

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    If I am not mistaken, it is generally considered that you get the most volume and the flatest frequency response out of a sub if you put it in a corner. Where I have mine sitting now is giving awful standing waves. Very low volume at the listening position compared to other listening points in the room and in other adjoining rooms.

    i don't want the sub in back of me and that doesn't leave many choices. I guess I will try moving it out of the corner but the magnet in the sub could discolor my TV if the sub is too close.

    Any suggestions?

    Thanks in Advance

    Artie
     
  2. CurtisSC

    CurtisSC Screenwriter

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    Actually I think that is incorrect. In a corner, I do not think it is flattest response.

    Someone metioned to me once to cut the room into thirds, and place the sub along one of those cuts.

    Then there is the crawl method. Place the sub in the listening position, crawl around the floor and listen for where the best sound is, and then place the sub there.
     
  3. John Garcia

    John Garcia Executive Producer

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    Placing the sub along a side wall should give you the flattest response, however it will not necessarily be the lowest (frequency) or the highest SPL, and it will be just as prone to standing waves. A corner will reinforce certain frequencies, but your room shape may not benefit from that. If it is a forward firing sub, try turning it in slightly different directions in the same corner. If it is down firing, try moving it a few inches at a time.

    I have a similar issue in my room, and it took me weeks of playing around with placement to get response that makes me happy.
     
  4. Terry Montlick

    Terry Montlick Stunt Coordinator

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    You do typically get the most volume by putting subs in the corner, by fully exciting all the room modes (which give you standing waves). But you definitely DON'T get the flattest response. Back in the old days, before subwoofers and powerful bass, people weren't to picky about how they got their bass. Any sort would do, the more the better. That's where the corner placement idea came from. Now we have more than ample bass power, so we can do things right.

    Curtis gives the most effective way to find the best subwoofer position - the "crawl" method. A real-time frequency analyzer can be useful for this, but there's nothing wrong with simply using a pair of good ears.
     
  5. scott>sau

    scott>sau Stunt Coordinator

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    The placement issue has been answered, I would just add that the key is experimentation. Also it is best to place a sub in the first half of the room and avoid placing near the center channel.
    About standing waves: "A general rule with subwoofers is to use twice as many as you think you will need. Dual subs placed asymmetrically reduce standing waves and yield the smoothest response".
    The above quote was from a CEDIA Expo I attended called: "Home Theater, Essential Elements" in 1995, by Russ Herschelmann. (One of CEDIA's founding fathers).
     
  6. Arthur S

    Arthur S Cinematographer

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    Thanks to all for the suggestions.

    John Garcia: Thanks, for some reason the side wall never even crossed my mind, I was only thinking about the front wall

    Curtis and Terry: Thanks for reminding me about the crawl.

    Scott: Thanks for the dual sub suggestion. I've been thinking about a Velodyne HGS-18 MK II for several years. While I probably won't buy 2 of them (or even one), a second sub typically does give you about 6 db more volume.

    Artie
     
  7. Kevin C Brown

    Kevin C Brown Producer

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    Some very excellent articles here:

    http://www.harman.com/wp/index.jsp?articleId=122

    Like others have mentioned, corner is best for raw output, but not for the flattest freq response. According to some of the articles above, the best place for a single sub is 1/2 way along one of the walls. Best compromise between betweem output and freq response.
     
  8. Richard Greene

    Richard Greene Stunt Coordinator

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    Subwoofer position is an interesting topic because everyone seems to have a strong opinion, seems to believe there is one right answer for every room, and almost nobody makes measurements to collect data that would lead to at least a Rule-of-Thumb for rectangular rooms.

    The first goal should be a subwoofer position where the subwoofer is sonically invisible (so well integrated with your other speakers that you don't realize it's playing ... until you shut it off.) The quantity of output above 80Hz. determines how "sonically visible" a subwoofer will be.
    If the subwoofer has significant output above 80Hz. it should be located quite close to either the left or right speaker, or else it will be sonically visible as a separate sound source (not well integrated with the left and right speakers).

    The answer to subwoofer positioning in a specific room is measurement, not speculation or theories not supported by data. In general, the subwoofer position that results in the smallest frequency response deviations (+/- X dB) measured using a slow sine wave frequency sweep from 20 to 100Hz. using a sound meter will be the best sounding subwoofer position ... but that position must also be in the vicinity of the left or right speaker so the sub integrates well -- even if the positions measure well,
    a sub should not be located six feet away from the main speakers, or on the other side of the room where it will not integrate well with the other speakers.

    A test CD such as Stryke.com's BassZone CD and
    Radio Shack analog sound meter can be purchased for less than $50. It is almost impossible to find an optimum subwoofer position by ear (I suppose if the wife says there are only two alternatives, "here or there", you might pick the best one by ear).

    The sad truth is that in almost all home listening rooms there is no subwoofer position with a smooth frequency response. +/-10db is typical at the listening position using a slow frequency sweep to excite standing waves.

    For well shaped rooms with well distributed room mode frequencies, there is an advantage to placing a single mono subwoofer in the vicinity of a room corner, as long as the sub is not more than 2-4 feet from either the left or right speaker. However, if the room is not well shaped for bass (square, near square, or the length/width/height are multiples of each other such as 24 x 16 x 8), a subwoofer in the vicinity of a room corner (where it will strongly excite all room standing waves) is usually a bad idea.

    This article explains a lot:
    http://www.harman.com/wp/pdf/Loudspeakers&RoomsPt3.pdf
     
  9. Richard Little

    Richard Little Stunt Coordinator

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    Wow! Moved my SVS 16-46pc+ from the corner by the front speakers to the side wall at about mid point of the wall. The room is not far from square (14x16). It made a huge difference for me. I had to turn the gain down because it was scaring me. It also helps that it's sandwiched between the wall and the side of the couch I watch from. Not only is it louder, you can feel every bit of the low end base. Rewatched AOTC and grinned from ear to ear. Company commented that it seemed much smother.
     
  10. Brett DiMichele

    Brett DiMichele Producer

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    I agree with Rich Greene fully!


    I run my sub up to 120Hz (My mains with thier subs turned
    off) the Mids are lowpassed at 100Hz. With the sub placed
    right beside my Right Main firing into the corner (cone
    aimed at corner) I get seamless blending. Infact it honestly
    sounds like there is no sub at all.. For music it's just
    full sounding and the sub never draws attention to it's self
    at all (the way it should be). The room is 16.5L x 13W x 8H

    Works for me [​IMG]
     

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