Does a riser need insulation?

Discussion in 'Home Theater Projects' started by AaronG, Feb 1, 2002.

  1. AaronG

    AaronG Stunt Coordinator

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    Hi guys,

    I'm just wondering if a riser needs to be built with insulation inside to avoid any sound problems. Will I hear an echo if the riser is basically hollow inside sitting on a cement floor?

    Thanks,

    Aaron
     
  2. Mike LS

    Mike LS Supporting Actor

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    I guess if your riser were 2 feet tall you might hear something, but if it's a "normal" size of 8 - 10 inches, there's really no need to insulate it.

    If it's sitting directly on a cement floor, it might be a good idea to put a piece of carpeting under the riser so to not have any vibration problems against the cement.
     
  3. RAF

    RAF Lead Actor

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    I carpeted the floor first and then built the riser to sit on top of it. That way if I remove the riser (I'm not planning on it) there isn't a gap where it once was.

    But I agree that anything under 1 foot high probably would not have sound issues.
     
  4. Nic K

    Nic K Extra

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    I would disagree with you guys on the need for insulation. The riser "acts" like a drum without any kind of dampening material. I used acoustic mat between my concrete floor and riser in addition to the cheapest R-11 insulation batts I could find. You will find this is the best way to go from an acoustic standpoint.

    Nic
     
  5. RAF

    RAF Lead Actor

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    It has been my experience that if you place the riser on a carpeted surface and then carpet the riser itself, there is not any problem with any resonances. Also, my riser is only about 5 inches high so this probably helps the situation too.

    And I have some serious sound "events" going on in the room with everything from dual subs to 7.1 sound.
     
  6. Nic K

    Nic K Extra

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    The height likely plays a part in the effects. My best recommendation would be to call up Acoustic Science Corporation at www.tubetrap.com (you can find their number there) and talk to Erik Veach. These guys are all acoustical engineers and can explain the details of this situation much better than I can.
     
  7. Dennis Erskine

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    Risers DO need to be insulated. You are creating resonance cavities that will be not helpful (unless you've done some very, very careful models and intend to create a resonator to resolve a bass response problem).
     
  8. Jay Mitchosky

    Jay Mitchosky Producer

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    I'm seeing mention of "normal" riser heights of 8-10" and I'm getting a little antsy. My room will be 23.5='" long by 17' wide by 8' high. The primary listening position (ie. the eyes and ears) will be 12.5' from a 96" wide 16:9 screen. Allowance for reclined position and some walking space places the rear seats at around 18' feet. I'm running these numbers off the top of my head. In order to create a clear sightline for the back row my riser needs to be 15" (follows a line that connects the top of the front row's head to the bottom of the screen). For those who have built risers what are your layouts and how did you determine riser height?
     
  9. Nic K

    Nic K Extra

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    Your sightline of utilizing a 15" riser may be correct if you have the screen positioned rather low. My room is very close dimensionally to yours. 8 high, 21 long, almost 16 wide. My screen ( would have to look it up to be sure, or measure) is about 2.5 feet above the ground and am using a 10" riser with no problems.

    Nic
     
  10. Pam W

    Pam W Stunt Coordinator

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    Our riser and stage are both insulated. The stage even has sand under the speaker/subwoofer area. I want no resonance cavities in my room - and if it weren't located over the garage, the entire stage would have been sanded.
    My $.02[​IMG]
    Pam
     
  11. Ron-P

    Ron-P Producer

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    I packed my risers with R-13. If you don't, your looking at a giant resonation chamber.
    Peace Out~[​IMG]
     
  12. Jay Mitchosky

    Jay Mitchosky Producer

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  13. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    I think a simple solution would be to use internal bracing and/or some insulation to prevent the panels from sounding "hollow".
    However, if the riser has insulation on the inside, it may act as a bass absorber. What happens is the large wood panel has a certain resonating frequency and will vibrate back and forth. The sound is then converted to "heat" energy when it hits the insulation, thus affecting the bass response. (Could be good or bad)
    If you have plain concrete exposed it may also create problems. When sound hits concrete, it adds a coloration to the sound due to the highly reflective surface.
    May I add the suggestion of solid wood (like side by side 2x4s with nails holding them in place), it will keep the solidity of the concrete surface, and just change its timbre. You can then use plywood subflooring on which you install the carpeting.
    Ideally, I'd say solid wood could be "best", but since that's not the cheapest option. I think what everyone else is saying could work for you. [​IMG]
     
  14. Nic K

    Nic K Extra

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    Jay,

    I can go measure my screen which is 100" diag FH, but why can't you move it up to 30" from the floor?

    Nic
     
  15. brandonchenry

    brandonchenry Stunt Coordinator

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    definately put at least fiberglass in. its cheap, and will help acoustically deaden your room anyway.
     
  16. brandonchenry

    brandonchenry Stunt Coordinator

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    This guy happens to be a notariable name on the subject, so he is definately worth listening to.
     

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