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Thread: Acoustic Panels - location questions

  1. #1
    Senior Member Ed Zeppeli's Avatar
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    Acoustic Panels - location questions

    I have four acoustic panels I just purchased for a song so I couldn't refuse.

    My room is about 14' by 34' and I'm listening from about 13' away. Speakers are placed on the short wall so there's about 20' of fairly open space behind the seating.

    The panels are 18" by 60".

    When I see photos of panels mounted at the first reflection points they are usually upright. My basement side wall has a protruding foundation which limits the height of open wall space for the upright positioning. If they don't fit that way would the panels work hung horizontally?

    Also, since I have four I was debating putting the other pair on the ceiling as clouds. Is this a good choice for secondary panels and if so do I hang them at first reflection point or directly above the listening position a la mixing studio.

    There are indeed a million opinions on these topics online but I'd like to hear from some of the members here about their experiences if possible.

    Regards,

    Warren
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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    Senior Member Ed Zeppeli's Avatar
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    Here is a 1/6th octave avg of woofs and subs taken from three mic positions around the listening position.

    There may be some bass traps in my future as well...

    Name:  avgwoofsandsubs.jpg
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    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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    Administrator Mr. Widget's Avatar
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    Tell us more about your panels. Absorbers, diffusers, a combination? If absorbers only, what is the material and thickness?



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    Senior Member Ed Zeppeli's Avatar
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    These are the panels. Their 'claimed' absorption rates are perhaps optimistic but I don't doubt that they will be an improvement over straight drywall.

    https://www.snapav.com/shop/en/snapav/episode-reg%3B--acoustic-panel-18-x-60-x-2
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

  5. #5
    Senior Member Ed Zeppeli's Avatar
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    Click on Support > Manuals and Guides to see the absorption rates.
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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    As you say, there's a thousand ways to move forward on this topic. I might first try spanning the intersection of the front wall (behind the speakers) and side walls, floor to ceiling if you have 80" of height, and see if that helps the bass. Straight diffusers are generally most appropriate for first reflections unless you're trying to tame something.

    Edit: Just noticed your post says 60"x18". The link said 24"x40". Sorry. In any event, spanning the intersections of walls/ceilings can be a good place to start.

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    Senior Member Ed Zeppeli's Avatar
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    Thanks Rusty. Yes, mine are 18" x 60" fixed the link.

    I should mention there are windows behind the speakers but I've put up some drapes.
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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    Senior Member Ed Zeppeli's Avatar
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    When I implement the house curve in REW and look at what filters it suggests there are none required in the bandwidth covered by the SAMs.

    ...and so it does make me wonder if I wouldn't be better off placing the panels at woofer height in the position of first reflection rather than at ear height.
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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    Senior Member 1audiohack's Avatar
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    Also posted on your measurment page.

    If you had a cardioid mic you might be able to "look" at your estimated reflection points and measure the spectral content of the bounce and see what your panel placements do for you

    Barry.
    If we knew what the hell we were doing, we wouldn't call it research would we.

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    Senior Member Ed Zeppeli's Avatar
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    Interesting idea. I do indeed have a few cardioid or hyper-cardioid mics around here somewhere.

    There seems to be some consensus that the ETC plot is a good way to check for reflections.

    I put a few panels up at the early reflection points using the mirror trick and below are the results. Blue = before. Red = After.

    You can see at about 4, 7 & 9ms there is a bit of effect where the -20dB outcome is attained. Otherwise, not too much to crow about there.

    You can see the three spikes in the first 4 ms are quite unaffected by the acoustic panels. Those short distances mean the sound is travelling an extra .5' to 3' further to get to the listening position.

    I have no idea what would cause that. Baffle step stuff?

    Name:  ETCLHornBeforeAfter.jpg
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    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

  11. #11
    Senior Member Ed Zeppeli's Avatar
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    Looks like it could be a floor reflection; at least in the case of the woofer.

    Name:  mirrormeasure.jpg
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    The measurement with the laser pointed at the mirror and hitting the woofer is anywhere from .4 to 1.5' different than one pointing directly at the woofer.

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    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Ed Zeppeli View Post
    You can see the three spikes in the first 4 ms are quite unaffected by the acoustic panels.
    Realize those panels will have zero effect below a few hundred Hz. Not sure what their absorption curves look like, but you need about 6" thick panels to get deep into the upper bass.


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  13. #13
    Senior Member Ed Zeppeli's Avatar
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    Yes I realize my confusing post now. The photo is of the woofer but the graph is showing the ETC of the left horn only. The distances will be a bit different but floor bounce is likely my main culprit here for the horn reflections.

    Regards,

    Warren
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

  14. #14
    Administrator Mr. Widget's Avatar
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    Ah, yes... looking at the bottom of the plot it does clear that up. Could be floor or other surfaces.

    In addition to finding the best location(s) I'd guess you need significantly more surface area covered to get a significant effect.


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