Room Treatment/Room Acoustics

Discussion in 'Sound Science' started by Fuzziekiwi, Dec 13, 2017.
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  1. Fuzziekiwi
    I'm just learning about these subjects since I recently bought studio monitors for casual listening use.

    The way my room is setup here, how does this impact the sound? Rear ported JBL LSR305, placed about 4 inches from the walls. I assume bass response is a little higher than it should be because of the corners behind it and the wall is pretty close. What can I do in the future to improve sound?

  2. bigshot
    You're speakers are toed in too far. They should join in the middle to create a flat plane in front of you. At that sharp of an angle it gets all mixed up in the middle. If the bass is too boomy, it probably is because you are in a corner. It might work better against the wall on the left, although you'd have less work space.
    Last edited: Dec 13, 2017
  3. Fuzziekiwi
    So essentially move them so the back is aligned with the table?
  4. Fuzziekiwi
    Here's a some more pictures of placement:

    IMG_20171213_161051.jpg IMG_20171213_161100.jpg
  5. Fuzziekiwi
    I aligned them with the back of the table and it sounds MUCH better now.
  6. bigshot
    They should be parallel with your screen, not angled in.
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  7. 71 dB
    How do you know that? It depends on many things and you have to try to find out the best angle.

    I'd test to angle the speakers up (by putting something under the front part of the speakers), treble aimed to ear level. More direct sound, less reflections from the table.
  8. Fuzziekiwi
    Slightly angled because I thought monitors had to be at around 30 degrees to make an equilateral triangle. I angled them a bit with the foam. Soundstage did get wider, and the sound is cleaner. IMG_20171214_142909.jpg
  9. Strangelove424
    Generally you are correct more or less about the tweeters being aimed at the ear, at ear level. Angled them up to achieve that (or atleast one out of two) is an awkward solution though, and sure to change the HRTF tonal characteristics. Looks like he already has some sort of acoustic decoupling I think? I'm not sure what the pads are. If need be, raising the speakers to ear level on cinder blocks is a budget solution. It's a good material for decoupling, if the desk can take it.

    Ascribing a single toe angle is impossible since all speakers have different dispersion characteristics. I've heard slight toe, no toe, and extreme tow with intersecting axis behind, at, and in front of the listener. There is no single recommendation that works for every speaker.

    The main issue I see is the proximity to the back walls/window. It's bare, and bound to reflect. Stick some absorption back there on both sides of the corner, and it will null the reflections very nicely due to the angles.
    Last edited: Dec 14, 2017
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  10. Fuzziekiwi
    Isolation pads so I can angle it and brings it up to my ear level. I'm short so as I'm sitting right now the tweeters are directly at my ear level without it angled.
    Last edited: Dec 14, 2017
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  11. Strangelove424
    Nice. Not too expensive, and get's the job done. I've heard Ethan Winer talk about using pizza boxes before, so acoustic isolation doesn't need to cost an arm and a leg. As long as they are at ear level, and not causing resonance with the desk, now you just play with speaker distance, spread, and toe angle. Just keep in mind that the further you can get them from the wall, and the more you treat the wall itself, the better it will be for the sound. 1.5-2ft would be great it achievable.

    BTW, nice rig!
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  12. Fuzziekiwi
    Question; are these actually useful or different from sound absoption pads?
  13. Strangelove424
    They are good for high frequencies, but you need some sort of structural trap that extends from the wall, or is wedged in the corner for mids/bass. That can mean just building foam mounts that extend the panels a few inches from the wall, or maybe buying corner traps.

    In regards to the wall space to the sides of the listener, in front of the speakers (the back wall technically) don't use absorption there. It's suggested to put diffusion treatment in those areas to make the sound lively, but evenly dispersed without peaks and nulls. I'm not sure it will matter so much for nearfield speakers, but it's a good principle to keep in mind.

    There's a few helpful guides that can cover some basics, and give you good pointers on how to DIY.
    Last edited: Dec 14, 2017
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  14. 71 dB
    It's not necessarily awkward at all. Genelec even has "IsoPods" for that:


    Angled or not, the direct sound is coming to your ears from down, negative vertical angle so HRTF tonal characteristics are what they are. However, you get more direct sound especially at high frequencies and less reflected sound from the table.

    Raising the speakers is of course another solution.

    Exactly. One has to try it out. That's why bigshot's definitive message looked weird.
  15. Strangelove424
    You know what 71db, you are correct, I take that back (partially) because my own center speaker has no flat bottom (due to curved cabinet) and comes with rubber pads, a bit like the IsoPods that accommodate the curvature of the speaker. They allow for a slightly inclined angle, and alleviate surface reflections from whatever might be holding the central speaker. I'd say that these are workarounds for compromised issues from the start, and those especially relevant to center speakers because they often have to be placed on top of or bottom of a screen. The inability to place at ear level, horizontal dispersion, and fact that they often sit on shelves or inside of media centers, makes acoustics all the worse. But never mind that, I don't mean to go on about center speakers. The point is, yes, in certain compromised circumstances it is a good idea to tilt speakers up.
    Last edited: Dec 14, 2017
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