Room acoustics

Discussion in 'Audio Science' started by Ardacer, Jun 16, 2020.

  1. murphythecat

    murphythecat Self Imposed Exile

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    this seems wrong in many level.

    above the schroeder FR: treating the early refelction is the only way to reduce the decay times. just treating the early reflection wont make a room too dead. this is pure myth.

    under the schroeder fr: dual subs dont change the modal problems nor the decay times. bass traps, with the fronts covered with kraft paper are the only way to deal with decay times.

    yes, untreated rooms, cardioid is best. but wont magically turn your untreated room into a treated rom either. its a band-aid. your much better off goign the big bass trap way if space permits
     
  2. wbass

    wbass Facebook Friend

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    I think the ceilings are about 12 foot. I can't measure at the moment. It's a fairly raw space, appealing in some ways, but less so if I can't make it sound good. I've already considered curtains, rugs, and acoustic panels on the walls and ceilings.

    GIK suggested 40 (!) 2" spot panels to kill the reverberations. That might be a bit much for me, both financially and aesthetically. I'm also considering trying to use room dividers or partial walls (perhaps formed from bookcases) to sort of make a room within a room. Don't know if that would be effective though, given the height of the ceiling. Maybe a combo of bookshelves, curtains, and a panel cloud overhead?

    Also, ruminating on whether this might finally be the time to find a used pair of Klipschorns!

    Thanks, all, for the suggestions.
     
  3. Armaegis

    Armaegis Friend

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    The ceiling is your shortest dimension, so reflections there are something to consider if it's all one big flat area. If you're handy, you can build some simple panels yourself.

    For the room itself, just add your usual decorations and be strategic with placement to diffuse or minimize reflections. Since the space is so big, trying to kill reverb at the walls is going to be a costly battle. You'd be better off putting something closer to the speakers to scatter things before they hit the walls in the first place... but again, you can do this with decorations rather than specific panels. A few nice armchairs, an island table, yadda yadda.

    A rug is nice for absorbing the floor reflection, and also the bonus of catching all the dust bunnies at the perimeter which makes cleaning a bit easier.

    Some room dividers are a nice idea. Create your living space as well as your listening space. Too much emptiness isn't good for either.
     
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  4. wbass

    wbass Facebook Friend

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    Yeah, I think making a room within the room is probably the best strategy. Possibly with theater curtains that can be pulled across behind the listening spot. Or maybe tall bookshelves. Thanks for the suggestions.
     
  5. Armaegis

    Armaegis Friend

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    Get some carpet scraps and put them upside down under the shelves. That'll make them much easier to push around. That or casters.
     
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  6. wbass

    wbass Facebook Friend

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    Yeah, a lot of things will be on casters. Feel that I can treat the room sufficiently to kill the reverb, but still worried about even the Forte's getting a little lost in such a big space, even with a room within a room. But if the folks at GIK think it can sound great, then it probably can.
     
  7. Ardacer

    Ardacer Almost "Made"

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    Agree to disagree then, I guess. If I understood correctly, if early reflections are spectrally the same as direct radiation, ear/brain integrates them and ignores them. Which is kind of the same as eliminating them alltogether.
     
  8. murphythecat

    murphythecat Self Imposed Exile

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    I suggest you read more carefully about early reflections.

    http://arqen.com/acoustics-101/reflection-free-zone/
     
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  9. Ardacer

    Ardacer Almost "Made"

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    Apparently you are correct, with a single but.
    Dipoles eliminate early reflections by not illuminating them due to figure of 8. This is the reason why they don't sound like in the room, together with the fact that late reflections have the same spectral footprint.
    I guess it wouldn't be a bad idea to absorb them, if the room permits it.
     
  10. murphythecat

    murphythecat Self Imposed Exile

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    dipole bass doesnt effect the modal problems and doesnt reduce decay times. for best SQ with dipoles, cardioid or any other kind, put huge bass traps in as many corners as you can.

    but ime if you position your speaker and listening position ideally in the room (measure for as flat FR as possible), you can get away without bass traps if you use thick early reflection panels.
     
  11. Ardacer

    Ardacer Almost "Made"

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    I remember reading that dipole bass won't excite any modes that are not on it's axis or something like that. If positioned properly, they should excite fewest modes.
     
  12. murphythecat

    murphythecat Self Imposed Exile

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    you need huge bass traps behind the dipole, but i dont know enough about them to fully understand its acoustic advantages.
    dipole bass needs huge baffle and many big woofers though to have the impact of a conventional 15" in BR
     
  13. Ardacer

    Ardacer Almost "Made"

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    That's simply not true from my experience, either of it. It might be for some designs like you suggested, but lx521 can hit easily 98 db bass down at 30hz, and that's just a 30x40cm dipole box subs. Without traps, bass is relatively uniform in room. If you add huge traps behind, I'd say you are making a quasi cardioid out of them, which might have benefits due to placement sensitivity of the dipoles. Cardioids are easy to place.

    https://kimmosaunisto.net/CardSub/CARDSUB.html
    https://www.diyaudio.com/forums/multi-way/121590-cardioid-bass-5.html

    Don't get me wrong, I'm enjoying this discussion very much, amd thankful for your input. Not trying to be a smartass, at all.
     
  14. murphythecat

    murphythecat Self Imposed Exile

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    I admit i know very little about dipoles. the lx521 is a active speaker. dipole subs work great indeed. but i thought we were talking about passive speakers using open baffle bass.
    if you have the money for lx521, go for it. it seems to be a well thought out design albeit pricy to diy.
     
  15. Andre Y

    Andre Y Friend

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    Dipoles have fewer problems with bass modes in a room because of two reasons:

    1. they put less bass energy into the room
    2. the closeness of the equiloudness curves of the human hearing system in the bass region: in the bass region, a slight change in volume or intensity is perceived as a big change in loudness.

    So putting less bass energy into the room lowers bass modes and resonances, which have an outsized effect on what we perceive.

    Also, dipoles = open baffle bass.

    Siegfried Linkwitz explains this somewhere on his website, and it came out of an email discussion we had a long time ago.

    BTW I run a pair of version 1 Orions.
     

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