Re: need advice on improving room acoustics

Discussion in 'rec.audio.pro' started by Rick Ruskin, Aug 25, 2003.

  1. Ethan Winer

    Ethan Winer Guest

    Scott,

    Those are all good points, and I'll add just two relevant bits about reverb
    Amount versus reverb Time in large versus small rooms:

    The primary cause of absorption in a room is the walls, floor, and ceiling.
    Even with relatively hard surfaces like painted sheetrock, the walls still
    absorb much more than the air. Since it takes longer for, say, five bounces
    to travel around a large room, that is the primary reason a large room seems
    more reverberant. Not so much that there's more reverb expressed as dB below
    the original, but mainly that it lingers longer.

    Also, in small rooms those bounces happen so quickly that much of the
    reflected sound combines in the ear with the original direct sound. Anything
    that happens within 20 milliseconds or so is not heard as separate echoes or
    ambience. So the first few bounces, which are the most audible, blend with
    the original source.

    --Ethan
  2. ScotFraser

    ScotFraser Guest

    << Since it takes longer for, say, five bounces
    to travel around a large room, that is the primary reason a large room seems
    more reverberant. Not so much that there's more reverb expressed as dB below
    the original, but mainly that it lingers longer. >>

    Absolutely. I thought I was making the point that a large room can be deader
    than a small room, but maybe that wasn't stated clearly. In either case, the
    ear can easily determine the size of the room by the time displacement of the
    early reflections from the direct sound. The factors that combine to constitute
    the ambient characteristics of a space, especially a larger performance space,
    are pretty complex & I'm not sure we have verbal means to adequately describe
    it all.


    Scott Fraser
  3. Ethan Winer

    Ethan Winer Guest

    Scott,

    > the ear can easily determine the size of the room by the time displacement

    of the early reflections from the direct sound. <

    Yes, exactly.

    --Ethan
  4. Ethan,

    Undesirable indeed. Hence the absorption at the point of the first
    reflection. Not perse problematic for determining ambiance, depending
    on the definition of that word (JAES is tackling the definition
    envelopment in the latest issue, another one of those abused words; I
    do seem plug that fab mag here, maybe I should quote Asterix and
    Obelix sometime). Worse is that basic aspects like the AB gap and
    unstable image will be harder to verify. Ambiance ma be fuzzier in
    balance, but does not need to be problematic.

    The amount of action you can take to reduce the level of that first
    lateral refection in the control room does beg the question if 10 dB
    down (which is sort-a the goal here) is enough to fall within the
    definition of natural, herin referring to your 'artificial and
    unnatural' ;-) Defining that may become a tricky adventure.

    Anyway, just developing into splitting hairs here, and trying to find
    out what your lingo is. So far seems to go well, but then again,
    you're a cellist, or so I deduct ;-)

    rt60



    On Sat, 30 Aug 2003 09:28:35 -0400, "Ethan Winer" <ethan at ethanwiner
    dot com> wrote:

    >RT,
    >
    >> Diffusion at that the point of the primary reflection will widen the image

    >quite a bit. <
    >
    >Okay, but anything that artificially and unnaturally widens the image when
    >making mix decisions seems like a bad idea, no? Sort of like mixing in a
    >room with too much ambience, so you apply too little to the mix.
    >
    >> you'll find that interpreting acoustics is a journey similar to playing

    >BWV 1007 thru 1012 ;-) <
    >
    >Does this mean there's another cellist in the group?
    >
    >--Ethan
    >
  5. Ethan Winer

    Ethan Winer Guest

    RT,

    > Undesirable indeed. Hence the absorption at the point of the first

    reflection. <

    Perhaps I misunderstood because originally you said, "Diffusion at the point
    of the primary reflection will widen the image quite a bit." So I thought
    you were proposing that.

    > does beg the question if 10 dB down (which is sort-a the goal here) is

    enough <

    How much an absorbing panel attenuates is less relevant than how low in
    frequency it works to. Even half an inch of 703 rigid fiberglass absorbs
    100% at the upper mids and above. As the material is made thicker and denser
    it's absorption extends lower. I recently added absorption on the side walls
    and ceiling of my control room to make an RFZ, and I used 2-inch thick
    705-FRK to make the zone effective down to low frequencies.

    > trying to find out what your lingo is. So far seems to go well, but then

    again, you're a cellist, or so I deduct ;-) <

    Ha, my "lingo" is all over the map as I have MANY interests - music theory,
    skepticism, acoustics, electronic circuits, consumerism, guitar and cello
    playing, audio and recording, computer programming. It's all on my web site
    www.ethanwiner.com.

    --Ethan
  6. Ethan,

    I had seen your website, in fact, referred some-one to in in this
    thread. I was kidding around a bit. Anyway, we seem to be running in
    parallels... I like the skepticism part quite a bit.

    The 2" will get you to about -10dB btw; that is about what we do. I'll
    look up some measurements for that, if you like.

    RU attending the AES convention by any chance?


    rt60

    off to the etude nicknamed humbadada...



    On Tue, 2 Sep 2003 08:53:49 -0400, "Ethan Winer" <ethan at ethanwiner
    dot com> wrote:

    >RT,
    >
    >> Undesirable indeed. Hence the absorption at the point of the first

    >reflection. <
    >
    >Perhaps I misunderstood because originally you said, "Diffusion at the point
    >of the primary reflection will widen the image quite a bit." So I thought
    >you were proposing that.
    >
    >> does beg the question if 10 dB down (which is sort-a the goal here) is

    >enough <
    >
    >How much an absorbing panel attenuates is less relevant than how low in
    >frequency it works to. Even half an inch of 703 rigid fiberglass absorbs
    >100% at the upper mids and above. As the material is made thicker and denser
    >it's absorption extends lower. I recently added absorption on the side walls
    >and ceiling of my control room to make an RFZ, and I used 2-inch thick
    >705-FRK to make the zone effective down to low frequencies.
    >
    >> trying to find out what your lingo is. So far seems to go well, but then

    >again, you're a cellist, or so I deduct ;-) <
    >
    >Ha, my "lingo" is all over the map as I have MANY interests - music theory,
    >skepticism, acoustics, electronic circuits, consumerism, guitar and cello
    >playing, audio and recording, computer programming. It's all on my web site
    >www.ethanwiner.com.
    >
    >--Ethan
    >

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