Re: need advice on improving room acoustics

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

  1. Rick Ruskin

    Rick Ruskin Guest

    On 25 Aug 2003 09:47:59 -0700, jnorman34@comcast.net (jnorman) wrote:

    >my studio is about 17'x23'x8' with carpet floor, sheetrock walls and
    >ceiling. no drapes or other acoustic damping materials. baby grand
    >piano, chairs, music cabinets, etc. i do a variety of mostly
    >classical acoustic instrument recording, solos, duos, small ensembles,
    >like flute and piano, violin and harp, oboes, etc. my gear is pretty
    >good now, and i can tell that my room holds my sound back more than
    >anything else at this point. but i dont know if i should make the
    >room deader, like a big isolation area, or if i should make the room
    >more live for a more natural ambience. should i add drapes, etc, or
    >should i replace the carpet with a wood floor? or will this room
    >alwasy be crappy just because it has an 8' ceiling? thanks for your
    >comments.



    With a ceiling that low, I think you will need less reflection rather
    than more. I'd suggest dampening some sections of the room to break
    up some of the early reflections. With luck you might be able to rid
    yourself of enough to make the room more pleasant sounding. You might
    also find it necessary to kill all ambience and create it
    electronically. You never know untill you try a few things. If you
    can determine which wall(s) cause the most sonic grief, work on the
    creases where walls and ceiling meet. This probably won't cure
    everything but it usually goes a long way. I used R-19 encased in
    cut-to- fit canvas for my room. It made a big difference. (Make sure
    to do all fiberglass work outside so that you don't contaminate your
    gear or room. Good idea to where a particle mask, too.)




    Rick Ruskin
    Lion Dog Music - Seattle WA
    http://liondogmusic.com
  2. Raymond

    Raymond Guest

    >On 25 Aug 2003 09:47:59 -0700, jnorman34@comcast.net (jnorman) wrote:
    >
    >>my studio is about 17'x23'x8' with carpet floor, sheetrock walls and
    >>ceiling. no drapes or other acoustic damping materials. baby grand
    >>piano, chairs, music cabinets, etc. i do a variety of mostly
    >>classical acoustic instrument recording, solos, duos, small ensembles,
    >>like flute and piano, violin and harp, oboes, etc. my gear is pretty
    >>good now, and i can tell that my room holds my sound back more than
    >>anything else at this point. but i dont know if i should make the
    >>room deader, like a big isolation area, or if i should make the room
    >>more live for a more natural ambience. should i add drapes, etc, or
    >>should i replace the carpet with a wood floor? or will this room
    >>alwasy be crappy just because it has an 8' ceiling? thanks for your
    >>comments.


    Try using a good spectrum analyzer and a good (flat) mic and throwing some
    sweep tones and also some pink noise into your room. The flatter the better (in
    most cases) but on the other hand, a good live room is cool for acoustic stuff.
  3. jnorman34@comcast.net (jnorman) wrote in message news:<e340b423.0308250847.3408ff32@posting.google.com>...
    > my studio is about 17'x23'x8' with carpet floor, sheetrock walls and
    > ceiling. no drapes or other acoustic damping materials. baby grand
    > piano, chairs, music cabinets, etc. i do a variety of mostly
    > classical acoustic instrument recording, solos, duos, small ensembles,
    > like flute and piano, violin and harp, oboes, etc. my gear is pretty
    > good now, and i can tell that my room holds my sound back more than
    > anything else at this point. but i dont know if i should make the
    > room deader, like a big isolation area, or if i should make the room
    > more live for a more natural ambience. should i add drapes, etc, or
    > should i replace the carpet with a wood floor? or will this room
    > alwasy be crappy just because it has an 8' ceiling? thanks for your
    > comments.



    Add *diffusors* instead of damping material... check out RPG and
    Auralex' stuff. Your risk is that if you damp with curtains you won't
    really take care of lo-freq resonance, which should be dealt with by
    means of Helmholtz resonators and bass traps, such as TubeTraps. Check
    out ethanwiner.com for examples of home made bass traps; Ethan also
    records / playas classical music (cello, I believe).
    Oh yeah.... Check out F. Alton Everest's "Handbook of Acoustics" for
    more info.
    Acoustics are a very complex argument and should be dealt with care.
    G'luck!

    Paul Weber
  4. Ethan Winer

    Ethan Winer Guest

    JN,

    > my studio is about 17'x23'x8' <


    That's not a great ratio, but it's large enough to get good results by
    adding proper acoustic treatment.

    > with carpet floor, sheetrock walls and ceiling. no drapes or other

    acoustic damping materials. <

    For the type of acoustic music you're recording you should reverse the floor
    and ceiling. Remove the carpet to have a reflective floor, then make the
    ceiling partly or fully absorbent with rigid fiberglass. A hard floor
    doesn't have to be expensive wood. Lineloum or even bare painted cement
    sound equally good.

    > i dont know if i should make the room deader ... or if i should make the

    room more live for a more natural ambience. <

    Your room is large enough to take advantage of ambience. Ideally you want
    some ambience, but controlled by selective placement of absorbing materials.
    That is, you don't want all the surfaces bare OR all covered with drapes or
    other absorbers. Applying absorption in a vertical striped pattern is good,
    as is a 2x2 or 2x4 foot checkerboard pattern. For a room that size you want
    somewhere between 20 and 40 percent of the surfaces covered with absorbing
    material - maybe a little more if you include the ceiling in that figure.
    Note that all rooms need absorption at low frequencies as well as at mid and
    high frequencies. This requires material much more substantial than just
    drapes or thin foam.

    > or will this room always be crappy just because it has an 8' ceiling? <


    Not at all, and that's the main reason to deaden the ceiling. A ceiling that
    is 100 percent absorptive is identical acoustically to a ceiling that's
    infinitely high. That is, it doesn't matter if sound is not reflected down
    from the ceiling because it absorbs or because it's very far away.

    I suggest you see my Acoustics FAQ which explains room treatment in great
    detail. It's 10th in the list on my Articles page:

    www.ethanwiner.com/articles.html

    --Ethan
  5. Scott Dorsey

    Scott Dorsey Guest

    Raymond <bruwhaha58097238@aol.com> wrote:
    >>On 25 Aug 2003 09:47:59 -0700, jnorman34@comcast.net (jnorman) wrote:
    >>
    >>>my studio is about 17'x23'x8' with carpet floor, sheetrock walls and
    >>>ceiling. no drapes or other acoustic damping materials. baby grand
    >>>piano, chairs, music cabinets, etc. i do a variety of mostly
    >>>classical acoustic instrument recording, solos, duos, small ensembles,
    >>>like flute and piano, violin and harp, oboes, etc. my gear is pretty
    >>>good now, and i can tell that my room holds my sound back more than
    >>>anything else at this point. but i dont know if i should make the
    >>>room deader, like a big isolation area, or if i should make the room
    >>>more live for a more natural ambience. should i add drapes, etc, or
    >>>should i replace the carpet with a wood floor? or will this room
    >>>alwasy be crappy just because it has an 8' ceiling? thanks for your
    >>>comments.

    >
    >Try using a good spectrum analyzer and a good (flat) mic and throwing some
    >sweep tones and also some pink noise into your room. The flatter the better (in
    >most cases) but on the other hand, a good live room is cool for acoustic stuff.


    More live doesn't mean it has to be less flat.
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  6. Ethan Winer

    Ethan Winer Guest

    Raymond,

    > would more live = less dead? And does alot of damping not make things

    live? <

    Live and dead are opposite. An empty bedroom in a new house is very live. A
    closet filled with clothes - damping material - is very dead. Good recording
    and control room are somewhere between those extremes. See my Acoustics FAQ
    referenced above for much more detail.

    --Ethan
  7. Scott Dorsey

    Scott Dorsey Guest

    Raymond <bruwhaha58097238@aol.com> wrote:
    >Scott wrote
    >>More live doesn't mean it has to be less flat.

    >
    >I'm not for sure but would more live = less dead? And does alot of damping not
    >make things live?


    More live means a longer reverb time. More dead means a shorter reverb
    time. (Given the same room volume, of course.)

    You can have a room without severe frequency response aberrations that is
    live, or one that is dead.

    You can have a room with bigtime standing waves in the low end, and you
    can have one with bigtime peaks and dips in the top end, that is live.
    Or one that is dead.

    A lot of damping will make things dead, but most damping is frequency
    selective. You throw a lot of thin foam into a room and now your high
    frequencies are damped, but the low end is unchanged. You put a bass trap
    in, and your low frequencies are damped, but the high end is unchanged.

    You can also use diffusion to change the frequency response of the room
    without changing the overall reverb time much. Bookcases can be a very
    handy tool for this.
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  8. Raymond

    Raymond Guest

    scott wrote
    >More live means a longer reverb time. More dead means a shorter >reverb time.

    (Given the same room volume, of course.)

    Larger room + longer Reverb time?
  9. ScotFraser

    ScotFraser Guest

    << I'm not for sure but would more live = less dead? >>

    Yes, more live means more reflective, more reverberant, less absorptive.

    <<And does alot of damping not
    make things live?
    >>


    A lot of damping does not make things live. Damping is absorption.



    Scott Fraser
  10. Scott Dorsey

    Scott Dorsey Guest

    Raymond <bruwhaha58097238@aol.com> wrote:
    >scott wrote
    >>More live means a longer reverb time. More dead means a shorter >reverb time.

    > (Given the same room volume, of course.)
    >
    >Larger room + longer Reverb time?


    That's also true. In a small room, most of the reflections you get are
    going to be short reflections from nearby surfaces. If it's a very live
    room, the reverb time can still be fairly long.

    In a large room, the reverb time will be longer, because most of the
    reflections are coming from distant surfaces.

    Whether high or low frequency reflections predominate is a seperate issue.

    In general, short reflections from nearby objects dominate so much in a
    small room that reverb time becomes a useless measurement. But we can still
    talk about "perceived liveness."
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  11. be careful with diffusors. They seem to make a dead room more life but
    that is mostly a high frequency issue. and with those vertical
    diffurors you get some nasty high frequency tones/hiss in the
    reflection back in the direction of the source, especially at shallow
    angles of incidence.

    in my humble opinion we should not be running to the RPG's of this
    world and spend hundreds of dollars in... adding nasty sound. yes, if
    you ahve a back-slap echo a schroeder diffusor may help, but if the
    area that has a shallow angle of incidence to these surfaces is
    important (because audience, mics or musicians sit there) try other
    solutions.

    in this small room, I'd start with base absorber of the panel type.
    see ethan's site for great links and examples. The surface of these do
    not necessarily have to be absorbtive, they could be simply 1/4"
    plywood. if that is too much, glue a small layer of felt on them
    (1/16" construction felt can don wonders). If you'd panel one of the
    walls (preferably the heaviest one), size them so that wall is no
    longer in parallel with the opposite wall, that way you can also
    'trap' some flutter conditions that might exist. then dampen (read:
    felt/fiberglass) the wall towards which the reflections are directed.

    just a few thoughts...

    rt60


    On 26 Aug 2003 03:38:51 -0700, paul@jjm.ch (Paul C. Weber) wrote:

    >jnorman34@comcast.net (jnorman) wrote in message news:<e340b423.0308250847.3408ff32@posting.google.com>...
    >> my studio is about 17'x23'x8' with carpet floor, sheetrock walls and
    >> ceiling. no drapes or other acoustic damping materials. baby grand
    >> piano, chairs, music cabinets, etc. i do a variety of mostly
    >> classical acoustic instrument recording, solos, duos, small ensembles,
    >> like flute and piano, violin and harp, oboes, etc. my gear is pretty
    >> good now, and i can tell that my room holds my sound back more than
    >> anything else at this point. but i dont know if i should make the
    >> room deader, like a big isolation area, or if i should make the room
    >> more live for a more natural ambience. should i add drapes, etc, or
    >> should i replace the carpet with a wood floor? or will this room
    >> alwasy be crappy just because it has an 8' ceiling? thanks for your
    >> comments.

    >
    >
    >Add *diffusors* instead of damping material... check out RPG and
    >Auralex' stuff. Your risk is that if you damp with curtains you won't
    >really take care of lo-freq resonance, which should be dealt with by
    >means of Helmholtz resonators and bass traps, such as TubeTraps. Check
    >out ethanwiner.com for examples of home made bass traps; Ethan also
    >records / playas classical music (cello, I believe).
    >Oh yeah.... Check out F. Alton Everest's "Handbook of Acoustics" for
    >more info.
    >Acoustics are a very complex argument and should be dealt with care.
    >G'luck!
    >
    >Paul Weber
  12. Raymond

    Raymond Guest

    Raymond <bruwhaha58097238@aol.com> wrote
    >Larger room + longer Reverb time?


    Opps that should have been = not +

    Scott wrote
    >That's also true. In a small room, most of the reflections you get are
    >going to be short reflections from nearby surfaces. If it's a very live
    >room, the reverb time can still be fairly long.


    Being a small room = many bouncing reflections? (depending on room
    construction) If its a small room the reflections (some frequencies) can be
    sharp or hard to control no matter what you do to the walls?

    >In a large room, the reverb time will be longer, because most of the
    >reflections are coming from distant surfaces.


    Yes, frequency is time/distance or size right?

    >Whether high or low frequency reflections predominate is a seperate >issue.


    So if your planning on using the room for a live guitar (small set range of
    frequencies) will be different than if you want to use it for a full set of
    drums (larger set of frequencies) etc.?


    >In general, short reflections from nearby objects dominate so much in a
    >small room that reverb time becomes a useless measurement. But we can still
    >talk about "perceived liveness."


    Your talking about pre/early-decay (I think) right? So a room (hopefully a
    large one) with no points of obstruction will give a larger revearb time yes?

    Forgive my ?'s but It maybe worth discussing.
  13. Scott Dorsey

    Scott Dorsey Guest

    Raymond <bruwhaha58097238@aol.com> wrote:
    >Raymond <bruwhaha58097238@aol.com> wrote
    >>Larger room + longer Reverb time?

    >
    >Opps that should have been = not +
    >
    >Scott wrote
    >>That's also true. In a small room, most of the reflections you get are
    >>going to be short reflections from nearby surfaces. If it's a very live
    >>room, the reverb time can still be fairly long.

    >
    >Being a small room = many bouncing reflections? (depending on room
    >construction) If its a small room the reflections (some frequencies) can be
    >sharp or hard to control no matter what you do to the walls?


    If it's a live small room, there will be many bouncing reflections. If
    it is a dead small room, there won't be. In all cases, the reflections
    that predominate will be ones that come a short time after the original
    peak, rather than longer term ones. This is why small rooms can sound boxy
    if they are very live.

    >>In a large room, the reverb time will be longer, because most of the
    >>reflections are coming from distant surfaces.

    >
    >Yes, frequency is time/distance or size right?


    The only time you want to think about frequency in terms of distance is
    when you're worrying about standing waves. In this case, the reflections
    that come back can be any frequency at all... the reflectivity of the
    surfaces in the room can have high end or low end dominating, it doesn't
    matter to the fact that it's a live room.

    >>Whether high or low frequency reflections predominate is a seperate >issue.

    >
    >So if your planning on using the room for a live guitar (small set range of
    >frequencies) will be different than if you want to use it for a full set of
    >drums (larger set of frequencies) etc.?


    Not really, you still want a room with a generally flat frequency response
    and a fairly long and even reverb. The length of the reverb decay that
    you want for a drum kit will probably be longer than you want for guitar,
    but it's easy to shorten it or deaden it with gobos.

    >>In general, short reflections from nearby objects dominate so much in a
    >>small room that reverb time becomes a useless measurement. But we can still
    >>talk about "perceived liveness."

    >
    >Your talking about pre/early-decay (I think) right? So a room (hopefully a
    >large one) with no points of obstruction will give a larger revearb time yes?


    Not necessarily. But if there are no points of obstruction, there will be
    more of a chance that you'll get discrete echoes from the surfaces rather
    than a nice even decay. And that's bad too.

    >Forgive my ?'s but It maybe worth discussing.


    The F. Alton Everest introduction to small studio acoustics is well worth
    checking out.
    --scott
    --
    "C'est un Nagra. C'est suisse, et tres, tres precis."
  14. Ethan Winer

    Ethan Winer Guest

    RT,

    > with those vertical diffusors <


    One thing many people don't realize is diffusion is not useful in small
    rooms. According to Dr. Antonio's FAQ at the RPG site, the distance between
    your ears and a diffuser should be at least ten feet. Less distance than
    that and adding diffusion actually harms the sound. This also holds for
    diffusion on the ceiling. Unless your ceiling is 15 or more feet high,
    putting a diffuser there is a mistake.

    --Ethan
  15. Raymond

    Raymond Guest

  16. Hello Ethan,

    devils advocate: sure doesn't work in a very small room to have flat
    surfaces all around. most diffusion is of course in practice cause by
    furniture and the different materials used for floors, walls and
    ceilings.

    with regard to RPG's science, I tend to take their interpretation of
    their own research with a grain of salt. I have seen and heard spaces
    with their material and applied with their endorsement that makes me
    doubt their science. gives me the same feeling sometimes as when I
    read about dr. bose. their attitude is to design a room and then buy
    the acoustics via mail-order, next-day delivery; it just doesn't work
    that way.

    when I mention diffusion I do not necessarily refer to expensive
    panels from a factory. I refer to a means to diffract some of the
    sound. the diffusion should be scaled to the need (1/4 wavelength
    idea, plus the broadening of the bandwidth by use of varying
    materials).

    skylines are possbily one of the better panels for smaller rooms as
    far as the factory panels is concerned, because it is a combination of
    mid frequency absorption and some decent high frequency diffusion. can
    take care of some harshness that is just short of identified flutter.

    with the vertical diffusors (schroeder type) angle of incidence is the
    most important issue. if that is close to straight-on for source and
    destination, the side effects can be acceptable... just don't use too
    much of it, it hurts when you play flageolets on the A string ;-)

    rt60


    On Thu, 28 Aug 2003 10:34:30 -0400, "Ethan Winer" <ethan at ethanwiner
    dot com> wrote:

    >RT,
    >
    >> with those vertical diffusors <

    >
    >One thing many people don't realize is diffusion is not useful in small
    >rooms. According to Dr. Antonio's FAQ at the RPG site, the distance between
    >your ears and a diffuser should be at least ten feet. Less distance than
    >that and adding diffusion actually harms the sound. This also holds for
    >diffusion on the ceiling. Unless your ceiling is 15 or more feet high,
    >putting a diffuser there is a mistake.
    >
    >--Ethan
    >
  17. Ethan Winer

    Ethan Winer Guest

    RT,

    > most diffusion is of course in practice cause by furniture <


    Good point.

    > when I read about dr. bose <


    Nuff said. :->)

    Dr. Bose may well be a genius - I have no idea - but all the products of his
    I've heard are pretty awful.

    Anyway, thanks for the clarification. I'm still getting up to speed on
    diffusion. As I understand it, the main problem with installing diffusers on
    nearby surfaces is you still have "early reflections," and broadly diffusing
    them just confuses the imaging even more. The studio designers I've
    discussed this with all told me they recommend broadband absorption on any
    nearby surface that could yield a primary reflection, which makes sense to
    me. But conflicting opinions are always welcome!

    --Ethan
  18. ScotFraser

    ScotFraser Guest

    << Being a small room = many bouncing reflections? (depending on room
    construction) >>

    Not necessarily. You can have a very dead small room, as well as a large room
    with a lot of direct reflections. Large rooms tend to diffuse into reverb,
    though.

    <<If its a small room the reflections (some frequencies) can be
    sharp or hard to control no matter what you do to the walls?>>

    Not necessarily. You can make an anechoic small room. What you can't do is fool
    the ear into believing the room is larger, because the early reflections are
    easily discernible as coming from a short distance away.

    << So a room (hopefully a
    large one) with no points of obstruction will give a larger revearb time yes?>>

    Reverb decay time is often longer is larger rooms, but it's very easy to make
    rooms where the opposite is true. It's all in the ratio of absorption to
    reflection of the surfaces. All things being equal (which they never are, but
    let's say they are for example) a large room that is an identical version of a
    small room, just multiplied in every dimension, will be more reverberant than
    the identical small room, & will be easily perceivable as larger due to the
    longer path for first reflections, greater degree of diffusion & greater
    absorption of highs in the contained air.

    Scott Fraser
  19. Ethan,

    Au contrare, I absolutely agree that it is good to reduce the level of
    the first reflections. But now we're talking about a control room, and
    not a recording space, I suppose.

    Diffusion at that the point of the primary reflection will widen the
    image quite a bit. I would be inclined to put diffusion on the side
    walls behind the listening position for stereo listening, and scatter
    the back wall in bigger blocks. The complication is that this is the
    area where the first wall-reflection for the surround loudspeaker is
    traced. When we start to get into that, there are multiple paths and
    ideas to follow, and we'd have to get to real-life situations before
    determining what would be the better approach, as part of this is the
    location and angle of the surround loudspeaker and its radiation
    pattern. Then add-in the issues involving the HRTF (see latest JAES
    for some new research on that) and the use of 'side-panned' source
    locations, and you'll find that interpreting acoustics is a journey
    similar to playing BWV 1007 thru 1012 ;-)

    rt60



    On Fri, 29 Aug 2003 11:28:49 -0400, "Ethan Winer" <ethan at ethanwiner
    dot com> wrote:

    >RT,
    >
    >> most diffusion is of course in practice cause by furniture <

    >
    >Good point.
    >
    >> when I read about dr. bose <

    >
    >Nuff said. :->)
    >
    >Dr. Bose may well be a genius - I have no idea - but all the products of his
    >I've heard are pretty awful.
    >
    >Anyway, thanks for the clarification. I'm still getting up to speed on
    >diffusion. As I understand it, the main problem with installing diffusers on
    >nearby surfaces is you still have "early reflections," and broadly diffusing
    >them just confuses the imaging even more. The studio designers I've
    >discussed this with all told me they recommend broadband absorption on any
    >nearby surface that could yield a primary reflection, which makes sense to
    >me. But conflicting opinions are always welcome!
    >
    >--Ethan
    >
  20. Ethan Winer

    Ethan Winer Guest

    RT,

    > But now we're talking about a control room, and not a recording space, I

    suppose. <

    Yeah, we needs to distinguish live room, control room, and now even surround
    listening rooms!

    > 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

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