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speaker box assignment

Discussion in 'Electronic Repair' started by [email protected], Nov 1, 2005.

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  1. Guest

    I'm studying industrial design at Wentworth Institute of Technology
    in Boston. I have been given the following assignment: to design a
    speaker enclosure to house a 4" woofer and a 2" diameter tweeter.
    The tweeter is an Onkyo 3/8" (269-708) standard one-way driver.
    The driver parameters are as follows:
    Fs=4200 Hz
    P-diameter = 0.375"
    Sd=0.713sq.cm
    Re=3.5 Ohms
    Le-= 0.013Mh
    Z=4 Ohms
    Pe=20 watts
    no=0.306%
    1-W SPL=87dB
    2.83-V SPL=90.59dB.

    Woofer properties:
    Goldwood, GS204/4S (290-370) standard one-way driver.
    Driver parameters:
    Fs = 138 Hz
    Qms = 7.19
    Vas= 0.991 Liters

    Cms= 0.336 mm/N
    Mms= 3.964 g
    Rms= 0.478 kg/s
    Xmax= 1.5mm
    Xmech= 2.25mm
    P-dia= 3in
    Sd= 45.6 sq.cm
    P-Vd= 0.00684 Liters
    Qes= 2.2
    Re= 3.333 Ohms
    Le= 0.184 mH
    Z= 4 ohms
    BL= 2.282 N/A
    Pe= 40 watts
    Qts= 1.69
    No= 0.114%
    1-W SPL = 82.72 dB
    2.83-V Spl = 86 dB

    Box parameters:
    Type" Closed Box
    Vb= 4.248 Liters
    QL=20
    Fill = Heavy

    My assignment is to design two bookshelf / desktop speakers that not
    only produce quality sound but are visually appealing. Our professor
    suggests we use ½" or ¾" MDF fiber board because it is dense and
    good for sound applications. We are allowed to explore other materials
    if we desire. This assignment is pretty open as far as materials and
    box design. I'm not asking for someone to do all the work for me
    with this assignment but rather provide me with some tips or possible
    places I can find some information about speaker boxes. Anything you
    can provide me would be most appreciated. Thanks!

    Jesse Stein

    If this is not the correct newsgroup to post this to if someone could
    direct me to a more appropriate group I would really appreciate it.
     
  2. Fx

    Fx Guest

    http://home.earthlink.net/~etunstal/diy.htm






    I'm studying industrial design at Wentworth Institute of Technology
    in Boston. I have been given the following assignment: to design a
    speaker enclosure to house a 4" woofer and a 2" diameter tweeter.
    The tweeter is an Onkyo 3/8" (269-708) standard one-way driver.
    The driver parameters are as follows:
    Fs=4200 Hz
    P-diameter = 0.375"
    Sd=0.713sq.cm
    Re=3.5 Ohms
    Le-= 0.013Mh
    Z=4 Ohms
    Pe=20 watts
    no=0.306%
    1-W SPL=87dB
    2.83-V SPL=90.59dB.

    Woofer properties:
    Goldwood, GS204/4S (290-370) standard one-way driver.
    Driver parameters:
    Fs = 138 Hz
    Qms = 7.19
    Vas= 0.991 Liters

    Cms= 0.336 mm/N
    Mms= 3.964 g
    Rms= 0.478 kg/s
    Xmax= 1.5mm
    Xmech= 2.25mm
    P-dia= 3in
    Sd= 45.6 sq.cm
    P-Vd= 0.00684 Liters
    Qes= 2.2
    Re= 3.333 Ohms
    Le= 0.184 mH
    Z= 4 ohms
    BL= 2.282 N/A
    Pe= 40 watts
    Qts= 1.69
    No= 0.114%
    1-W SPL = 82.72 dB
    2.83-V Spl = 86 dB

    Box parameters:
    Type" Closed Box
    Vb= 4.248 Liters
    QL=20
    Fill = Heavy

    My assignment is to design two bookshelf / desktop speakers that not
    only produce quality sound but are visually appealing. Our professor
    suggests we use ½" or ¾" MDF fiber board because it is dense and
    good for sound applications. We are allowed to explore other materials
    if we desire. This assignment is pretty open as far as materials and
    box design. I'm not asking for someone to do all the work for me
    with this assignment but rather provide me with some tips or possible
    places I can find some information about speaker boxes. Anything you
    can provide me would be most appreciated. Thanks!

    Jesse Stein

    If this is not the correct newsgroup to post this to if someone could
    direct me to a more appropriate group I would really appreciate it.
     
  3. none

    none Guest

    Try the following links.

    http://www.speakermania.com/
    http://www.madisound.com/cgi-bin/discuss.cgi?
    http://www.diysubwoofers.org/talkshop/
    http://f16.parsimony.net/forum27133/index.htm
    http://www.pesupport.com/cgi-bin/config.pl
    http://www.spiceisle.com/audiodiy/
    http://www.diyaudio.com/
    http://www.speakerbuilding.com/
    http://www.us-epanorama.net/audiospeakers.html
    http://www.hi-fi.com/speaker/
    http://www.sound.au.com/tsp.htm
    http://www.geocities.com/SiliconValley/Park/1187/speakernet.html
    http://www.melhuish.org/audio/links.htm
    http://www.scrounge.org/speak/speak.htm
    http://www.globalnode.com/users/stevenr/xover3.htm
    http://www.audioasylum.com/audio/speakers/bbs.html
    http://members.tripod.com/XSSpl/Audio/Sound.htm
    http://www.speakerworks.net/
    http://www.madisound.com/
    http://www.speakercity.com/
    http://www.epanorama.net/measuring.html
    http://www.epanorama.net/measuring.html#audio
    http://www.trueaudio.com/linksp1.htm
    http://www.audioholics.com/Message_Forums.htm
    http://www.i-depth.com:80/P/k/kj05019.frm.speakmess.html
    http://www.AudioAsylum.com/audio/speakers/bbs.html


    Some of these links are old but their should be something there
    that'll get you started.

    I've used a program called win ISD to calculate box volumes and dimns
    that is fairly accurate and is free to be had at their site.

    www.linearteam.org/winisd.html

    There are better programs but this one gets the job done.

    If your going with a woofer as small as 4 inchs 1/2 inch mdf will do
    though I always use 3/4 or thicker for my projects.
    The key thing for getting good sound out of such a small driver is to
    be sure to limit the low pass frequencies to keep response tight.( I
    wouldn't try and drive anything below 40hz into it, it would most
    likely cause distortion and will certainly rob it of most of it's
    efficiency.)
    Keep the design simple, go with a sealed box, you really won't see
    much benefit from porting with such a small driver.( You might
    consider a dual woofer setup wired out of phase if you can get two
    more of those Goldwood's.(It's called an isobarik or push/pull design
    and works wonders when used with smaller drivers. Most designs use a
    simple tube configuration which can be designed for an esthetically
    pleasing appearance.)


    Here are a couple of up-to-date links for software.

    http://melhuish.org/audio/software.html

    http://www.audiogrid.com/audio/
     
  4. GregS

    GregS Guest

    The so called woofer is a bit strange. It high resonance is higher than typical full
    range drivers, and it sensitivity is very low. Both strange. Your going to be using
    a high crossover frequency, so stuffing requirments are not only for bass response,
    but also high frequency attenuation. I would use foam and or fiberglass since
    they have the best attenuation.

    greg
     
  5. JW

    JW Guest

    I'd always figured that granite enclosures would rule audio-wise - they'd
    look nice too. All other things being equal, I suspect that the higher the
    density of the enclosure material, the better the sound quality.
     
  6. jakdedert

    jakdedert Guest

    I just salvaged almost 3000 solid bricks from a house scheduled for
    demolition. I wonder what kind of enclosure 'those' would make.....?

    jak
     
  7. Mebbe but it's not so much the density as the damping. Some of the
    best enclosures were made of Aerolam damped with bituminous felt.
    Many modern enclosures are made of synthetic laminates with internal
    damping layers.

    One might check the archives of speaker reviews at www.stereophile.com
    (shameless plug) to see the bench tests of speaker enclosure
    resonances. Fewer and shorter is better.

    Kal
     
  8. JW

    JW Guest

    Correct me if I'm wrong, but wouldn't a higher density material cause the
    damping to improve? (Lead speakers anyone?)
     
  9. Lead is dense and soft, both of which contribute to its damping
    properties. The problem with simply saying that a dense material is
    sufficient is that it leaves out the thickness. A dense but thin wall
    is harder to damp than a light but thin wall. Same for thick walls.
    It really depends on the sizes of the walls and where you want to move
    the resonances.

    As a general rule, you can get away with dense, thick, braced panels
    but that might not be practical (or moveable).

    Kal
     
  10. Mike W.

    Mike W. Guest

    4+ liters sounds big for a 4" woofer to me. Particle board or plywood (high
    grade, very fer voids) are good choices.
     
  11. or depleted uranium : )
     
  12. JW

    JW Guest

    Two birds with one stone! Who could ask for anything more?
     
  13. none

    none Guest

    I'm not sure exactly what you mean by dampening but will have a go at
    explaining why dampening materials are of benefit in box building.
    In regards to dampening in box material itself( mdf, plywood, concrete
    etc...) Yes the more rigid and dense the material the better as it
    acts to reflect the back waves better resulting is less energy loss
    and of course lower resonance which only adds coloration/noise.
    In box stuffing the idea is to add a material such as polyfill which
    acts as an "acoustic maze" or baffle which has the effect of
    increasing box volume. There are special materials such as
    acoustastuff which has the optimum characteristics, they can be had at
    parts express or any good speaker parts dealer.
    In the old days we used a material called kimsul, a kind of wool-like
    material which has been rendered obsolete by better materials

    As for box materials, I've seen them made with just about every kind
    of high density material.
    I've always favored acoustic plywood.( 10 ply birch or white oak,
    usually 1-1/4 inch thick. It has the advantage of being a bit denser
    than regular plywood as it's pressed under greater pressure and with a
    glue that has stronger adhesion qualities than the water based stuff
    used in ordinary ply.)
    The best box I've seen in regards to it's dampening properties was
    formed out of concrete. Hard to build, heavy as hell and not too
    attactive in the home setting though.
    Years back a friend of mine had me help him wire up an isobarik that
    he'd made using 8 inch concrete drain pipe. About 4 feet tall as I
    recall using two woofers wired out of phase for push/pull effect.
    The bass was fairly clean and it had decent efficiency specs but were
    they heavy! Not too pretty either.(though he did improve their looks
    with some concrete paint and a bit of gloss laquer.)

    I've had occasion to use the mdf especially designed for audio
    boxes.(can be gotten at most automotive sound shops)
    It's of a finer construct material and is sealed on the outer surfaces
    rather than the more coarse, open grain stuff you get at home building
    supply stores. It's also thicker( 7/8 for what we used) and is easier
    to apply paints or finishing coats to.

    I talked to a fellow online that was attempting to use wonderboard to
    build a set of boxes, though I never heard how it worked out.
     
  14. Asimov

    Asimov Guest

    "none" bravely wrote to "All" (05 Nov 05 04:49:02)
    --- on the heady topic of "Re: speaker box assignment"

    no> From: none <>
    no> Xref: core-easynews sci.electronics.repair:347606

    no> On Thu, 3 Nov 2005 01:58:39 -0500, "Michael Kennedy"
    no> I'm not sure exactly what you mean by dampening but will have a go at
    no> explaining why dampening materials are of benefit in box building.
    no> In regards to dampening in box material itself( mdf, plywood, concrete
    no> etc...) Yes the more rigid and dense the material the better as it
    no> acts to reflect the back waves better resulting is less energy loss
    no> and of course lower resonance which only adds coloration/noise.
    no> In box stuffing the idea is to add a material such as polyfill which
    no> acts as an "acoustic maze" or baffle which has the effect of
    no> increasing box volume. There are special materials such as
    no> acoustastuff which has the optimum characteristics, they can be had at
    no> parts express or any good speaker parts dealer.
    no> In the old days we used a material called kimsul, a kind of wool-like
    no> material which has been rendered obsolete by better materials

    no> As for box materials, I've seen them made with just about every kind
    no> of high density material.
    no> I've always favored acoustic plywood.( 10 ply birch or white oak,
    no> usually 1-1/4 inch thick. It has the advantage of being a bit denser
    no> than regular plywood as it's pressed under greater pressure and with a
    no> glue that has stronger adhesion qualities than the water based stuff
    no> used in ordinary ply.)
    no> The best box I've seen in regards to it's dampening properties was
    no> formed out of concrete. Hard to build, heavy as hell and not too
    no> attactive in the home setting though.
    no> Years back a friend of mine had me help him wire up an isobarik that
    no> he'd made using 8 inch concrete drain pipe. About 4 feet tall as I
    no> recall using two woofers wired out of phase for push/pull effect.
    no> The bass was fairly clean and it had decent efficiency specs but were
    no> they heavy! Not too pretty either.(though he did improve their looks
    no> with some concrete paint and a bit of gloss laquer.)

    no> I've had occasion to use the mdf especially designed for audio
    no> boxes.(can be gotten at most automotive sound shops)
    no> It's of a finer construct material and is sealed on the outer surfaces
    no> rather than the more coarse, open grain stuff you get at home building
    no> supply stores. It's also thicker( 7/8 for what we used) and is easier
    no> to apply paints or finishing coats to.

    no> I talked to a fellow online that was attempting to use wonderboard to
    no> build a set of boxes, though I never heard how it worked out.


    Speaking of experimenting, how about making an enclosure out of a
    semi-rigid shell perhaps 1/4" thick (aluminium alloy?) but lined on
    the inside with sonopan glued to its inner surface? It would lose some
    efficiency but it could then be much lighter weight. I've seen a
    similar sandwich construction used in quieting ventilation baffles for
    mainframe computers so it isn't a new idea.

    A*s*i*m*o*v

    .... A stereo system is the altar to the god of music.
     
  15. That's similar to Aerolam/bitumen idea except that the Aerolam is
    lighter but stiffer for any given thickness and its lightness makes
    the damping layer work more effectively.

    Kal
     
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