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Thread: Speaker cabinet design

  1. #1
    Join Date: Dec 2011

    Location: sussex

    Posts: 124
    I'm phil.

    Default Speaker cabinet design

    Got a pair of superpensil 12's . I made the cabinets out of 20mm MDF but they need respaying so I'm wondering if I would be better making a new pair out if 18mm birch ply if what are the advantages.
    Technics 1200, Ian Mac bearing, rb300 AO arm funk mat modded plinth external psu, angle audio studio pro mc virtual battery phono amp, Onix pre and mono amps, Onix CD player, Onix BWD and soap tuner. B&W dm2 speakers or super pencil 12 speakers, atlas cables, seperate mains power supply with earth spike.

  2. #2
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 272
    I'm Dennis.

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    From my experience and reading you are better of with MDF because it is a lower Q material, and so more self damping.

    In the 60s many cabinets were made from ply which has a higher Q and produces quite noticeable resonances with a knuckle wrap test, many of them making a hell of a racket, but in horn designs not so noticeable because they tended to be coloured anyway.

    Chipboard is even lower Q, but is mechanically low quality to work with, and weak.

    My choice is MDF with corner bracing with fillets of the scotia profile, using PVA.

  3. #3
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 26,848
    I'm Geoff.

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    Quote Originally Posted by Pharos View Post
    From my experience and reading you are better of with MDF because it is a lower Q material, and so more self damping.

    In the 60s many cabinets were made from ply which has a higher Q and produces quite noticeable resonances with a knuckle wrap test, many of them making a hell of a racket, but in horn designs not so noticeable because they tended to be coloured anyway.

    Chipboard is even lower Q, but is mechanically low quality to work with, and weak.

    My choice is MDF with corner bracing with fillets of the scotia profile, using PVA.

    Yes, I agree with what you say. The use of MDF in speakers has been blighted by negative comments recently, probably by people who have not compared its capabilities. It's my choice of (reasonably economic) materials.
    Mr. Tact!

    Main system: MMs/ADCs/Low output MC's/One rare Japanese SUT/One scarce British phono stage/various tonearms/hefty Japanese DD TT and hefty Japanese BD TT and small British BD TT. 4 CD players/2 jitter buster/2 DACs/Valve buffer. TVC stepped attenuator or valve pre-amp or solid state pre-amp. Current dumping power-amp or either of two Class A SS power-amp or Class A EL34 valve monos or big Japanese (part Class A) integrated. Big dual concentric speakers/Smaller dual concentric speakers/Two way British compacts and full range speakers, amongst others. And too much more to list!

  4. #4
    Join Date: Dec 2011

    Location: sussex

    Posts: 124
    I'm phil.

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    Thank you both. Off to the spray shop, will post the completed pics when done.
    Technics 1200, Ian Mac bearing, rb300 AO arm funk mat modded plinth external psu, angle audio studio pro mc virtual battery phono amp, Onix pre and mono amps, Onix CD player, Onix BWD and soap tuner. B&W dm2 speakers or super pencil 12 speakers, atlas cables, seperate mains power supply with earth spike.

  5. #5
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 613
    I'm Andrew.

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    This is a BBC research paper about loudspeaker cabinet materials
    http://downloads.bbc.co.uk/rd/pubs/reports/1977-03.pdf

    It makes for interesting reading. I don't think MDF was available at the time but quite a few other materials are examined.

  6. #6
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 272
    I'm Dennis.

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    I haven't read the paper, but the BBC had its own philosophy now continued by Harbeth in which they used flimsy panels damped with heavy layers of bitumen, the idea being to put the resonances outside the critically audible ranges.

    I'm not convinced that this approach is very beneficial, especially as the flexing can seriously compromise bass performance as the cabinet walls are sucked and blown in and out.

    I suggest that if it was a real universally accepted breakthrough technique, it would be more widely adopted.

  7. #7
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 613
    I'm Andrew.

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    Quote Originally Posted by Pharos View Post
    I suggest that if it was a real universally accepted breakthrough technique, it would be more widely adopted.
    I'm not advocating the BBC's approach as such, just pointing anyone interested in the direction of some interesting reading from a reputable source, based on some research and without a commercial axe to grind.
    Actually, I think the principle of minimising panel resonances is very widely adopted - they just don't all take the same approach to it as the BBC did. I think the BBC wanted to reduce audible resonances in the midrange without having extremely thick/heavy cabinets.
    Anyway, it's there if anyone wants to read it.

  8. #8
    Join Date: Dec 2015

    Location: vancouver

    Posts: 642
    I'm danilo.

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    Try particle board? MDF is a semi recent material and anecdotal (at least) info suggests it ,
    despite it's pedestrian nature/price point, is a surprisingly decent enclosure medium... superior to MDF by many claims.
    Certainly more stable under paint if nothing else.
    My audio bits: Thorens / diy phono, CD/dvd player(s), diy pre, F6, Tannoy Golds in my boxes / my xovers, and of course all strung together with basic diy Wires
    Lots of Cd's, yet more audio files, a couple of hundred semi worn Lps.

  9. #9
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 272
    I'm Dennis.

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    Of course you are right about damping Andrew, that is not in question, but that the BBC's technique had not been universally adopted, and so is a relatively 'out on a limb' solution, was my point.

    Particle board may well be lower Q, I think ESS used it to an extent.

  10. #10
    Join Date: Apr 2008

    Location: east yorkshire

    Posts: 497
    I'm steve.

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    Quote Originally Posted by moodybuilder View Post
    Got a pair of superpensil 12's . I made the cabinets out of 20mm MDF but they need respaying so I'm wondering if I would be better making a new pair out if 18mm birch ply if what are the advantages.
    Your best placed to answer this your self , listen to them with a bit of volume, does all sound well ? Feel the cabinet while playing is there any vibrations / resonate areas of the cabinet thats vibrating, this will colour sound, you may or may not recognise/ hear it.. But its there..

    My own experence of materials is is mostly limited to open baffles and large back horns, mdf imparts a dull sound to the music, sort of greyness that is unnatural sounding.
    birch ply gives the music a brighness but can resonate suprising easily, (and its easily felt), and if you know what to listen for, quite audible.
    Flooring grade chipboard to me is much better sound wise than mdf, its brighter sounding with out the dullness of mdf, it seems to be less resonant in larger panels, using the thicker grades works well,

    In slim speakers like yours the sound is likely to be less influenced. But its is unlikely there will be no difference (someone somewhere would point it out.... )
    I think scott ( the designer) brought a pair of these round to my house a few years ago and as i remember they sounded very good,
    I organise the audio talk meets and have heard alot of speakers over the years, sometimes the material they are built from is easily heard, but with others its not- so good design and construction is the first priority...
    Hope thats some use
    Steve
    Last edited by SPS; 06-05-2017 at 08:39.
    collector and DIY user of old british triode valves

    Open baffles / single ended diy px4 and px25 valve amps

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