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Thread: MDF for Speaker Cabinet!

  1. #1
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    Default MDF for Speaker Cabinet!

    Hello Everyone,

    I live in Toronto and absolutely new in this forum!!! ...

    I searching through the net to find a supplier for MDF sheets. I want to build new cabinets for my JBL L100T speakers. Unfortunately, I haven't been able to find a supplier! I also need some advice about what kind of MDF I need to get.

    Any help would be greatly appreciated.

    Thanks,
    Ramin

  2. #2
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    Default Re: MDF for Speaker Cabinet!

    Windsor Plywoods if you have one there. Home Depot, Rona, etc usually carries it.

    Shouldn't be too hard to find at most home hardware type of outlets.

    Good luck.

  3. #3
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    Default Re: MDF for Speaker Cabinet!

    also you should use a minimum of 3/4" thick material, 1" is better if you can find it. good luck.

  4. #4
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    Default Re: MDF for Speaker Cabinet!

    You have enemies? Good. That means youve stood up for something, sometime in your life. Winston Churchill

  5. #5

    Default Re: MDF for Speaker Cabinet!

    I'd consider baltic birch ply as opposed to MDF for speaker cabs. Building box's out of MDF will have little or no structural strength. Correct me if I am wrong.
    If you are building to last, think ply. I've refit a few bass cabinets in my time and built a few as well. All were out of BB ply.

    My two cents.
    "my hero's are all cartoon characters. What does that say for society, or for me for that matter"

  6. #6
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    Default Re: MDF for Speaker Cabinet!

    I just realized he wasn't talking about a car system...

    As far as strength goes I've never had a problem using MDF for speaker enclosures. Built many sub boxes and such back in high school and college and so long as they were properly built (glued, screwed and appropriate joinery) they held up well. Always make sure you finish it off properly by either vinyl or fabric wrap or you can get a little more creative with fibreglass and paint.

  7. #7
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    Default Re: MDF for Speaker Cabinet!

    the only thing against plywood is that MDF has a better acoustics, most boxes are mdf, so i think he's got the right idea. Besides if its glued and screwed correctly, and possibly he uses dados and rabbits, i cant see it ever coming apart, unless someone tries to take it apart

  8. #8
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    Default Re: MDF for Speaker Cabinet!

    +1 for Baltic Birch, but get ready to dig a little deeper into your wallet... If you do go the MDF route be sure to allow the sheets to off gas for a good chunk of time. You'd be amazed how much MFD will shrink dimensionally after it's stablized.

    Any properly made speaker enclosure should be designed with structural strength in mind. That doesn't mean you can't use MDF, but just keep in mind that any panel with large enough dimensions that will allow itself to be easily resonanted should have bracing to compensate. Using that model, structural strength won't be an issue.

    I of course have no idea, what kind of performance you're looking to get out of your project, but a good place to get some basics, (and some extreme advice) is diyaudio.com

    Good luck...

  9. #9
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    Default Re: MDF for Speaker Cabinet!

    Quote Originally Posted by jason_31 View Post
    the only thing against plywood is that MDF has a better acoustics, most boxes are mdf, so i think he's got the right idea.
    That's actually the complete opposite of what the speaker diy extremists preach... Zero void BB is the defacto standard in the highend world.

    Most diy boxes are mdf because it's cheaper.... by a long shot. If you wanted to survey the whole industry I'd be willing to bet the vast majority of enclosures out there aren't any better than low grade particle board.

  10. #10
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    Default Re: MDF for Speaker Cabinet!

    Wow...this thread takes me back! I remember cranking out custom sub enclosures 20 years ago for autosonics.....High SBL sub boxes mostly.

    Anyway, the reason we use(d) MDF over ply was that the MDF had a low resonance, it was a very "dead" enclosure.

    Depending on the size of the drivers, go with 3/4" at a minimum, if you want the ultimate sound though, sandwich a layer of dynamat between two layers of 1/2" (use the factory adhesive on one side, 3M Super77 on the other to glue the sandwich together) and reinforce with 1" screws. Fill all of your screw holes and dress all your edges and seams with bondo, then gelcoat or wrap with hot vinyl
    I dream of a better world, one where chickens can cross roads without having their motives questioned.

  11. #11
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    Default Re: MDF for Speaker Cabinet!

    U will get a better sound quality with MDF then anything else because its so dense ,the sound comes out through the speaker not the wood !
    Dont forget to predrill before u screw it together ,u could use a good exterior glue rather then interior !


    Thats my 2 cents worth !

  12. #12
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    Default Re: MDF for Speaker Cabinet!

    Ok... The only common element between this site and the diy audio forums I used to live on is the use of wood in projects. Frankly, if I wanted to get into this debate yet again, I'd go back there...lol.

    To any who would like to know the pros/cons of both building materials for use in speaker enclosures. I suggest you do some reading on diy audio forums. There's more to it than the specific weight of the wood.

    However, do yourself a favour and just use mdf... No point jumping head first into that world, unless you enjoy analysis paralysis.

  13. #13
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    Default Re: MDF for Speaker Cabinet!

    Quote Originally Posted by Ryan Shervill View Post
    if you want the ultimate sound though, sandwich a layer of dynamat between two layers of 1/2"
    Some would argue that the ultimate enclosure would have no dampening what so ever and be so stiff with internal bracing that you couldn't resonant it within the passband.

    I personally subscribe to that methodology, but it makes construction considerbly more difficult.

  14. #14
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    Default Re: MDF for Speaker Cabinet!

    Quote Originally Posted by J. Vibert View Post
    Some would argue that the ultimate enclosure would have no dampening what so ever and be so stiff with internal bracing that you couldn't resonant it within the passband.

    I personally subscribe to that methodology, but it makes construction considerbly more difficult.
    The only problem with that approach is that all of the bracing, in itself, can cause distortion.

    The only trully effective way to brace the crap out of a sub enclosure is to use the enclosure as the bracing.....5th, 6th, 7th order bandpass boxes would fill this, but you'd need a HUGE space to be able to fit the enclosure
    I dream of a better world, one where chickens can cross roads without having their motives questioned.

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    Default Re: MDF for Speaker Cabinet!

    Quote Originally Posted by Ryan Shervill View Post
    The only problem with that approach is that all of the bracing, in itself, can cause distortion.
    WUT....? distortion of what...? standing waves maybe...? That's something you want to disrupt.

    edit:

    Here's a couple of examples of an effective means of internal bracing...
    05_bracing.jpg
    horzbracingopt.jpg

    The second example is actually better as it's pattern is slightly less uniform.

    Anyways, rather than derail any further, (or is this "drift") lets start something in the off topic forum.
    Last edited by J. Vibert; 02-29-2012 at 10:13 PM.

  16. #16
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    Default Re: MDF for Speaker Cabinet!

    No need to start another thread....this info could be valuable to the OP

    Those pics are impressive! Did you cut them by hand or CNC? Go gentle on me....my experience is based on the knowledge available in the infancy ( was competing in EARLY IASCA) of performance car audio (pre-digital/DA conversion....tube amps, etc.) so there is a ton I don't know/understand on the topic anymore
    I dream of a better world, one where chickens can cross roads without having their motives questioned.

  17. #17
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    Default Re: MDF for Speaker Cabinet!

    Ok, bare with me... It's been a while since I've talked audio.

    Those pics are something I had on file since the last time I had this conversation...lol. They aren't mine, and to be brutally honest aren't the best example of the right way to do it.

    There's two schools of thought when it comes to controlling panel/enclosure reasonance. Your example of the sandwiched dynamat is the dampening method. Which mainly is the process of making the panels of the enclosure as heavy a possible. The idea being, the more mass, the more energy needed to move said mass. Looking at it quickly, there doesn't seem to be anything wrong with that approach. However, and especially with sub enclosures, you will still have the needed energy to excite the panels. The problem, is you haven't elminated the issue with adding mass. You've just attempted to hide it with mass. Without getting into math, simply because I really don't want to...lol, here's the jist of it.

    Lets pretend your panel's dimensions allow a disposition for it to be excited by 20Hz. 20Hz in some magnitude will excite that panel regardless of it's mass. A panel with two fixed points and a floppy middle will flex. Yes I'm sure you could get it heavy enough to overcome your max forces but gas is on the rise so lets be practical. The key element though isn't 20Hz. It's 40hz, 80hz, 160hz...so on so forth. Those are all the other frequencies your panel will be producing while being excited by the 20Hz tone. Worse yet, even though you've dampened your panel. Once you've got it moving it's going to want to keep moving.

    Now forget about dampening for a moment, and lets focus on the panel's dimension that's sympathetic to the 20Hz tone your driver is creating. Rather than trying to prevent it's motion by weighing it down, let's just remove the possibility. The only way to do that, is to divide the panel's dimension into smaller segments. Ok fine, here's some math... let's keep it really easy and say a 20" panel will be sympathetic to a 20hz tone. So what do you do..?..., you place a structural support somewhere along the panel to remove the excitation at that tone. Here's the trick...

    If you halve that 20" panel with internal bracing to create two 10" panels you removed the possibility of it resonanting at 20Hz. You've also removed the 40, 80, 160... However, you're newly created 10" panels share the same dimension, and therefore will be excited by the same frequency. You're best approach is to divide the large 20" panels into two smaller but dimensionally different sections. Symmetry is you're enemy when trying to control reasonance. The more random you can be, the better off you are. That even goes with the braces you use. Somewhat like the earlier pics. For sake of internal volume you really should "hollow out" the braces so you can reap the benefits without killing the volume. Those braces should be treated the same as an external panel, as they can be excited and reproduce frequencies just the same.

    One last benefit to bracing over dampening... You need more energy to get a panel resonanting at say 40hz as compared to 20hz. So yes there is a limit to how much bracing you can effectively do, but you would need to double/triple the relative power that you needed for the "20hz panel" excitation, to get the "80hz panel" moving. That 80hz resonance will also decay much faster than the 20hz.

    If you really put some effort into bracing, you can effectively push up the resonance of all your enclosures panels above the passband. Thereby creating a resonance free enclosure..., regardless of the amount of power you're producing.

    Sry so long winded... I'm attempting to stand on the shoulders of others here, so I'm sure I'm leaving something out that's improtant.

    Here's an example of one of the best ways to randomize holes in an internal brace to quell it's own resonance:
    Untitled.jpg
    Last edited by J. Vibert; 02-29-2012 at 11:54 PM.

  18. #18
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    Default Re: MDF for Speaker Cabinet!

    So just curious. After all of that, con you really tell the difference? I suppose it's kind of like tasting wine or something...

    I found it interesting, didn't understand most of it, and am now glad I'm not planning on building any speaker enclosures!

  19. #19
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    Default Re: MDF for Speaker Cabinet!

    lol... probably not...

    I should point out that I'm not debating which wood sounds better. My hearing isn't anywhere close to where it would have to be to distinguish being material types in a blind comparison, if it's even possible.

    In terms of building methodology, it's just simply two ways to skin a cat. What method you choose plays into the building material I think.

    The whole thing really comes to full circle if you look at the mdf vs BB ply reccomendations. I personally believe a brace with ample holes cut into it to retain enclosure volume, should be made with ply rather than mdf. MFD may be dense but it isn't very strong. Zero void BB on the other hand is stiff stuff, and fairly dense as ply goes. So if you subscribe to the internal bracing, then BB ply is the better choice, imo...

    If you want mass, and to save some money, then obviously mdf wins it. Of course if you do multiple layers of mdf for sake of the added mass. You may just be back in the range of the BB ply costs . Frankly, I'm just done with working with mdf...nasty stuff.

    Waaay back, I even used threaded rod to control panel flex in sub enclosures....

  20. #20
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    Default Re: MDF for Speaker Cabinet!

    A bit more on building of speakers http://www.diyaudioandvideo.com/FAQ/Build/.
    They are also advocates of mdf. More than you ever wanted to know about mdf and other materials to build speaker enclosures http://www.diyaudioandvideo.com/FAQ/MDF/#Q7
    It seems that all MDF isn't the same. You can be sure that the big box stores will choose their product based on lowest price and a construction application. If you want something different from that, I suggest you try a specialty firm that could source different products such as Peacock Lumber in Oshawa if you are an east-ender http://www.peacocklumber.ca/.
    If plywood is any indication, there is a world of difference between the quality that Peacock offers compared to the big box product.
    I'm sure there are other suppliers around the GTA who offer similar quality and range of product to Peacock that may be more conveniently located to you.
    Last edited by Rick Thom; 03-01-2012 at 05:04 AM.

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