MDF vs. Hardwood for speaker case. Sonic differences?

Discussion in 'Archived Threads 2001-2004' started by Steve Elias, Jan 21, 2002.

  1. Steve Elias

    Steve Elias Stunt Coordinator

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    I'm toying with the idea of DIY bookshelf speakers, and wonder if there is any reason not to use a hardwood (specifically quartersawn white oak) other than cost. Most speakers I've seen, whether DIY or retail, are MDF with laminate. And while I have your attention, I'd love to hear some recommendations for high quality speaker/crossover kits that I might use for this project. Thanks.

    -Steve Elias
     
  2. jeff lam

    jeff lam Screenwriter

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    I just finished a kit from GR-Research not to long ago and I can't say enough good things about it. A true value at the price point. I highly highly recommend them. The best bookshelf monitors I have ever heard at any price point.

    GR-Research.com

    AdireAudio has a few good kits from what I hear.

    ACI also has some good kits but they are a little more pricey.

    Speakerpage.com is the cheapest and several people here have had good things to say about them.

    Also look at madisound.com or partsexpress.com for some kits.
     
  3. Greg_R

    Greg_R Screenwriter

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    It has to do with the resonant qualities of the wood. Ideally, you want a non-resonant enclosure (MDF and marine grade ply are typically used). You may want to consider resawing the oak into veneer if you like the look of the oak (or purchase commercial veneer).
     
  4. Wes Nance

    Wes Nance Stunt Coordinator

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    Dennis Murphy's MB1's are quite similar to GR Research AV-1's, and you can find the design/plans on murphyblaster.com. I plan to build a set this summer. . .

    Supposedly these sound *very* good for the money, as do the AV-1's, I've heard.

    Wes
     
  5. Mark Krawiec

    Mark Krawiec Agent

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    two reasons.
    one, already mentioned, hard and softwoods have resonances which can color the sound. You can design to minimize these, but it takes a bit of test equipment and skill.
    two, manufactured wood products are dimensionally stable. Real woods expand and contract over time, and you will likely develop an air leak. If your joinery skills are very good, you can design around this.
    As you can see, the easiest approach is veneered mdf. Ply can be used in subs. It's dimensionally stable and it's resonances are usually above the typical sub cutoff.)
    As for kits, as well as the aformentioned, try Zalytron and be sure to check out speakerbuilding and speakerbuilder.
     
  6. Steve Elias

    Steve Elias Stunt Coordinator

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    Thank you all very much for the links. They are very helpful. As far as the hardwood construction is concerned, you've pretty much convinced me to stick with MDF and veneer. I'd planned on using dovetail joinery to combat expansion and contraction (which is somewhat less of a problem here in southern California), but the resonance issue is more than I want to deal with. Thanks for the cautions! I'm hoping to create speakers that are on par (or better?) than the usual suspects (Paradigm, B&W, Monitor, PSB, and so on...) for a combo music/HT system powered by my Rotel RB-985MkII amp. Thanks again.

    -Steve
     
  7. jeff lam

    jeff lam Screenwriter

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    Wes,

    I actually have the MB1's too. I just got the cabs for them which I had the problem of them being brown and not black(other thread). I am breaking them in now and from what I can hear, they are amazing. Very much like the AV1's

    When this is all over and I A/B the MB1 vs. the AV1, at least some of us will know which crossover design sounds better. All I know right now is that Danny's crossover is much simpler. Honestly, I'm not expecting them to be much different at all, since they use the exact same drivers and nearly the exact same alignment and cabinets.

    All I can say is both of them are of Audiophile quality! And at this price, it's a no brainer.
     
  8. Ron Shaw

    Ron Shaw Stunt Coordinator

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    As others have pointed out, resonance issues are the reason MDF is used (particle board, basically). MDF has 1.7 times the damping of equal thickness plywood. Ideally, concrete would be used, but this is hardly practical. Veneering a particle board enclosure is easy to do. My favorite source for veneer is Tape Ease. Here is their web site: http://www.tapeease.com/ They have great prices, and excellent quality. I recommend single thickness veneer (.010 thk). It sands easily, and corners disappear. Cut the veneer about 1/4 in. larger both ways than the surface it is to be applied to. Apply with contact cement. Coat both the box and the veneer, and let the contact cement dry before applying veneer. Lightly lay a layer of newspaper over the box (don't press it into the contact cement, or it will stick) and then position the veneer over it. The newspaper prevents sticking until you have it properly aligned. Then, begin to pull the newspaper out from under the veneer (a small bit at a time), pressing the veneer down to the box. After the newspaper is completely removed, press down well over the entire surface to insure good adhesion. Then, just sand down the edges with fine sandpaper over a sanding block.
     
  9. Steve Elias

    Steve Elias Stunt Coordinator

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    Thank you, Ron, for the advice on laminate and laminating. I've only laminated MDF once before and that was thirteen years ago so your advice is much needed.

    Jeff, I look forward to your comparative review!

    Thanks everyone.

    -Steve
     
  10. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Steve, now that you know to not use solid hardwood for speaker cabinets, on to joinery...you do not need to use dovetail joinery the pins would be so delicate, they'd break off during assembly. I tried a large lock-miter router bit once, and the thin line of MDF broke as I slid adjoining sides together. I recommed rabbit joinery, but lately have gone to butt joints, which are very strong if you use enough carpenter's yellow glue. Also, you do not need to use any screws, which will save you a good bit of labor. For large subwoofer cabinets where it's hard for one person to handle the big panels, I'd use a brad nailer after applying glue and aligning the panels - not for joint strength, but to hold the panels together and in alignment while the glue dries. All this learned the hard way via building several cabinets of different sizes the last few years. I recommend the 10-mil paper-backed veneers and wax paper makes a good separator while positioning glued veneer.
    Now go make some sawdust [​IMG]
     
  11. Steve Elias

    Steve Elias Stunt Coordinator

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    Thanks Hank! I was only planning on dovetail joinery if I made the cabinets out of solid hardwood. Now that that material is out of the picture, so are the dovetails, for the reasons you mentioned. I have been considering biscuit joinery or rabbit joinery for the case, but I will reconsider butt joints on your recommendation. Sometimes the easiest way really is the best choice, although I must admit to having a built-in bias against butts joints thanks to one of my other hobbies - making Arts & Crafts furniture. Thanks also for the wax paper tip.

    -Steve
     
  12. Ron Shaw

    Ron Shaw Stunt Coordinator

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    Use glue blocks in the corners of the box. Butt joints alone can be fairly weak, especially in a material like particle board. In my early days of building loudspeakers, I tried wax paper as a temporary barrier, but it didnt work as well as newspaper. The slick surface wanted to cling to the contact cement (you would think that it would slip easily, but thats not what I found). Also, if your box is large, it may take more than one width of wax paper.
     
  13. Jack Gilvey

    Jack Gilvey Producer

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    Wow, lots of very valuable info from these guys. I feel that MDF is probably best for "full-range" speakers, but I prefer a good no-void ply (thanks, GM) for subs (not just any ply will do). I used 3/4' marine ply for one I'm finishing up now, it's great to work with and is much stiffer than MDF for an equivalent thickness. With a little bracing (2x2 in my case) it's easy to push the resonance of the cab much higher than would ever be excited by a sub. It does ring like a bell (literally)when knocked, though, which would put some people off. What it tells me is that the resonance is right where I want it.

    I use butt-joints myself (skill- and tool-dictated decision), and the combination of perfectly square cuts (finally used a table saw), a few Bessey K-body clamps and Gorilla Glue worked astoundingly for my last project.
     
  14. Derrick G

    Derrick G Stunt Coordinator

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    You may also want to check out www.northcreekmusic.com. They only use high quality drivers (Scan Speak and Vifa) with custom, hand-made crossovers. They're not as well known as GR Research, but they have a perfect 5.0 rating on audioreview and are highly recommended on the audioasylum. I am fixing to order a set of the Okaras. I'll let everyone know how they sound when I get them up and running.
    Derrick G.
     
  15. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Also, I believe the Northcreek cabinet construction method is THE way to build speaker cabinets, but only worth the effort for high-end (very best drivers/crossovers/design) speakers. Their cabinet building manual is worth the nominal cost.
     
  16. Steve Elias

    Steve Elias Stunt Coordinator

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    As Jack stated, there is a lot of valuable info in this thread. I thank you all. And now to check out North Creek Music...

    -Steve
     
  17. GeorgeHolland

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    I can certainly recommend North Creek Music and the quality of George Short’s cabinet design and crossover quality. I have recently finished building a pair of their newest design, the Vision Signature. http://www.northcreekmusic.com/Vision/VisionInfo.htm
    Before that I built the Leviathan Subwoofer in a 4>3’ sealed design. The Vision cabinet “is ruggedly constructed and heavily braced as described in the North Creek Cabinet Handbook, with an MDF shell, laminated MDF - Baltic Birch fronts and backs, and Baltic Birch bracing.”(quote from the NCM web page)
    If you look at one of the pictures on the above Vision link you can see George Short actually used hardwood for the top rather then the MDF called for in the Vision cabinet plan. He also assured me I would have no problems laminating hardwood to the outside of the Baltic Birch front. I ended up using a piece of
    1 ½” solid Oak for the outside front. I also used ¾” solid oak on the top, but in my case I laminated the top oak piece to a piece of ¾” MDF.
    His design includes an internal cabinet treatment utilizing North Creek Glop. The glop helps minimize resonance’s and is applied inside of the first or driver compartment of the Multichamber Aperiodic Progressive Damping design.
    I continue to be amazed by the quality of these speakers. They are quite simply the finest I have ever heard, I have found no weaknesses. I find myself listening to more music then I ever have. I find myself playing music much louder than I used to and the sound is never fatiguing in any way. I have also noticed music retains a proper balance and is more enjoyable to listen to even when playing at a much lower volume level. But since this thread is about cabinet constuction, I will leave my Vision review for a future post.
    George
     
  18. Doug Fraser

    Doug Fraser Extra

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    WRT to using MDF or hardwood, here is what I have found.

    I built bookshelf speakers using 3/4" Cherry and 3/4" MDF. The cherry units where made for the L, Centre, R and Surrounds. The MDF ones where to be mounted between ceiling joists for the rear channels and no one would see them, thus the use of the MDF.

    The Cherry units use lock miter joints, the MDF units biscuit joints. Other than the wood and construction tequniques they use the same drivers, same crossover, same stuffing, same grills, same terminal cups, same internal wiring etc.

    I have done considerable critical AB listening (with the speakers beside each other, before mounting them in the appropriate location for HT use) and have concluded that there is no audible difference.

    From a wood working perspective MDF does not crack, expand, shrink whereas, depending on humidity variation, Cherry could. This may lead to problems in the future. Cherry is very nice looking, exudes quality while MDF, is well, MDF.

    Cherry is expensive, MDF is relatively inexpensive.

    Since these were bookshelf speakers they is not that much energy being pumped into the boxes from the speakers. I have set my speakers to small on my Integra 9.1 receiver, therefore frequencies are rolled off at 80 Hz (THX spec). What I am trying to say is that there is no 15" woofer moving large amounts of air and perhaps causing the case to flex and/or resonate. Also, the dimensions of the case are small so there is no large unsupported panel areas that can flex and/or resonate easily.

    My conclusion is that if you want your bookshelf speakers to be a piece of fine furniture and are willing to put in the extra effort in constructing them then use hardwood, otherwise use MDF. With my bookshelf speakers there is no audible reason to use cherry or other hardwood just esthetics.

    Regards,

    Doug
     

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