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What's the deal with MDF?


dohhhhh6

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Hey, I've been doing a lot of research (well... some...) on MDF, or Medium Density Fiberboard.

 

It's cheaper than most woods, is less resonant, and is easier to work with... so why aren't more bass cabinent using it?

 

It supposedly reflects SPL and doesn't color the sound as much as opposed to plywood that has wholes in it that absorb certain frequencies and color the sound. That seems pretty bass worthy to me.

 

I got introduced to MDF by www.drbasscabs.com It's a small company that make bargain priced bass cabinent out of both plywood and MDF. Interesting stuff.

 

MDF is also used in TONS of home theater sound type speakers. It's also a favorite among DIY speaker makers for it's cheapness and ease of use. However, the experienced ones notice an MDF tone to MDF speakers, some hate the quality.

 

So, can anyone tell me why more bass speaker companies don't use MDF? I'm particularily looking for responses from Numba 6 and a few more knowledgable individuals about this, though all are welcome.

 

Any

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I work at Home Depot in the Lumber and Building materials department, so I feel qualified to answer. (that doesn't mean I am) From the many many sheets of both that I get to play with every day, they are very close in weight. Other than that pearl of wisdom I know nothing. :(

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For those who believe, no explanation is necessary. For those who do not, none will suffice.

 

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Medium density fibre board is a fine material for making cabs. When I'm not so totally under the influence of alcoholic substances, I can elaborate.

 

Basically, higher density materials make things sound better. The speaker enclosures in my truck's stereo are all made of 1 1/4" MDF material and it rocks like you can't imagine; especially with nearly 1500 watts behind it. MDF good when done properly. A lot of your speaker response has to do with how it's ported and tuned. Anyway. YEah.

 

-Drunkard Bri

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Originally posted by Da LadY In Tha Pink Dress:

It's cheaper than most woods, is less resonant, and is easier to work with... so why aren't more bass cabinent using it?

Caveat: I'm neither a speaker cabinet maker nor carpenter, but I have played engineers on TV...

 

The differences between typical MDF and void free plywood are as follows. MDF is denser (~800kg/m3 vs ~600kg/m3), stiffer (haven't found any numbers yet) but less strong (likewise)

 

If you don't care about weight, then it's relatively easy to make a very stiff, strong and non-resonant enclosure out of MDF - which is why almost every single home speaker cabinet is make from MDF. However we have to move our bass rigs so weight is a factor.

 

Once you start trying to reduce weight, MDF begins to cause problems. Although thickness for thickness it's stiffer than plywood, it's not as strong due to being more brittle, so you can only go so thin whilst still being road-worthy. Even then its higher density makes the cab that much heavier. It's reduced strength also makes it harder to make the joints as strong.

 

There are cabs out there made of MDF (or OSB - oriented strand board - which is a stronger variant), including Trace Elliott, Basson and Wayne Jones. They are all seriously heavy - TE & Basson 4x10"s are around 120lbs+, whilst Wayne Jones's 2x10" is about 75lbs IIRC. As most of the players that spend money on bass cabs don't have roadies weight is an important factor. A carefully cross-braced thin plywood cabinet can reduce the weight of a 4x10" down to less than 80lbs and a 2x10" to less than 50lbs (and less if neo speakers and low density ply (poplar rather than birch) is used - <60lbs for a 4x10"!!!) whilst still maintaining sufficient non-resonance/absorbtion to have a good sound. That's a big difference - I know what I'd prefer to gig with!

 

Alex

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plenty of companies do make cabinets out of MDF, but it's not exactly a selling point. so they usually don't make much of the fact. and when build material is a selling point, it's plywood.

 

for example, my employer, peavey, makes two levels of bass cabinets. our mid-level TVX (tour series) cabinets use MDF. they're heavier, they don't sound as good as our best, the PRO series cabs. pro series cabs are made of plywood. they're lighter and sound better than TVX cabs. this has something to do with the speaker drivers, but it also has to do with weight, market, and cost.

 

there are 38 reasons i switched to the bergantino HT-112 as my only cab, and MDF ain't one of them.

 

robb.

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i invite anyone that has ever derided tube amps for their weight to lift a sheet of 3/4 plywood and then lift a sheet of 3/4 mdf. i'm all for tube amps but i would never want to lug around an mdf cabinet.

 

it's fine for home stereo speaker use because you plop those guys down and rarely move them.

Eeeeeehhhhhhhhh.
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invite anyone that has ever derided tube amps for their weight to lift a sheet of 3/4 plywood and then lift a sheet of 3/4 mdf. i'm all for tube amps but i would never want to lug around an mdf cabinet.

 

Interesting point. I'm getting ready to build a 1x15. Most DIY sites say to use MDF. I think I will use mdf, but thanks for the weight warning. I'll definetly plan in some casters. Being a bass player heavy amps and cabs kinda go with territory. Also as a bassist, tubes vs no tubes was never a factor for me. IF it sounds good it sound good, but if you play 6 string, and you're willing to sacrifice tubes for weight. There's something wrong with dat.

Together all sing their different songs in union - the Uni-verse.

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Interesting point. I'm getting ready to build a 1x15. Most DIY sites say to use MDF. I think I will use mdf, but thanks for the weight warning.

MDF is easier to work but, as has been mentioned, much heavier. MDF is also less moisture resistant than ply.

 

Are there any cabs. out there with a clear finish?

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Originally posted by a boy named sue:

Are there any cabs. out there with a clear finish?

Bag End

 

There may be others, and it seems to me that the few who do offer them are similar to Bag End in that they specialize in installed sytems in addition to instrument cabs.

 

Back to MDF... the only thing I might add is that it doesn't accept any old screw like wood does. Be sure that you use recommended fasteners.

- Matt W.
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The original post stated that MDF is easy to work with. I don't do lots of woodwork, but I've worked with wood boards, plywood and MDF. I do not like working with MDF. Just look at that "assemble at home" furniture that you buy to see that the joining techniques are very different.

 

One other characteristic I've noticed is that MDF is susceptible to moisture damage. The edges tend to expand and fracture when damp. That's not much of a problem in my den, but outside the house?

 

Jeremy - your unit must be well-sealed and well taken care of to last that long.

 

Tom

www.stoneflyrocks.com

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Be practical as well as generous in your ideals. Keep your eyes on the stars and keep your feet on the ground. - Theodore Roosevelt

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It's easier to make a good freq enclosure with MDF because it requires less work to get close to acoustic rigidity. That means the panels vibrate less themselves, which can conflict with the tones that one is attempting to reproduce. This absorbs energy (and of course translates it into heat) and thus can be less efficient and less focused - less pure. This is especially true for lower freqs. It is also less resonant - and HEAVIER. It is often the choice for expensive fixed installation designs, and studios.

 

It's actually pretty easy to work with if one is set up with the proper tools, but can be a bit flakey with typical hand tools if one wants to NOT cover it with carpet or whatever. It cannot take quite the impact and corner abuse well constructed plywoood boxes can, but treated decently and finished decently can last many decades.

 

Plywood qualities and densities vary (wood species are chosen for average weight and propensity for density - lack of voids, bad knots, etc - and more layers (and thus more glue) tends to take some of its rather pronounced resonance back a few notches. Then the rest is achieved by bracing.

 

The best cabinet designms for portable applications these days have a lot of research and trial and error into them as concerns bracing. Good bracing practices can allow one to use lighter and thinner plywoods, for example. Especially for subwoofers good bracing is important. This keeps the panels from moving as much and soaking up power, and makes the cabinets more focused and accurate. When you get into single components with RMS ratings as high as 1200 watts you don't want anything that will drag down the performance or durability.

.
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