Will the real "MDF" step forward?

[HornEd]

Klipsch "Legends" are made of "MDF" or so the specs say. The motor board in a KLF 30 looks like "particle board" with its yellowish cast. The MDF my son bought at Home Depot to make a new motor board version for my horizontal center channel KLF 30. The stuff he bought is heavy, dense and grayish and looks more like cardboard... is quite inexpensive... and is not as "tough" as the stuff of "Legends."

Can any of you speaker cabinet mavens out there give us a clue as to what makes the best motor board... and where we can get it? We just don't understand all we know about building a better motor board... and we know that Klipsch goes through several painting and smoothing sessions to get their motor boards looking spiffy. Help!!! HornEd

PS: The data cable to my new cell phone hasn't arrived so I will not be able to respond to any helpful hints until after Labor Day. No Internet and low-speed Klipsch... yeah, this is "roughing it!"

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"Where Legends Live! Klipsch Powered HT"

FOREGROUND SOUND STAGE:

KLF 30 Center, KLF 30 Mains, KLF 10 Front Effects

BACKGROUND SOUND STAGE:

KLF 30 L&R Side/Surrounds, KLF 30 Rear Effects

LARGE MOUTH BASS:

Twin SVS CS-Ultra sub with Samson Megawatt Amp

SPEAKER SUPPORT SYSTEMS:

Mitsubishi RPHD1080i 65", Yamaha RX-V3000 Receiver

Toshiba Pro Scan 6200, Toshiba Pro 6-head SVHS W808

and such... Tweakin' On!

Music Respite Room: Cornwalls (SVS 16-46/Ultra pending)

Klipsched Motorhome SB2 main's, temp. small Infinity sub & speaker's for placement tests, Yamaha 5-disc DVD/CD 996, 17" flat screen monitor

Under Construction (It's a "puzzlement!")

This message has been edited by HornEd on 08-31-2001 at 05:53 AM

[Ray Garrison]

Hi Ed! How are you feeling?

Hummm... "...what makes the best motor board..."

This ought to be interesting. I'm very curious to see what types of response you get. I've been involved with some construction projects involving big, multi-driver ugly looking speakers. I worked with Clark Johnsen of the Listening Studio in Boston a few years back, making my own cabinets for a pair of psuedo VMPS SuperTower II A/R Special Edition speakers.

(Just to give you an idea of the scope of this, in case you're not familiar with VMPS, here's a quote from their website referring to these speakers...

"It was Bert Whyte, late Senior Editor of Audio Magazine, whose April 1980 review ("Towers of Power") of the 6ft 6", 250 lb. VMPS Super Tower IIa/R put us on the map, validating a unique design philosophy which emphasized full spectrum reproduction at intentionally, often spectacularly low prices. The STIIa/R, with its 16 active drivers including four of the most expensive tweeter extant, the Focal T120 harddome, retailed back then for a very affordable $3,876/pr.")

These things had a Phillips ribbon supertweeter, four of the Focal inverterted dome yellow fiberglass tweeters, six (Dynaudio?) 4" midrange drivers, three carbon fiber 12" woofers, one carbon fiber 15" woofer, and a 15" mass loaded passive radiator. I got the drivers and crossovers from VMPS, and built my own cabinets. During the course of the project (a story in itself... I'd sold my pair of B&W 801F to raise money for the components, and found myself in my garage looking at piles of drivers, resistors, inductors, capacitors, wires, a pile of wood, and a serious bout of "What the HELL did I just do?") I talked to a lot of guys in the Boston audio club (don't remember the name), the Connecticut audiophile society, Harvey Rosenburg (RIP Harvey ), Jim Theil's brother (don't remember name) who used to do the cabinets for Jim, Brian Cheney, and bunch of other folks.

Conclusion - everybody has their own opinion. Generally, everyone agreed that:

(1) constrained damping, say by taking two plywood or MDF sheets and bonding them together with a sheet of rubber or sorbothane between them, was excellent, through results in VERY heavy and difficult to work with panels;

(2) Heavy, inert sheets of high density mineral filled resins or polymers work well; things like synthetic marble, Corian (mentioned specifically by quite a few people), though again these are VERY heavy and difficult to machine;

(3) Sheets of hardwood or plywood, particularly if unbraced or minimally braced, resonate like a drumhead;

(4) MDF or Particleboard are better than plywood or hardwood, but not as good as layers of wood with damping between them. Veneering the MDF or particleboard stiffens the panel, moving the resonant frequency up, and provides a modicum of damping.

Couple of definitions:

MDF: MDF is a composite panel product typically consisting of cellulosic fibers combined with a synthetic resin or other suitable bonding system and joined together under heat and pressure. Additives may be introduced during manufacturing to impart additional characteristics.

The surface of MDF is flat, smooth, uniform, dense and free of knots and grain patterns, all of which make finishing operations easier and more consistent, especially for demanding uses such as direct printing and thin laminates. The homogeneous density profile of MDF allows intricate and precise machining and finishing techniques for superior finished products. Trim waste is significantly reduced when using MDF compared to other substrates. Stability and strength are important assets of MDF, and it holds precise tolerances in accurately cut parts.

Particleboard: Particleboard is a composite panel product consisting of cellulosic particles of various sizes that are bonded together with a synthetic resin or binder under heat and pressure. Particle geometry, resin levels, board density, and manufacturing processes may be modified to produce products suitable for specific end uses. At the time of manufacture, additives can be incorporated to provide greater dimensional stability, better fire resistance, or to impart additional characteristics.

Basic difference: MDF is easier to machine, and has a higher quality finish when cut and shaped, because the cellulose particles are smaller and of a more uniform size.

Me, I'd be daring, and go get a section of Corian from Home Depot or Lowes. Assuming you have the tools to cut and shape it.

Have fun!

Ray

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Music is art

Audio is engineering

[fini]

HornEd, Howdy! That stuff your son bought would be the real thing. Medium Density Fiberboard is used extensively in cabinetry and in interior trim because it takes a paint finish and wood veneers so well (it's sooo smooth). They even make it into fancy mouldings, like crown moulding. I have no clue, however, about its sonic qualities, and how they compare with other materials (like plywood, lumber core, etc.).

MDF is easy to work with, but the dust, whether from sanding or cutting, is VERY fine, and goes everywhere, so keep it out of your lungs with a good mask. By the way, there is another product called MDF Ultralight (Ultralite?) that is, as you would expect, MUCH lighter than regular MDF, and is available in 1 1/2" thick panels. Makes nice bookshelving. See ya, fini

[Fried Elliott]

Ray gave a GREAT response.

The MDF you get at home improvement centers is real dense and kind of looks like it was made of super pressurized cardboard.

I have used it in a couple of projects. Good compression load bearing material, not so great lateral. Takes screws and fastners well. Cuts, mills, and sands very nicely with SHARP blades and CLEAN sand paper. Because it is so smooth, any scratches or flaws you introduce will be magnified so work slowly.

[John Warren]

[fini]

Ooh, do I smell a three page, hotly argued, hostility-filled debate a'brewin'? MDF-to screw or not to screw... It'll rival the big wire controversy, for sure!

In MY experience, screwing MDF works in a "screw-and-glue" situation, where the pieces being joined together aren't going to be taken apart. In applications where parts will be removed, I'd use solid wood or plywood- repeated screwing and unscrewing in MDF will eventually drill a hole too big for the screw to "bite."

Two other points: Fasteners driven perpendicular to the surface hold well, but tend to "dimple-up" the area right at the fastener, so close attention should be paid at sanding time. Also, fasteners driven into the "end-grain," even small ones, can wedge the layers apart, so predrill.

So, who thinks I'm wrong, huh?

fini

[John Warren]

at the tightening levels I work to, i prefer

13-ply Baltic, Canadian or Finnish. the screw has to pull the joint together at a pressure consistent with a clamp. For me MDF just doesn't "tighten up" like wood does. I use stainless FH sheet metal screws for construction projects.

This message has been edited by John Warren on 09-02-2001 at 04:31 PM

[Guest BobG]

There are many different grades of MDF available. Some have more glue and less wood which others are the opposite. In Reference speakers, the back and sides are one type while the front panel is a more dense version.

Legend uses the same MDF all around but with different veneer on the back panel.

[Fried Elliott]

Well, MY MDF DOES TAKE A SCREW SO THERE.

Heehee.

The MDF to which I am referring is the stuff you currently find at Home Depot or Lowes and is an extremely heavy dense material that looks more like cardboard or brown paper. You can buy it in sheets or boards. Some is already primed. This stuff is pretty impressive. The "older" MDF looks and works more like particle board. That stuff sucks.

I have used drywall screws with the MDF in both screw/glue and dry applications. I am not sure how hard you guys are driving or tightening your screws, but this stuff is very close to wood in its screwing properties. Gee, I'm starting to get a little excited here...

[John Warren]

[Fried Elliott]

Okay, John, I wasn't going to list the *entire* freakin' inventory of fastners I have used on MDF or even the ones I have in my garage, or even the fastners I have known in my life. Lots of people are familiar with dry wall fastners and I was using them as an example. I am aware of their differences and even the differences between glues. My dad once had a "slab" of animal glue he got in Germany during the war he used in only the most dire emergency repairs, when all else had failed. God, did it smell.

My sense of this thread was that currently available MDF materials were getting a bad rap, which is not consistent with my experience. I am perfectly okay with my Klipsch synergy speakers being made of the modern MDF. However, had I not had some personal experience with it, I would have considered it "cheap".

BTW, I have not glued any MDF to plywood, but I have glued it to some #2 pine I had to pull apart. Result: the pine splintered first.

[fini]

Fried Elliott, I don't know about anyone else here, but I'd love to hear you expound on the fasteners in your garage. A few photos would be a bonus--- could you get your socks in the shot, too?

Thanks, fini

[John Warren]

Tightbond makes a liquid hide glue (animal glue from hoof, bone, cartlidge, etc) that is treated with anti-bacteria additives. Has a shelf life of six months.

It has no odor.

For wood, hide glue is superior to synthetics. Musical instruments like piano frames, violins, and alike, were, and still are, glued together with this stuff and those joints last 100's of years.

When building Klipschorns, there is no better glue, it takes hours to set-up and gives the assembler plenty of time to get it right. It forms a chemical bond to the wood, unlike PVA.

[Fried Elliott]

Hey fini!

No problem on the photos --- uhh, no wait second. I'm not wearing any socks!

[WMcD]

I myself stick with plywood for construction. However, it may be a bit of snobbery over price.

One good thing is that I'm used to working with it and there don't seem to be any particular special screws or glues necessary.

I'd think that if you get the technique going, MFD is not going to produce an inferior speaker by any means.

Gil

[TheEAR]

Plywood is best used when curved to make horns in horn loaded speakers.I know an audiophile who built Altec Voice of the Theater speakers and he used Plywood all around.The speakers feature curved plywood pieces to form the woofer horn.The bracing is very extensive.Very nice built.These monsters can play loud with just a few watts.I a bit like the Klipsch Horn.

Now plywood VS MDF,MDF takes the win.A well braced MDF cabinet is more inert then one made ot of plywood.When cabinets resonate the speakers have nasty colorations.Some manage to hide the minute defects quite well by voicing the speakers with care.

And then there is ceramic,marble and concrete mix cabinets!These are ideal(not the weight and cost).

Thiel uses composite conctere bafles,very nice.And a small company called nOrh makes some of the best monitors in the world and uses marble for the cabinets!

I am about to order the nOrh 9.0(main) and 7.0(sourround).All I can tell you I heard these when visiting another audiophile maniac like me.WOW these speakers are amazing.nOrh is the SVS of speakers,its a small company known only to a few audiophiles who makes outstanding quality speakers and sells them direct!

So speakers can be built form many materials the end result will depend on good design and smart cost cuts.

TheEAR(s) Now theears