Why MDF so Bad???

Hi everyone,
I've been reading left and right about how bad MDF seems to be for equipement racks. Everyone seems to agree that MDF shelves will color the music badly. The only thing I wonder is why do many speaker companies use MDF in their speakers?

Also, does MDF sound bad in every thickness? Did someone try to use 1 inch thick MDF shelves?

I'm very curious about MDF so I'm getting a woodsmith to build a 5 shelf equipement rack made of 1 inch thick MDF (only 1 inch thick MDF will be used for the whole unit). The shelves will be fixed to the frame. The whole rack will be assembled using high strength glue only. No nails nor screws will be used. The rack will be veneered with 1/28" thick mahogany wood (no paper backing)... Also, the back of the rack will be reinforced by MDF braces... The overall rack will be as rigid as possible.

One more thing, the rack will sit on the same kind of spike Verity Audio uses on their Parsifal encores (I guess I want the rack construction to be as close to a speaker cabinet as possible)...

I'm getting this rack made as an experiment, not as my definitive rack.

Any opinions as to what I should expect from this rack (sonic qualities)?

I was also thinking to use some sound absorbing material under each shelves and on the inside of the sidewalls to try lowering sound reflection (am I off the track here?)...

One last question, any thoughts as to how I could improve this rack (please don't recommend to throw the rack out the window and get a brand name rack)?

If anyone is interested, I will be able to post some pics when the rack is ready...

Your input is greatly appreciated.

Thanks ahead
your experiment is very interesting & I believe that you may be pleasantly surprised by the results. I used a similar rack arrangement for many years & have always liked it. Not sure where your perception that MDF is undesirable came from, but I disagree with that conclusion based upon my own experience. I don't think that you'll need to treat the shelving at all. My shelves weren't even that thick: closer to 5/8" is all that mine were. And the whole thing was assembled from pieces in a Sauder Furniture kit; fastened with steel screws & the shelves sit on adjustable side pegs that plug into a column of holes such that the shelving heights are adjustable. Quite solid & rigid, it doesn't even have spikes which (I'm guessing) may not be very effective for this type of high mass rack anyway. Rather it has casters which are fantastic for rolling away from the wall & accessing the back of equipment for cabling changes or tweaks, but spikes could be installed in place of the casters (I have the spikes on hand, but I love the casters for convenience). It also had smoked glass doors which looked great, but I eventually removed them because I figured that it sounded a little better without them resonating, at least that was my perception. If you're interested in trying this rack it's now available cheap; it is shippable. I only replaced it because it has 7 shelves & I need 10 for my larger system now. It's double wide & even has compartment storage for records or accessories.
So I think that you'll have no problems with your new rack. You might find for certain pieces of equipment that audiophile shelving such as Black Diamond, Zoethecus, Symposium, Neuance, etc. placed atop the MDF shelves still enhances performance. Pods or cones placed between the MDF rack shelf & the audiophile equipment shelf sometimes enhances or even degrades sonics, or has no perceptible effect at all, so experimentation is required. Same applies for cones, footers, etc. placed between the components & the MDF shelf or the audiophile shelf when used. The whole thing responds quite well to these kinds of tweaks. My new larger rack is also made of wood, which I find much more attractive & WAF-friendly than black steel etc. Good luck with your project!
Of course wood, in my book, is MUCH nicer to the eye than the proverbial metal rods, pipes, shafts etc... MDF is a mixed bag of goods, not a priori bad; the thicker IMO the better.

About the rack/shelves: (Not being a specialist, take my comments w/ a grain of salt...)

I think the positive effects that Bob refers to are, that you may have the whole rack (shelves included) being vulnerable to less frequencies on the vertical plane. The rigidity of the rack would restrict vibration on the horizontal plane -- albeit its height looks like it would make it more vulnerable to resonances there.

OTOH, the wood mass may be "friendly" to low-frequency --higher amplitude level resonance. This is important, I think, and can only be addressed at each shelf-to-component level, by either DAMPING (i.e. find s/thing that turns some of the vibrational energy into s/thing else say, heat) or TUNING each component (using cones, pucks, etc that alter the resonant frequency of the component-rack system).

Strange though it may sound, I get better (subjective) results when resonant frequencies are higher than lower -- probably due to the lower amplitude of higher frequencies even though they play well within the critical audible spectrum (lower mid-range...). Whatever.

As Bob implies (I think) start out with components directly on the beautiful wooden rack, maybe putting sources/pre closer to the bottom (less prone to vertical movement) just for starters. Then change around. Take notes. Then play around with devices between component & shelf. If you can, try out a damping device such as Neuance shelf: sit the component on a Neuance, couple the Neuance to your shelf with s/thing rigid (cones?). Jadem6 has been successful(and so have I, copying his epxeriment) using bubble wrap b/ween Neuance and other shelf.

Input on sound & pics appreciated! Cheers
An all wood rack can be both a thing of beauty and sonically excellent in my experience. I would stick to using 2 x 2's or "mega duty" dowel rods ( rails ) for the frame and risers and then use suspended shelves resting across the support rails. Stick with wood that is lightweight but offers a high degree of internal damping when it comes to shelves. Added mass ( the thicker you go, the more mass you have ) is noticeably poorer sounding when it comes to shelving in my experience. This definitely hurts "prat" and bass definition.

Another factor in such a design is that the shelves should NOT be a stressed member of the frame ( if at all possible ). In other words, the rack should stand on its' own in rock solid shape without the shelves being in place. You also want to keep the rack open ( no closed sides or back ) as this allows far greater ventilation and will affect room acoustics the least. Otherwise, you've got a large reflective surface to deal with. If you want to put the equipment into an enclosed rack, make sure that you have adequate airflow around the amps / other heat generating components and get the rack out of the room. Mounting it into a nearby closet, etc.. would be a good choice. I think that Dekay is doing something like that. This should also help to reduce the amount of airborne vibrations that the equipment has to deal with too.

I went from a "home brew" rack of this nature to a very heavy commercially built rack in one of my systems. The commercially built rack used two sheets of .75" MDF sandwiched together for each shelf. These 1.5" shelves were then coated with some type of poly for cosmetics / protection by the manufacturer. The difference in sonics between these two racks was astounding. In effect, it was one of the worst mistakes i had ever made but it did teach me a BIG lesson i.e. bigger is not always better, things that cost more are not always better and things that you don't think have that much effect on the sound really do.

Learn from our mistakes and do some digging in the archives both here and at AA. It's a lot cheaper that way and you'll probably end up with better performance. I think that you'll find that most people that have tinkered with multiple racks and have greater experience in this area are shying away from what you are thinking about having built. If you look at a rack as more a piece of your system in terms of tuning & resonances rather than being a piece of furniture that you can stack your equipment on, you'll probably have a better idea of the why's and how's of what works best. Sean
Just a comment about MDF in speaker boxes: It's used so much because it's readily available, cheap, easily machined, assembled, and veneered, and has moderately good internal damping. That said, there are VASTLY better materials for cabinet construction, and the best ones are virtually NEVER used because the cost is so high (not just the materials costs, but the cost to the manufacturer of the learning curve that is required to use them properly). So MDF is probably here to stay, limited as it is.

Sean, interesting report on the thick MDF rack. It makes me wonder whether really thick shelves, say 4" to 6", would be better or worse. The stiffness goes up a lot faster than the mass. It may be that 1.5" MDF just isn't enough, especially for heavy components.
Oh, I forgot! I'm also getting some 2 inch thick maple shelves (they are actually made of one piece of maple, like the mapleshade). I guess the maple shelves will go on top the the MDF shelves and I will be using some cones or points to separate the maple shelves from the mdf base shelves...

In this rack, the MDF shelves are only used as a bracing for the rack and as a support to the maple shelves... The back of the rack will be fully opened...

The only thing I am worried about is reflection. Since the sidewalls are closed, I will probably end up with some sound reflection... I was thinking of putting the rack between the speakers but I have pair of Verity audio Fidelios which has rear firing woofers (I have no other place to put the rack)...

Sean (and everybody else for that matter), do you thinks I'm better putting the rack directly in the middle of the 2 speakers or leaving the rack a bit behind the speakers...

Worse comes to worse, the rack will become a nice plant table in my office :-)

thanks again
do you think I'm better putting the rack directly in the middle of the 2 speakers or leaving the rack a bit behind the speakers...
I would think that the rack placed somewhat behind the speakers is the more typical approach, but with the rear firing woofers you might find it works better otherwise. However when placed directly between speakers, staging may be degraded.
Karls: The tests that i've seen on speaker cabinets shows that going from .75" to 1.5" does reduce resonance and ringing, but not by what one would think. When one gets up to 2.25" to 3", the differences really come into play. As such, your idea about "super thick" shelves may have some validity but i'm not about to try it out myself : ) Personally, i've had much better luck with relatively low mass yet rigid wood that offers good internal damping. The shelves on the other "double thick" rack weighed something like 23 lbs apiece whereas my current shelves clock in at about 4 - 5 lbs each. The other rack also had the shelves acting as part of the support structure whereas these shelves are free-floating. I think that these are the two major differences in what i'm hearing / experiencing.

Lgregior: I basically agree with what Bob had to say. If you can get the rack behind the speakers, that would work much better than having it on the same plane. If you can get the rack far enough back so that the rear of both speakers is visible when looking from the side with no interference from the rack, you should be pretty good in terms of soundstage, imaging, etc... As far as the woofers pushing air / vibrating all of the gear situated behind them, that may be another story. Moving the rack to another part of the country might reduce this, but the cables would have to be awfully long : ) Sean
Hello, I do not have a answer to your question, I have my own similar delimia. I too am in the process of buidling a rack using 1 1/8 MDF for shelves. It will be open on all sides (supported only at the corners) I also have 1" granite slabs that are to be placed on each shelf. Is this a good idea, are cones needed between the equipment and the granite for any benifets?
Thanks for any feedback.
Lgregoir, I agree with Bob and Sean. I would not want my rack, or anything else, located within the soundstage (between and behind the speakers). So I would place the rack against the back wall at a minimum (acoustic difusion may help here?).

I built a rack with which I am quite pleased: The open framework is veneered plywood and oak. The shelves, which sit on points (cone set screws at four corners) are IKEA Lak shelves. This is a recipe posted by Caterham1700 a few months ago. These shelves are attractive black finish, light, stiff, damped, and cost $10 each. Search the archives for that thread.

As to the floor coupling, do you have a wood frame floor or a concrete slab?

I have a maple floor...
Try listening to the shelf and the equipment with a stethoscope. Many shelves, especially MDF, pick up and amplify the 230Hz to 350Hz range, and depending on thickness, also "boom" around 60-100Hz.

The former is from the particles themselves talking- inside the material, and that is what cones avoid touching many of.

The latter is the entire middle of the shelf going up and down, and you either straddle that motion with cones or brace the shelf or lay that hunk of maple right on the MDF, so they damp each other for that trampoline motion.

There are other solutions of course, but those are the two modes of vibration in a shelf, assuming the frame is rigid. A perfect shelf would dissapte all sounds coming into it, and that is achieved, or approached, by looking at the various acoustic impedances of all the materials involved.

Acoustic impedance must decrease as you go deeper into the material- that is how one makes sound "go away"- via no reflections. Check out this link- the Java Applet in the middle of the page.


It shows how the % reflection changes with impedance mismatches- for ultrasonics, but completely applicable to audible sounds.

Green Mountain Audio
MDF is the most boring, lifless material i have used. I have made many racks, cabinets, shelves out of many different materials. I love working with wood. I make all my furniture. I would like nothing more than to make a beautiful custom wood rack that performs as well as it looks. I have used MDF shelves with several different footers and spikes. I have filled the wood columns with lead shot and sand. I have used granite, marble, glass, corian, sand boxes, bladders, and maple. For best DIY results for me was maple. I do not mean to offend anyone with my opinions. If you have not tried comparing a Neauance board on a rack or a Sistrum rack to a well made wood rack then you are missing much in performance that will never be realized until a comparison is made. I believe both Neauance and Sistrum have a 30 day trial. IMO, these products are as important as your gear.
I have found that both Sistrum and Neauance work best spiked to the froor as opposed to sitting on a shelf.
You can never know what can be gained or lost without a comparison. My post is to help and not critize based on my never ending search for racks that perform and not degrade.
I hope all find what works best for them as i have. I find no value in opinions based without comparison or experiance.
Bob Bundus, please do not take offence from my post. I have nothing but high regards for you and your contributions.
Brulee, have you tried using any of these materials for speaker cabinets? I agree that mdf sounds boring, and yet have used it for speaker boxes (double laminated).

Royj, good idea to use a stethoscope. That is much cheaper than an accelerometer, preamp and headphones.
I'm considering maple shelves for a wooden cabinet. I assume the grain should run horizontally. Has anyone tried a verical grain such as a butcher block?
Hi Bruce et al thanks for your valuable input.
I fully agree with the "posting our experiences" philosophy.
Zargon: from what I've read (I have not tried it myself) the long grain should run horizontally for best results with maple vs. the vertical grain butcherblock. The Mapleshade people also agree with that approach FWIW.

Both Roy's & Bruce's comments above are very interesting & in fact are applicable & valuable info. regarding my latest rack issues. I've recently observed that when changing my equipment from the old veneered MDF all wood cabinet to the new cherry veneered (+ ? wood, I don't know what kind of wood is inside there) shelved Target rack (which has steel tube framing) that the initial results weren't quite as desired. I much perferred the sound of the older higher-mass cabinet. Many of the previous tweaks that I'd 'perfected' no longer do the job on the new rack, & in fact I've determined that the Vibrapods topped by Black Diamond shelves topped by brass or titanium cones are now actually making matters worse.
So to experiment, I am going to get a Neuance shelf & a Mapleshade shelf + probably some of their other cones & IsoBlock footers etc. Last night I placed mini tennis balls under the preamp, which helped to restore the now-thin midbass, but hasn't yet fixed up the low bass back to what is was previously; I'm going to try some superballs tonight instead. Also the highs aren't as scintillating as they were previously, so I still have a lot of work left to do. Fortunately at least the CDP still works prety well on a Zoethecus Z-slab, with Vibrapods underneath it & Nordost titanium Plusar Points above.
If all else fails then I'll either go back to my old cabinet (a last choice for space limitation reasons only) or I may look for someone to build me something similar to my old cabinet, but with more shelf space. Bruce I don't know where you're located but it sounds like you might be the perfect man for the job, if you're willing?
Try using very dense fiber board instead of medium dense fiber board. I'm not sure about the name of this material, but it's used in making kitchen counter tops. You can get it at Home Depot with white formica laminated on both sides, and in a variety of sizes from 2x4 to 4x8, and a variety of thickness from 3/8 to 3/4 inch. This board will not resonate like MDF. It sounds like hitting a rock with your hand. This stuff is hard to work with, however. You have to drill pilot holes for all screws or nails. The sonic results make it worth while. I plan on using this dense fiber board in the construction of a sub woofer that goes down to 12Hz. I got the plans for this cabinet from TacT audio which uses 4 ten inch drivers. I hope that the room doesn't fall down around me. Wish me luck.
thanks for the suggestion Les: I believe that material is called HDF, for high density fiberboard
High and low density fiberboard sound harsh!
If you want naturally musical sound and good looks use solid maple. Musical instruments are made of this wood. Have you heard a violin ever made from HDF ? That should tell you something.
Violins are made of solid wood to provide their own beautiful unique overtones. The purpose of speakers is to provide NO ADDED OVTERTONES, but rather to reproduce sound as recorded and NOTHING ELSE. HDF does not sound harsh; it sounds like hitting a rock with your hand. This means that no extra resonance is added. A violin made out of HDF would sound dead which is bad for violins, but great for speaker cabinets.
Every rule has its notable exception, this is a fact that confuses the rigid. At least 2 top success manufacturers use solid wood and no MDF in their speakers and the results are spectacular!. SONUS FABER and SHUN MOOK with their BELLA VOCE speaker.
The Sonus Faber Mahler Speaker made with Brazillian Rosewood is beautiful. There is no question about that. Some people with lots of money and good taste prefer speakers made with pure wood. If solid wood is thick enough, it could approach the sonic advantage of HIGH DENSITY (not medium density) FIBER. The point was the pure science sonic comparison between HDF and solid wood. HDF is the winner even if it is cheap and ugly.
MDF is a high profit material. That is why it is used....
Just like anything mass produced, there are so many levels odf distribution, speakers need to be made as inexpensive as possible...
I have to agree with verastarr......BECAUSE IT IS CHEAP AND EASY TO MACHINE. Oh..... and the bottom line.....