# Why MDF?



## pascione (Jan 26, 2009)

OK DIY speaker builders. I'm looking around at speaker designs and can't help but wonder why so many of you choose MDF? I love woodworking and want to create great sound that looks like a piece of furniture. I couldn't sleep at night if I went to Veneer over MDF, why make it myself if I do that? Is there an audible sound difference?

Feedback is welcome.


----------



## bonehead848 (Jan 21, 2007)

No sound difference, many people build with many different materials. MDF is mostly used just because its incredibly easy to work with and paints really well. Im sure some others can chime in on the best wood types.


----------



## tonyvdb (Sep 5, 2007)

MDF is extremely ridged and makes for a solid cabinet. It is also fairly inexpensive.


----------



## Anthony (Oct 5, 2006)

MDF is also very stable for boxes. You don't have to account for wood movement in the design. A sealed box won't warp or crack with MDF like it would with solid wood.

Some also argue its damping properties, but those are debatable versus solid wood or baltic birch plywood. It is very heavy for it's volume, which helps.

Also, it's cheap and a good substrate for veneer. So you can tell everyone you made that speaker out of solid tiger maple


----------



## DrWho (Sep 27, 2006)

Hmmm, I've always found MDF to be much harder to work with and hard on tools too. It's also very easy to damage - both moisture and dropping onto corners. An MDF speaker isn't gonna last you 30 years and they're real pains to move too. MDF will also have a greater tendancy to sag with very heavy drivers. Of course there are ways to work around everything, but having done both many times, I'm done with MDF.
_Posted via Mobile Device_


----------



## Anthony (Oct 5, 2006)

Well, some of the best speakers in the business as still made with MDF. I believe Thiel makes their speakers with CNC cut and laminated layers of MDF. Very heavy, but also very well braced. And with the right veneer and/or finish can last a very long time. Baltic birch is also very good (and widely used).

As for being hard on tools, I have three levels of tool quality in my shop: hardwood, softwood/plywood, and MDF/particle board. With router bits, the new ones are only used on hardwood until they dull, then they are downgraded (and then eventually thrown away).

Now all that being said, my current project is going to be a hardwood speaker, but it's open baffle, so wood movement won't be a problem.


----------



## ktaillon (Apr 3, 2007)

MDF has a lot of pro's but don't forget the con's. I try not to use it because of what it does to my eyes and nose. That stuff is mean compaired to plywood's and real woods.

I rather use more plywood and better bracing than MDF.


----------



## Anthony (Oct 5, 2006)

I'll actually second that. I installed a full dust collection and air filter system in my shop just to deal with that (and I still prefer to rout MDF outside). I still use it, but that is a major downside.

Miner's have black-lung, I guess speaker builders have brown-lung


----------



## JCD (Apr 20, 2006)

Here are some of the reasons that I've heard people say they use MDF:
1) Fairly inert
2) Very consistent (e.g., no voids)
3) Less prone to warping/expanding/contracting (of course, it assumes you don't spill water on untreated MDF)
4) Inexpensive
5) Pretty easy to work with -- and I think it's easier than ply as it's less likely to chip when making cuts/routing/etc.

The downside is it's very heavy (which is part of the reason it's good for speakers) and can be damaged easily, particularly corners, edges, etc.


----------



## pascione (Jan 26, 2009)

Wow,

Thanks for all the feedback. I couldn't help but chuckle; all the feedback was with regard to the woodworking properties of MDF, no surprises there. I was hoping there was no audible rational for going with MDF because I want to make furniture quality speakers from wood. As a DYI'er the cost savings is not a big deal and solid oak is quite substantial. So, wood it will be. Now the quest for designs; I'm starting with the surrounds for a 7.1 system, any suggestions?


----------



## JCD (Apr 20, 2006)

My points #1 and #2 would have implications towards the sound quality.


Edit: here's a link that goes into some of the issues.


----------



## JCD (Apr 20, 2006)

Oh, and we'd need a budget and goal design before making a suggestion for a DIY project. As you can imagine, the swing a lot in price/performance/size.


----------



## pascione (Jan 26, 2009)

Thanks for the link Jacen. Maybe I will opt for veneer over MDF. I'll sleep on it. As for the speaker budget that’s a tough one. I didn't want to cheep out and I'm wondering how much speaker you really need for the back 4. My thinking is the big bucks go into the front and center speakers based on my 5.1 performance. Not much comes out of the back in a 5.1 system, I thought I'd start with a simple 2 way bookshelf design so I don't scare the wife off with an intrusive monster in every corner of the room; we'll save that surprise for the fronts. So to answer your question, $200-300 a pair might get me there. FYI the room is 14 x 24 and I’ll be driving them with either the Marantz SR5003, 90 x 7 watts, or SR6003, 100 x 7 watts.


----------



## DrWho (Sep 27, 2006)

JCD said:


> My points #1 and #2 would have implications towards the sound quality.
> 
> 
> Edit: here's a link that goes into some of the issues.


There were a lot of comments about the wood being used affecting the timbre of the speaker based on the density of the wood, etc etc...the problem with that reasoning is the enclosure shouldn't make any sound in the first place.

I can accept that different materials might require different bracing and construction techniques, but two cabinets "braced to the same stiffness" will sound the same....and there is really no physical limitation preventing any sane material from working to the same levels of performance (except maybe the wallet).

So all that to say...using a bad design practice to claim a certain material superior to another is ultimately meaningless.

There also seems to be a lot of fixing of problems that are unknown, unquantified, or just plain don't exist.

To put things into perspective, how many people here can walk into a room and hear what construction materials were used? Or do you have to look first?


----------



## bobgpsr (Apr 20, 2006)

IMHO quality 3/4" 13 ply baltic birch plywood is superior -- less weight, stronger and stiffer. Does cost more, but much easier to work with than horribly dusty MDF.


----------



## WmAx (Jan 26, 2008)

People here have covered very well the practical reason for MDF(cost, consistency and easy to paint).

Personally, I despise MDF because of the horrid dust and it's weak structure and high weight that gains you nothing in itself that is substantial. I use MDF only when I am painting a surface now.

The high grade 13 ply birch is stronger/stiffer and weighs less and it lacks the horrid MDF dust. You can more easily achieve a specific stiffness per area using less bracing, and with far less weight, than a MDF cabinet.

If you want a true very low resonance cabinet, you have to do more than just use a good base material and moderate bracing, anyway. Standard construction method for cabinets used by most DIYers and Hi-Fi manufacturers will not give you a low resonance cabinet; you will have to go to more extreme methods to effect a low output cabinet. I can state this with high confidence based on my own research and experiments/measurements. I find it takes a surprising amount of effort to substantially reduce cabinet talk; at least surprising to most people compared to what they presume will effect low cabinet talk.

-Chris


----------



## JCD (Apr 20, 2006)

_Plywood will vibrate more than MDF and allow more midrange energy to bleed out of the cabinet through the walls, which is bad for the sound of the speakers. Hence the suggestion to use more bracing and dampening materials. _

Not going to argue with anyone else out there, this is just somethign I came across..
I guess I'm just playing Devil's Advocate. :devil:


----------



## robbo266317 (Sep 22, 2008)

pascione said:


> Wow,
> 
> Thanks for all the feedback. I couldn't help but chuckle; all the feedback was with regard to the woodworking properties of MDF, no surprises there. I was hoping there was no audible rational for going with MDF because I want to make furniture quality speakers from wood. As a DYI'er the cost savings is not a big deal and solid oak is quite substantial. So, wood it will be. Now the quest for designs; I'm starting with the surrounds for a 7.1 system, any suggestions?


Hi Pascione,

Why MDF? 

I guess the answer is "Why not?"

I think the first few posts nailed it. 1) Cost, 2) Availabilty & 3)Machinability.
The best thing about DIY is 1) you can save money, 2) you can work with what you have & 3) It's whatever you are comfortable working with.

You can make speakers from any materials if you want to & have the neccessary skills, it's up to you!
All have different properties, therefore you need to design around their strengths or weaknesses.

The best way to find out is to try it. (& post lot's of pictures on the way so everyone can learn. Be it good or bad. In fact, more so if it's bad! So we don't make the same mistake...)

I'm looking forward to your speaker build project & rest assured whichever path you choose you will be supported fully by all here. :T

cheers,
robbo.


----------



## bobgpsr (Apr 20, 2006)

JCD said:


> _Plywood will vibrate more than MDF and allow more midrange energy to bleed out of the cabinet through the walls, which is bad for the sound of the speakers. Hence the suggestion to use more bracing and dampening materials. _
> 
> Not going to argue with anyone else out there, this is just somethign I came across..
> I guess I'm just playing Devil's Advocate. :devil:


Thus when you DIY you can add a lot of internal window braces. No more than 6" span without an internal brace. The resulting resonance of the sidewalls is raised in frequency to the point that they do not get activated. Going to this type of extreme is rarely done for a commercial product -- but DIYers can obsess. :hyper: :sweat:


----------



## WmAx (Jan 26, 2008)

bobgpsr said:


> Thus when you DIY you can add a lot of internal window braces. No more than 6" span without an internal brace. The resulting resonance of the sidewalls is raised in frequency to the point that they do not get activated. Going to this type of extreme is rarely done for a commercial product -- but DIYers can obsess. :hyper: :sweat:


This is still going to leave the resonant points within the passband unless you are talking about only a woofer cabinet section. A 6" span matrix brace on all axises on 3/4" MDF would place the first resonant panel mode in the 400-550 Hz range, I expect. The typical window braced enclosure with braces every 8-10" typically has it's first resonant panel vibration roughly in the 180-300Hz range.

On top of the resonance, even more troublesome, regular cabinets will have a wide band of high vibration through the entire audible bandwidth. One needs to not only address the huge resonant spikes, but also the high over all vibration level of the cabinet panels.

Of course, I presume the point is a no-hold-barred reference grade speaker. For a HT speaker, or a speaker for less than critical listening, I don't suppose cabinet talk needs to taken as a very high priority.

-Chris


----------



## WmAx (Jan 26, 2008)

JCD said:


> _Plywood will vibrate more than MDF and allow more midrange energy to bleed out of the cabinet through the walls, which is bad for the sound of the speakers. Hence the suggestion to use more bracing and dampening materials. _
> 
> Not going to argue with anyone else out there, this is just somethign I came across..
> I guess I'm just playing Devil's Advocate. :devil:


I think one needs to qualify the statement you quoted. Sure, regular AC grade softwood ply is not a great choice. But we are talking about 13 ply void free hardwood birch plywood in this thread; a different animal.

-Chris


----------



## pascione (Jan 26, 2009)

Thanks for all the good tips folks. I've never gotten denser than 9 ply of any type. I'll look into that!


----------

