MDF thickness

[castropine]

This is my first time building a speaker enclosure, however the MDF I have lying around at home is only 6mm thick. I was planning to buy 12mm but I might as well use up the leftover MDF I have.

How would a enclosure made out of 6mm MDF sound different from 12mm? Can I achieve the same sound if I stick the MDF together and make it 6+6=12mm?

[CLS]

For cabs of 'normal' sizes, 6mm is just way too thin.

How big (or I should say small) is your cab?

[tresch]

whoah. 6mm is really thin. I wouldn't even trust that to hold up under its own weight. Unless the MDF where you're from is way stronger than what we have in midwest USA, I wouldn't touch it. I just worked with a little half inch (12mm) and it's bad enough by itself.

If it's strong enough actually stay together, you'll then get problems with the walls of the enclosure resonating depending on the size of each panel. This will come across as spikes in the frequency response. I couldn't tell you how /bad/ they'd be, but if you're making a full range speaker, you're probably going to get some significant "muddiness" or "ringing" from it.

As far as laminating them together, if you have a nice even coat of glue between the two layers, 6+6 would theoretically be STRONGER than a single sheet of 12mm, as the layer of glue in the middle would provide a fairly significant amount of stiffness.

[planet10]

Personally i avoid using MDF for any speaker boxes....

... as tresch says a plywood made from multiple thin layers of MDF will be stronger than a single piece of equivalent thickness.

How big is the box?

dave

[Mario Pankov]

12mm will be not enough for the wall thickness, go with at least 36mm and additional ribs inside. If this is for a smaller fullrange ( smaller than 13cm ), 24mm would be enough. If you want a no-compromise box - asymetricaly curved sides of at least 45mm sandwich made of at least two types of wood.

The speakers I am buidling right now use curved sides and I am buidling them with MDF and plywood sandwich. What I noticed about the MDF is that when stuck, two pieces of 3mm are much stronger than one piece of 6mm. So it should be the same for two pieces of 6mm vs one piece of 12mm. One more advantage - when glued together, the glue forms somekind of a composite with the MDF so you will have two zones with different Fs and properties - this will help you to control box resonanses.

[castropine]

I'm building the enclosure following this plan, for CHR-70.
It's 6.4L, 290x160x190mm.

I was concerned about the resonate problem, but if stiffness does increase if I simply glue them together, might give that a try.

Just another question, for a box this size, is bracing necessary?

[CLS]

6mm is still too thin for that size.

I would at least use double thickness with bracing -- one solid/hard stick (not the MDF) connecting the 2 parallel 290x190 areas should be fine.

If triple thickness is used, then maybe I'll leave it without bracing.

[tresch]

Originally posted by CLS
6mm is still too thin for that size.

I would at least use double thickness with bracing -- one solid/hard stick (not the MDF) connecting the 2 parallel 290x190 areas should be fine.

If triple thickness is used, then maybe I'll leave it without bracing.

What he said!

Perfectionism aside, coming from another new-to-DIYer who just built two sets of CHR-70 speakers as first projects, you're pretty much going to love it no matter what you do.

laminate the 6mm into 12mm sheets and you're basically going to have a better speaker than any off the shelf computer speaker out there. Beyond that it only gets better.

[wxa666]

Originally posted by castropine
This is my first time building a speaker enclosure, however the MDF I have lying around at home is only 6mm thick. I was planning to buy 12mm but I might as well use up the leftover MDF I have.

How would a enclosure made out of 6mm MDF sound different from 12mm? Can I achieve the same sound if I stick the MDF together and make it 6+6=12mm?

It's just a fun speaker, isnt't? If not for the sound, what I doubt, the 6mm MDF would be hard to work with. The corners are very small, to small to apply srews, glue etc. Go for 12mm which is still very thin. 16mm would be better to work with. Regarding the sound, it won't do that much as others like to tell. In this very case the speaker chassis will be the weak link anyhow. Way to small for any serious listening and by far to expensive. It has its chique but that was it. Just my 2cc

by

[Moondog55]

6mm is far too thin but 3 layers of MDF glued together would be fine