Time to build a box: Material?

[PaulB]

OK, so I "dissasembled" my P5 gloatspeakers... time to start planning the new cabs. For you veteran DIYers, is there a significant difference between MDF/particleboard (what the originals were)? I was originally planning on solid oak, but frankly I don't know that these justify that kind of expense... after all they aren't JBLs ;)

Also... any tips on fabricating grilles and stretch the cloth? Not much experience with that.

Thanks for any tips or links!

PaulB

[Zilch]

MDF is the material of choice.

Solid hardwood like the oak you suggest would have resonance issues.

http://audioheritage.org/vbulletin/showthread.php?t=7941

[jim campbell]

i had very good luck with a product called plum(b) creek board which was supposed to be much more dense than mdf.i dont know where or how to get this stuff but im sure a few phone calls would do it.the only drawback was the 10 cu ft cabs were incredibly heavy.i lined them with accoustic foam and braced them well and they are still in use twenty some years later

[Gary L]

Skip the idea of solid Oak for sure! Oak has Tanic Acid in it and is not good for interior spaces or speaker cones or foams.
If you use Oak plywood then deffinately seal the inside wood with either poly or a good shelac.

MDF is the material of choice these days but wear a dust mask when cutting it. I would shy away from particle board simply because we never know what glues were used to bind it or what effect it might have on the components if there is some strange chemicle.

Good idea when building with MDF to glue and screw and pre drill all holes with a countersink bit. Standard Yellow Carpenters glue works great but I hate Gorilla glue even if it does hold great!

Gary

[scott fitlin]

You could do what Widget did for me! 3/4 mdf, bonded to 3/4 Baltic Birch!

Heavy, and dense, like concrete, NO rattles, buzzes, or other extraneous cabinet distortions!

WILL definitely last a lifetime.

[MJC]

Like everyone else has said, mdf is the best choice. You can always cover the outside with wood veneer. I bought a 4x8 sheet of Ash veneer(1/32" thick) to cover my main L212s and sub1500 boxes and then stained them with Sherwin-Williams Black Stain concentrate.

[macaroonie]

Sorry chaps but that stuff will A kill you B drive you crazy C sound crummy,
Do youirself a favour and buy the best Quality ply you can get. In the grand scheme of things the cost of your sheet material is almost nothing compared to the cost of your compnents, If you do it my way you are doing it way better than factory. 13 ply baltic at least and lots of bracing . I am a shopfitter and cabientmaker trust me.

[Baron030]

Macaroonie is absolutely right on all counts!

A. MDF will kill you. So, please read the following and take all of the necessary safety precautions:
MDF can be dangerous to use if the correct safety precautions are not taken. MDF contains a substance called urea formaldehyde, which may be released from the material through cutting and sanding. Urea formaldehyde may cause irritation to the eyes and lungs. Proper ventilation is required when using it and facemasks are needed when sanding or cutting MDF with machinery. The dust produced when machining MDF is very dangerous. Masks and goggles should always be worn at all times. Due to the fact that MDF contains a great deal of glue the cutting edges of your tools will blunt very quickly. MDF can be fixed together with screws and nails but the material may split if care is not taken. If you are screwing, the screws should not be any further than 25mm in from the edge. When using screws always use pilot holes. Urea formaldehyde is always being slowly released from the surface of MDF. When painting it is good idea to coat the whole of the product in order to seal in the urea formaldehyde. Wax and oil finishes may be used as finishes but they are less effective at sealing in the urea formaldehyde

B. MDF will drive you crazy. Believe me, when I say this, MDF is miserable to work with. It’s like working with drywall. :banghead:
Baltic Birch plywood on the other hand, is an absolute joy to work with. :applaud:

C. MDF sounds crummy. Personally, I would think that an MDF enclosure would fall apart over time, particularly, if it was moved around a lot. As an experiment, try dropping a piece of MDF and a piece of Baltic Birch plywood on the floor a few times and see which holds it shape longer. Since, JBL components have such long life span. Ask yourself this, which material will hold up as long as the drivers will?

As one last final tip, regardless of which material you use, it is a good idea to seal the wood on inside of the enclosure as well as on the out side. This reduces the amount of expansion and contraction of the wood with humidity changes. In the Chicago area, humidity can be equal a tropical rain forest during the summer and be as dry as a desert during winter. So, seasonal changes in humidity can cause wood to warp and glue joints to loosen unless the wood is sealed.
Baron030

[Mr. Widget]

A. MDF will kill you. You can get hospital grade MDF... it has a low toxicity glue so that it won't out gas toxic fumes in your home or while working it.



B. MDF will drive you crazy.Working MDF does suck from a dust collection standpoint, but on the positive side it is very consistent and it doesn't splinter or chip... I have had edges blow out when working with birch ply... it isn't terrible, but can be annoying at times especially in mitered corners.



C. MDF sounds crummy. I agree that MDF is structurally only slightly better than a damp sponge, but when properly braced it is a very good speaker building material. As Scott mentioned my favorite construction technique is to build an MDF box that is braced with birch ply internal bracing and covered in birch plywood. This construction forms a constrained layer type of cabinet where the sogginess of the MDF dampens resonance while the very rigid birch plywood adds a structural integrity to the cabinet that significantly reduces the lossy nature of the MDF.


Widget

[Ian Mackenzie]

I have seen locally made multi ply laminate with a lead/mix filler that is used to great effect for industrial sound protection. Again its very heavy.

Ian

[Gary L]

Lots of great info above!

I used MDF to build my 19 clones and learned about the fine dust produced while cutting it. I never knew about the Toxic chemicles in it!

The idea of plywood is a good one but how in the world do you get past the obvious problems in a small shop?

1. Useing good ply should negate the need to veneer if you can 45 the seams. How do we glue up large box 45 cabinets in a small shop where glue jigs are a big problem?
Seems a shame to pay big bucks for ply and still have to pay big bucks for veneers to cover over glue residues that won't take stains.
It is not like you can sand off any glue smudges from the thin veneers on ply and I try very hard to keep glues where they need to be and off the surfaces but we all know it gets where it should not.

Gary

[macaroonie]

You can buy router cutters that will give you an interlocking mitre. In the factory they use V groover cutters that don't quite penetrate the veneeer. The process is called Mitrefold but we cant readily do this. The cutter set gives you a locking joint that is very strong and consistent and if you buy pre veneered ply ( your sheet supplier should do any type of ply with ANY type of veneer as a to order item. Order it with your veneer of choice and a compensating layer on the B side. Search the web for veneer info ) and are careful with your cutting and jigging you will actually get a way better than factory result.
Use 2" masking tape on the surface where any tool penetration occurs and do not attempt to cut too much at once. Do test cuts. Measure Measure and then cut. If your material is tearing or your tool is screaming then you are going too hard. Good luck.

FYI [URL="http://www.trendmachinery.co.uk/profinder/display.asp?PartNo=10%2F99X1%2F2TC"]

[Gary L]

If the router cutter you are refering to is the Lock Miter, I have it!
Have not really experimented with it yet but it sure looks like a shaper would work better with this bitt.

I have a few projects on the burner for this winter so will have to play around to get the best joint for my boxes.

I have some issues with the MDF I used previously and this thread just added to them.

Added to my wish list will be a shop three times the size, full of great tools and someone to pay the heat and electric bills!:D

Thanks

Gary

[macaroonie]

you do not need a big shop all you need is patience and best practice. be careful and you will get there.

[Gary L]

you do not need a big shop all you need is patience and best practice. be careful and you will get there.

I Did check the link! The one I have is Miter Lock Jointer and not sure if this is the one you mean. Also not sure if this is good for 7 or 9 layer plywoods.

Gary