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MDF wood or birch plywood ? (Read 9382 times)
franksmith
Ex Member



MDF wood or birch plywood ?
11/21/05 at 12:41:23
 
Hi,

I'm new here. I borrowed a paire of hdt "proto" from someone to try them at home. There are using audio nirvana, cheap passive radiator from a local electronic store, cheap wire, nothing is tune, no damping anywhere, mdf 1/2 ...

Anyway, I really like their sound but there are some place for improvment like some wood resonnance on the big front piece and they do not go under 45 hz.

But even so, I really like the mids and tight bass then can do (I own two pair of electrostatic).

I'm looking to start a hdt project using the fe206e from decware and I want to alternative tuning to go deeper than 45hz.

Anyone ever tried them in birch plywood or other ply ?

I'm not a big fan of MDF (found it a little dead and resonnant)

What would be the difference acording to your experience with mdf vs plywood ?

Thanks a lot,
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« Last Edit: 11/21/05 at 12:42:46 by franksmith »  
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franksmith
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Re: MDF wood or birch plywood ?
Reply #1 - 11/21/05 at 12:51:10
 
Ho,

Forgot, If i go with the birch plywood. What thickness should I use ?

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RFZ_Quest
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Re: MDF wood or birch plywood ?
Reply #2 - 11/21/05 at 13:49:30
 
Hello Franksmith,

The Baltic Birch that I get is 11/16ths inch thick. This is the ultimate material to use for cabinet structures and far superior to MDF!  This is quite expensive but you get what you pay for. Quality should always be the #1 priority in your diy projects. Baltic birch is free from voids with 13 layer composition versus 5 layer for standard plywood. Very strong and uniform construction. The edges are very attractive and solid which can be easily painted or covered if exposed. I will not go back to using MDF again as long as I can get this material.

My internal HDT structures are all constructed from Baltic birch with the outer cabinet shell constructed of cherry faced plywood. All of my edging is finished with exotic solid hardwood trim.

Good luck.

Paul
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franksmith
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Re: MDF wood or birch plywood ?
Reply #3 - 11/21/05 at 14:54:58
 
Thanks for the answer Paul.

I will go with the birch plywood. Are you using only glue for the cabinet or glue+screw ?

With a well tuned hdt using the gel coated fe206 from decware, how low could I expect the bass to go ?

I would like to go a little bit lower than 41hz, would it be possible ?

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franksmith
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Re: MDF wood or birch plywood ?
Reply #4 - 11/21/05 at 15:04:22
 
I can have birch plywood only in 5/8 or 3/4 (13 ply) in 4X8 format

Or I can have cherry plywood in 11/16 (13 ply) in 4X8.

IT's about the same price, should I go with an all cherry plywood design ?

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Doorman
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Re: MDF wood or birch plywood ?
Reply #5 - 11/21/05 at 22:10:09
 
In these parts (Western Canada), Baltic birch comes in 5'x5' sheets. Regular/shop grade etc.birch ply, comes in 4'x8' sheets. Baltic birch has more laminations, and no voids. I prefer it to mdf for speakers( can't handle that mdf dust!)
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RFZ_Quest
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Re: MDF wood or birch plywood ?
Reply #6 - 11/21/05 at 23:08:47
 
Hey Franksmith,

If you can get 13 ply Baltic birch at 3/4 inch, GET IT and USE it! Most of these diy projects call for 3/4 " material although adjusting for the 11/16" material is no problem.

The answer is quite simple as it is a matter of using the Baltic birch to build the entire cabinet for superior strength and performance ...(or) giving a little bit as I did to create the outer (visible) shell from pre-veneered cherry plywood so that the finish was already in place. Note: when going this direction, there is NO room for mistakes as you are working with zero margin of recovery if any of the panels are scarred during the fabrication and assembly process. ABSOLUTELY use the high strength Baltic birch for all internal structural components as a minimum!

Actually, If I was to do it again, I would opt for the Baltic birch for the entire structure and finish with a nice veneer.
Either way, these material choices are quite costly by the sheet BUT ABSOLUTELY WORTH IT for the final result.

My HDT cabinets conform to the Mark II configuration, which are 2-way using the ribbon high frequency driver. Mine are built with a change of creative cosmetics to make them unique but they are essentially the same thing.

I am not familiar with the single driver details but there are many here that can lend you good advice.

With the dado channels provided for the panel assembly, all that you need is good carpenters wood glue. If you wanted to use the pocket jig assembly technique, it would make production time faster without the need for alot of clamps but this is completely optional. If you choose to use ordinary wood screws, make sure that you use an appropriate step bit to compensate for the exact length of the shank. This ensures a proper snug fit without ANY splitting or bulging of the cabinet material.

Anyway, I will try to get some detailed photos of the internal assembly stages posted for you to examine.

Have fun.

Paul.
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Rap
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Re: MDF wood or birch plywood ?
Reply #7 - 11/22/05 at 15:25:35
 
Master builder Ziggy stated that the most economical use of baltic (and only audible) would be to use it for the inside structures of the HDT´s just using mdf for the rest. So thats what I did Wink saves a mint as baltic costs 4xmore than mdf but If I had the cash Id go all Baltic for the "no damn MDF dust " reason. I used no screws (mainly cos mdf and screws are a pain in the ass) but I doubt there is a very noticeble sonic difference
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franksmith
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Re: MDF wood or birch plywood ?
Reply #8 - 11/24/05 at 17:02:20
 
Thanks again for the answers.

I have to say that the protos I have home are quite resonnant, specialy in the mids area. They are made of 3/4 mdf. Just knocking on them and you got the picture.

Maybe with a good veneer but I'm not a big fan of mdf (tend to sound dead) and you need to install veneer inside and outside to get rid of this sound.

Anyway, The parts as been ordered including the modified fe206e. I will go with the baltic birch 3/4 13 ply.

Unfortunatly I wont be able to get a pair of gel waxed driver from decware Sad

They are not available anymore because of a change in the fostex speaker fabrication or something like this.

Anyone as more clues about this ? I would had like to get a pair of gel waxed. Anyone here as a old pair for sale ? Smiley
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Doorman
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Re: MDF wood or birch plywood ?
Reply #9 - 11/24/05 at 21:55:02
 
There are many variants on cone treatment, including "puzzle-coat", "Dammar" varnish, etc. Perhaps one of these alternatives would also be good? I'm gonna try one of 'em on my 108ez's, being non- reversible is the downside!
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franksmith
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Re: MDF wood or birch plywood ?
Reply #10 - 11/25/05 at 23:28:00
 
I would had like to test the gel wax but give me some feedback of your tests.

I also found on the internet something about using weldbond as doper.

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serenechaos
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Re: MDF wood or birch plywood ?
Reply #11 - 11/30/05 at 23:54:28
 
I built mine using 3/4" baltic birch, inside & out.  
The edges are 3/4" oak.  
The inside & outside finished dimensions are the same as the 'print, but I cut the bb outer panels narrow, then added 3/4 x 3/4 oak strips to the outer edges, to get the finished width, then clamped & glued it all together, & routed the edges.  
Came out real nice, with solid oak edges seeming more able to take bumps & dings, & no laminations showing.  
Robert  :)
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franksmith
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Re: MDF wood or birch plywood ?
Reply #12 - 12/01/05 at 12:07:08
 
Robert :

Do you have some pictures of your project ?

Sylvain
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franksmith
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Re: MDF wood or birch plywood ?
Reply #13 - 12/06/05 at 19:22:11
 
I have another question.

I choose the birch ply for my project but I have to choose if I will only use glue or glue/screws for the construction.

What do you think is the best ?
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Doorman
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Re: MDF wood or birch plywood ?
Reply #14 - 12/06/05 at 21:37:11
 
Once the glue sets up, (assuming it's a good wood glue, like Weldbond, etc) the joint will be stronger than the wood. Screws may ease the initial assembly, but are usually not needed.
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