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Message started by franksmith on 11/21/05 at 12:41:23

Title: MDF wood or birch plywood ?
Post by franksmith on 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,

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 11/21/05 at 12:51:10

Ho,

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


Title: Re: MDF wood or birch plywood ?
Post by RFZ_Quest on 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

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 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 ?


Title: Re: MDF wood or birch plywood ?
Post by franksmith on 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 ?


Title: Re: MDF wood or birch plywood ?
Post by Doorman on 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!)

Title: Re: MDF wood or birch plywood ?
Post by RFZ_Quest on 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.

Title: Re: MDF wood or birch plywood ?
Post by Rap on 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 ;) 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

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 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 :(

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 ? :)

Title: Re: MDF wood or birch plywood ?
Post by Doorman on 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!

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 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.


Title: Re: MDF wood or birch plywood ?
Post by serenechaos on 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  :)  

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/01/05 at 12:07:08

Robert :

Do you have some pictures of your project ?

Sylvain

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 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 ?

Title: Re: MDF wood or birch plywood ?
Post by Doorman on 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.

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/09/05 at 02:04:57

Thanks Doorman.

BTW, I received the parts today from decware.

The driver phase plug is very well made. The damping is nice also but I was a little bit disapointed to get them in their original white color.

Everywhere we see black fe206 on the website and mine aren't.

I should be able to built the cabinets in the next few weeks but I will have to call for some missing parts for the passive (atl tuning) since I only got the external surrounding.

I'll try to grap some pictures while building them.

Title: Re: MDF wood or birch plywood ?
Post by Corey on 12/09/05 at 02:15:07

FrankSmith,

I don't understand what you mean by white color. What is white? The driver cone?

Corey

Title: Re: MDF wood or birch plywood ?
Post by Corey on 12/09/05 at 02:17:15

Yes, the phase plug is well made!  ;)

Corey

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/09/05 at 02:31:40

On the pictures of the drivers in the website, the cones are all black but mine are to original white color from fostex.

Maybe I would had need to specify ... I don't know.

Another question, for the passive I only received 4 large surround, nothing else with the kit.

Is that the only parts supplied with the alt tunning passives ? how do I built the two domes ?  

I didn't receive the explanation how to built them in the kit so it's pretty hard to figure and on the website there is only a sheet for the original tunning passive assembly.

Title: Re: MDF wood or birch plywood ?
Post by Corey on 12/09/05 at 02:57:07

Okay,

Give me a minute and I will take a picture of the passive and tell you how to build it.

Each passive has 4 parts to it:

-large surround which glues to the wood cabinet.
-small surround which glues to the large surround.
-saucer dome which faces out and is glued to the small surround.
-flat dust cap which faces inward and is glued to the inside of the saucer dome.

The driver cone should be black. Deckert applies a special black titanium/carbon ink to it and I believe this is primarily for cosmetics.

BTW, the phase plug is a 15/16" socket.

Corey

Title: Re: MDF wood or birch plywood ?
Post by Corey on 12/09/05 at 03:23:15

Here are 2 pics of the passive. Notice how the large surround is in "standard" form meaning the surround roll faces outward.
The smaller surround is "inverted" meaning the roll faces inward, like it does on the Fostex driver:





Here is another pic from the front showing how the dome passive protrudes out from the cabinet and its shape loads the air into a hemispherical shape or radial pattern. It is like a ball sticking out into the room:





Hope this helps.

Corey


Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/09/05 at 19:03:16

Ok so I only got the biggers surround, not the other parts.

There seem to be 2 way of building the "alt tunning" passives, some have the smaller dome way outside of the cabinet than others.

Maybe if I had all the parts in my hand I will figure it all but is there am official pdf on the website about how to built the alternative tunning ?






Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/09/05 at 19:05:43



Look at how theses passive are way out of the cabinet.

Title: Re: MDF wood or birch plywood ?
Post by Microbe Man on 12/10/05 at 03:55:14

FS,

There is only one way to build the passives. I removed the last picture of the inside dust cap because it was confusing.

Yes, the dome or ball should be sticking out like that. The last picture is a close up of that.

Once you get your other parts you will understand and we will go from there.

Take care,

Corey

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/10/05 at 19:14:24

Yesturday we sended an email to decware, I will wait for their answer.

So far the drivers have been test (brand new from the box) in a pair of bigfunhorn with very good result after 30min to 1hr of playing time.

Today I've intall them in some "burn-in" box until the cabinets are built.




Title: Re: MDF wood or birch plywood ?
Post by Microbe Man on 12/10/05 at 20:03:38

FS,

Actually those drivers look pretty sharp with the silver phase guide and white cone.

My drivers are from the early production of the HDT's and the socket and cone are painted black. This matches well with dark veneers like walnut or rosewood but I bet your drivers would look swell in maple.

Actually I bet black oak would suit your drivers best, that would look sharp.

Take care,

Corey

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/10/05 at 20:52:32

I was aiming for an red wood like an african acajou.



I may have access to 2mm venneer.

For the mounting of the driver, should I mount them flush ?


Title: Re: MDF wood or birch plywood ?
Post by Microbe Man on 12/11/05 at 23:23:35

Frank,

No, flush mounting isn't required.

Take care,

Corey

Title: Re: MDF wood or birch plywood ?
Post by Jason_S on 12/11/05 at 23:41:07

I imagine the reason the drivers aren't coated is becuase either Decware is too busy to coat them, or they might be out of coating.

Corey, I believe that the first prototypes of the alt passives that Steve built, had both surrounds facing the same way.  In talking to Bob, I think he found it was easier to glue them opposite so thats the way they are now.  I don't think it matters how they are assembled, if you can do it the other way, great.

FWIW, my drivers came coated, but the phase plug is silver.

Man I need to get myself motivated and finish my cabinates.

Jason

Title: Re: MDF wood or birch plywood ?
Post by franksmith on 12/12/05 at 03:45:56

The explanation for the coating was that the news fe206 are now melting while trying to coat them.

If it's the case I may buy some old fe206 and send them for a coating.


Title: Re: MDF wood or birch plywood ?
Post by Jason_S on 12/12/05 at 04:08:23

Are they being Gel waxed now instead of the magic black titanium carbon whatzit?  Or it that still optional?

Jason

Title: Re: MDF wood or birch plywood ?
Post by Microbe Man on 12/12/05 at 04:19:20

Wow, that is not the best news for me. I had best make sure I don't mess up these drivers because a white driver in a walnut cabinet just wouldn't look nearly as good.



Take care,

Corey

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