Baltic Birch/Particle board sandwich.

[dogscanskate]

My diy speaker project is slowly coming along as there are so many choices and compromises that have to be made. Sooo, CLD is out of the question as I don't have the skills nor patience to make it work.

That's why I'm thinking of sandwiching particle board between 2 sheets of BB, something in the order of 12 mm BB (exterior), 9 mm particle board, 6 mm BB (interior). On the front baffle I plan to add a 6 mm thickness of BB (glued to the 12 mm BB exterior) which avoids having to rebate the BB to accommodate the drivers. I may also end up veneering the cabinets but we'll see...

For enclosure stuffing, it looks like Ultra Touch (cotton/denim) would be a nice choice but I'm not sure about thickness or density. The design is a 2 way aperiodic (closed box though) design based on the Dynaco A 25 (World Designs WD 25T, building plans available on their site).

Drivers: SEAS A 26RE4 (10" mid/bass)
SEAS T29CF001-06 (excel tweeter)

The system will be "active" and I'm considering a Marchand analog XO. SS amp on the mid/bass and tube amp on the highs. ARC D130 and VT 50.

Since I'm likely to use BB instead of MDF, I'm wondering if more bracing is essential as the only negative I've read about BB is its flexibility. So the front baffle should come out to 33 mm (almost 1.5") and the rest of the panels to about 27 mm (few hairs more than 1")...

I'd appreciate any advice you guys have to share as to the glue, stuffing, bracing, exterior finish... and no screws are used for this project (except to secure the drivers).

Thanks for your help.

[MJL21193]

How big is the box? What are the dimensions (W x D x H)?
Your effort is almost certainly better spent effectively bracing the box, rather than making the panels excessively thick.

[dogscanskate]

Internal dimensions are approximately 935 mm H x 250 mm W x 210 mm D. The plan already has 3 horizontal braces and 1 vertical brace.

[badman]

My diy speaker project is slowly coming along as there are so many choices and compromises that have to be made. Sooo, CLD is out of the question as I don't have the skills nor patience to make it work.

That's why I'm thinking of sandwiching particle board between 2 sheets of BB, something in the order of 12 mm BB (exterior), 9 mm particle board, 6 mm BB (interior). On the front baffle I plan to add a 6 mm thickness of BB (glued to the 12 mm BB exterior) which avoids having to rebate the BB to accommodate the drivers. I may also end up veneering the cabinets but we'll see...

For enclosure stuffing, it looks like Ultra Touch (cotton/denim) would be a nice choice but I'm not sure about thickness or density. The design is a 2 way aperiodic (closed box though) design based on the Dynaco A 25 (World Designs WD 25T, building plans available on their site).


I'd go about 2" thick on 3 of the walls, excluding the bottom, baffle, and one side. Keep the densitity about what you find in the ultratouch as sold.


Drivers: SEAS A 26RE4 (10" mid/bass)
SEAS T29CF001-06 (excel tweeter)

The system will be "active" and I'm considering a Marchand analog XO. SS amp on the mid/bass and tube amp on the highs. ARC D130 and VT 50.

Since I'm likely to use BB instead of MDF, I'm wondering if more bracing is essential as the only negative I've read about BB is its flexibility. So the front baffle should come out to 33 mm (almost 1.5") and the rest of the panels to about 27 mm (few hairs more than 1")...

With the wall thickness you're doing it is improved over a normal 18mm wall. I like to overbrace, but it isn't strictly necessary, particularly with your layered wall construction. Stock bracing scheme may be sufficient. Always focus effort on the biggest area without a brace, and try to couple opposite walls to each other.


I'd appreciate any advice you guys have to share as to the glue, stuffing, bracing, exterior finish... and no screws are used for this project (except to secure the drivers).

Thanks for your help.

Use good jointing technique with your laminated material. Rabbeted joints are a good mix of strength and ease. Be sure to coat all cut edges with woodglue, and coat the inside of the cabinet with something. Particle board will be problematic with moisture, so you must be very sure to seal it well.

[planet10]

Originally Posted by dogscanskate

For enclosure stuffing, it looks like Ultra Touch (cotton/denim) would be a nice choice but I'm not sure about thickness or density. The design is a 2 way aperiodic (closed box though) design based on the Dynaco A 25 (World Designs WD 25T, building plans available on their site).

A bale of 3.5" is probably your best bet.

Do you know that Scott & i did a TL for this WD kit?

Classic TL Revisted

Since I'm likely to use BB instead of MDF, I'm wondering if more bracing is essential as the only negative I've read about BB is its flexibility.

The reason to use BB is that it is stiffer & better damped than MDF. It is always hard to overdo the bracing.

Discussion on what materials to build speakers out of

(what is missing from that thread is the post where John has an epiphany and relizes what i'm describing)

New search is truly better Discussion arising from Geddes loudspeaker

dave

[MJL21193]

I would build the entire box out of 3/4" BB plywood (or MDF if you like) and have 3 full panel holey braces that run from top to bottom - 2 from front to back, cutting the panels into three spans. The other (actually 3 separate pieces) from side to side:

117.PNG

The braces can be 1/2" thick.

[MJL21193]

Originally Posted by planet10

(what is missing from that thread is the post where John has an epiphany and relizes what i'm describing)

New search is truly better Discussion arising from Geddes loudspeaker

dave

Good snag Dave. I forgot about that "discussion"

[planet10]

Originally Posted by MJL21193

What John shows is very good.

Keep this detail in mind:

A brace should divide a panel into subpanels such that the aspect ratio of the subpanels are higher than the original panel and such that the aspect ratios of the subpanels are not equal.

dave

[dogscanskate]

Thanks so much for the input guys, I still have much to learn. I've been reading up on speakers and have read many threads here on the matter but still have a ways to go. John's plan seems to be quite similar to the original plans of this kit so it seems these guys knew what they were doing.

I've also been reading up on an old BBC research into loudspeakers that many of you are aware of but I include for those who have never had a chance to sift through it.


Here it is:
http://downloads.bbc.co.uk/rd/pubs/reports/1977-03.pdf


So, I'll read up on the links provided and keep badgering you with questions.

Thanks so much for the help!

[dogscanskate]

Originally Posted by planet10

A bale of 3.5" is probably your best bet.

Do you know that Scott & i did a TL for this WD kit?

Classic TL Revisted



The reason to use BB is that it is stiffer & better damped than MDF. It is always hard to overdo the bracing.

Discussion on what materials to build speakers out of

(what is missing from that thread is the post where John has an epiphany and relizes what i'm describing)

New search is truly better Discussion arising from Geddes loudspeaker

dave

Well Dave, I realize you know about Peter's (Comeau) mdf/particle board sandwich for the 2nd version of the WD 25. I just thought that sandwiching particle board between 2 sheets of BB may yield better results even though more costly.

I'm also looking up your Classic TL based on that design. Thanks for the links!