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Material Selection
Material Selection
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Old 23rd April 2019, 05:25 AM   #1
McFluffels is offline McFluffels  Australia
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Default Material Selection

Hello everyone, (sorry about the essay!)
I will cut right to the chase, I have only ever built one speaker two 3" full range shielded drivers in a sealed cabinet small enough to fit on my desktop amp when i was in high school. I originally built it out of pine mainly because it was the only thing my school shop had access to, I have since out-grown it and I am looking to build a new pair.

From all of the research I have done it seams the universal opinion is that Baltic Birch plywood is the material of choice when it comes to building speaker cabinets.
I have recently found a local timber re-seller that stocks Baltic Birch plywood. I submited a request for a estimate of one sheet measuring 2400mm x 1200mm x 19mm.
I plan on building a two way cabinet using the B&C 6NDL38 6.5" Woofer and the B&C DE35 tweeter.
The timber re-seller has two different types of ply with a significant difference price.
Also of note is that I am going to have the cabinets cut out on a cnc router because it is cheaper than the upfront cost of tools/equipment to do it myself and I want to recess the woofer and it is a awkward shape.
Option 1:
B/BB FSC Birch Plywood for $215
Pics:
Face: Brirch Ply FSC Face.jpg - Google Drive
Edge:Birch Ply FSC Edge.jpg - Google Drive

Option 2:
B/B Birch Plywood with Acacia core for $125
Face:Birch Acacia Ply Face.jpg - Google Drive
Edge:https://drive.google.com/open?id=1AM...3scja8RbE8MAHU

I am leaning towards the Birch with the Acacia core because the face looks to be of far better quality, and the price.

Now the actual question.
Does the Birch with a Acacia core preform any worse than the regular Birch, and if so is it very noticeable?
Thanks in advance for the help.
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Old 23rd April 2019, 05:57 AM   #2
planet10 is offline planet10  Canada
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Material Selection
What about the core? Which is stiffer? How many plies in each?

dave
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Old 23rd April 2019, 02:47 PM   #3
McFluffels is offline McFluffels  Australia
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Sorry it has taken so long to reply.
-Does the stiffer acacia laminate have an effect on sound?

-The birch plywood with the acacia core is about 1.4x stiffer compared to the regular birch sheet. Seller said it is commonly used as a indoor floor substrate. The other birch is used to make luxury kitchen cabinets.

-The birch with acacia core is 6 thick plys of acacia with a thin birch face. The other is 9 thinner plys of birch only.
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Old 23rd April 2019, 03:33 PM   #4
Zampotech is offline Zampotech  Russian Federation
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Plywood is a sonorous material. Parasitic resonances will appear
For acoustic boxes probably need to take a material with low Q, such as MDF. Or marble (not joke)

Last edited by Zampotech; 23rd April 2019 at 03:39 PM.
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Old 24th April 2019, 01:11 AM   #5
planet10 is offline planet10  Canada
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Material Selection
Quote:
For acoustic boxes probably need to take a material with low Q, such as MDF
As far as i am concerned MDF is a last choice material for building speakers.

dave
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Old 24th April 2019, 01:15 AM   #6
PRR is offline PRR  United States
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Would help to have the edges side-by-side in the thread rather than some Drive.

To my eye, I'd pay $5 more for the more-ply product; but NOT $100 more. I rather doubt any but the most experienced golden-ears would know the difference in residential speakers. (Road-PA speakers do need tough wood because roadie-abuse opens up the plywood and it can buzz.)

The mimosa-core has a visible void-- this is a cheaper construction with a cheap wood. I had no idea mimosa could be structural, though I use Luan and that's also cheap wood.
Attached Images
File Type: jpg BirchAcacia.jpg (108.3 KB, 172 views)
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Old 24th April 2019, 02:26 AM   #7
planet10 is offline planet10  Canada
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Material Selection
That is a pretty low ply count. The 18mm stuff we use has 15 plies. Use whichever material is stiffer… that pushes any potential resonances up high enuff that they will not likely be excited. And any piotential resonances will be hi-Q which means they need a steady sustained input in a very narrow bandwidth, something that rarely happens with misic.

dave
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Old 24th April 2019, 05:42 AM   #8
scottjoplin is offline scottjoplin  Wales
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What plywood is that? I thought baltic birch was 13 plies for 18mm
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Old 24th April 2019, 07:38 AM   #9
Tromperie is offline Tromperie  Australia
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'Some' say MDF is to be avoided at all costs, except the larger 'some' use it in most speakers made on the 'planet', all the while giving reasons, akin to the use of unicorn poo as an aphrodisiac, why their choice is so much better.

I have used MDF several times and cannot hear a deficiency. Why not use it and use the balance of the budget for some very nice veneer?

BTW, how much will those drivers cost to get to OZ? There are many drivers, just as good if not better, to be had here at a reasonable cost.
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Old 24th April 2019, 08:54 AM   #10
McFluffels is offline McFluffels  Australia
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Tromperie,
Yeah I just got past the research phase to the budgeting. With current currency conversion
it would run about $940. That includes
- 2x 6NDL38 Woofers
- 2x DE35 Tweeters
- 2x Dayton Audio 4.5K 2-way crossovers
- 1x WF60PA full range amp with wifi (I plan on streaming from s media server)
- Terminals, Mounting hardware, and Batting
Still a bit rich for my blood do you have any suggestions on alternatives?
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