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Plywood thickness for 15 inch subwoofer
Plywood thickness for 15 inch subwoofer
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Old 21st September 2017, 09:17 PM   #11
chrisb is offline chrisb
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+1 to the bracing.

jmd - I've been working in the commercial cabinet industry for almost 25 yrs, and it should be noted that once you get below the level of certified BB, all bets are off as to quality / rigidity of plywood.
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Old 21st September 2017, 09:55 PM   #12
richardr is offline richardr  United States
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I built one the same size. Use 1" ply but, do it by gluing two 1/2" inch pieces together. The 7/8 and 1" ply tend not to to be straight(warped) and require some serious effort to get straight walls. A T-brace above the woofer works pretty well. The sad part is that even a well braced 1" ply woofer box will vibrate at higher volume as it is just tough to stop. It will be the woofer end that does it. The t-brace works.

Last edited by richardr; 21st September 2017 at 09:56 PM. Reason: english
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Old 21st September 2017, 09:59 PM   #13
straight8s is offline straight8s  Canada
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MDF sucks. I might be over building a closed sub box with double 18mm ply with hardwood bracing. It doesn't take much extra doing while eliminating room for doubt. For a push pull I'd make it mandatory.
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Old 21st September 2017, 10:08 PM   #14
simon7000 is offline simon7000  United States
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Quote:
Originally Posted by j.michael droke View Post
Hi there: Plywood! MDF is snarky stuff to deal with. No advantage to MDF and if it gets any water on it, it swells-up (unless you want to create 1" MDF from 3/4" MDF). Baltic birch plywood, while good material, sells for over a hundred dollars for a 5x5 foot sheet here in my area. ...regards, Michael
I usually pay $40.00 a sheet for the Russian made Baltic birch. Not quite as good as the stuff from Finland. You might want to find out who supplies the local kitchen cabinet makers.

They may have a minimum order of typically $150 and a delivery charge on small orders. But should allow pickup. If you need a pickup truck for a few hours Home Depot often has them.

They also used to carry the Chinese birch plywood. But unfortunately it cost much more than corregated cardboard, which is a bit stronger.
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Old 21st September 2017, 10:12 PM   #15
planet10 is offline planet10  Canada
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Plywood thickness for 15 inch subwoofer
Quote:
Originally Posted by richardr View Post
The sad part is that even a well braced 1" ply woofer box will vibrate at higher volume as it is just tough to stop.
This is were using a push-push pair really helps a lot because you have active reaction force cancelation abd the load on the box is dramatically reduced — well done probably by 90% or so.

Use 2x10 instead of a 12, 2x12 instead of a 15, 2x15 instead of an 18.

dave
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Old 21st September 2017, 10:17 PM   #16
planet10 is offline planet10  Canada
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Plywood thickness for 15 inch subwoofer
Quote:
Originally Posted by simon7000 View Post
I usually pay $40.00 a sheet for the Russian made Baltic birch.
About the same as here, but we quit using it when the quality became hit or miss. We now use sheets sourced from MurphyPly in Oregon. Quality Baltic sourced cores which they put maple surface plies on. 4x8s are about twice as much as the BB, with much higher quality, much less waste and typically better yield from th elarger more convienient size. We try to use 15mm as much as possible but do use 18mm and 12mm when called for.

dave
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Old 21st September 2017, 10:26 PM   #17
chrisb is offline chrisb
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The biggest issues we had with the spotty QC on the Russian BB was on the face veneers - increasing occurrences of large foot-ball patches, smaller unpatched pinhole knots, and mineral stains, etc - all cosmetic. In over several hundred sheets of the 5x5s I only ever had maybe 3 that had delaminations of glue joints, which the vendor immediately replaced.

But yah, the Murphy Multi-ply have a much nicer maple veneer face.
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Old 22nd September 2017, 01:22 AM   #18
wmd916 is offline wmd916  United States
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Originally Posted by planet10 View Post
This is were using a push-push pair really helps a lot because you have active reaction force cancelation abd the load on the box is dramatically reduced — well done probably by 90% or so.

Use 2x10 instead of a 12, 2x12 instead of a 15, 2x15 instead of an 18.

dave
Can you explain what YOU mean by a push-push configuration? Both drivers with frame/magnet inside the enclosure running in phase or is one driver flipped? Forgive me if I'm being naive here. As always I appreciate your time and glad you're seemingly back to good health Dave.

Wes
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Old 22nd September 2017, 01:27 AM   #19
planet10 is offline planet10  Canada
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Plywood thickness for 15 inch subwoofer
Here is a thread on the subject: Force Cancellation: X, Y or Z axis?

And i copy my post from it below.

dave

Quote:
I built a set very similar to what you are describing with 2 CSS SDX10 per box. Performance was outstanding.

Mount the drivers on the side, a 90 turn of the box gives front & back. Side mounting, unless the box is way out from the wall (or way up in the air) is the only arrangement where the 2 woofers will get ~equal boundary loading. As radiation at these frequencies are omni-directional the direction makes little difference in that sense. And a recent FAST build where we let an associate go at that to design a passive XO, ended up with the side mounted woofers XOed up near 450 Hz — mind you much smaller woofers.

The only picture i have is of the push-push nature shown from inside:

Click the image to open in full size.

We built the raw box out of well braced 15mm BB. You could easily pick up both boxes with two hands. Load the drivers in and each box was Good news a 2-man lift (or 1 guy with a strong back). They never got finished as Chris sold them to raise cash while i was in the hospital — the new owner raves over them.

I did a test with a mechanics stethoscope to check box resonances. I turned the system up to uncomfortably loud, then turned off the satellite amps and then added another 10 dB (bass amps were probably haevily clipping). I was able to get the top moving, alll the other panels were quiet. I figures a corian (or similar) top would fix that.

Good news — CSS is back in business under new ownership with SDX10s appearing again new years end, and i am already working on getting a new set for V2.

I did 2 plans for these, ended up building the smaller ones, i figure being sealed that i could EQ them to suit…sim-wise the larger box is closer to ideal Q.

http://www.planet10-hifi.com/downloa...oof-230712.pdf

3d visuallization of the bigger box:

Click the image to open in full size.
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Old 23rd September 2017, 12:15 AM   #20
phivates is online now phivates  United States
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Who'da thought AR knew what they were doing with the AR-9. So long ago. Luck?
Re plywood: just buy void free 3/4 fir decking grade. Unless you insist on paying too much. We really don't need to import plywood to the USA; we need to be pushy consumers and seek out the good stuff made here. HD and Lowes won't be any help on this. You need a real wood products vendor.

Last edited by phivates; 23rd September 2017 at 12:32 AM.
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