Building THAM15 in 3/4" Plywood - diyAudio
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Old 2nd December 2014, 05:49 PM   #1
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Default Building THAM15 in 3/4" Plywood

Hello everyone, I searched around to see if someone has built this cabs on a 3/4" plywood but with no luck I have found any. I am getting ready to built this cab for knowledge and testing (with Dayton Audio PA385S-8) but I am planing on using a 3/4" Plywood from my local Lowes store (just for testing and learning purpose, I don't want to invest on a $80 sheet right now and maybe screw something up) and wondering if the change in thickness of the panels and braces, have a major change in the cab performance? It's a .75" is about 1.05mm bigger than the suggested 18mm panel thickness.

NOTE: I was thinking of enlarging the sides (panel 6), the upper front (panel 9), the lower front (panel 10) and the top/bottom (panel 7), to compensate a bit.

Questions:
1st - Using a 3/4" Plywood from my local Lowes store and wondering if the change in thickness of the panels and braces, have a major change in the cab performance?

2nd - Should I just go with the original external measurements and don't worry about the internal volume?

3rd - Should I enlarge outer panels to compensate a bit and leave the internal panels and braces alone or should I do something to the inside panels as well?

4th - Is the Baltic Birch plywood actually 18mm or a bit smaller?

Panels to enlarge:
#6 - 646.10 x 552.10
#7 - 253 x 464
#9 - 295.05 x 464
#10 - 95.55 x 464


Thanks in advance for the help?

Last edited by Fresh101; 2nd December 2014 at 06:10 PM. Reason: added size to panels to enlarge
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Old 3rd December 2014, 12:43 AM   #2
tb46 is offline tb46  United States
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Hi Fresh101,

Is your plywood really 3/4"/.750"? It usually ends up being 23/32"/.719" nowadays. Looking at it from prior experience w/ Hornresp simulations of this enclosure:

To question 1: No.

To question 2: I would. The driver makes much more of a difference than this minor wall thickness change.

To question 3: See #2.

To question 4: Yes, 18mm or 0.709" (haven't measured any in a while).

Regards,
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Old 3rd December 2014, 01:45 AM   #3
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Quote:
Originally Posted by tb46 View Post
Hi Fresh101,

Is your plywood really 3/4"/.750"?

Regards,
Hello TB46 and thank you for your response. I just checked on Lowes site and the plywood I was planing on using it actual thickness is .71" = 18.034mm which is really close. Thanks
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Old 3rd December 2014, 01:49 AM   #4
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I am getting ready to buy some clamps to start building but I just thought on how people hold down the inside panels while the glue cure, if clamps don't reach pass 3.75" from the edge? Thanks
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Old 3rd December 2014, 03:01 AM   #5
sine143 is offline sine143  United States
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I use screws... sometimes Brad nails. Whatever suites you really.
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Old 3rd December 2014, 03:26 AM   #6
wg_ski is offline wg_ski  United States
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Weight it. Lay the opposite side panel across everything (don't glue), and stack a bunch of 45 pound barbell plates on it for 24 hours. Evenly, of course. When that cures, flip it over, glue the last panel, and weight the other side. Use a few brads or screws to keep the corners in alignment, if necessary. If it isn't CNC-cut, it will usually be a little "twisted". A 16th of an inch or so is no big deal.
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Old 3rd December 2014, 04:25 AM   #7
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Got it, thanks for the advice.
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Old 3rd December 2014, 09:13 PM   #8
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I'd suggest the accuracy of your cuts is going to be a bigger issue than the thickness of ply
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Old 4th December 2014, 12:14 AM   #9
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Quote:
Originally Posted by bitSmasher View Post
I'd suggest the accuracy of your cuts is going to be a bigger issue than the thickness of ply
What do you mean by this, I am extremely a*al about preciseness on cuts. I like to double and triple check on markings and cutting and then recheck after cutting of the exact measurement, I always aim to cut slight bigger (1/16") and start shaving to the exact size . So I don't think the accuracy will be a problem.

Last edited by Fresh101; 4th December 2014 at 12:20 AM.
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Old 4th December 2014, 01:30 AM   #10
evanc is offline evanc  United States
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I say "measure twice...cut three times"
Sorry I had to, Evan
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