PLYWOOD 1/2" or 3/4" FOR CABINET

AriajazzJulio

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Hi all. I know this has been asked thousands of times but I don't feel I've found an answer to it. I'm planning to built a stereo guitar amp with two 6.5" Emminence speakers, they are 20w each (4 ohms). My questios is: should I use 1/2 or 3/4 inch plywood. I've read many times that 3/4" is the industry standard for guitar cabinets but considering the one planned is kind of small (19x13.5x8 inches) I would think 1/5" thick could be enough, maybe I'm wrong and that's what I want to clarify. Here in Ecuador plywood is meassured in milimeters and not inches so the choices for thickmess are 15 and 18 mm. Working with 15 mm makes meassurements more precise and exact whilst using 18 mm complicates this factor.

I know about Baltic Birch Plywood which is not available in this country. In this case I will get the best that I can find. I plan to tolex the cabinet, and as far as I know this can help reduce resonance issues. The cab will be ported with 35mm holes. I know this design is not that easy to obtain good reults. A lot of math and calculation is involved but I want to help these little speakers to have more bottom end. Also will want to know about baffle material and thickness. Some experts say that MDF is better for it since is more robust

I will really appreciate your help and your thougts so I can have a clear idea of what to do and complete this project. I'm getting tired of reading and not getting a definitive approach and decision.

Thanks in advanced.
 

nojazzhere

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Hi all. I know this has been asked thousands of times but I don't feel I've found an answer to it. I'm planning to built a stereo guitar amp with two 6.5" Emminence speakers, they are 20w each (4 ohms). My questios is: should I use 1/2 or 3/4 inch plywood. I've read many times that 3/4" is the industry standard for guitar cabinets but considering the one planned is kind of small (19x13.5x8 inches) I would think 1/5" thick could be enough, maybe I'm wrong and that's what I want to clarify. Here in Ecuador plywood is meassured in milimeters and not inches so the choices for thickmess are 15 and 18 mm. Working with 15 mm makes meassurements more precise and exact whilst using 18 mm complicates this factor.

I know about Baltic Birch Plywood which is not available in this country. In this case I will get the best that I can find. I plan to tolex the cabinet, and as far as I know this can help reduce resonance issues. The cab will be ported with 35mm holes. I know this design is not that easy to obtain good reults. A lot of math and calculation is involved but I want to help these little speakers to have more bottom end. Also will want to know about baffle material and thickness. Some experts say that MDF is better for it since is more robust

I will really appreciate your help and your thougts so I can have a clear idea of what to do and complete this project. I'm getting tired of reading and not getting a definitive approach and decision.

Thanks in advanced.
I agree with @Jon Snell that 1/2" should be adequate. How are you joining the sides? Will there be any internal structure to help stiffen the box? Personally, I'd probably have 3/4"-1" support pieces at each corner anyway.
 

AriajazzJulio

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I agree with @Jon Snell that 1/2" should be adequate. How are you joining the sides? Will there be any internal structure to help stiffen the box? Personally, I'd probably have 3/4"-1" support pieces at each corner anyway.
Yes, I will be using support pieces at corners and front and back panels, probably 3/4". I do not have appropiate machinery to do finger joint, so regular glueing and screws or wooden ferrules will be used. Any thought on baffle material and thickness?
 

old wrench

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For a small cabinet like you've planned 1/2" is adequate as long as you use a good solid method of joining your corners.

I've actually used some plywood that was manufactured in Ecuador and it was good stuff - it had more plies than it's counterpart manufactured in the U.S. - a good product.


edit: you could make it easy on yourself and use the same 1/2" ply for your baffle ;)

.
 

nojazzhere

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Yes, I will be using support pieces at corners and front and back panels, probably 3/4". I do not have appropiate machinery to do finger joint, so regular glueing and screws or wooden ferrules will be used. Any thought on baffle material and thickness?
Like @old wrench said above.....the same 1/2" should be good for baffle.
Just curious.....what is this cabinet for, amp-wise? A 19" wide cab isn't going to give much stereo separation, is it?
My Fishman Loudbox Mini has one 6.5" speaker, plus tweeter, and it sounds pretty darn good.
 

24 track

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you could compromise at 5/8" , 1/2" may be alittle too light unless a small cab , 3/4 too heavey to lug around , so 5/8" may be the ticket
 
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schmee

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I lean toward 3/4" or 5/8". But it depends a lot on how you do the joints etc. A cab needs to withstand the sound with some mass. The weight difference will be negligible.

I'm more worried about the depth of only 8" though.
IME, depth is the biggest factor for tone. Too deep and you have hifi woofy tone. Bass cabs are built deep for a reason, it enhances the lows tremendously.
Too shallow and you have highs and upper mids but lose some nice low mids and low end.
I would go at least 9" deep. 9.5-10 being better.
 

AriajazzJulio

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Ok guys, thank you very much for your replies. Actually I think I can find 16 mm plywood wich is just a bit more than 5/8" as Intubator said. The stereo cab will have an inner plywood separation panel between both speakers and they are angled outwards by a 5 degree angle. This design is inspired on a keyboard amplifier I saw a while ago. I will follow Schemee recomendation of 10" depth. The cab is closed back but I intend to make 35 mm holes on each baffle. Do you think is a good idea?. The speakers are back mounted. Should I fill the inside of the cab with some acoustic material?, I was thinking about 1/2" foam panels.
 

old wrench

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Part of the problem when we think about regular 1/2" plywood here in the States, is that the "1/2 plywood" sold here is quite a bit less than a true 1/2" - it seems like it gets thinner every time I buy it :)

15mm plywood is stout enough, as long as you construct your joints properly.

Construction methods are just as important as construction materials.

Hell, a 3/4" plywood cabinet with flimsy joints will fail just like one using 1/2" if you don't build it properly :)


.
 

AriajazzJulio

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Part of the problem when we think about regular 1/2" plywood here in the States, is that the "1/2 plywood" sold here is quite a bit less than a true 1/2" - it seems like it gets thinner every time I buy it :)

15mm plywood is stout enough, as long as you construct your joints properly.

Construction methods are just as important as construction materials.

Hell, a 3/4" plywood cabinet with flimsy joints will fail just like one using 1/2" if you don't build it properly :)


.
I am aware of that, stiffness and solid construction is a must.
 

Lowerleftcoast

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Can you find wood planks that are not plywood in suitable sizes? The baffle and back should still be plywood.

If you stick with ply I would use 1/2 inch.
Should I fill the inside of the cab with some acoustic material?
Use padding that is intended for the purpose or fiberglass insulation. The wrong material will decrease the internal volume of the cabinet.

Porting a cab can be very exacting. If you decide to port the cab, do your research. Chances are you will want a tube as part of the port. The length x diameter of the tube changes the tuning of the cab. It gets quite involved.
Simplified... you can watch some youtube videos where the cabinet is pointed up. Rice or beans are placed on the cone while a bass frequency is swept while looking at the rice to find the resonate freq of the cab.

Good luck.
 

JL_LI

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15mm is 5/8” and is ideal for 6 1/2” to 8” speakers. Measure twice, cut once and you’ll be OK. Have fun building your cabinet. Be sure to fill in any voids before you cover with Tolex.
 

AriajazzJulio

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Can you find wood planks that are not plywood in suitable sizes? The baffle and back should still be plywood.

If you stick with ply I would use 1/2 inch.

Use padding that is intended for the purpose or fiberglass insulation. The wrong material will decrease the internal volume of the cabinet.

Porting a cab can be very exacting. If you decide to port the cab, do your research. Chances are you will want a tube as part of the port. The length x diameter of the tube changes the tuning of the cab. It gets quite involved.
Simplified... you can watch some youtube videos where the cabinet is pointed up. Rice or beans are placed on the cone while a bass frequency is swept while looking at the rice to find the resonate freq of the cab.

Good luck.
Thanks for your opinion. What about using a 1/2" panel of foam? similar to Auralex but flat, I saw that in a video. And porting the cab with just a hole with no tube?

Most wood available here is not dry enough with the risk of buckling.
 

AriajazzJulio

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THESE are the specs for the speaker. I'm working with them and changing some design details.

The Eminence 6.5" Guitar speaker

Created specifically SKB, this Driver has a surprisingly rich Clarity and punch for its size. It is Perfect For small practice / Bedroom amps and works with effects pedals as a guitar speaker should. The FX dont sound pasted over top of your tone, they sound organically integrated.This little speaker will surprise you with stunning results and sounds larger than it's 6.5" over all diameter.

Materials of Construction

Coil Construction - 1" Copper voice coil
Coil Former - Paper former
Magnet Composition - Ferrite magnet
Core Details - Non-vented core
Basket Materials - Pressed steel basket
Cone Composition - Paper cone
Cone Edge Composition - Paper cone edge
Dust Cap Composition - Zurette dust cap
Over all weight is 2.1 pounds

Mounting Information

Recommended Enclosure
Sealed or Vented
Resonance 96Hz
Usable Frequency Range - 80 Hz - 4.5 kHz
Sensitivity* - 96 dB
Magnet Weight - 12 oz.
Gap Height - 0.31", 7.9 mm
Voice Coil Diameter - 1.", 44 m
The TS parameters are:
Re: 4.01 ohms
Fs: 108 Hz
Qts: .966
Qes: 1.04
Qms: 14.2
Le: .48 mH
Mms: 5.59 g
Vas: .378 cuft
SPL: 96 dB
Physical dimensions of this speaker are:

From the back of the mag to the front of the speaker = 2 7/8"
External diameter edge-to-edge of the basket= 6 9/16"
Speaker hole cut out diameter = 5 9/16" =

This speaker lets dynamic styles Project Clean and full, with lots of body and clarity. It is smooth with high-end definition. Country, Jazz Blues, Rock and even Metal are obtained with stunning results for the size and price. For an 8 ohm load you would need 2 of these and we will combine shipping, please refer to the wiring diagram in the pictures.

CAB
15.5” wide x 10” tall x 8” deep
 

AriajazzJulio

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Hello guys. Thanks a lot for all of your replies, the more information obtained the more precise are my conclusions. There is anothers aspect about the speakers used that I'd like to point out.

This Eminence speaker has a Qts of 0.966. According to some experts is better suited for open back cabinets and infinite applications. Nevertheless, speaker specifications I found while ago (posted above) states that sealed or vented enclosure is recomended. Which way should I go?. On the other hand, these specs recomend a cab size of 15.5" wide x 10" tall x 8" deep. 10 and 8 inches are good for me but 15.5" wide is kind of too much. I was thinking about 10"x10"x8" for each speaker since is a stereo cabinet, it has a separation panel between them so it is basically to enclosures that make a larger one. What do you think?. Which way should I go?
 

Boreas

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Hello guys. Thanks a lot for all of your replies, the more information obtained the more precise are my conclusions. There is anothers aspect about the speakers used that I'd like to point out.

This Eminence speaker has a Qts of 0.966. According to some experts is better suited for open back cabinets and infinite applications. Nevertheless, speaker specifications I found while ago (posted above) states that sealed or vented enclosure is recomended. Which way should I go?. On the other hand, these specs recomend a cab size of 15.5" wide x 10" tall x 8" deep. 10 and 8 inches are good for me but 15.5" wide is kind of too much. I was thinking about 10"x10"x8" for each speaker since is a stereo cabinet, it has a separation panel between them so it is basically to enclosures that make a larger one. What do you think?. Which way should I go?
I don't know much about speaker cabs, but what I have read is that speaker enclosures should not be too symmetrical. I would compromise at something like 12"x10"x8" for each enclosure. And don't forget to figure the dimensional space the divider and insulation will remove. I think I would lean toward a firm insulation on each side of the divider. Or better yet, two thinner dividers separated by sound insulation material to better isolate the chambers.

One advantage of the 15" width dimension for each speaker is additional separation. You could also investigate not centering the speaker in the chamber but shifting it to the outside to increase separation even more. Perhaps move the speakers closer to the edge and put the ports toward the center.
 
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