Speaker cabinet construction

Jim Palenscar · Post by **Jim Palenscar** » 14 Mar 2003 4:52 pm

In the past I've used mdf and 13 ply apple-birch for speaker cabinets. I recently weighed an unloaded small (18"x 18"x 12") 15" speaker cabinet of 3/4"mdf and it weighed 35#! I'm aware that some cabinet makers use 1/2" mdf vs. 3/4" mdf for cabinets and say that it works well. Frank "Tone-to-the Bone" Carter was talking about rumors of exceptional tone qualities of pine over mdf, etc. I'd like to build another set of 15" cabinets as small and light as possible and am aware of the common rule of thumb of 2 1/2- 3 cu ft for a 15" speaker for tone. Unfortunately my current design gives me about 1 1/2 cu.ft. and I'm commited to not going larger. I've had some discussions with Terry "Mr.Physics" Downs (thanks for the help Terry) and wondered if anyone out there has experimented with some of these variables and has anything to offer in the way of comments? Thanks in advance~~ Jim

jim milewski · Post by **jim milewski** » 14 Mar 2003 9:31 pm

Jim, Duane Marrs makes cabinets with 1/4" plywood, with lots of bracing, I saw them and lifted one, very light, the cabinets have styrofoam in them I believe, I upgraded to a 1501 in my Twin and used 3/8" strandboard for the baffle board, cause I'm cheap and thats what was kicking around, but it sounds great, I think if a speaker cabinet is made from light and thin stuff, but braced and glued so as not to give unwanted vibrations with low notes, I think they would actually sound better than the thicker stuff, like light acoustic guitars that really ring opposed to the heavier guitars, (thick top Gibsons) etc., I'm thinking about modifying my Session 500 cabinet with 1/4" plywood and see what the weight reduction will bring it down to, I think particle board is to heavy for something that has to be moved around.

Jim Palenscar · Post by **Jim Palenscar** » 15 Mar 2003 2:43 pm

I wonder if the amount of bracing required using 1/4" stock negates the weight advantage?

Terry Downs · Post by **Terry Downs** » 15 Mar 2003 3:26 pm

Jim,
I was a pleasure to meet with you at the convention. Have you thought about using a router to remove pockets of material? Now, bracing is often used to reduce standing waves as much as a structural component. It would take some work, but routing out pockets in your wood can serve as well for standing wave supression as well as weight reduction.

Regards,
Terry

Jim Palenscar · Post by **Jim Palenscar** » 15 Mar 2003 3:30 pm

Always thinkin, aren't you Terry? Good idea~ thanks for the reply.

Paul Graupp · Post by **Paul Graupp** » 17 Mar 2003 3:12 pm

Jim: When I used to build Texas Sound cabinets, I'll always felt compelled to use datoed 3/4" wood for ridgidity and strength.

At first I used Birch ply but came accross some walnut wood and made several cabinets out of that. Bud Carter who uses these walnut cabinets occasionally, says they are much more MELLOW than the birch ply units I had sent him earlier. Both units used the same speaker configurations and power ratings but still the difference in solid wood, especially a hardwood, seems to be very noticable.

In fact, another steeler locally who uses these cabinets found the solid walnut to be "Too Mellow" for his tone requirements. Again, same speakers, power ratings and size.
With speakers and wiring, these 400 watt units weighed in at 32 lbs.

Regards, Paul

Jody Carver · Post by **Jody Carver** » 17 Mar 2003 6:58 pm

Leo Fender used 3/4" marine plywood lock jointed cabinets on all MusicMan amps ditto on the baffle board mounted with "T"nuts.

Built like a Sherman tank.

Jim Palenscar · Post by **Jim Palenscar** » 17 Mar 2003 7:11 pm

Thanks Paul- interesting about the effect of different woods on tone. Did you use solid walnut or walnut ply?
Jody~I remember seeing that when I was recovering an old Vibrasonic in the early 70's~ will check into the pine info more thoroughly~~ thanks again~ Jim[This message was edited by Jim Palenscar on 17 March 2003 at 07:15 PM.]

Paul Graupp · Post by **Paul Graupp** » 17 Mar 2003 7:27 pm

Jim: It was solid walnut I used. My cabinet maker had a close friend who died and when he was cleaning up his shop, he found this old 3/4 walnut. He thought it would be an interesting experiment and I got the wood for free so it was a nice trade all the way around. The finish is a really nice plus for the cabinets as well especially if you're going to use them in house and not on the road.

Hey, Jody !! Nice to be in the same thread with you for a change.

Regards, Paul

Regards, Paul[This message was edited by Paul Graupp on 17 March 2003 at 07:29 PM.]

Jody Carver · Post by **Jody Carver** » 17 Mar 2003 9:25 pm

I have been looking for you Paul,,where ya
been?? Lets hear more from you. Good to see you. Hows Caleb?? tell him I told Casey he likes her picture with the missing tooth.She said,poppy why did you show everyone that funny picture of me?

[This message was edited by Jody Carver on 17 March 2003 at 09:27 PM.]

David L. Donald · Post by **David L. Donald** » 18 Mar 2003 2:16 am

For the low frequencies, the more rigid the less "pumping" of the cabinet.
And provided the interior volume and / or portings are well matched for the speakers frequency curve it will give a more balanced sound.
This said, sometimes accurate isn't the sweetest to your ears.
The routing and bracing to break up standing waves inside the cabinet are also good. The combination can make it more rigid and still less negatively resonant.
It is always a fight between rigidity and lightness.
The routing can lower weight, but also cause more "pumping". With the braces it can restore some of the rigidity, while also adding other internal angles to break up the standing waves.

James Quackenbush · Post by **James Quackenbush** » 18 Mar 2003 6:03 am

Experimenting with different wood for cabinets, I have found that using aged, dry, Pine, like the old Fenders, and also going to a floating baffle board (attached on the sides only) allows the cabinet to be a big part in the sound...The cabinet now resonates and is an integral part of the overall sound of the speaker...3/8 birch baffle is the thickest I will use to still have the resonating properties...The speaker and the steel itself will give you the "highs" you need, and the cabinet aids in giving you the "body" of the tone that you need...The combination is very rich indeed .. VERY tightly glued joints is a must..I also dovetail all the corner joints for strength, and it looks good too !!...Jim

Jim Palenscar · Post by **Jim Palenscar** » 18 Mar 2003 7:46 am

Thanks for the replies. Jim- when you say birch are you referring to ply or solid? And 3/8" for the baffle alone then use 5/8"-3/4" pine (again solid/ply?) for the cabinet? I've been thinking of using a 1/4 open back- Gerry Walker says that's tougher on the speaker voice coil than an enclosed/ported cabinet. Thoughts?

Paul Graupp · Post by **Paul Graupp** » 18 Mar 2003 7:55 am

There is another factor involving standing waves that had a different approach altogeather in my cabinets. With a single speaker the pattern become a simplex one but using multiple speakers as I did, the wave pattern takes on a complex structure. Since no two speakers are alike, the resulting cancellation or reinforcement of the SW varies constantly.

Now try to envision that pattern with eight speakers in a cabinet and you see an entirely different approach to this condition. Then add a stereo side cabinet and vary the speaker positions or perhaps even reverse the phase to one of the speakers and you get all sorts of tonal patterns and variations. While the wiring idea proved impractical, it does have it's own special characteristics and qualities.

Jody: Caleb is just fine and I'm getting back into the groove again. It's been a rough winter but the trees are blooming again and so are my mental processes. I hope to maintain them. Now I want to go back to the Humor Forum. Haven't been there in a while either !!

Regards, Paul