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Minimum thickness for speaker cab construction

#41
Thakid2u said:
If you dont like the sound of the cabinet when you get it done, try throwing some insulation in it. Just staple it to the back and or the sides.
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That's a basic requirement, any full range cabinet must be fully lined with damping material. Any exposed surface will reflect midrange waves back to the driver cone, arriving there at various angles of phase, causing response peaks and dips as deep as 24dB.
 
#42
billfitzmaurice said:
It's already been done, more than once, and the results published, in sources ranging from Speaker Builder and AudipXpress magazines to the Journal of the AES in the US, as well as European sources. Where weight is not an issue 1" MDF is the preferred material, where low weight is required 1/2" plywood cross-braced every 6 to 8 inches works best. Pound for pound cross-bracing is four times as effective as added mass in limiting panel flex, but costs twice as much to produce when labor costs are factored in. For that reason cheap cabs will often weigh a lot more than very high end cabs. Where cost is no object a honeycomb composite matrix gives the best strength to weight ratio; it's why JBL Vertecs are quite light and cost upwards of $10k each.
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Shucks, I was hoping for a plush academic research job.
 
#43
Tell you what. I'll build the cab, and do a full report, with progress photos and sound clips. I'll give an honest, no balls assessment of how it sounds and how sturdy it is. I'll ask for advice on bracing, etc, and build it the best I can. If it sucks, I'll admit it. If it rules, I'll gloat.:D
The way I see it, if I go out and buy the components, like corners, handles, etc, and the cab doesn't sound good, I can take them off and put them on a 3/4" plywood build, so I won't be out that much if I don't like it, because I want to build this box one way or another. My labor isn't worth a whole lot of $$, so if I have to build it twice it's not going to make me cry.
I'll start gathering components and hopefully get started by the end of July.
Awwww yeah, son!
C7
 
#44
very basic principles of using high quality materials, good design high quality speakers, will inevitably yeald good results,

When you are doing one cab, You can afford to go to greater lengh to build a great cab. When you have to do a 100, corners get cut, here and there,

Why not use the best it will last a lifetime and you will know that you did you best, nothing to wish you have done.

.
There are results published here and there on different materials, I dont remember who actually did the research but I remember Baltic birch was found to be acousticly transparent at certain frequency and other tests showed best responce after MDF, 1"MDF was top material. (very heavy) I tryed it once.

1" Baltic Birch is killer, I make 410 out of it, heavy as all get out, but not only flex resistant, it can take a lot of energy and vibration and not give a bit, I dovetailed it and braced it glued and srcewed. MONOLITHIC is the word.
 
#45
I understand the viewpoint, but I think it assumes that you have a killer design to start with. Otherwise, you are experimenting with expensive materials when you can experiment with cheap materials.

Another way of putting it is, are you designing a speaker to play, or one to test? If it is your first DIY project, then the main purpose is having something to test, because it probably won't be the final design.

In my house are three cabinets, all wonderfully made, which are being used for various purposes. One is my stool for sitting at the downstairs computer. It stores a 15" driver that I might use for a speaker project someday. One is propping up a bike in my garage. Another holds my alarm clock next to my bed.

My spouse had her own opinion about this. She said: "Don't bother building it to last a lifetime, because you can always build another speaker. In fact, I know that you will always build another speaker."

I seriously respect both approaches, but I think each approach is appropriate for a different stage of the development process.
 
#46
Crescent Seven said:
Tell you what. I'll build the cab, and do a full report, with progress photos and sound clips. I'll give an honest, no balls assessment of how it sounds and how sturdy it is. I'll ask for advice on bracing, etc, and build it the best I can. If it sucks, I'll admit it. If it rules, I'll gloat.
C7
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that sounds like a nice little project then. give it a go. if for no other reason, i know that DIY cab threads with pictures and reports and periodic updates "do" real well on TB. they are a hit. I know I enjoy reading them.:cool:

THAT BEING SAID. I have an even better proposition. send the finished cab to someone who knows cabs and doesa great job evaluating them (ahemtomBahem) and have HIM do a "no balls assessment."

shipping shoulndt be too bad, and it'd REALLY be an unbiased review. he could even pit it against the IP series of super cabs.

if TOM is unavailable or unwilling or disinterested (or busy smiling at his IP's), i am sure there are others on here who are equally experienced, or more so, who would do a review of your cab. It'd be worth the 40 bucks in shipping, IMO. hell, i'd even pitch in a few bucks if you have paypal. anyone else?
 
#47
Crockettnj said:
that sounds like a nice little project then. give it a go. if for no other reason, i know that DIY cab threads with pictures and reports and periodic updates "do" real well on TB. they are a hit. I know I enjoy reading them.:cool:

THAT BEING SAID. I have an even better proposition. send the finished cab to someone who knows cabs and doesa great job evaluating them (ahemtomBahem) and have HIM do a "no balls assessment."

shipping shoulndt be too bad, and it'd REALLY be an unbiased review. he could even pit it against the IP series of super cabs.

if TOM is unavailable or unwilling or disinterested (or busy smiling at his IP's), i am sure there are others on here who are equally experienced, or more so, who would do a review of your cab. It'd be worth the 40 bucks in shipping, IMO. hell, i'd even pitch in a few bucks if you have paypal. anyone else?
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There are enough Denver forumites on here that I could have one come over to my house and check it out, and give a report.:D
C7
 
#50
I seriously respect both approaches, but I think each approach is appropriate for a different stage of the development process.
fdeck said:
I agree. I built a single 12" transmission line cab out of some cheap ass, bunch of voids, semi beat-up 3/4" ply. Upon completion, I had a tech friend of mine test it and the results showed almost the identical line as the Thiele-Small specs of the driver(eminence kappa pro, 500 watt),with the exception of a little bump at 1k. Needless to say, I was stoked! So I purchaced some 3/4" void free poplar and built one for keeps. Broke it's virginity on the gig last weekend. Our guitarist (50 watt marshal 1/2 stack & 2-12 combo) was concerned that I was WAYunder rigged. After our set he immediatly came up to me and said "Holy ***T,what is that thning?" I simply grinned and said "Your worst nightmare" Oh yea. I was pushin' it w/ 600 watts rms. I.m building another soon.
Peace
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#52
Crockettnj said:
a home brew transmission line cab- very cool!

if you dont mind, where'd you get the design? are you an engineer? a design program, or just some real good "kentucky" windage?

wouldnt mind seeing a pic too.
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No, I'm not an engineer and did not use a design program. Just alot of very confusing math and a bit of California luck. I'll try to get pic posted soon. Dont want to hijack this posting so I'll PM you with some more info.
Peace
 
#53
The more bracing in a cab the more you reduce the internal volume; Turbosound were most particular as to the positionong of the struts in their cabs and demonstrated to Brian McKenzie at Precision Devices the importance of correct positioning.
Bill what type of dampening material do you use? I know that there are various schools of thought on this subject.
 
#54
Bassman62 said:
The more bracing in a cab the more you reduce the internal volume
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Not if you've gained back more than that amount by using thinner materials. I drill holes in my braces to reduce mass, minimize internal reflections and allow free passage of air within the box. I recently built a 16 cubic foot folded horn subwoofer with a ten foot horn path. With 400 watts sine wave input at 100 Hz the output is 133dB; you can stand a glass atop it and the glass does not move. It weighs 90 pounds, driver included.
Bill what type of dampening material do you use? I know that there are various schools of thought on this subject.
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Studies have found they all function just as well, though in a critical application like a TL the density required differs from material to material. Where it's important to keep driver frames and ports unobstructed I use convoluted foam or felt carpet underlayment lining. I use polyester pillow stuffing to fill areas where lining the cab is impractical and shifting material isn't a concern.
 

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