Everytime there is a transition, in this case from one ply to the next thru the glue, one gets damping.
dave
Some numbers for damping:
damping factor values - audio qualia
The composites and things with random particles generally do better than single materials. Some cheap stuff fares well.
e.g. acrylic over mdf is pretty good. Humble chipboard is pretty good.
The various resins are good too, so adding a fibreglass lining to a stiff ply (or whatever) shell seems like a good way to add both damping and stiffness.
damping factor values - audio qualia
The composites and things with random particles generally do better than single materials. Some cheap stuff fares well.
e.g. acrylic over mdf is pretty good. Humble chipboard is pretty good.
The various resins are good too, so adding a fibreglass lining to a stiff ply (or whatever) shell seems like a good way to add both damping and stiffness.
wonder what would be a good material to glue over 5/8" BB for Karlson "wings" to reduce Q ? I have a 1955 factory Karlson K12 - Formica -> 5/8" plywood -> 1/8" smooth "hardboard" (~ "Masonite)
Yes, it has a bit lower MOE of ~1.1 m Vs 1.8 m psi, so needs more bracing, but where looks isn't an issue and cost is........ I forget who, but someone here did a nice diffraction horn plus woofer cab out of it IIRC. I made a bunch of kid's bedroom and a few shop/garage/man cave speakers with it.
GM
Hey Dave p10, remember the super long thread ages ago where one guy kept 'taxing' you re when to push the cab resonance up or down, but eventually got it? Who was he? IIRC he's the one did the horn two way.
What would you say is higher quality, especially with any chance of having a similar number of laminates?
@Cableaddict: Most spruce I encountered is 7-laminate for 3/4" (9 if you're lucky), an equal number to 3/8" BB ply.
Regards Johan
If you ask a real plywood vendor to get void-free fir ply they will do it. We make all grades out here in Doug Fir country.
FWIW, when I've wanted BB, Apple or Marine grade in the last ~30 yrs I ordered from either Lowes or Home Depot except for the last time, which was a PlyMart that sadly has since closed, though Peach State Lumber Products has no void 13 ply in 4x8 ft sheets for ~ $129.
GM
Oh well........didn't find it in a search, but Google found a bunch I'd not seen, so apparently a lot more popular than I assumed: OSB diy horn - Google Search
GM
I've had really good luck going to cabinet supply houses, that normally only sell wholesale to the custom cabinet or furniture maker markets.
Always seems the sales desk guys have a soft spot in their heart for speaker builders 🙂
It's worth a try !
From such, around here in VA.... BB 18mm 5x5 $37 a sheet, 15mm $31 a sheet
Well, the problem is that cabinet suppliers typically have BB that's not graded void free; for instance Peach State's 5x5 13 ply is ~$43, but will have voids depending on the veneer grade whereas the 4x8 sheets are the only ones rated void free regardless of veneers [that they stock], so caveat emptor applies.
That said, the cab grade BB ply has got to be better than the seeming near hollow core of the furniture grade, Birch, etc., I see nowadays in the 'big box' stores.
When I queried them about Spruce ply, they made it plain that soft woods weren't on their radar, so to speak.
GM
That said, the cab grade BB ply has got to be better than the seeming near hollow core of the furniture grade, Birch, etc., I see nowadays in the 'big box' stores.
When I queried them about Spruce ply, they made it plain that soft woods weren't on their radar, so to speak.
GM
Interesting.
Both my suppliers say there is no difference in the 4x8 sheets, and the 5x5's, given equivalent grade.
I haven't used much 4x8 because it's rarer to be in stock.
But in the maybe 60 5x5 sheets of 18mm and 15mm I've cut up, I haven't seen a void yet.
I wish 4x8 were in stock more often simply for handling. IMO, 18mm 5x5 is a bitch to handle. 4 x8 is easier despite the extra weight.
Both my suppliers say there is no difference in the 4x8 sheets, and the 5x5's, given equivalent grade.
I haven't used much 4x8 because it's rarer to be in stock.
But in the maybe 60 5x5 sheets of 18mm and 15mm I've cut up, I haven't seen a void yet.
I wish 4x8 were in stock more often simply for handling. IMO, 18mm 5x5 is a bitch to handle. 4 x8 is easier despite the extra weight.
Your supplier may only spec void free whereas 'mine' apparently doesn't care in the 5x5 size. Long ago ['60s-'80s] I only used 4x8 marine no void, but once on-line some folks were telling me that marine grade was no longer guaranteed void free, so went with the 'party line' and began recommending the BB, but marine was/is still rated no void according to Peach State, so now wondering why the bad intel. End grain isn't as pretty, but at < $100 will be using marine.
GM
GM
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