Just ordered a set of Alpair 12P (Madisound USA) - Page 3 - diyAudio
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Old 19th June 2012, 04:32 PM   #21
StevenZ is offline StevenZ  United States
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Good info. Would you suggest something along the lines of a "supra baffle" that Bob uses or would that give the sound a completely different characteristic?
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Old 19th June 2012, 04:48 PM   #22
chrisb is offline chrisb  Canada
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Good info. Would you suggest something along the lines of a "supra baffle" that Bob uses or would that give the sound a completely different characteristic?

On which enclosure? A prime characteristic of the official "Ken" family has long been the narrow front baffle and deep chamfers to layered side panels, When combined with "golden ratio" derived or similar aspect ratios of front panel dimensions, this provides a fairly benign diffraction signature.


AFAIK Bob hasn't built with the 12P yet? - and even on a recent build of one of his designs for the 10.2 ( i.e. the M10A10 - great sounding enclosure), the suprabaffle needed to be thicker than 18mm once rebated for flush mounting. Also don't forget that with a suprabaffle, the opening on front of enclosure panel should at least continue the flare rate of chamfer / round-over on the SB - which on narrow enclosures may conflict with the width of front panel.

An SB on the Pensil12 might well work - I haven't built a pair yet, although will be cutting material for a pair for Jeff shortly.

Jeff: any thoughts on the subject?
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Old 19th June 2012, 05:38 PM   #23
mp9 is offline mp9  United States
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Please remember that if you plan on rebating the 12Ps for flush mounting that allowing for gasket compression and possible veneer finish, the required depth for flange and super-gasket is 10mm - so a single layer of 18mm won't leave a lot of meat for fasteners, particularly after the rear of opening is relieved with chamfer or round-over.

On the MK12Ps currently on the bench I used 18mm + 6mm ply for the baffle, which leaves approx 14mm of core for the hex head mounting screws.
Any reason why tee nuts inserted into the remanding 8mm of a 18mm baltic birch plywood baffle wouldn't work? The inside cut out on the baffle could then be cambered /a 45 router bit going from tee nut to tee nut. Then no need for a additional 6mm layer or supra baffle.

Last edited by mp9; 19th June 2012 at 06:02 PM.
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Old 19th June 2012, 07:14 PM   #24
chrisb is offline chrisb  Canada
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Any reason why tee nuts inserted into the remanding 8mm of a 18mm baltic birch plywood baffle wouldn't work? The inside cut out on the baffle could then be cambered /a 45 router bit going from tee nut to tee nut. Then no need for a additional 6mm layer or supra baffle.

I'm personally not a fan of "T"-nuts for this application - a few years ago a buddy of mine had a pair of Cain & Cain Abbys in which one of the T-nuts used to mount the Fostex driver the to solid Alder Supra baffle same loose - much fun getting those out - but threaded insert fittings, "hurricane nuts" etc, sure

However, since all of Mark's frames are soft enough that it'd be easy to over-torque them with a metal on metal machine screw and through the drive train out of alignment, I just use the supplied hex wood screws with a 9/64" pilot hole. I can really only see the advantage of insert fittings on drivers this size if you plan on repeatedly removing and reinstalling them.
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Old 19th June 2012, 07:44 PM   #25
mp9 is offline mp9  United States
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...good point re over-torque/alignment. I'll add the additional 6mm to the baffle.

Regarding Stuffing for the Super Pencil box:

I'm going to order a 5lb bag of Acousta-Stuf.

I'm also considering ordering the 1/2" Sonic Barrier acoustic foam and lining the back wall from top down to 24" leaving the last 12" bare, same for one side wall and also line the entire top wall.
Obviously i know it's trial and error but what's the consensus on that, good idea or not and or how should i change the plan?
(SB comes in 1/2", 3/4", 1" & 1"3/4")
Sonic Barrier 1/2" Acoustic Foam w/PSA 18" x 24" 260-520
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Old 19th June 2012, 08:38 PM   #26
chrisb is offline chrisb  Canada
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...good point re over-torque/alignment. I'll add the additional 6mm to the baffle.

Regarding Stuffing for the Super Pencil box:

I'm going to order a 5lb bag of Acousta-Stuf.

I'm also considering ordering the 1/2" Sonic Barrier acoustic foam and lining the back wall from top down to 24" leaving the last 12" bare, same for one side wall and also line the entire top wall.
Obviously i know it's trial and error but what's the consensus on that, good idea or not and or how should i change the plan?
(SB comes in 1/2", 3/4", 1" & 1"3/4")
Sonic Barrier 1/2" Acoustic Foam w/PSA 18" x 24" 260-520


I've never been impressed by several of the solid or corrugated foams I've tried - for this deep a box, I'd consider either rockwool, something like Owens Corning fiberglass ceiling tiles (available at your local Home Depot, etc) or the 2" Ultratouch denim insulation.
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Old 19th June 2012, 09:18 PM   #27
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I'm personally not a fan of "T"-nuts..... but threaded insert fittings, "hurricane nuts" etc, sure
Oh God, NO! If you mean these things, PE part # 081-1082, they are much worse than T-nuts. They will strip out by just looking at them. If everything isn't dead straight or the thread don't engage correctly, they will spin even before you get the bolt tightened down. Ask me how I know!

Bob
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Old 19th June 2012, 10:10 PM   #28
chrisb is offline chrisb  Canada
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Oh God, NO! If you mean these things, PE part # 081-1082, they are much worse than T-nuts. They will strip out by just looking at them. If everything isn't dead straight or the thread don't engage correctly, they will spin even before you get the bolt tightened down. Ask me how I know!

Bob

yer damned right - I was thinking of something else - personally either something like #081- 1098
Click the image to open in full size.

but many of these are a fairly soft alloy that can easily crack if over torqued when the pilot hole is too small - now that's a mutha to get out
or even better an external coarse thread unit like:

Click the image to open in full size.

EZ-lock, Hafele, et al
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Old 20th June 2012, 02:03 AM   #29
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Right! I use these all the time. They are usually Zamak, a zinc alloy. I use the flanged insert for most driver, but I think that the unflanged inserts would work best with MA drivers that have the gasket cast integral with the frame. Getting the pilot hole right is important as is setting the insert square. There are insertion tools for the purpose and I have seen demonstrations of using a drill press ti set the inserts. I just use a hex bit in my power screwdriver and pay attention to getting things square.

Bob
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Old 20th June 2012, 04:46 AM   #30
mp9 is offline mp9  United States
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Originally Posted by chrisb View Post
I've never been impressed by several of the solid or corrugated foams I've tried - for this deep a box, I'd consider either rockwool, something like Owens Corning fiberglass ceiling tiles (available at your local Home Depot, etc) or the 2" Ultratouch denim insulation.
Are you saying to use the acoustic-stuf or wool stuffing for fill and line 75% of three of the walls with Owens Corning tiles, or one of the other two products?

This the Owens Corning product you're referring to? - Owens Corning 703 1 inch panels at best prices - TM Soundproofing Inc

How about Delflex panels lining ~1/2 to 3/4's of the rear wall behind the driver and Home Depot denim insulation option at $6 16"x48" roll lining the top side and possibly inside baffle walls?
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