Need some help with a pensil build, while the speakers are slowly being warmed up.
Due to restricted materials availability locally, the intended cabinets are posing problems by either quality of ply available, or restricted thicknesses (I am off the normal map if you will). I even considered building the main cabinet in 20mm granite which is available, until I worked out the hernia inducing weight of a single speaker.
I even considered using 40mm beech worktop for the sides as it was more consistent than the ply here.
With the throat thickness for the pensil baffle defined as 18 - 20mm, is there a way in which a thicker material can be used (and round the throat edges), or would that have a detrimental effect otherwise ?
Due to restricted materials availability locally, the intended cabinets are posing problems by either quality of ply available, or restricted thicknesses (I am off the normal map if you will). I even considered building the main cabinet in 20mm granite which is available, until I worked out the hernia inducing weight of a single speaker.
I even considered using 40mm beech worktop for the sides as it was more consistent than the ply here.
With the throat thickness for the pensil baffle defined as 18 - 20mm, is there a way in which a thicker material can be used (and round the throat edges), or would that have a detrimental effect otherwise ?
A speaker made of granite would truly be spectacular looking. Perhaps a thinner granite like 1/4 in thick for the front baffle only and thicker plywood or what have you on the back and sides. Getting a driver cutout and holes drilled will have to be done by a granite cutting professional shop.
The A7.3 needs about a 10mm rebate to sit flush, plus 8 to 10mm for the screws. I did talk with a mason about making one in black granite, and it was viable in 16mm for the cabinet, but when it got to the baffle, I believe the translation was "go forth and self reproduce".
Granite cabinet yes, baffle no, and even at that at 40+kg, is impractical. It certainly would look spectacular, particular as it descended the four storeys to the basement...
Ply or beech blockboard are the current favourites....
Granite cabinet yes, baffle no, and even at that at 40+kg, is impractical. It certainly would look spectacular, particular as it descended the four storeys to the basement...
Ply or beech blockboard are the current favourites....
If you're able to taper a significant part of the baffle, then yes. If you're talking about a simple chamfer of the back edge of the vent, then unfortunately not. The extra length will lower Fb somewhat away from the stock alignment. However, the difference won't be all that much, so I wouldn't worry about it too much.
Having heard speakers made from both solid stone (diamond cored basalt) and "Corian" or equivalent acrylic solid surface counter-top material, I'd say stick with the plywood.
And as boblamont mentioned, good luck finding a shop able to rebate holes for flush mounting the drivers in solid granite, as well the requisite rear side chamfer. Through holes and some degree of profiled edges are easy enough, but if the technology exists to achieve a clean rebated round hole, the machine time would likely cost more than enough high quality plywood to complete the project.
If you need to use the thicker wood material for the front baffle, a few cross-cut passes with a dado blade could effectively reduce the thickness in the vicinity of the vent. You'd also need a deeper chamfer at the driver opening.
And as boblamont mentioned, good luck finding a shop able to rebate holes for flush mounting the drivers in solid granite, as well the requisite rear side chamfer. Through holes and some degree of profiled edges are easy enough, but if the technology exists to achieve a clean rebated round hole, the machine time would likely cost more than enough high quality plywood to complete the project.
If you need to use the thicker wood material for the front baffle, a few cross-cut passes with a dado blade could effectively reduce the thickness in the vicinity of the vent. You'd also need a deeper chamfer at the driver opening.
The stoneworker guy said he could do it Chris, but warned against it.
He pointed to the weakness of the thin granite left at the back of the speaker rebate through which the mounting screws would have to mounted, the screws applying pressure radially on a thin flange. Granite does not give or form a thread tap like plywood, it fractures. He was not happy about the amount of meat left on the periphery of the baffle at the driver either.
If I have to go thicker for the baffle, it will be a long taper as both suggested.
He pointed to the weakness of the thin granite left at the back of the speaker rebate through which the mounting screws would have to mounted, the screws applying pressure radially on a thin flange. Granite does not give or form a thread tap like plywood, it fractures. He was not happy about the amount of meat left on the periphery of the baffle at the driver either.
If I have to go thicker for the baffle, it will be a long taper as both suggested.
If only you knew Andrew....
Were I home in Scotland, or back in Romania, there would be no issues, unfortunately I am working in neither.
FleaBay and postal services are on another planet.
Had to hand carry in cables, terminals, speakers, micro amp, dac, etc. just to stay sane, finally cracked and brought the Alpairs. Plywood may well prove to be my next luggage....
Boblamont,
Wow, it sounds like you are on assignment out in the sticks, literally. At least you have internet access to diyaudio What indiginious materials/building materials/junk is available where you are? If sound quality is more important than looks, as you are at a job site, maybe making something that may look dog ugly, but is cheap and sounds good may be something you can do? When is your next trip back to civilization so you can hand carry some choice construction materials?
If you ever see flat panels of any type of plywood, or better yet, kitchen cabinet door panels, wall panels, drywall, ceiling sound tiles, etc being demo'd from a construction project site.... Those make an excellent back and front baffle for a Cornu BLH http://www.diyaudio.com/forums/full-range/225622-ever-think-building-cornu-spiral-horn-now-you-can.html. I know you are asking for Pensils but those require lots of materials, clamps, a table saw, etc and lots of cutting nice 90 deg corners. May I suggest the Cornu as an alternative? Give it some thought, many folks have been super pleased with the sound and construction can't be simpler. So what you need to bring with you the next time you come home are: hot melt glue gun and lots of glue sticks, a razor, ruler, some old pillow stuffing, some cat 5 wire, a printout of the Cornu plan all folded up, a bottle of pva glue, some wood screws to mount the drivers, wire cutters/strippers, a small keyhole saw for cutting the driver hole, and most importantly, foam core panels pre-cut into 4 in wide strips. This can be very compactly fitted in your suitcase. They can be even cut along the 20 in direction so that they fit in your roller carry-on bag. You may have issues with the razor and saw for carry-on luggage you now have the ingredients for a very nice sounding speaker for your Alpairs that is easy to make and requires only rudimentary tools and supplies, while relying on almost any flat natively available panel for the main baffle and back. I would build the 28 in x 4 in version for the Alpair 7. Trust me, it will sound better than you can imagine. Hope that helps, but that is my 2 cents for your predicament. Good luck!
Regards,
X
Wow, it sounds like you are on assignment out in the sticks, literally. At least you have internet access to diyaudio
What indiginious materials/building materials/junk is available where you are? If sound quality is more important than looks, as you are at a job site, maybe making something that may look dog ugly, but is cheap and sounds good may be something you can do? When is your next trip back to civilization so you can hand carry some choice construction materials? If you ever see flat panels of any type of plywood, or better yet, kitchen cabinet door panels, wall panels, drywall, ceiling sound tiles, etc being demo'd from a construction project site.... Those make an excellent back and front baffle for a Cornu BLH http://www.diyaudio.com/forums/full-range/225622-ever-think-building-cornu-spiral-horn-now-you-can.html. I know you are asking for Pensils but those require lots of materials, clamps, a table saw, etc and lots of cutting nice 90 deg corners. May I suggest the Cornu as an alternative? Give it some thought, many folks have been super pleased with the sound and construction can't be simpler. So what you need to bring with you the next time you come home are: hot melt glue gun and lots of glue sticks, a razor, ruler, some old pillow stuffing, some cat 5 wire, a printout of the Cornu plan all folded up, a bottle of pva glue, some wood screws to mount the drivers, wire cutters/strippers, a small keyhole saw for cutting the driver hole, and most importantly, foam core panels pre-cut into 4 in wide strips. This can be very compactly fitted in your suitcase. They can be even cut along the 20 in direction so that they fit in your roller carry-on bag. You may have issues with the razor and saw for carry-on luggage
you now have the ingredients for a very nice sounding speaker for your Alpairs that is easy to make and requires only rudimentary tools and supplies, while relying on almost any flat natively available panel for the main baffle and back. I would build the 28 in x 4 in version for the Alpair 7. Trust me, it will sound better than you can imagine. Hope that helps, but that is my 2 cents for your predicament. Good luck!Regards,
X
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Not quite out in the sticks, just an artificial environment where the assumed norms do not apply...
The Pensil design is less intrusive than the FH3, so Scott's creation appealed, and I can take the drives when I leave and build either back home. It is just a matter of finding that material which is permitted here, and engineering the solution within that, Chris and Scott's observations have extended the options now.
Have followed the foam-core escapades with some interest, may try it later, but not on this occasion.
The Pensil design is less intrusive than the FH3, so Scott's creation appealed, and I can take the drives when I leave and build either back home. It is just a matter of finding that material which is permitted here, and engineering the solution within that, Chris and Scott's observations have extended the options now.
Have followed the foam-core escapades with some interest, may try it later, but not on this occasion.
For the 7.3s you can get away quite nicely with 15mm plywood of decent quality, and even with the smaller drivers, I wouldn't consider the Pensils without some front to back and lateral bracing.
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I am working on (applying veneer now) a 12mm version of my M10-A10 tweaked to work with the A10P. I here no difference between the thin version and the original built with 18mm material. This is real hardwood Russian birch, not the softwood Chinese knockoff.
IMO 12mm BB/Russian birch is good to ~12" panel widths with only a 12x50mm panel stiffener. I do use window braces around the driver and a 24mm top panel. Gives the whole structure a nice sounding knuckle rap.The long panels of a MLTL don't sound so firm, but once 24mm of type 700 fiberglass lining is applied, the cabinet is sufficiently quiet.
Bob
The Pensil design family is by Scott Lindgren - the bracing & aesthetic flourishes in the photoed pair have become a bit of a signature by the Planet10 team.
The "details" are that I built as per the drawing (with extra bracing), chamfered the long front edges, added grilles and a 1" plinth echoing the footprint with a 1/4" recessed spacer to create a shadow reveal line - pretty standard stuff.
Chris,
Is there any particular reason that these holey plate type braces are better than say hardwood dowels or battens randomly spaced?
I can see that front to back and top to bottom would be firmly linked by this arrangement, but would cross dowels not lock the side panels adequately?
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