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Old 23rd March 2011, 11:15 PM   #1
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Default Starting my first speaker project: Pencil 7 questions

Hi all - so it's taken quite some time but I'm finally ready (I think?) to start this project. I originally had grander schemes in mind but decided to start with an easy build and do another if all goes well. That said, I have a few basic questions before I start:

First, the basics: standard Pencil 7 build, .75" baltic birch (pretty good stuff from the looks of it, but what do I know).

1.) Roughly, what will the impedance be?
2.) Internal wiring - what should I use? CAT5? Just a single strand or half for + and half for -? My speaker cables are made from Canare 4S11 and I have some extra laying around...should I use that?
3.) Should the inside of the port be rounded over? If so, what type of roundover?
4.) Should the inside of the driver cutout be rounded over? If so, what type of roundover?
5.) Do I need to finish/treat the wood after I'm done building? I don't mind this project looking rather basic as it's just an experiment, but if there's some "simple" way for me to make the wood look better, I'd be game.
6.) Seeing as I have no experience in woodworking...which layout for the top/bottom & sides should I use? I assume it's just a personal preference kind of thing, but maybe there's a generally accepted way to go: the top and bottom extend to both sides of the speaker OR the sides extend from the top to the bottom of the speaker OR (see image)?

Click the image to open in full size.

Thanks all - apologies for the noob questions but I'd rather ask now than screw up later.
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Old 24th March 2011, 02:25 AM   #2
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0/ 3/4" BB is probably really 18mm
1/ 4 ohms nominal
2/ we use ingle strand of solid core CAT5 (cryotreated just because)
3/ maybe, it is more properly called a terminus
4/ we champher it at 45 degrees, the quicker you get the cut-out sides away from the driver the better,

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Old 24th March 2011, 03:52 AM   #3
zacster is offline zacster  United States
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If I were building from Baltic Birch, I'd have the fronts as a solid piece, so the option on the right. If you are veneering it doesn't matter as you cover all edges with veneer.

I wouldn't worry about the wire, but if you are using Canare 4S11 on the outside, it will be fine on the inside. I use that cable myself. It is cheap and I'm always surprised by how many "audiophool" cables are made from it. All it takes is a snakeskin outer covering and it looks like it should cost thousands.
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Old 24th March 2011, 04:17 AM   #4
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Thanks for the help Dave (again).

And zacster - if I'm reading that right, you say that the fronts should take up the entire face of the speaker (no end grain from the top/bottom/sides showing)? I thought about that as well, but I saw more examples showing the grain than opting for a full-faced piece. I guess I'll just have to pick one and go with it.
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Old 25th March 2011, 07:44 PM   #5
chrisb is offline chrisb  Canada
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In designs such as Pensil (and numerous others) that have internal panels for slot ports, folded path dividers, etc., I always find it easier to overlay the side panels or fully inlay the internals, depending on how you want to look at it. Cut all the same width parts at one set up of rip fence and you should be golden.

edit; of course the generous mounting flanges of the Mark Audio drivers does make for tighter tolerances when rebating for flush mounting on baffles as narrow as the P7

As for exposed edge grain - if you're not planning on post veneering or filling and painting, but rather on directly finishing the raw plywood, you could simply edge band with pre-glued veneer tape before assembly and use biscuits / dowels for assembly alignment. Just make sure to adjust parts sizes for the approx .5mm thickness of the tape on each banded edge. If biscuits or dowels are used, band the parts first so that adjoining panels will align flush.
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Last edited by chrisb; 25th March 2011 at 07:50 PM.
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