Alpair Pensil 10p Build - and Questions

This is my second speaker build. My first was a set of Dallas II cabs I documented here :

https://www.diyaudio.com/forums/full-range/318518-dallas-ii-build.html

My wife felt pretty strongly that she wanted something with a smaller footprint in the living room, so I'm building the Pensils and the Frugel Horn XL and seeing which ones get the upvote. I'm going to have fun with it.

This promises to be an easier build, but as a trade-off, I plan on being more detail-oriented with this one. I broke down the stock over the weekend into roughly what all the panels will need to be (pics later).

In order to make the speaker as adjustable as possible, I'd like to be able to easily remove the driver and the back panel - and in the interest of durability, I was thinking of using machine screws/bolts and threaded inserts directly into the wood. These usually come in some kind of metal. For the back, I'll use some kind of neoprene along the edge to seal it up and avoid vibration. The driver gasket will do the same thing along the front. Are there any issues acoustically with using these metal inserts?

Second - I've decided for now to forgo the side to side bracing, which the designer says are not needed for the (smaller than 12p) pensils. Anyone have thoughts?

Third - I'm considering a double thickness baffle for the front, but the trade-off is that with double 19mm plywood, I either end up with a deeper inset (which I guess I can chamfer) or I end up with a lot of thickness behind the driver frame (which I can also chamfer). Any pros or cons here?
 
Second - I've decided for now to forgo the side to side bracing, which the designer says are not needed for the (smaller than 12p) pensils. Anyone have thoughts?


The holey braces are the funnest part of the build:eek:. I even used them on my CHR-70 Pensils, makes for a very, very solid cabinet and braces the driver. Would definitely recommend if you plan to crank 'em up.:D
 
frugal-phile™
Joined 2001
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The A10p come with gaskets, and neoprene (closed cel) foam strip is what is typically used on the back.

The allowable depth of the vent is 18-10mm. If you double the baffle (is is really needed with the full-length brace) you can just leave the inner piece short of the vent, or do somethig decorative with the outer piece.

dave
 
What Dave says. The bracing is always recommended, since it does provide a superior box structure; it's just not a fundamental requirement in that it improves things, rather than is a night and day change.

There are no 'wings' in the Frugel horns; they do have horn termini however, which are not optional: they're a significant part of the horn. ;)
 
Right, so here are my pics with the lessons I learned from my Dallas II build. For all the newbies like me that aren't professional cabinet makers.

1. Most people say measure twice - cut once. I did that with the Dallas II and still screwed it up. First, your tools probably need adjusting unless you use them daily. Second, as panels get progressively smaller, they get easier to manage, and it's easier to make the cut right. Usually I give myself a half inch on the big cuts, then true everything up on the table saw or miter. This also gets my edges cleaner and more square than just trusting the track saw.

2. For building cabinets, try to set your table saw and make all the same sized cuts in one pass. It's really hard for me to get exactly to the same 1/16th or 1/32nd of an inch on my table saw twice, which means I end up with panels a fraction off. So instead for this build, I ran all of my 8 inch width cuts at 8.5" then flipped them to the other side to get down to 8 inches. Both sides had really clean cuts and every single panel is the exact same width. Did the same for all my 12.5" cuts.

3. You can never have too many clamps. Smarter people than me may be able to use less, but I have a metric F-ton of clamps. They're cheap, they're useful, get some.

4. Buy a Wixey digital angle gauge. That means you don't have to trust the little hash marks on your miter or table saw (for people that don't own Festool everything), and it works great for adjusting. Plus they're cheap.

Pics below, with my highly technical cut sheet for my 5x5 baltic birch ( the drawing is ~4x5 - removed roughly 13 inches to fit in the back of my Land Cruiser.

Baffles tomorrow. Question - is it easier to veneer rounded corners or beveled corners?

Flatsheets.jpg

Cutsheet.jpg

Cornergluing.jpg
 
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Progress

So I've started gluing together the panels, a few lessons learned on the inset and rear chamfer.

1. Slower speed is actually better for the rabbet bit on the router. Since my router has a 1/4" collet, I made several passes to get to the 11mm depth I needed. I totally effed up a set of panels the first go-round and actually bent a bit.

2. For the rear chamfer, 45 degrees was way too steep, so I ended up making 2 passes with the 45 degree chamfer and then taking a file to it to give a more gradual slope.

I made a 45 degree bevel on the bottom of the baffle near the vent with my sliding miter, hopefully that's the right approach.

I started gluing together the panels, and I'm fairly happy with the results so far, and it's coming together fairly cleanly.

Router.jpg

Rabbet.jpg

Halfbox.jpg

Bevel.jpg

Backbox.jpg
 
Looks great. And very familiar - I am making their cousins these days :)

The bracing was a headache, using cup drills I destroyed one vertical table drill and 2 18v cordless drills were not up to snuff. However it was a breeze with a router. Though I am getting these black areas, not important at the back in the image but will need to be sanded on the front (use a bosch pof 1400 and can't adjust speed).

I had hoped it would be possible to glue all pieces together in 1 go, do you think 1 piece a time as you do is much better?

For damping in the top area I have either wool on some kind of canvas, or a semi-long-haired bathing mat with a thin rubber bottom. Seemed to make sense in the store but probably is a stupid idea :eek:


IMG_0794.jpg
IMG_0787.jpg
 
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Bracing looks neat. Mine I think is going to end up looking like what they have in the 12p plans. The way you are doing it looks simpler though. I might copy that.

I noticed you didn’t cut a chamfer at the bottom of the baffle. It’s not on the plans but I thought someone mentioned it was a good idea.

With respect to the gluing - I haven’t ever run across Baltic birch that didn’t have at least a slight warp in it - especially over long panels - and I find that no matter how precise my cuts are that I need clamps to pull something or another 1/16th in some direction. So slow gluing makes the box look neater at the end. YMMV.

Overall I’m a person that learns more by making mistakes than following directions. But if I take it slower there are fewer mistakes.
 
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Kyngfish, not trying to hijack your thread.
I have built quite a few cabinets over the years and have did all but my Ids clones with radius corners and veneered them, not easy but they look nice.
Has anyone here ever heard the 12p pencils?

Thanks, Greg
 

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