3 ways with Peerless 830668 10" woofers in sealed bass bins. The top enclosures will have 2.5"+ roundovers with SB12MNRX2-4 midranges and GRS RT3.0-8 ribbons. Cut some PB after work:
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Nice driver combination, those should sound great!
5.375" OD cardboard shipping tube from work = free
Two 11.5" x 3/4" × 48" PB shelf boards from Menards = less than any 6" sandwich from Subway
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We had absolutely beautiful weather here today (71°F and partly sunny) so I took advantage and machined the rebates, through holes, and rear reliefs for the midranges. Perfect fits. Whew, glad those steps are done!!!
I still have to make a template and router the rebates for the rectangular ribbons. Then It’s smooth sailing 
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I made my router template to machine the rebates for the rectangular faceplates of the RT3.0-8 ribbon tweeters. I’m sure there is probably an easier/better way but this is just how I do it. This is not a daunting task to the experienced, but maybe me posting this could possibly help a newer builder who has been reluctant to use a rectangular frame driver.
First step: protect the ribbon and faceplate surface with some painter’s.
tape.
Second step: set the rip fence with the tweeter just barely touching the cutting edges of the saw blade’s teeth and the fence itself.
Third step: rip a piece of scrap wood the same width as the tweeter.
Step four: cross cut it in half, then use two other scrap pieces of wood that are the same exact thickness to form the template. I do this on my work bench top but it could be done on any surface that is smooth (ie the tablesaw top).
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Continued:
I use a piece of wax paper so the glue won’t stick to the work bench surface.
A tiny bit of TiteBond II and some very light clamp pressure:
Clamps and weighs removed… this template should produce extremely nice rebates with my 0.250" router pattern bit.
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That was how I made square templates before I got my 3D printer. You should use a bearing bit that matches the 6 mm radius of the corners of the tweeter. 1/4 inch is pretty close but you can buy 12 mm bits online if a test cut isn’t close enough. I mount the driver and stick the template to the baffle with double stick carpenter’s tape and then remove the driver and cut the rebate. I set the router on the template and plunge the bit until it hits the face of the baffle and lock it. I have a big set of wire size drill bits that I then use to set the depth stop on the router. It’s always a good idea to make a test cut on some scrap.
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Good additional advice Ron. Thanks!
Good pics, makes it easy to visualize and great tips Ron!
Even on the CNC and with round drivers, I still need to do at least a couple of test cuts, the posted specs are never accurate 
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And you have to plan for the wood finish
Definitely, all the layers of primer and paint adds up and a nice snug fit in raw MDF no longer fits!
I cut my rebates after the cabinets are finished. The only problem I’ve ever had is getting a wood chip under the router base and scratching the finish. After a little light sanding and another coat of poly on the baffle it’s all good.
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Yes, good point to consider if priming and painting. Since these are PB they will be veneered, so I like to keep the fit snug.
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New pattern router bit ordered.
Another beautiful day here for this time of year. After getting my yard chores done I spent a little time flush trimming the enclosures. I built the bass bins last year as ported prototypes for a pair of MCM 55-5670. I built them with some super cheap and sightly damaged PB. I had to enlarge the through holes for the bigger Peerless. I’ll have to cut some block off plates to seal off the ports.
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I cut these squares out of some scrap PB that are exactly the same width as the cardboard tubes’ diameters. A quick temporary tack with some hot glue and easily cut exactly in half on the table saw.
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Oh yeah, this is the timely post I was waiting for. I recently acquired a ‘crete form with a 7-3/4” outside diameter and a mailing tube with a 6-1/4” outside diameter…
Okay, carry on.
Great solution versus kerf bending. I’ll have to try it!
Horizontal polars should be super smooth.
Good idea for cutting the tubes in half