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@HacksawbobDefinitely DO NOT use a router and carbide cutter on wood that has metal fasteners already in place. That is a recipe for a hospital trip. If you did butt joints and biscuits or dowels you would be fine, but screws/nails -- no way. Your progress looks good. You've gotten a lot further along than I have.

The picture of the Scorpion that Hacksawbob is showing has a hole in the rear magnet assembly. On my Scorpion that was filled with a foam plug to prevent debris from falling in. The issue is that after 20-30 years, the foam disintegrates on touch and "becomes" the debris. Hacksawbob's may have already disintegrated since it looks like nothing was there. Progress on my combo to head/cab has been slow. I was back at work and also applying for a new role (which I did not get after a month of interviews, grrrr!) I did get the headshell glued up and just sanded down the finger joints over the US Thanksgiving holiday. It looks like this now: I need to pull out the router table and mount my 1/2" Bosch router with roundover bit. I'll be moving the work instead of the tool this time and hopefully have an easier time than I had routing the finger joints. Even with the finger joints and clamps while gluing I had a bear of a time trying to get this to come out square. I was not entirely successful. My cabinet will be larger in depth than my Porter Cable dovetail jig allows, so when I eventually get to the cabinet, I think it will be butt joints.

No progress on the head shell, too much going on. I did verify that the Scorpion is still operational after cleaning out the old foam dust protector that disintegrated on me. I had disassembled the magnet a month ago and cleaned all of this out as well as using tape to fish any garbage out of the voice coil gap. I reassembled the magnet to the basket but never had any way to verify the speaker was still OK. Well this weekend, I popped the speaker back in the old Peavey cabinet with a new speaker wire pigtail terminating in a 1/4" jack. I plugged this into the amplifier out on my Orange Terror Stamp pedal board amp and it tested out fine. The bonus was learning that the Terror Stamp made a fun little bass practice amp as well. Glad I verified this before spending time constructing the cabinet only to find I had messed up the speaker.

What Phil said and additionally I probably "should" have stuck with my larger Bosch router. The collet is bigger (1/2") and I could have used my straight spiral cut bit. Also, it comes with 2 wrenches that you use in opposite directions to tighten the collet. The router I did use was a smaller Dewalt trim router with a 1/4" collet and uses a single wrench to tighten along with a button you depress that "locks" the router spindle from rotating. I think my Dremel also has something like this too, and although convenient, I always feel like I am not getting the bit in tight enough. I think the 2 wrench style is better. The more I think about it, these dovetail jigs are flawed in that they require you to make the complete pin or tail cut in one go. Normally, when I route out a guitar body, I either cut away or hog out as much wood with a saw or Forstner bit. By the time I start routing with a template, I am only removing small amounts of material and lowering the bit until i get to the final depth. I do not like a 2 cutter dovetail bit biting full depth into a cabinet side. The is now doubly so with routing this birch ply. The Fender-style cabinet I did half-blind dovetails in solid pine was not the endurance test this Peavey headshell was. Retrospectively, since these were straight cuts for box joints instead of an angled dovetail cut, I guess I could have removed material in smaller bites. I still need to work out final dimensions for the speaker cabinet, but I realized my dovetail jig is only good for 12" width boards. This headshell basically maxed it out. The speaker cab with bee deeper, so I think I am limited to rabbit joints with the tablesaw.

Yeah, I definitely had a moment of "ya dodged a bullet there, fella."

Alright, good thing I planned this job for Saturday, because it took me until end-of-day Monday to get it all cut and dry fit. The Kreg edge rip guide was the way to go instead of the tablesaw for even this half sheet of birch ply. I also grabbed the 1.5 inch foam insulation to use as a backing board. The rip cut to 11.75" width for the headshell went smoothly. The first scoring cut and then cutting to full depth also left me with a clean edge and no tear out. That was Sunday. I then tried my chop saw for cross cuts and no matter what I did, I could not get it clean and perfectly 90 degrees. So I chopped the head shell top, bottom and sides oversized and got everything dimensioned properly on the tablesaw. Today (Monday) is my last day of my work sabbatical, so I wanted to get the box joints finished. Setting up the jig and getting bits centered in the router went easy. First cut and I had massive blowout from the 2 blade 1/2" cutter on the inside on the first 2 pins on one of the side pieces. It was nasty but I didn't take any pictures. I was so flummoxed as to what to do, I forgot. I had a spiral cutter that I should have been using, but it was 1/2" and I wanted to use my smaller 1/4" collet trim router. Next time for the speaker box I'll pull out the 1/2" Bosch router and use the spiral bit. I found some 1/4" MDF and cut a sacrificial face board to put over the plywood. This worked and the rest of the cuts went more or less OK. I did have a scare as I was not checking the tightness of the router bit after every pass. On the 4th or 5th cut the bit must have loosened and my cuts got shallower as it pushed the bit up to the collet. I am really glad I stopped at this point and did not hurt myself with a metal cutter spinning at 20,000 RPM. I dry fit the headshell box to check all my joints. I'll clean it up and glue it together this weekend. I also test fit the Peavey combo chassis to get an idea of what it will look like. Now, I get to go back to the office after the last 10 weeks off. Argh...

I grabbed a Kreg rip guide last night and I'm going to try this out today. I also bought some solid core foam insulation to use as a sacrificial backer board. Wish me luck!

I was hoping to at least get the headshell knocked together today. No such luck. I dragged the table saw out in to the driveway and set up a makeshift feed and outfeed tables with stands/sawhorses. I dug out the zero clearance insert I bought ago and never used to limit tearout on the birch ply. Switched the saw on and slowly raised the blade to cut through the blank zero clearance plate the first time. I was going to use the shallow cut method to score the underside of the ply at less than a mm and then repeat with the blade raised , again to prevent tearout. I practiced feeding in the half sheet of birch with the blade lowered and the saw off to see how it would work. No matter what I did, I could not get the ply to sit against the table saw fence with the factory edge. Realized that I was going to ruin this $40 half sheet of ply if I proceeded. Decided that I am going to reverse the procedure and bring the saw to the plywood. I'm looking at edge clamps and DIY edge guides now on YouTube to use with my circular saw. Time to run to the big box HW store... I will try to pick this up again on Sunday.

I like the NASA reference. We all groaned that day...

Phil thank you again, for both the knowledge and your patience. I think I missed that we were talking about the added variable of "tuning." I was getting hung up on dimensions first and choice of materials. The 55L at (purple) 55Hz is a fine number to settle on. When you speak of tuning, this is the job of the port itself, correct? And the length of the port will determine the frequency tune? (Really the volume of the pipe but if I settle on standard drain pipe 110mm UK or 4" here in USA the length is the only part I vary) I picked up a 1/2 sheet (30" x 60") birch plywood today. It is being sold here are 1/2" but comes in at 12mm by my caliper measurements. I'm going to sketch this out on paper in the next few days and see if I can possibly get started by this weekend.

Thank you for posting the wdr file for the Scorpion 15. The numbers in the one I created are vastly different, so not sure I entered them correctly. It is also difficult to get ALL of teh Scorpion 15 specs especially since this one is from the 1980's and even the most recent incarnation is EoL. I am not 100% sure what that final graph is telling me, but I see the big scoop in the green line. It looks like the red line for the 70Hz tuning in a 55L cabinet is the best compromise. Again, this is a cabinet to have around the house and not intended for playing out. Really just an attempt to reuse what I already have, make it usable across different amps if needed be and reduce the weight from this massive Peavey MDF monster. I think I am going to shy away from solid wood at the moment and use 1/2" (12mm) Baltic birch ply instead. I'll start with rehousing the amp portion of the combo first since it "should" be the easier of the 2 jobs.

Thanks for all of the great information and thank you for the encouragement, Phil. I have attempted to enter the Scorpion details into WinISD but not sure if I have done it correctly. The first graph it returned for me was very optimal for bass to 50Hz but the defaulted cabinet size was gigantic. I downloaded and installed WinISD 0.7.0.950 and created the .wdr file for the Peavey speaker since included by default. Can you share your .wdr file for the Scorpion so I can see if mine is correct? I was aiming at using a solid wood like poplar or the clear pine that I have built a Fender-style modified vibro-champ from in the past, so I might do some nice joinery and stain. Unfortunately, it seems that both the dimensioned pine and poplar boards available stop at 12" widths. If I wanted to make a cabinet deeper than this to still have the requisite 60ish L it would have to be taller and wider and therefore less compact. Compact was one of my goals. I could achieve a depth greater than 12" by laminating boards, but I don't think it will look as nice. Also, I did not want to go to the lengths of purchasing thicker 8/4 poplar, splitting them and book matching. So I need to give my materials and eventual covering some more thought. Black tolex is boring, but I guess it is pretty classic.

I have also grabbed the old Electro-Voice TL606 and TL806 plans floating around the net. This TKO65 cabinet and that quasi-half Showman cabinet volumes fall right in the middle of TL cabs. From some additional Google-fu I have found comments on other forums that indicate the Scorpion benefits from a smaller box volume and only treating them as a mid-low speaker. "...The specific construction tends to favor (or be optimized for) the range above about 70Hz as they were also used in smaller PA speakers, stage monitors, etc." So maybe I just "pick a size" and start experimenting. Somewhere between the original combo 48L and 66L, maybe ~57L. Funny, because 57.8L is the internal volume for the "entire" TKO65 combo if you count the space occupied by the amp...

I contacted the guy in the video about the actual dimensions of his sealed "half" Fender Dual Showman style cabinet. He provided internal dimensions: 58,41 cm high x 43,18 cm wide, 26,10 cm deep (23"Hx17"Wx10.25"D) My math puts this just under 66L. (2.32 cu ft) Here are the existing Peavey TKO 65 combo dimensions again: 18.75" (47.625cm) high x 19" (48.26cm) wide x 8.25" (20.955cm) deep Volume: 1.7 cu ft (~48L) Again, it has that triangular port approximately 7 inches squared. Since this port has no extension inside the cabinet except for the depth represented by the thickness of the 3/4" baffle thickness, I'm not even sure how to determine "how" this cabinet is tuned.

I took the 15" Scorpion out and first thing I did was to check the condition of the foam dust cap on the rear of the magnet assembly (motor). As many online forums indicate, the foam was ready to disintegrate at the slightest touch. As I did not want this in the voice coil, I disassembled the motor from the basket and cleaned out the foam. Then cleaned the voice coil gap with masking tape as Peavey recommends in their field replaceable basket documents and reassembled. Using a kitchen scale, I got these weights: Magnet assembly only (motor): 4.15 lbs Fully assembled speaker (motor and basket): 8.15 lbs. Moving to a digital scale for humans I got the cabinet weight: Empty cabinet: 39 lbs Empty cabinet plus grill cover: 41.2 lbs The cabinet is indeed particle board and probably the reason the 24"h x 20.5"w x 12"d cabinet weighs as much as it does. With the speaker removed, internal cabinet dimensions are: Height: 18.75" (47.625cm) Width: 19" (48.26cm) Depth: 8.25" (20.955cm) Volume: 1.7 cu ft (~48L) The triangular shaped port was difficult to get an exact measurement on, since the corners are rounded. If they were not rounded and each corner was taken all the way out to the corner inline with the sides they would be a ~4" x ~4" x ~5.66". As it is the matching sides of the isosceles triangle measure ~3" were they transition into a 3/4" rounded corner into the hypotenuse of approximately 4.5" until it transitions into the corners. Lastly, measuring with the side of the ruler flat on a side, the measurement come out somewhere in the middle at ~3.75" x ~3.75" x ~5.25". I'll use this last one for an approximate port size of 7.03 sq inches (45.35 sq cm).