How to handle these (cab) dummies

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therecluse

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Mar 17, 2014
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#1
Today I picked up 2 Mesa Powerhouse 115 cabinets of craigslist for $50.

Sounds too good to be true, right? There's a catch...

These cabinets were used as dummy cabinets on stage and the baffles are just a solid board without holes for ports or a speaker.

I figure this would be a good project and even after new speakers and some miscellaneous hardware this will still end up being a great deal for a couple of nice cabs, but I'm trying to plot out the next steps to make sure I handle this properly.

The baffle boards are glued in to the surrounding cabinets, so I can't remove them to make the necessary cuts. Also, because the baffles are recessed it doesn't look like i can use the normal circle jigs for a router because they won't have enough clearance.

I'm thinking of using a circle cute to score the circumference of the speaker hole, then using a plunge cutter to do the dirty work. I suspect it may not be a perfectly circular cut, but it will get the job done.

I'm also wondering about the horn and the ports. I never use the horns on my existing mesa cabs, so would omitting the hole for it matter?

Similarly, It looks like the current powerhouse cabs have a triangular port to the left of the speaker. I could cut this in, but is it necessary? Do these cabs need to be ported at all, or could I just mount the speaker and go for it?

Any and all input is much appreciated! Thanks!
 
#2
Under these conditions, I would recommend using a jig saw and it's going to take a lot of had work to get this done. My experience freehanding a router has not been very good, not close enough to mount a speaker ;)

If you are trying to get close to a powerhouse, you might want to order a correct replacement driver, and port it the same way the original cabinet is ported. Otherwise, you are into the same thing as building a custom cabinet except the box is already done. If you make it different, out of fairness to the next owner, disclose what you did.
 
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#3
Take the grill off and cut out all but the outer couple inches of the baffle board with a saber saw. Then cut a board sized to fit over the remaining baffle board - use 1/2 inch plywood, paint flat black. Cut the holes for the drivers . Add braces as needed. Then mount the board, then the drivers. If you can't get stock drivers (and crossover), you'll need to select drivers based on their modeled performance, and add the appropriate porting. there are plenty of good drivers available. If you provide a budget, some idea of your tone preferences and cab internal volume people here can make some good suggestions.
 
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#5
aged horse:
All the replacement speakers/drivers are available as parts direct from mesa. I'm waiting to hear back from them regarding jack plate availability. I was thinking a jigsaw might work too. The good part is, there's no rush and I can take my time with these. The goal is more about getting a couple of usable cabs more than flipping, but if I were going to sell them, they'd require full disclosure for sure.

Astrosonic:
That's an interesting approach - cutting out the bulk of the existing board then mounting a new baffle to it. That wouldn't leave room for the grill to go back on though.
 
#6
You will have to ask the customer service guys, I do not know the official policy on this sort of thing.

Cutting out the baffle and adding one on top will not leave enough space for your existing grill to go on properly.
 
#7
If the grill has a lip around the sides that rests against the baffle board, you could use Astrosonic's advice but size the new baffle a bit smaller to allow the lip to fit around it against the original baffle. The speaker would be 1/2 inch closer to the grill, so you'd need to make sure there was still a gap between the speaker and grill.
 
#8
the circle cutting router jigs work great but not with a raised edge in the way. either buy a cheap harbor freight router table or make your own. basically reverse the setup. instead of moving the router on a pivot point. make the router stationary and pivot the cabinet on the router. just use a dowel or metal rod mounted to the table and drill the center point in the baffle and rotate the cab. you simple use a router bit thats long enough. they have 2 1/2 inch long straight router bits. i like the cheapo router table from harbour freight cause its a wood top so yeah a dowel, rod, screw nail. really any worthy pivot point can be driven right into the table. or likewise just get a old table /computer table or whatever drill hole into it and bolt any decent router to it and whammmo you got a router table. old table would work great since now that i think of it the table would be just big enough to support the cab . or just make up for the baffle setback with another piece of wood or pieces of wood. if its setback 1.5 inches then two pieces of 3/4 inch ply so its flat now and cut out by hand with a jigsaw or again a long router bit with the simple jig you were gonna use. the peices would just be temporary of course and just mounted with one or 2 temporary screws. basically cut to same size as the grill. cut circle and then remove temp pieces
 
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#9
I don't think the lacking horn was addressed. Leaving it out will increase the effective cab (cu ft) volume. If wood from the dumy mod remains in place and it's behind the baffle, that will decrease volume. If it's a plastic horn with a replaceable driver, you could replace just the plastic and plug the end. Original might be best, especially for the next owner, but a cheap MCM or Parts Express part would also help reduce the volume. You can always add more wood or something inside if needed, just going by how it sounds...

If you want to skip replacing the crossover and adding a real horn, you might see if you can find out what the frequency response of the woofer is. It could poop out too soon to stand alone. If that's the case, better to go with a horn, or follow @AstroSonic 's advice to seek another woofer.

The title of the thread made me visualize a couple of dummies with huge under-bites and unkempt hair walking down the street with a couple of crappy looking DIY cabs :D
 
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#10
BogeyBass said:
the circle cutting router jigs work great but not with a raised edge in the way. either buy a cheap harbor freight router table or make your own. basically reverse the setup. instead of moving the router on a pivot point. make the router stationary and pivot the cabinet on the router. just use a dowel or metal rod mounted to the table and drill the center point in the baffle and rotate the cab. you simple use a router bit thats long enough. they have 2 1/2 inch long straight router bits. i like the cheapo router table from harbour freight cause its a wood top so yeah a dowel, rod, screw nail. really any worthy pivot point can be driven right into the table. or likewise just get a old table /computer table or whatever drill hole into it and bolt any decent router to it and whammmo you got a router table. old table would work great since now that i think of it the table would be just big enough to support the cab . or just make up for the baffle setback with another piece of wood or pieces of wood. if its setback 1.5 inches then two pieces of 3/4 inch ply so its flat now and cut out by hand with a jigsaw or again a long router bit with the simple jig you were gonna use. the peices would just be temporary of course and just mounted with one or 2 temporary screws. basically cut to same size as the grill. cut circle and then remove temp pieces
Click to expand...
+1 on the second piece of wood cut to fit inside the lip and raise the saws contact surface up.
 
#11
therecluse said:
Astrosonic:
That's an interesting approach - cutting out the bulk of the existing board then mounting a new baffle to it. That wouldn't leave room for the grill to go back on though.
Click to expand...

The grill appears to have nice folded edges. Cut out the blank baffle board leaving a 3 inch margin. Then cut the new baffle board just small enough to allow the grill to fit.

I like Munjibunga's suggestion, but given the baffle dimensions and driver cut out dimension, There is not likely to be enough room for a router or sabre saw (there is about 1 3/4 to 2 inches between the driver hole and the smaller edge). But there is likely enough room for a zip saw - kind of like a very small hand held router (Dewalt DW660 5.0 Amp 30,000 RPM Cut-Out Tool). The trick is to free hand cut a decent circle, but they are made to do just that.

It looks like the internal volume is about 4 cf - a decent amount of volume for a 15 inch driver. When you layout the driver hole keep in mind that you'll probably want to have room for a couple of ports.
 
#13
agedhorse said:
Zip tool is fine for drywall, but the oriented fibers of plywood are a bitch to freehand.
Click to expand...
That was my experience, but only with a dremal that came with a zip jig and bits. Works great on plastics. Took ten seconds to poo poo it for plywood.

A good quality trim router might fit as well. A bit larger footprint than a zipsaw. My Makita has about a 3" footprint IIRC.
 
#15
Lots of good ideas. Very much appreciated!

I had another thought about this. What If I cut a board to fit inside the lip of the existing cabinet, then used a circle jig to cute a hole where the speaker would mount. Then I could lay this board inside the lip and use it as a template for a router.

FWIW, the entire cabinet appears to be made out of MDF, not plywood. Not sure if this is the case with all of these cabs or if they just made these out of pdf since they weren't intended to be functional.
 
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#16
Are they the same depth as the real cabinet? I don't know anything about the custom and one-off pieces.
 
#17
I'd be suspicious of an MDF dummy cab. It might be fine but it could have unseen structural issues. You have to figure that, beyond materials, a dummy cab may not have the built quality, same joints, etc.

You have your money's worth in hardware. If it doesn't work out you can always copy the design and construct new ones out of plywood.
 
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