The Martian Stack
Marshall has their stacks, I have a Martian stack, face-on-Mars front panel, satellite dish, and all.
It started out as a Roland Boss MG-10, being sold for $15 because the guy who tested it (an audio surplus buyer and seller with musical experience in old electric organs) thought it sounded like it had problems. It sounded fine, it's just that this modeling amp was always meant for making distortion. It had 3 controls specifically for that, and just running it to hot brought it on. I got it in case he was right because I needed a matched pair of small instrument speakers. He was half right, but that's because it was working just fine. I'd used it as a distortion modeler, amping it through a Fender Frontman 65. It needed more though.
I tweaked it for power first by bypassing the input volume, used for mixing to wide-open distortion with non-distorted signal. I could still get clean sound (as clean as it ever got from this box) at the increased power level, so I knew if I gave it more headroom I could get more of that. So dropping the impedance after boosting the amp would probably work fine.
I took out the amplifier section and bolted it to the top, with screws running all the way through the handle, the amp and into the top layer, so it was carryable. I put a baffle around the pair of 5" 8 ohm instrument speakers inside and ported their back side through the horn I put in (the bell from a clarinet; because I could). Inside the original box I installed an 8" 8 ohm musical instrument speaker taken from a late 60s Lowry organ. Its font side was vented out through the opening where the map was removed. It got a solid baffle, with its backside ported out through the bottom into the lower 'cabinet' (a second sealed box with its ceiling before the floor of the upper box). Wiring to the lower cab went though the ports.
The lower cab got two Sony 6" 5.5 ohm woofers firing through a solid front panel, a baffle behind them open to let their back side into the same volume where the upper cab vented down into. A port made from a copper pipe cut at a very acute angle ran from this rear volume, through another piece of clarinet, through the front panel. The lower cab also got a sealed (ie. front firing only) high output, high dispersion piezo tweeter (a 75 watt glaring bright Goldman with a 200 Hz high pass capacitor on it). The drivers were wired as pairs (two Sonys, two Rolands, the Lowry and tweeter together) then paralleled to give a 5.3 ohm nominal load. At this point I figure I'm getting about twice the original 10W output, and moving 4 times more air than the original. And it's far more front-firing than the MG-10 ever was, the volume from behind about half from in front, thanks to all the baffling and driver isolating gasket material (also used liberally inside the isolate the volumes and keep the box completely closed too).
The post sticking out the top has a sheet music clip (the clarinet again) sticking out the top. The satellite dish is the front of an old humidifier fan, beause it looked far cooler than a small piece of PVC with a music clip sticking out. The 'eyes' were speaker covers from an old boom box that served better as pieces than something to listen to.
Testing was done with my favorite Tele, alone and though a Deltalabs DGFX-1 f/x box and pedal. Under its original indoor apartment level settings, the output volume was about twice what I got from the MG-10 alone for a given setting. I could get it up to 90% before distortion started creeping in unbidden. With the internal distortions (bass boost + 'presence' + amp overdrive simulator) turned up, the apparent volume was twice again the output level, probably not in terms of power, but in perception; adding the f/x input supported this assumption by making it seem louder without increasing power. It won't touch the Frontman for output, but it could now serve a small bar stage setting without secondary amping, of fill a studio space to get good distortion with room ambience instead of miking it too closely to get ambience at all. What the non-musical instrument drivers lack in handling the transients of direct instrument output (for realistic live guitar sound) the piezo replaces just fine. With the original cost + other drivers + gasketing and wiring and cabinet screws and hardware, I've now gou about $40 plus 4 hours work invested, and the result is well worth it. I've also now got the experience necessary with the new scrolling jig saw for cutting driver openings to tackle the pair of 12 driver PA cabs I've been planning as well as a high output secondary cab worthy of connecting to the Frontman.
Re: The Martian Stack
A minor hack of peripheral interest to builders, I wanted a stand off with very low floor contact profile, but nothing spiky, as some folks take exception to that when you play at their place. I came up with wall mount coat hooks, the two hook jobs that go onto the wall with a couple screws. So tough I couldn't bend them using pliers, easily installed on any bottom surface, the low floor contact profile is a nice smooth curve. You can tuck them well out of sight, or like you can barely make out here, have them sticking out slightly to give your little Martian pal some toes. For the uninitiated, low floor contact area means less bass sucked out through the bottom/floor and so more available to boom out the front as it should.
Re: The Martian Stack
Re: The Martian Stack
Originally Posted by drmcclainphd
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