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Looking for a fun, functional, low-cost project to knock out during the holidays? Check out this clever repurposing piece from the pages of MAKE Volume 10, offered up by David Battino with help from George 'the Fat Man' Sanger.
The Sweet Sound of Particleboard
Beef up the tone of open-back amps with a little thrift shop help.
By David Battino
After transforming a record player and some plumbing parts into a spinning speaker (see MAKE, Volume 05, page 24), George "the Fat Man" Sanger is back with a new way to enhance your guitar sound.
His Goodwill Amp Enhancer is a DIY version of the commercially available Enhancer, which beefs up the tone of open-back amps by redirecting the "lost" sound to the front.
The nicely finished commercial versions start at $150 (soundenhancer.com), but the Fat Man built his enhancer out of a $15 computer desk he scavenged from a thrift shop. "It took just an hour or two," he reports, "and adds wonderful tone to my amp."
How It Works
The Sound Enhancer site details the science involved, but in general, the Fat Man explains, an open-back amp is a design compromise.
"In theory, a perfect speaker box would be a speaker mounted in the middle of a wall of infinite size, because that would let the sound from the front reach your ear without having been partially cancelled by the inverse sound from the back," he says. "Mom won't let us build anything infinite anymore, not after what happened last time, so we approximate the infinite wall by putting speakers into sealed boxes, also known as infinite-baffle enclosures.
"Unfortunately, infinite-baffle enclosures make it really hard for the speaker to move, so the sound is quieter. And of course, quietness is not very rock 'n' roll, is it? So designers make a lot of amps louder (and a little funny-sounding) by opening the backs.
"This speaker stand bends the back sound around a corner, which makes it even less like the front sound, and then sends it out the front, where its slightly altered power is added to your already Majestic Volume in a rich and tonally pleasing way."
In addition to reinforcing the sound, the Goodwill Amp Enhancer points the amp at your head, letting you hear yourself louder than, and before, your bandmates do. That helps you play better, and your bandmates don't hate you for playing too loud.
MATERIALS
Donor furniture with big sides (e.g., a printer stand or computer desk, ideally with casters), taller than your amp (hip height is great), and 1¼ times your amp's depth
Other wood (possibly salvaged from the donor), several pieces cut so their lengths match the width of your amp minus about 1". Their widths must add up to approximately 1 amp depth plus 1 amp height. They need to be thick enough to take a ½" screw.
Particleboard screws about 1½" long
Saw Circular is good, but a handsaw will do.
Screwdriver
Caulking gun and caulk
Hot glue gun and glue
Weather stripping twice the amp height, twice the amp depth, and once the amp width
Weather-stripping adhesive
DIRECTIONS
Step 1: Ready the donor. Pull the sides off the donor, place them on the floor, and lay your amp on its side in the tipped-back position you want it to sit on the stand. The back of the stand needs to rise above the opening in the back of your amp to seal it off, but it mustn't block any essential controls. The bottom-front edge of the amp will come right to the front of the stand.
Step 2: Make the side panels. Mark the outline with a Sharpie, and saw along the resulting L-shaped line. Now your side panels are done, and they should look something like that one particularly odd block
in the game Blockhead!
Step 3: Make the floor and back wall. Make a floor and back wall for the amp by hot-gluing the other wood between the two side panels. You may need one additional narrow piece to bridge from the top of this back wall to the spot on your amp where the open back stops and the controls begin. Don't worry if you mess up; hot glue can be broken free and redone easily.
Step 4: Make it permanent. Once it looks right, make it permanent by sinking some screws in from the sides. Caulk up the cracks, then glue the weather-stripping to the edges that will touch your amp. "This stand will make your amp sound so much better," the Fat Man promises. "It has to be heard to be believed."
Sound comes out the back of the amp and is forced out the front of the stand. Beyond that, the shape of the barrier isn't too important. Be sure that the horizontal bit hits the amp's back above the speaker opening and below any controls.
Hear the Goodwill Amp Enhancer: makezine.com/10/diymusic_amp
More from the Fat Man: fatman.com
About the Author:
David Battino is the audio and digital music editor for O'Reilly's Digital Media site, the co-author of The Art of Digital Music, and on the Steering Committee for the Interactive Audio Special Interest Group (IASIG). He plays Mac, PC, and keyboards. With his wife, Hazuki Kataoka, he also writes, publishes, and performs Japanese kamishibai storycards. More at www.batmosphere.com.
A normal closed box speaker is not called an infinite baffle. An infinite baffle is where the speaker is mounted on a baffle that is _effectively_ infinite.
Usually it's either an extremely large box whose resonance doesn't affect the driver's motion, or in some cases a wall between rooms, etc. Its main goal is to keep the back wave from interfering with the front wave, and should not damp the driver's motion.
A sealed box, doesn't make a driver harder to move either overall, it just changes the resonance. Think of the enclosure of the box like a trampoline, not like a crash mat. When you apply energy to it, it comes back out. at some frequencies, this will cause more sound than you would get with an infinite baffle, and at other frequencies you will get less.
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But, but... I have a 4x12 slant cab... It'll never fit :(
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