Closed Back Cabinets & Spring Reverb...

http://www.andrewwasson.com/

Andrew Wasson of Creative Guitar Studio answers questions from off of his Guitar Blog website...

Q). I own a 80 watt solid state amp with a 12" speaker that has an open back and I was wondering if I closed it up if this would improve the sound projection from the front at all? Also, when I bump it, or move it when it's on, it makes a crazy crash-banging sound! What is that sound, and it is bad to hear? Thanks!
- George -- Bloomfield CT. United States

A). On your first question, closing up the back of the amp would definitely improve the projection of the amp's sound. Except for the slight blockage of the speaker's magnet, the open back design (also called non-enclosed cabinet) projects the amps sound-waves both forwards and backwards. However, an enclosed cabinet causes the sound to change to a forward effect as well as alter the sound waves themselves because the speaker will actually move back and forth at a slower rate. This results in better projection, better bass response and better overall speaker efficiency. The main reason we see so many open back amp cabinets is because they add brightness. If you want to try out your amp as a closed back, try taking a piece of ½" plywood and close up the back in a temporary way to see if you like it. But, one word of caution, don't try this with a tube amp, as you'll likely find that it will over heat. As for that crazy crash-banging sound from your amp upon moving it while it's on, that's the sound of a "Spring Reverb Tank." The tank has long springs and a small sensitive pick-up in it. So, any sudden shock will cause the sound you described, but it's not overall bad for the amp!

Thanks for writing in.

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[Charlesdance]

When I become president of my country I shall name Andrew the Minister of Guitars.

[r3ap3rjay7]

great video! I always wondered why my amp did the crash sound as well hahaha now i know ^_^

Keep up the great work Andrew :)

[BillEvans1956]

Yeah. With a tube amp, surely closing the back would also increase the vibration effect on the tubes and you might get more tube rattle and maybe eventually failure of your tubes? Good post.

[humbecker]

thanx again