Wednesday, March 31, 2010

Why we needed the isolation boxes

I donate time to my church by playing electric/lead guitar on the Sunday morning services (and occasionally in other services). We usually have 2 electric guitarists playing at once, which is the first of two issues. The second issue is that the electric guitarists want to play out of amplifiers, and the amplifiers are causing problems.

The amps are located in a large high-bay (garage-esque) room with 30-40 foot ceilings, lots of concrete, and a big garage door (it is formally a 'prop room', but is used as storage as well). The prop room's walls are shared with walls with the outside hall and with Sunday School rooms, which means that the sound bleeds outside of the prop room, and it is causing complaints. Sunday School classes don't like a big distorted guitar bleeding into their room during morning rehearsals.

The second problem stems from the fact that there are 2 guitarists. A normal person wouldn't see the problem with setting 2 amplifiers next to each other and mic'ing them. But anyone who has any knowledge of musical instrumentation and amplification knows that you will run into 2 problems with this: bleed-over and phase issue. Bleed-over means that you will hear amplifier 1's sound in amplifier 2's mic. One may think 'well, what is the issue? You are mixing them both anyway.", but the problem is that if levels are being increased and decreased for solos and ambiance, the bleed-over will cause problems. If you are trying to elevate a certain guitars sound, you the bleed-over will elevate the other's sound as well.

The phase problems deals with audio engineering and physics. The sound waves that leave the amp do so in a sin wave. The peaks and valleys of the wave need to hit the mic all at the same time. With the bleed-over problem, you will have the sin waves from amp 1 hitting amp 1's mic at time X, and then hitting amp 2's mic at time X + N, where N is a number of milliseconds. While this may sound like a minimal problem, the differences in phase from the mics will cause a weird sound, and the sound will semi-pulsate and get muddy. It is not ideal.

That all being said, I decided to create some isolation boxes to house the amps. This will cause the amps to be contained to their own box, and the sound will be contained to said box. This means: there will be no more complaints from adjacent rooms about the guitar sound, there will be no bleed over from each mic, and we can crank the amps up a little louder, giving them more headroom and getting the tubes a little hotter.

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