Your guitar cabinet is too loud. You don't want to turn it down. So what do you do?
There are two problems in recording the electric guitar. One is interference, the other is that it's so damned loud!
If you have a soundproofed studio, or live in the desert, then making as much noise as you like isn't a problem. But for the rest of us it certainly is.
Recording engineers have long sought a way of recording electric guitar successfully at a low volume level.
Here are some possibilities...
- Turn it down!
- Use a less powerful amplifier so that it produces the same amount of distortion at a lower level.
- Use a 'soak' on the output of the amplifier and DI the signal - the soak is a resistive load that sucks up the power but produces no sound. A further resistor network feeds the signal to the recording equipment.
- Use a digital modeling processor to mimic an amplifier and speaker.
You have probably tried all the above alternatives and found that none of them really work entirely.
But there is a further possibility - if you could enclose the cabinet in a soundproof enclosure, together with the microphone, then you could play as loud as you like.
Sounds tempting, doesn't it?
But it needs thinking about before rushing into construction...
Let's consider an approach that will definitely not work - fix a boundary effect (PZM) microphone to a thick piece of wood and fasten it directly in front of the speaker at a distance of zero feet and zero inches (zero meters, if you're metricated).
Clearly this is not going to work. As the cone of the speaker pushes forward, it will compress the air in front of it that is now trapped. It will compress the air, and air - being springy - will push back.
In fact the motion of the cone will be so restricted that you will probably get hardly any sound out of it at all. But try it - everything's worth a try. Just don't blame me if something catches on fire.
So clearly, the cone needs space to push air into, so there is a larger volume of air and the amount of compression is less.
The trouble is that the volume needs to be really big. It's not simply a matter of making the enclosure as big as the cabinet. It will have to be much bigger so as not to affect the sound quality.
A further option would be to put absorbent material in the enclosure. You could stuff it full of mineral wool, but this causes two more problems. One, where do you put the microphone without it being blocked by the mineral wool? Two, if the mineral wool were packed in tightly to absorb more sound, it would become a barrier to air motion in its own right, defeating the object.
So it all seems hopeless then?
Well actually no. You just have to realize that the enclosure needs to be very large, and it needs to be lined with absorbent materials, not stuffed. The right amount of absorbent would be determined by experiment.
So a spare room would be ideal for the purpose. And if you were really into guitar recording, it wouldn't be too much trouble to set up. It would repay itself every time you got an inkling that you wanted to plug your guitar in.
How you get the signal from the guitar into the room is another question, for another day...