acoustics question/help

[messylife]

I am planning on building an isolation chamber for my guitar amp so i can record without the interference of ambient noise getting into the mix and so excessive niose will be contained within. The box willbe constucted with noise dampening materials and fit to seal around the amps face leaving the backs of the speakers free to "breath"

My question is more of an acoustic engineering question than an electronics question, but will this isolation chamber affect the acoustics of the speakers and the sound going into the microphone inside the chamber. Mind that the chamber will be lined with sound danpening foam to cut out the internal reverberations and the box will appox have the dementions of 2 ft by 2 ft by 3.5 ft deep. I would hate to build this and find out the product sound is worse than the original.

Thanks

[sreten]

As long as the amplifier is close miked you'll be hard
pushed to tell the difference between the box and
free spaced close miking.

I don't understand your "Face" and "Back" unless
your miking it from the back.

The way I've seen it done is the amp tilted back at 45
degrees in the box with the mike close to the centre
of the front speaker / one of the speakers.

The box does not need to be any bigger than something
that would allow the above arrangement IMO / experience.

sreten.

[Da5id4Vz]

Do you want as much isolation as possible to keep it out of other mics, or just eneough to keep the neighbors from becoming part of the performance?

I have a friend who after a certain amount of discussion built a chamber. He has a Celestron (sp?) driver at one end and a Senhiser or SM5x at the other. He drives the speaker with some big old Marshal head. I cannot remember what he did for the baffle. Sonex was applied to the inside of the box... I don’t remember how much or where.

The box is the size of a refrigerator and lives under his basement stairs.

The construction is box in a box surrounded by a layer of dense Styrofoam. The door seals between the layers are concentrically smaller to avoid direct path leakage.

After years of touring and studio sessions this is now amongst his favorite places to record. I think he said that he prefers the big iso chambers at the Power Station that will hold an entire Marshal stack, but its 200 miles a way and expensive to rent.

[sreten]

Originally posted by Da5id4Vz
Do you want as much isolation as possible to keep it out of other mics, or just eneough to keep the neighbors from becoming part of the performance?

I don't understand this.

What other mikes ?

I don't see how you can use the box playing with other people,
well you can via a monitoring system, in this case its enough
isolation so you can't hear the box under the monitoring.

I thought they were used simply to keep the level down whilst
you take the (presumably) valve amp and speakers to their limits.

Generally used for recording single guitar tracks.

The biggest size you'd need is something that can
hold the amplifier tilted and twisted 45 degrees IMO.

sreten.

[messylife]

sorry, i ddin't mean to confuse about using two mics - only one mic will be close miked to one of the speaker cones inside the enclosure. i was just tyring to make the point that the planned enclosure will only seal around the front of the amp leaving the back of the amp and speakers for that matter open to free atmosphere. the isolation chamber does not completely surround the entire amp.

The purpose of the box is to keep the neighbors music out from my recording and also to help dampen the overall noise my amp creates (but that is only a secondary goal to getting a clean recording environment.)

the question i was posing is if there is any internal acoustics i should worry about. when discussing this project with my father who is an architech, he had warned me there might be possible problems with it but i didn't think so since i was close miking the amp with my condensor mic. Just to be sure, i wanted to see if anyone who has more experience with acoustic engineering had any concerns for my design. thanks for all the replies - unless i get some negative feedback, i think its a greenlight to start building.

if anyones interested, i will be using mdf, quiet stone drywall (5/8) and acoutic noise dampening foam for the inside lining. i will post a picture of the finished product with an outcome review also if anyone's interested. thanks again

fa

[sreten]

Now I understand the half box idea I've never
seen it, its more like an acoustic front hood.

I'd suggest a 45 degree angle with a tight fit around
the sides against some foam would work best, you
don't wan't a surface parallel to the cone.

Low frequencies would still get through to the
mike and some external sound through the cone.

sreten.

[messylife]

thats a great idea about slanting the face of the box, i didn't think about that, that should redirect any bounce back, if any, away from the mic. thanks sreten.

[sreten]

Well I really meant the amplifier at 45 degrees into a corner.



sreten.

[messylife]

the only problem with that is that my guitar amp has 4 speakers all at the corners and for me to best mic the amp i need to point right at the cone at 90 deg. so my revised design would be to have two sides and a top running with the amp and the back face slanting down. let me know if you have any other suggestions. thanks again

fa