Drew's diary, update

drew.n · Post by **drew.n** » Tue Jul 12, 2005 7:26 am

Goals
A small single multi-purpose room for recording/mixing and also doing some sound to picture work. Drums, bass, elec guitar are DI (and can be in another room if more musicians and we can't fit), some acoustic/vocal stuff will be on mic.

Soundproofing
Incoming: Quite end of town, near the outskirts, noisiest thing is occasional light aircraft or glider towplane. Some distance from a main road, completely inaudible with the windows closed. Willing to schedule mic sessions for quiet periods just to make sure, but it isn’t a problem.

Outgoing: Not going to be monitoring at high volumes for long periods. Instruments are generally not going to be loud. Neighbours are just about far enough away not to bother,

Construction:
Construction has started, but has not advanced to the point where I can’t move a door or window.

UK standard construction which means, double skinned, (outside brick /middle cavity with rockwool / inside breezeblock. (makes further inner walls a no-no, but should be sufficient for my needs if done properly.

1 existing window in the east wall is non-negotiable, (movement or bricking up has a WAF 0.0), another window is required in either the north or west wall and has to be big enough to climb out of (local fire regs). Access door needs to be somewhere in the south wall.

Floor – oversite concrete slab, sand, insulation, isolated 150mm slab on top, with further insulation/isolation around the edge.

Ceiling plasterboard on joist (could be on RC), new attic space above, rockwool layer, fibreglass over that to a depth of 1m (ish). An alternative could be gypsum top and bottom of joists, rockwool between, loads of fibreglass on top with a vented roof over.

Dimensions:
W 2.85m x D 2.97m x H 2.3m

Budget. About £15K from the ground up.

Rooms near: kitchen to the east, conservatory to the south, both unoccupied during recording.

Questions:
I’m planning dog-tooth treatment to the east and west walls. Is this as effective as a “real” trapezoid wall?

Also thinking that some of the dogtooth could be built into a bookcase, any opinions on this?

Back wall is going to be an 8” basstrap, with superchunks or cross-corner fibreglass in the corners.
Can I “run them into each other” if you see what I mean (see pic)

Acrylic window diffusers, will they work? Is that design ok? I’ve run some ray tracing tests and can’t see speakers from my seat position.

The big one:
Given the restrictions, (size, east window fixed, west window and door movable, not losing too much floorspace) has anyone got any better layouts?

drew.n · Post by **drew.n** » Thu Jul 21, 2005 12:37 am

New version of layout. Rotated 90 degrees with some hopefully crafty touches:

Acrylic diffuser over west window.

Desk shape designed to stop reflections, but still allow two people to work at the same time looking into the corners, (not for audio work).

Door built into south slotwall.

Sliding bass trap panel over east window. Should hide behind the basstrap on the other side when not in use. I'm planning on trying to find an old sliding door mechanism to slide it across and out. Failing that I'll just make it on a movable stand and heave it across.

Instruments would be kept round the edges, (guitars, elec drums, keyboard), but could easily be "jet fightered" in a couple of minutes.

knightfly · Post by **knightfly** » Fri Jul 22, 2005 8:20 am

I was going to suggest rotating, you beat me to it. Your questions -

I’m planning dog-tooth treatment to the east and west walls. Is this as effective as a “real” trapezoid wall?

Not if you make the "teeth" smaller than around 3-4 feet; too small and you just get "acoustic averaging", doesn't work to as low a frequency (wavelength dependent)

Also thinking that some of the dogtooth could be built into a bookcase, any opinions on this?

If the "teeth" are deep enough, might be OK; I'd watch what goes on the shelves though, might get some specular early reflections if you're not careful.

Back wall is going to be an 8” basstrap, with superchunks or cross-corner fibreglass in the corners.
Can I “run them into each other” if you see what I mean (see pic)

Sure, no problem.

Acrylic window diffusers, will they work? Is that design ok? I’ve run some ray tracing tests and can’t see speakers from my seat position.

There are even commercial micro-perforated absorbers, RPG if I remember right. Might want to re-direct them to the ceiling, if it's more absorbent.

The big one:
Given the restrictions, (size, east window fixed, west window and door movable, not losing too much floorspace) has anyone got any better layouts?

Looks OK to me, John may have other ideas... Steve

drew.n · Post by **drew.n** » Sun Jul 24, 2005 6:50 am

Thanks for the advice.

I found a calc for microperf absorbers on the sheffield university site,
Extremely impressive for a piece of plastic with holes in. Absorbtion plus daylight plus reflection into the ceiling, all in one, bargain.

For those with Dremels and spare time on your hands it's here:
http://www.shef.ac.uk/acoustics/html/absorber.html

Apparently it'll work with fabrics as well, looks like the right fabric with the right spacing would be pretty good on it's own. I wonder how the perforated plastic they wrap bread in would do? off to google to find specs...

Another useful thing I've found, a virtual ripple tank, Great demo of wave phenomena. I've been using it to try out roughs for HVAC ducts.

http://falstad.com/ripple/

Hey Steve, you'll be glad to know I'm investing in a copy of Cara. I'll be using it at home and work if we ever get round to converting the safe.

Meanwhile, in goes the first footings

drew.n · Post by **drew.n** » Tue Aug 02, 2005 4:17 pm

Latest pics. Still nowhere near the interesting bit yet.
As you can see there are currently no problems with early reflections, but isolation is an issue.

The blue membrane is damp proof and radon protection, which is statutory in this area on all new building, so the music room will be protected whereas the rest of the house isn't

I've gone for an isolated slab rather than full floating, which seems like best bang for buck given the room useage. Under the membrane there is insulation, and also round the edges. The stuff round the edges is more compressable then the substrate to aid isolation between slab and walls.

The Building inspector, he say "YES",

so onto the walls.

Since I last posted there have been some interesting developments at work. The obstacles to us converting the safe may have been removed, so the conversion could be a viable option when budget allows. The safe is about 2.5m wide (with a 10degree splay end to end) and 10m long 2.2m high. 70cm thick concrete walls and a .7 tonne door means isolation is not really an issue. See how it goes.

drew.n · Post by **drew.n** » Wed Aug 17, 2005 7:33 pm

Still in the dull bit, but now I have walls!

The inner wall is seperate and the gap stuffed full of mineral wool, the lintels are two L shaped pieces rather than a single hat shaped piece. Builder gave me some funny looks over that one

Roof time.

Post by **sharward** » Thu Aug 18, 2005 12:39 am

Very nice work -- the addition looks like it will "blend right in" with the rest of the building.

Keep those pics coming -- it's always a pleasure and an inspiration to see actual progress on projects!