Home studio planning: absorbers and tricky diffusor question

Hello all! Thanks for an inspiring forum. I have been using a room with crappy acousics upontil now, but now Im planning of turning half of a basement room into a "home recording studio". Som background info: I mostly make music with computer software and MIDI. if there are any guitars, its more often online collaborations, so I'll get the files... Never the less, these are the studio-specs: 1. Most used for mixing/arranging and playing midi. 2. some electric guitars, -lined. 3. E-Drum kit is on my wish list....a small one ;) 4. vocals will be recorded. So...I will not be too loud, no live drums or so.... Budget? I guess about 1000 USD or so.... my main goal is to achieve a nice, creative room, with "at least some improved" acousitcs....I might add that I really love to make stuff by my self, so its basicly jsut fun..and that internest is probably what made me choose the diffusor design ;) Room dimensions are 5,5 by 3,6 meters, and unfortunately only 2,3 m high. What you see on the pictures are the corner absorbers, the cloud, and the wall absorbers, together with the elliptical design diffusor/slat resonator. 3 existing walls are massive "light concrete (dont know english for this, sorry..." and very good sound isolation. I can turn up the volume alot in the basement and not hear a thing upstairs, except from the leaking through the stairs. I will then build a double leaf wall, with two 3" thick steel framed walls: One sheet of plywood and two sheets of plaster facing the studio, and on the other side, just one sheet of ply and one sheet of plaster. I will seal off any slots with sealant. I have two old doors from apartments, with I think .40Db on them or so... one for each leaf. The doors will be placed at teh "cut of wall" in the pictures below. The absorbers will be made from 120mm (5" ) fiberglass insulation material, and coated with spray-glued fabric and flame protection. (ive seen a few good threads about this!) And, to the tricky part. Diffusing... I checked out, and my listening position will be about 3,4 metres from the back wall. My first thought was skyline diffusors, but then.....ther would be a LOT of wood cutting :D ok, perhaps there is still the opportunity left if you guys think my ideas here are crap :) The idea I have is to make an elliptic shape, and then have stripes (2-4" wide)of MDF mounted as in the pictures. The varying depth of the resonating body (elliptic) and varying distance between the stripes will create a multi band resonator. The construction will be places between the corner absorbers and be about 0,5 meters deep at the deepest (in the mid of it) and roughly 2m wide. I have also som questions about the properties about the slots on the diffusor, but perhaps I should ask that in the acoustic forum? Thank you in advance...i hope this is good enought info. So, do you guys think this could be something to start with? best regards from sweden! /Tomas PS: i will link in the pics since I dont have access to the files on my computer....i will upload them later! hope its OK....

Full range diffusion is not recommended on rear walls closer than 3 m to the listening position. The space will act as a Helmholtz absorber. Think about shallow polycylindrical diffusors or accept the work in making Schroeder type diffusers if you are committed to diffusion on the rear wall. Andre

AVare wrote:

Full range diffusion is not recommended on rear walls closer than 3 m to the listening position. The space will act as a Helmholtz absorber. Think about shallow polycylindrical diffusors or accept the work in making Schroeder type diffusers if you are committed to diffusion on the rear wall. Andre

Ok, thanks frp speedy reply! I think that it would be good with a helmholtz in that space? If I make it a bit less deep, it will be a little more than 3m away from me... On the other hand, schroeders look awsome too ;) :D Still go for schroeder/polycylindrical even if the distance is 3,2m?

Still thinking, but my first thoughts are for a shallow Schroeder type with absorption behind it. I don't know what your budget or desire for DIY (Do It Youself) is, but commercial product that would be suitable is the GIK Acoustics D1 diffusor. The side wall/ceiling corners could use additional absorption. The amount of absorption could be excessive in the high end, so try some with a plastic or similar cover to reflect highs for non initial reflection point absorbers. The ceiling height is a concern. What is the construction of the ceiling and how much can you modify it? I am thinking in terms of either fine tuning it to be a panel absorber or build in Helmholtz absorbers at the first axial mode frequency. Andre

AVare wrote:

Still thinking, but my first thoughts are for a shallow Schroeder type with absorption behind it. I don't know what your budget or desire for DIY (Do It Youself) is, but commercial product that would be suitable is the GIK Acoustics D1 diffusor. The side wall/ceiling corners could use additional absorption. The amount of absorption could be excessive in the high end, so try some with a plastic or similar cover to reflect highs for non initial reflection point absorbers. The ceiling height is a concern. What is the construction of the ceiling and how much can you modify it? I am thinking in terms of either fine tuning it to be a panel absorber or build in Helmholtz absorbers at the first axial mode frequency. Andre

Ok, yeah, I think that I'll be doing most of the stuff myself...i think its some sort of therapy ;) The ceiling is giving me some headache, yes. The floor is concrete, and the ceiling is actually som kind of sandwich: 3 inch concrete, styrofoam, conrete. So the sound isolation to the rest of the world is OK, but its really giving me no freedom at all when it comes to moficiations. perhaps som kand of helmholtz slot resonator above mixing poisition, tuned the critical frequency ? I checked the link..not too expensive. I'll look for them in sweden to see them in real life :) So absorbers where the side walls meet the ceiling? OK! And the need for plastic on those are excellent in terms of dust protection :D The vertical ones are planned without any plastics. Thank you again, for your quick replies. I am a total newbie at theese things...and yes, it is possible to read and learn..but before builiding somwething, it is so great to ask someone. :)

For such a small place I would only use diffusion (QRD's) in the back wall and eventually on first reflection points mixed with absorption

perhaps som kand of helmholtz slot resonator above mixing poisition, tuned the critical frequency ?

Hmmm I don't see much benefit from this.

andrebrito wrote:

For such a small place I would only use diffusion (QRD's) in the back wall and eventually on first reflection points mixed with absorption.

After thinking about it, Andre Agrees with Andre :D Andre

AVare wrote:

andrebrito wrote:

For such a small place I would only use diffusion (QRD's) in the back wall and eventually on first reflection points mixed with absorption.

After thinking about it, Andre Agrees with Andre :D Andre

ok, thanks Andre(s) :D Is this QRD a "skyline" type or ... ? :)

It's a Quadratic Residue Diffuser, like this....

andrebrito wrote:

It's a Quadratic Residue Diffuser, like this....

OK, thanks. Is this one better than a skyline type, or are both valid choices? Thanks for your effort :) /Tomas