Home recording studio in the attic.

#1

Hello!
I'm building a studio in the attic. I'm not a professional, but I know how important it is to have good acoustics in the studio, a flat response. I read the instructions for the acoustics treatment of classical rectangular rooms (SBIR, 38% listening position, center of the room - bass cancellation, bass traps, absorbing acoustic panels, diffusers, etc.). I am writing this post for the atypical size of the room. Can you advise me on problems with the acoustics of this attic? I am sending a drawing of the attic with the layout of the monitors (Yamaha HS7) and the listening position. The initial treatment of acoustics would be to make absorbent acoustic panels for the first reflections (ceiling, side walls, front wall), vertical corners of the bass trap. I don't know what to do with that chimney which can be a problem because the listening position is between the monitors and the chimney. Apply a diffuser to the entire chimney behind your back? The back of the room is a combination of absorbing acoustic panels and diffusers? On sloping walls there are Velux roof windows, walls and ceiling one plasterboard 12.5 mm with mineral wool 100 mm, concrete floor with carpet. I will be happy for any advice. Excuse me my english is very poor.

#2

Congratulations on starting your project and welcome to the forum. This shape of room is great fun, and in my experience can give recording acoustics that are interesting in a very good way. Some aspects of it are also beneficial to a mix room. On the other hand, it makes predicting room modes difficult!

A couple of things spring to mind;

1) With the monitors that distance from the front and side walls, you will get terrible SBIR; I've put in what I think are your values to here. Nulls from front and side of 57Hz and 59Hz respectively. These add up. Right in the kick drum and bass guitar fundamental range. Ouch.

SBIR calculator here; http://www.tripp.com.au/sbir.htm

2) The chimney is too close to the mix position for diffusion. From memory, diffusion needs at least 10 feet distance to start being effective. I'd personally treat it like a first reflection point. Absorption with extreme prejudice!

I have a thread on a smaller but similarly shaped room, you may find it useful. I'll be doing some significant updates soon you might be useful;

https://www.digistar.cl/Forum/viewtopic.php?f=5&t=8

Cheers,
Jennifer

#3

Gilmour74 wrote:Source of the postI don't know what to do with that chimney ...

If you cannot remove the chimney then Jennifer's suggestion will be the next best thing you can do: treat it like a first reflection point.

endorka wrote:Source of the postFrom memory, diffusion needs at least 10 feet distance to start being effective. I'd personally treat it like a first reflection point.

The theory as I remember reading it is that you do not want any sound other than the original, direct signal returning to the listening position any earlier than 20ms after the direct sound gets there. That works out to be 7 metres, so the nearest you could have a wall behind you with diffusion is 3,5 metres.

#4

Thank you endorka and Starlight for valuable information, I follow your great projects.
Monitors should not be on an axis 45 ° from the corner. My monitors are located on this axis, which is not good, they should be from the inside or outside of this axis. I think that's why SBIR is doing so badly. New information for me that diffusers work at a greater distance of about 10 feet. The manufacturer recommends placing monitors 1.5 m or more from the rear and side walls. In my design, the monitors are 1.5 m from the back wall, in fact 0.9 m from the back sloping wall. I read somewhere, SBIR in rooms with sloping ceilings is different from ordinary rooms. Yamaha HS7 monitors rear ports not suitable for soffits? What would you suggest my monitor layout?
Thanks again for the advice and posts.

#5

Gilmour74 wrote:Source of the post... the monitors are 1.5 m from the back wall ...

The language of the geography of a room is this: the wall you are looking at, the one where your monitors are, is called the front wall. The rear or back wall is the one behind you, which will be covered by a large and deep bass trap.

#6

Gilmour74 wrote:Source of the post Thank you endorka and Starlight for valuable information, I follow your great projects.
Monitors should not be on an axis 45 ° from the corner. My monitors are located on this axis, which is not good, they should be from the inside or outside of this axis. I think that's why SBIR is doing so badly.

Seems logical. If they are on axis 45 degrees from the corner it means the distance from the speaker axis to the closest side & front wall is the same, so presumably you'll have the same SBIR null being added to twice.

The manufacturer recommends placing monitors 1.5 m or more from the rear and side walls.

I've seen and measured this being done successfully in another studio, and it was achieved by having the monitors sufficiently far away from walls that the SBIR dip was below the frequency response of the monitors. Yours apparently go down to 43 Hz; 1.5m gives a null at 57Hz, so you'd have to move further from the front wall to get the null below it. Check the calculator I linked to above to determine this.

Another option would be to move the monitor as close to the front wall as possible so the SBIR moves into much higher frequencies, where it is less harmful. This worked well for me in dealing with SBIR, but brought some other problems with it too, perhaps related to them being in a window bay with fairly complex shapes and reflection points.

How you would get the best distance from side walls without ruining your mix position setup is less clear.

I read somewhere, SBIR in rooms with sloping ceilings is different from ordinary rooms.

Different, certainly. Different in what way is something I've been trying to figure out for close to five years :-)

It gets messy. Moving speakers is not as predictable as with straight walls. In my room. as you move the speaker closer to the sloped ceiling, I think it gets more complicated because not only is the speaker getting closer to the surface behind it, it is also getting closer to the surface above. If the entire wall was sloped this may not be much different from a normal wall, perhaps the complexity comes from having one part of wall vertical (the knee wall portion) and the other sloped (the ceiling)

I don't have any simple answers sorry!

I think the best solution for my place would be soffit mounting the speakers, and I am certainly going to try this at some point in the future.

Yamaha HS7 monitors rear ports not suitable for soffits?

Good question, have a search around, I think some people have soffit mounted rear ported speakers. Mine are Genelec 8030, rear ported, and Genelec say it is possible with them.

Cheers,
Jennifer

#7

Hi
I have successfully soffit mounted rear ported (well actually a rear passive radiator, but much the same) speakers - Mackie HR824. The key was having more space behind the speaker and damping it with Rockwool. I guess if your speakers are small and rely on the bass ports a lot for their low end response it might not be so successful. Worth an email to the technical department of the manufacturer?

Gareth

#8

Do you have any photos or other data of that setup Gareth? Would be very interesting to see.

The official Genelec instructions for flush mounting the rear ported 8030;

: 8030 flush fitting - updated with all dimensions.jpeg (46.59 KiB) Viewed 38147 times

: 8030 flush fitting - updated with all dimensions.jpeg (46.59 KiB) Viewed 38147 times

I've attached the Genelec documentation on flushmount kits for their bigger speakers that have a cover with an elliptical cutout to go over the speakers.

Stuart had this to say about those;

I know that Genelec sells a "soffit mount" box that has the speaker poking half way out the wall, as you are showing in your model, but to be honest I've never really understood WHY they do that! My guess is to get decent air flow around the speaker, for cooling, but there are other ways of doing out. My concerns with it sticking out so far from the wall, include edge diffraction, SBIR, and other potential issues. It makes more sense to have it fully flush.

#9

Thank you for the information. Do you know software Olive Tree Lab Suite? I tried to simulate in software comparing 4 room types. Classic room, classic room with chimney (obstacle), attic room (sloping walls), attic room (sloping walls + obstacle chimney). Range from 25 Hz to 10 kHz. Exactly as endorka wrote "It gets messy". Sloping walls and obstacles create different acoustic behavior. I did not manage to exactly set the different absorption and composition of materials (plasterboard, chimney and floor) in the demo version, so I do not believe that the simulations would show exactly my project. In each case, in four columns are the same material settings 10 cm mineral wool and one board plasterboard 12.5 mm. The simulations are without any modifications acoustic absorption panels, diffusers, bass traps. The results are interesting.

#10

If I moved the speakers away from the front wall, I would get close to the center of the room with the listening position (green diagonal lines on the original floor plan - low bass). This condition may not apply if there is an obstacle chimney.

#11

Have you tried moving the speakers very close to the front wall, say a couple of centimetres away?

#12

[quote="endorka"]Source of the post Do you have any photos or other data of that setup Gareth? Would be very interesting to see.

I have a thread from a few years ago on the John Sayers forum with a fair bit of detail. I’m not sure I did it perfectly correctly, but the results sounded great. The problem I had was I had a fair bit of bass coming out the vent holes (where heat from the speaker and amp should vent) which makes me wonder whether sealing the sides of the soffits was a good idea. Hard to say now as it’s all dismantled and I’m building a new room...

http://www.johnlsayers.com/phpBB2/viewt ... ck#p142698

Gareth

#13

Endorka studio is not finished in the reconstruction yet. I can only simulate in software. I moved the monitors 20 cm to the front wall, in PDF comparison. This position is better, 63 Hz improvement; 125 Hz, deterioration 160 Hz, improvement 400 Hz; 500 Hz; 1kHz; 2 kHz; 2.5 kHz; 3.15 kHz.
Garethmetcalf great project thank you for the type.
I will go to speaker stands, when there are bad results, I will consider soffit mounted.

#14

endorka wrote:Source of the post Another option would be to move the monitor as close to the front wall as possible so the SBIR moves into much higher frequencies, where it is less harmful

Which frequencies are more and less harmful?

#15

Get the frequency of the SBIR dip as high as possible, by moving your speakers as close to the front wall as possible. There may be a limit to this due to rear ports or other factor - check the speaker manual for this. I had my Genelecs only about 1 cm away.

I understand there are two reasons for this;

1) Higher frequencies are directional, so a greater proportion of them come out the front of the speaker than the rear. Less sound at the high frequencies going out the rear of the speaker means a less severe SBIR dip. In contrast, low frequencies are pretty much omnidirectional.

2) Higher frequencies are easier to absorb and reduce with room treatment.

That's the theory, and it worked that way in practice when I tried it.

Cheers!
Jennifer

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