Building Control/Rec Room - Help with Acoustic Treatment

[musicman0318]

Hello!

I'm planning on building a small control/recording room (23 m2) on the first floor of my house and would absolutely need your professional advice on how to treat it acoustically!
As I already mentioned, its going be used as control and recording room simultaneously, as well as a rehearsing room for my band. My goal is to run a professional recording studio in the future, so decent acoustics for these application is a must. In best case, I even want to be able to record a small drumset if necessary in this room. I provided pictures, a rough sketch up model and a first room measurement (REW) below. (Unfortunately I wasn't able to attach the .spk and .mdat files so I refer to a Dropbox link below)

So far as it is possible, I want to build the acoustic treatment myself (Reflection panels with rockwool, basstraps in all the corners by stacking rockwool packets to the ceiling). However, regarding diffusors I will likely have to by those.

THE ROOM: (SketchUp model Dropbox link )

-LENGTH: 5,4m
-WIDTH: 4,15m
-HEIGHT: 2,28m

It has a sloped ceiling on the shorter sides of the room. The two windows on one of the longer walls were covered with 13 cm of rockwool and 2,5 cm of drywall (reason is soundproofing).

Long wall 1: exterior brick wall (2 covered windows as mentioned above)
Long wall 2: interior brick wall; door;
Short wall 1: sloped ceiling; 2,5 cm drywall - 13 cm rockwool - 3 cm wood wool insulation panel - 1 m gap - roof truss
Short wall 2: sloped ceiling; 3 cm wood wool insulation panel - 1 m gap - roof truss

It's an old house and nothing is straight and absolutely symmetrical. Even the SketchUp model isn't perfectly correct, there could be a difference of 2 or 3 cm at some measurements. Thought i should mention that.

All objects in the room can be moved. For now I plan to have a small desk with computer monitors, a siderack with my interfaces etc, my Neumann KH120A monitors, guitar amp head and cabinet, couch. (Placed like in the SketchUp model.

Regarding soundproofing...my nearest neighbours are 20 meters away. At about 95 dbSPL in my room, there is no problem. When I crank up my amp (and easily get 110dBSPL), thats probably to loud for my neighbours at certain times. So if theres any relatively cheap way to tame the sound going outside even a bit, I would be open to that. But soundproofing is not my first priority here.

Here are pictures of the room:

long_wall_1.jpg

long_wall_2.jpg

short_wall_1.jpg

short_wall_2.jpg

REW MEASURING: (file -> Dropbox link )

When I measured, there already was one package of rockwool in each corner, as you can see in the pictures.

freq_response.jpg

waterfall_diagram.jpg

So hear are my specific questions:

- Is my current placing of items effectiv or would you place anything different? (Distance between wall and monitors? for instance..)

- Where and how should I place my reflection panels for early reflections, what should the size of those be, and how should I treat the wall behind my monitors?

- Where else should I put reflection panels and diffusors? And which diffusors should I use?

- Are there any relativeley cheap ways to do additional bass trapping and would i need it at all?

- Where should I mount my monitors? Should i build my own monitor stands or should I buy one of those?

- Are there relatively cheap solutions to sound proof my room a bit more? Would decoupling my amp and monitors help it and how should I do that?

- Is there a cheap way for air conditioning? it would need just a little cooling in the summer. I feared that leading the air outside with those systems would worsen the „soundproofing“?

- Should i use one of this power conditioners to hook up all my equipment? (Speakers, Interface, Computer, Monitor, Amp..etc..)

BUDGET:

I’m aiming for around 500€ as I want to build the panels and bass traps in the corners myself. If a couple hundred more would increase the quality of the acoustics in my room extensively I would be open to that though.

I know, this were many questions. I read the forum rules and provided as much details as I could think of. I hope it is ok.

I’m looking forward to your replies and thank you for helping us guys here in the forum. This is really awesome!!!!

Chris

[Soundman2020]

Hi again Chris! It looks like your thread "slipped through the cracks", and I had not seen it to reply to it. Sorry about that!

I'm planning on building a small control/recording room (23 m2) on the first floor of my house and would absolutely need your professional advice on how to treat it acoustically! As I already mentioned, its going be used as control and recording room simultaneously, as well as a rehearsing room for my band. My goal is to run a professional recording studio in the future, so decent acoustics for these application is a must. In best case, I even want to be able to record a small drumset if necessary in this room.

OK, I noticed that all your questions so far are about treatment of the room (acoustics inside the room), not about isolation, so I'm assuming that: 1) you don't need much isolation, and/or 2) that you realize that isolating a room on an upper floor is very hard to do, and very expensive. Is that correct?

So far as it is possible, I want to build the acoustic treatment myself (Reflection panels with rockwool, basstraps in all the corners by stacking rockwool packets to the ceiling).

Excellent! But if you build a panel with Rockooll, it won't be a "reflection" panel: it will be an "absorption" panel.

However, regarding diffusors I will likely have to by those.

The room is likely too small to be able to use diffusers. Your only real option for treatment in such a room, is absorption.

It has a sloped ceiling on the shorter sides of the room.

That's a strange shaped room: not so easy to treat, but not impossible.

But soundproofing is not my first priority here.

Good! Because that's hard to do when you are not at ground level, and expensive...

- Is my current placing of items effectiv or would you place anything different? (Distance between wall and monitors? for instance..)

Your minitors should be right up against the front wall, with just a 10cm gap, where you will insert a panel of absorption. Your speakers need to be about 120 cm from the side walls, so they will be about 175cm apart. Your mix position (your head) should be 200 cm from the front wall, and the speakers should be aimed at a spot about 30cm behind your head (230 cm from the front wall). That's the theoretical best spot. from there, you can try moving things around in small increments to see if there is a a better spot, but it should be close to there.

- Where and how should I place my reflection panels for early reflections, what should the size of those be, and how should I treat the wall behind my monitors?

Use a mirrors to find the first reflection points on your side walls, and place 10cm thick absorption panels there. Put similar panels on the front wall, as I already mentioned above, and also on the front angled wall, above the speakers.

- Where else should I put reflection panels and diffusors? And which diffusors should I use?

Diffusers none at all (too small room), but you will need to cover the entire rear wall with thick absorption, at least 15cm, on both the vertical part and the angled part. You will also need a "cloud" over the area between the mix position and the speakers. That's a good start, but you will need more than that, probably.

- Are there any relativeley cheap ways to do additional bass trapping and would i need it at all?

It's a small room: You will need a LOT of bass trapping!

- Where should I mount my monitors? Should i build my own monitor stands or should I buy one of those?

I gave the locations above, and it is easier to build monitor stands. A very simple and cheap method is to stack up bricks or concrete blocks to the correct height, then wrap carpet or fabric around that, to hide it.

- Are there relatively cheap solutions to sound proof my room a bit more? Would decoupling my amp and monitors help it and how should I do that?

That won't help to soundproof the room, but it will help to keep the vibrations out of the floor, which is good. You can use Sorbothane pads for that.

- Is there a cheap way for air conditioning? it would need just a little cooling in the summer. I feared that leading the air outside with those systems would worsen the „soundproofing“?

For air conditioning, you can install a small "mini-split" system, probably around 9,000 btu/hr or 12,000 btu/hr for that room, but that does nothing for ventilation: it just cools/heats/dehumidifies the air. You will also need ventilation, which is a big issue....

- Should i use one of this power conditioners to hook up all my equipment? (Speakers, Interface, Computer, Monitor, Amp..etc..)

Not necessary. You only need that if you have power stability problems where you live, such as lights flickering and dimming, surges, frequency changes, etc.

I’m aiming for around 500€ as I want to build the panels and bass traps in the corners myself.

That's fine for your basic treatment, probably, but a mini-split air conditioner is going to cost a lot more than that.

- Stuart -

[musicman0318]

Thanks for replying!! I can't thank you enough. This forum is absolutely awesome and it's so nice of you pro guys to help us out!!

Hi again Chris! It looks like your thread "slipped through the cracks", and I had not seen it to reply to it. Sorry about that!

Never mind

OK, I noticed that all your questions so far are about treatment of the room (acoustics inside the room), not about isolation, so I'm assuming that: 1) you don't need much isolation, and/or 2) that you realize that isolating a room on an upper floor is very hard to do, and very expensive. Is that correct?

That's correct! As I said, if there are inexpensive options to get rid of 3 to 5 dB...great!! But if not at all, I can live with that!

Excellent! But if you build a panel with Rockooll, it won't be a "reflection" panel: it will be an "absorption" panel.

Thanks for correcting me. I have no idea why i wrote "reflection" hahaha

The room is likely too small to be able to use diffusers. Your only real option for treatment in such a room, is absorption.

Nobody told me that before! That's why I'm relying on you guys here

It's a small room: You will need a LOT of bass trapping!

About my DIY "Corner Bass Traps" - How exactly should I handle them regarding the sloped ceiling? I would assume it's better to go beyond the corner of the angled wall? So that the horizontal corner is covered as well?? (I hope this made any sense, my english is disgusting. sorry)

I gave the locations above, and it is easier to build monitor stands. A very simple and cheap method is to stack up bricks or concrete blocks to the correct height, then wrap carpet or fabric around that, to hide it.

When I bought my Neumann KH120A, wall mounts were included. I assume, mounting them to the wall would weaken isolation and won't be good at all?

That won't help to soundproof the room, but it will help to keep the vibrations out of the floor, which is good. You can use Sorbothane pads for that.

Great. Never heard of this products. And it's surprisingly cheap?! hahaha
But I guess it could also help reducing the sound going to the room below?

For air conditioning, you can install a small "mini-split" system, probably around 9,000 btu/hr or 12,000 btu/hr for that room, but that does nothing for ventilation: it just cools/heats/dehumidifies the air. You will also need ventilation, which is a big issue....

How is ventilation a big issue?

- I can get products from "Knauf" very cheap. I don't now if you are familiar with their products - if that's the case, which one would you suggest for absorbing frequencies?

Thanks again for your help!!

Chris

[Soundman2020]

Nobody told me that before! That's why I'm relying on you guys here

Don't feel alone! Even some studios that you'd think are "professionally designed" fail miserably on this one. The problem is that most types of diffuser, and especially numerically based ones (such as QRD, PRD, Schroeder, BAD, etc.) work by creating patterns of changes in the direction, frequency, phase, and timing of the sound wave. The wave-front arrives at the device as a coherent whole, at the same level across the entire front, all in phase with itself, but gets "broken up" by the diffuser. Different parts of the wave leave the device going in directions other than the one they would have taken from a simple bounce, which is good, but the device also delays some parts of the wave by different amounts (they have to take a longer or shorter path than their neighbors), thus changing the timing and phase of the wave. Some parts leave at a lower intensity than other parts. The net outcome is that if you measure all of those aspects close to the diffuser, you'll find "lobing", in the sense that the diffusion is not evenly spread out: in some directions, it is more intense, in other directions the phase changed more, and in yet other directions the timing changed to a greater or lessor degree. As the "broken up" wave moves further away from the diffuser, those artifacts tend to smooth out more and more, until eventually, when you get far enough away, the field is nicely diffuse, roughly the same in all directions.

So the problem is that if your head is too close to the diffuser, one ear can be in a different part of the uneven sound filed than the other ear, and each of those might be hearing a "lobe" that is not a true representation of a diffuse sound field.

The guys that figured out all the math that describes how diffusers work, two smart folks by the name of D'Antonio and Cox, also figured out that you need at least ten feet (3 m) between the face of the device and your head, in order to expect a reasonably diffuse field. Closer than that, and it is not diffuse, not even, not smooth, not nice. But the also said that it depends on frequency. Or more accurately, on wavelength. You need at least three full wavelengths between the device and your head, and preferably seven full wavelengths, in order to ensure that the field is well smoothed, with all the lobes evened out. So, depending on the frequency range that your diffuser is tuned to, you might need more than ten feet (3m). Work out the wavelength of the low cut-off frequency, multiply by three, and that's the closest that your head can be.

But even if you tune your device high, so the wavelengths are short, there's still that "minimum ten feet" rule.

Yes, you do see lots of studios that have Schroeder and Skyline and binary diffusers much closer than that, and you have to wonder why anyone would do that... until you realize that many musicians, producers, engineers and studio owners don't understand acoustics, and are therefore ignorant of the issues, while some places just want their studios to look cool, exotic, "acoustic", even though they know that the treatment is not appropriate. That's the same type of studio where you will see speakers sitting on the console meter bridge or dog-box, and the client couch at the back of the room just a foot or so (35cm) away from some really beautifully made Schroeder diffusers, tuned way down low...

If there are inexpensive options to get rid of 3 to 5 dB...great!!

You could probably get that much by just taking care to seal your room. In other words, examine all of the room carefully, bit by bit, looking for any gaps, cracks, or holes, and seal those with a good quality caulk. If air can get in or out, then so can sound. Go over ever part of the room, checking carefully, especially around windows and doors. The door will need rubber seals all around the edges (top, both sides, and especially the bottom) such that it is completely sealed when it is closed. Also take a close look at your electrical boxes: the switches, plugs, and light fittings. They are usually "leaky", and greatly reduce your isolation.

Just doing those few things can probably increase your isolation by 3 to 5 dB. Adding another layer of drywall (plasterboard) to all of the wall and ceiling surfaces, and putting a layer of tick plywood on the floor, could add another 3 or 4 dB.

About my DIY "Corner Bass Traps" - How exactly should I handle them regarding the sloped ceiling? I would assume it's better to go beyond the corner of the angled wall? So that the horizontal corner is covered as well??

Right! They need to go all the way from the floor surface to the ceiling surface.

When I bought my Neumann KH120A, wall mounts were included. I assume, mounting them to the wall would weaken isolation and won't be good at all?

Right! The KH120s are great speakers, but they have many possible uses. Those mounting brackets are for things like using them in a live room to play back mixes to the musicians, or as PA speakers in a hall. When you use those speakers in a studio, then forget about those brackets, and use proper stands that are very massive, or better still, flush-mount your speakers in "soffits" on the front wall.

Great. Never heard of this products. And it's surprisingly cheap

It's a well-kept secret! Sorbothane is a great product for acoustics. Most types of rubber "bounce". If you drop a piece on the floor, it bounces back up, because it converts the kinetic energy into deformation, then converts the deformation back into kinetic energy again. But if you drop a piece of sorbothane on the floor, it does not bounce. It just sort of "flops" onto the floor, and stays there. That's because it converts some of the kinetic energy into heat energy, which is then lost into the air. It deforms like other rubber, yes, and it regains it's shape again, but more slowly, and in a different way. In other words, it "damps" the vibrations applied to it, by converting the sound energy into heat energy, which then "disappears".

But I guess it could also help reducing the sound going to the room below?

It will reduce the amount of structure-borne sound going down through the speaker stand, into the floor, yes. But it won't affect the air-borne sound that gets into the floor.

How is ventilation a big issue?

Because you need to breathe! If your room is sealed air-tight to get good isolation, then you need a ventilation system with silencer boxes on it to provide fresh air and remove stale air (while still blocking sound), so that you can stay alive and comfortable....

- I can get products from "Knauf" very cheap. I don't now if you are familiar with their products - if that's the case, which one would you suggest for absorbing frequencies?

I know the brand, yes, and they do have insulation that is good for acoustics, but I'd need to know which of their products you can get where you live.


- Stuart -

[musicman0318]

Right! They need to go all the way from the floor surface to the ceiling surface.

Regarding covering the whole rear wall - would it even be better to leave a gap between the wall and the rockwool? and if so, can the gap be too big? should i leave a gap behind the "bass traps" as well?
I was thinking about leaving a gap as long as the bass traps length, so it would look like a new wall. dont know if you know what i mean by that? of course this would make the room length about 1 meter shorter and the room would nearly have the same length as width.

Right! The KH120s are great speakers, but they have many possible uses. Those mounting brackets are for things like using them in a live room to play back mixes to the musicians, or as PA speakers in a hall. When you use those speakers in a studio, then forget about those brackets, and use proper stands that are very massive, or better still, flush-mount your speakers in "soffits" on the front wall.

Do you have a link to a description how these soffits work? how to build them.

I know the brand, yes, and they do have insulation that is good for acoustics, but I'd need to know which of their products you can get where you live.

Actually I should get every product from Knauf as my father has connection to a bigger hardware store and they usually can order anything! So what products would you suggest?
Right now I have four of Knauf Heralan WP 50mm in the corners.

[Soundman2020]

Regarding covering the whole rear wall - would it even be better to leave a gap between the wall and the rockwool? and if so, can the gap be too big?

Yes, you can leave a gap if you want. It helps to extend the frequency range down a bit lower. Making the insulation thicker would do the same, and be a bit more effective, but of course it would also cost more.

should i leave a gap behind the "bass traps" as well? I was thinking about leaving a gap as long as the bass traps length, so it would look like a new wall. dont know if you know what i mean by that?

Not really! A diagram would help. But if you are doing superchunk style baas traps, it would be better to have insulation all the way to the wall.

Do you have a link to a description how these soffits work? how to build them.

The way soffits are made, and what they can accomplish, can be seen in this thread, http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471 Without soffits, it would have been nearly impossible to obtain such flat, smooth response. They work by removing the speaker from the room, and therefore eliminating all of the artifacts associated with the speaker and the front wall: No more SBIR, comb filtering, edge diffraction, power imbalance, front wall reflections, phasing issues, etc. The result is much cleaner, tighter, smoother, flat bass response, better imaging, etc.

Right now I have four of Knauf Heralan WP 50mm in the corners

I could not find any English language acoustic specs for that product. Please post a link to that, so I can see if it is suitable


- Stuart -