Building my home-studio

[nifaun]

Yes-ish.
It's better if the gap is filled (doesn't have to be with the same heavy duty RockWool as the front of the trap, but it will still work if you have, for example, a flat panel across a corner with a gap behind it.

I can't remember reading this explicitly in the text books I've read, but if you have a flat panel too far from a parallel wall then I expect it will act as a nodal point for any dominant room modes.
To take a theoretical example: say you have a flat panel 50cm from one wall, that will be at the nodal point for a wavelength of 1m (347Hz). So it's going to do next to nothing for that frequency. If your room was, say, 4m wide, it would also be a dominant room mode so could lead to problems.
This is why it's generally recommended to space your panels off the wall by a distance equal to their own thickness. In this case the thickness of the panel is large compared to the wavelength of the space behind it, so it will still have a significant effect. In the example above we can see that a 5cm deep panel, 50cm from the wall is really pretty small compared to the wavelength of the standing wave that can arise either side of it, so therefore won't have much affect.

Putting a flat panel across a corner obviously gives you a variable distance between the wall and the panel so mitigates this effect.

Thanks Blinddrew,

I asked several isolationshops about the right rockwool plates for my studio. Most of them said they had only rockwool plates to a density of 55. When I searched online I found Rockfound Duo what has a density of 60 on the front and a density of 35 in the rear... Im kinda doubt wheter this is the panel I need, can you provide me more clarity about this? If not, can you tell me which panel is best for my studio?

[Sam Spoons]

Another advantage of a corner placement is that the reflected wave travels around the corner, reflected twice before emerging so the effective depth of the trap is greater than the actual physical depth.

[Drew Stephenson]

I asked several isolationshops about the right rockwool plates for my studio. Most of them said they had only rockwool plates to a density of 55. When I searched online I found Rockfound Duo what has a density of 60 on the front and a density of 35 in the rear... Im kinda doubt wheter this is the panel I need, can you provide me more clarity about this? If not, can you tell me which panel is best for my studio?

I suspect the difference between 60 and 55 density is negligible from both a audio and workability perspective, but if you let us know whereabouts in the world you are we can probably make some sensible recommendations.

[nifaun]

Yes-ish.
It's better if the gap is filled (doesn't have to be with the same heavy duty RockWool as the front of the trap, but it will still work if you have, for example, a flat panel across a corner with a gap behind it.

I can't remember reading this explicitly in the text books I've read, but if you have a flat panel too far from a parallel wall then I expect it will act as a nodal point for any dominant room modes.
To take a theoretical example: say you have a flat panel 50cm from one wall, that will be at the nodal point for a wavelength of 1m (347Hz). So it's going to do next to nothing for that frequency. If your room was, say, 4m wide, it would also be a dominant room mode so could lead to problems.
This is why it's generally recommended to space your panels off the wall by a distance equal to their own thickness. In this case the thickness of the panel is large compared to the wavelength of the space behind it, so it will still have a significant effect. In the example above we can see that a 5cm deep panel, 50cm from the wall is really pretty small compared to the wavelength of the standing wave that can arise either side of it, so therefore won't have much affect.

Putting a flat panel across a corner obviously gives you a variable distance between the wall and the panel so mitigates this effect.

Thanks Blinddrew,

I asked several isolationshops about the right rockwool plates for my studio. Most of them said they had only rockwool plates to a density of 55. When I searched online I found Rockfound Duo what has a density of 60 on the front and a density of 35 in the rear... Im kinda doubt wheter this is the panel I need, can you provide me more clarity about this? If not, can you tell me which panel is best for my studio?

1. I havent understood it yet... Does the distance between the panel have to be equal to the thickness of the panel?

I asked several isolationshops about the right rockwool plates for my studio. Most of them said they had only rockwool plates to a density of 55. When I searched online I found Rockfound Duo what has a density of 60 on the front and a density of 35 in the rear... Im kinda doubt wheter this is the panel I need, can you provide me more clarity about this? If not, can you tell me which panel is best for my studio?

I suspect the difference between 60 and 55 density is negligible from both a audio and workability perspective, but if you let us know whereabouts in the world you are we can probably make some sensible recommendations.

2. Okay so what about the tho measurements. Should I focus on the front one... Or does the back one matters as well.

Im based in the Netherlands, ordering from German stores is possible as well.

[Drew Stephenson]

Sorry, meant to reply earlier but forgot.

I'll see if I can draw a diagram for 1) - leave that with me. But in short, yes, the distance from the wall should be roughly the same as the thickness.

A rockwool plate of density 55 will be fine. If you went with a dual density I would guess, and it would be a guess, that you'd be better with the low density side facing the room. This would make it easier for the sound to penetrate the slab and therefore be absorbed.
If you use too high a density (100kg/m3 for example) it will still function to an extent but will actually reflect higher frequencies rather than absorb them.
Knauf Earthwool is a comparable product to Rockwool.
I have no idea if this is a good supplier, but they have 60kg/m3 rockwool and earthwool: https://www.ikoustic.co.uk/products/aco ... g8QAvD_BwE

[Drew Stephenson]

Ok, here's an attempt to answer your question 1) with some badly drawn diagrams (I couldn't easily find a sinewave so you've got ovals instead)...

Let's look at sound interacting with a wall:

The highest sound pressure is right up against the wall (because the air can't go anywhere) but the most air movement is 1/4 wavelength away from the wall.

This can be easier to visualise if you think of it like a guitar string:

N.B. we're obviously only looking at half a wavelength at this point, the rest of the wavelength continues off the screen to the right.

Right, now let's add an absorber against the wall and bring the wavelength down a bit for illustration:

As we can see, with the absorber right against the wall, it's most effective on its outside edge, where the air movement is greatest, but against the wall, where there's no air movement, it's doing almost nothing.

Let's move the absorber away from the wall a distance of its own thickness:

Now we can see that all the absorber material is in an effective zone for this wavelength.

Now, to get to your question of distance from the wall vs thickness of absorber.
Let's take the same situation and look at a higher frequency:

Even where half a wavelength matches the distance behind the absorber, we can see that it's still going to be effective because the peak air movement is still easily covered by the absorber at the next anti-node.

Ok, now take the same absorber but bring it further away from the wall:

You can see now that at longer wavelengths, where the node coincides with the position of the absorber, it will be doing very little at all.

And if we go back to the shorter wavelength:

You can see that the absorber here will be less effective because it again sits at a node.

I'm sure Hugh or Max could have explained that better (and they may still be along to correct me!) but hopefully that makes sense?

[Wonks]

Looks OK to me.

It should be noted that this really applies to standing waves/resonant wavelengths which are fractions of the rooms dimensions. Other soundwaves will hit the absorbers at all different amplitude along their wavelengths and will be attenuated to greater or lesser extents. They certainly won't all hit the wall at node points.

But it is the standing waves that cause the most problems, which is what we (hopefully) design and position the traps to reduce.

[Hugh Robjohns]

All well explained Drew, although in respect of the last two diagrams:

Ok, now take the same absorber but bring it further away from the wall:

You can see now that at longer wavelengths, where the node coincides with the position of the absorber, it will be doing very little at all.

At very low frequencies the wavelength is so long that to emulate your diagram the absorber would have to be placed several feet from the wall, which is obviously impractical, so it's never going to find itself sat in a node half a wavelength out in reality. Instead, at very low frequencies the absorber will tend towards being in the node pressure zone against the wall. Either way it loses efficiency, of course.

And if we go back to the shorter wavelength:

You can see that the absorber here will be less effective because it again sits at a node.

Except that in this situation a practical absorber will be thick enough probably to span several full (short) wavelengths, so it will actually be very efficient.

[Drew Stephenson]

Sorry Hugh, the point I was trying to make was that a 'normal' depth absorber wouldn't necessarily benefit from being further and further from the wall.
The question a few posts back was about a 5cm panel 50cm from the wall.

[nifaun]

Sorry Hugh, the point I was trying to make was that a 'normal' depth absorber wouldn't necessarily benefit from being further and further from the wall.
The question a few posts back was about a 5cm panel 50cm from the wall.

Thanks blinddrew. But I don't know if it is because I'm a non native speaker or rather that I'm a beginning record producer, but how do I know how much is 1/4 wavelength?

Ooh and they always say that you have to put 4 bass traps, one for each corner, but in one of the corners is a door? Would that give any problems?

Thanks for your help and your patience, I'm close to recording in my new studio

[Drew Stephenson]

The wavelength of a sound is inversely proportional to the frequency.
At 20kHz the wavelength is 1.7cm. So clearly even a thin absorber will be effective here as the point(s) of the greatest air movement will always be included in the depth of the absorber.

At 20Hz though, the wavelength is 17m. So in order to have an absorber that was fully effective here it would need to be 4.25m deep. That's not practical for most of us! (My room is only 4m long).
So you can quickly see that bass performance in small rooms is always a compromise.

Say you have a panel 10cm deep, and it's spaced 10cm from the wall. That will be very effective down to about 400Hz (wavelength about 86cm) because the front of the absorber is 20cm from the wall; nearly 1/4 wavelength at 400Hz.
It will still be fairly effective below this as well.

But to control your low end you need to go deeper, which is why if you can use the corners you get the benefit of a deeper trap without losing too much room space, as well as putting your bass traps in the most efficient place for them (sound pressure is at its highest in the corners).

So definitely target the corners, and if you can only do three of them then that'll have to do but you might get a bit of stereo instability - consider hanging a thick broadband absorber off the back of the door to compensate.
Don't forget that it's not just the vertical corners you can tackle, remember your wall/ceiling corners as well.

[Hugh Robjohns]

Sorry Hugh, the point I was trying to make was that a 'normal' depth absorber wouldn't necessarily benefit from being further and further from the wall.

Ah.. yes. True enough.

The question a few posts back was about a 5cm panel 50cm from the wall.

Hmmm... not particularly effective or particularly practical !

[Hugh Robjohns]

Ooh and they always say that you have to put 4 bass traps, one for each corner, but in one of the corners is a door? Would that give any problems?

I don't know who always says that, but it's not strictly really true.

In general, the more bass traps the better, and the more symmetrical the treatment in the room the better... but I ended up with three bass traps because of a door in the corner too!

The two front traps are bigger and identical (which was important for stereo imaging stability). The third trap in the rear right corner was smaller, and I've made do with panels hung on the door itself for the other corner. These differences at the back of the room haven't affected the Stereo imaging at all, but still help usefully with the bass control.

https://www.soundonsound.com/techniques ... ound-good

[nifaun]

Ok got it...
Is it also possible to cut the rockwool in to the half to a width of 30 cm? It woudnt only be cheaper but also the distance to the wall will be equal with the thickness of the panel?

And when I attach them to a trellis, how do I attach the complete panel to the wall?

[Drew Stephenson]

If you're proposing a panel 30cm deep, 30cm from the wall, then yes, that should be effective down to a fairly low frequency.
As to attaching it to the wall, that's going to depend on what your wall is made of, but basically let the bulk of the weight be taken by the floor and secure the corners to stop it moving.

[nifaun]

I actually meant a bass-trap which is 30 cm wide instead of 60 cm. It would be more convenient regarding the heater and windowsill. I'm using four panels so that the thickness would be 20 cm, and the gap to the wall would also be approx. 20 cm..

I heard people saying that for singing it isn't necessary to cover from floor to ceiling. It would also be quite expensive and not practical because this isn't possible in every corner of my room because of tubes who are leading to the heater. Therefore I would like to attach those panels and center them to the point of impact... Since I can not let the bass trap rest on the floor I need to attach them. The same as the panels also need to be attached to the wall. I don't know how heavy those bass traps will be as I have not worked with them yet. And I understand not every wall will held the panels and traps. In that case let this lean on the floor would be the only solution. Though I would have another problem by then. The average person is approx. 180 cm long, and the trellis I'm working with is also 180 cm long, When I want to add another one up I don't have a floor where I can let it rest on.

I was wondering If you would have a solution to solve this.

[Drew Stephenson]

I think it would really help if you could share a diagram or two showing what your plan for the room is please.
This forum doesn't host images but you can load them onto a platform like Imgur, set them to hidden if you want to, and link to them here.

[nifaun]

I think it would really help if you could share a diagram or two showing what your plan for the room is please.
This forum doesn't host images but you can load them onto a platform like Imgur, set them to hidden if you want to, and link to them here.

I hope the positioning of the panels are fine. Could you check please?
https://imgur.com/iZ1RS0m

Since I can't rest them on the floor, bass traps should be at hight of the singers mouth??? And I have tubes in one corner, I'd like to attach them to the wall.. But I dont know to be honoust.

[Drew Stephenson]

I hope the positioning of the panels are fine. Could you check please?
https://imgur.com/iZ1RS0m

You might want to think about some panels on the wall opposite the speakers - that's another 'mirror point'.

Since I can't rest them on the floor, bass traps should be at hight of the singers mouth??? And I have tubes in one corner, I'd like to attach them to the wall.. But I dont know to be honoust.

Bass traps work best in corners, triple-corner are the best, but you'll have to find the compromise that works for you and the room.
The height of the singers mouth won't make much difference a low frequencies.
What you've drawn up should make a significant difference to the room and give you much more accurate monitoring.

[nifaun]

I hope the positioning of the panels are fine. Could you check please?
https://imgur.com/iZ1RS0m

You might want to think about some panels on the wall opposite the speakers - that's another 'mirror point'.

Since I can't rest them on the floor, bass traps should be at hight of the singers mouth??? And I have tubes in one corner, I'd like to attach them to the wall.. But I dont know to be honoust.

Bass traps work best in corners, triple-corner are the best, but you'll have to find the compromise that works for you and the room.
The height of the singers mouth won't make much difference a low frequencies.
What you've drawn up should make a significant difference to the room and give you much more accurate monitoring.

Okay, so you suggest me to set them on the floor? It is difficult to cover the bottom and top triple corner, I actually dont know how to do this in a practical way, Would you have suggestions?

I have located the monitors with the mirror trick, and pointed the location at the side wall. Would you suggest to attach those panels(1,80) to the wall or is setting them on the floor sufficient?