John Sayers' Recording Studio Design Forum Archive

Hello,
New member from sweden! Nice to meet you all!

I´ve got some serious dips and peaks below 300hz in my control room and it´s driving me completely crazy.
It´s just now that i realized that most of the corners (wall -wall, ceiling - wall, floor - wall) that i built reflects perfectly back to the mixing position, which i think might be the big problem here.

I´ve started trying to cure the problem, but i feel that i could use some help and that´s why i´m here.

Here´s some old pictures where you can see the room and how it looks like.




Tomorrow i´m going to take more pictures on the back wall and such.

Here´s the very professional super-edited photoshop 3d model of the CR that i made all by myself.



The red area is something that i just recently put up to try.
The whole area behind the speakers (excluding the window) is now covered with really high density rockwool
from floor to ceiling.
I´m talking about 140kg one´s, 7 cm thick, spaced about 7 cm´s out from the wall, and covered the corner.

I´m aware of that 140kg/m is very high, but i wanted to try it out. I can always change them for rockwool with less density without to much work.

I find it nice to be mixing now with these up. But the bass problems is still there. So the real question is,
what would be the first thing to do to help in this matter?

Since i have the doors in the corners in the back, its almost impossible to make efficient superchunks.

Im think that maybe i could cover the wall and the 90 degree corner (wall - ceiling) in the back wall behind me. Just cover the whole window as well while im on it.

Any idea´s out there?

Every input is greatly appreciated.

Hi Dimarino, and welcome!

I suspect that your basic problem is a general lack of bass trapping in your room. From your comment on superchunks, I guess you have also realized this. So, since those doors at the rear prevent you installing bass traps in the most obvious location, I reckon what I would try if that were my room, is to install large, deep bass traps in every other possible corner of the room. Wall-ceiling corners would be good, and you seem to have plenty of space up there for those. You can probably still get something up above those rear doors, too, and sine those are tri-corners (wall-wall-ceiling), you'll get an extra boost from whatever you do up there. Make those as big as you possibly can. You might be able to do some wall-floor corners too. Any chance you could move those doors a bit, to give you space for rear corner bass traps?

Also: The geometry on the photos and the "3D model ( )" don't seem to match very well, which makes it hard to figure out relative positions and angles, but it looks like your speakers are very close to the walls (less than 1m?), very far apart, and not angled so that the axes intersect at 60 degrees. Your speaker stands also don't seem to be very massive, and it looks like the speakers are directly coupled to the stands. You might want to try fixing all of those issues, too, since they might all be playing a role. What is your floor made of? Wood, obviously form the photos, but is it wood laid directly on concrete slab, or is it wood over a joist-and-subfloor construction? If so, you might find that your speakers, which seem to be coupled to the floor, are causing the floor to vibrate in the low bass range, which is adding to your problems. You can deal with that by replacing your stands with something really massive (concrete blocks, sand-filled metal, etc.) and/or decoupling the speakers from the stands. Moving the speakers further away from the walls would help, if you can do that without putting your mix position in a bad location acoustically (although it does seem that the one you have right now isn't very good!). Another option would be to flush-mount (soffit-mount) your speakers.

I think I'd start by playing around with the above options, and see how much of an effect they have.

- Stuart -

Here´s more recent pictures of the CR. Taken today.





As you can see i have put up rockwool all over the wall behind the montiors. I was thinking that since not too much high frequencies is projected to the back then it shouldn´t matter that i´m using that high density rockwool? It´s maybe even better for bass purpose since it has high density. Correct me if i´m wrong please.

Soundman2020 wrote:Hi Dimarino, and welcome!

I suspect that your basic problem is a general lack of bass trapping in your room. From your comment on superchunks, I guess you have also realized this. So, since those doors at the rear prevent you installing bass traps in the most obvious location, I reckon what I would try if that were my room, is to install large, deep bass traps in every other possible corner of the room. Wall-ceiling corners would be good, and you seem to have plenty of space up there for those. You can probably still get something up above those rear doors, too, and sine those are tri-corners (wall-wall-ceiling), you'll get an extra boost from whatever you do up there. Make those as big as you possibly can. You might be able to do some wall-floor corners too. Any chance you could move those doors a bit, to give you space for rear corner bass traps?

To move the doors is not possible without having to rebuild all 4 rooms, and its too much work. I was thinking about what you said, and its true. I could use all the space above the doors without too much effort.

I´ve got another idea though. I really love my windows. Its the perfect bass trap (exit). To let the bass outside. Unfortunately there´s a world outside.

So, how about this:


As you can see there´s a piece of rockwool in white cloth which is leaning out from the wall. My idea is to keep the angle like that one, all the way to the ceiling over the whole wall (6 m). That means that i would get up to 80 cm space behind the rockwool. That should trap some bass right?

Unfortunately i´ve got 3 big radiators on that wall (They´re sweet during the winter) so i can not build all the way down to the floor. But it should cover at least 3/4 of the whole wall.
Also it should cover the tri-corner you mentioned over the door.

In my mind this would definiely be the easiest way to do it, and not to expensive.
But do you think its enough for the room?

The geometry on the photos and the "3D model ( )" don't seem to match very well, which makes it hard to figure out relative positions and angles, but it looks like your speakers are very close to the walls (less than 1m?), very far apart, and not angled so that the axes intersect at 60 degrees. Your speaker stands also don't seem to be very massive, and it looks like the speakers are directly coupled to the stands.

Please excuse my poor graphics.
The real measurements for the room is.
6.70m backwall
1.30m sidewall (including doors)
2.20m frontwall
4,5m back to front wall.
angled side walls are relative to the sidewalls and the front wall.

I have tried many different positions with my speakers but the problems just move around.
I´ve got a pair of Adam p33a. (currently sent back to the factory for repair, thats what i get when im cheap and buy the P series instead of the S series.), and i was thinking about flush mounting them since they have the bass reflection in the front. I wanted to fix the acoustics in the room first though.

I put some special soft stuff made for furniture under the speakers today, and the vibrations from the speakers to the speaker stands almost dissappeared completely. I probably gained something there. Thanks for reminding me of those! It´s quik-lok stands, but not the massive ones.

Dimarino - check out the rear wall in Joes Castle

http://johnlsayers.com/Pages/Castle.htm

he has a forward leaning rear wall.

John Sayers wrote:Dimarino - check out the rear wall in Joes Castle

http://johnlsayers.com/Pages/Castle.htm

he has a forward leaning rear wall.

Thanks John,
Indeed that´s exactly what i was thinking with the rockwool.
Wonderful studio he has by the way, in the castle.

Another Idea that i have for the whole studio is to raise the ceiling.
It was stupid that i didn´t do it when i first built the studio.

At the rear wall its about an extra 80cm above the ceiling that is basically nothing up there except insulation and pipes for my ventilation.
And the height increases all the way to the front wall, where it is about 170 cm.

My idea would be to raise the ceiling all the way up and maybe cut the corner and use hangers up there like he has also done in the castle.
It would be perfect for the live room and the cr in my case, but it requires alot of work and i suppose it wont be cheap even though im doing all the work myself.

I plan this to be the next project with the studio in 1 - 2 years time. And for now im happy if i can get the time to install my rearwall bass trap.

Here is what i have done.

In this town it´s really hard to find good insulation. Its either really loose, or really dense. But I had some great luck two weeks ago. They had 24 m2 left overs of what they call "outerwall" insulation here in sweden which they sold cheaper to me.
The pieces are 80mm thick and 120 x 270 cm big. Wonderful stuff.
Its also fiberglass which mean its really hard to find any specification on the actual density.

After working with them i reckon they are about 90 - 100 kg/m3 which would be perfect from what i hear.

Here´s what i did.





Its almost like a regular wall, except that that it´s not all the way down to the floor because of the fat radiators and the doors on the sides.

The space from the wall is as much that i could build. which is 20 cm from the wall in the bottom, and 40 cm at the ceiling.



Here you can see, i filled the spaces with big pieces of the insulation. Then i put fibercloth (the white stuff on the pic) over, just so that I wont breathe to much of that fiberglass dust, and on top of that some nice fabric, which looks like coming from the porn industry.

On top of this now i´m gonna have some wooden panels with maybe 30 cm spacing. Just that it looks nice and because right now the room is pretty dead.


Is it functional?
Hell yeah. Its a big difference as many of you would imagine.
when I measure the frequencies in the room with a microphone (im sweeping a sine wave) the difference is not too big from before. But my ears tells me something completely different.

the stereo spacing is a big deal better now. The whole frequency spectra is more distinct and I can actually be mixing bass frequencies without headphones. the mix also sounds equal wherever you are in the room. Before i could get a completely different mix just by moving 1 meter to the side.
I decreased the RT60 a great deal. It´s almost weird just to be talking in the control room now.

Anyway, with some panels i get some natural sounding again.

Now another question.
The spacing behind the insulation is completely empty now. I reckon filling it up with insulation would have even more effect on bass frequencies.

What density should I use behind this insulation wall, looser or more dense?
Loose density tend to be alot cheaper. but i have also read somewhere that loose density has a great effect on the low end when used in basstraps and alike!

Please correct me on this.

Hi Dimarino. Glad to hear that the suggestions from folks here are working so well for you!

Congratulations! It's very heartening to get feedback from people who implement suggestions given here, and find that they really do work so well.

It's interesting that you say that a simple swept sine wave analysis doesn't show much difference in response, but your ears say otherwise: That suggests that your problem was simply long resonance, not frequency response. You mention that your RT60 is much tighter now, and that confirms the above, and that it has gone a long way to solving your problem completely. So your problem was basically just to much sound bouncing around the room, between the walls, floor and ceiling, and your bass trapping has controlled that well, without changing the actual response too much. I love it when theory works out so well in practice!

Regarding your comment about putting wood panels in front of your traps: I don't think that would be a good idea. It might just destroy your great new RT-60!!! What I would suggest is to put polyethylene or some other kind of plastic over the fibreglass, but underneath your "porn cloth" (!!) decoration. That will reflect back the highs that you are losing right now, but will not affect the lows. You will recover some of the "liveness" of your room like that, but without damaging the bass trapping that you did, and that is working so well. I suspect that if you did it with wood, you would get back the highs, but you would also get back some of the lows too. I think wood is too thick and dense to do the job that you need. something very thin, like plastic, will do it just fine.

You mentioned that you think the fiberglass is probably around 90 kg/m3 or so, and that's fine. It is about twice as dense as you need. The normal recommendation is for around 48 kg/m3. 90 kg/m3 will work too (as you already found out!), but it won't do much more for you than the lighter stuff. You probably would have gotten about the same effect from 48 kg/m3. It's a pity that you can't get the lighter stuff where you live, as it probably would have been cheaper, but the good news is that you managed to get stuff that works well!

The spacing behind the insulation is completely empty now. I reckon filling it up with insulation would have even more effect on bass frequencies.

Yep! Deeper trapping is better, so if you can get more insulation in that empty space, then sure, why not? You don't need to fill it all the way back to the windows / wall: you can leave a small air gap back there if you want, maybe an inch or two. This is because bass traps work on the velocity component of the sound wave, not the pressure component. Velocity diminishes as you get closer to a hard reflective surface, while pressure goes up. Right at the surface (wall/window/etc.) the velocity is zero (of course), and the pressure is at its maximum, so putting insulation in the last few inches near to the surface won't gain you anything at all in terms of trapping, since the velocity is low and the pressure is high. As you get further way from the surface, pressure goes down and velocity goes up, until at one quarter wavelength you have minimum pressure and maximum velocity. That is the point where trapping works best. So leave a small air gap next to the surface. It won't do any harm to put insulation in there, but it wont help acoustically: it will just waste money.

What density should I use behind this insulation wall, looser or more dense?

48kg/m3 is optimum, if you can get it. If you use stuff that is much lower density than that, then it won't be as effective. Higher density won't hurt, but it wont help much either. So if all you can get is that 90 kg/m3 stuff, then that should be fine.

Thanks for sharing your photos and results! Let us know how it goes when you complete the treatment.

- Stuart -

Thanks Stuart for taking your time,
It´s impossible to tell the value of having people like you in the world. Helping other people.

Regarding the insulation.
I can easily get insulation of around 40kg/m3, it´s just that the next step in density is 140kg/m3.
And that´s pretty dense and expensive.
What I thought was that around 90kg/m3 would be perfect in the sense that its enough loose to still
handle highs, and also more dense and effective in bass than 40kg/m3. I also read somewhere in this forum someone saying that 90 is optimum.

So you´re saying that high density insulation doesnt have more effect in bass?
It would be really nice to clear this out once and for all.

Anyway, i feel that i didnt waste any money even if i paid more than i would have done buying the lower density insulation.
These ones are big and really nice to be working with, and they don´t "dust" too much either.
And i like the new sound in my control room!

I think you´re right regarding that the resonance was the problem.
I also had alot of complete frequency cancelations at the mixing spot. Which i believe has to do with the resonance as well in this case.
The sinewave curve shows (and i can hear them frequencies!) that there is no more complete cancelations, and some areas are greatly improven, and some problems still persists.

Next thing to do is to improve the trapping behind the monitors and then do something about the ceiling or improve my cloud that i have.

I´m also gonna post pictures of my liveroom where im gonna try building a giant bass trap in the wall.

Thanks again

//Nicko

nicko, does your cloud have a back on it or is it open to the ceiling??

Here´s an update of how the CR looks like at the moment.

The problem was:
the whole frequency spectrum below 300 hz was more or less cancelled out.
Unlike most other controlrooms that has issues with peaks and standing waves, i had the opposite.
The standing waves seemed to take out themselves leaving nothing but guesswork for me in mixing.
Adding a sub didn´t do to much, neither did the eq settings on my speakers.

Have a look on the earlier pictures in this thread.

My idea was to damp the bass frequencies, and to prevent some of the standing waves to reach back and go suicidal in the mixing position, and to get a more even frequency response across the CR.


Today:
Due to poor economy i didnt have the money to pay a professional to come and make suggestions for my cr, so I basically have to build and try it all out for myself.
A tip for anyone who is doing, or planning to do the same: Before building, keep in mind that time is money. With that in mind, count in the costs of the material, and the fact that you might not be lucky and have to rebuild, and so on and so forth.
In the end, if you´re a fully booked studio, maybe it´s worth paying someone to have a look at the situation before doing any changes that might cost just time and money.
I have two passions, music and building (which is not so different after all) so I can count the building as my hobby time when my family asks me.

Thanks to some very helpful people here at the forum, I have pulled myself together and finally finished the CR with success.



As you can see on the left, I built a wall with 100 kg/m2 wool of the whole rear end of the CR, about 1 dm out from the wall in the down end, and about 30 cm in the upper end.
I filled the cavity in the corners and in the middle just behind the mixing position, with 30 kg/m2 glasswool.

This approvement made a better stability across the frequency spectrum. I have more control over mid´s and high´s, because they´re not boucing around in the back so much. I also a had a slightly better bass response.
After a couple of months I gave it a new try by trying to put one of my adam p33a speakers in the corner, almost flat against the wall, instead of having them
on those shitty stands that are about 50 cm out.
This gave me huge bass boost, and suddenly i started hearing things that I havent experienced from those speakers before.

So I gave flush mounting a try.



And while i was on it, i was changing the dense rockwool i had on the front wall, to the same 100 kg/m2 glasswool, and filled the sides behind the wood with loose wool.

Increadible.
I just finished my first mix in the new CR today, for a Tribute to Judas Priest album, and really important for the band and ofcourse for my studios reputation.
The first couple of hours I was still guessing, having the "old setup" in mind and ears. Then finally i just let it go, and trusted my setup and ears, and it turned out fantastic. It really translates in other systems, like it never has before.

At the moment im really high on the excitement of my new CR, that´s probably why I wanted to share this success with all of you in here, to help and to show appreciation.

To learn from this: Standing waves doesnt always make a peak in the frequency spectrum, the frequency can actually dissappear as well.

Also, i have tried moving my 3,200 dollar speakers around the area in front of the mixing position, but with the same result of lack in bass response.
I DIDN´T try the obvious "DONT" of placing them just as close to the wall (dont try this at home kidz) as I could. But when nothing else worked, I was more or less forced to do it in desperation, and it made the trick, together with the wool ofcourse.

I hope I have given some inspiration to the builders out there looking for new ways to approach the problem.
This fixed alot, not all, of my problems. It might not be the right for you, but it could be!
At least I hope you have enjoyed reading it!

If you have any questions, I would prefer if we keep the conversation in this thread for more people to read, it might help someone else too.

Hey Dimarino, congratulations! So glad that the suggestions worked out for you! Soffit mounting is a great solution.

And the room looks really good. What can I say?

You sound like you are really happy with the result!

- Stuart -

Congratulations!

Andre

Thanks alot soundman and Avare!

Especially you Soundman for coming up with ideas and possible solutions.
I´m still having a peak at around 120 hz that doesnt seem to go away. I always make a dip at around 120 hz when i find it disturbing, but just before mixdown
I deactivate the EQ. Its just for my own convenience, but still its annoying and leaving me again for some guesswork.
It would be really nice to have 100 % super control over the whole frequency spectrum sometime in my life. I dont mind headphones, and i have about 5 pairs of them ranging from 50 euros to 300 euros, but i still prefer having the speakers move the air around me.

Can anyone guess where the 120 hz peak comes from?
If i move up to the left or right upper wall-ceiling corner just next to the mixing position, the closer I get the more 120 hz.
Im thinking of implementing Soundmans idea of smaller superchunks in the uppercorners of the left and right angled walls.

Also I´m gonna try changing the clouds 3" wool for the same 7" wool as i have in the rest of the room.

Another unsolved problem is the phase problems as I sweep up above 500 to 4000 hz.
The signal is rarely completely dead, you can hear that it moves from speaker to speaker at some points.

Probably the side walls are not identically angled. Just a slight difference in angle would make this behaviour right?
If they would be identical i would have similiar peaks and dips, but here its more that when the left speaker has a dip the right is ok, and vice versa.
With that i mean, the perceived signal from the mixing position. when sweaping slowly you would perceive that the signal wanders from left to right and around
you like surround, obvious phase problems.

My idea for a solution in this case would be putting up mid/high absorbers or diffusors on the left and right walls.

Question: The windows are exactly the same height as the ears in the mixing pos. Is it enough to treat the rest of the wall, or would it make a huge difference if I would actually cover the windows with treatment, maybe as a portable solution?

Dimarino - two possibilities.

1 - does the cloud have a back on it as the floor to ceiling waves could be causing a problem albeit it looks like you ceiling height is around 8 feet (2.4m) which has a harmonic at 132hz.

2 - front to rear standing wave exaggerated by the windows. 17'8" (5.4m) has a harmonic at 122hz.