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PostPosted: Thu Jul 12, 2018 7:43 am 
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Joined: Thu Nov 06, 2014 9:06 pm
Posts: 17
Location: Athens, Greece
Hi everyone, I am George.
Thank you for the time and the effort you all put into this forum!

I am reading the forum for some time now, also reading Rod Gervais book and I am in research of how to correct the acoustics of my room.

The room is 41m2 on a groundfloor in Athens - Greece and I am planning to use it mostly as a control room for mixing.
I am not soundproofing the room, just treating the inside for good acoustics.
I usually mix around 80-85dB loud with higher and softer volumes for short periods of time.
My monitoring system is a 2.1 ATC, with SCM20-2A monitors and SCM0.1/12 sub.
The budget has to be the lowest possible so I am using insulation, wood and other stuff I already have and I am building everything on my own.

Room's volume is 163m3.
Dimensions are 8.7m long, 4.4m wide, 3.95m high.
On north side around the 6th meter of the total length the room gets wider on the right side by 1.5m but that is now drywalled to create a storage room and leave the room with the dimensions mentioned above.

Ceiling's concrete joists are coming down off the ceiling 37cm.
Side walls' concrete studs (four of them) are coming out of the walls about 7-11cm, and front wall's stud is coming out 13cm.
The floor is concrete covered on tiles.


Things I have done so far:

-Installed the electrical stuff, outlets, lights, etc.
-Seperated (drywall) the small corner making it a storage room.
-Covered all the vertical and horizontal corners (front, back, sides), including the ones on the ceiling where the two joists are, with mineral wool rolls (air resistance of 5KPas/m2) of an approximate diameter of 45cm. I placed the rolls inside LDPE bags which for their density and thickness will provide 6dB reflection at the cuttoff frequency of 425Hz and +6dB/octave above it.
-I am now at the point of building the frame for covering the corner traps on fabric.


My next moves are (and this is the point where I seek some advice):

1-building the ceiling clouds. Three of them, placing them on the three blocks of the ceiling-inbetween the joists (that will leave a small gap between the corner traps and the cloud of about 7-10cm), all angled the same way-that would be all looking on the back wall where the door is, starting around 10cm off the ceiling and adjusting the other side accordingly. Making them hard-back, 3x1.5m big, 15cm deep or more if needed, filled with 30 or 40Kg/m3 stonewool.

2-Treating the first reflection points and adding broadband panels all over the room,many of them, making them 0.6m wide by 2.4m high, 15cm deep, leaving 5-10cm air gap behind them, 30 or 40Kg/m3 stonewool. Many of them, placed in sequence, leaving the wall treated with 50% uncovered area, i.e starting with a 60cm wide trap, then leaving 60cm untreated, then one more trap, and so on..

3-placing a big trap I already have on the back wall, it's size is 2x1.5m, 35cm deep, filled with mineral wool (air resistance of 5KPas/m2), placing it's center on back wall's mid-height/mid-width, and considering building in front of it an air transparent diffuser using wooden slats.


So regarding 1. What should I consider in order to know the angle, the depth and the starting distance off the ceiling for the cloud?
I understand that will be used for breaking room modes but whats the math behind it? maybe someone can point me in the right direction..
Would it be better to be opened back? i.e. no need to brake modes, etc, so i can just make big bass traps on ceiling (30cm deep+air gap) just to add to overall bass absorption.

2. Am I in the right track for the coverage, depths, gaps, dencity of wool?

3. Is that ok placing it there or is a better usage for it?

More, what do you think about the corner traps I placed so far, did I missed something or did something wrong?

I am attaching a floorplan, calculation of room modes, links for measurement of the empty room and full room, pictures and link for video of the progress, etc.

The measurement called "full room" was made with all my equipment,instruments,stuff and approx 15m3 of insullation being inside the room and covered on plastic membrane, as close to the back of the room (where the door is), leaving the front side 4.36x3m available for making the test with the speaker, mic, etc. It may not be usefull, I just thought at that time to take a measure of the full room so to see the difference between empty and full.

Also the "empty room" measurement is before the drywall of the storage. One big unseperated space with nothing inside.

Thank you in advance for your time.


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PostPosted: Thu Jul 12, 2018 11:21 am 
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Location: St. Albert, Alberta, Canada
What style of control room are you going for? Ex: RFZ

Are you going to soffit mount your speakers?

I'm not convinced your tube style bass traps are appropriate.

Why have you not drawn your space up in SketchUp? Drawing up your plan will help you so much.

What's your HVAC situation like?

Greg

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PostPosted: Thu Jul 12, 2018 3:04 pm 
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Hi George, and Welcome! :)

Quote:
The room is 41m2 on a groundfloor in Athens - Greece and I am planning to use it mostly as a control room for mixing
41 m2 is certainly a nice size for a control room.

Quote:
SCM20-2A
I'm not familiar with those, personally, but I've read good things about them. They don't go down very low, though, so the sub is very necessary, and will need careful placement.

Quote:
Dimensions are 8.7m long, 4.4m wide, 3.95m high.
That's a good overall size, but the ratio is not that good. It fails two of the three "critical tests" for a control room. You might want to consider building a wall to re-size that, and get a better ratio. You have enough room to do that, and still have a good sized room. You can clearly see the problem on the prediction you did using Andy's calculator (amroc). You are going to have serious modal issues around 39 Hz, 44 Hz, 58 Hz, 78 Hz, etc., and your room ratio is way outside of the Bolt area. You really should try to fix this. The signature caused by that modal pattern is clearly visible in your MDAT files, as comb filtering across the entire spectrum.

Quote:
Ceiling's concrete joists are coming down off the ceiling 37cm.
Side walls' concrete studs (four of them) are coming out of the walls about 7-11cm, and front wall's stud is coming out 13cm.
That can be very useful.

Quote:
(air resistance of 5KPas/m2)
That's about right for mineral wool, for low frequencies, but it's not enough.

Quote:
inside LDPE bags which for their density and thickness will provide 6dB reflection at the cuttoff frequency of 425Hz and +6dB/octave above it.
Not necessarily, because it looks like the plastic is stretched tight, so it will act more like a membrane than a foil. I suspect that those will also act somewhat like poly-cylindrical reflectors to a certain extent, especially for higher frequencies. That's good, not bad!
Quote:
My next moves are (and this is the point where I seek some advice):
1-building the ceiling clouds.
I would not start with clouds. I would start with teh rear wall first. It's always the most prominent acoustic surface, and always needs the most treatment. Your room is plenty large enough that you can get in some seriously deep bass trapping back there, and also use diffusion, to properly produce a good ITDG and diffuse reverberant field. This room can be very, very good, if you take the time to treat it correctly!

Here's a thread that shows how to treat a control room for excellent acoustics: viewtopic.php?f=2&t=21368 That one is currently in progress, and we are tuning the room to be as good as possible. You can see how I went about that process, and what happens at each stage.

As you can see from that thread, the cloud has NOT yet been built, and will only be done as one of the final steps, in this case. Here's another room (already finished) where you can see the cloud in place: www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=20471 That room is close to the same size as yours, and you can see the results we got. Yours could be similar. In that case I put the cloud in sooner, but it still was not the first thing I did. Bass trapping comes first, always.

Quote:
2-Treating the first reflection points and adding broadband panels all over the room,many of them, making them 0.6m wide by 2.4m high, 15cm deep, leaving 5-10cm air gap behind them,
Instead of deciding on that now, I would wait until the rear and front of the rooms are done, then measure the acoustic response of the room to see how it is doing, and based on that decide what side wall treatment will be needed.

Quote:
leaving the wall treated with 50% uncovered area, i.e starting with a 60cm wide trap, then leaving 60cm untreated, then one more trap, and so on..
That would tune the treatment to a couple of specific frequency ranges, and would not deal with the acoustic issues in the room.

Quote:
3-placing a big trap I already have on the back wall, it's size is 2x1.5m, 35cm deep, filled with mineral wool (air resistance of 5KPas/m2), placing it's center on back wall's mid-height/mid-width, and considering building in front of it an air transparent diffuser using wooden slats.
As I mentioned above, the rear-wall bass trapping should be the FIRST thing you do. 35cm is not very much for a room that size, and I would not make it a single mass of insulation. Rather, I would do classic acoustic hangers of varying sizes, deeper in the corners, less deep in the middle of the room, something like this:

Attachment:
STVNO-USA-REAR-WALL-DSC00299.JPG


That's from another room that I'm working on right now, and you an see the hangers in the frames across the entire rear wall. The hangers in the corners have already been covered with their insulation, but the ones in the middle have not yet been covered in that photo. They have been now, but I don't have an updated photo yet. The rectangular frame in the middle, above the sofa, is where the diffuser will go, once it is completed. You should do something like that. It is working very well in this room.

Quote:
So regarding 1. What should I consider in order to know the angle, the depth and the starting distance off the ceiling for the cloud?
It's too soon to know that, and it would require that you model the room and the cloud in something like SketchUp, then slowly adjust the angle and height of the cloud until you get the optimum RFZ conditions.

Quote:
I understand that will be used for breaking room modes but whats the math behind it? maybe someone can point me in the right direction..
The primary purpose of a cloud is NOT to break up modes! The number one most important reason why you need a cloud, is to control reflections from the ceiling, and to add absorption above the mix position for mids, as well as deep damping for lows. Slightly smearing the vertical modal issues is a distant side effect that is useful, but that isn't the reason why clouds are there,

Quote:
More, what do you think about the corner traps I placed so far, did I missed something or did something wrong?
Corner traps need to be large. The best option is either properly designed hangers, or superchunks.

Quote:
links for measurement of the empty room and full room,
Are you sure you followed the instructions for doing that? Here: viewtopic.php?f=3&t=21122 I only see data for one single speaker in each case.

Yes, you are getting some effect from the treatment you have put in there, but nowhere near enough.

Here is the waterfall plot for your room as it is right now, for the low end (below 300 Hz)
Attachment:
ALMAELECTRONIX--REW-WF--20-300--RT-first.png


Compare that with the exact same graph for the room in the picture above:
Attachment:
STVNO-USA--REW-WF--20-300--RT-first.png


Your room is similar in size to this one, but you can see that you are a very long way from getting the low end under control.

Here's the low-end frequency response graph from your room right now:
Attachment:
ALMAELECTRONIX--REW-FR--20-300--RT-first.png


And the exact same graph from the room in the picture above:
Attachment:
STVNO-USA--REW-FR--20-300--RT-first.png


Once again, you can see that your response is far from flat.

Here's the spectrogram for your room:
Attachment:
ALMAELECTRONIX--REW-SP--20-300--RT-first.png


And the same spectrogram for the room above:
Attachment:
STVNO-USA--REW-SP--20-300--RT-first.png


Finally, the RT-60 plots for both rooms. These are different form the others, because the ones above are only for the low end (below 300 Hz), but these two here are for the entire spectrum. Your room:
Attachment:
ALMAELECTRONIX--REW-RT--40-11k--RT-first.png


And for the room in the photo:
Attachment:
STVNO-USA--REW-RT--40-11k--RT-first.png


As you can see, you have a long way to go. Your room is similar in size to this one in the photo, so you should be able to get similar results. I have not yet finished the treatment of this room: there's still a lot more to go, but you can see that it is possible to get really nice results, even in an unfinished room.


Quote:
It may not be usefull, I just thought at that time to take a measure of the full room so to see the difference between empty and full.
It is VERY useful! All REW tests are useful. I usually taken dozens of REW tests throughout the tuning process for a control room, and sometimes hundreds. For the Studio Three room I mentioned above, the owner wanted to go to extremes, and tune it to the physical limits of what could be achieved, so we ended up taking nearly four hundred REW measurements in there, over several months. All of them were useful. In Frank's room (the one that is in progress at present) so far we have taken 51 measurements. So take as many tests as you can! Each time you do something to the room, also do another REW test, so you can see what is working, and what still needs to be done. However, do make sure that you get the measurement mic in the exact same position in the room, every time: the tip of the mic mist be in the precise same spot, accurate to within a few mm.

So, I would suggest that you should stop here for a bit, and first define what basic concept you want for your room, then do the initial layout for that, building whatever is needed to start down that path, then treat the rear wall and front wall, then the ceiling and first reflection points, then the side walls, and last of all the cloud. The tweak all of that as needed to get is as good as possible.

A room that size has excellent possibilities, if you design it right and treat it right.


- Stuart -


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PostPosted: Thu Jul 12, 2018 6:23 pm 
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Joined: Thu Nov 06, 2014 9:06 pm
Posts: 17
Location: Athens, Greece
Soundman2020 wrote:
Hi George, and Welcome! :)

Thank you Stuart,
thanks for taking the time to reply and really quick!

Quote:
I'm not familiar with those, personally, but I've read good things about them.

These 2-way monitors with SL bass/mid drivers are nicer looking :D , slightly larger and more expensive "audiophile" version of ATC SCM20 pro.

Quote:
They don't go down very low, though

Yes, here are the specs:
Attachment:
20s specs.jpg


Quote:
sub is very necessary, and will need careful placement

I am planning to place it 37.5cm off mains' centerline and 12.5cm closer to front wall, starting from same ac.axes plane.
This stereo sub is cube sized and really big so may not be possible to move it closer to front wall as I am planning to have my mains as close as possible due to sbir. But we will see.
Its specs:
Attachment:
sub specs.jpg


Quote:
You might want to consider building a wall to re-size that, and get a better ratio

I suppose building a wall at the front is more suitable for this as there is the door on the back wall right?
The thing is that using amroc and changing room's length I went down to 6 meters and I am still not getting inside bolt area.
Changing length and height takes me inside, if I go 5.5m for the length and 3.58m for the height. (I cannot get wider unfortunately)
But that is also moving the schroeder frequency up and leaving the room with a total size of 24m2..close to half of the starting..
Attachment:
amroc size 2.jpg


Quote:
That can be very useful

I can see the use as of breaking the modes. Are you referring to that or there is more?


Quote:
will also act somewhat like poly-cylindrical reflectors to a certain extent

I am not familiar with poly-cylindrical reflectors and their behaviour, any technical documents /articles to point me at so I can read?


Quote:
I would start with teh rear wall first

I can do that, thank you!

Quote:
to properly produce a good ITDG

Yes I can even now see that without treatments on first reflection points etc that my ETC looks promising.

Quote:
Here's a thread that shows how to treat a control room for excellent acoustics

Quote:
Here's another room

I will definitely study both over and over again! :lol:
Thank you!

Quote:
Instead of deciding on that now, I would wait until the rear and front of the rooms are done

I will do that! About the front wall, I was only thinking of adding some broadband panels, apart from the corner traps.
Do you think I need more than that?

Quote:
then measure the acoustic response of the room to see how it is doing, and based on that decide what side wall treatment will be needed

Do you mean decide if the side wall treatment needs to be thick or not in order to absorb lower, etc?

Quote:
That would tune the treatment to a couple of specific frequency ranges, and would not deal with the acoustic issues in the room

So apart from the first reflection points, it would be better to target the modes I am treating the room for and place the panels accordingly, right?

Quote:
rear-wall bass trapping should be the FIRST thing you do

I will do that!

Quote:
I would not make it a single mass of insulation

I already got this one, from my previous control room. Got to do something with it, don't you see any usage? :roll:


Quote:
I would do classic acoustic hangers of varying sizes, deeper in the corners, less deep in the middle of the room

I think I can do this.
Is it a problem if I leave the rolls inside bags as they are and add the hangers in front of them (I can make holes on bags also)
I ll probably go to 50-60cm on center and 1m on corners (60+40 the existing ones)

Quote:
is where the diffuser will go

A deep diffuser of any design (qrd, skyline, etc) covering 1.2x1.8m (HxW) will do the job right? I got leave that part untreated and make a frame around it



Quote:
then slowly adjust the angle and height of the cloud until you get the optimum RFZ conditions

Ok, I can do they ray tracing to create that, I ve bookmarked a post somewhere :roll: how to do that.

Quote:
The number one most important reason why you need a cloud, is to control reflections from the ceiling, and to add absorption above the mix position for mids, as well as deep damping for lows. Slightly smearing the vertical modal issues is a distant side effect that is useful, but that isn't the reason why clouds are there

So I can as well make it thick and open back, without getting the distant effect of the close back, but still open back is easier and lighter to support.


Quote:
Corner traps need to be large

So 42cm corner to front of the rolls is not so big right? So I need to add hangers on front corners too I suppose..


Quote:
Are you sure you followed the instructions for doing that? I only see data for one single speaker in each case.

Yes sorry I thought file was too large so I just left the "right" measurement to reduce size.
Here is all of them.

Quote:
Yes, you are getting some effect from the treatment you have put in there, but nowhere near enough.
[/quote][/quote]
Sorry I was not clear about that. The full room measurement is not with the insulation rolls placed in corners. It was taken just before starting, when i just got all my stuff inside the room. Just to see the changes..
I have no measurement for the corner traps yet.


Stuart , you are doing and excellent job on these rooms, I wish I could afford to hire you.
You see I am trying to use all the insulation and stuff I had from a previous control room I had so I am cutting corners but I can understand now that will not work.
But being a father of two boys and my wife not working that makes it really hard for me to fund it.
I am sure you heard about the crisis here in Greece making things even more difficult for families.
Anyway I will read and go over everything you pointed me at and slowly try to find some cash to buy more insulation for the hangers and we will see..
Thank you so much for all your time and your suggestions , I really appreciate! :)


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Last edited by almaelectronix on Fri Jul 13, 2018 5:01 am, edited 2 times in total.

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PostPosted: Thu Jul 12, 2018 6:38 pm 
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Location: Athens, Greece
Hi Gregwor, thank you for your post!

Quote:
What style of control room are you going for? Ex: RFZ

I don't really know how to design any of these, I guess I will try to create a reflection free zone at the listening position but I don't really know if there would be a benefit if I choose some other style..

Quote:
Are you going to soffit mount your speakers?

No I am going free standing. I am on really low budget and I need a place to start making some music cause as I have some projects I was proposed to take over.

Quote:
I'm not convinced your tube style bass traps are appropriate.

Do you think will not work at all or?


Quote:
Why have you not drawn your space up in SketchUp? Drawing up your plan will help you so much.

I don't really have a plan yet to be honest, just researching and gothering info as I slowly make some progress on the room (approx. 5hours a week) and see where it takes me

Quote:
What's your HVAC situation like?

I already got but not installed yet a split a/c for cool/heat and a single motor for taking the air out.
I will need the pipes, probably one more motor for bringing the air inside, and the soundproofing boxes for that.


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PostPosted: Fri Jul 13, 2018 7:22 am 
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Quote:
Yes sorry I thought file was too large so I just left the "right" measurement to reduce size.
Here is all of them.
Great! But there's a problem with the way you are doing your tests. Take a look at this:

Attachment:
ALMAELECTRONIX-all-levels-the-same.png


Notice something strange there? That's the frequency response graphs in the file you linked to. The Left speaker, Right speaker, and both together. But ALL THREE ARE AT THE SAME LEVEL! That's impossible That would mean that if you have only one speaker turned on, then turn on the other one as well, it does NOT get any louder in the room. I'm sure you can see what that is impossible. With REW, the combined level from both speakers should be 6 dB higher than the level of the individual speakers by themselves. That's because REW plays coherent sound out of both speakers. If it was not coherent, then the increase would only b 3 dB, but with REW it is 6 dB. Yet in your case, the increase is ZERO dB. That implies that you changed the levels between tests! :roll: It also implies that you did not carefully follow the instructions for doing these measurements. Here: viewtopic.php?f=3&t=21122

So you'll need to re-calibrate your system correctly, and re-do the tests, according to those instructions.

I'll get back to you on the other stuff later, but right now you need to fix whatever was wrong when you did the tests, re-calibrate, and repeat.


- Stuart -


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PostPosted: Fri Jul 13, 2018 2:48 pm 
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Location: Athens, Greece
Soundman2020 wrote:
That implies that you changed the levels between tests

Stuart thank you!
You are right as always!
I searched my notebook and guess what..it seems that for some reason I decreased the laptop output volume for measuring both so the can produce the same spl as of the single speaker. Dont really know why I thought of that at the time but it seemed right...Now thinking again it doesnt... :? :mrgreen: :oops:
Attachment:
1st test notes.jpg


Unfortunately there is no way I can remake a test with the empty room, because of the corner traps placement and of all the things inside which I have no other place to put them in.

More, I tried to measure the room as of now and there is something wrong with soundcard's left channel, I am hearing distortion on bass, grrrrrr
I can only measure one channel.. Till I find some cash for a new soundcard :oops:


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Last edited by almaelectronix on Mon Jul 16, 2018 6:52 am, edited 1 time in total.

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PostPosted: Mon Jul 16, 2018 6:51 am 
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Soundman2020 wrote:
I'll get back to you on the other stuff later


Would love to hear your thoughts on my earlier post if you find some time to spare :oops:


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