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PostPosted: Tue Jan 14, 2020 11:23 pm 
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Joined: Tue Sep 12, 2017 9:14 pm
Posts: 11
Location: Tyrol in Austria
Hi everybody!

Perhaps this thread should rather be called "How NOT to do it and (roughly) still succeed" but that would be a bigger debate.

Three years ago I set out to build a house in the Austrian countryside with the help of my dad's workmanship. The intention from the start (though somewhat ill defined) was to build it in such a way that I could use the entire basement as a studio for music and video post-production purposes. The available budget was good after I had some well-invested capital from monetary compensation due to a climbing accident with major back injuries some ten years earlier. So much to my background.

Two years ago I made a post right here – already well past most of the construction and past most of the admittedly ongoing planning stage – and our dear Stuart graciously and patiently took the time to explain to me in detail all the ways in which I had gone wrong and how we could have done the same thing better for less :lol:.

A well-needed punch in the gut at that point.

Stuart advised me strongly to halt construction and finish the plan before doing anything else! And while we did pause for a while and I studied and modeled like crazy, we eventually moved forward and completed the studio as well as we knew how.

Not least to my own surprise, the studio turned out wonderful in almost every respect. Insulation is fantastic, HVAC turned out very effective and also whisper-quiet (I can post details on how we solved our issues in a separate post if anyone is interested), the room acoustics in the live room are very pleasant and versatile, the entire space looks, feels, and sounds amazing, but alas, unfortunately, it is currently not a very reliable mixing environment, no surprise to anyone looking at the dimensions of my CR.

I 've been tracking several bands in the studio over the last year or so since completion, and I always had a blast mixing things in this wonderful space, but every time I tried my mixes outside of my CR, the mixes fell apart, leading me to go over and over them, often in vain. Only when I started mixing primarily on headphones have things begun to sound like I wanted them to outside of the studio too... Obviously that is an unfortunate outcome in light of all the money and effort that was put into this place.

As I have outlined in my original thread, the room is virtually square (4,99m long, 4,78m wide and 2,99m tall), making it modally sub-optimal from the get-go. Additionally, I designed the room with the studio window to the left of the console favoring a TV screen in front of it for post-production, and I had always had the room in mind with the speakers firing down the shorter dimension, rather than the longer one as I had later learned would have been preferable.

All of this was addressed comprehensively by Stuart in my original thread from two years ago here.

I took on-board what I could, but also improvised to some significant degree...

And while – mostly through dumb luck – the room response overall turned out quite decent, REW points out a number of significant problems I now hope to resolve with your help.

Specifically, my measurements show three modal holes at around 87Hz, 146 Hz, and 185Hz that have narrowed and weakened with treatment, but not been eliminated.

Attachment:
Room Baseline Empty (Spec).jpg

Attachment:
Room Baseline Empty.jpg

Attachment:
Room with current treatment (spec).jpg

Attachment:
Room with current treatment.jpg


A more comprehensive set of measurements can be found here on my dropbox.

Here a few pictures during treatment and how it is now.

We built two large soffits positioning the speakers close to the front wall, a bit outside left and right of the 25% width mark, all solidly mounted with plenty of mass, with the speakers fully floated on sylomer pads (I have done the calculations, too).

Attachment:
IMG_20180918_162237.jpg


We then built large cages around the back of the speakers and attached airducts to release excess heat up and away from the speakers back into the room. We stuffed the top space behind and above the speakers with Rockwool and fluffy insulation and used 5 hangers of varying sizes on each side for the space underneat the speakers.

We put in 16cm of cm of rockwool RW3 in the center front section and 8cm along the sides to act as broadband absorption, used the same material to build two superchunks in the rear corners, (very similar properties to OC703 according to my research), put another layer of 8cm of RW3 along the rear wall and hung 5 more large hangers of varying width in the center of the rear wall.

We used a stiffer insulation material used for under-floor insulation fitted into the fabric frames (2 cm thick) to act as semi-absorbant waveguides, and used the same technique for the ceiling clouds, only that we mounted those frames directly on a 2cm thick, rigid plasterboard (correction: actually it's fiberboard, similar to homasote] backing, to guide the reflected energy towards the back wall where it can be absorbed.

Attachment:
IMG_20200114_134845.jpg

Attachment:
IMG_20200114_134938.jpg

Attachment:
IMG_20200114_135016.jpg


Finally, a few more shots of the rest of the studio, just for curiosity's sake!

Attachment:
IMG_20200114_135201.jpg

Attachment:
IMG_20200114_135046.jpg

Attachment:
IMG_20200114_135122.jpg

Attachment:
IMG_20200114_135134.jpg


I could go on about plenty of details regarding our build, but perhaps I'll best write a diary in hindsight once all the main issues are actually resolved!


So now: my question to you all is simply this:

How might I try to resolve these last critical acoustical issues in my Control Room, so that I can finally get to use this great space to its fullest potential?

Thank you all in advance! I'm looking forward to a great discussion.


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Last edited by oslthom on Wed Jan 15, 2020 2:12 am, edited 1 time in total.

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PostPosted: Wed Jan 15, 2020 12:43 am 
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Joined: Tue Mar 25, 2008 3:31 am
Posts: 198
Location: Cork Ireland
Fabulous looking work, but I am sorry to be the one to point out some Acoustic oddities.
Please post the .mdat, I am not convinced that your biggest issues are modal.
The clouds are very thin and the plasterboard will ruin any possible airgap effect. Never seen one like that before.
Hangars always strike me as a tad uncertain. But if I were doing them I would copy exactly a proven example. Never seen plasterboard.
Flush mounted speakers are flush to a hard boundary, which extends the baffle and eliminates cabinet and baffle edge effects.
I have Mixed many recordings over the decades. My biggest issue has always been translation of the mixes to the outside real world.
I too relied on Sennheisers. HD380, now 650. They are home to me. Canopener Studio is very helpful for headphone mixing.
By far the biggest and most common translation problem I have found is that listening in CRs is way too bright, leading to dull mixes.
Here is what people hear in their homes and cars. It is 6dB tilted from flat. (Harman say 1dB per octave)
Headphones are designed with a similar response. Nobody listens on Audiometric Lab Headphones.
Review the Clouds, perhaps repurpose those hardbacks as hanging deflectors in your live rooms. Dirac Live is excellent for creating a B&K curve.
DD

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http://www.irishacoustics.com
http://www.soundsound.ie


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PostPosted: Wed Jan 15, 2020 2:05 am 
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Joined: Tue Sep 12, 2017 9:14 pm
Posts: 11
Location: Tyrol in Austria
Thank you, Dan!

I have posted the link to the latest .mdat measurement collection via my dropbox.

Here is the link one more time, to save you looking for it.

I would greatly appreciate if you could have a look at it.

As to the "plasterboard", I seem to have used the wrong term there. It's actually a fibreboard, very close in properties to Homasote, only that I couldn't find the actual Homasote product anywhere here, nor accurate specs in terms of density. I suppose I should be able to calculate the density by measuring the weight and exact volume of one of those boards should that be helpful.

It was an experiment, but It seemed to be doing what I wanted it to, at least roughly, namely controlling the bottom end reverberance.

As to the clouds, they too were an experiment, and I may be well served as you suggest to rethink my entire ceiling solution and try to use the existing frames as deflector elements in the live room.

I do think the main issue should be modal (though there may well be other issues I'm oblivious to) because the positions of the greatest dips in the spectrum correspond very closely to the calculated modal response for a room of my particular dimensions (4,99 x 4,78 x 2,99m). If I am reading the data incorrectly, or missing a few things please let me know! I'd love to understand the problems I am dealing with as much as I can!

Quote:
Flush mounted speakers are flush to a hard boundary, which extends the baffle and eliminates cabinet and baffle edge effects.


I'm not sure I see what you're pointing at here, can you reiterate? I understand the concept of the "infinite" baffle and thought I had applied it correctly, is that not the case? Or do you mean to say that this is the reason why consumers are usually not listening on quite so bright systems? Sorry about my confusion...

I have certainly noted that my first few mixes were way too dull and had to consciously compensate for this effect. The HEDD Type 30 are on the bright side in general, due to the ribbon tweeters. Very transparent and revealing, but certainly a pair to get used to.

I'll also give canopener Studio a try, and look into Dirac Studio, thanks for the tips!


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PostPosted: Wed Jan 15, 2020 9:17 am 
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Joined: Fri Nov 24, 2017 12:07 am
Posts: 30
Location: Hastings, East Sussex, United Kingdom
Congratulations Oslthom,
Your studio looks tremendous and it's a great achievement - I'm sure with the collective knowledge and help of this community it will soon sound as good as it can.
Quote:
HVAC turned out very effective and also whisper-quiet (I can post details on how we solved our issues in a separate post if anyone is interested

I, for one, most certainly am interested in how you did this. I look forward to hearing more about your design and build.

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PostPosted: Thu Jan 16, 2020 5:16 am 
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Joined: Tue Sep 12, 2017 9:14 pm
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Location: Tyrol in Austria
Thanks John! I hope so too!

My guess or hope is that I will be able to improve the sound in the room by rethinking my ceiling treatment, but I'm intrigued to hear a more educated opinion.

I'll outline what we've done since my conversation with Stuart two years ago, and explain our HVAC solution in particular, along with some other details sometime this week. It's been an incredible journey and learning experience, to be sure.


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PostPosted: Thu Jan 16, 2020 8:53 am 
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Location: Hastings, East Sussex, United Kingdom
Looking forward t reading about it!

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PostPosted: Thu Jan 16, 2020 9:53 am 
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Joined: Tue Mar 25, 2008 3:31 am
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Location: Cork Ireland
Looking at the .mdat, your CR is quite amazing. Look in your Waterfalls, I see no modes. I do see an SBIR dip which may well be the floor bounce.
You could try a blocking element under the desk.

In the ETC Left fully treated, I see a protruding reflection at 3.5mS. What is that? In the individual L and R measurements I see strong comb filtering at HF. Probably the mixing desk. You could try angling it. Or if you are not actually mixing on it, perhaps behind or to the side.
I have seen homasote used for hangars and I believe it has some sort of damped resonant absorption also.
So as you were, this is really really well done.

Overall your FR looks brighter than flat. Real world listening conditions are tilted at least 6dB downwards from LF to HF.
This issue for translation is a common one. Most people listen to a B&K curve. In order to mix for them, you need to hear it.

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http://www.irishacoustics.com
http://www.soundsound.ie


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PostPosted: Fri Jan 17, 2020 7:05 am 
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Location: Tyrol in Austria
Thank you Dan! That's very encouraging to hear!

So what I thought must be a modal issue at around 87Hz is actually an issue with SBIR? How would I best remediate that?

I will definitely try to eliminate any potential floor bounce and see if it makes a difference.

Would it make sense to rethink my ceiling treatment? I have a suspicion that a more substantial ceiling cloud with deeper broadband absorption would help a great deal, but I would appreciate a more sophisticated proposal.

I've also found that reflection you mentioned at 3.5ms in the Impulse Response of the left speaker measurement. I suspect it is the iMac I have sitting to the left of the console. I will move it further away for the next measurement to see if that was actually it. I might then find a place further back in the room for it or actually switch to a tower PC sometime down the line.

I've also tried canopener studio last night and will continue to test that for the time being, and I've looked into Dirac Live and I plan on trying out the dirac processor in my room tomorrow. Thanks again for the recommendations and for taking the time to look at my measurements!

Thom


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PostPosted: Fri Jan 17, 2020 4:04 pm 
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Location: St. Albert, Alberta, Canada
Thom,

Here is the distance to add to the distance from your speaker to your measurement mic. Do the string trick and find out exactly what it's bouncing off of!
Attachment:
Thom Reflection.png

Greg


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PostPosted: Sat Jan 25, 2020 10:27 pm 
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Joined: Tue Sep 12, 2017 9:14 pm
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Location: Tyrol in Austria
Hey everybody!

sorry for the delay, I've been swamped in projects and got distracted by family matters. All good now.

Thank you for the hints, Greg!

My speakers sit pretty much exactly 2m from the sweet spot, angled 45° out from the center (pretty much the maximum in terms of justifiable spread from what I've read).

I cut a piece of string at 3,2m, adding the additional 1,2m which the reflected signal had to take to the speaker distance and taped it to the speaker and the measurement mic.

Pulling the string taut towards potential reflection points showed me that three elements on the left side of the room could have been responsible (the iMac, the ceiling cloud, the floor), but only the floor displayed a reasonable angle of incidence and reflection.

I placed a bit of insulating material around the sides and back of my console as Dan had suggested before (2cm thick stiff glass-fiber boards, encapsulating pretty much the whole sides and back of the console) and the reflection disappeared.


Doing this obviously didn't do much or anything in terms of SBIR or combfiltering, though it did bring down the very high end a little bit, rolling off about 2-3dB between 10-15kHz.

I still suspect that I will need to install a bigger and more conventional ceiling cloud above the desk to address the biggest chunk of this issue, along with angling and positioning my desk in such a way the issue of comb filtering becomes less of a problem.

I also thought that I could increase the size of my wooden baffles, should you guys think this will help.

Other than that (and maybe even those measures aren't what I should really be doing) I'm not sure what to do next.

If any of you have any ideas or further comments, I would greatly appreciate it!





In the meantime: let me outline a few more of the things we've done in terms of HVAC and construction in general, for anyone who might be interested:

So as you might have seen in my thread from two years ago (linked in the opening post of this thread) we basically built three decoupled basements (CR, LR, and general area), separated by a special kind of cork (Pronouvo Kork 1073) and yet joined by an elastic rubber band (to keep water from coming in through the gaps) and dowels wrapped in sylomer, just to prevent any potential if not expected slipping of the 3 separate foundations.
Attachment:
IMAG0481-2.jpg


As Stuart already explained in detail, much of this was overkill, and a single large basement with several room-in-room constructions would almost certainly have been cheaper and less of a hassle to build.

We made the entire Live-Room Cubature using poured concrete, all of the outer walls of the whole structure as well, then built the inner walls of the control room and towards the general area with cement bricks, filled with more cement. Quite a massive structure.

We filled the airgap between those double walls with rockwool, leaving about half of the width as an actual airgap.
Attachment:
Doppelmauer.jpg

Attachment:
Doppelmauern-2.jpg

Attachment:
Studio-Window.jpg


For HVAC, we opted principally for a fresh-air system of the kind as it is commonly installed in Austria or Germany for living spaces.
Attachment:
HVAC-Intake-and-Outlet.jpg


Note the air intake on the far right, going through intake filters, then a muffler, and into the machine. The in- and outlets to and from the rooms goes through another pair of mufflers and then into distribution boxes, from where the air travels through several tubes of 7,5cm diameter to and from the rooms, as seen here:
Attachment:
Ductwork.jpg


As Stuart pointed out quite correctly, the way we did all this was not exactly ideal, as the airflow through these pipes was very fast when I ran the HVAC fans on the required level that would get me the appropriate exchange rate. That, and any vibration in the ceiling slab would have a very easy path into the airflow and hence into my recording space...

We then built a room-in-room structure for the Live Room and the Control Room. Again, probably overkill in light of the already massive construction and isolation measures, but as it turned out an essential part of how we would come to solve our newly found HVAC problems.
Attachment:
RoomInRoom.jpg


Again, there are certain problems with this and there would have been better, cheaper, and easier ways to go about this, but this is what we did. We built a wooden structure to sit within the room ontop of our screed floor (which btw. contains two conduits the size of our HVAC ducts for our audio snakes and a network cable.) and left 2cm to any of the other 5 walls. We used Sylomer pads screwed to the outside of some of the 2x4s to ensure this distance without any stiff contact points (again, using more intuition than calculation, much to any knowledgeable person's dismay).
The roof of this inner construction of course used beams of an adequate size, with 6cm width IIRC and 24cms in height.

Between those beams, we placed a pair of HVAC baffle boxes for each of my in- and outlets, one only connected to the outer concrete structure, and the other only connected to the inner wooden structure. The two were then joined by a flexible, insulated airduct.
I can't seem to find a photo of the actual boxes installed, but this was my sketchup for them, which is very close to the actual construction.
Attachment:
HVAC Schalldämpfersystem verbaut.jpg

Attachment:
HVAC Schalldämpfer 1.jpg


We then put OSB boards in place, followed by a layer of plasterboard, caulking and sealing as one should. For the Outlets we decided to put in place separate covers which we could remove, should we have to do any maintenance on any of the baffle boxes at some point down the line. Of course, we sealed them using silicone for the time being.
Attachment:
OSB-and-plasterboard.jpg


Oh, and as you can see we also used three of the gaps in between the ceiling beams to insert skyline diffusers. We left three sealed cavities in the ceiling and built the diffusers to fit snuggly in place. Before we put on the plasterboard we screwed them in place and sealed everything again. Each diffuser consists of three square arrays glued to itself, between which we left a tiny bit of space to allow for potential expansion/contraction of the wooden pieces. I calculated them to be effective in a range from about 500Hz to 3500 Hz, if I remember correctly. I still have the calculations printed out somewhere, only where is the question!
Here they are during assemly:
Attachment:
Skyline-Diffusers1.jpg


We then built all inner geometry attached directly to the inner room constructions and placed all treatment for the CR as outlined in my initial post I think.
Attachment:
Inner-geometry.jpg


For the live room we created several angled sections filled entirely with rockwool, a couple of sections filled with hangers behind wooden walls (but with air-ports behind acoustic fabric), and used additional acoustic foam absorbers to control resulting flutter echoes between floor and ceiling (a solution I still want to improve upon with well-placed ceiling clouds).

All in all, not perfect, not exactly done as one should do it, but also really not bad I would say.

Again, I could go into much more detail. Should anyone wish me to do so, don't hesitate to ask!

Here once more the results as of now:
Attachment:
IMG_20200114_134845.jpg

Attachment:
IMG_20200114_135134.jpg


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