Hello everybody,

since the last 4 years, I've been on a project with 13 other guys, to buy an old military fort, which homed several crafts workshops rented by the town. But since the place is dangerous, the town didn't wanted to continue to assume the responsibility of the place.

It got complicated for some years but we became owners late march !

Here is the place :



So I have one casemate, which has quite nice dimensions : 12 meters in length, 6 meters wide, and between 3.6 and 5 meters high.





It will house for now my mastering studio, with a lounge on top, and a bigger space (which will be rented for now to get back a bit on my investment). The studio and lounge will be on the first 5 meters. In a few years, I'll build a bigger mastering studio, and the current one will become an electronic music production space, with some artists friends.

I'm actually at the acoustic building stage, and will update with posts to make that topic up to date

Awesome! Look forward to this build!

Isolation wise, the big rock walls between the casemates are 1.2 meters thick. They are dampened by up to 3 meters of ground above them, so I'm not really concerned with sound leaking up or by the sides. The windows and the door at the back go to a corridor, which connects all the casemate. The wall there are .5 meters thick. It will be filled with 50 cm concrete to match the density of the wall.
Front of the place, which connects to the outside word, will be concrete filled masonry units, and a big heavy front door.

Inside walls will also be built to give rigid and flat surfaces to act as the back wall of big membrane absorbers. They are also steel reinforced and will act as load bearing walls to the lounge above the studio.

On the acoustic side, I'm going for non environment.
Speakers will be my PMC MB1 tree-ways, flush mounted in a concrete filled wall. Listening position will be around 2.5 meters from the speakers. Walls will be shaped to redirected all the energy towards the back of the room, inside the ~1 meter deep back wall absorber. Side wall will house slightly "thinner" absorbers (~70 cm) but also targeted at the primary mode of the room (29 Hz).

The shaped shell is 27.5 m², and will be around 17 m² after treatment.



The ceiling height will be at 2.54 meters. This is kind of a compromise. The idea behind that is that in a mastering studio, you are in the studio, or you chill in the lounge after the session. Isolation to the lounge is not required.
The idea behind that is to have a not that heavy floor. Ceiling trap will be 345 mm of fluffy fiberglass with a denser rock-wool layer in front, which is very efficient to 100 hz, and becomes less efficient as we go down. The twist is, as we go down, the ceiling will increasingly let pass those frequencies to the lounge. That will make the ceiling height acoustically bigger than it is at low frequencies. To not be annoyed when a client goes take a coffee when I work, there will be an impact floating floor above, to greatly reduce the footsteps.

Walls going up !





Preparing for the speaker boxes.



Speaker boxes ! "Floated" on sorbothane hemispheres on X Y Z axis. Fluffy is here juste to tame possible resonances.







And we got beams !

wow! love the place
any floor plans?

Here it is !

Very cool space!

To continue the masonry required to build the doors. So that was the next step.

Panels cut. 3 layers of 22 mm MDF for the interior doors, 3 layers of 30 mm MDF for the front door.



Then the frames, with some space for the seals.



Screwing everything together.



Test fit ! Those doors weight a bit more than 80 kg.



Concrete formwork.



Front door frame, done with 100x200 mm beams, as the finished door with it's 3 layers of 90 mm MDF and two layers of 15 mm tempered glass window will weight 154 kg.



More masonry. Water evacuation integrated in corner blocks.



Result !

The tempered glass for the front door.



Small framing that will support the ceiling fiberglass.





Concrete painting began. It will be covered, so it's not to look nice, but to seal the concrete.

Now was the time to construct the ceiling diffusers. PRDs above the engineer's head, meant to interact with self noises and hoping not so much with the speakers. It was a bit of a gamble as they are close to the engineer's head, but first listening tests and measurements showed that they feedback around -25 dB in the ETC, which is great Will say more on that later !

First, the plan !



and then cutting all the pieces, more than 150 meters in total.



Test fit !



After sanding and one layer of rosewood colored oil.



Second layer of oil, inside the boxes.



Boxes painted in "panther black".



And fitted in the ceiling !

Exhaust.



Lights.





Intake and exhaust to the silencer.

And we start the ceiling treatment, lounge floor, all at the same time.

Insulation.



Fitting.





Ceiling structure. It connects to the beam and concrete walls by a small layer of SBR rubber that's leftover from the membranes. It's acting as a first impact attenuation layer.



Small technical room.



Panorama, ceiling almost finished.



Ceiling finished, front view.



First layer of the lounge floor.

Progressing fast!

Is this a northward design?

Cheers
Wiggy

No, but quite inspired ! I don't think it will reach the same benchmarks though, but I will go as far as I can with my current knowledge. Part of the 100% DIY build here is not only about the costs, but also because I like to learn, and for that, you also need to try.

I'm glad I did put the ceiling diffusers, because as the room is now (I'll go back to that in a few posts), when I tried to put 300mm fiberglass on side and back walls, just to test the response of the room above >100 Hz, under the diffusers, the room is quite nice to be in, but everywhere else, it's too "dead feeling" for my taste. As some guys said, NE room with only floor and front wall reflective can feel great for some people, but a bit less nice for others. I think that without the diffusers, it would have been too much for me. That test is also incomplete because no control below 100 Hz, will have to wait for the membranes for that. But since I'm doing things iteratively, I can correct / adjust as I go

I really think the back-wall PRDs are needed also, to add comfort at the speet spot, but also everywhere else in the room. For now, it doesn't seem quite comfortable at the client spots. Also, the concrete of the front wall is not sealed for the moment, so I guess it will become a little bit more reflective in the mids and highs when it will be done.

On another topic, the space I'm reserving on the back of the casemate is 6 x 7 meters, with a ceiling height from 3.6 to 5 meters, so if you look the minimum requirement of "you-know-who", it might tell you what are the plans in a few years

Caulking the ceiling, to make it airtight.



Another test fit :p



Preparing the 30mm MDF layers.



Two layers glued, preparing the third.



Last layer glued, now time to cover all the screws. That very expensive paint also act as a primer.



In place for mounting !



And then in place

what did you mean dangerous?is the area a crime hot spot?

Interesting thread and interesting place.

I read you use SBR rubber in some places. That will probably work out well as there will be no sunlight or noxious chemicals, nor high temperature or UV-light from spotlights where it is installed.

It might be worth to check up with the manufacturer though on the particular SBR rubber's age resistance if the places where it is installed are hard to get at when / if any service needs to be done in the "foreseeable future" (Note: Age resistance may vary quite a bit within the same type of elastomer.) Also check the labels on the rubber rolls for the batch number and cure date ("manufacturing") From the batch number any reliable manufaturer can always give info on cure date if it isn't clearly written out on the label already.

Compared to some other elastomer materials, SBR has a short shelf life. The attachment is from a US MIL-standard for various elastomers. SBR is usually quite cheap, EPDM affordable, silicone expensive (and not good versus mechanical abrasion) and viton very expensive. Indicated number of years is minimum shelf life ("approved" storage time) before actual use.

(I work at a company supplying materials to "heavy industry" in general. Nuclear plants very often require EPDM rubber and cure date less than year for positions where planned service intervals are many years in between. For them EPDM is often a first choice for that reason.)

In some places it is a ruin, big rocks are falling, some areas are tagged as mortal danger. The central area where the casemate are is structurally viable, as the structural engineer report says.

Interesting, thanks !

So at this point, I did a small measure to check the resonances with no wall treatment.

The speakers inside the boxes.



And a spectrogram with the mic against the back-wall. I draw the lines of the different behavior zones that are indicated on the bob gold room mode calculator. It matches quite well what we are observing here. The low mids are not that directional and so are quite absorbed by the absorptive ceiling. We see that by 300 Hz and up, waves seems to stay in the horizontal plan and so are allowed to decay way slower.



The 29 Hz resonance is the 0 1 0 mode. What's interesting is that it measures the strongest at the back-wall and corner instead of the side wall. Perhaps the shaping of the shell is responsible for that ?

To check that the geometry functions well, I put against the walls 300mm of fluffy fiberglass, and some small pieces of rockwool on some uncovered (for the moment) beams, around the speakers, etc.



What we see is that : a nice floor bounce !



And the waterfall : as we can see, 300mm of fluffy shortens a bit the 50-100 but is not enough for the low end. That's what the membranes need to attack. We can also see the uncompensated baffle step response.



Last one, for fun, a sweep only on the ATC dome : look at that nice, floor related, comb filtering.



And now, we are up to date

Great pics and great work!!!!

ps there's some issue with the last post, I can't see the pics

Re-uploaded and corrected !

Thank you! you've done a hell of job here. is it all DYI? it's clear that 300mm of fluffy fiberglass doesn't really tackle <100HZ range isn't it?

Yes it is !

Plan is to put membranes centered between 25 and 37 Hz depending on which wall, and at first, try with 300 to 600 mm of fluffy in front of them. But as Thomas Northward said so many times, porous in front of membranes affect their behavior, so I can try, adjust and so on.

If there is too much of a gap in efficiency between 50 and 100, I have a "backup" plan. Or I must say I don't really trust the fact that fluffy will work in front of the membranes, and the backup plan is the main plan

I will try it anyway, easy to test, just to see what happens.

But those measurements seem to match pretty well the modeling here : http://www.acousticmodelling.com/mli...4=300&v14=5000

Fluffy works better at 600 mm and stacked as to get the fibers parallel to the wave path instead of perpendicular as I did put my 300 mm layer here. I read somewhere back in the days that it lowers the GFR but can't find that reference anymore. Anyway, for those measurements, it was not meant to test the fluffy efficiency but to check if the geometry is working from the low mids to the highs. On that side, I'm happy

So the other way I was thinking about is to go with hangers. That's what I draw in my floor plan. As they are used in Mr. Newell's designs, they always are in front of membrane absorbers, and intuitively that seems to restrict less the airflow to the membranes. I know that intuitively is usually a red warning in acoustics, but I will try anyway, as the goal here is to learn.

I would be careful with PMC and their TL design. They do not like to be mounted in-wall in general, especially without a very particular and complicated type of compensation, and you will notice a 90° phase shift at the TL frequency...

The TL tends to create all sort of issues in the LF, that some people think are room related at first, but really it's the TL. So if you start chasing your tail, test with another speaker in there and look at differences.

These don't have ATC mid domes. They are Volt, like the woofer iirc.

Noted. As I said, I'll go the furthest I can in there with what I have.

For the mid driver, yes it is the ATC SM75-150S, I already unmounted them some years ago. Those MB1 are old, from the time ATC was still selling their mid dome to PMC.

Yes old ones used to rock ATC mid domes

BTW, since you already are here could you expand a bit on what type of LF issues I should expect from the TL ?

This is looking great! Congratulations!

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