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Storm Mastering - a mastering NE room in a military fort
Old 17th September 2019
  #31
Gear Maniac
 
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Thanks !

Lot of work at the current studio going in September.
Next step will begin in October : the membranes.
Old 18th December 2019
  #32
Here for the gear
 

Any updates? This is one of the coolest DIY projects on Gearslutz

- May I ask which prime number did you use on the PRD's on the ceiling?

- Which type of membrane traps do you have in mind for the walls?

Keep up the good work!
Old 18th December 2019
  #33
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Quote:
Originally Posted by Gekk0 View Post
Any updates? This is one of the coolest DIY projects on Gearslutz

- May I ask which prime number did you use on the PRD's on the ceiling?

- Which type of membrane traps do you have in mind for the walls?

Keep up the good work!
Thanks for your interest ! I have been really more busy than hoped since september so the project has been paused.
I'm planning the next steps, and I should get back on a daily basis on the build from the end of december.

For your questions :
- It's p=157, 12x13 PRD
- Limp type of membrane traps. But they will be huge : 2x 140 cm x 240 cm + 2x 70 cm x 240 cm for the back wall and 2x 140cm x 220 cm for each side wall. That accounts for around 22 m² of membranes to deal with the low end. Tuning is planned between 29 to 37 Hz for the moment, but will build each symmetric pair time at a time, measuring, adjusting depth if need, and so on. All the surfaces treated by membranes should complement each other well. Then Waveguides in the front, which by their planned size, should have their lamdba/4 first absorption peak arround 65 Hz.
Old 18th December 2019
  #34
Very nice! I assume you've already thought of 'Fortified Mastering' for a name?
Old 31st December 2019
  #35
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Membranes !

Ok so membrane work has begun !

The idea is to utilise ground and masonry as a part of the membrane absorber boxes. But to be sure it will be airtight, I'm planning several barriers and caulking.

here is an isolated sketch :
Storm Mastering - a mastering NE room in a military fort-54.jpg
Framing wood is fastened to the wall with caulking under and both sides. Then the membrane box side is screwed on this framing wood, also with caulking everywhere. It will give strong support and more fail safe on the air tight part.

Here it is in real life :
Storm Mastering - a mastering NE room in a military fort-55.jpg

Acoustic measurements of those two membranes should be done this week-end
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Old 3rd January 2020
  #36
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A little bit of progress, each box for the big back wall membranes is done. Caulked with acrylic, then painted to cover the last bit of porosity. Might be overkill, but seeing all the fail stories with membranes on the forum, I prefer to overbuild them

Storm Mastering - a mastering NE room in a military fort-56.jpg

If everything goes well, tomorrow I'm attaching the membranes !
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Old 5th January 2020
  #37
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2 out of 8 !

Two membranes done out of 8 !



And here is a measurement, close to the sweet spot, mic did not move between the two measurements.



Tuning was calculated at 31 Hz, but actually knocking the membranes, they resonate at 26 Hz. But it seems to knock of quite a bit of that 33 Hz mode (which is not really an axial one, so at this place in the room, it quite a good result actually).

With 6 more membranes to be done, readjusting the formulas to predict better the other one (which will be tuned to some primary mode and/or primary SBIR null), I'm quite confident that it will bring the low-end decay into the "very-tight" territory
Attached Thumbnails
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Last edited by Storm Mastering; 11th January 2020 at 09:59 AM..
Old 8th January 2020
  #38
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Work has begun on the next pair of membranes, which will target the 0-1-0 mode (the lowest as the largest dimension is the width of the room).
Should be done by Thursday !

Storm Mastering - a mastering NE room in a military fort-59.jpg
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Old 10th January 2020
  #39
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4 out of 9 !

We are Thursday and 4 membranes are in place since yesterday !

Storm Mastering - a mastering NE room in a military fort-60.jpg

And in comparison 2 membranes vs 4. I have to investigate why my Umik-1 USB mic is outputting the mains 50 Hz in measurement at the new studio and why it doesn't do that at the current one.

Storm Mastering - a mastering NE room in a military fort-61.jpg

As you can see, the low-end decay is improving. I'm currently at 4 membranes out of 9, so I'm quite excited to see the decays when finished

As I said early, I'm also there to learn in the process, so I tried to put on the side membranes only, 5 cm (2") of fluffy firberglass, to see if it affects the behavior of the membranes. And it does, clearly, only with 2" so imagine the effect with 30-60 cm in front of them ! It seems to widen the Q and lessen the efficiency. I will do more tests when the 9 membranes are in place, but that small test with such a small amount in front of 2 out of 4 membranes confirms to me that I should go the hangers road in front of them.

Storm Mastering - a mastering NE room in a military fort-62.jpg

Next two weeks : building the remaining membranes and the wall PRD diffusers.
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Old 10th January 2020
  #40
Lives for gear
It's reassuring to see that you are able to get the decay times down in that 20-40hz range. In my build, I was assuming that this might simply be a floor resonance (slab on grade here as well?). I was planning some pressure based absorbers to give it a shot, and looking at your results it seems this will be worth while.
Old 10th January 2020
  #41
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Quote:
Originally Posted by RyanC View Post
It's reassuring to see that you are able to get the decay times down in that 20-40hz range. In my build, I was assuming that this might simply be a floor resonance (slab on grade here as well?). I was planning some pressure based absorbers to give it a shot, and looking at your results it seems this will be worth while.
Yes. But bear in mind the size of them, that range requires huge amounts of treatment. I'm also in a concrete shell with flush mounted mains so that excites a bit more of the low-end problems.

For the slab, mine is quite "small", around 7-8 cm, but under is a mixture of compacted grade with huge amount of rocks, you can't dig in it unless you have at least a wired puncher / small jackhammer.

Edit : a graph with none vs four. I will tune at least two of the remaining membranes under 30.

Storm Mastering - a mastering NE room in a military fort-63.jpg
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Old 10th January 2020
  #42
How you construct your membrane absorbers would be cool to see.
Old 10th January 2020
  #43
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Quote:
Originally Posted by johannburkard View Post
How you construct your membrane absorbers would be cool to see.
As shown in the sketchup a few posts above and in the pictures. Between them, it's filled with fluffy and some strings to maintain it from touching the membrane, some adhesive caulking on the box sides where it touches the membrane, a few staples to at first position and maintain it without it being loose or tensioned, and then the wood strip with a screw each 10 cm to compress the membrane to the box side and let it be really airtight.

Storm Mastering - a mastering NE room in a military fort-64.jpg

Nothing really fancy, just making triple sure that it will stay airtight.
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Old 10th January 2020
  #44
And how do you tune these?
Old 10th January 2020
  #45
Gear Maniac
 
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Quote:
Originally Posted by johannburkard View Post
And how do you tune these?
Using the traditional formula under isothermal conditions (i.e. filled with porous) : F = 500 / SQRT(mass per square meter of the membrane x depth of the cavity in cm).

In my case density is 8,57 (calculated with the weight of the 10 meter roll of SBR).

For the 30cm depth membrane, it should have been 31 Hz and for 25cm it should have been 34 Hz. But after measuring the first, I adjusted the calculation for the second pair to 29 Hz, with 25 cm.

Measured are 26 Hz and 30 Hz. So it adjusts the formula coefficient to 420 for the deepest and 435 for the other one. A bit hit & miss but not that far. Anyway, the bandwidth is pretty "broad" as you can see on the graphs. See, the resonance at 33 Hz got really knocked by the 26 Hz membrane.

The Q of this membranes are the beauty of them But as you widen the BW, you lessen the overall efficiency, so I guess that's why you need lot of them.
Old 25th January 2020
  #46
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Next !

Top framing for the next pair of membranes, tuned @ ~29 Hz. It needed a lot of caulking so I'm letting it cure well.

Storm Mastering - a mastering NE room in a military fort-65.jpg

Storm Mastering - a mastering NE room in a military fort-66.jpg

In the meantime, sanding and first layer of oil for one of the two backwall diffusers.

Storm Mastering - a mastering NE room in a military fort-67.jpg

Storm Mastering - a mastering NE room in a military fort-68.jpg
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Old 28th January 2020
  #47
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Boxes for membranes 5, 6, 7 & 8 in the making !

Storm Mastering - a mastering NE room in a military fort-69.jpg
Attached Thumbnails
Storm Mastering - a mastering NE room in a military fort-69.jpg  
Old 29th January 2020
  #48
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Caulking, caulking ... more caulking. At the end, I must count the number of caulk cans, it must be absurdly high.

Storm Mastering - a mastering NE room in a military fort-71.jpg

Storm Mastering - a mastering NE room in a military fort-70.jpg

In the meantime, both diffusers are oiled with two coats. Just need to build the boxes they go in, and paint that box in "panther black"

Storm Mastering - a mastering NE room in a military fort-72.jpg
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Old 31st January 2020
  #49
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Quote:
Originally Posted by Storm Mastering View Post
In the meantime, sanding and first layer of oil for one of the two backwall diffusers.

Loving the routed edges on these - very nice touch.
Old 31st January 2020
  #50
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Quote:
Originally Posted by Fred Pearson View Post
Loving the routed edges on these - very nice touch.
Thanks ! I sanded a little bit too much my fingers / nails at the same time
Old 6th February 2020
  #51
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Very low-end treatment done !

All the caulking dried, so it was time to finish

Fiberglass :

Storm Mastering - a mastering NE room in a military fort-73.jpg

Then preparing all the wood to tighten the membranes :

Storm Mastering - a mastering NE room in a military fort-74.jpg

and ... voilà !

Storm Mastering - a mastering NE room in a military fort-75.jpg

Storm Mastering - a mastering NE room in a military fort-76.jpg

Storm Mastering - a mastering NE room in a military fort-77.jpg
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Old 6th February 2020
  #52
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Internet !

On another note, the fort is really thick and buried in the ground, so it's shielding all communications. Wired internet access has very low speeds, so I needed another solution.

On the top of the fort, we get LTE, so I installed an LTE modem in an antenna, powered by ethernet, so I have a single cable going down. On that, I have a femtocell which creates a local cell phone network.

So here's my antenna :

Storm Mastering - a mastering NE room in a military fort-78.jpg

It is a directional antenna, and it is targeting a provider's antenna in the valley, just under our beautiful french alps
What you see in the axis is a concentration of enterprises, and there are big antennas there. I'm getting speeds of around 45 mbits/s in both download and upload, which is perfectly fine for a mastering studio.

The mountains in the background are called "Le massif de la Chartreuse", and on the top left of the mountain in the center, there is another matching military Fort, built at the same time.

Storm Mastering - a mastering NE room in a military fort-79.jpg

And lastly, yesterday night as I got out of my studio

Storm Mastering - a mastering NE room in a military fort-80.jpg
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Old 6th February 2020
  #53
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Amazing. Vista !!
Old 7th February 2020
  #54
Gear Maniac
 
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Final wall positions.

After a lot of measuring and tracing, final position of the walls and support for the waveguides have been set !

Storm Mastering - a mastering NE room in a military fort-81.jpg

Storm Mastering - a mastering NE room in a military fort-82.jpg
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Old 7th February 2020
  #55
Good job & good luck with your project.
I have no luck with membrane n past
So I appreciate if you tell your way
What material you use for limb membrane? Do you follow a calculations ? Or measuring then adjust? How do you decide what targeted frequency for each one ?
Old 8th February 2020
  #56
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Quote:
Originally Posted by bmss View Post
Good job & good luck with your project.
I have no luck with membrane n past
So I appreciate if you tell your way
What material you use for limb membrane? Do you follow a calculations ? Or measuring then adjust? How do you decide what targeted frequency for each one ?
Thanks.

see posts :
Storm Mastering - a mastering NE room in a military fort
Storm Mastering - a mastering NE room in a military fort

The material is 6 mm thick SBR. A lot of people are using EPDM also.
For the targeted frequency, it is a bit wide (about one octave) so not that critical. In my build, they are tuned to primary modes and SBIR Nulls.

On another topic, I have settled on the final back wall position.

Storm Mastering - a mastering NE room in a military fort-83.jpg
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Old 11th February 2020
  #57
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Waveguides !

The door.

Storm Mastering - a mastering NE room in a military fort-84.jpg

Building and hanging the waveguides, test fit !

Storm Mastering - a mastering NE room in a military fort-85.jpg

Storm Mastering - a mastering NE room in a military fort-86.jpg

Storm Mastering - a mastering NE room in a military fort-87.jpg

Preparing the back wall hangers tomorrow, and then I'll just have to wait for the insulation delivery
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Old 12th February 2020
  #58
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Almost done.

Some small ones left, a bit of tweaking there and there, and it will be done.

Insulation is delivered tomorrow, so I guess next week the hangers will be finished. I also cut the place for the diffusers, the hangers go around them.

Storm Mastering - a mastering NE room in a military fort-88.jpg
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Old 19th February 2020
  #59
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One half done !

The right hangers are done :

Storm Mastering - a mastering NE room in a military fort-89.jpg

just need to finish the left hangers and the diffusers and the acoustics will be 99% done !

Storm Mastering - a mastering NE room in a military fort-90.jpg
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Old 19th February 2020
  #60
EOG
Here for the gear
Progress!
I really hope your design works out, very interessting approach (regarding the hangers/wings). Would you mind explaining the concept a bit?
NE plus some self noise is almost failsafe, at least when someone knows whats what.

Have you found something on problems with TLs and wall mount/half space that Northward mentioned? Just curious.
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