Attic Shaped Studio

[Starlight]

Jennifer, I continue to be impressed by your seemingly never-ending willingness to explore further possibilities to improve your studio, complete with all the tricky maths that goes into making sure the weakest links are covered. You deserve the improved results you are getting and I trust they will improve further.

[endorka]

Thank you, that is really encouraging and helpful. As one of my favourite books said;

The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.

[garethmetcalf]

I can't believe you popped a rib doing this! I hope you feel better from that soon.

Congratulations on getting this far with it all.

I also have a similar amount of low frequency air noise with my fan on full blast, and my fan is considerably lower power than yours I think. As mentioned previously I bought a carbon dioxide meter and am using that to ensure the fan is moving enough air but not too much, which cuts down on noise. If you have an amazon account I recommend buying this, using it for a week to set your fan speed and then returning it (!). Is that too naughty? I fear I may have had mine too long to return now but if you plan it right you could do it.

https://www.amazon.co.uk/gp/product/B01 ... UTF8&psc=1

Cheers
Gareth

[Starlight]

Why would you return it? I bought mine last May, way too early to install it in the studio but I will want to know that I am pumping enough air in not just for me alone, which no doubt I will get used to over time, but when a group comes I can see at an instant whether the CO2 level is rising or at the alarm level. Tip: pick a CO2 meter where the audible alarm can be turned off so as not to accidentally interrupt a recording mid-flow.

[SoWhat]

Greetings Jennifer,

when a group comes I can see at an instant whether the CO2 level is rising or at the alarm level.

Time for another Frampton tune: Do You Feel Like We Do?

All the best,

Paul

[endorka]

Thanks chaps. The end of this part of the project us in sight, just got to keep going

Supply silencer installation begins seriously today. Yesterday I did a lot of measuring and designing about where and how to cut the hole in the ceiling of the room below for a hatch to allow ventilation filter changes. As ever, nothing is simple. There is coving along the borders of that room and it makes the hatch smaller than I had hoped. In theory should still work though.

The CO2 meter sounds like a good idea. I wonder how much exchange will go on through the ventilation ducts even with the fan off? Presumably the increasing partial pressure of CO2 in the room would promote passive movement of CO2 from inside to outside? And the reverse with decreasing partial pressure of O2 in the room. Of course if you have backdraft shutters installed this won't apply.

Cheers,
Jennifer

[garethmetcalf]

Your points about passive movement seem valid. Whenever I go into my room when the fan has been off the Co2 meter is reading around 340, which is the same as outside or thereabouts. Interestingly the thing that makes it go up the most is cutting and installing rock wool... weird, good thing I've been wearing a dust mask thingy.

Good luck with the holes.
Gareth

[endorka]

Thank you Gareth for confirming the theory in practice.

When reading EBU Tech. 3276 "Listening conditions for the assessment of sound programme material: monophonic and two–channel stereophonic" yesterday I noticed they specify acceptable limits for ventilation and other background noise in control rooms;

So I fired up the UMIK-1 calibrated measurement mic for a quick test in REW's real time analyzer. The mic was just sitting on my chair, not at the specified 1.2m height, but I reckon that's close enough for just now. First thing I noticed with the fan off was the 50Hz spike. Presumably some mains hum from something electrical in the room. It's barely perceptible though, a minor problem to figure out another day.

The room still looks like this, with the knee wall off on the right hand side where the supply silencer will go. So there will be more ambient noise from outside coming in than normal. It also means the static pressure in the ventilation system is lower now than when it is finished, so more air will be going through the exhaust duct just now, and so the ventilation noise will be louder than the finished system. I did the tests at night so outside ambient noise is quieter than daytime.

For comparison to the EBU standard I went for 1/3 octave smoothing and 16 averages. No fan;

With the fan at low speed. It is moving plenty of air at this speed, enough to stick a sheet of A4 paper to the register with a filter in front of it.

To my understanding the system meets the criteria for NR10. Only just at 125 & 250 Hz, but it is there. And I reckon it will be quieter when finished. I find this quite surprising, but there it is!

Cheers,
Jennifer

[garethmetcalf]

Brilliant test! I'll give the same a go myself. This is a great way of interpreting theory in practice. I'm amazed you have the time to be browsing such technical documents whilst in the midst of a studio upgrade...

Cheers
Gareth

[endorka]

Source of the post Brilliant test! I'll give the same a go myself. This is a great way of interpreting theory in practice. I'm amazed you have the time to be browsing such technical documents whilst in the midst of a studio upgrade...

What better time could there be? Some might say "before the studio upgrade" but what do they know?

This week I've been preparing the eaves bay for the air supply silencer and filter on the left hand side of this drawing.

The tolerances are very tight for such large objects, so it has been painstakingly slow work. As mentioned before, the only way to access the filter box to change the filter was to make a hatch through the ceiling of the room below. I had forgotten about the coving when doing the design, so the tolerances became even tighter in practice. What fun!

I made a structural frame from stud wood around the perimeter of the hatch. Rubber window seal was embedded in this in a routed channel to ensure a good seal. The hatch will be screwed into the structural frame. Screws are fine as the filter will only have to be changed every 3 months or so. I'll put a nice border around the hatch so it looks proper.

View from the eaves. Working in there with that gaping hole downwards to oblivion before the hatch structure was installed was not to be taken lightly. I made a horizontal "ladder" from stud wood so I could crawl along to the end of the space.

I'll be doubling up the plasterboard layer from above in that area in case noise from the filter is significant. Don't want it to get into the room below. Also after driving a 150mm diameter hole into the roof soffit for the duct, a bit more isolation there won't do any harm. There are just a couple of narrow offcuts around the hatch perimeter as a start.

I've installed the filter box and fortunately it is possible to change the filter from the room below. No photos of that though, will add soon.

Cheers!
Jennifer

[SoWhat]

Greetings Jennifer,

Amazing work, as always!

I guess Santa has another way in now too, although it's a tighter squeeze than the chimney.

All the best,

Paul

[endorka]

Brilliant Paul, thank you

Cheers!
Jennifer

[endorka]

I've added an extra layer of plasterboard above the existing one in this bay as a precaution against noise from the filter getting in to the room below. I've no idea if this is likely to be necessary, but it's now or never! It also might reduce additional outside noise coming in through the extra 150mm diameter duct hole cut in the roof soffit getting there too. The ventilation filter is at the end of the bay and has been attached via flex duct to the soffit vent. I added an extra noggin / cross beam to catch the silencer in the unlikely event it becomes detached from the stud wall.

The filter box is attached to the roof rafters with this "handle" made of OSB offcuts.

The filter box is attached to the handle with screws through the top of it into the OSB. A bit of sealant on each for a proper seal.

View of filter box through the hatch from the room below. It's pretty easy to reach through, open the box and exchange the filter cartridge.

Test fit of the partially assembled silencer in the eaves bay. Propped on various wood offcuts until the correct height is reached, is plumb and does not foul on the sides of the bay;

Wood props at the hatch end.

A test fit of the duct flange & duct to filter box. Once in place I drew round the flange to determine the correct position to cut the duct hole in the silencer. When properly installed I will use flex duct to connect the silencer to the filter box so they are acoustically decoupled.

Hatch cover, the wooden frame will be painted white to match the ceiling. The frame is larger than I had hoped, but necessary to ensure a reliable seal.

Inside of the hatch cover with double plasterboard layer. The frame has rebates cut for rubber seal.

Final silencer assembly. This one is the standard design, it didn't have to be stepped like the exhaust silencer as the house structure does not impede it in this bay;

It's also the original width, 20mm wider than the exhaust one, which had to be reduced to fit the narrower bay. It is a considerable size.

Flange in place. Let us hope my measurements were good!

[Starlight]

Source of the postWhen properly installed I will use flex duct to connect the silencer to the filter box so they are acoustically decoupled.

You are demonstrating how thorough you are with small but important details, not just on this connection but throughout your whole studio, as you have been from the start. Well done!

[SoWhat]

Greetings Jennifer,

Looks amazing (again!).

I added an extra noggin / cross beam to catch the silencer in the unlikely event it becomes detached from the stud wall.

Just the thought of this would keep me up nights.

All the best,

Paul