The "Outdoor dunny" iso booth project

[Manning]

This follows on from a thread here:
viewtopic.php?f=1&t=6777

Quick summary - I'm building a 2.4m by 1.8m iso booth in the carport of my home. Rick dubbed it the "outdoor dunny".

General construction: In my last update I posted a few photos. Chris (Tasmanian) and Senad made some intelligent comments regarding the structural integrity of the walls (chiefly about the lack of floor-to-roof joists) which scared the bejeezus out of me, so a heavy rethink took place.

So far I have built the floor, two of the walls ('left' and 'right') and the ceiling. I've now redesigned the remaining two walls ('front' and 'back') to include floor-to-roof joists. Meanwhile, I'm adding an external skeleton of 200x50 joists around the existing (left, right) walls and over the roof. There will be four vertical beams spaced 600mm apart on each wall, each supporting a horizontal beam over the top, which will suspend the existing roof structure. The extra cost is justified for the peace-of-mind.

Door - I've researched door design to a ridiculous extent and have decided on two 1700x600 doors made of sandwiched yellowtongue and MDF. Each door will have a 45 deg bevel and be hinged to a 900x900 joist. These will go into the 'front' wall.

Window - Despite numerous suggestions to the contrary, there will still be no window. I'm reserving the right to use the iso booth as a pleasure dungeon, so windows are out. And to be honest, I just want this building project to end.

Ventilation - I'm building two 1500mm by 600mm fan-driven vent boxes to go on the back wall (an intake and an outtake module). These will have an internal maze structure containing a snaked 6m long 150mm insulated duct and a pair of DC driven silent computer fans @ 700 RPM. For the intake duct I'm building an additional 3.6m long duct box (yellowtongue, insulation and weatherproofing) that will connect to a remote window AC unit located in a nearby shed behind bricks.

Wiring - I seriously need to start thinking about wiring at some point. Obviously audio, plus electrickery to put light in the windowless dungeon, and some way of powering those silent computer fans for ventilation.

[Drumstruck]

Don't forget to paint a redback on the seat ;-)

For vision have you considered a monitor in the dunny and a security camera system? A few hundred $s and you can have video surveillance of your whole place, including the dunny, from your control room.

[Manning]

Absolutely... but of course, at the moment this falls into that whole "wiring I have yet to really think through" aspect.

For the record, the wife has now decided the dunny will be painted hot pink. For marital reasons, I have nothing further to say on that point.

[Drumstruck]

Pink is the go - the floor of my little place is watermelon pink

[Manning]

Well I have four walls and half a ceiling frame now.

Meanwhile I've been trying to find insulated ducting and silent fans to build my two ventilation boxes.

And where does one go to find insulated ducting and silent fans? To the DIY dope growers websites it turn out. Seriously those guys know more about moving air quietly than I ever imagined possible.

[jkhuri44]

according to michael Pollen (and it's no secret anyway)...there is more technology developed for growing marijuana, hydropnically and in dirt than there is for any other plant.

[audioio]

Forgive my ignorance, as I never embraced the rock lifestyle!

Why does marijuana need a quiet environment? (Or why do its growers?)

[jkhuri44]

^ to make the operation less conspicuous. imagine....

Sometimes it's grown legitimately in the US for medical purposes. State laws and Federal Laws differ in the US, so caution is usually practised.

Back to the topic! lol....

[Manning]

@David

Well I haven't smoked marijuana since about 1986, but given all the websites I ended up visiting last night, I imagine I've just added myself to every police watch-list there is.

But yes, based on what I learned during my travels, the 'self-sufficiency" dope crowd are the clear experts on silent ventilation (and also - although not relevant to my needs - on the cooling of exhaust air). I would imagine that noisy fans (plus the venting of large volumes of hot, moist air) in an apartment block might attract unwanted attention.

I found a mains powered 150mm fan which is (allegedly) quieter than the "silent" computer fans (which need DC adapters and stuff). I've got all the links at home, I'll add them here later.

Oh and Jamil - as an interesting aside, all of the websites I visited were Sydney based companies.

[jkhuri44]

you wanted to grow hydro tomatos? whats wrong with that

[Manning]

Hydroponic tomatoes - at 9 bucks a kilo I just might do that.

Anyway, someone someday will browse this thread and want to know about the fans I was talking about, so here is the link.
http://www.airefco.com.au/BLAUBERG_FANS ... 11496.aspx

The 125mm version has a claimed noise level of 29 dB at 3m.

[Manning]

OK some progress shots.

I'd run out of covered space to work in, so I spent a day rigging a tarp covering for my driveway:



Based on advice received, I redesigned the back and front walls to have vertical joists. The outer panels on the left wall are done, and there are some (non visible) support beams there as well.



To keep everything airtight, I've used a rubber sheet between every layer.

[The Tasmanian]

Looks just like a pro did it!!!!
Well done Manning.

[Manning]

LOL, as if.

But thanks anyway mate - your (and Senad's) advice has been absolutely invaluable.

[chribble]

looks great buddy!

[Hookemeister]

Anyway, someone someday will browse this thread and want to know about the fans I was talking about, so here is the link.
http://www.airefco.com.au/BLAUBERG_FANS ... 11496.aspx

The 125mm version has a claimed noise level of 29 dB at 3m.

Hi Manning, good research work finding those fans.

Keep in mind that 29db @ 3m equates to around 38db @ 1m. Sound attenuates by roughly 6db for each doubling of distance in free air. Not sure why they quote the noise level at 3 metres, probably the average separation between houses in high density suburbia.

These look like good quality fans. Reasonably quiet for a high pressure fan and looking at the specs it appears they can run on a variable voltage.

Couple of things to keep in mind.

In a studio situation you want deliver a large quantity of air but at a low velocity, this is why good studio airconditioning utilises ducts with a large cross sectional area. You basically want the air exiting from the supply registers at around 1m per second. This will be difficult to achieve with a 125mm high pressure fan.

Now I know it only an "Outdoor Dunny" studio but you may as well do the the best you can with what you've got.

It looks you're on the right track with plenums and your original idea of 700rpm fans seemed like a reasonable way of achieving a low velocity system. Now that you've moved up to a fan running at a minimum of 1960rpm into a 150mm duct you better make sure you've got your hat on tight.

So here's a couple of options:

Wire the 2 fans in series, this will halve their speed. In fact I'd go for the 150mm model as it has a lower base speed with a larger cross sectional area.

If you really wanted to get tricky you could plug them into a Variac and be able to really slow them down when you're recording a vocal. With a variac you could achieve a jet velocity of 1 metre per second.

Next thing is to design the plenum so the cross sectional area increases as the air travels thru it. This will reduce the pressure where it enters the room. I'd suggest making the plenum from white 16mm HMR Melamine as opposed to yellowtongue. Get rid of the ducting and create the duct by inserting dividers wrapped in insulation with a gradual widening of the aperture from inlet to outlet. It's easy to build.

If you can mount the fans in the shed that will alleviate any chance of structure borne vibration and any fan noise will be attenuated along the ducting. If you need to mount the fans on the room or plenums then make sure they are resiliently mounted.

Mount the supply and return vents at each end of the room with supply vent positioned so that airflow from supply to return is in the same direction as the microphone faces... so the air flows into the rear of the mic.

If it's a monitoring room then make sure the vents are positioned symmetrically.

Lastly it's imperative to introduce some fresh air into the aircon loop, especially if you're going to be spending long hours in there with doors and windows closed.
Easiest way to do this is to get some 50mm flexible pipe and hang one end outside the shed where the airconditioner is. Then cut a 50mm hole into the supply duct near the fan and gaffer the flexible pipe into it. The fresh air will be sucked in. Make sure the end that's outside the shed is hanging down so that water can't get it in when it rains.

OK that's my two bits... hope it helps.

[Drumstruck]

You've probably thought of this Manning so forgive me if I'm stating the obvious.... but the fans need to be isolated and solidly mounted as they can create a sympathetic vibration (due to tiny imbalances "amplified" by rotation speed).

[Manning]

Actually Greg/Ian, my fan research hasn't been that thorough - I'm still stuck on the "door" problem (although I'm making progress on that front).

I hadn't even looked at the RPM of that 240V fan, I just thought it was interesting at the time so I posted the link.

Based on your comments above, I'm now leaning back to the 700 RPM computer fan - particularly as the internal volume of the booth will only be 7 cubic metres. As far as air refreshing - I'm building two soffit boxes, intake and outtake. I'm always going to have fresh air, never to recycle. Less energy efficient I know, but also less likely to cause hypoxia.

However I've also got a plan for an air conditioner, and there are definitely no silent versions of those. Hence I'm toying with the idea of a lengthy (6+ metres) duct enclosure to an AC hidden in a shed (the duct enclosure would definitely have varying cross-sectional areas).

Still only at the "mental toying" stage on that front though - right now I'm discovering just how annoying it is when your yellowtongue sheets aren't all exactly the same size and you have spend an hour with a planer smoothing the edges out (or else your side panels won't be flush).

Apart from all that, your advice is brilliant, thanks. I suspect numerous other people will end up reading this.

[Manning]

Greg - some more responses to your comments...

Location: The mic will be positioned near the back wall facing the door (the door will go in the section that current has no frame on the front wall). If I build a lengthy duct, it will go to the left, down a small hill and around to the front of the house (which faces the bush). The lengthy duct idea appeals greatly, because if I end up using a noisy AC to provide cool air, I can also use it for normal ventilation in the winter (most AC's have a 'fan only' option).

The inflow will be aimed at the side/rear of the mic, at the top left of the back wall. The out-take vent will be at the bottom right of the front wall, next to the door. (At the bottom because CO2 is heavier than regular air).

I got my design for a plenum from an American company (www.dawbox.com) - I'd be happy to show them to you if you're ever around my way (the house is in Epping, Sydney). I'll be mulling over your design suggestions carefully though.

[Manning]

A question for those who aren't as electrickery-challenged as I am:

Assuming I use two fans like this one for booth ventilation - http://www.coolermaster.com/product.php?product_id=6510

How do I go about getting power to it? Could I just take a 12V/1A wall wart and rewire it, or is this really stupid?

[jkhuri44]

could just use a computer powersupply? a really small one. (obviously adding up how many watts u need)

[Manning]

Yeah I considered that but all the computer power supplies I've been able to find have existing fans on them, adding to the noise factor.

As I only need a small current (0.16A/0.28A max per fan) I was wondering if a wall-wart might get the job done.

[tony]

Wall-wart should be fine. We do exactly that for ventaling box's on theatre sets all the time.

[Hookemeister]

The out-take vent will be at the bottom right of the front wall, next to the door. (At the bottom because CO2 is heavier than regular air).

Hi Manning,

CO2 is not going to be you're problem if you've got a fresh air intake.

Your biggest problem in summer will be getting rid of hot air.

Hot air rises... Cold air falls.

If you have the out-take vent (return air) at the bottom of the wall you will be sucking out the the cold air you've just brought into the room.

So keep both the supply and return air at ceiling height and as far apart as possible.

Assuming I use two fans like this one for booth ventilation - http://www.coolermaster.com/product.php?product_id=6510

Once again Manning you get full marks for research.

This looks like a excellent fan, nearly too good to be true. 19dba Noise and 100CFM, which equates to roughly 550 cubic metres per hour, at only 3.6 watts... that's super efficient. I'd like to see that.

I'm just not sure whether they could move that volume of air down a long duct and thru a plenum. The plenums will create an impedance to airflow. This application is very different to blowing air across a power supply.

How do I go about getting power to it? Could I just take a 12V/1A wall wart and rewire it, or is this really stupid?

Let's assume you can move enough air with two of these fans, then I'd suggest running them from a 12V car battery or a sealed lead acid battery or even a lead filled snow shoe, trickle charged from a small solar panel on the roof of your house. Now there's a DIY project for you.

Well that's my bit for the environment and Frank Zappa.

mmm... I wonder if I can claim a carbon credit for that suggestion?

Your move.

[Manning]

Please don't hit me in the nose or in the fin.

Good advice, as always. I really need to test one of these fans across the ducting and see what happens.

Shall advise.

[Senad]

The "dunny" is looking great Manning!

[Manning]

It's come quite a bit further now, I'll upload new pics soon.

But dear God, I want this project to end. I fondly imagined it would take six weekends or so...

[Senad]

Yes, piccies please.

[jkhuri44]

It's come quite a bit further now, I'll upload new pics soon.

But dear God, I want this project to end. I fondly imagined it would take six weekends or so...

you're doing a lot better than me, im building a guitar cabinet...its smaller, easier, and cheaper, yet still is taking foreever.

[Manning]

Progress update:

Roof is finished, three out of four outside walls done, started on the inside walls. I've built a ventilation box (not shown) but I've been avoiding the door.

Also that's not a gap in the roof frame, it's a stray piece of black duct tape.



Anyone know anyone who can make a custom patch panel? I need four XLRs, two headphones, USB and HDMI. It will go in that area at the left that currently has no insulation.