Garden studio UK

Hi Stuart, Thanks for the advice and words of encouragement!

Slide your entire soffit out into the room a bit, slide the speaker over towards the middle of the room a bit, and reduce the angle a bit. The speaker should NOT be centered on the baffle... I used to think that was a good idea, but then I did the math and discovered that it's not so good...

...instead of making them in that "sawtooth" form, just make then as a flat panel that transitions from the soffit to the side wall. I call those "soffit wings".

Ok, so I've taken on board the speaker positioning advice and pushed them in as far as I can without having to lose any room length (the baffles literally meet in the middle). I've made two RFZ ray traces with "wings". The first is the simplest, it works, but needs a significant angle to reflect the further off-axis rays, also it doesn't have as large a RFZ. Also the wing's angle terminates very close to the speaker and I imagine this is not ideal as it limits the size of the parallel flush baffle surface. :? My second wing design seems to be a big improvement. By chopping a corner off the wing where it meets the baffle I can get away with a far less extreme angle. This reflects troublesome off axis rays in-front of the RFZ zone towards the opposite wing where it is reflected towards the back wall. This design allows the wing to finish further from the speaker along the baffle, as well as increasing the size of the RFZ. 8) I understand the second design is similar to my "sawtooth" form before, but there is a difference: The "cut-off" bit of the wing is parallel to the side walls. This means that reflections are still sent away from the speakers and not back towards the front wall as in my previous design, they also don't create an acute angled corner between the baffle and wing. I'm leaning towards the second wing design at the moment. They happen to have the bonus of using up less floor space and reducing room volume less too. 8) Can you see any obvious problems with the new design(s)? Thanks! Dan

Ok, so I've been steadily building the studio and I'm coming up to the point where I will be installing my outer skin silencer box. So I'd like some feedback on my design if possible. I have a three skin roof as I need ventilation below my roof deck. So the outer leaf silencer box will be screwed and sealed to the boards on the underside of the roof joists. The fan will be an inline fan and flexible ducting residing in the roof void. The inner leaf silencer box will be screwed and sealed to the top of the inner leaf ceiling boards. The ceiling is an inside-out design. Flexible duct will run between the silencers. I've calculated I need 180 CFM, the fan I'm looking at provides 211 CFM flow rate, so it seems ok: http://www.fansandspares.co.uk/shop/pro ... -125mm-dia. I'm looking at a 4 way ceiling diffuser on the inlet large enough to reduce the air velocity to 100-300 FPM. Let me know of any mistakes you can see in the design below, if possible. Thanks.

- It looks like you double your cross sectional area for the first little section of your outer leaf silencer box, but then as soon as it hits the end of the first baffle, it gets really small again. You need to maintain that large cross sectional area all the way to your register. So, your boxes need to be twice as big as they are right now. The point at which changes occur create noise. Having a tiny inner leaf silencer path that opens up huge right at the outlet will create turbulent noise and defeat your efforts to get quiet air movement. That's why you do it all right at the inlet of your first silencer. - How are you physically going to install your inner leaf silencer and connect it via flex duct (which isn't very rugged)? I suppose if you do it in modules, you could make it happen, but just something to think about. - Have you figured out what LVL studs will hold the weight of your ceiling with that super heavy silencer box? You need an engineers stamp to pass inspection, and in some cases even buy the wood. I want to see pictures of your build so far!!! Greg

Hi Gregwor thanks for the advice. That makes sense about the turbulence. I'll extend the box design. I was under the impression that I needed multiple changes in flow area throughout the box though in order to cancel out some noise. Are you saying this should happen in relation to the doubled volume though and not the original air volume? ... If you follow my thought process. Yes, I'm building the inner ceiling in modules, so I'll lift it between the joists and straddle 2-3 joists. My trada table gives me the max static load for joist sizes, so I'll double check it. You can see the build diary here: viewtopic.php?f=10&t=21269 Thanks

Are you saying this should happen in relation to the doubled volume though and not the original air volume?

If I understand what you're saying, then yes. Inlet of outer leaf supply silencer = supply duct size. As soon as the air hits the inside of your box, it should double in cross sectional area and remain that way, period. Return should be exactly opposite. I've attached a picture of my control room return silencers. The one on the right is the inner leaf and the one on the left is the outer leaf. Unfortunately, my situation isn't perfect. I don't have the space (due to my wooden sleeves running between joists) to maintain the cross sectional area. So, my inner leaf box is big and the outer leaf is small. I've obviously removed the tops of the boxes so you can see it better. Greg

Hi again, So this is my new silencer design. I've increased the size of the paths for the supply and increased the ducting to 150mm. I'm planning on using metal spigots caulked and screwed to the boxes to attach my insulated flexible ducting between the silencers and to the fan etc. I plan on using a 4 way ceiling diffuser for supply and probably exhaust too (mainly cosmetic reasons, continuity, and the datasheet says it's fine). Thanks

It looks awesome now!!!! Greg

Thanks Greg! I've ordered the materials to build my ventilation system so I'm happy. Back to construction! Dan

Are you using any kind of fan to draw stale air out of the room? That's the dilemma I'm running into.

davepettitt wrote:

Are you using any kind of fan to draw stale air out of the room? That's the dilemma I'm running into.

Yes, you use a fan that can provide 6 air changes per hour to provide for comfortable oxygen requirements. So mine needs around 200CFM or 340 m3/h. The fan I've installed is an inline mixed flow fan that has 2 settings with the lower setting only 26db and provides 410 m3/h at free flow so should be fine: http://www.ductstore.co.uk/acatalog/Sil ... -Fans.html

Dan! More pictures please!! Greg

Gregwor wrote:

Dan! More pictures please!! Greg

Yup, more pics on the build thread: viewtopic.php?f=10&t=21269

Waka wrote:

Hi again, So this is my new silencer design. I've increased the size of the paths for the supply and increased the ducting to 150mm. I'm planning on using metal spigots caulked and screwed to the boxes to attach my insulated flexible ducting between the silencers and to the fan etc.

Not preserved: New ventilation design.png

Not preserved: New ventilation design inside.png

Not preserved: New ventilation design below.png

I plan on using a 4 way ceiling diffuser for supply and probably exhaust too (mainly cosmetic reasons, continuity, and the datasheet says it's fine). Thanks

Dan, what cross section do your silencer boxes have? Will the duct between the two silencers be 150mm?

Dan, what cross section do your silencer boxes have? Will the duct between the two silencers be 150mm?

So the duct cross section is 17671.5mm2 and yes The duct between the silencers is also 150mm diameter. The cross section inside the silencers is 150mm x 250mm = 37500mm2 I'm currently having to redesign the inner leaf silencer as I have less space between inner and outer leaf then on my sketchup design. It's looking like I will have it between the inner leaf joists instead of on top of them. I'm going to post a new design for them soon (TM) Dan

Waka wrote:

davepettitt wrote:

Yes, you use a fan that can provide 6 air changes per hour to provide for comfortable oxygen requirements. So mine needs around 200CFM or 340 m3/h. The fan I've installed is an inline mixed flow fan that has 2 settings with the lower setting only 26db and provides 410 m3/h at free flow so should be fine: http://www.ductstore.co.uk/acatalog/Sil ... -Fans.html

Fire up that fan and let us know if it’s really producing only 26 dB. In my limited experience with “silent” mixed flow inline fans, the quoted specifications are usually miles away from reality. Worth checking before you install. I purchased the following fan which claims to produce only 33db on high and 26db on low. On both settings the fan is about 30db louder than quoted. https://www.fansonline.com.au/fanco-tt- ... 150mm.html

Fire up that fan and let us know if it’s really producing only 26 dB. In my limited experience with “silent” mixed flow inline fans, the quoted specifications are usually miles away from reality.

Yep. :thu: Agreed! - Stuart -

chrispire wrote:

Fire up that fan and let us know if it’s really producing only 26 dB. In my limited experience with “silent” mixed flow inline fans, the quoted specifications are usually miles away from reality. Worth checking before you install. I purchased the following fan which claims to produce only 33db on high and 26db on low. On both settings the fan is about 30db louder than quoted. https://www.fansonline.com.au/fanco-tt- ... 150mm.html

Ye I did take it with a grain of salt, and the measurement is from 3m, so 1m away is more like 38db. It's actually installed already, but outside of the sealed middle leaf in the ventilated third leaf void, so any noise has to go through the silencers or the leaves before entering the room.

Ok so I think I've got a workable design for my inner leaf silencers now. I definitely don't have enough room to place them on top of the inner ceiling joist, so I've had to make the box breach the leaf itself (I'm going to have to be extremely precise making sure this is sealed properly). I've created a boxed section on top of the silencer to take the air to the other side of the box as the gap isn't big enough for the flex duct to get through. This means the diffusers are central in the ceiling (which I like) and the boxes are quite compact. I think I've covered most of my bases with the new design, but they're a lot more complex then the outer leaf boxes. From above: Inlet images: Extract images: I need a filter to stop room dust etc getting into my extract silencer/fan so I've added a slight dropped ceiling section with an access hatch on the front to replace the panel filter. This dropped section consists of additional bass trapping and is located against the rear wall. All of the brown coloured insulation will be covered by fabric stapled between the joists and the seams covered by wooden strips.

Innovative design! The size of these things make fitting them anywhere so difficult. I'm re-designing mine right now and it's proving to be a nightmare, just like yours :-( Have you checked the specs on that register grill? Make sure it's quiet enough! Greg

Gregwor wrote:

Innovative design! The size of these things make fitting them anywhere so difficult. I'm re-designing mine right now and it's proving to be a nightmare, just like yours :-( Have you checked the specs on that register grill? Make sure it's quiet enough! Greg

They are indeed a pain! I phoned them before I bought it. It has 50% free area, and is 450mm x 450mm. This allows quite alot more than the flow in the silencers, so it looks good to me. Silencer cross section is 37500mm2 and flow through diffuser is 50625mm2.

Waka wrote:

Gregwor wrote:

Innovative design! The size of these things make fitting them anywhere so difficult. I'm re-designing mine right now and it's proving to be a nightmare, just like yours :-( Have you checked the specs on that register grill? Make sure it's quiet enough! Greg

They are indeed a pain! I phoned them before I bought it. It has 50% free area, and is 450mm x 450mm. This allows quite alot more than the flow in the silencers, so it looks good to me. Silencer cross section is 37500mm2 and flow through diffuser is 50625mm2.

Is the diffuser supposed to reduce the noise of airflow? Is there a reason why you chose to use this as opposed to a normal grille?

Is the diffuser supposed to reduce the noise of airflow?

The opposite actually. It disturbs the laminar air flow and it shoots the air in different directions around the room. No matter what, the change in air direction will cause some noise. Each diffuser will have an NC rating based on CFM passing through it. Here's an example: Nailor Catalog You can see the specs of the different types and the more CFM passing through them, the louder they are. You should be picking a register/diffuser that maintains the quiet operation we've all struggled so hard to achieve in our HVAC designs! Greg

Hi Greg, I wasnt aware of an NC rating. The company I got these from doesn't list anything on their website for it. Looking at the same design at another company shows it achieves 15-18 NC when below 300fpm. So I'm hoping mine will be the same! I might phone them Monday and ask for a datasheet. Dan

Looking at the same design at another company shows it achieves 15-18 NC when below 300fpm.

At what CFM? 10 CFM or 1000 CFM? To put that into perspective, 10 CFM @ 300 FPM is a lot less air moving than 1000 CFM @ 300 FPM. Both values matter when it comes to achieving low NC levels. I hope the one you picked up works out! Keep us posted. Greg

Gregwor wrote:

Looking at the same design at another company shows it achieves 15-18 NC when below 300fpm.

At what CFM? 10 CFM or 1000 CFM? To put that into perspective, 10 CFM @ 300 FPM is a lot less air moving than 1000 CFM @ 300 FPM. Both values matter when it comes to achieving low NC levels. I hope the one you picked up works out! Keep us posted. Greg

My fan draws 410m3/h. The diffuser I'm looking at is the same size listed as I have, with the neck area listed as 0.192m2. Giving a velocity of 410/0.192 = 2139m/h or 0.59m/s. The datasheet says 16NC at 1 m/s. So seems to be looking good to me (Assuming my diffuser is in anyway comparable to the the one that looks exactly the same and is the same size)