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PostPosted: Tue Apr 14, 2020 4:45 am 
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I designed/drew these up for him (John, don't worry, I didn't charge him but instead asked him to donate to the forum) :thu:
Attachment:
Atomicus Silencer 1.jpg

Attachment:
Atomicus Silencer 2.jpg

Attachment:
Atomicus Silencer 3.jpg

Greg


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PostPosted: Wed Jun 03, 2020 1:23 pm 
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Just a quick update on this... has taken me a while, mostly due to COVID related delays in getting supplies, but have finally got all my boxes built now. I went double layer, plywood and MDF, so they're pretty solid (and weight a tonne!)

Next stage is getting the rest of the room finished, and then getting the boxes up and all connected etc, but I have a few more things to do before I'm at that stage. For now, I'm parking them out of harms way.

A huge thanks to Gregwor, couldn't have done this without his help! :)

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baffle-box1.jpg


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baffle-box2.jpg


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baffle-box3.jpg


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PostPosted: Tue Jun 30, 2020 2:17 am 
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Just wanted to jump in and let you know that reading this single thread has increased my knowledge of HVAC ducting tenfold. Thank you!

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PostPosted: Sun Jul 12, 2020 9:15 pm 
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Impressively neat job! Can I ask what you used to cut the foam with? Best wishes, John.

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PostPosted: Sun Oct 11, 2020 9:24 pm 
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Update:

Finally. Pretty much done now. Boxes are all hooked up and room is all but finished. Plasterer is due next week. Has been quite the journey to get to this point, and I'm just glad it's nearly complete! Many thanks again @Gregwor.


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PostPosted: Sun Oct 11, 2020 9:27 pm 
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John Steel wrote:
Impressively neat job! Can I ask what you used to cut the foam with? Best wishes, John.


Apologies, I only just saw your post. For the foam, I used a sharp insulation knife I purchased from Amazon - https://www.amazon.co.uk/Connex-COXT670000-Insulation-Knife/dp/B007HKYCOG in combination with a large metal square to ensure straight edges. It was easy to cut, I just had to measure carefully as I'd built the boxes first, so everything had to fit quite precisely.

Updated pictures above. The one thing I'm having a bit of a conundrum about now is the airflow. I'd already settled on having the fan as extract - I could still change this to intake as I haven't hooked the fan up yet, but from all my research, extract was indicated to me as the best option. With the passive return though, I'm unsure if I should be using a filter or not on this, and if so, what exactly? I've seen quite a few of the carbon cylindrical types (used mostly for hydroponics), but these seem to be more commonly used for extract, and always seem to incorporate a fan. But because my intake is PASSIVE, I don't know if this is the correct thing to use, not least because it would significantly impact the airflow resistance. Any thoughts? Maybe I don't need a filter at all, just some mesh to prevent any creepy crawlies getting in. I certainly don't want anything building a nest inside my baffle boxes lol!


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PostPosted: Sun Oct 11, 2020 11:35 pm 
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atomicus wrote:
John Steel wrote:
Impressively neat job! Can I ask what you used to cut the foam with? Best wishes, John.


Apologies, I only just saw your post. For the foam, I used a sharp insulation knife I purchased from Amazon - https://www.amazon.co.uk/Connex-COXT670000-Insulation-Knife/dp/B007HKYCOG in combination with a large metal square to ensure straight edges. It was easy to cut, I just had to measure carefully as I'd built the boxes first, so everything had to fit quite precisely.

Updated pictures above. The one thing I'm having a bit of a conundrum about now is the airflow. I'd already settled on having the fan as extract - I could still change this to intake as I haven't hooked the fan up yet, but from all my research, extract was indicated to me as the best option. With the passive return though, I'm unsure if I should be using a filter or not on this, and if so, what exactly? I've seen quite a few of the carbon cylindrical types (used mostly for hydroponics), but these seem to be more commonly used for extract, and always seem to incorporate a fan. But because my intake is PASSIVE, I don't know if this is the correct thing to use, not least because it would significantly impact the airflow resistance. Any thoughts? Maybe I don't need a filter at all, just some mesh to prevent any creepy crawlies getting in. I certainly don't want anything building a nest inside my baffle boxes lol!


The advantage of having the fan on the supply side is that you can filter the air before it enters the silencers and it will also pressurise your room, which keeps dust out.

Paul

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PostPosted: Sun Oct 11, 2020 11:51 pm 
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Paulus87 wrote:
atomicus wrote:
John Steel wrote:
Impressively neat job! Can I ask what you used to cut the foam with? Best wishes, John.


Apologies, I only just saw your post. For the foam, I used a sharp insulation knife I purchased from Amazon - https://www.amazon.co.uk/Connex-COXT670000-Insulation-Knife/dp/B007HKYCOG in combination with a large metal square to ensure straight edges. It was easy to cut, I just had to measure carefully as I'd built the boxes first, so everything had to fit quite precisely.

Updated pictures above. The one thing I'm having a bit of a conundrum about now is the airflow. I'd already settled on having the fan as extract - I could still change this to intake as I haven't hooked the fan up yet, but from all my research, extract was indicated to me as the best option. With the passive return though, I'm unsure if I should be using a filter or not on this, and if so, what exactly? I've seen quite a few of the carbon cylindrical types (used mostly for hydroponics), but these seem to be more commonly used for extract, and always seem to incorporate a fan. But because my intake is PASSIVE, I don't know if this is the correct thing to use, not least because it would significantly impact the airflow resistance. Any thoughts? Maybe I don't need a filter at all, just some mesh to prevent any creepy crawlies getting in. I certainly don't want anything building a nest inside my baffle boxes lol!


The advantage of having the fan on the supply side is that you can filter the air before it enters the silencers and it will also pressurise your room, which keeps dust out.

Paul


So if the extract side has the fan (as I had planned), I am more likely to suffer with dust build up in the room and baffle boxes?

If the fan is on the supply side as you suggest, I assume the extract is then passive? Are there any disadvantages to this?

It's been a long time since I looked into this, but I recall the general consensus across what I read being that the fan on extract was better... I just don't remember why.


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PostPosted: Mon Oct 12, 2020 12:01 am 
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atomicus wrote:
Paulus87 wrote:
atomicus wrote:
John Steel wrote:
Impressively neat job! Can I ask what you used to cut the foam with? Best wishes, John.


Apologies, I only just saw your post. For the foam, I used a sharp insulation knife I purchased from Amazon - https://www.amazon.co.uk/Connex-COXT670000-Insulation-Knife/dp/B007HKYCOG in combination with a large metal square to ensure straight edges. It was easy to cut, I just had to measure carefully as I'd built the boxes first, so everything had to fit quite precisely.

Updated pictures above. The one thing I'm having a bit of a conundrum about now is the airflow. I'd already settled on having the fan as extract - I could still change this to intake as I haven't hooked the fan up yet, but from all my research, extract was indicated to me as the best option. With the passive return though, I'm unsure if I should be using a filter or not on this, and if so, what exactly? I've seen quite a few of the carbon cylindrical types (used mostly for hydroponics), but these seem to be more commonly used for extract, and always seem to incorporate a fan. But because my intake is PASSIVE, I don't know if this is the correct thing to use, not least because it would significantly impact the airflow resistance. Any thoughts? Maybe I don't need a filter at all, just some mesh to prevent any creepy crawlies getting in. I certainly don't want anything building a nest inside my baffle boxes lol!


The advantage of having the fan on the supply side is that you can filter the air before it enters the silencers and it will also pressurise your room, which keeps dust out.

Paul


So if the extract side has the fan (as I had planned), I am more likely to suffer with dust build up in the room and baffle boxes?

If the fan is on the supply side as you suggest, I assume the extract is then passive? Are there any disadvantages to this?


Yes, dust could be an issue.

I am not aware of any disadvantages, perhaps it depends on the climate? But, I am also not aware of the advantages of doing it the other way round that Gregwor was talking about.

There's other advantages to positive pressurised rooms; it helps to keep the doors closed up tight against the seals.

and this:

"In reverse flow conditions, when the air flows in the opposite direction of the
sound wave the effective speed of sound decreases slightly,causing the sound to take
a longer period of time to travel the silencer passages. This results in improved low
frequency insertion loss performance.

The opposite is true of forward flow applications. When the air is flowing in the
direction of sound propagation the result is decreased acoustic performance at low
frequencies and increased performance at high frequencies."

This is taken from a quote by Rod Gervais, who was referencing the Price Silencers & Panels Engineering Guide.

Paul

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PostPosted: Tue Oct 13, 2020 1:05 am 
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Paulus87 wrote:
Yes, dust could be an issue.

I am not aware of any disadvantages, perhaps it depends on the climate? But, I am also not aware of the advantages of doing it the other way round that Gregwor was talking about.

There's other advantages to positive pressurised rooms; it helps to keep the doors closed up tight against the seals.

and this:

"In reverse flow conditions, when the air flows in the opposite direction of the
sound wave the effective speed of sound decreases slightly,causing the sound to take
a longer period of time to travel the silencer passages. This results in improved low
frequency insertion loss performance.

The opposite is true of forward flow applications. When the air is flowing in the
direction of sound propagation the result is decreased acoustic performance at low
frequencies and increased performance at high frequencies."

This is taken from a quote by Rod Gervais, who was referencing the Price Silencers & Panels Engineering Guide.

Paul



OK, many thanks for that. I think I will switch to intake on the fan side. Worst case, I can always revert to extract, but from what you're saying it should all work out fine. :)


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PostPosted: Thu Nov 05, 2020 10:44 pm 
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Any thoughts? Maybe I don't need a filter at all, just some mesh to prevent any creepy crawlies getting in. I certainly don't want anything building a nest inside my baffle boxes lol!
I have put a filter box on my air intake path. It has a replaceable dust filter which I'm told is also insect proof. Some designers also choose to filter both the supply and exhaust paths. Bear in mind that whatever you install, the fan has to be powerful enough to meet the airflow requirements of your room and also overcome the static pressure inherent in your HVAC system. Every component added to the path will add a small amount of resistance to airflow or static pressure. This can be cumulatively significant and is tricky to work out although there is a very helpful app available from ASRHAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) which helps to detail static pressure for specific HVAC components. I'm sure you'll have seen this already, but if not, this thread is a must read. ATB John.
https://johnlsayers.com/phpBB2/viewtopic.php?f=1&t=21752

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