So a couple of updates about noise reduction.
Now I have 2x S9 and 1x L3+ working in the garage with the ducting adapters from Screwfix which are far from from flow optimised. S9 has 4ft of 4" ducting either side, L3 + only on exhaust. S9 are pretty much working on max fan speed and chip temp about 90C, I understand this is OK and S9 can go up to 110C. I have also put some bricks I had lying around on the sides of S9 and plywood on top. The noise has gone down from 80dB to about 70dB. L3+ does not respond well to noise reduction, it starts at 70dB but pretty much stays at 70C as it needs to crank up fan speed with the ducting attached and also I think the extra vent at the back let's more of the noise to escape. Intake ducting reduces flow a lot more than exhaust so I only have ducting on exhaust for L3+, noise has not reduced according to sound meter but pitch is more pleasent to the ears with less droning. with the proper ducting adapters results should be better. I also spoke to neighbour today and he is happy now with the reduced noise levels coming out of garage.
The 4" adapters I bought turned up yesterday but they were 117mm outer diameter on the ducting side so I could not use them and have sent back to the seller. Maybe it's for the best as I think I should have gone with 5" in the first place and have ordered 5" now from another supplier and also some 5" ducting.
I also bought Manrose 5" fan and have done some limited testing with it using only on intake. As I did not have any adapters yet I have just removed stock fans from S9 aligned it next to miner while the stock fans were still connected and running on the side. It was not ideal and some of air was escaping after running for 15 minutes the chip temps were 91C in the house with about 22C ambient temp so about the same like stucking 4ft of 4" ducting on either side of miner. It definitely has potential as it has the lowest noise so far at 65dB running air through miner and still leave about 20C temp reserve to max 110C for S9. The cooling should be improved a bit with the proper adapter. Another possibility is to stick a lower power exhaust fan something like 2500rpm/50dB to help it or use 6" Manrose fan which has higher CFM and static pressure. I have not received pulse generator yet so could not test it without stock fans connected but I can confirm that it stops hashing without fans connected. I can tell you those stock fans have some power, you cannot leave them running by the side of miner when take off, you need to hold them or tie or screw them down as they are trying to fly away.
I think for the rest of the evening I need to test how the temps are effected with just I I only use stock intake fan without exhaust to estimate the possible effect of using Manrose intake fan and a second lower power exhaust fan. And also to test how it works on L3+ in terms of cooling and noise level.
For the weekend I think I will make pigeon hole style shelving out of these blocks which are supposed to have great acoustic properties
https://www.buildbase.co.uk/durox-10...010511-2800748 Using blocks on the side and then 3 across on the top I can create holes 620mm long, 420mm wide and 215mm high which will be just big enough to put 2 miners with power supply on the side in each hole. If I use 3 blocks on the base to lift it off the ground a bit I will need 18 blocks to create 3 pigeon holes to house 6 miners. I could even create unit 3 holes high bby 2 holes wide using 33 blocks and slightly wider holes but I din't really have enough power supply to use all of them anyway. If needed I can then use fire resistant MDF with holes drilled for ducts to close off ends and reduce noise but so fat it looks like It will not be needed. Even if I end up using Manrose fans holes will be long enough to fit miner and fan.