I was astounded also. Such a difference.
That original exhaust fan did 13,000 RPM, that’s what my 4" angle grinder does - High pitched whine.
For a self-contained system that was required, no room for a massive slower spinning fan. A lot of people have purchased the cheap Chinese alternative laser, only to discover vast improvements by adding to it. That’s all we are doing, improving the design beyond (or in spite of) what manufacturing standards require.
The noise reduction is amazing because the larger impellers or fans, the boosters don’t need to spin at that high an RPM = Piece. 
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Yes. I made a simple adapter and shared the design here, but buggered if I can find it now.
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When everyone was saying it was quieter you were still saying “WHAT?! I CAN"T HEAR YOU”
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I have the 4" vivosun and i would recommend something with a higher cfm. I find it lacking on prints with heavy cutting.
yeah, just did a longer acrylic cut and i can see that it’s a little less functional for that. i’ll keep using it for now to be an additional fan and let it keep evacuating odors after the cut stops. but i’m looking at the 6" fans. i have to make sure i have room in my setup to fit whichever one i buy. it’s a snug fit behind there. especially since i like my hard elbow. but maybe i’ll have to give that up.
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I have the Vivosun 6" and it’s insanely quiet compared to the 4". It makes me want to get an 8" and adapt it from 4" inlet to a nice breathable 8" outlet. I mounted the speed control near the GF button. It makes for a nice compliment when engraving slate a fan speed 1. PRICELESS!!
I can actually listen to music while using the machine now!
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I have tte 195 cfm vivosun and most of the time I use both but if there will not be a lot of smoke I use just the Vivosun
yeah for simple cuts i use just the external, when its like 30mins of cutting plywood i turn on the fan in the glowforge and just deal with the noise. thinking of swapping out the fan tho for the 6" one above
I’ve been thinking of doing this too. Problem is, I have a 4” vent in my wall. I keep hearing that the 4” fan isn’t sufficient, but I don’t think putting a reducer from the 6 inch fan to the 4 inch vent makes any sense either. I can’t see any obvious way to increase the hole size, & I don’t really want to cut another hole in the wall. Any suggestions?
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This sounds amazing , but I am confused do I just add to the back of the machine that that i have already going out the window or do I need something extra for it ? Do i turn off the glowforge fan to use it. Where is that ?
Thank you .
When i was talking to the Engravers Network guy that I’m getting the 150-watt ULS from about cutting capabilities, he said on things like thick acrylic it’s all about the exhaust.
Lots of things go into it, but pressure is a big one. It might be a 400 CFM fan, but that’s probably at 0.00” static pressure. The further the run is, the more turns and angle of turns, the type of tubing etc all add resistance thus decreasing pressure and decreasing airflow, usually drastically. The closer you can get the fan to the exhaust port, the less fan you’ll need overall. Putting it at the end of the run will hide exhaust leaks by keeping it under negative pressure but you’ll need more fan.
A 4” duct is capable of flowing nearly 400 CFM before it maxes out. Using reducers to go into the fan isn’t an issue. Pretty sure Boyle’s law comes into play here also at some point.
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i have a pretty short run, thankfully. and two 90 degree turns.
My 6" fan is 25’ away from the machine, back in the hallway near the window it vents from.
Alexa kindly turns it on and off for me… 
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Mine is pretty short too (only about 4 feet). So maybe the 4 inch fan will work.
well, i’m not sure i think the 4" fan is completely successful, and my run is 46" with 3 (not two, as i said earlier) 90 degree turns.
So, should I not bother with the 4" fan? I have 43" run with two turns. Should I just go straight to the 6" and find some adapters?
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Total effective length. I forget exactly, but a 90 degree bend adds like 30’ of effective length. Compressed flex hosing makes a big difference as well when uncompressed (loses a ton of flow).
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30 feet? or 30 inches?
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You just go to the Gloforge interface and click the dropdown menu with the three vertical dots, and select “Glowforge filter attached” this will disable the internal fan and let you utilize the externally attached fan. Yep, you just add it to the back of the Glowforge. Do a search in the forum for inline fan, or Vivosun. A bunch of folks have posted pics.
Can i still run it out Window or do i need the Filter set up to make it most quiet. you mentioned the 8 inch being the best , Thank you