Cheap 6" inline duct fan muffler tutorial!

Discussion in 'Do It Yourself' started by SmokinTrichs, Sep 25, 2009.

  1. #1 SmokinTrichs, Sep 25, 2009
    Last edited by a moderator: Oct 1, 2009
    I just typed a huge thing for you about my home made muffler but it got erased and I'm bummed!

    Oh well I'll see what I can muster rewriting. Yes I know I shoulda saved it before I went to preview and screwed things up. I did not do that. My bad!

    This will be my first real contribution to GC since I feel like this thing really works.
    Hope some of you find some of this useful! I know I learned from it and had fun building it too.

    So I've been battling the sound problem a bit with a 6" fan on my indoor setup.
    I'm in the next room and sleep is tough at higher speeds but with the heat of the hps in the summer they are necessary. I'm also in a 2x2x4 tent! haha. Need to keep air moving 24/7, or so I have learned here. I can also no longer use the central AC to externally cool my grow. (Duh!) Lesson #2,456,392,98659dsihtl!

    But I learn quick. So one step at a time!
    Downsize to proper lighting. Picked up a 150w HPS that manual states covers 2x2 space.

    Now to ventilation. The tent has 6" cooling hole on top so I'll take advantage of that. Yes, I need a 6" fan to cool hps in a 2x2 tent in the summer with no AC, sorry to burst your bubble hash! It's 86* in here now at 9:30pm and was hotter earlier. lol

    The creation of the bucket muffler is born on the day I didn't like the price of the currently available duct mufflers. Since I had freshly exited Bubble Bucket 101 from the gracious Rumple sticky with my bucket degree I had a few extra "homers" (buckets from home depot) on hand and the skills to use them. Getting down to business..

    My 6" inline fan mounts to a thick cutting board and sits on carpet for sound dampening. No sound there and I could even set it on foam later no biggie. My setup isn't what we are here to discuss. It's the DIY muffler to dampen the sound from the wind and even some of the motor noise.

    Quick thinking I grabbed a bucket lid and started cutting a hole with a dremel. The hole got bigger and I went with it. I made the hole large enough to "friction slip fit" on the output flange of my 6"inline fan. It is hard to press on, but once it's on there it's solid without any extra parts. Now is were I made it even more solid than that by adding a hose clamp on the flange in front of the lid. Not going anywhere buddy!

    Now that we had a mount for the bucket muffler it was time to experiment with some sound muffling designs. First off I tried simply putting a 6" hole in the bottom of a bucket and attaching to the lid forced and clamped on the fan. A hollow bucket with a hole helped a tiny tiny amount, but I still couldn't sleep at night in the next room! I then got the wild hair to google "how mufflers work". What do you know I'm a genius about mufflers 5 minutes and a wikipedia session later! Turns out you need to defuse the sound and make it take a few corners or even cross cancel it with negative backpressure through a resonator! interesting stuff to say the least and I had some info to work with. I decided to make a diffuser type of design with also a bit of a negative pressure thing going on.

    Went down to Lowes and found a 6" aluminum air conditioning duct adapter that was perfect for the job. Also grabbed a cap for the "diffuser" assembly I could see in my mind.
    You can see the two duct pieces in the picture. One has prongs on one side for installing into ducting assemblies. The first thing you will need to do is pound the 6" duct cap on to the side of the duct adapter without the prongs, leaving those free to use for later.
    Once you have the endcap pounded in place, put a piece of aluminum tape on there to keep it there. Wrap it once over the top of the cap and down the sides of the adapter and then all the way around the cap and adapter ends to seal them off. See the pic!

    Now check to make sure your defuser assembly fits in to the hole in the bottom of the 5 gallon bucket snugly. You don't want this to be a loose shoddy fit. Make sure you take your time when making this hole so the defuser isn't rattling around in the bucket and is a press fit.

    Now comes the tedious part. Drill a bunch of 1/4-3/8" holes around the diameter of the diffuser. The idea is to have enough holes so as not to restrict your airflow by a large margin, if any at all. You can adjust the amount of holes you think you will need as necessary for airflow.

    Once all the holes are drilled you can go ahead and insert the diffuser into the bucket bottom hole from the inside, prongs facing out the bottom of the bucket and bend the prongs over. You will now be deflecting and diffusing air in your bucket! But you can go one step further and line the bucket inner wall with a thin layer of egg crate foam to help even further!

    Does it work?
    Let me just say I can sleep in the next room now with my fan at almost full throttle no problems. I took a nap today just to test after finishing construction. lol. I have also received approval from others. I don't even have my foam insert installed yet but I know it's going to help even more and the sound is already cut in half if not more. It won't reduce all the electric hum from the motor although it does slightly, but it really puts a huge damper on the noise created from the moving air!

    Basically, it works very well!

    Don't forget to try adding foam! You might also add a 6" flange to the back/bottom of the bucket for running your exhaust out. I'm sure you could probably use smaller buckets and smaller flanges for 4" systems like this as well! Give it a shot and let me know what you think! We are positive it's reducing noise on our end and it only cost us homer bucket, some aluminum tape and a trip to lowes for the ducting and hose clamp! My buddy is bringing the foam (not pictured) soon! Should make it work even better. I was surprised how much more I could increase my fan speed! You will be too for what you paid for this device!

    Thanks for checking out my muffler. Don't forget your foam! Let us know how it goes!
    SmokinTrichs :wave:

    Attached Files:

  2. Pretty cool setup on the muffler for the duct fan... I also use a 6" duct fan on the top of my cabinet.. The problem im faced with is if anything upstructs the fan, air flow isnt as good.. Have you had the same problem..? I dont worry about heat since im using CFL's so my fan is only for air exchange and slight cooling..
  3. #3 SmokinTrichs, Sep 25, 2009
    Last edited by a moderator: Sep 25, 2009
    Thanks for coming in to check out my rig.

    I can't say for sure because I have no way to measure the airflow, but my muffler does not "load up" the fan motor. As in, you do not hear a decrease in RPM or notice the fan bog down at all when you put the muffler on. If I am restricting airflow, it's not by enough to make much of a difference I believe. The sound benefit would be worth while to me anyways even so.

    I was told I need less than 100CFM to keep my setup cool during the day but my room temperature is 86* before I even turn my 150w HPS light on. Get over 90* quickly with the hps on. I might have to wait for winter to grow with HPS in this little box :( which means I coulda saved money buying all this in the first place by waiting until it's cold and growing outside. I don't know how I'll work around these temps!

    I'll update you guys when I get the foam in my muffler or if I make any changes. Could only get better!
  4. #4 Herbalonics, Sep 28, 2009
    Last edited by a moderator: Sep 28, 2009
    Jah Bless! I have been thinking about the same thing once I saw they go for $90, and was looking for something exactly like this. I am running a 465 cfm 6" exhaust in the closet of my bedroom! and boy it took a good few weeks to condition myself to sleep through the noise, but I am going to get the stuff for this and build it tomorrow! ill let you know how it goes, thanks for the post!

    EDIT: Question, the diffusion is the same concept as the downstems in bongs, and I hear having lateral, thin slits as opposed to the round shaped holes is better and more efficient for diffusion, do you think this could be the same for this muffler?
  5. I have a 6" 465cfm and I am also gonna try this out...
    do you think I can attach my filter to the output end of the silencer and still get the same affect?.
  6. #6 SmokinTrichs, Sep 29, 2009
    Last edited by a moderator: Sep 29, 2009
    Your guess is as good as mine there. This is the first one I have built so you guys know as much about it as I do. I do know that I am able to sleep better now for sure and I run my fan at much higher speeds. The muffler does work. I found you might want to set the unsupported end on something though to prop it up a bit. I don't even have the foam in my muffler yet. I still need to try that because I know it will help even further.

    At $20 max this bucket will probably help you out more than harm your wallet.

    I would imagine so. Carbon filter? Just find a suitable flange at a "building supply store" and bolt it to the bucket over the diffuser, adding RTF silicon as a sealant or something between bucket and flange and diffuser. As long as it's inside the tent I think it should still work. Make sure you have no air leaks in the rig.. I think that ducting isn't so air tight so wouldn't help much to have a carbon filter outside the tent after the muffler like say in my setup. I'd put the carbon filter inside.

    Also, the bucket lid will flex if you put too much weight on the bucket. You'll want to support it if you add weight to the bucket bottom so it doesn't detach from the bucket lid. As it is without weight the bucket stays attached on it's own at full speed 400 something cfm, but I put a lil container under the end to prop it up so it doesn't "lean". See pic below. Canister under muffler for support.

    if you maximize that picture twice you should be able to see my fan speed control up in the red zone near full power. No complaints. I received complaints prior to the bucket at 1/2 power. lol It's definitely working.

    Attached Files:

  7. I know that most performance auto mufflers use the slits instead of holes. *shrug*
  8. yea I had a feeling about the slits, I am going to experiment some more because i rigged this up, but I couldnt find the exact connector duct piece with the prongs at the end, I found one similar that had end-caps but didn't have as much as a surface area as the example so I dont think i have sufficient airflow, because its not working yet, but needs some tweaks. I also want to experiment with sucking the air in through this rather than push it out, i feel like it would be more effective with ventilation and hopefully have the same effect on the noise of the fan its self
  9. #9 SmokinTrichs, Oct 1, 2009
    Last edited by a moderator: Oct 2, 2009
    Friend gave me a piece of foam for lining the inner wall of my bucket muffler today! I just have to cut it down a bit.

    A performance muffler lets extra exhaust noise out over an OEM muffler.
    We are shooting for a quiet 6" fan "electric vehicle" type sound, not an "old Chevy muscle car with headers and exhaust" type of loud sound.

    Here is the picture of the muffler I got part of the idea from for diffusing the air.
    HowStuffWorks "How Mufflers Work"
    I only had to do 50% of the diffusion of the design in that picture to get noise reduction (one diffuser on one side). I suppose you could do two, one on each side to further reduce the noise.. as shown in the muffler picture.

    Attached Files:

  10. It good to see people being resourceful. I'd rather make it myself than pay more for the same thing........
  11. Nice! I think I am gonna give this a shot with a smaller bucket. I am a newbie to growing, but I have my 2x2 tent setup going and I have a 4" can fan that I would like to make a little quieter. Any improvements with the foam? Also how much did the foam restrict the airflow? :hello:
  12. #12 SmokinTrichs, Oct 21, 2009
    Last edited by a moderator: Oct 21, 2009
    The foam was cut in a manner to not restrict any airflow. It just lines the bucket in a thin layer on the inside so it doesn't have such a hollow sound. It works fine with or without the foam.

    I now set foam under the board I mount my 6" fan to and this helps quiet it down some too.

    I just recently bought a 4" inline as well. It's pretty quiet if you just put ducting on both sides of it and hang it inside your space. I did buy the parts to make a muffler for it though so you will probably see a DIY 4" muffler added here soon. ;)

    I'll get pics of the foam installed in the 6" muffler up later.
    It's 2am right now and I can't hear the 6" or the 4" in the other room..
  13. I had to sleep in a room with a 6" vortex.. My musician buddy told me about the material they use in his studio to muffle to duct for air conditioning in the recording studio. Auralex SheetBlok 4x30 @
    Cut it to size, wrap it around the noisiest equiptment, line a box with it and drop the loud equiptment into it. Works very well. Seal the edges with caulk + duct tape.
  14. Hello, just wanted to say thanks to SmokinTrichs for this great tutorial. I have a 4" CAN fan and I used this tutorial as my guide. I used a 2 gal. paint bucket instead of the 5 gal. and I made a few minor modifications, but the outcome was what I was hoping for and that is less noise. I will post pics soon. Thanks.
  15. #15 Spaceinvaderx, Oct 26, 2009
    Last edited by a moderator: Oct 26, 2009
    Here are the pics... Also, I used the cheapest air conditioning filter at Home Depot, removed it from the cardboard frame (I recommend using working gloves because of little splinters), and just folded it inside my new muffler. I am considering adding a second filter, but it has made a considerable difference already, so I may not mess with it. My next project is trying to figure out a 4 inch ventilation attachment that can fit underneath a door.

    Attached Files:

  16. I was brainstorming tonight :smoking: and thought about your muffler, if you tried incorporating the odor neutralizing cfl's with enough you may be able to completely do without a carbon scrubber.:eek:
  17. Glad to see the idea spreading around :)
    It does help quite a bit on my 6".
    My 4" was fairly quiet once I put some ducting on it and I don't have to sleep in the same room so I lucked out on making another muffler so far. Although I'm sure the idea would work out fine on my 4" too. I'll be getting the carbon scrubber eventually and then probably adding a muffler almost like you did there.
  18. I have my grow set up in my closet so I definitely needed something to muffle the sound and this reduced the noise by about 30-40%, which makes a huge difference. I haven't started my grow yet, just waiting for the seeds, but I've been trying to read as much as I can and get everything I need before I start.
  19. A wise choice. :)
    You might even want to test your whole system for a week or two or three before adding your seeds. I've set myself back quite a few times already on stuff that could have been prevented by testing for a good few weeks. Be patient and the rewards will be great! Nothing goes quick growing herbs. Patience is one lesson I really need work with myself. This is good for me in many more ways than one.
  20. #20 Spaceinvaderx, Oct 28, 2009
    Last edited by a moderator: Oct 28, 2009
    Yeah, I have been researching the growing aspect for about four months now (just finished reading the Cannabis Bible). I have also been purchasing parts little by little, and now I am as ready as I am going to be. I have enjoyed the herb for many years, but this will be my first attempt at growing. I have chronic back pain and knee pain from my military service, so I figured Once my seeds get here I will try to keep a grow journal so that I can be advised on how I am doing. I am a computer geek (that is my hobby), but the more and more I read about growing, the more I like it.

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