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Discussion Starter · #1 ·
So here it goes, my first real contributing/sharing post after being a long time lurker (having recently joined). I’ve been planning to upgrade my subwoofer arrangements for quite some time, I had a Mach 5 Audio MJ-18M in a small sealed box in my last house when I lived away for school, I have since Had all my theater gear in storage and had the urge to upgrade my subwoofer “box” before I find a new place. Cue the research and design which lead me to a SonoSub.

I used WinISD Pro and SonoSub software to model the design to the best of my abilities, contacting Mark from Innovative Sound Technologies (Mach 5 Audio) to get the exact specs since the woofer isn’t in production anymore. I ended up going with a 24” diameter sonotube, capped off to create 300L (~10.6 cft) of internal volume ported with an 8” sonotube tuned to 21 hz in a -3db extended bass shelf.
I have a friend in contracting who got me the 24" sonotube for free, bought a sheet of 5/8" mdf, and bought about 4 square meters of black felt. I had everything else. So in total for the felt and mdf I spent about $70 total on this build.

Enough of the text onto the pictures:
24” sonotube, 8” sonotube, 18” MJ-18m (yes the 18 seems tiny in comparison)

Untitled by eric_duva, on Flickr

5/8” base plate,
1.5” dowels lifting the assembly 5.5 inches, lag bolted in place
1-7/8” thick for the tube/sub mounting

Untitled by eric_duva, on Flickr

Untitled by eric_duva, on Flickr

Top plate/port is 1-1/4” thick with 8” internal diameter port

Untitled by eric_duva, on Flickr
Poly fill on the endcap to remove tube resonance
Untitled by eric_duva, on Flickr


Full assembled (plastic exterior lining removed as I will be applying a black fabric)
Untitled by eric_duva, on Flickr

The port with bluray for size reference (still going to clean the port edges up when I finish off the exterior
Untitled by eric_duva, on Flickr

Overall:
Untitled by eric_duva, on Flickr

I don’t have my equipment set up as I looking for my own place where I will set up my full theater again, so in the meantime I have pulled out a couple speakers and amp to test it out. WOW I am blown away, this sub has a presence that wasn’t even imaginable in the sealed box. It plays the low notes so cleanly it is astounding. For fun I loaded up a 20, 15, and 10 hz sine waves and I could literally feel the room pressurizing! With the 8” port there is zero port noise even when the sub is pushing all that air to produce a 10hz note. Not bad at all considering this cost me $70 to build!


Question for those of you with bottom dwellers (low tuned) subs, do you add a second sub (smaller ported/sealed) for near field for some tighter midbass? I can’t test moving the sub around or how it would act in a theater space I don’t have yet.
 

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Nice work! Very cool build.

I have never seen a Sonotube in person, how thick are the walls? Are they made of cardboard?
 

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Very cool, I considered going Sonotube instead of the Micros I built, but the MFW15 driver sag squashed that idea.
Does that top plate hang over enough to mate up with the material you are putting on it?
 

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Discussion Starter · #4 ·
Nice work! Very cool build.

I have never seen a Sonotube in person, how thick are the walls? Are they made of cardboard?
On the larger tubes the wall thickness is generally from 1/4" to 3/8" on the thinner tubes like the 8" port the walls are typically 1/8" thick

The large tube is plenty strong, and the nature of being a circle means it evenly disperses the pressure across the entire surface area/ internal circumference.

and yes the tubes are made up of a layered cardboard system.


Very cool, I considered going Sonotube instead of the Micros I built, but the MFW15 driver sag squashed that idea.
Does that top plate hang over enough to mate up with the material you are putting on it?
Yeah I made sure that the MJ-18 was able to handle the being mounted inverted and by my sag calculations it was next to zero sag. They say a woofer shouldn't have more then 5% sag (if I remember correct), and the MJ-18 was right around 1%.

Both the top and bottom plate on the tube overhang by 3/32" which will mate up nicely with the felt. I am trying to find if there is something like a 1/2 piece of flexible molding/trim which I can use to mount just inside the end plates to cover the ends of the fabric so they don't get pulled up/down over its life and make a more finished look than just a butt seem.
 

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always nice to see good work done well, :cool:
if you get time, post some graphs
 

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Discussion Starter · #7 ·
Thank you!

What kind of graphs? Like I said this is only temporarily hooked up to tease myself, I have no metering or anything.

I do have this comparison of the EBS and the sealed box it was in. I found it quite fun playing around with the different volumes and tuning to to optimize the literal 'shelf' in the response graph. I would have tuned lower but I was at the point where it meant large jumps in volume to have a level EBS response.

plot1 by eric_duva, on Flickr

btw, this was my first time using a WinISD program, such a great tool to use.
 

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Discussion Starter · #12 ·
Nice work so far. Looking forward to seeing the finished product. Been awhile since I've seen a Sonotube build. Did you investigate lining the walls of the tube with batting (polyfill in sheet form)? I've read good reports on that working well to tame resonances.
Thank you!

I looked into it in my research and most people seem to put it in because it "doesn't hurt anything", "Seen others do it", "had the fill/foam laying around", but I wasn't able to find concrete evidence of it providing any true benefits, the only real resonance is from the back wave bounding off the only flat surface, the end cap. I am astounded by the results as is and am very happy with it!

Love it! but why 21hz? I made 4 of these tuned to 13.5hz and they were monsters.
Thanks!

Main reason being size, still want this to be portable since I'll be moving shortly and had the itch to build it. It only stands about 4.5 feet tall. If I tune it that low, that would involve about another 3-4 cubic feet of volume to keep a nice flat EBS, especially with this large of a port.
 
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