Easy, inexpensive cabinet for 12 inch subwoofer

[RickS]

Since my Dayton RSS315HF was just slightly too big for the cabinet I had intended, that cabinet got a couple of RS225s. This was done as a bass module for Directiva r2, but for the listening test, I used it as a subwoofer. I already had one of the RSS315s in sealed rectangular cabinet but wanted to try it out as a bass reflex design. The f3 is about 10 Hz lower than the dual RS225s, so I wanted to hear what difference that 10 Hz makes with my music.

Have enough MDF for a box but it is messy and wanted a quick cabinet for the subwoofer. I have contemplated a cylindrical subwoofer in past, but was unable to find a big enough one. However, there is a newer Menard’s nearby and they stock a 16 inch by 4 ft long tube for a mere $25! I did some quick Bassbox modeling and came up with couple of different volumes. The smaller one required a 20 inch tube length and so I cut the tube down to size…



For the ends, had planned to cut MDF circles, but decided 18 inch square ends were easier and more versatile. The RSS315 can be used as a down-firing woofer but did not like a port out the top and so the squares were better suited for horizontal use. If I do the bigger tube, may try a vertical approach later.

I routed 16 inch grooves in the ends and an offset hole for the driver and did a dry fit and now have this…



I did this over the course of a busy weekend between other tasks/events and am very pleased with the results. The tube is only 1/8 thick but very sturdy once the end caps are on. If I find it needs more support can always add some sides or a bottom panel. Next is some mounting holes and will start gluing it together.

 

[JohnnyNG]

Ahh, yes, good ol' Sonosub! Gotta love the physics of a cylinder.

 

[Timcognito]

Idea: Buy a second tube, saw cut end to end, slide it over and glue it to the first for more rigidity. It might take the next size up and a bigger pie cut.
Edit or on the inside as @OldHvyMec says. Great minds think alike.

 

[OldHvyMec]

Take the tube that is left over, cut one to length (16") and what is left over and split the pair down the side. Cut 1/2-1" the length of the shorter inner tube and glue it inside.

Split the outer tube that is 16" and slide it over the original sonotube. Add silicone or glue. 1/4 X 3 = 3/4" wall thickness. You can add inner bracing pretty easily. 3/4 X 2-4" and then join the left to the right in a couple of places.

Add your speaker post

Stuff it and you have a pretty solid cabinet. A new pillow is 6-8.00 usd and cleaner for those that don't like fiberglass. I'm a course fiberglass guy myself.

Enjoy.

 

[RickS]

Take the tube that is left over, cut one to length (16") and what is left over and split the pair down the side. Cut 1/2-1" the length of the shorter inner tube and glue it inside.

Split the outer tube that is 16" and slide it over the original sonotube. Add silicone or glue. 1/4 X 3 = 3/4" wall thickness. You can add inner bracing pretty easily. 3/4 X 2-4" and then join the left to the right in a couple of places.

Add your speaker post

Stuff it and you have a pretty solid cabinet. A new pillow is 6-8.00 usd and cleaner for those that don't like fiberglass. I'm a course fiberglass guy myself.

Enjoy.

Thanks for sharing your ideas…

Keeping it clean and easy inside initially, am more inclined to brace externally, but this will get a variety of damping. If the tube needs internal damping, will likely use lightweight vinyl sheet to line it. Once I seal the ends, anything I do internally needs to fit through the woofer cutout. Also want to keep internal volume closer to the original sim as I refine tuning.

Once I get past tuning the prototype, some additional external bracing seems in order mainly to reinforce the tube mechanically.

 

[RickS]

…or (with some tall feet) can readily go back to vertical orientation.

 

[rgpit]

Built these years ago out of oak cylinders that are made for drum kits or commercial display furniture. I cut 3/4" discs for the end inserts and veneered them to match. Drivers are SB Acoustic. They really sound fantastic.

 

[RickS]

Idea: Buy a second tube, saw cut end to end, slide it over and glue it to the first for more rigidity. It might take the next size up and a bigger pie cut.
Edit or on the inside as @OldHvyMec says. Great minds think alike.

Thanks, made me contemplate the mechanical design more. The lip of the tube may not get enough support horizontally. Think am going to add support along the inside bottom joint between the baffle and the tube. Or may be just add a strip along the bottom from front to back…

Or both.

 

[RickS]

So, will plan to either use this vertically or will give it a bit of a spine to better support.

Also realized, these tubes would allow me to more readily experiment with a push-pull design that is otherwise much more work to make a nice box to implement.

 

[RickS]

Ran out of glue and so slowed me down, but glued the front on yesterday. After cutting port hole and doing some beveling, glued the back on today. Forgot pics so will have to some after the glue sets. Am using a Liquid Nails Fuze-it adhesive and it takes 24 hours to fully cure. Hope to have it port added and wire.

Hopefully will be ready to test on Monday.

 

[RickS]

So, here are some pics. Since I said easy, here is bit more detail in that regard. This could be made a bit simpler if you fully inset the baffle into the tube. Then you might be able to do without a router and a circle jig. To cut the tube, the popular online approach uses a circular saw. For this, would recommend a fine tooth blade. Since I did not have, I used an oscillating cutter. With steady hand and patience, this cut nicely with negligible waste.

The ends were cut with hand router and a circle jig. Each end gets a 16.25 circular groove about a half inch deep. If you do not want to fill the centering hole, do not drill through. On the front it matters less as the woofer cutout eliminates it. I decided to offset the woofer cutout about an inch about the tube. I did so for 2 reasons. When the subwoofer is horizontal, this gets the driver away from the floor and should keep it from being an easy target for errant shoes or the vacuum cleaner. Secondarily, figured a little asymmetry might help with baffle resonances. The front baffle will likely get doubled after I settle on the the final tuning.

At this point, beveled the back of fhe woofer cutout and the port exit for less turbulence. Using a hole saw, cut a 3.25 inch hole in the back baffle ensuring it was a little more than 3 inches away from the top of the tube. I am initially testing with a couple of different ports lengths. One is the recommended tuning for the box and it us 13 inches and have a shorter one that is 8 inches long.

After lightly sanding the tube ends, was ready for gluing. As mentioned previously, I used Fuze-it adhesive. After applying a generous bead in the groove, I set the tube in the front baffle and a gave a slight twist to ensure it was seated fully. I applied a bit more adhesive along the inner seam to ensure a good seal. About a day later, I repeated the same for the back baffle and used another board to ensure the baffles were aligned and would sit nicely on the floor when horizontal.

Here is a front view pic…



After the adhesive had set, used some clear latex caulk to ensure a good seal on the outside tube seams. Here is pic while the caulk was still drying…

 

[RickS]

Should note, if your target is a sealed subwoofer, this approach is even simpler and only requires about 7-8 inches of tube to get the required volume for the RSS315HF. Might add another few inches of tube if mounting horizontally just for better stability.

 

[RickS]

So, no measurements except for some impedance checks to verify tuning vs sim. Also gives me an idea if I have any major leaks. This one is sealed well and right on target. As for my initial quick subjective feedback, I do miss that extra 10 Hz. Getting an f3 that is around 30 Hz makes a lot of difference for my test tracks (mainly prog rock). Tomorrow will try some of Amir's test tracks and do some more measurements. I need to get my sealed subwoofer to better match the low end of the vented one or else it will be difficult to compare them without being overly influenced by lower bass output from the vented box.

For those who are wondering, the amplification is a bridged Hypex NC502MP with filtering done by minidsp 2x4HD.

Btw, one vented sub is yields nice authoritative bass for me. Will likely be using 2 or more in my final system.

 

[FrantzM]

Hi

Should note, if your target is a sealed subwoofer, this approach is even simpler and only requires about 7-8 inches of tube to get the required volume for the RSS315HF. Might add another few inches of tube if mounting horizontally just for better stability.

@RickS

That is a most interesting idea. I did consider DIY at some point of my Audiophile life. Took me a while to understand that the cost of tools, non existing woodworking skills made such a venture a failure.. from the start., thus commercial subwoofers were , for me, a much better option... I haven't looked back until ...

This idea of using a "sonotube" Horizontally seems to bring DIY , sealed, subwoofers to the realm of the possible... Are there exemples (video?, Links) of such builds you could share with us?

Peace.

P.S.
Just saw the pictures .. Duh..

 

[DanielT]

Up in the right corner. My subwoofer made of cardboard casting tubes. Dual 12 inch JBL bass drivers in saucer configuration, down firing.

Fascinating is that I did not experience resonances from the tubes themselves. However, I had to brace the plates on the top and bottom with side beams, to reduce vibratones. I was able to play loud as hell with that subwoofer. Unfortunately, I then destroyed the drivers by gluing the drivers together , glue that then also flowed out and destroyed them...but before that it was a high SPL fun seald subwoofer.

It was a cheap fun DIY subwoofer project.

Edit:
Two of these JBL bass drivers were in my tube subwoofer. Bought them cheap from a teenager. Actually for car bass but in a sealed box they worked well for home hifi.

 

[RickS]

Hi


@RickS

That is a most interesting idea. I did consider DIY at some point of my Audiophile life. Took me a while to understand that the cost of tools, non existing woodworking skills made such a venture a failure.. from the start., thus commercial subwoofers were , for me, a much better option... I haven't looked back until ...

This idea of using a "sonotube" Horizontally seems to bring DIY , sealed, subwoofers to the realm of the possible... Are there exemples (video?, Links) of such builds you could share with us?

Peace.

P.S.
Just saw the pictures .. Duh..

This one was built as a rapid prototype and, given how simple it is, did not bother with many step by step pics. Plan another build and will more carefully document. I foresee some need for improvement. As @DanielT mentions, expect will need to bolster the end caps (thicker and or better bracing. As I want this one to be easier to move, was more worried about keeping the weight lower. Some better driver mounting hardware than the screws I used initially, are likely needed for better reliability. Ofc, all this tends to add complexity too. So am going to be pragmatic to avoid over-engineering as well.

 

[DanielT]

My suspicion is that cardboard casting tubes for subwoofers can work well as long as you have steep filters that cut off around 80 Hz. The resonances are then pushed up in frequency and are cut off by the steep filter so they are not heard. But then the size of the tube itself probably also plays a role in making it work well. Please note that this is just speculation on my part.

Full-range speakers and cardboard casting tubes are not something I would work with, however. Unless you place two tubes, one larger and one smaller, and fill the space between them with sand. Or it after all cardboard casting tubes so you can fill it with cement , concrete in between if you want. Plus, of course, before that, a baffle must be mounted. Cut the pipes lengthwise and install a baffle, for example so it is another slightly more extensive project than a tube subwoofer.

My tip; @RickS , if you are going to build a downfiring sub, place a lot of heavy weights on top of your subwoofer. It stabilizes it. In my case, it was needed because it was a party playing high volume/SPL subwoofer.

 

[RickS]

Here is a look at the design for the vented subwoofer in Bassbox Pro. I have been using Bassbox for decades for subwoofer sims and used it to help with Directiva evals too. It is pretty comprehensive, but its graphing is not up to more contemporary software. However, for evaluating the bass performance of subwoofers, I prefer it. Here is a look at the key graphs...

 

[RickS]

Here is my first (and so far only) real measurement..

The blue trace is the longer port and green trace is the shorter one. Tbe Bass box one in the previous post if the longer one and it matches well. Is also very clean and free of even slight kinks that would indicate resonance concerns. The 2k Hz one looks to be related to the driver as it shows up in the spec sheet. Not any concern for a speaker design that has little output below 200 Hz.

 

[JohnnyNG]

Here is my first (and so far only) real measurement..

View attachment 469232

The blue trace is the longer port and green trace is the shorter one. Tbe Bass box one in the previous post if the longer one and it matches well. Is also very clean and free of even slight kinks that would indicate resonance concerns. The 2k Hz one looks to be related to the driver as it shows up in the spec sheet. Not any concern for a speaker design that has little output below 200 Hz.

Yeah, I see that 2kHz blip in my sealed dual-RSS315HF-4 box as well.