Cardboard 10" DOS sub project

[ppataki]

This post is related to my moving to a new house/apartment post that I created earlier today

I have mentioned in there that I am changing the subwoofer concept for my new living room - I am moving away from using two mono subs (this and this) to having two identical subs in stereo
I had experimented with this concept before and I came to the conclusion that with stereo subs the 'immersion' or the 'envelopment' is much better
Planned room placement can be found in the link at the top of this post

So the task at hand:
- build two subs
- I want DOS concept so there is no vibration
- I want cylinder shaped cabinets to match my front speaker cylinder design

After many simulations I ended up choosing the SB29SWNRX-S75-6 sub drivers (4 pieces in total)
Those will need a cylinder cabinet with a diameter of 30cm which would be tricky to print with my 3D printer so a pretty unorthodox alternative solution came to my mind: in an earlier post, @RickS shared building a sub using cardboard cylinders (sorry, I cannot find the original post)

I managed to find those in my country too (for peanuts):

So I will put two SB subs into one of these and create two subs like that

I will 3D print some adapter rings that will help fit the speakers into the cylinder (with flush mounting):

Dimensions will be 30 x 50 cm:

Two of these will give me an SPL of 105dB at 20Hz at 1 meter
(99 + 6 for stereo, driving it with 2x400W)

I will use 4mm butyl sheets, 10mm acoustic felt sheets and polyfill filling for the cardboard cylinders

Project will start in July, stay tuned!

 

[Timcognito]

You might learn something here on this thread and our mod @RickS can be a very helpful expert and poster

Easy, inexpensive cabinet for 12 inch subwoofer

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...

www.audiosciencereview.com

 

[ppataki]

You might learn something here on this thread and our mod @RickS can be a very helpful expert and poster

Easy, inexpensive cabinet for 12 inch subwoofer

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...

www.audiosciencereview.com

Thanks, that is exactly the original post that got me inspired

 

[Timcognito]

Thanks, that is exactly the original post that got me inspired

Sorry I read your post but somehow did not look at who it was as you are a quite competent designer yourself and not a newbie. I have enjoyed your content.

 

[ppataki]

The subs have just arrived!

I will do a quick quality check for all four of them tonight

The 'cabinet' shall arrive next week
Stay tuned!

 

[LTig]

The concept to use hard paper is not new - in Germany the company Audioplay sold speakers named Charlie in the 1980s:

CharlyXL

hifimuseum.de - Sie sind im Bereich : Die Charly-Produkte (1984)

Around the same time Jürgen Leppert (a somewhat weird engineer) sold similar speakers made of hard paper. He claimed that Audioplay had stolen his invention. From the ad which sells this speaker:

At the beginning, there were tube loudspeakers made of wood. But Jürgen Leppert recognized early on that significantly better acoustic performance could be achieved with hard paper. This unusual material dampens unwanted resonances more effectively than conventional materials such as MDF or multiplex, while also reducing weight. The result: a lightweight, low-resonance loudspeaker with outstanding sound quality.

I have no clue though whether this is true.

 

[Flaesh]

Just for fun:

Swan Song Audio at Axpona

 

[EngineerNate]

SVS sells, or used to sell, “sonotube” subs commercially and they are very popular in the diy community.

 

[ppataki]

Happy to report that the 'cabinets' have also arrived!

Next step is to 3D print the adapter ring prototype - that will ensure I can fit the sub drivers nicely into the tubes

Hopefully I will be able to do that in the coming days - it will take time since I need to print 3 parts and glue them together to form one ring. And then repeat this 4 times (if the prototype is OK)

EDIT: forgot to add that wall thickness is 3mm, cost was less than 20 EUR altogether

 

[DanielT]

Good luck.

Here is my cardboard casting tube seald subwoofer with dual JBL 12 inch car subwoofer drivers...


.. in downfiring saucer config:

Worked really well.

Important to get good braces, beams, on the sides of the tube to make it stable. However, I happened to glue the drivers together the wrong way so the glue ran. I don't understand how you can be so clumsy. Throwed the tube sub away later. It cost almost nothing and is easy to build so I can easily DIY a new tube sub. Or two maybe two smaller ones.

Luckily I bought the JBL woofers second hand very cheaply so no big loss:


Edit:
I don't think you need to worry about resonances in the cardboard tubes themselves. I think resonances occur a bit higher in frequency than around 80 Hz (if you set that as the cutoff frequency).
Then with, for example, a 24 dB LP filter, it is attenuated by well 24 dB at 160 Hz, 48 dB at the next octave 320 Hz and so on. If there are resonances in those frequencies, you shouldn't hear them. But you can measure and check that.

 

[ppataki]

Good luck.

Here is my cardboard casting tube seald subwoofer with dual JBL 12 inch car subwoofer drivers...
View attachment 527253

.. in downfiring saucer config:
View attachment 527252
Worked really well.

Important to get good braces, beams, on the sides of the tube to make it stable. However, I happened to glue the drivers together the wrong way so the glue ran. I don't understand how you can be so clumsy. Throwed the tube sub away later. It cost almost nothing and is easy to build so I can easily DIY a new tube sub. Or two maybe two smaller ones.

Luckily I bought the JBL woofers second hand very cheaply so no big loss:
View attachment 527255View attachment 527256View attachment 527257

Edit:
I don't think you need to worry about resonances in the cardboard tubes themselves. I think resonances occur a bit higher in frequency than around 80 Hz (if you set that as the cutoff frequency).
Then with, for example, a 24 dB LP filter, it is attenuated by well 24 dB at 160 Hz, 48 dB at the next octave 320 Hz and so on. If there are resonances in those frequencies, you shouldn't hear them. But you can measure and check that.

I agree
Also I guess bracing might not be necessary due to the DOS design and the shape but will see. Inside, I will use a 4mm thick vibrodamping layer and 10mm acoustic felt
If needed, I can add constrained-layer damping (CLD) too but again, not sure if it will be needed

 

[ppataki]

Getting there.....

 

[ppataki]

The above prototype was too small but after fiddling around with the size I have managed to do it correctly

I have actually glued the adapter ring into the tube, let's see tomorrow morning....
Pre-drilling on the adapter ring for the speaker was also done in the meantime

 

[BlueTunes]

What a fantastic thread.

 

[kemmler3D]

The above prototype was too small but after fiddling around with the size I have managed to do it correctly

View attachment 528340View attachment 528341

I have actually glued the adapter ring into the tube, let's see tomorrow morning....
Pre-drilling on the adapter ring for the speaker was also done in the meantime

Pre-drilling a 3D printed part... are these solid infill? I always print with the holes already made, haven't tried drilling a printed part before...

Recently I discovered threaded inserts (Ruthex) that you install by heating them and melting them in place... quite strong and way easier than messing around with nuts on the back.

 

[kemmler3D]

Just for fun:
View attachment 524847
Swan Song Audio at Axpona

I saw these on FB and don't know what to make of them. They're huge for 3D printed cabinets, so you have to respect the commitment, but the facets (to someone who pays attention to 3D printing) suggest incompetence or laziness. And having sharp angles nowhere EXCEPT right next to the drivers, likewise. Just not sure what's going on with these. The website doesn't elucidate the design decisions.

 

[ppataki]

Pre-drilling a 3D printed part... are these solid infill? I always print with the holes already made, haven't tried drilling a printed part before...

Recently I discovered threaded inserts (Ruthex) that you install by heating them and melting them in place... quite strong and way easier than messing around with nuts on the back.

I have always drilled & screwed my 3D printed projects, oldskool but it works like a charm
I use 60% cube infill where I drill

This Ruthex thing seems to be really cool though! Thanks for sharing

 

[ppataki]

Made some pretty good progress today:

The butyl sheet and the acoustic felt were added along with the terminals and the adapter ring on the other end of the tube too

I might add some CLD rings in the center
Tomorrow I will post a knock-knock video

Stay tuned!

 

[ppataki]

Here is the knock-knock test:

New video · Wednesday, Apr 29

Tap to view!

photos.app.goo.gl

To me it sounds pretty good!
For now I am not going ahead with the additional CLD rings

 

[ppataki]

One of the speakers are in!
I have run out of connectors so tomorrow I will buy some more and hopefully will be able to finish the first cabinet (without the painting; that will come later)
I am also waiting for a shipment of polyfill to arrive