Tiny sub based on Tang Band W5-1138SMF sub and Dayton DSA270-PR

[Jared]

I was wondering if anyone knew of existing projects with the Tang Band mini subwoofer and a larger passive radiator?
I am looking for packaging ideas. With a 10" passive radiator, an 11" cube seems to be the best option, however that ends up bigger than the ~9 liter target. Anyone have any other form factors work well with similar small sub and single larger passive?

reference links:

PR:
Dayton Audio DSA270-PR 10" Designer Series Aluminum Cone Passive Radiator
sub:
Tang Band W5-1138SMF 5-1/4" Paper Cone Subwoofer Speaker

 

[MartyMG]

Hi, I thought the 8" Dayton passive is fine for the Tang Band W5 sub? It could squeeze in a 9-10" cube if that's the form you're aiming for. Dayton themselves use that combination of drivers in their new boombox. Executive 200 Watt Portable Bluetooth Speaker Kit
It looks to have around 9 litres sub volume. I have those drivers myself and I'm planning a portable 2.1 using ND91's and mini amt's.
Martin.

 

[Jared]

Thanks MartyMG, I did some rough math with the commonly read guideline of double the volume for a PR as the sub itself.
For the sub:
94cm2 * .925cm
~87cm3 swept volume
For the 8" PR:
211cm2 * 1.1cm
~232cm3 swept volume
For the 10" PR:
353cm3 * 1.1cm
~388cm3 swept volume

So I must have gone wrong somewhere, clearly you are right and the 8" is more than double. I already jumped the gun and bought the 10" though. Otherwise, a 9" cube would have been great.

I guess I am leaning towards an 11x11x7ish with the woofer on the 11x7 face to avoid buying another PR.

 

[MartyMG]

Hi Jared, why not keep the 10" PR for another project? I've got one of these as well which I plan to pair with the W6 1139 I have as the project after next!! It might be a bit heavy to be portable though.
Martin.

 

[TBTL]

You could build a bandpass with them and use the PR instead of a port, like the Logitech Z-3e and Z-4 or Overdrive sub. I have tried that concept and it works. Looks good too, as you can make a cube of which one side is completely taken by a large cone. You can either make a fourth order bandpass or a series tuned sixth order bandpass.

 

[wolf_teeth]

I built a sub called Triumph with 2x 830880 as well as Biumph with a single SD215PR; both utilizing the W5-1138.

The problem with the 1139 or 1138 in a 4th order PR-bandpass, is that they aren't sealed-box woofers, and require the vented box on the bottom to get the extension required. They really can't handle the boost like used in Overdrive10 due to the size of the driver and limited Xmax/Sd ratio.

Thanks for the mention, TBTL! I love my Overdrive10! Can I ask what your implementation was if not too large a hijack?

Later,
Wolf

 

[TBTL]

It was a 4th order bandpass utilizing the W5-1138sm and SD215PR. Attached is the WinISD simulation. I see I even designed the box such that it reduces the already low sensitivity of the W5-1138. Good point about the W5-1138 requiring a vented box. I listen at a low SPL and did not boost the bottom end, so for me it was OK.

 

[wolf_teeth]

Wow- that is tiny, and insensitive! You got your low-end by allowing the sensitivity to go down in the design. There is such a delicate balance in bandpass designs to where you normally lose sensitivity to get any kind of low bass from them, or you have a limited bandwidth. It takes just the right driver to overcome these limitations with a small Vas and high Xmax, which typically means a more powerful amp and possibly boost is required. When I design a bandpass, one of my goals is to not reduce the sensitivity of the system as a whole. With the above criteria in tow, this severely limits the possible drivers that apply to this type of design. It just so happens the UM10 and it's larger siblings are quite applicable to this type of design. The UM8 was not large/durable enough to handle the duress these systems can require.

I'm glad to see you built a PRBP4, and that you really like it as well! The 'get out of the way' factor is a nice result for blending and room node considerations.

Later,
Wolf

 

[Jared]

So I have this so far in hornresp.
Anything obvious I overlooked? I went a tiny bit past xmax on both the PR and the sub for this 40w plot as I will be using a tpa3116 modded to mono operation but running off of an inadequate power supply ( a 45 watt laptop power supply) so I expect less than 40w total available power.

I am surprisingly able to max out the 10" PR so not sure how this design would have fared with only the 8...

 

[Jared]

I turned a 130g weight on the lathe today, glued the front panel on, mounted the PR, driver, and terminal and did some low volume listening. I screwed up a seam so it was leaking air.. grrrr.... gotta redo a bit.. not sure if I might just patch the leak and send it lol.

 

[Jared]

fixed seam. Ran it a bit until some magic smoke made an appearance in a tpa3116 board I modified for mono operation. This thing is AWESOME. and to think, it is 2x bigger than it could have been if I did not need the depth to fit the sub on the side. I think I might have to buy (3) 6" passives if the math vs the mass works out to try and balance it a bit. It jumps all over the place, I have to stand on it to hold it still, and then it is not incredibly loud, but it gets way lower than any sub this tiny has any right to go.

 

[Jared]

This has never sounded right. Dropped off like a rock at 50 hz. Turns out I used the specs from the wrong PR when I modeled it... grrrr . I used a 10" PR but modeled with the 8" PR specs somehow. Time to redo the box, and probably turn a new weight for the PR. Is it safe to have a passive radiator with a weight facing downwards? I would expect it to sag over time? I see very few downward firing commerial products, is that my sign?

 

[TBTL]

Indeed, passive radiators do sag when mounted facing downwards.

It jumps all over the place, I have to stand on it to hold it still, and then it is not incredibly loud, but it gets way lower than any sub this tiny has any right to go.

 

[MartyMG]

Indeed, passive radiators do sag when mounted facing downwards.

Hi, I was planning to use a downward facing Dayton 215 passive/ W5 in a portable speaker. If the enclosure was large enough that the PR didn't require any weight added, would that avoid the sag problem?
Cheers
Martin

 

[Jared]

What does that model look like? Going all the way out to 50 liters on the w5 and dsa270 and no mass hits xmax limits for both the PR and the sub around 40 hz. It also leaves a narrow 6db peak at 40 hz. Were you getting similar with the 8" PR ? Plan to handle it with a lot of DSP ?

 

[Jared]

Bumped the weight to 300g, been listening while working from home for the corona. I will measure soon, but it seems like the 50hz drone is totally gone, and that it goes a bit lower frequency wise.

 

[MartyMG]

Hi Jared. There's been no progress on my project but with Covid lock down here, I'm thinking of getting my table saw out of the shed. I can't model PR's as I don't have a Windows device. I use an Android box modeler but of course, it doesn't do PR's. I just research others efforts and make dodgy deductions. The Parts Express boombox employs the DS 215 with 5 1.5 x. 25 inch washers. I was planning to copy that. Glad your's is sounding better!

 

[MartyMG]

Finally got my project going and finished after a month. Tang Band W5 1138 with an SB Acoustics SB15SFCR-00 5'' x 8'' Passive Radiator. The racetrack shape allowed for a low profile enclosure rather than a briefcase style. I tuned the passive using 1hz step test tones to approx 36hz in around 9.7 litres with 40g weight added. Tang Band W4 9374Sf for the mid high sound great in .5 litres sealed. The TPA 3116 2.1 amp provides great power and flexibility with the 24v lithium battery. Its run for over 20 hours! Total cost around £240.

 

[TBTL]

Looking great!

 

[Jared]

Looks good. How did you do the knobs for the tpa3116d2 board?