Wavecor Subwoofer

[kvardas]

Hello, thinking of building a subwoofer that uses either the Wavecor SW275BD or SW312WA driver. Anyone developed a subwoofer based on these drivers?

[JonMarsh]

The SW275BD01 has a pretty monster Xmax; PE doesn't carry them anymore (don't know if that is a corporate choice or an availability issue); Solen has 4 in stock. Not inexpensive, to say the least... well over $500 USD. Fs about 30Hz, higher than I would expect.

There is a test review on AudioXpress, if that's of interest:

https://audioxpress.com/article/test...udio-subwoofer


There are two each of the SW312WA03 and WA04 in stock at Solen, about 11 mm Xmax, and has a couple of Faraday rings. PE doesn't have them; they were clearance items last time they were in stock.

Nice cone design, very stiff with a primary breakup mode at about 2kHz. Qts is also in the range that almost makes them dipole drivers; you could possibly use them with a PR, but to keep the peaking down, would need a large box. Fs is about 29Hz, OK for music, but HT sub?

What's your target? A sub only in a small box? Not above 100Hz? Music or HT? PR's possible?

In the price range you're talking about here, I'd give strong consideration to the CSS SDX12. It's an XBL design, low distortion at long throws, Fs of 21.3 Hz, and good specs overall. I'd likely use it with 2 12" PR, to get the maximum output down low- with a Qts of 0.37, that shouldn't be a problem. Distortion should be very low even up to a few hundred Hz, due to the triple shorting rings to reduce Le variance. It's like the big brother to the SDX10, which is a driver I have on hand for a planned project.

[kvardas]

Thank you Jon. The subwoofer will be used strictly for music listening. I want to experiment with a subwoofer to go with my wavecor ardent speakers that you designed, and which enjoy listening to immensely.I find the low end to be sufficient for my tastes.

Creative Sound Solutions sells a kit the contains CSS SDX12 driver, PR, and a precut box - they post the dimensions of the box.

[JonMarsh]

That makes things pretty straight forward- would be interesting to plug the specs into Unibox and see how it models- just need to find a bit of spare time!

[JonMarsh]

Let's take a bit more detailed look at this...

I'm going to have to make a substitution, though, as CSS provides very limited data on their PR, though I expect it's been designed fairly specifically for this application. Some of the best PR data sheets I've ever worked with are the Dayton Audio sheets for the RSS series, such as the RSS265PR, and the RSS315PR. Besides the basic table for Fs, Qms, Mms, Cms, Sd, Vd, Max, and Xmax (with zero added weight), they provide the a table for each of the added disk mass steps with the Mmpr, Fpr, and Qmpr. Unibox does a good job supporting parameter changes with added mass, but you can check against the data sheet values, too.

Since I have all of that as used in some different designs for Unibox already, I setup a model with the SDX12 and two RSS315PR.


Here's the 1W data which I check out first against the data sheet.





Here's the fuil SPL plot at 1W.




Though it's a 4 ohm setup, you wouldn't call this a high sensitive design, of course- it's been optimized to go quite deep in a relatively compact enclosure, and as well see, is capable of putting out a lot of SPL without approaching it's excursion limits.

[JonMarsh]

This alignment is with the maximum number of disks you can use with the RSS315PR, at 750g. The APR12 can be mass loaded up to 1200G, tuning it very low- but this would be an unusual way to go, setting an Fb below the range of most program material and limiting PR output.

So, I targeted getting 110dB output, like the SMJ-40 design concept in progress. This ends up requiring 400W- and still leaves headroom for more power an excursion. This is a brute of a 12" driver, and for a single sub setup, will deliver a lot of SPL.








Checking the SPL Plot....






Here's how the excursion looks:






And a very "classic" impedance curve...

[JonMarsh]

So as long as you can bring some watts to the party, you're in great shape with this design, and likely the full kit from CSS Audio.


I mentioned the SMJ-40 concept design, as comparing these two really is a case study for Hoffman's Iron law... enclosure volume versus extension and SPL and power requirements. The design with the SDX12 modeled above uses the same cabinet volume as their kit. The SMJ-40 uses about double that cabinet volume- and takes half the power to reach the same SPL level.

Both are 4 ohm systems.

[kvardas]

Thank you Jon! So impressed with your speaker builder design and building talent and prowess.

[JonMarsh]

Dang, I think I'm blushing!


One other comment about this in the concept stage, for other possible builders too, if bucks are tight- one could build an approximation of this with a slightly less expensive woofer, the Dayton RSS315HE22. it would not have the XBL motor system, but it does have better inductance control than the other long throw Dayton woofers. OTOH, considering the overall cost of the build, saving $150 might be penny wise and pound foolish. It depends on the needs of the target audience. I am a fan of XBL2 motors done right. And the CSS SDX12 seems to be very "right".


But for some, the Dayton might be worth checking out. I'll do an analysis later today.

[JonMarsh]

So, here's the lowdown on a similar configuration with the Dayton RSS315HE-22- or at least, a couple of possibilities with it.

It's important to keep in mind there are a number of areas where the parameter set is different, in ways that directly translate into differences in capabilities. I'll start off sharing doing something pretty close to a straight across comparison at 1W, in the same size enclosure.





The PR mass loading was adjusted a bit, to keep the tuning fairly flat, and in this case, it has to be what is called an EBS alignment, as we're tuning below the free air Fs of the driver.

But notice something interesting- the net sensitivity for 1W is a bit higher higher than the SDS12, in spite of the actual working impedance being higher. And it seemed to me that it might be worth looking for an alignment more optimized for the driver characteristics, which suggested to me a different box volume.

That resulted in this design, with the volume reduced from 63L to 45L.






Lets look at the SPL plot for this closely...






We're not giving up much with this alignment, and we still have nice reposes to below the driver free air Fs with a 25% smaller enclosure.



What's it take to get some "juicy" output levels, and how hard are the drivers working? Let's go for about 110 dB again...






This alignment has a slight slow roll off, so the half plane output isn't a full 110 dB down low, but even a small amount of boundary reinforcement will raise that substantially.



What about excursion?





Here we see an interesting situation, that highlights the issues around design with either ports or PR's. With a PR tuned higher up, targeting "just" 30Hz on the low end, the difference in output of the PR versus frequency reduces the needed woofer excursion in the 30-40Hz area. So, for the RSS315HE22, in this alignment, the max excursion models at about 8mm, whereas the alignment tuned low and delivering well below 30Hz for the SDX12 is pushing 12mm Xmax. Now, both those numbers are well under the driver limitations, and both will probably impress with almost any music program material.

But if budget and space are a bit more limited, the RSS315HE-22 is interesting, though of course the SDX12 can be tuned similarly. Just dropping the enclosure size to 45L gets one part of the way there, while still having an F3 of 26Hz. Dropping the PR mass down to the same level results in slight peaking of the response at 35Hz, and almost drops the excursion to 10mm.

All in all, though, I'd say keep the 62-63L enclosure size with the SDX12, make the room for it, and just enjoy the ride!

[kvardas]

Thank you! I’m gonna go with a 62L enclosure and the SDX12 and two PRs. Again. Thank you.

[Evil Twin]

That should be a most satisfactory solution for your system...