Taking the Long Way...

[JonMarsh]

Now, as to the topic title, this is an oblique reference to how long the development path is for some of my “What if?” Projects. In this case, a follow up to the promise yesterday to Steve Manning about a design synthesis for the CSS SDX10, a promise I was confident in making, because I figured I’d already done it!

So, a first for me, this topic has a theme song! Steve will tell you this is how 2022 has felt, and for me, it's how everything has felt since 2015...

✅ Unibox SDX10 Design


This is one Doc Brown should be handling, because it's a "Back to the Future" item from early 2020, and a project study inspired by an active speaker that combines both pressure zone loading and a cardioid mid bass to achieve more uniform room response. The SDX10 is obviously involved in the pressure zone LF solution aspect.Key elements are pressure zone woofer loading near the wall, on back of the enclosure, from 100Hz down, and a cardiod mid woofer/midrange running up to 1200-1500 Hz, depending on both on and off axis performance.


The SDX10 likes an enclosure nearly as large as the SDX12- 60L is pretty optimum. Here's what that looks like with 2.83VRMS with two RSS265PR setup with the right mass loading:












I expect this part will work best with it's own plate amp and LF crossover driving from the speaker level input signal. These days there are a lot of candidates to choose from. For initial POC testing, I have a NOS Hypex DS 8.0 like I used way back for the UMAX sub build for Beverly. Wish I could get more of those. Probably a Hypex Fusion FA501 will do. There are some interesting new ones at PE, but they're mostly backordered.

Midwoofer/midrange had a few possibilities, but not anything I was in love with back then. Now I’m thinking “go slow or go Pro!”, with drivers I’ve recently tested from Faital. Currently the part at the top of my list of possibilities is the Faital 8RS250. Of course, PE doesn’t carry that Faital part.

This is the factory data for the 8RS250. Note that ALL of their woofer measurements have a dip like this between 300Hz and 400Hz, I have concluded it is a problem with their test setup, because the parts I have measured to date do not exhibit that dip. This is another part developed for high power line arrays. It certainly looks doable from this for a 1500Hz to 2kHz crossover, but the acid test will be examining the distortion profile and seeing if there is any significant resonance amplification of distortion products from the cone breakup at 1500. And whether it can be suppressed via a notch filter.








Now, just to keep this from getting boring with all these cone drivers, I could let slip that I'm going to be evaluating something a bit more outré for the high frequency range- and no, I won't get offended if you just call it weird!






And what's great is, all I have to buy is the horn/waveguide assembly, as I already have the Beyma TPL150H drivers. A mere pittance extra, literally!



They should be here by the end of the week...


And the directivity control and flattening of response seem to be useful, based on factory data. But you know what they say... In God we Trust, all others we verify!






I'm going to need to do a lot of new measurements soon... but first, finishing some crossover builds!

[theSven]

What does the cabinet look like for this build?

[JonMarsh]

Well, that's still in formulation, as regards the details, but expect around the same height as the Ardent D, similar materials, relatively narrow and deep. It my look like a kissing cousin to the SMJ-40 bass cabinet concept, but shallower. I'm thinking to keep a family resemblance, because I like the materials and esthetics. If I go two piece with this also, the bottom section will have to be on the order of 34-36" tall. But most likely it will be a once piece setup with the mid frequency (125Hz to 1500Hz) and HF on the front, woofer and PRs on the back, possibly PR's on the sides. Mixed feelings about that, as we only need 2, where as for the SMJ-40 (AKA Saint-Saens Planar) it's not feasible to put 4 10" PR's on the back.

This is representative of the general cabinet construction DNA and likely overall outline.





A front panel in two layers of 1-1/4" maple ply; top and bottom also 1-1/4" maple ply; side walls 1" laminated bamboo for outer walls combined wiht 3/4" BB ply for inner walls (yes, I stocked up early this year with the Ukraine war on the horizon- I hate it when I see stuff like this coming from a mile away, but I don't ignore it), and maple ply for the rear wall. Overall cabinet width is 12-1/2 inches and there are several projects planned around that, including some smaller ones, because this matches pretty well with the TTC baffle size. The cabinet shown here is designed for 4x RSS210HF-4 and 4x RSS265PR or 4x Seas SL26R, the new version, for the Saint-Saens "Ultra". Don't ask, if I told you, then I'd have to kill you...

😂

And for the record, this SMJ-40/Saint-Saens was already underway before I heard about the PS Audio FR30; the initial version was supposed to be smaller and use the Epique E180HE-44, until I measured them and figured out that though it has great very low frequency distortion for a 7" "subwoofer", it's kind of lousy in the low midrange- too much motor inductance, too much inductivity modulation related distortion.

BTW, Saint-Saens is because the Cminor organ symphony is my favorite symphony. And is very demanding of a speaker's frequency range and dynamics. This project (unnamed as yet) should be able to do well also- a bit more focus on reducing room interaction, though.

I consider the RSS210HF to be something of an unsung hero in Dayton's so called subwoofer line up- it's another one that straddles the border between subwoofer and woofer very nicely. Very good behavior below 1500Hz. In the SMJ-40/Saint-Saens Planar, it will be crossed at around 400-450. Eazy-Peazy. A 4x array increases the net sensitivity compared with a single driver, in the same way a small line array does. Because that's what it is.

But that's not this project...

[technodanvan]

Mixed feelings about that, as we only need 2, where as for the SMJ-40 (AKA Saint-Saens Planar) it's not feasible to put 4 10" PR's on the back.

Where there's a will there's a way, start truncating those frames!

[JonMarsh]

Where there's a will there's a way, start truncating those frames!

🤣


Only in the CAD work- I have materials on hand for building both! If it weren't for all the other stuff stored in my garage, it would look like I was running small specialty lumber yard!

[theSven]

BTW, Saint-Saens is because the Cminor organ symphony is my favorite symphony. And is very demanding of a speaker's frequency range and dynamics. This project (unnamed as yet) should be able to do well also- a bit more focus on reducing room interaction, though.

OK so this is the build from that youTube video that was posted some months back. I felt some Deja Vu and this clarified it for me. Now as for Saint Seans, I was at Epcot with my son back in 2017 visiting France and heard that song. My dad is a musician and knows all things classical. I asked him and he told me who that was. I purchased the album in iTunes moments after my dad told me. That is a fantastic symphony!

[JonMarsh]

Yes, it definitely is- And way back in my misspent youth as a co-owner of the Boulder Sound Gallery, I had the pleasure of doing a live recording of this Symphony for the Boulder Philharmonic, performing it, with our Ampex ATR100. But this was actually well after it became my favorite symphony. Note, I define “youth: as < 30 years old.

I have about 5 or 6 different versions of it, 3 in my primary networked music SSD’s

[JonMarsh]

OK, it's going to be a bit of time before I can get back to these, but they are on hand now... you know what they say a about a bird in the bush versus one on hand...