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Potential sub project?
So I am sitting on four of the Scanspeak built Peerless XXLS lookalikes from the Aerial buyout four or five years ago. Nice build quality, good specs for small enclosures. Shorting rings and some venting around voice coil should mean reasonably low distortion here and there.
Now for the fun stuff. I modeled these as a pair (they are 8 ohm) in a sealed enclosure with the 35Hz boost applied from the SPA250. 0.63 cubic feet(!) yields F3 of 32Hz:
Xmax is nowhere near its limits at 250Watts - however 3rd party testing indicates the SPA250 is actually capable of outputting 400W! I modeled based on the 250W figure. Will never see near that under my normal usage, but at 250W we are looking at over 104db between 40 and 63Hz. This is a significant output level, especially if thrown in a corner somewhere.
Excursion at 250W:
SPL:
These would be mounted opposing so bracing is probably not really required. I can crank them out using some PB shelving, and the drawing I made is based on any one panel having a maximum width of 11". Add a nice Duratex finish and we are looking at a serious pair of stealth subs.
I'm thinking these might replace my pair of 12" GRS 240W powered subs in my basement. No idea what I would do with those, however. The amps are worth boxing up and shipping out, but the drivers are not really worth anything outside of potentially selling them to a car audio guy for peanuts. Then disposing of the largish cabinets is always fun. Alternatively I can use them in my upstairs living room or even at my desk as they will not take up much space.
Anyways, should I build these? I can probably crank out the cabinets in a weekend.
Some driver porn:
Comments
I would think you'll like those a lot.
InDIYana Event Website
I'm thinking that as well.
Just build them!!!!!!!
Your dimensions come up to around .665cf. The amp and drivers probably take up a not insignificant chunk of that.
I skimmed through the Q&A and found the amp mounting depth is 3.5" (subtract .75" for enclosure material). With the 8.5x8.5" opening that calculates to ~.115cf lost. Then you've got those big chungus magnets. etc. I'd just figure tuning tolerance get tighter when dealing with small volume enclosures like that.
Even at 0.5 net F3 is still in the 34 range, I'll take it for the small form factor.
3rd party amp dyno testing of the Dayton SPA250 and the Yung 300W plate amps:
Dayton managed 400+ watts dynamic into 4 ohms. Makes that amp a pretty serious bargain imho.
Also means it will have the beans to really make some volume out of these little fellers.
Upsized to ~0.75 internal. Glued up, will machine tomorrow and start seam filling and prep for Duratex. Drivers will probably not be flush mounted. Have not decided. Will need extra meat installed if I do flush them.
The SPA250's are really nice amps. I have been using a pair for several years. I did a comparison with my Dyna ST400 and it held up very well. Could push it up to ~~ 28 ~~ 38 volts rms into 8 ohms before soft clipping started to kick in (that's about 180 watts!). The only problem I had with it over the years was the 35Hz boost switch. I was clicking it on and off one day and accidently got the switch stuck half way between "on" and "off". Caused the amp to shut down completely until I found the problem.
Good to know! I had two of the 240W predecessors that failed on my, but have now been running two of them almost daily for three years now with zero issues.
Yeah, I'll set the boost and be done with it. I really wish the boost was set at 30Hz, but I am not in the mood to go resistor rolling so will make it work.
Some updated models:
Gained some output below 50Hz with larger enclosure:
Note, I did model this based on the 400W dynamic rating of the SPA250. Even considering how much overhead the boost gobbles up, it still gives an impressive overall output. These things should flatout rock corner loaded.
F3 around 32Hz (with a 60Hz low pass applied):
Zero issues with excursion, even fewer issues considering the model is tickling 108db - subtract 20db from that for my normal listening levels and we are barely moving the cone here.
The above models assume a 19Hz high-pass filter which is what I seem to remember Dayton using in the old 240W version. The effect with or without it is negligible. It also assumes the boost is not a peaking high-pass variety, as well. So several assumptions have been made here, but reasonable assumptions. The difference between a simple EQ boost and a peaking high-pass is also minimal. So moral of the story on this particular build is do not sweat the small stuff.
I've heard that Mills resistors really remove the veil from the dynamics but Mundorf Nickel resistors are faster.
I'll church these up just a little bit.
Machine work done, now to decide how much further I take the cabinets. I might do a full seam/end grain fill and a smooth Duratex. I may just rough Duratex them and call it a day. I don't know - see how my mood is here in a bit. Beautiful weather today.
I decided on outriggers, Lowell gifted me a set a few years ago that will be perfect for these.
Decided to do a half decent finish on these. I figure I'll have something like $1000 in to the pair I may as well make them look halfway decent.
My can of Duratex did not survive the last six months so I just ordered some more. Should be here for the weekend, I'll get these done then.
In the meanwhile, the boost switch on one of my amps is a maintained pushbutton, not a slide. No idea what the boost is as the instructions still claim it is a slide switch. Oh well. Off to PE product page.
Luckily I had some white sitting around so will do first two build coats with it.
I guess pushbutton in = boost on. According to some claimed measurements, the boost is actually centered at 28hz, q of 1.6, and 5db. Changes things a bit, but not terribly.
Sanded first coat down and started filling more blems. Will recoat again after putty cures.
Is that automotive spot putty that comes in a tooth paste tube from Autozone, Advanced Auto, O'Reilly's, etc?
Yessir.
Gosh that looks too much like work for me
.
The hardest aspect is knowing when to stop. My dad was a professional body man who did restorations. He set a high standard, and it is very easy to go down a rabbit hole of finish work. So I don't venture.
Besides, in my personal aesthetic, I want my speaks to blend into the background.
Same stuff I used on my super tw waveguide (built by Nate / silverD) from the local car shop. !
I’m curious why you think they’re ScanSpeak built. They have very Peerless XLS/XXLS-like part numbers - 830772 right? The OG XLS’s were made in Denmark, during the d-s-t era. I have 4 of the 830500s (XLS12) so badged.
Regardless, IMO still a world class driver. Literally the only OEM driver I’ve ever seen KEF use was an XLS or XXLS, in their flagship sub at the time.
That is how PE advertised them. Big Aerial buyout.
https://www.parts-express.com/Scanspeak-269-10-Paper-Cone-Subwoofer-8-Ohm-299-729?quantity=1
Ah - just based on the p/n I expect that's an inadvertent error based on the country of origin. Maybe defensible in that Vifa/Peerless/ScanSpeak would've all been dst at the time, and IIRC all made in Denmark at the time except for Vifa's "Logic" line. Regardless, based on pedigree and frankly who they were made for can't imagine they're anything but exceptional woofers.
Change of plans due to me being an idiot. I measured wrong and the enclosure is not wide enough for two drivers. So, I remodeled with a single driver in this enclosure. It obviously sacrifices output, but I actually gain extension. I will have to add a brace or two now, as well. So that all being said...
With the 60Hz lowpass, 20Hz highpass, and boost applied the sub now extends to 27Hz. This is 6Hz lower than the dual driver, so that at least is a win.
Maximum SPL is of course reduced somewhat:
And of course excursion increases, and in this alignment hits the limit at 28Hz give or take:
Now I have to uglify my beautiful enclosures by capping on hole
Like I said, I am an idiot.
I forgot I have a pair of Dayton RS 10" passive radiators... They fit the cutout and everything. So, now I do not have to make my cabinets ugly with a cap on the one hole. I also gain output but sacrifice a few Hz. The rolloff is steeper as well.
Max SPL is back up to the 106db range:
Excursion is at its limits at 22Hz but it otherwise under pretty good control:
Passive radiator is not working overly hard, either:
So whew, saved the day. Many thanks to Tajanes for the passives awhile back.