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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.