Alternate drivers for Jon's "Simple Sub"?

[cdwitmer]

For some reason I had trouble replying to the original post, so I started a new thread.

I am very much intrigued by this "Simple Sub." I had been thinking of a pair of Joe Rasmussen's "Critical Q Sub" units, which are quite nice in that they make life simpler for an inexperienced DIYER than, say, the Linkwitz or Rod Elliott subs that require the construction of special EQ circuitry. However, it seems that one can't get much simpler than this "Simple Sub." I have enough room for two 75 liter enclosures. (I could go a tad larger if necessary.) Now, since I would be purchasing drivers for this from scratch, can anyone tell me which of the following would likely be the best? --

Adire DPL12
TCSounds TC2+
Peerless XLS 830500

I confess that I am much more interested in these subs for listening to organ music than for HT. They would be steeply crossed at 50Hz and I have a pair of 300W/8 ohm monobloc amps (without any built-in EQ functions) to drive them. Eventually I intend to use Digital Room Correction, but I want the subs to be as flat as possible to down to 20Hz in the first place.

Any thoughts on the best driver selection for this would be GREATLY appreciated!

Thanks,

Christopher Witmer
Tokyo

[Dennis H]

Well, I think the whole point of Jon's article was that the DPL12 sub was "simpler" than using otherwise comparable drivers.

[cdwitmer]

Well, the original thread was dealing with the drivers that Jon happened to have on hand, which included the Shiva, BP1203, and the Titanic MkII. The Peerless XLS 830500 and the TCSounds TC2+ were not discussed, if my short-term memory serves me correctly.

[JonMarsh]

What makes the idea with the DPL12 "simple" is that the driver T/S parameters produce a very nice characteristics for a smallish box as regards system Q and Fb, so there's no need to caclulate a port, or box EQ, or whatever, as is usually the case to reasonably "optimize" something more "complex", like BPD203's or the Peerless in the same size box.


You should get close to the same results with the TC2+ I haven't run the numbers for it in a sealed box using Unibox or LspCAD- but since they cost about the same, and have about the same distortion below 100 Hz (the TC2+ has a light edge in performance, the DPL12 tops all other contenders I know of below $200 and below 100 Hz). The TC2+ very smooth and extended in the top, so integration at various crossover frequencies wouldn't be a problem. I can run figures this weekend if you don't have a chance to check yourself.

BTW, why 50 Hz crossover frequency? What area your mains good to? The reason I ask is that for clean integration with "text book" filters, you generally want about 1 octave of clean overlap; that is, your mains shouldn't start rolling off until at least 1/2 octave below the chosen crossover frequency. 60-75 Hz is usually a lot more practical than 50 Hz, unless your mains are good to 30-35Hz already. Just my 0.02.

IIRC, the Peerless are too low in Q; they would be well overdamped, but require some EQ to get the right overall response. I.E., not simple!

Another factor for the DPL12's was that I had four from the original pre-build purchase, so these one's didn't cost me much, either. But I've since sent those all to ThomasW, who's using them in his "Arvo Ultra" (four DPL12's per side). Will their be a Arvo Ultra with TC2+? Well, I don't really have room for thme! :rofl: But they're work well if I did....

Actaully, what I'm debating now is what midwoofer setup to use with my RD50 ribbons- might be 6-8 of a new Dayton 8" woofer coming out the end of September which MarkK previewed, or it might be 4 TC2+, depending on how they test on a dipole panel about 200 Hz.

~Jon

[cdwitmer]

Dear Jon,

Thank you very much for the kind reply and for the offer to run the numbers. I have quite a bit of experience designing and building my own loudspeaker enclosures . . . but the last time I did it was nearly a quarter century ago! And I am not yet comfortable with this newfangled plug-in-the-T/S-parameters approach that you young whippersnapper rocket scientists seem to have such a good grasp of.

Here are the parameters I have been quoted for the TC2+:
Fs: 26.00 Hz
Qe: 0.57
Qm: 4.67
Qts: 0.51
Vas: 63.79 ltr
Sd: 0.0457 m^2
Mmd: 167.08g
Cms: 0.0002 m/N 0.217073 mm/N
Rms: 6.04 Ohm m
Bl: 14.21 N/A
Xmag: 19.3 mm
Xsus: 23.5 mm
Xmax: 19.3 mm
Mag Maximum: 2.8 mm
Sus Minimum: 0.2 mm

As to the crossover frequency, I admit I'm not absolutely confident that 50Hz is where I should be crossing. I'm currently having the fullrange drivers for my main speakers custom built, and the builder and I have still not finalized the characteristics for the low end of the fullrange driver. The -6dB point for those drivers can be set as low as 25 Hz or as high as 35Hz. I have an analog active crossover unit that will give me 6/12/18/24dB slopes at 50/70/90Hz, and I also have a digital crossover (in software) that I can adjust almost infinitely, so I can, to a degree, "force" just about drivers to work . . . although IMO the closer the individual components of the loudspeaker system match each other mechanically prior to adjusting through electronics, the better.

If I didn't have a choice between the TC2+ and DPL12, I would probably use either and be happy, but since I am in passionate pursuit of clean, low-distortion bass in that last octave, I fret over such choices.

I can't wait to share my collection of pipe organ music with all my neighbors after I finish these subs!

[JonMarsh]

Dear Jon,

Thank you very much for the kind reply and for the offer to run the numbers. I have quite a bit of experience designing and building my own loudspeaker enclosures . . . but the last time I did it was nearly a quarter century ago! And I am not yet comfortable with this newfangled plug-in-the-T/S-parameters approach that you young whippersnapper rocket scientists seem to have such a good grasp of.

....I can't wait to share my collection of pipe organ music with all my neighbors after I finish these subs!

:rofl:


I can't remember the last time someone called me a young whippersnapper; it must have been several decades ago, as I'm AARP material these days, though in denial, of course! :lol:


I'm sure your neighbors can't wait, either! :lol: I trust you have at least a few different recordings of Saint Saen's Cminor Organ Symphony? Might as well try them all out!

With luck, I'll get this done at lunchtime on my new laptop- anything to play with it, you know!

Plus, I still have that box to put a driver in, though I don't have any extra TC2+, they're all being used in the dipoles I'm building.




Should have those number's later today.

Best regards,

[cdwitmer]

Boy, those sure look appetizing!

Every time I see those dipoles of yours, my mouth starts watering. I can imagine they must sound wonderful. At what frequency do you cross over to sub?

-- Chris

[JonMarsh]

I'm working with them full range for now, with a simple passive T shelf equalizer to kick in about 8 dB of boost below 75 hz, down to 30 Hz. The EQ circuit can be run full passive, though I'm doing a non-feedback buffer board with power supply to give more flexibility regarding amplifer impedance. The idea is to get them "respectable" down to 35 or so.

My boss Shanghaied me at lunch time yesterday, and one of my colleagues from Austria kept me up working late last night, so hopefully THIS lunchtime I'll get to the sub calc....

[JonMarsh]

TC2+ Sealed

Sorry this has taken so long to get back to...

There's actually a pretty wide range of box size you could use the TC2+ driver with sealed and get good results- and in fact, one of the best ways to use it would be an IB... are you listening Thomas?

In a more conventional sealed box, due to the starting Qts, we can't go for my preferred Q of 0.5. But let's say we shoot for something not much above a Bessel alignment, which has good transient and phase characteristics; then we're looking at boxes in the range of 80-100 liters. 80 liters well stuffed (Thanksgiving is coming up in a few months, you know) would give a box Fb of 38 Hz with a fairly slow roll off; response is down only a skosh over 4 dB at 30 Hz; considering normal room gain, this is a pretty good alignment, as you can expect 4-6 dB of lift below 60-70 Hz. 20 Hz is down an additional 6 dB from the 30 Hz point.

What if we went a little larger with the box? With 100 liters, the Fb stays about the same, as the 30 Hz point, but 20 Hz is only -5 dB from 30 Hz. Realistically, you could get all the added low end it's capable of by staying with the 80 liter box and just using a judicious amount of LF EQ.

What about an ASW-12 clone? The T/S parameters aren't quite what we'd normally look for ported, but if you use a 100 liter box, you can turn this into a lean, mean, earthquake making machine. Tune it to 18 Hz, you'll have a gradual roll-off from 45 Hz to 17 Hz area (~4 dB), which will give a good balance considering room gain (won't be overpowering down low), and maximum output down to 17 Hz will be about 110 db before room gain at Xmax limits... not bad at all from a single twelve. 200W will get you 106 dB. Stereo subs, anyone?

Sealed, the Xmax X Sd determines the achievable results; before room gain, a single TC2+ will hit about 100 dB at 20 Hz with 250 W input at Xmax limits; at 30 Hz, it's 106 dB, but you'll need about 500W to push that out without clipping. That makes the additional 4-6 dB output capability below 30 Hz of the vented design fairly impressive.

Hope this helps.

Regards,

Jon

[cdwitmer]

Thanks a million, Jon!

Boy, there are so many approaches that would all work, I think it is time for me to stop worrying about it and just "cut wood or cut bait." Thanks to you, I think I am now armed with all the information I need to help my main speakers and subs "make beyootiful music together."

I'll report back on how things work out!

Gratefully,

Christopher Witmer
Tokyo

[JonMarsh]

Do keep us informed, Christopher.

And yes, the nice thing about the TC2+ is that you can use it a wide range of ways- not quite just stick it in anly ole box, but pretty close...


Have a great weekend, and make some sawdust soon!


~Jon