custom JBL 2206 ewave testing

Many months ago I sent GordonW a trashed JBL 2206 for a custom recone something like the "2236" frankenspeakers he worked up for another member. The goal was to drop the Fs and get more bottom end out of it and make it a budget-friendly high performance ewave woofer.

From WT3 testing...
Fs = 32.3 Hz
Qms = 7.138
Re = 5.5 ohms
Qes = 0.527
Zmax = 80 ohms
Qts = 0.491
Le = 1.83 mH

Graph # 1 - used the high efficiency (>95 dB) ewave HF section. Low pass is also standard ewave L2 = 1.5 mH and C2 = 12 uF. I added zobel (C = 15 uF R = 7.5 ohms) across the woofer for good measure. Not bad, but the woofer rolls off a little early.

Graph # 2 - being lazy, I tried running the woofer naked for full range testing. It looks to me like it rolls off reasonably smoothly. A little tweaking on the HF section and it might be possible to make it work with no LP at all. I don't know if that is a good idea but it is in the econo spirit.

All curves smoothed 1/6 octave, measured at ~40" between woofer and waveguide.

Photos and more details later...

Looks like your are off to a very good start.

Photo...

And here are some notes from GordonW regarding how he put it together. Not sure if the specs below were measured or modeled. My original thoughts were to drop it into an L100 cabinet and pair it with a B&C DE250 on a SEOS 12" waveguide. The L100 cab is too small but I wouldn't want to hang anything larger from the ceiling....these would be used for surrounds

Fs= 37 Hz
Qts= .415
Qes= .436
Qms= 8.786
Vas= 3.93 cubic feet
Re= 5.395
X-max= 9mm
Le= 1mH
SPL= 93dB @1w/wm

As for response- looks like about:

36Hz f3 in a box of 4 cubic feet
32Hz f3 in a box of 5 cubic feet
30Hz f3 in a box of 6 cubic feet

All vented, tuned to about 32 Hz.

That looks to be a better trade-off, than the 2203 or the 2206. Neither of them get below 40 Hz flat, really (very low Qts for the 2203, very high resonance for the 2206). The efficiency is a little lower (93dB for this one), but IMHO, it's still pretty good, for anything that will make bass in a remotely moderate size box (i.e, anything more efficient, the box has to be HUGE for low bass reach).

This is using a longer-winding, copper-wound voice coil, a soft spider, and the original 2206 cone- the 2206 cone gives the flattest midrange frequency response of any of the JBL 12s. It would be easy to integrate into an E-wave, or anything like that. And, with 9mm X-max, it would have NO PROBLEM with bass output either.

Looks to me like the ideal low pass would just knock down the ~4.2kHz noise and let it do its thing below that.

I couldn't tell you how to change the high pass without PCD, but it looks like you could have a VERY flat response. It actually looks a bit like you might be measuring a little off the axis of the primary lobe (vertically, I assume). Invert polarity on the HF and find the deepest null from top-to-bottom, then go back to correct polarity and measure again. If you've already done that, nevermind .

This might well be a killer plan. Being able to NOT use a LP filter, is a great way to cut some cost out of the project. And, not having external components on the woofer? Can you say "cleaner signal path"?

One thing you might want to try, to improve the blend between woofer and horn- try a slightly SMALLER inductor value in the E-wave highpass. Maybe a .5mH instead of .6mH as a start. You want to increase the crossover frequency AND the Q of the crossover. Might require a slightly smaller cap (say, more like 4uf instead of 4.7), and an even smaller inductor (say, .4mH), if that doesn't work.

Or, it might be worth it, to put in a first order lowpass at about 3.5KHz, and a LCR notch filter at 4.2KHz after that. That, maybe also plus the above, might well work well.

Worth some experimentation!

Regards,
Gordon.

I'm working on rigging up my work laptop to do measurements in the garage so I should be able to beat on this some more over the weekend. In the garage I can do testing with the wife at home. I probably should have though to that 2 years ago.

GordonW said:

Or, it might be worth it, to put in a first order lowpass at about 3.5KHz, and a LCR notch filter at 4.2KHz after that. That, maybe also plus the above, might well work well.

Click to expand...

Any suggestions on what component values to start with? I'll eventually get around to PCD modelling but getting pointed in the right direction is appreciated.