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Finally, a bit of "closure" on a number of projects.
Here's the 2245H I commented on, regarding measurements taken after an aftermarket recone kit was installed, with a "PR18" that I built (2245H cone with mass loading, on an old Sunn surplus 18" woofer basket).
Here's a second view. Note that I trimmed down the cone diameter about 1/4" all the way around the perimeter of the cone in the passive radiator, to allow the installation of a much "fatter" surround. This, combined with the deeper-pleated spider, allowed for about 3.8 liters of cone displacement from the PR. Combined with the 2245H itself, that's nearly SIX LITERS of available air displacement! Think this oughtta make a little bass? :D
Here's a close-up of the suspension and the weight tuning mechanism. I duplicated the methodology used on the JBL PR15 and PR300... a bolt-on washer weight arrangement, mounted to a Masonite plug. There are also steel weights glued onto the masonite inside the dustcap, to give a moving mass of about 15.5 ounces before the rear weights are applied. As shown, it's about 18 ounces, total. My calculations show that the optimal weight, in the box my client is building, will be between 16 and 20 ounces, to achieve a 25-20 Hz box resonance tuning, roughly.
OK, Project 2- a very-high-output center channel, to be used with a pair of JBL Perkins horns (4560 cabinets loaded with 2225H, topped with 2382 horns loaded with 2445 drivers, plus non-JBL supertweeters), as mains, and OAP/Peach State W-horns loaded with JBL 2441 18" as subs. Needless to say, it needed SERIOUS efficiency and power handling. The final result measured in at a sensitivity of about 96.5 dB/1w with a power handling of 300+ watts (that's just the woofer). The driver complement is a modified 2022H (mass-loaded with a mass ring) on bass, a 2410 horn driver on a Sammi Sound/Stanford slightly-smaller-scale version of the JBL 2370 horn flare (14" wide instead of 18", to fit the cabinet) and a 2404H tweeter. The cabinet is a highly-modified early-model L-100 cabinet (it was an orphan, no mate, and the drivers out of it are to be used in my S70 Alpha project).
Crossovers on this project were a bit of a challenge- it's actually got a 4th order low-pass on the woofer, combined with second order everywhere else (midrange and tweeter). Crossover points are about 1200 and 11000 Hz. These crossover points resulted in a response that measured, except for one narrow "diffraction dip" at 18KHz of about 5 dB, flat +- 3 dB from 80-28000 Hz, on a composite of measurements!
I'm always impressed with DIY stuff, especially re-engineering transducers. :cheers:
Hopefully, you'll answer a few questions.
re; The 2022h ( with mass ring )
(1) Why the 2022?
- Documents show it has less Xmax than the 2020, leading me to believe its a shorter coil winding.
I guess that's (Xmax) not an issue here .
(2) Does this 2000 series transducer also have the 1/2" deep top-plate ?
(3) How much mass did you add ? ( I'd like to know the new Fs )
(4) Did you get Ts parameters for this hybrid driver ?
(5) Did you consider and then reject foaming the surround to drop the Fs ?
(6) Did the 2022 have a "rising response" so typical in the other deep-gap woofers?
(7) Did a rising response lead to the higher order low-pass ?
regards <>Earl K
:rockon1:
:scoot:
Next, my C36 project. Note these are non-JBL drivers... Goodmans Axiom 301 12" wide-range drivers, EV T35 horn tweeters, EV X36 crossovers. This speaker system is exactly as it would have been, as assembled in 1960, except for reconed woofers and replacement tweeter L-pads. The only tweak it needed, was to reverse the polarity of the tweeter to remove an upper mid harshness. Amazingly good sound- 97 dB sensitivity, very fast, very TIGHT, CONTROLLED if not massive bass output. It goes pretty low- just not LOUD low bass. Very satisfying transient "snap"!
A "Nudie" of the C36. Drivers mounted from the rear of the baffle, just like most systems "in the day". The cabinets are original... a few chips in the veneer, but pretty woodwork, IMHO. Other than re-staining scratches and chipped areas, the cabinets are bone stock as they were in 1959!
2022 info:
The driver was reconed with a softer spider, and about 15 grams of lead ring for mass. The resultant Fs was about 32 Hz, a LOT lower than stock. Basically, it's more like the parameters of a 2204, except the 3" coil. F3 of about 52 Hz in a box tuned to about 42 Hz.
As for X-max- well, the pole piece is 1/4", and the voice coil winding is 3/4... that gives a .25" X-max (6.5mm). Plenty for this app, which won't see the speaker going below 60 Hz.
With the mass ring, and the use of the "sticky" 123A/Altec-style coating on the fabric surround, there was NOT a rising response. In fact, the driver tracked smooth up to 2000 Hz!
I left the fabric surround, to more closely match the "sonic character" of his main drivers, the 2225Hs. Also, the fabric should stand up to more "abuse"... this guy likes it LOUD...
Regards,
Gordon.
Hey Gordon
Nice center!! Geez man lot's of speaker in that box must weigh a ton!! You using the 18's in the HT set-up??
Rob:thmbsup:
Thanks for that. I only know about the 2020 , 2012 and what Robh has told us about his 20(32?). They all have 1/2" deep gap - hence - my question.Quote:
As for X-max- well, the pole piece is 1/4", and the voice coil winding is 3/4... that gives a .25" X-max (6.5mm). Plenty for this app, which won't see the speaker going below 60 Hz.
It's good to know that the deep gap isn't necessarily present on every 2000 series transducer.
Makes sense, without the extra deep-gap, one parameter for creating a rising response has been omitted .Quote:
With the mass ring, and the use of the "sticky" 123A/Altec-style coating on the fabric surround, there was NOT a rising response. In fact, the driver tracked smooth up to 2000 Hz!
Thanks! I really do love hearing about this stuff! :yes: :blah: :yes:
<. Earl K
It's like 60 lbs! :biting:Quote:
Originally posted by Robh3606
Hey Gordon
Nice center!! Geez man lot's of speaker in that box must weigh a ton!! You using the 18's in the HT set-up??
Rob:thmbsup:
Yes, the 2241s in the W-horns are the subs on the HT setup... with the 4560/2382s as left and right front, and a pair of L100s for rears. Capable of like 130 dB! :eek:
He's got a pair of Hafler DH500s, one running the 4560s/2382s, and one on the LFE channel running the W's. A NAD T753 receiver is supplying the signal to the Haflers, and directly running the L100s, and will be running the center when he picks it up and gets it installed. Crossover point will be about 80 Hz...
Regards,
Gordon.
Oh, I forgot... the main reason I wound up with the 4th order lowpass on the woofer, was the time delay differential betweeen the 2410 on the horn and the 2022. The 4th order filter added a bit of extra delay to the woofer, and took it out of the overlap band faster, so it blended much more coherently with the horn mid.
Sometimes you gotta play with the rules a bit. :idea: :readme:
Regards,
Gordon.