LE14A quandary

[Don McRitchie]

I'm not sure of the logic behind that sub choice. JBL has gone out of its way to pioneer lightweight neo drivers for the Vertec line to reduce transport costs for tour sound operators. Sticking a 30lb woofer in their sub goes against that whole approach.

[johnaec]

Are they using "Differential Drive" technology in mobile?

I've got one of the 10" W10GTI differential drive speakers ready to go into a mobile sub cabinet. The magnet assembly is identical for the 10, 12, and 15 inch series. I think part of the reason they're going to very high output speakers is more for the space savings instead of weight, especially when considering extra weight of larger cabinets. Even this little 10" has an Xmax of 17.78 mm!

I wonder if the pro series wires them up the same, with separate leads going to each voice coil, as below:

[Zilch]

From U.S. Patent #5,313,525, May 17, 1994, to Klasco; Michael A. (Berkeley, CA):

"A further alternative enclosure system is the triple chamber bandpass system which utilizes a manifold bass reflex system with the manifold cavity enclosed and ported. The basic configuration is identical to the manifold bass reflex configuration, except that the common cavity is enclosed where the two woofers face each other and a port is added which is tuned to an upper frequency. Two tunings are utilized, one at the low frequency limit of the intended bandpass range (within the outer subenclosures), and the other in a center chamber and tuned to the high frequency limit (below a few hundred Hz). There are two frequency ranges over which enclosure tunings help to reduce distortion by minimizing cone motion. All acoustical output from the system is by way of its port openings, which act effectively as acoustical low-pass filters and further reduce distortion. Dual transducers are employed in a push-push arrangement which reduces mechanical stresses and minimizes third harmonic distortion through cancellation of non-linearities."

References:

Audio Engineering Society Preprint, "A Compound Loading Loudspeaker System: Simulation and Acoustic Characteristics in A Low Frequency Range", Noboru Kyouno, Nov. 1988.
Adamson B218F, 1989.
JBL Introduces SB-1 and SB-5 Control Series Sub-Bass Systems With Triple Chamber Bandpass, 1990.
Acustica, vol. 39, "Loudspeaker Enclosure To Simulate An Infinite Baffle", A. D. Broadhurst, pp. 316-322, 1978.
Speaker Builder, "Constructing a Sontek Subwoofer", Phil Todd, pp. 20-25, Feb. 1985.
Bose Professional Wave Systems, 1987.
Acoustic Research STC 660 Subwoofer Satellite System, 1988.
EAW 1988 New Product KF600, 1988.
Renkus-Heinz Model Sub-152, 1988.
JBL 4688 Sub-Bass System, Mar. 1990.
JBL 4688, 4688-4 TCB Subwoofer System, Aug. 1990.
SR2 System Subwoofer, undated.
Bose 302 Tandem-Tuned Bass System, undated.
ADC Soundshaper 3025 3-Piece Speaker System, undated.
JBL Technical Notes, vol. 1, No. 19, "Sub-Bass Systems Using Triple Chamber Bandpass (TCB) Technology", undated

Anybody have the referenced JBL Tecnical note Vol. 1, No. 19?

[Zilch]

Here's what I was thinking of when I alluded to JBL having a current bandpass product with center slot port similar to the proposed designs:

http://www.jblpro.com/mpro/PDF/MP255S.pdf

The Bose patent has expired, so "dual-tuned bandpass" enclosures are apparently again fair game. There are similar designs from other manufacturers.

This one's wired in mono "Pull-Pull" configuration, the back side of the woofers facing out. The rear chamber has no apparent ports:

http://www.jblproservice.com/pdf/MPr...ies/MP255S.pdf

Installation of the front covers creates the front chamber with center slot port, looks like. Adroitly configured, this....

[loach71]

A very similar enclosure was designed by Steve Deckert at Decware.
It is called the Housewrecker.

http://www.decware.com