JBL 2231 Reproductions.

JBL studio monitors are hugely successful and rightfully famous for the exceptional output ability and low distortion. The larger models in JBL's last generation of alnico driven monitors were based on the wonderful JBL 2231A 380mm (15") low frequency driver. It provided the clean, clear fundamentals, and smooth, articulate lower midrange that made them famous. The 2231 was used in JBL's 4331, 4333, 4343 and 4350 studio monitors.

Vancouver Audio Speaker Clinic offers reproductions of the classic JBL 2231A, built into reclaimed JBL frames, using original JBL 13lb Alnico-V magnet structures. We use new production air-dried pulp cones with 12 'ribs' and charcoal polyester foam roll edges. Our cones are darker grey than the original #50320 cone, to ensure that our reproductions are not sold as 'originals' or considered counterfeits. We have also carefully reproduced the JBL polyester-cotton spiders. Our 8-ohm voice coil has a factory specified 6.4-ohm DC resistance and a 19mm long edgewound copper winding on a polyimide bobbin. All our parts, including silver-plated Cd-Cu lead wires are engineered to provide the highest possible fidelity and longest life.

In order to reproduce these drivers, we use JBL alnico drivers, from which the 'soft parts' have been removed. A thorough cleaning removes the old adhesives, and the magnets are recharged to their original 12,000 Gauss factory spec. We hand assemble each 2231A cone kit using factory assembly aids to ensure original tolerances are maintained. Donor chassis and magnets come from JBL D130, D130H, D140, K130, K140, 136A, 2205A/B, 2220A/B/C, 2230A and 2231A drivers, selected for good condition. We normally upgrade the small spring terminals to red and black 5-way binding posts, to accommodate modern speaker wire, maintaining JBL's reverse-polarity convention. We also repaint the chassis to black, and (on request) the front rim can be left unsanded to reduce visibility in behind-the-screen cinema systems.

The performance of our reproduction is remarkably close to the original, varying minimally from 40Hz to 800Hz. Selecting the appropriate enclosure size is simple. For most domestic systems, we recommend a compact 100 litre (3.55 cubic foot) enclosure, tuned with a pair of 100mm (4") diameter port tubes. Clean, solid, wonderfully musical bass response is achieved with a pair of tubes 360mm (14.25") long, tuning the system to 31Hz. The ports may need to include 90-degree bends to fit them into the enclosure. This system has a baseline sensitivity of 93dB, with smooth low frequencies down to 39Hz, with a useful lower limit (-10dB) of 27Hz.

In applications where enclosure size is not limited by domestic harmony concerns, a 140 litre (5 cubic foot) enclosure, tuned to 31Hz, extends the deep bass output to 33Hz, and moves the -10dB lower limit frequency down to 25Hz. This exceptional performance is achieved with two 100mm (4") diameter port tubes, 230mm (9") long, and provides musically accurate bass and stunning output levels.

SPECIAL NOTE: 6th May 2010,/P>

We have temporarily suspended production of 2231A reproductions, as we have exhausted all available stocks of JBL chassis in the local market. Until further notice, 2231A customers must locate and supply 'donor' chassis. Our price will be reduced to reflect this. Please call for updated info.