JBL S106 Aquarius II
1970 - 1973
Introduction
The JBL S106 Aquarius II was the second model in JBL's Aquarius series of non-directional speaker systems. It was more ambitious than the Aquarius I. It used rear-mounted slot-loaded drivers and a more complex diffraction system, aiming for a wide soundfield that didn't depend on where you sat. With a 12-inch woofer, dual midranges and all that dispersion hardware, it was one of the most technically ambitious home speakers of its era, and one of the hardest to produce consistently.
Overview & Specifications
| Specification | Details |
| Type | 3-way, 4-driver bass reflex non-directional floor/bookshelf |
| Woofer | 12" (30cm) 123A cone woofer (rear-mounted) |
| Midrange | Two 5" (12.7cm) LE5 cone midranges (rear-mounted) |
| Tweeter | 2" (5cm) LE20 cone tweeter (front-mounted) |
| Crossover Frequencies | 300 Hz, 1,000 Hz, 5,000 Hz (estimated) |
| Nominal Impedance | 8 Ω |
| Power Handling | 50-75W continuous program |
| Sensitivity | 90 dB/W/m (estimated) |
| Frequency Response | 40 Hz - 20 kHz |
| Dimensions (W×H×D) | Approximately 24" × 36" × 15" (specifics vary) |
| Weight | 55-65 lbs (25-30 kg) |
| Finish | Walnut veneer |
Driver Configuration
The Aquarius II used a driver array built for non-directional dispersion. The 123A woofer was a 12-inch professional-grade driver, rear-mounted in the center of the enclosure. Spacers sat radially around it, with a flat panel attached to create the slot loading that spread bass energy through the room.
The dual LE5 midranges were also rear-mounted, near the top of the enclosure. Each had its own loading plug on the diffraction panel. These 5-inch hard-cone drivers worked through that panel, which limited their response above 5,000 Hz but gave the wide dispersion pattern the Aquarius concept depended on.
The LE20 tweeter was front-mounted and direct-radiating, to give high-frequency localization and keep stereo imaging intact. This 2-inch cone tweeter worked above the diffraction panel's frequency limit.
The slot loading and diffraction system was the core of the Aquarius II. The rear-mounted drivers fired into engineered slots and diffraction panels that produced a dense comb filter. The result was reasonably flat power response at almost any listening position and a room-filling soundfield.
Design & History
The Aquarius II was developed alongside the Aquarius I under Ed May, JBL's head of Product Development. The Aquarius I used front-mounted drivers with elliptical diffraction panels. The Aquarius II went with a more complex rear-mounted design, which Marketing believed would allow greater flexibility in cabinet design and possibly better coupling with room boundaries.
The original Aquarius II prototype was considered a sonic success, with a wide, deep soundstage that stayed consistent across the listening area. Turning it into a production system was extraordinarily difficult. The design was notoriously sensitive to minor production variances in transducer and enclosure tolerances. Those variations could change the sound from expansive and balanced to thin and nasal.
Eventually, drivers had to be hand-picked and matched to extremely tight tolerances, which raised production costs significantly. Add the complex cabinet construction the slot loading system required, and the Aquarius II was expensive to build. That contributed to its short production life.
The Aquarius II was part of JBL's response to a brief vogue for non-directional speakers in the mid-1960s, championed by companies like Harman Kardon and Stewart Hegeman and particularly acclaimed in the New York audiophile market. JBL brought its professional engineering expertise to the concept. The result was the technically ambitious but commercially difficult Aquarius series.
Sound Character
The Aquarius II's sound is best described as "expansive, immersive, and remarkably consistent throughout the listening space." When properly executed, the slot loading and diffraction system makes the soundfield seem to come from the whole room rather than from discrete speaker locations. That suits social listening and rooms with challenging acoustics.
The bass is full and well-extended, with the 12-inch 123A woofer providing substantial low-end authority. The rear slot loading couples effectively with room boundaries, so the bass presence belies the speaker's physical size.
The dual LE5 midranges deliver transparent, natural vocals and instruments with the usual JBL clarity, but with a more diffuse presentation than conventional designs. The midrange seems to float in the soundfield rather than sit on the speaker cabinets.
The LE20 tweeter provides detailed highs and keeps enough localization to preserve stereo imaging. Direct-radiating highs combined with diffused mids and lows give a presentation that is both immersive and coherent.
When everything works (properly matched drivers, intact diffraction systems), the Aquarius II is less about analytical detail and more about musical envelopment. They do well with acoustic music, jazz ensembles and orchestral recordings, where a natural, room-filling presentation is wanted.
Collector's Notes
The Aquarius II is among the rarest and most challenging JBL speakers to find in proper working condition, representing both the pinnacle and the limitations of 1970s non-directional speaker technology.
Finding an Aquarius II with all original components and intact diffraction systems is extremely rare. The 123A woofers generally need foam surround replacement. The LE5 midranges can suffer from hardened suspensions. The diffraction panels and slot loading systems are fragile and often damaged or modified. Cabinets may show wear from age and the complex construction.
The Aquarius II commands premium prices in good condition. Complete, functional pairs are exceptionally rare and can bring $2,000-4,000 or more. Incomplete or modified examples sell for significantly less. With so few around, market pricing is highly variable.
Restoring Aquarius II speakers is a specialist job, and the diffraction and slot loading systems need particular attention. They should never be altered from their original configuration. Driver matching is critical - the design is sensitive to component variations, so replacement drivers must be carefully selected and tested. Crossover restoration should use high-quality components to keep the original voicing.
The Aquarius II needs careful room placement to get its non-directional effect. It typically wants some distance from rear walls so the slot loading can function properly. They work well with moderate-powered amplifiers (50-100 watts) and are particularly engaging with tube amplification. Because they are non-directional, they are less fussy about listener position than conventional speakers.
The JBL S106 Aquarius II stands as a fascinating chapter in audio history—a technically ambitious design that pushed the boundaries of what was possible in home speaker technology, but whose production challenges ultimately limited its commercial success. For collectors seeking not just a speaker but a piece of audio engineering history, the Aquarius II represents both the promise and the perils of innovation in loudspeaker design.
Documentation
Factory Technical Documents
- HiFi Engine - S106 Aquarius II Manual - Factory technical manual
- Harman Technical Sheet (PDF) - Official specifications sheet
Service & Maintenance
- Service Manuals.net - S106 Aquarius II - Service manual with diagrams
- NoDevice - Service Manual - Technical service documentation
Historical Articles
- Audio Heritage - Aquarius Series - Historical profile of the Aquarius line
External Resources
- Lansing Heritage - JBL historical archives
Similar items on eBay
No exact JBL S106 Aquarius II listings are live right now — these searches show current JBL and similar vintage audio gear on eBay:
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.
Related Models
- JBL 075
- JBL 077
- JBL 120Ti
- JBL 124A
- JBL 124H
- Braun AUDIO-1 (1965)
- Braun AUDIO-250 (1965)
- Magnavox Component Systems (1972)
- Acoustic Research AR (1967-1976)
- Acoustic Research 11