JBL K2 S9800 (1997–)

At 110 kg per side, with pure beryllium domes where lesser speakers use fabric, the S9800 was built from summit-level materials.

Overview

The JBL K2 S9800 arrived in 1997 as the flagship of the K2 series. JBL named the line after the second-highest mountain on Earth to signal its "summit-level" ambitions. It was no gentle step along the studio monitor lineage. It cost ¥2,000,000 per pair in Japan and $18,000 - $20,000 per pair in the US, and JBL built it in its Northridge, California factory. It was the first JBL product to use pure beryllium dome tweeters and midranges. Beryllium is still rare in loudspeaker manufacture because it is so difficult to work with.

This is a three-way design with dual 12-inch woofers, a 4-inch pure beryllium dome midrange, and a 1-inch pure beryllium dome tweeter. It is not a four-way, despite what some marketing materials suggested. The configuration is simple on paper. The woofers use Aquaplas-coated pulp cones, a treatment JBL had refined over decades of professional monitor work. The enclosure has curved side panels and internal bracing to keep the cabinet from adding its own voice.

The S9800 was designed as the successor to the original K2 series from the 1980s. Stereophile (1998, p.23) gave it a Class A rating in its "Recommended Components" list. It praised the speaker's "exceptional neutrality and resolution" and called the beryllium dome drivers "a significant technical achievement."

Key Features

Pure Beryllium Dome Tweeter and Midrange: The 050Ti and 100Ti

The headline feature of the S9800 is pure beryllium for both the tweeter and midrange domes. The 1-inch (25mm) 050Ti tweeter and 4-inch (100mm) 100Ti midrange were the first beryllium dome drivers JBL had ever produced, and collectors still talk about them decades later. Beryllium is extraordinarily stiff for its weight - roughly three times stiffer than titanium. That lets the dome move as a rigid piston across a wider frequency range before breakup modes set in. The result is a clean midrange and treble, free of the coloration that plagues softer dome materials.

There is a cost beyond the price tag. Beryllium domes are fragile. Owners report that they dent if touched, and replacement domes are expensive and hard to source, sometimes requiring an order through JBL's Pro parts division at significant cost. The acoustic lens around the tweeter helps with dispersion, but it won't stop an errant finger during setup.

Dual 12-Inch Woofers with Aquaplas-Coated Cones

Low frequencies come from two 12-inch (300mm) woofers in a vented enclosure, each with an Aquaplas-coated pulp cone. The Aquaplas treatment adds mass and damping to the cone material, which controls breakup modes and keeps the cone rigid where it needs to be. JBL used the same approach in its professional monitor line, and it gives the S9800 bass that is articulate rather than merely loud. The woofers are mounted to work as a pair, sharing the load and reducing distortion at high output levels.

The woofers also use JBL's patented SFG (Symmetrically Field Geometry) magnet structure. It is designed to reduce even-order harmonic distortion by creating a more symmetrical magnetic field in the motor gap. That detail doesn't show up in a spec sheet, but it helps the speaker play loudly while staying clear. Stereo Sound magazine in Japan named the S9800 one of its "Best Buy" speakers of 1999.

Fourth-Order Linkwitz-Riley Crossover at 900 Hz and 10 kHz

The crossover is a fourth-order Linkwitz-Riley design (24 dB/octave) with crossover points at 900 Hz and 10 kHz. It is a textbook topology, chosen for its phase behavior and its ability to keep a flat summed response across the crossover region. The steep slopes keep each driver well within its comfort zone, with minimal overlap and interference between adjacent drivers.

Dual sets of binding posts allow bi-wiring or bi-amplification. That suits the speaker's 92 dB sensitivity and its appetite for clean power. JBL recommends 200W - 500W per channel, with a maximum of 500W, so this is not a speaker for a 20-watt tube amp, sensitivity or not. The crossover components are a known weak point after two decades. Owners report that the electrolytic capacitors drift out of spec over time, and many recommend replacing them with film types as a preventative measure. Any prospective buyer should put that on the checklist.

Historical Context

The K2 S9800 was JBL's flagship consumer loudspeaker in the late 1990s, part of the K2 line the company positioned as its reference-grade series. The name came from K2, the second-highest peak on Earth. The S9800 was the top model in the K2 lineup at its introduction in 1997. The larger K2 S5800 was later introduced as a bigger, more expensive floorstanding model, which led to some confusion about which model held the flagship title.

JBL stated that the S9800 carried on the legacy of the original K2 series from the 1980s, a line that had established JBL's reputation for high-end consumer loudspeakers. Built in Northridge, California, the S9800 represented the company's home-audio ambitions at a time when the consumer market was increasingly dominated by mass-market products.

Collectibility & Value

The used market for the K2 S9800 has softened considerably from its original pricing, but these speakers still command serious money. Listings on Audiogon in 2023 ranged from $6,500 to $8,500 per pair depending on condition, while eBay listings from 2023-2024 showed prices between $5,000 and $7,000 per pair. In Japan, where the speaker was originally sold for ¥2,000,000 per pair, Yahoo! Japan Auctions listings from 2023 ranged from ¥350,000 to ¥800,000 per pair. That is a big drop from the original $18,000 - $20,000 US asking price, and it reflects the niche nature of a speaker this large and this demanding.

Prospective buyers should know the failure points. The beryllium dome tweeters and midranges are prone to denting if touched, and replacement domes are difficult to source and expensive when found. The woofers' foam surrounds deteriorate over time and need replacement. That is standard for speakers of this era, but it takes professional work given the size and weight of the drivers. The piano-gloss finish on the curved side panels is prone to scratching and requires careful handling. And as noted, the crossover capacitors age and drift, affecting crossover accuracy. None of these issues is insurmountable, but the S9800 is not a low-maintenance vintage purchase.

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