KLH Model Eleven (1959–1965)
A self-contained transistor stereo that put Henry Kloss's acoustic suspension bass in a box you could carry.
Overview
The KLH Model Eleven was introduced in 1959 as KLH's very first product. It was a complete stereo system in one wood cabinet wrapped in vinyl: amplifier, AM/FM tuner and two pairs of speakers, with a carrying handle on top. It wasn't the first portable stereo ever made, and owners on forums say that claim is debated. The consensus that holds up is that it was the first high-quality portable. It showed a battery-powered box could deliver real hi-fi sound instead of the thin, tinny output people expected from anything you could carry.
At $199.00 it cost more than the typical transistor portables of the era. Some sources list $199.50, likely a typo that's never been resolved. It was also cheaper than the competing portable consoles, and the engineering justified the premium. This was one of the first consumer transistor amplifiers, using early solid-state circuitry to get the low power draw that made battery operation feasible in the first place. A tube-powered console was no longer the only option for the beach.
The Model Eleven paired a transistorized amp rated at 6 watts per channel with a pair of 6-inch woofers and 2-inch tweeters in a sealed enclosure. That's not a lot of power on paper. But the acoustic suspension design - Henry Kloss's signature approach, carried over from his work at Acoustic Research - squeezed surprisingly deep bass out of the compact cabinet. Owners consistently describe the sound as warm, full, and capable of filling a room, which is not the language people usually use about 1959 portables.
Key Features
Early Transistor Amplifier
The amplifier section is historically significant on its own. KLH built the Model Eleven around early silicon transistors, making it one of the first consumer audio products to go solid-state. The payoff was twofold: it ran cool enough for a sealed portable cabinet, and it sipped power slowly enough that a set of D-cell batteries could keep the music going. The specs hold up reasonably well even by modern standards — frequency response is rated at 20Hz–20kHz (±0.5dB) per one source, though classic-audio.com lists a more conservative 30Hz–20kHz, and total harmonic distortion comes in at less than 0.5% at rated output. Signal-to-noise is a respectable 70dB below rated output. For a 1959 portable, those numbers are genuinely impressive.
Acoustic Suspension Speaker System
Instead of the open-back or ported enclosures typical of the era's portables, KLH used a sealed acoustic suspension design. The two 6-inch woofers worked against the trapped air inside the cabinet, which let them produce bass that seemed impossible for the box size. The two 2-inch tweeters handled the top end, and the whole thing presented a 4-ohm load to the amplifier. Collectors note a practical benefit decades later: the speaker surrounds aren't foam, so there's no rot issue. That's one less thing to rebuild on a survivor.
Self-Contained AM/FM Tuner
The Model Eleven packed an AM/FM tuner into the same cabinet, with analog tuning via a mechanical dial and built-in antennas. No external speakers, no separate amp, no wires to trip over. The trade-off is that there are no auxiliary input jacks, and owners still grumble about it. You can only listen to the tuner. No tape deck, no CD player, no external source of any kind. For a modern collector, that's the single biggest limitation.
AC and Battery Power
Portability meant battery operation, and KLH used D-cells - eight of them according to classic-audio.com, though some forum sources say six, a conflict that's never been fully settled. Either way, you could get up to 20 hours of music per set, which was generous for the era. Near a wall outlet, the built-in AC power supply took over. The unit ran from batteries when you were out and plugged in at home for longer listening sessions. That dual-power approach was novel in 1959.
Historical Context
The Model Eleven was KLH's first product, and it was the reason the company existed. Henry Kloss had co-founded Acoustic Research before leaving to start KLH with Malcolm Low and Josef Hofmann. The Model Eleven was the debut product, and it set out what the new company stood for: serious engineering applied to categories nobody had thought to take seriously. The portable stereo had been a novelty before. KLH made it a legitimate hi-fi instrument.
KLH's own advertising leaned on the evolution angle. A 1966 ad in High Fidelity (May 1966, p.45) boasted of "128 quiet changes" made to the Model Eleven between its 1962 introduction and 1966. The company kept refining the design year after year without changing its appearance. That continuous improvement became a KLH hallmark. The Model Eleven didn't look much different in 1966 than it had in 1962, but it was a better phonograph.
The "first portable stereo" claim needs a footnote. Online discussions on forums like Audio Karma point out that KLH wasn't literally first to market with a portable stereo. What the Model Eleven did was set the quality bar. As one forum member put it, "It's often called the first portable stereo, though that's debated - it was certainly the first high-quality portable."
Collectibility & Value
The Model Eleven is a collector's item now. Forum members report seeing them listed on eBay for $500 - $800 in good condition, and one YouTube reviewer picked one up for $350. The wide range reflects condition more than anything. These are 60-plus-year-old electronics, and survivors vary enormously.
The common problems are well documented by owners. Tuner drift is the big one: the FM section drifts off frequency after a few minutes and needs constant re-tuning. Old electrolytic capacitors in the amplifier and power supply are another known failure point, and the standard advice is to recap the amp before trusting it with regular use. Battery leakage is a perennial problem, with the original battery compartment often corroded from decades-old D-cells left inside. The controls get scratchy with age, and the vinyl cabinet covering chips and peels while the grille cloth frequently shows damage.
The repairs are manageable for someone with basic electronics skills. Owners who've done a recap describe it as "not hard," and it makes a big difference. A tuner alignment is recommended if you plan to use FM heavily. The golden rule from the forums is to clean the potentiometers with DeoxIT before trying anything else. That solves a surprising number of problems.
Parts are harder. Everything is discontinued and obsolete, so you'll be sourcing generic capacitors from Mouser or Digi-Key rather than original KLH parts. Replacement drivers are very hard to find. Original KLH woofers and tweeters rarely surface, and you may need to get creative if one is blown. Reproduction grille cloth doesn't exist, so owners suggest trying a fabric store with acoustically transparent material. The sealed speaker surrounds are the one bright spot: no foam rot.
Owners are enthusiastic about these units. The praise is consistent: "It sounds remarkably good for its size - warm and full." "The bass is surprisingly deep thanks to the acoustic suspension design; it really fills a room." "I've heard a lot of vintage portables; this one is in a different league." One collector calls it "the crown jewel of my collection." The criticisms are just as consistent - the lack of inputs, the tuner drift, the battery cost - but they rarely dampen the enthusiasm. As one YouTube reviewer put it, "It's beautiful, it's heavy, it's got that wonderful KLH smell of old wood and electronics."
If you're shopping for one, the practical advice is straightforward: budget for a recap, check the battery compartment for corrosion, and be prepared to live with the tuner drift unless you invest in alignment. The Model Eleven will never be a modern convenience — it's a tuner-only system with no aux input and controls that need attention. But as a piece of audio history, as the product that proved portable could mean high-fidelity, it's hard to beat. Owners keep them on bookshelves, show them to guests first, and fire them up to demonstrate what 1959 could do when someone took portability seriously.
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