Sony SS-7110 ULM11 (circa 1973)

Name: Sony ss-7110
Brand: Sony

At 13kg and nearly 55cm tall, these bookshelf speakers carry a heft and ambition that belies their class.

Overview

The Sony SS-7110 ULM11 isn't chasing delicacy. This is a statement piece from Sony's early 1970s engineering push—a 2-way, bass-reflex bookshelf speaker built with obsessive attention to magnetic linearity and mechanical integrity. Marketed around 1973 with a price tag of ¥19,000 per unit, it was positioned as a serious high-fidelity option during a period when Japanese audio firms were aggressively refining their technical credentials. Despite its "bookshelf" classification, the dimensions—326 mm wide, 550 mm high, and 290 mm deep—suggest a speaker that leans toward compact floor-standing proportions, demanding space and stability. The walnut grain finish adds a conventional touch of warmth, but the real story is inside: a 20 cm cone woofer and 2.5 cm dome tweeter anchored by Sony’s Ultra Linear Magnetic Path (ULM) technology, a design meant to surgically reduce distortion at the magnetic core.

Owners report that the ULM system isn't just marketing fluff. By introducing a notch in the center pole of the magnet and capping it with thick copper plating, Sony tackled nonlinear magnetic distortion—a subtle but pervasive flaw in many drivers of the era. This, combined with a metal bobbin in the woofer voice coil, was intended to improve power handling and thermal stability. The 50W maximum input (measured with weighted pink noise) wasn't class-leading, but it reflected a design focused on clean headroom rather than brute force. The 87dB/W/m sensitivity is modest, suggesting these speakers benefit from a robust amplifier to shine, especially given their 6 Ω impedance, which demands a current-capable output stage.

The crossover is anchored at 3.5kHz, a relatively high point that places significant demands on the 2.5 cm dome tweeter. To manage this, Sony equipped it with a continuously variable level control, allowing users to tailor the high-frequency balance—an unusual level of user tuning for the time. The network itself uses an air-core inductor with low DC resistance, avoiding the saturation issues of iron-core coils under high signal loads. Mylar capacitors are specified in the crossover, contributing to what was likely a clean, low-hysteresis signal path. The cabinet, constructed from 20 mm thick hard particle board and reportedly featuring a double-layer structure, aims to suppress panel resonance, though no internal bracing details are documented.

One of the more intriguing mechanical touches is the woofer’s edge: a cloth surround treated with a special thin rubber and airtight sealing process designed to eliminate a common 400 Hz response dip. This suggests Sony was addressing a known acoustic weakness in cone drivers of the period. The dust cap also plays a role beyond protection—it's said to contribute to sound insulation and prevent unwanted resonance from the voice coil cavity. Even the lead wires use high-purity copper foil treated with resin for durability, a detail often overlooked but critical for long-term reliability in high-excursion drivers.

Specifications

Manufacturer	Sony
Model	SS-7110 ULM11
Product type	2-Way, 2-Speaker, Bass Reflex System, Bookshelf Type speaker system
Production years	around 1973
Original price	¥ 19,000 (1 unit, around 1973)
Woofer	20 cm cone type
Tweeter	2.5 cm dome type
Playback frequency band	45 Hz ~ 25000 Hz
Output sound pressure level	87dB/W/m (New JIS)
Impedance	6 Ω
Maximum allowable input	50W (weighted pink noise)
Crossover frequency	3.5kHz
External dimensions	Width 326 x Height 550 x Depth 290 mm
Weight	13kg
Enclosure structure	Bass-reflex
Enclosure material	20 mm thick hard particle board
Finish	Walnut grain

Key Features

Ultra Linear Magnetic Path (ULM) Magnetic Circuit

The SS-7110 ULM11 leverages Sony’s ULM technology to combat magnetic distortion. A notch is machined into the center pole of the woofer’s magnet structure, then filled with a thick copper cap. This copper element acts as a shorting ring, damping flux modulation and reducing harmonic distortion caused by magnetic nonlinearity—especially at low frequencies and high excursions. This was a sophisticated solution for 1973, reflecting Sony’s investment in driver-level engineering rather than just cabinet or crossover design.

Metal Bobbin Woofer Voice Coil

Unlike the paper or Kapton bobbins common in the era, the SS-7110’s woofer uses a metal bobbin. This improves heat dissipation from the voice coil, allowing the driver to handle higher continuous power without thermal compression or failure. It also adds mechanical rigidity, reducing deformation under high drive levels. While metal bobbins can increase moving mass slightly, the trade-off here was clearly in favor of durability and thermal performance.

Scandinavian Pulp Woofer Cone

Sony specified carefully selected Scandinavian pulp for the woofer cone, processed using proprietary paper manufacturing techniques. This suggests a focus on consistent fiber structure and damping characteristics, aiming for a balance between stiffness and internal loss. Such materials were believed to reduce breakup modes and deliver a more natural midbass response, though the exact sonic signature depends heavily on the cone’s profile and treatment.

Airtight Rubber-Edge Surround

The woofer’s surround uses a cloth base impregnated with a special thin rubber and sealed for airtightness. This design targets a known issue: a response dip near 400 Hz caused by air leakage or flexing at the cone’s perimeter. By eliminating this "valley," Sony aimed for smoother lower-midrange transition and improved cone control during excursion.

Continuously Variable Tweeter Level Control

Mounted on the crossover network, this feature allows real-time adjustment of the tweeter’s output level. Given the 3.5kHz crossover point—high for a 20 cm woofer—this control lets users compensate for room acoustics or personal preference, softening brightness if needed or boosting presence. It’s a rare inclusion in a bookshelf speaker of this vintage, indicating Sony’s intent to deliver a tunable, system-ready product.

Air-Core Crossover Inductor with Low DC Resistance

The crossover uses a large air-core coil, avoiding the magnetic saturation and hysteresis losses associated with iron-core inductors. This ensures the inductor remains linear even at high signal levels, preserving transient detail and reducing distortion. Combined with mylar capacitors, the network is built for signal integrity, not just frequency division.

Dust Cap with Sound Insulation Function

Beyond protecting the voice coil, the dust cap is engineered to provide acoustic insulation, minimizing rearward sound radiation from the motor structure. This reduces interference with the main cone output and helps prevent coloration caused by cavity resonance behind the driver.