Infinity Alpha 1200s

At 57 pounds, it lands with the quiet authority of a speaker that knows it can move air—and your floorboards.

Overview

The Infinity Alpha 1200s is not a subtle piece of gear. It's a home theater subwoofer built for impact. It was released during the late 1990s or early 2000s and sits in the Alpha series, a lineup of home audio speakers from Infinity aimed at performance-minded buyers who wanted more than shelf-fillers but weren't chasing flagship status. It was made for living rooms and dedicated media spaces, where bass response was a requirement.

The headline spec is the claimed 500-watt RMS amplifier, a figure corroborated by both Crutchfield and a service manual hosted on Scribd. It is rated from 20Hz to 150Hz with no more than 0.1% THD, which points to a design aimed at clean, controlled output. The 12-inch driver uses Infinity's C.M.M.D. (Composite Metal Matrix Diaphragm) technology, which combines rigidity and lightness and was competitive for its time. The bass-reflex (ported) cabinet helps extend low-end reach. Frequency response is officially rated at 28Hz - 150Hz (±3dB), which is not earth-shattering by modern standards but was solid for mainstream high-performance systems of the era.

Owners report mixed experiences with longevity, particularly in the amplifier section. One AVS Forum post notes concerns about "older amps" used in these units, implying reliability issues in later years or after power events. A JustAnswer thread documents a user troubleshooting an Alpha 1200S that failed following a power outage. Some users still defend its performance. A Reddit commenter on r/hometheater called it “a good sub; not great,” but praised the RABOS room-tuning system as the feature that elevated it, tailoring response to real-world acoustics in a way few subs at the price point could match.

Specifications

Key Features

500-Watt RMS Class AB Amplifier

The Alpha 1200s specifies its 500-watt RMS amplifier clearly, with no peak power claims. Based on the era and design, the amp is almost certainly Class AB, a topology chosen for its balance of efficiency and linearity under load. The specification includes a strict THD ceiling of 0.1%. Damping factor exceeds 50, which helps keep the 12-inch cone under control during transients and reduces overhang and muddiness. Real-world performance depends heavily on component aging. Electrolytic capacitors and output transistors in amplifiers of this vintage can degrade, especially if units were run hard or in poorly ventilated spaces.

12-Inch C.M.M.D. Woofer in Ported Cabinet

Infinity's C.M.M.D. (Composite Metal Matrix Diaphragm) technology used a thin aluminum coating over a composite substrate to make a stiff, lightweight cone. In the Alpha 1200s, that driver sits in a bass-reflex enclosure, tuned via a port to reinforce output in the lower end of its operating range. The sub reaches down to 28Hz, though user measurements on forums suggest output drops to around 85dB at 25Hz. That is predictable for a 12-inch ported design. The cabinet is "furniture-sized," not something you hide under a couch.

Room-Adaptive Bass Optimization System (RABOS)

One of the more distinctive features of the Alpha 1200s is RABOS, Infinity's Room-Adaptive Bass Optimization System. It is not detailed in the fact sheet beyond anecdotal mention, but owner reports confirm it was a manual tuning system, likely involving internal switches or adjustments that altered EQ or damping to suit room placement. A Reddit user specifically credited RABOS with taking the sub from “good” to “great,” which implies that out of the box it might not deliver ideal response without calibration. It was a forward-thinking feature for its time, since subwoofer performance depends as much on room interaction as on raw specs.

Continuously Variable Low-Pass Crossover and Phase Control

The back panel has a continuously variable low-pass crossover from 50Hz to 150Hz and a 0/180-degree phase switch. These are essential for blending the sub with main speakers, especially in home theater setups where timing and frequency overlap matter. The line-level RCA inputs limit connectivity by today's standards, with no high-level inputs or digital processing, but they keep the signal path simple. The documentation gives no output count or type, which suggests it may lack speaker-level outputs or preamp pass-through, common on more flexible modern subs.

Collectibility & Value

Original pricing is sparsely documented, but a March 2004 AVS Forum thread title notes a sale at "$489 shipped," a snapshot of its market position in the early 2000s. No official MSRP has been located, and current collectibility data is absent. The sub doesn't command premium prices today, and it isn't widely sought as a vintage audio relic. Its value lies mostly in function, and owners keeping one running likely do so for performance, not nostalgia. The lack of spare parts documentation and the known amplifier vulnerabilities mean repairs can be a gamble. Units that have survived without power supply or output stage issues are likely still capable, but aging components remain a concern.

Similar items on eBay

No exact Infinity ALPHA SUBWOOFER listings are live right now — these searches show current Infinity 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

• Infinity 1000H
• Infinity 2000 A
• Infinity 2000 AXT
• Infinity 2000
• Infinity BETA C250