Heathkit AS-1348: The DIY Enthusiast’s Gateway to Deep Bass

Name: Heathkit AS-1348
Brand: Heathkit

In the late 1970s, when high-fidelity audio was rapidly evolving and home stereo systems were becoming more sophisticated, Heathkit stood as a beacon for the do-it-yourself (DIY) electronics community. Known for offering affordable, build-it-yourself kits ranging from test equipment to complete audio systems, Heathkit empowered hobbyists to learn electronics while creating functional, high-quality gear. Among their diverse catalog was the AS-1348, a unique and often overlooked product that catered specifically to audiophiles looking to enhance their speaker systems with dedicated low-frequency reproduction.

The Heathkit AS-1348 was not an amplifier, receiver, or speaker in the traditional sense. Instead, it was a passive subwoofer system—a kit that included both a crossover network and a bass-reflex enclosure designed to be paired with a separate 12-inch woofer. Marketed as a way to extend the bass response of existing bookshelf or floor-standing speakers, the AS-1348 allowed users to build a custom subwoofer solution without the complexity of active electronics. It was a clever, cost-effective approach to achieving deeper, more powerful bass in an era when powered subwoofers were rare and prohibitively expensive.

Technical Specifications

The AS-1348 was designed around simplicity and accessibility. It required the builder to supply a compatible 12-inch speaker driver (typically 8 ohms), while Heathkit provided the enclosure, crossover components, and detailed assembly instructions. The system was entirely passive, meaning it connected between the amplifier and main speakers, splitting the audio signal acoustically rather than electronically.

Specification	Detail
Type	Passive subwoofer system with crossover
Enclosure Type	Bass-reflex (ported) design
Driver Compatibility	12-inch (30.5 cm), 8Ω recommended
Crossover Frequency	Approximately 100 Hz (low-pass)
Crossover Type	12 dB/octave passive filter
Dimensions (H×W×D)	20" × 14" × 16" (50.8 × 35.6 × 40.6 cm)
Weight (empty)	~25 lbs (11.3 kg)
Material	Medium-density fiberboard (MDF) with walnut veneer
Inputs/Outputs	Screw terminal inputs for amplifier; internal speaker connection
Assembly Required	Yes (kit form)
Power Handling	Dependent on installed driver and amplifier

The bass-reflex port was tuned to optimize low-frequency extension, typically reaching down to around 40–45 Hz, depending on the driver used. The crossover network was a second-order design, using inductors and capacitors to roll off mid and high frequencies sent to the subwoofer, ensuring a smooth transition with the main speakers.

Sound Characteristics and Performance

As a passive system, the AS-1348’s sonic performance was heavily dependent on the amplifier and the main speakers in the system. It did not amplify the signal but instead redirected low frequencies to the dedicated woofer. When properly integrated, the AS-1348 could significantly improve the bass foundation of a stereo setup, adding weight and authority to music and film soundtracks alike.

Users reported a tight, controlled bass response when paired with a high-quality 12-inch driver and a robust amplifier. The bass was not boomy or overblown—typical of well-designed passive systems of the era—but rather musical and articulate, enhancing kick drums, pipe organs, and orchestral bass lines without muddying the midrange.

However, due to its passive nature, the AS-1348 required careful speaker matching. If the main speakers were inefficient or the amplifier underpowered, the system could strain, leading to inconsistent frequency blending or even phase issues. Optimal results were achieved when the main speakers had a natural roll-off near 100 Hz, allowing the crossover to do its job seamlessly.

Notable Features and Innovations

What made the AS-1348 stand out in Heathkit’s lineup was its practical approach to bass extension. At a time when most consumers either accepted the limitations of their speakers or invested in large, full-range floorstanders, the AS-1348 offered a modular upgrade path. It was especially appealing to:

DIY enthusiasts who enjoyed building and customizing their gear
Budget-conscious audiophiles who wanted deeper bass without buying a new speaker system
Home theater pioneers experimenting with surround sound and low-frequency effects (before the advent of LFE channels)

The kit included precision-cut MDF panels, high-quality terminal connectors, and a comprehensive instruction manual with wiring diagrams and alignment tips. The walnut veneer finish gave it a classic, warm aesthetic that blended well with 1970s and 1980s living room decor.

Another innovation was the modular design—users could experiment with different drivers and damping materials to tailor the sound to their preferences. This flexibility was rare in pre-built subwoofers of the time and reflected Heathkit’s philosophy of education through hands-on experience.

Common Issues and Maintenance

Like many vintage audio kits, the AS-1348 is now approaching 45 years of age, and surviving units may require attention. Common issues include:

Deteriorated speaker surrounds: Foam or rubber surrounds on installed woofers often degrade over time, leading to rattles or loss of bass response. Replacement with modern equivalents is recommended.
Crossover component aging: Capacitors and inductors can drift in value or fail, especially if the unit was used heavily. Checking or recapping the crossover ensures optimal performance.
Cabinet integrity: While MDF is durable, port tubes can become loose, and veneer may chip. Reinforcing joints and resealing ports can restore acoustic integrity.
Terminal corrosion: Screw terminals may oxidize; cleaning with contact cleaner improves connectivity.

Maintenance is relatively straightforward for those with basic soldering skills. Replacement drivers (such as the Eminence LAB12 or Peerless XLS) are readily available and can breathe new life into an original AS-1348.

Current Market Value and Collectibility

The Heathkit AS-1348 is not a high-profile collector’s item like the legendary AA-141 amplifier or HW-101 transceiver, but it holds a niche appeal among vintage audio and DIY communities. Complete, assembled units in good condition typically sell for $100–$200, depending on driver quality and cosmetic state. Unassembled kits or original boxes with manuals can fetch slightly more from Heathkit memorabilia collectors.

Its value lies less in rarity and more in historical significance—it represents a time when consumers could actively participate in building their audio systems. For modern hobbyists, the AS-1348 offers a rewarding project: restoring a piece of audio history while gaining insight into passive crossover design and enclosure acoustics.

Conclusion and Legacy

The Heathkit AS-1348 may not have revolutionized the audio world, but it exemplified the spirit of innovation and accessibility that defined Heathkit’s golden era. As a passive subwoofer solution, it bridged the gap between modest speaker systems and full-range sound, offering a practical, educational, and affordable upgrade path.

Today, it stands as a testament to the DIY ethos that once thrived in American electronics. While modern active subwoofers offer superior control and integration, the AS-1348 remains a charming and functional relic of a time when audiophiles didn’t just buy gear—they built it.

For vintage audio enthusiasts, the AS-1348 is more than a speaker cabinet—it’s a hands-on lesson in acoustics, a piece of audio history, and a reminder that sometimes, the best sound comes not from a factory, but from your own workshop.