[Overview]
This is a pair of ALTEC 606 corner bass-reflex speaker enclosures fitted with 604D Duplex 16Ω drivers, produced by ALTEC from 1945 through the late 1960s.
The “604” Duplex system is considered one of ALTEC’s three major speaker systems, alongside the company’s renowned “Voice of the Theatre” and “Iconic” systems.
The famous “612” system was widely used as a standard monitor speaker in recording studios. In addition to this model and the 612, ALTEC introduced the 605, 613, 614, and several other models in rapid succession, creating a major sensation in the audio industry at the time.
Among these models, the 606 stood out for its corner bass-reflex design. Its relatively compact size and furniture-like appearance made it highly suitable for home interiors. As a result, it was installed not only in theaters and auditoriums, but also in the homes of many audio enthusiasts, where it remained popular for many years.
Another notable feature of this enclosure is its screw-fastened construction, with the use of adhesive kept to an absolute minimum.
More than 150 screws were generously used in each cabinet, minimizing unwanted resonance while allowing the desirable resonance and natural tonal character of the enclosure to remain.
■ 604D + N1600B ■
This system is equipped with ALTEC’s American-made 604D two-way driver, finished in the company’s beautiful and iconic ALTEC Green.
The 604D is the predecessor to the legendary 604E, which is widely regarded as one of the finest loudspeakers in ALTEC’s history.
One of the main differences between the 604 and the well-known 605 series is that the 604 was developed as a professional-use driver. It delivers dynamics that clearly distinguish it from domestic models, while also providing a delicate, smooth tonal character.
The result is an exceptionally powerful and well-balanced monitor sound.
The system uses the N1600B dividing network. Its seamless integration between the low- and high-frequency sections is on an entirely different level from that of a conventional crossover network.
The 604D is also highly regarded for its excellent efficiency and can be driven without difficulty by a low-powered amplifier.
The enclosures feature an attractive mahogany finish and are rare, specially ordered cabinets designed specifically for the 604C and 604D drivers.
Our honest first impression after listening to these cabinets was simply that they sounded outstanding.
They perform every bit as impressively as the 612 enclosure, producing a well-balanced response from the highest frequencies to the lowest and fully realizing the potential of the 604D.
In terms of tonal balance, imaging, clarity, consistency, and power, these cabinets are virtually flawless.
They completely overturn the commonly held belief that the 612 enclosure is the only ideal choice for the 604 series.
Due to their age, the cabinets show some minor paint loss, scratches, and signs of use. Aside from these cosmetic imperfections, they remain in generally good condition.
We have included as many photographs as possible so that the exterior condition can be carefully inspected.
■ Sound Quality ■
This cabinet served as the foundation for the later 821A and many other corner-style speaker system designs.
Although the balance between the high and low frequencies is relatively flat, each frequency range remains clearly defined, producing a tight and focused sonic image.
The sound has a distinctively dry character, yet it retains the necessary degree of richness and warmth.
Its dense, persistent tonal texture is particularly impressive and is characteristic of a true ALTEC enclosure.
[Specifications]
604D DUPLEX 16Ω
Diameter: 15 inches
Design: Two-way coaxial driver
Magnet: Alnico V
Impedance: 16Ω
Frequency response: 30Hz–20,000Hz
Lowest resonant frequency: 40Hz
Power handling: 35W continuous / 50W peak
Crossover frequency: 1.6kHz
Magnetic flux density: 13,000 / 15,500 gauss
Dimensions: 38cm outside diameter
N1600B
Crossover frequency: 1.6kHz
Attenuation characteristics: LF −6dB/octave, HF −12dB/octave
Level control: Three-position selector
[Enclosure Specifications]
Constructed from Douglas fir plywood.
We have included numerous exterior photographs so that you can carefully review the cosmetic condition.
Dimensions per speaker: 800mm W × 910mm H × 425mm D
Weight per speaker: Approximately 60kg
