Altec Crescendo

1974 - 1970s

Altec Crescendo - floor system for 604E/605B coaxial monitors (1974)

The Altec Crescendo is a furniture-grade floorstanding cabinet made by the Japanese company Elektri and approved by Altec Lansing. It was built to give the 604E and 605B coaxial studio monitors a proper home in a living room. Introduced in 1974, it was a tuned, optimized enclosure for pro drivers that had only ever lived in control rooms.

Specifications

Type	2-way, 1-speaker coaxial system, bass-reflex floorstanding
Driver	604-8G or 605B 15" coaxial duplex speaker
Coaxial Configuration	15" woofer with integrated multicellular horn and compression driver
Crossover Frequency	604-8G: 1.5 kHz 605B: 1.6 kHz
Nominal Impedance	8 Ω or 16 Ω (depending on driver version)
Power Handling	35W continuous
Frequency Response	20 Hz - 20 kHz
Sensitivity	Approximately 98-100 dB/W/m (typical for 604-8G/605B)
Dimensions	690 mm W × 1,018 mm H × 485 mm D (27.2" × 40.1" × 19.1")
Weight	12.5 kg (27.6 lbs) per speaker (cabinet only, without driver)

Driver Configuration

Everything about the Crescendo depends on the driver you put in it. It was designed for two of Altec's coaxials, but the later, more common driver wasn't the 604E. It was its successor, the 604-8G.

604-8G Super Duplex (1973 onward)

Type: 15" coaxial duplex speaker. This is the one you'll usually find. Woofer: 15" with a 3" voice coil and Alnico V magnet. Compression Driver: 1.75" aluminum diaphragm sitting in the throat of the multicellular horn. Crossover: Internal network at 1.5 kHz. Sensitivity: 98 dB/W/m or better, so it plays loud on very little amp power. Impedance: Typically 8Ω, which is easier on amplifiers.

605B Duplex (1959-1964)

Type: 15" coaxial duplex speaker, the earlier version. Woofer: 15" with a shared magnetic circuit for the HF driver, a clever design that is slightly less efficient. Compression Driver: Same 1.75" diaphragm and horn. Crossover: 1.6 kHz internal crossover. Sensitivity: About 95 dB/W/m. That's still very efficient, but it needs a bit more power than the 604-8G. Impedance: Often 16Ω, which tube amp users might prefer.

You could order the Crescendo with either driver, but the 604-8G became the standard pairing. It's the more refined, higher-output driver.

Cabinet Design

Elektri did more than build a box around a 604. The Crescendo cabinet is a calculated bass-reflex design, tuned to get the best low-end extension out of the big coaxial cone. It's tall and slim, just over a meter high, which gives it the internal volume it needs without looking like a studio monitor in your den. The styling is calm 1970s Japanese modernism: clean lines, restrained grilles, and a finish meant to blend into both Western and Japanese interiors. The port is tuned for a 15-inch Alnico magnet driver. The driver mounts from the front, so you don't have to take the whole cabinet apart for service.

Coaxial Advantage

With a coaxial like the 604 or 605, the high frequencies fire from the center of the low-frequency cone. That gives you true point-source radiation. The result is strong phase coherence, so notes start and stop together across the frequency range. The multicellular horn controls the highs, which gives a consistent, predictable dispersion pattern. The soundstage is natural and stable, and instruments lock into place in three dimensions in a way that separate drivers struggle to match. It's the sound of a studio control room, in nicer wood.

Historical Context

By 1974, audiophiles were figuring out that the gear used to make records often sounded more real and direct than the hi-fi gear sold to play them. The 604 and 605 were studio standbys, but they lived in plain utilitarian boxes. Elektri in Japan designed the fix and got Altec's approval. It was a premium, niche product. In Japan, the 605B version sold for ¥228,900, which was serious money. It was for the listener who wanted the technical performance of a pro monitor in something that wouldn't cause a fight over decor.

Design Philosophy

The idea is simple: take a professional transducer and house it in a domestic enclosure. The cabinet is acoustically optimized for that specific driver, not a generic big box. The styling is neutral and stays out of the way of the driver. It's a complete system approach, built for a single purpose.

Performance Characteristics

Plug in a good amp and the Crescendo gives you the classic, dynamic Altec sound. It's efficient enough that a few watts from a small tube amp gets you lifelike volume and dynamics. The bass from the tuned cabinet is solid and extended, far better than the driver would manage in a poorly sized box. The midrange is where these coaxes live, with an immediate presence to voices and instruments. The top end from the compression driver is detailed and energetic, but it has a specific flavor. It isn't the airy, ultra-smooth top of a modern ribbon tweeter. It's the direct sound of a horn. Some listeners find it addictive, others need time to adjust.

Amplifier Pairing

The high sensitivity (95-100 dB) opens up a lot of amplifier choices. Low-powered tube amps are a good match - think 5 to 20 watts from a classic EL84, 6BQ5, or even a single-ended triode (SET) design. The speaker will reveal every nuance your amp can produce. Quality vintage solid-state from the 70s also works well, offering control and slam. Modern high-quality Class A or D amps work too. Match the impedance (usually 8Ω for the 604-8G, often 16Ω for the 605B), especially with tube outputs.

Legacy and Collectibility

Today, the Altec Crescendo is a collector's prize. It's rare, it's well designed, and it houses one of the greatest speaker drivers ever made. A clean, original pair with 604-8Gs can easily command $3,000 or more. The 605B versions are rarer and appeal to the vintage purist, sometimes trading for a bit less.

Restoration is usually about the driver, not the cabinet. Plan on a professional check of the 604/605: the crossover capacitors are due for replacement, the Alnico magnets might need recharging, and the woofer suspension (often cloth) should be inspected. The cabinets are typically sturdy, but a careful refinish can help.

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Documentation

Altec Crescendo specification sheets
604E and 605B driver technical documentation
Elektri cabinet design information
Altec home audio catalogs (1970s)