The original ALTEC 601 DUPLEX® was, as mentioned above, a field-coil device, assembled from units already in the Lansing® line when George Carrington, Sr. Lansing asseverate that he designed it, but the plain truth is that he didn’t, although he did design the tooling to build it. The origin of the concept of the ALTEC 604 DUPLEX® has been in dispute for many years. This difference is quite hearable, as the low frequency loading on the larger horn, coupled with a lower crossover point, giving it more naturalism and presence. Note the original and B style horn is a true, multicellular horn (cells go all the way back to the mouth of the throat), whereas the C – G style uses an extension to connect the smaller horn to the pole piece. Author has one of only two models made to create the photo.)Ĭ-G style on left, original & B style on right. (Scan of published advertising literature.

The most recent 604 (K-series) used a small constant-directivity MANTARAY® horn (see image below). Later versions (C through E) used sectoral horns with vanes.

The high frequency sound waves traveled through a hole bored through the low frequency pole piece, exiting through a small multicellular horn. It utilized a new, permanent magnetic structure of Alnico V, had a 15″ low frequency loudspeaker with a high frequency compression driver mounted to the rear of it’s magnet. In 1944, the first of the world-renown ALTEC “604” series of DUPLEX®Loudspeakers (left) was introduced. Thus began the famous DUPLEX® series of loudspeakers. Called the “601”, it was of the field-coil type and included a small-format HF compression driver mounted to a 12″ low frequency loudspeaker with a hole bored through the pole piece of the woofer which connected to a 2 x 3 multicellular horn. Altec Lansing invented the first DUPLEX® Loudspeaker System in 1941 (some sources say 1943 – we’re really not sure).

Altec lansing atp3 white