Hi, my name is Jeff Markwart, and I’ve used numerous Altec Lansing Professional speaker products since the late 1980s in home stereo settings. I’m referring to the Altec Lansing Professional Products that were produced from the 1940s through the late 1990s, and are best known as “Voice of The Theatre” components. Like many Altec users, I’ve been able to achieve improved sonic performance from these amazing inventions by making small changes to drivers, enclosures and crossovers.
My “Corner” of the GPA website is intended to provide useful information to audio amateurs and others who are seeking improvements in the sound of their Altec speaker products. I do not manufacture nor sell any of the crossover solutions I have listed here for the Altec 604 and 605 series, but rather encourage the Audio Do-It-Yourself community to further experiment with my ideas on their own. My crossover designs are free for non-commercial use.
Although my original idea was to publish my Altec Duplex phase corrected crossover designs, it continues to grow and now includes a number of related vintage Altec Lansing items of interest.
Altec Lansing 604 & 605 Crossover Options
The following posts and referenced pages contain some ideas I’ve had about improving Altec 604 & 605 Duplex crossovers.
If you would like to discuss my Phase Corrected Altec 604 crossovers, head on over to the Great Plains Audio Altec Lansing Community.
The parts and bi-wiring layout I have specified here for building my various 604 and 605 phase correct crossovers are ones I have used successfully with vintage Altec Lansing drivers in the past. The parts are not inexpensive, nor the layout … Continue reading →
In early 2008 I had the opportunity to evaluate a loaned Altec Lansing 604-8K utilizing the CLIO system. The driver was an early unit (serial # 3403, date stamped DEC 1982) and was equipped with the original factory low frequency cone and … Continue reading →
Ferrite Magnet 604s As I mentioned on the Home Page, horizontal separation between voice coil gaps for ferrite magnet Altec Lansing 604 & 904 duplexes is 2.8125”. This distance produces 112 degrees of phase shift between the driver’s acoustic centers at … Continue reading →
Enter the H Model… In early 2004 I acquired a pair of 604-8Hs, the last ALNICO magnet duplex model Altec produced before they switched to ferrite magnets. It was also the first Altec duplex model that combined the Tangerine phase plug with a … Continue reading →
I acquired a pair of 604Bs in the early 1990s, and had them refurbished with new 604E low frequency (LF) cones and new 16 ohm high frequency (HF) diaphragms at the Altec factory in Oklahoma City, Oklahoma. I subsequently used … Continue reading →