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Jeff Markwart's Corner

Jeff Markwart’s Corner

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.


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Great Plains Audio was born out of the Altec Lansing corporation in 1998. It carries forward the loudspeaker design and manufacturing tradition that began with Western Electric in the early 20th century. Great Plains Audio is the only place where the legendary Western Electric/Altec Lansing sound reproduction technologies live on.

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