The Altec HF horns are originally made to go down to 500Hz, but the response is more irregular down there. In the later years, Altec reaised the crossover point to 1200Hz (I used to work for them when they were in CA). The 15" woofer in the LF horn is actually very light, and has good response a bit beyond the crossover point.

The DBX subharmonic synthesizer you have is actually used in movie dubbing stages to create the LFE track in a lot of instances. I can imagine what they do with a bass shaker

Some people are amazed that someone would actually use all tube amplification in a home theater, much less a single ended tube amp that puts out a mighty five watts! Without exception, people have been amazed when hearing the results.....

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The Soundhound Theater