Last summer I purchased an early-1960's Allen TC-4 all transistor church organ that now occupies one end of the living room in our mobile home. The organ has four tone generators: Flute, Diapason, Celeste, and Reed. The Celeste combines with the Diapason, so there are three outputs: Flute, Diapason and Reed.
It came with two Allen furniture-grade Gyrophonic speaker cabinets with one Allen T-50 100 watt amplifier in each cabinet.
The amplifier in the Flute cabinet accepts only a single input. The output is monaural, and passes through a (post-amp) crossover unit that sends the upper frequencies to two rotating 12" (Jensen 220334 C12P ceramic 12" 25W 8ohm) speakers, and sends the lower frequencies to two non-rotating 15" (Jensen 220338 C15N ceramic 15" 50W 8ohm) speakers.
The amplifier in the Diapason/Reed cabinet accepts two inputs that have separate gain controls. The output is monaural, and passes through a (post-amp) crossover unit that sends the upper frequencies to three rotating 12" (Jensen 220334 C12R ceramic 12" 25W 8ohm) speakers and three tweeters, and sends the lower frequencies to two non-rotating 15" (Jensen 220338 C15N ceramic 15" 50W 8ohm) speakers.
Right now the Reed source, instead of being combined with the Diapason, is being routed to a third Allen T-50 100 watt amplifier that feeds a non-rotating Allen HC-15 speaker cabinet (with its own crossover, 15" speaker, 4" mid-range speaker and tweeter) and a non-rotating Allen HC-9 speaker cabinet (with its own crossover, 9" speaker and tweeter).
I have become increasingly unhappy with the sound quality of the organ pedal division, i.e. bass response. (A newer 1978 Rodgers organ that has a dedicated amplifier and subwoofer for the pedal division sounds much, much better.) In both Allen speaker cabinets, the pair of non-rotating 15" Jensen speakers occupy a space that measures (inside dimensions) 17 inches wide, 31.75 inches high, and 17.5 inches deep. The wood construction is very solid, but the back of each cabinet is ENTIRELY OPEN.
What I am wondering is whether the sound of these 15" speakers could be improved without building completely new cabinets. Should I enclose the backs of the cabinets, and either line the bare inside surfaces with something or pack them with something, and even possibly change the dimensions in the process. One friend recommended I buy a pre-amp crossover to permit separate amplification of the bass/low frequencies. I do have a Parts Express catalog, but don't know what I might need to order: subwoofer amplifier(s), carpet, acoustic foam, port tubes? Because I am a novice regarding speaker cabinet design and construction, I need someone to give me helpful advice about what to do to improve the sound of these large speakers without wasting my limited funds.
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