I just picked up a single JBL C-38 cabinet with a D131 12" full range driver inside. It has the silver dust cap and untreated paper surround, 16 ohms. I hooked it up to my Marantz 2330B receiver set to mono and played a mono recording, Montserrat Caballe singing Bellini's "Casta Diva" with a Shure M44-1 (1 mil stylus). It sounded so-so. Weak in the low end and heavy mid range when compared to a Dynaco A25 10" 2-way speaker. The driver is extremely well made, cast frame, 4" voice coil, heavy magnet and the cabinet is over twice the size of the Dynaco enclosure. Why does the JBL sound so poor when compared to a speaker was only about $80.00 when it was being manufactured? Will it benefit from a crossover and tweeter? If so, which ones. Should the enclosure be modified? Thanks in advance.