When you say "woofer" are you talking along the line of something like a sub-woofer. The PSR-1500 has decent speakers, but part of the reason it pumped a bit was because the 1500's amp was (12w), and many of the previous PSR's were running on half of that.
I think the PA-500's amp is (15w), but based on the specs the speaker configuration for the unit is 2 dual cone speakers... The 1500 had its tweeters separate from the main speakers. With a 15w amp I can't imagine the PA-500 not thumping.... However isn't the EQ on the 500 fixed?
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