Mint condition 15" biflex drivers. Good from 40-10khz or so on open baffle or in large box. I used on an Esmilla style baffle with a ribbon tweeter crossed at 6khz with a 1.5uF cap. Sound is amazing. Same woofer cone as the 515 and 604 series etc... Mechanical cross to inner cone at around 1.5khz. These are amazing and undervalued drivers. Matching tweeters available for free to buyer (currently at my friend's house but can be shipped). $225 plus shipping from 97333. Pictures available. email harryzweben@yahoo.com.