Picked these up today--they will be a gift for a relative after the refurb. The XI was the bottom of the line in 1971 at $80. Next step up was the Mini II at $100. The TOTL Model III Lowboy was $300. The XI is a simple 2-way bass reflex system with a 10" woofer and phenolic ring tweeter, crossed over at 1.8kHz. Freq response is reported to be 45-17k +/- 3db. The 10" Woofer W-11 was used in XI, XIa, XIb, XII. The 4" phenolic ring tweeter RT-11 was used only in XI. First impression: Nice speakers