its cuz not many people have them ... let alone heard them ...
if u want a comparable sub to it ... there really isnt one .. i had very minimal listenting time with it .. but it got very loud and sounded somewhat good .. the guy that had it ... didnt have have it in a great enclosure ... kinda small .. but by listenting from ear he was hitting alot of the low notes .. and also picking up a wide range of frequenices .. if powered and installed correclty u will not be disappionted