I copied the quote below from another thread out of the archives. FWIW these are considered to be very good drivers and reconers often have ready-to-go supplies of these at very good prices.. it'll cost you at least as much to get a competetive driver. These drivers get blown because users fail to understand the limitations of the cabinets they are loaded in, the LS608 for example is a 50hz and up box and driving it with any power below that frequency is a great way to toast the driver from overexcursion. If you're happy with that you should be able to scare up some drivers with a web search.
"The original woofer in the LS608 was the RCF L18P540, which was superseded with the RCF L18Y800, which was in turn superseded with the B&C manufactured Yorkville 18/029. The xmax on the last two are close to 9 mm each."
That quotation above is mine.
I own 4 of those subs among others.
The LS608 is not a 50 hz and up box. It is minus 3db@44hz
You LPF them at 40 hz.
These are the real 1w1m numbers.
It is 95db@41 hz, 101db@45 hz, 102db@50, 103db@60 hz, 103@70 hz,101@80 hz, 103@90 hz, and 103@100 hz.
"The response drops like a stone at 50 hz". Someone posted this unsubstantiated crap and now it is gospel. The numbers above do not support that.
I have read this internet BS about this speaker for years all over the internet,
Compare this speaker to well regarded SRX-718 and you will find that it outperforms that box from any number above 45 hz.
I have the actual Yorkville test charts.
The woofer that you require will need to have an fs of close to 30 hz with an xmax of 9mm, and a bl factor above 25 Tesla Meters (at a bare minimum), in order to deal with the compression loading.
There is not much on the market available new that one could call inexpensive with those characteristics. Most candidate woofers will be well in excess of $300.00 US with a few exceptions.
There are no free rides in the PSR world.