SCSI LVD to SE adaptor?

I've heard of adaptors that will let you use an LVD drive on an older SE chain. Anyone try this? And where can I get one?

I read you could do this without an adaptor, but it causes the LVD drive to run at SE speeds. This would be fine, if it worked.

I have an Adaptec 2940 UW, an old Micropolis 9g SE drive, and a new IBM 18g LVD drive. If I put the drives on together, the system will not boot. Put the drives on seperate and all works fine.