I'm trying to capture sony beta and sx tape into my iMac. I know I need a device between the deck and computer. I believe that device is the Canopus ADVC 110 converter (have yet to purchase this.) Will I be able to cable from that converter directly to the thunderbolt port on the iMac? There are no firewire ports on my iMac. Pretty confused on this process. thanks!
If you have firwire device but no firewire port you need an adapter. Apple offers one: http://store.apple.com/us/product/MD464ZM/A/apple-thunderbolt-to-firewire-adapter
If you tape deck is offering an output that the Canopus supports you will be able to capture your tapes that way. Alternatively you might want to look for a USB based solution that might be cheaper than using this device with an adapter.
I would suggest looking for an interface that offers SDI inputs (as I suppose both your SP and SX players have SDI outputs) with which you will have better results than with a composite inputs as is on the Canopus product.
SDI interface will allow syncing your interface with the player, and get embedded audio directly in the SDI stream.
An example of such interfaces is https://www.blackmagicdesign.com/products/ultrastudiousb3, other products might exist.