[Ron]

 Thought I would pass on this bit of information for those DIY's who have never installed Electra Tube input connectors. The required whole size for these connectors is 7/16". I have found that a 7/16" Forstner drill bit works better than a sprial type drill bit in that it provides a tighter fit.

[sl_1800]

Ron I recently installed the Electra Tube connectors on some speakers.  Drilled the 7/16 hole with a spiral bit and could not get the Tube connector in the hole.     Then measured my CHEAP drill bit with a digital micrometer and found it was undersized!!  Went up to the next size which turned out to measure 7/16 and all was good.  For anyone else out there installing these, make sure your drill bit really is 7/16.

[Ron]

 Sprial bits are also very good too, but I personnally like to use Forstener bits. They seem to provide a smoother bore in my opinion. I certainly agree that it is always a good idea to measure the actual size of any drill bit before you use it to verify that the size is correct.