Just recently bought a evh 5150 50 watt head and the only cab i have at the moment is a line 6 spider 3 4x12 cab. Seeing if i can plug into it until i buy a new cab. New to tube heads...
Match the impedance. You'll be fine.

Also use a speaker cable.
Bass Gear:

Mensinger: Speesy
Fender Precision 1989 (CIJ Rosewood)
Fender Steve Harris (CIJ)
Lakland J Sonic 5
Epiphone Explorer
Maruszczyk (custom) Jake

Ashdown CTM 100
Last edited by Fisheth24 at Dec 27, 2014,
yes you can, but I believe the L6 cab is stereo at 8 ohms each side. So you will need to set the amp to 4ohms if you plug into both sides of the cab. You will need 2 speaker cables to do this.

If the EVH does not have a 4ohm setting put it in 8 ohms and only plug into 1 8ohm jack on the cab.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
5150 III 50 watt has parallel speaker outputs and a 4/8/16 Ohm selector switch. Do what Robb says.
Ibanez Prestige RG852MPB
Ibanez Prestige RG652KFX
Schecter Loomis NT
EVH 5150 III 50
PRS 212 DB
Line 6 POD HD500X
Deadhorse OD/Boss HM-2