impedance matching

[noel]

Hey all,
I've got a pretty easy question.  I've got a head (selmer treble n bass 50) that has 15 or 7.5 ohm speaker out jacks.  Not many cabs are 15 ohms anymore...looks like 16 or 8 ohm is easier to find.  Could I safely plug a 16ohm cab into the 15 ohm socket or 8 into the 7.5?  What are the pro's and cons of doing something like this etc?  Is there any way I can modify either the speaker outs or the cab speakers such that the impedance is the same?
thanks

[mckinnon audio]

  Hi there,no need to mod anything,they'll work fine.Impeadance is resistance in an A.C. circuit,when you use a volt meter,you're using D.C. volts because of the battery in the meter. D.C. resistance and A.C. impeadance will never be the same,mainly because the D.C. isn't changing polarity every second like the A.C. is. Having said that,your 8 ohm spkr. will read around 5.6 to 6.3 ohms on a meter,your 16 ohm spkr. will read around 11.3 ohms.When your amp is in use,the impeadance is changing all the time,depending on what note(freq.)you're playing at that point in time,hope this helps,good luck,Mel.

[noel]

Hey Mel,
Thanks for the info.  So just to clarify, using an 8ohm or 16 ohm cabinet wont be a problem?!?! 
thanks,
Ryan

[mckinnon audio]

  Hi there,just plug the 8 ohm cab. into the 8 ohm jack and the 16 ohm one into the 16 ohm jack and you'll be fine,good luck,Mel.