Speaker impedance question

[bagman67]

This one goes out to my electrical engineer/audio pro buddies.


As many of you know, Carvin has all but gone out of business. They are no longer manufacturing amps and cabinets.  I scored a brand new V3M head on eBay that Carvin are blowing out (there are still a dozen or so left, if y'all are interested).  For the time being I will play through a 16-ohm 1x12 cheapo cab I already have until I can afford to drop a few more bucks on something that specifically suits my ear.


So my questions are the following: 


Given the amp is switchable between 4, 8, and 16 ohms, I can do what I want when it comes to the eventual cab replacement.  Is there a tendency for specific sonic characteristics to be emphasized or diminished at different impedances?  If so, what are they?  Should I expect different performance characteristics in terms of speaker breakup, and so on? Will power tube life be implicated in my choice of one impedance or another?  Anything else I can drive myself crazy worrying about despite it being either wholly out of my control, or simply a matter of individual taste?
Thanks in advance.

 

[Cagey]

Impedance matching is more a matter of sizing the load to the output for the greatest efficiency, not for any sonic characteristic. If you mismatch it, then you can have problems that you can hear until the amp or the speaker returns to Valhalla due to abuse. But, if the output and load are matched, you won't hear any difference from one pairing to another.

 

[mayfly]

You get more of a tonal difference changing how the speakers are wired.  For example, a Fender Twin has the two 8 ohm speakers wired in parallel for a load of 4 ohms.  A Vox AC30 has those 8 ohm speakers wired in series for a load of 16 ohms.  Amps aside, these cabinets sound very different.  The Vox is not as tight sounding.

 

[bagman67]

Thanks, guys.  I've been an open-backed combo kinda guy my whole life and this will be my first head/cab arrangement.  Should be fun!

 

[stratamania]

Just to reiterate if the amp output says 8ohms, set your speaker to that.
If it says 4ohms, the speaker also needs to be 4 ohms etc.