The Final Word on Impedance Mismatching

[mrid]

OK, I know it's "a bad thing" to put a high load on a low load speaker(s), i.e a 16 ohm load going into a 4 ohm cab, but is the reverse bad as well? IMO, no, but I've heard several consevative types say that the impedences must be matched. I'd like to play around with the different settings on my amp (4-8-16) to see what kinds of tones I get with a 16 ohm cab. I usually just leave it on 8 ohms, just to be safe.

[dystrust]

Mismatching a high impedance will not damage your amp, however it will change your tone. You'll get a lot of extra distortion due to a mismatch; 8 ohms into a 16 ohm cab sounds pretty good, but any larger mismatch is almost too mushy to use.

[Gearjoneser]

A good word is that they should be equal, so the amp is performing where it's supposed to. Anything else is just stressing components, needlessly.

The final word is they should never be mismatched by more than
4 ohms. You're risking a $300 transformer replacement, if you don't at least follow that guideline.

[Kent S.]

The match is to ensure the maximum power, with the minimal strain on the power amp ... that being said going from a 4ohm output Z into an 8ohm speaker load isn't going to damage anything, now, the reverse if the amp is built reasonably well won't hurt anything either ... as long as you are not running the amp wide open, about half way up would probably be okay.
Running say a Fender Super reverb (2ohms output Z) into say a 16ohm cabinet and running it wide open, well you might cook something ... do to the amp not being able to deliver all of it's power (that means the rest is converted to heat, and some gets reflected back into the output transformer). If you ran a 16ohm output Z marshall into a 4 ohm cabinet at full bore, then you'd probably cook something before the set was over with. It really depends on the amp, and how it's designed. Mismatching loads at lower levels generally won't hurt anything as the power output requested by the load is still within the amps ability to produce supply it. if you've got a loud amp, and you are running at half or under, then you should be fine, to be safe though, *I* would run it about a third or lower. Either way some cooling fans go a long way towards added protection. I'm betting you won't be turning your amp past the half way point anyway, in almost any settings.
The answer is that you can do it, some amps put up with it better than others, just do it carefully and at lower volumes, the lower the load value (4 <8) then greater the load, because it wants to draw more power from the amp, so the amp works harder; the higher the load value (8>4) the less the load because it doesn't draw as much power, but the trade off is the extra resistance creates more heat ... also there is something called reflected power in which the output tranformer can not transfer all of it power ... it kinda creates a situation where the secondary can't transfer of all of it's power to the load, while the primary is still trying to induce more into it, and the amp is trying to shove more into the primary ... that tends to generate quite a bit of heat, and heat is the enemy of all electronics period.
That's kinda a half technical explanation/illustration of it, but I think you get the point, just do it carefully, and you should have no problems ... Boogs have been doing it for years, the original ext.speaker jack on the black and silver faced fenders were simple a parallel off the output jack, there was no internal correction on the amp ... so that was a mismatch into a lower load ... but most people didn't run them wide open, so they didn't have many problems (of course I don't think most people actually even used those jacks at all ).

[Gearjoneser]

Besides risking the transformer, due to heat, having an impedence mismatch is especially hard on tubes, cause they're less resilient than the tranny.

[mrid]

http://www.mrgearhead.net/faq/pdf/gu...ToneMaster.pdf

The manual almost treats the impedance switch like a tone switch! Then again, this amp has the biggest OT I've EVER seen! Like, 90% of the weight of this thing is output transformer.

[Young Angus]

ummmm i might have made a big mistake here but up until recently i had the 16ohm output going into my 8ohm cab??

I thought that type of mismatch was okay, or is it the other way around and should i have my amp checked for any damage i might have caused?

[kevlar3000]

Originally posted by Young Angus
ummmm i might have made a big mistake here but up until recently i had the 16ohm output going into my 8ohm cab??

I thought that type of mismatch was okay, or is it the other way around and should i have my amp checked for any damage i might have caused?

Swap that puppy around.

Back in the day folks used to juice their Marshalls by lowering the ohm selector on the amp into the higher ohm cab.

[Kent S.]

Re: The Final Word on Impedance Mismatching

http://www.mrgearhead.net/faq/pdf/gu...ToneMaster.pdf

The manual almost treats the impedance switch like a tone switch! Then again, this amp has the biggest OT I've EVER seen! Like, 90% of the weight of this thing is output transformer.

Hence, the boogs are built to take it, they are built from an overkill perspective on just about every componenet level ... you should be fine with those at normal levels.