Replacing an 8ohms speaker with 16ohms in my combo - will the amp fry? good/bad ????

[tildeslash]

I like to replace in my tube combo an 8ohm speaker with a 16 ohm Celestion Blue. Am I asking for trouble?

[Dannc6]

I'd run a search - a lot of good insight out there already

[HandOfTheHost]

I'd run a search - a lot of good insight out there already

+1 And yes, that's asking for trouble.

[SatelliteAmps]

Depends on the combo. Some have switchable impedances, some don't. Those that don't would be running the risk of overheating an output transformer.

[Cottage]

It'll sound like shite! Break up much earlier and hardly any overhead at all. I tried it in a Pro Jr. Ended up going back to the 8 ohm.

[pgissi]

It'll sound like shite! Break up much earlier and hardly any overhead at all. I tried it in a Pro Jr. Ended up going back to the 8 ohm.



1) You really cant say what it will sound like, depends on the amp,
speaker and musical/tonal flavor your going for, most amps can handle
and this being a 100% mismatch your within the safety margin. If using a low wattage amp below 30 watts or less, it may not yield a good tone but it depends on yoru needs and tastes.

2) Tonally you may like it more than the stock 8ohm coupling, you just
have to try. Yes tone will brown faster with slightly less headroom,
response flattened out in the lows and highs. You should find the
high end is smoother as the upper end response is reduced some
which in this day of high gain amps with plenty of high end sizzle
and bright speakers can reduce fizziness which gives you more clarity as the fizziness in minimized which when apparent masks your clarity

3) Power will be reduced by 1/3rd give or take, this can be a postive
change since now you can run the amp harder get more from its
eq and master etc.

Once again depends on the amp and a generalized explanation of what is happening is simply that an imp mismatch using a lower than rated for stock load (4ohm speaker with 8 ohm output) will work the output tubes
harder with the opposite mismatch using a higher than stock load, works the Output tubes less. Whether this is what you want is too subjective too determine.

The warning comes here, higher impedances result in a higher than normal reflected impedance to the OT but with a 100% mismatch your within the safety margin for the majority of tube amps, most amps can handle.

Using loads over 16ohms or anything over a 100% mismatch is never recomended.

Generally the OT will run hotter with any Imp mismatch but once again using a lower than stock load, the tubes run hotter and will not last as long.

Have been doing this for years with my 30watt Rivera R30, not a boutique amp by any means but well built although with a small OT and loaded PCB. I went from using it as a 1x12 combo stock 8ohm to using it with a 2x12 cab @ 16ohms with the speakers wired in series.

The tone was transformed dramatically for both channels and the 2 most influential factors are the imp mismatch using a 16ohm load with the stock 8ohm output and series speaker wiring. Riveras manual states this mismatch is acceptable and is the case with many amps.

-Buzziness was eliminated on both channels
-Highs are creamier
-Tone Browns faster and is harmonically richer and more complex but yet
retains good interaction with guitar pot to roll back to a clean tone
-power was reduced which allows me to run the master vol higher and get
more output tube in the tone
-output response curve was altered in a positive way to where the tone
regardless of guitar sits in a mix better probably as the mids became
slightly more emphasized in a broad bandwidth manner but subtlely and
due to the de-emphasized highs and lows, early browning

This is just what my ears tell me as the amp is slightly darker with this mismatch which I counter with the amps EQ and once again this is a 30 watt amp so the loss of headroom was not dramatic and in fact was based on the idea of running a low wattage amp hard for great OD at lower volume. Using a mismatch moves the tone in that direction

I reasoned I need to throw away some efficiency in the output to maybe introduce some OD character that was not there stock and it ended up being a good thing, in fact I dont use the amp in any other way.

Bottom line I knew going in the result was impossible to predict and only had a general idea of what I may hear and that it may not be to my liking but was pleased I took the chance and it was just something I tried to accomplish these 2 things-

-throw away some output efficiency to get the amp singing at lower
volume since even with this 30watt amp, getting a singing OD tone to the
place I wanted it, it was still too loud and thin stock
-alter the output response curve subtlely to see if it was useful and it
seems now and it was pure chance, the output curve is more pleasing
across the output range, I dont find myslef boosting things to get them
to jump out as much, its just there now


I have posted much about this here at TGP and began using this to solve a problematic amp and its less than inspiring tone and began reading here and elsewhere that its not as dangerous or uncommon than you think.

Its a way to tweak your tone without the use of tone controls and in an unpredicatable manner using the complex interaction that is the OT to its load at "X" impedance with "X" speakers wired in "X" style.

In the end its unconventional and sometimes pays off

[drbob1]

The "output impedance" of an amp is a bit of an oversimplification. The output transformer couples the speaker (2-16 ohms) with the tubes (which want to see thousands of ohms) but the impedance of the speaker is highly frequency dependent, and most amp makers set the reflected impedance somewhere in the vague appropriate range for the type of tubes specified. Consequently, only your ears and experience are going to tell you what works and what's safe. As a rule of thumb you can double or 1/2 the impedance your amp expects and not blow anything up, but some amps will tolerate it better than others. Most modern amps have very heavy OTs and will tolerate it fine. Most Fenders are good. Voxes-I probably wouldn't go higher, might go lower. Silvertones and Valco amps, it's a gamble. Traynor and Garnet-no problem. And so on....