Can someone explain the 8 ohms better than 16 ohms thing a bit?

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romanianreaper

romanianreaper

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I have been reading that people like setting the 5150-III at 8 ohms with a 16 ohms speaker cab. I had a few questions about that.

Number 1, why if it sound better, do they even make cabs at 16 ohms?

Number 2, is there any negative to doing this? Is it harder on the transformer, affect any other parts of the amp, etc?

I know it is probably not a big deal to do so but just trying to understand it.
 
I've never heard a lick of difference between 4, 8, or16 ohm configurations. I've run em all with countless amps and never experienced any significant change. I'm like that with tubes too though where most folks experience significant changes, I do not.
 
It doubles the reflected primary impedance of the output transformer. Doubles the load on the plates.
 
So a few things. IME 16 ohm speakers are brighter than 8 ohm speakers of the same model. Using an 8 ohm speaker out into a 16 ohm cab tends to sound slightly warmer than the 16 ohm speaker out into the same 16 ohm cab. Will that damage the amp? Most say no but people will argue til the end of time over it. Mesa says it's fine, but it may depend on how well the amp has been built.
 
My tech told me to set my amp to 8 ohms going into my 16 ohm 4x12 many years ago. It does sound a little warmer (better to me) that way but I often wondered if it stresses the amp as mine seems to run pretty hot. The PT gets hot anyway. My OT stays pretty cool.
 
Oversimplifying it a bit - the way i was told, it makes the amp work a bit harder, so you get a little bit more of the power amp goodness...
It's expecting to see 8 ohm resistance, but sees 16...
 
matttornado said:
My tech told me to set my amp to 8 ohms going into my 16 ohm 4x12 many years ago. It does sound a little warmer (better to me) that way but I often wondered if it stresses the amp as mine seems to run pretty hot. The PT gets hot anyway. My OT stays pretty cool.
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I assume the PT doesn't care what the cab impedance is, so I would think any issue with the PT is not related to an impedance mismatch.

I think supposedly running a lower impedance output to a higher impedance cab increases the risk of flyback voltages arcing the OT. Running the other way supposedly wears the tubes faster.

For some reason Fenders (and by extension probably Mesa) transformers seem to never fail. Marshall transformers seem to fail, but it's still seems rather rare.
 
If we are talking strictly speakers, not amp load, there is quite a difference in sound between a 16 ohm v30 and an 8 ohm v30. Enough that I preferred the 8 ohm as it was smoother and wasn’t as spiky sounding. Personal preference as some might prefer slightly brighter and tighter.
 
nigelpkay said:
If we are talking strictly speakers, not amp load, there is quite a difference in sound between a 16 ohm v30 and an 8 ohm v30. Enough that I preferred the 8 ohm as it was smoother and wasn’t as spiky sounding. Personal preference as some might prefer slightly brighter and tighter.
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Yeah, I have an admittedly small sample size, but I have quads of UK V30s in 8 and 16 ohm and quads of 6402-cone G12Ms in 8 and 16 ohms and there is a shockingly significant difference in the tone.

The 8 ohm speakers are much warmer/darker.
 
I believe it just all depends on what amp you are using and what tone you are after.
I went down the rabbit hole a few years ago.
I have 8 -4x12 cabs, 4 - 2x12 cabs and one 1x12 cab, all have different speakers some 8 and some 16 ohm.
I tend to like the 16 ohm speakers with my Bogners.
They just have a bit more high end bite to my ears ?
I will say I have never been a fan of gt75 speakers.
However on a carvin legacy head I had they sounded best ?
They were 16 ohm running on 8.
The best way to know what you like is to try different things.
 
Fordman65 said:
Personally I think stuff like this is minutia. Plug in so you don't blow the amp up and have fun. Too many variables like this to get bogged down in. Guitar lacquer this, capacitor that. Tube this, special transformer that. All seems like excuses to buy more and play less. Been there, done that.
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100%
 
I've noticed big differences in vintage and cathode biased amps, but very few differences in modern high gain amps as far as both mismatches and different ohm ratings.
 
thegame said:
In general, older gear is much more revealing to differences such as that, as well as different guitars, cables, buffer circuits, tubes, incoming voltages, etc.
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I agree with Dan, Gary….In general, running a 4 or 8 out into a 16 ohm cab will lower the headroom a bit; while the tone gets slightly darker/warmer and a bit thicker.
Not super obvious but it’s there.
 
Fordman65 said:
Personally I think stuff like this is minutia. Plug in so you don't blow the amp up and have fun. Too many variables like this to get bogged down in. Guitar lacquer this, capacitor that. Tube this, special transformer that. All seems like excuses to buy more and play less. Been there, done that.
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I definitely dislike the idea of special mojo or unobtainium gear etc.

It's easy enough to try a mismatch to see if you like it. The 8- vs 16-ohm speaker to me is a noticeable difference, but I can mostly compensate with the amp's tone controls.

If you hate a 16-ohm speaker's character, you won't suddenly love the 8-ohm version. But if you like, say, the warm midrange and biting treble of a 16-ohm G12M but thought it had just a bit too much high end presence/sizzle that the amp's presence knob couldnt quite tame: then the 8-ohm version might be worth a shot. That type of thing.
 
Only taking the speakers into account, yes there are some minor difference in the sound. Whether you can hear that difference or not is another question. Personally I can't hear shit of difference between 8 & 16 ohm speakers. I'd suspect anyone who can would be able to compensated for it by adjusting the EQ knobs a millimeter or two.

If you're getting at an ohm mismatch between amp and speaker, there's a minor difference in sound there too. I watched an interview with Steven Fryette about this not too long ago. I forget exactly how and which way it goes but there's a slight effect on the emphasis of midrange frequencies. He talked about how the whole magic tone mismatch thing stems from the beginning of guitar amplification when all this stuff was limited. You only had the option of a mismatch. Somewhere along the line a famous guitarist was playing through a mismatched amp and cab which sounded really good. So someone decided that this was where that magic tone was coming from and hence the legend was born.
Again if you can hear the difference and achieve that special sound more power to you. Again I can't hear much shit of difference between the two, and any difference I do hear is negligible.

The other thing that goes along with the whole ohm mismatch thing is will it fry the amp. This will be debated to the end of time with hardcore proponents for either side. From the same interview; his assessment was as long as you have a solid transformer and don't go in either direction more than a factor of 2 all will be fine. So, 8 ohm head to 16 ohm cab or 16 ohm head to 8 ohm cab is fine either way. The frying the amp thing he says came from people running 100 watt amps at full volume for 8 hours straight. The speaker would melt down under those conditions which resulted in a zero load on the transformer. The zero load would be the cause of the amp frying, not the mismatch. The same thing would happen even if the amp and cab were matched. He said the only negative (or positive depending on the way the mismatch is) was how hard the tubes were being worked.
 
Ok, so which is harder on tubes?
Amp at 8ohm into 16 ohm cab… or amp at 16ohm into 8 ohm cab?
 
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