Tonal/Volume differences between 16ohm and 8ohm cabs??

  • Thread starter Thread starter Stramm8
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There are a lot of misconceptions about impedance matching with tube amps. I will not venture in too deep, but I will say using that the higher impedance cab is the only thing that is OK applies to solid state amps, and not tube amps.

Since speakers are reactive they are only 8, or 16 ohms at one frequency, a lot of speaker manufacturers provide the impedance curves which show how much it changes over the usable range. Tube power amps put out the optimal power over a certain impedance range if you change that range you will loose power at one end of the range, and have either a darker, or brighter tone.

I am not going to get into much of the discussions on damage to OTs etc I will just say that unless you are running it at very high levels a well designed amp will have no problems. I have never found an amp that sounds better (to me) using a mismatch in the impedance selector.

I am sure that some people who know a bit more theory on this can provide a better explanation.
 
GuitarGuyLP":3p8mp1ev said:
There are a lot of misconceptions about impedance matching with tube amps. I will not venture in too deep, but I will say using that the higher impedance cab is the only thing that is OK applies to solid state amps, and not tube amps.

Since speakers are reactive they are only 8, or 16 ohms at one frequency, a lot of speaker manufacturers provide the impedance curves which show how much it changes over the usable range. Tube power amps put out the optimal power over a certain impedance range if you change that range you will loose power at one end of the range, and have either a darker, or brighter tone.

I am not going to get into much of the discussions on damage to OTs etc I will just say that unless you are running it at very high levels a well designed amp will have no problems. I have never found an amp that sounds better (to me) using a mismatch in the impedance selector.

I am sure that some people who know a bit more theory on this can provide a better explanation.
Click to expand...

This was my understanding as well. Something about flyback voltage. There's some interesting discussion on TGP about it.
 
From what I understand flyback voltage is a different thing, and is more likely to happen when there is an unexpected change in impedance like a speaker connector coming off, a speaker cable being yanked out while playing etc.

Bottom line this is a bit of a complicated issue, and I have even heard some misinformation coming from amp builders. I am sure that it is not really needed in designing a power section since you are not assuming mismatches etc. I did a bunch of research on it a while back, and ended up crosseyed trying to find what info is right, and wrong. A lot of people hear one view once, and believe it like it is the gospel. And others hear it from then and on, and on. One very good source is http://www.londonpower.com/faq.htm his books are great too!!!
 
Back to the OP, I find 16ohm cabs to sound the best for reasons I am not entirely sure about... Just seems when my amp is pushing a 16ohm cab, it's nice and full. Dropping down to an 8ohm cab with the amp changed to 8ohm, it's subtle but it's there...maybe a bit stiffer sounding.

I can't recall 4ohm experience. I'm sure I've had it, but I can't say for sure. Just seems to me, things get stiffer sounding when I worked my way down from a 16ohm cab. YMMV.
 
Its not so much the different impedance of the cab as it is how the transformer is reacting to it.
16 ohm loads are using the entire transformer windings.
Honestly though, I prefer the sound of 8 ohm, it's not as shrill and has a nice warmth when the volume is higher.
 
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