Since 16 ohm loads demand less power than 8 or 4, it seems like any amp that could do 8 ohms could deliver at least as much power into 16. Are there any other factors I’m not aware of that would affect this?
As a related question: If a speaker varies between 4 and 16 ohms over the frequency spectrum, would wny amp that can deliver sufficient power at 4 ohm be appropriate? What if it’s a tube amp? Would it need to have an autoformer output?
As a related question: If a speaker varies between 4 and 16 ohms over the frequency spectrum, would wny amp that can deliver sufficient power at 4 ohm be appropriate? What if it’s a tube amp? Would it need to have an autoformer output?
Aren’t tube amps without output transformers even fussier about load impedance?
They have limited output current, and are best with high impedance speakers.
What is your actual problem?
You keep changing focus.
You should have stated this very specific case in the original question, instead of making a very generic one and after answers: "oh! but that´s not what I´m interested in".
I had two related questions:
1. Does a 16 amp load present a challenge to amplifiers as a 4 ohm load does? (both being deviations from the "standard" 8 ohms)
2. What about for tube amplifiers?
The only answer I got was:
I was confused by this, because (unless I am mistake) all tube amps either have an output transformer or no output transformer, and I know that OTL tube amps are *extremely* fussy about load impedance.
Mark Johnson seemed to be saying that tube amps with output transformers are fussy about the impedance, *but some other type aren't* (implication added)
If a amp is rated for 100 watts @ 8 ohms and you use a 16 ohm speaker you will only get 50 watts @ 16 ohms.
Its also about what max volts the amp will put out too.
I used to run a mobile disco off 16 ohm speakers.
I used 4 in parallel to get 4 ohms.
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Oh right, because going down to 4 ohms increases power (if available), so going up decreases.
And then about voltage; So if I need 100w and my amp will do 200w at 8 ohm, it’s no guarantee that it can do 100w at 16 ohm because it may become voltage limited.
Thank you! A simple answer, but it all clicked for me.
And then about voltage; So if I need 100w and my amp will do 200w at 8 ohm, it’s no guarantee that it can do 100w at 16 ohm because it may become voltage limited.
Thank you! A simple answer, but it all clicked for me.
And while a 4 ohm load pulls more current from an amp than a 16 ohm load, it isn't like that is a problem. AN amp is rated to 4 ohms or it is not. Assuming it is properly engineered, an amp rated for 4 ohms will be happy with 4 ohm loads. Higher impedance loads will be less demanding, but that doesn't make 4 ohms a problem.
As stated, it requires more voltage but less current to drive the same power into 16 ohms as it does 8 ohms. For a direct coupled, linear solid state amplifier, this presents no hazard; the only drawback is that less power will be delivered to a 16 ohm load.
I went through a period where I reverse engineered a whole lot of audio equipment out of curiosity. It should come as no surprise that not all amplifiers are created equal. Anyway, I noticed a trend in some mid 80s to late 90s receivers (like Pioneer) that had "A,B,A+B" speaker selector switches. Many of these switches put the speakers in series in "A+B" mode, and the amplifier voltages were scaled accordingly. Some of these units could deliver close to rated power into 16 ohm loads. So there's exceptions to the rule.
Digital amplifiers (which are often designed to drive very low impedance loads) can be affected by load impedance. Because they typically have aliasing filters on their output (in series/parallel with the speakers), their frequency response can be affected by load impedance.
Finally, any amplifier with an output transformer (not just tubes) can be affected by load impedance. Transformers can do some nasty things which result in the output device's SOA being exceeded, typically by voltage spikes.
I went through a period where I reverse engineered a whole lot of audio equipment out of curiosity. It should come as no surprise that not all amplifiers are created equal. Anyway, I noticed a trend in some mid 80s to late 90s receivers (like Pioneer) that had "A,B,A+B" speaker selector switches. Many of these switches put the speakers in series in "A+B" mode, and the amplifier voltages were scaled accordingly. Some of these units could deliver close to rated power into 16 ohm loads. So there's exceptions to the rule.
Digital amplifiers (which are often designed to drive very low impedance loads) can be affected by load impedance. Because they typically have aliasing filters on their output (in series/parallel with the speakers), their frequency response can be affected by load impedance.
Finally, any amplifier with an output transformer (not just tubes) can be affected by load impedance. Transformers can do some nasty things which result in the output device's SOA being exceeded, typically by voltage spikes.
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Doubling the load impedance on a transformer coupled amp isn’t going to produce voltage spikes that are particularly dangerous. Not like leaving it *unloaded* would. Tube amps dislike it because if the plate current is too low when the plate voltage falls at the top of each cycle, the SCREEN current goes up. Often WAY up. Solid state amps with an OPT don’t have screens to overload.