Speaker Load Question

[ehdwuld]

Just wonderin

if you have a 8 ohm speaker
but need a 16 ohm speaker

couldn't you just put a resistor in series with one of the leads
and make it appear to the amp as a 16 ohm load?



and what about the other way

say you needed a 4 ohm speaker
couldn't you put that same 8 ohm resistor
in parallel across the terminals and make it appear to be a 4 ohm load


isn't that, in effect, what the switch on the back of the amp is doing?

 

[IM4Tone]

Re: Speaker Load Question

Speaker impedance is not purely resistive, so to do what you question will give a safe situation, but poor tone.
Amps change their impedance output by alternating taps on the output transformer (I'm referring to tube amps), not by adding/subtracting a resistive load. The key here is impedance rather than resistance, although both are stated in ohms.
HTH

 

[kilphody]

Re: Speaker Load Question

The switch on the back of the amp is using different taps from the output tranny. Impedence is not resistance.

 

[crusty philtrum]

Re: Speaker Load Question

Resistance = DC, & not frequency-dependant

Impedance = AC, & frequency-dependant.

 

[PFDarkside]

Re: Speaker Load Question

To answer your first question, technically yes you could, but half of the power would be going to the resistor. That means something along the lines of a 50W resistor on a 100W amp. (Not to mention, that would severely change the inductor/resistor "network" that is a speaker, changing the tone and response). Notice that good attenuators are more than a simple resistor as well.

Others have covered the output transformer tap.

 

[misterwhizzy]

Re: Speaker Load Question

Regardless, this comes off as a loaded question to me.

 

[marvar]

Re: Speaker Load Question

I've tried it for sport- it sucks all the tone right outta your amp.
As said before a speaker is reactive, if you could put a meter between your amp and speakers, you see the load changing as you play.
but, always a minimum resistance as specified by the speaker.(4,8.16)

 

[ehdwuld]

Re: Speaker Load Question

well thank you all very much

clears that up

as you were