What happens if you hook 4 ohm speakers to 8 ohm tap on tube amp?
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mhardy6647
Lunatic Member
No harm is likely to befall your amplifier.
Kegger
R.I.P. 1/12/1966 - 6/1/2017
What he said.
It makes your output tranmsformer primary impedance half of what is was stated for.
In other words if you had a 5000ohm primary with an 8ohm rated secondary but your
using 4ohm speakers then your primary becomes 2500ohm, nothing that would hurt it
but it could sound worse, make less power or could sound better an make more power,
any of the previous combinations, depends on tubes, voltages, currents and speakers.
It makes your output tranmsformer primary impedance half of what is was stated for.
In other words if you had a 5000ohm primary with an 8ohm rated secondary but your
using 4ohm speakers then your primary becomes 2500ohm, nothing that would hurt it
but it could sound worse, make less power or could sound better an make more power,
any of the previous combinations, depends on tubes, voltages, currents and speakers.
Kegger
R.I.P. 1/12/1966 - 6/1/2017
UHMM......NO!
All your measuring is the DC resistance of the woofer.
That can give you an idea of the woofers lmpedance, as generally what is considered to
be an 8ohm woofer will have say 5 -7 ohms DC resistance, but the coil in the speaker is
generally in series with the woofers as well which would make your readings even higher.
An 8Ohm speaker is not 8Ohm measured with a meter, it varies with frequency and it's an
AC resistance/impedance that goes up an down at the different frequencies, you really do
need to see the impedance chart of the entire speaker to see what it is.
The PartsExpress woofer tester can measure your whole speaker an give you the graph.
All your measuring is the DC resistance of the woofer.
That can give you an idea of the woofers lmpedance, as generally what is considered to
be an 8ohm woofer will have say 5 -7 ohms DC resistance, but the coil in the speaker is
generally in series with the woofers as well which would make your readings even higher.
An 8Ohm speaker is not 8Ohm measured with a meter, it varies with frequency and it's an
AC resistance/impedance that goes up an down at the different frequencies, you really do
need to see the impedance chart of the entire speaker to see what it is.
The PartsExpress woofer tester can measure your whole speaker an give you the graph.
Last edited:
rob29
Active Member
If you wanted to make your 2 4ohm speakers into an 8ohm, you would wire them in series meaning positive output to Speaker 1 positive input. Speaker 1 negative input to Speaker 2 positive input. Speaker 2 negative input to negative output on your source.
But you would be feeding the same signal into both speakers and only using your source unit as a mono off of one speaker output.
But you would be feeding the same signal into both speakers and only using your source unit as a mono off of one speaker output.
mhardy6647
Lunatic Member
A quick and pretty good guide to measuring impedance (as a gateway to DIY Thiele-Small parameter measurement for a loudspeaker driver, which is what the woofer tester is intended for). The impedance of a whole speaker system can also be measured, but you'll "see" the whole system, crossover networks and all.
http://sound.westhost.com/tsp.htm
The nominal impedance is usually that measured in the impedance curve valley above Fs, typically in the vicinity of 100 to 200 Hz (depending on the speaker, of course).
The impedance curve of a single driver (woofer) typically looks more or less like this...
http://sound.westhost.com/tsp.htm
The nominal impedance is usually that measured in the impedance curve valley above Fs, typically in the vicinity of 100 to 200 Hz (depending on the speaker, of course).
The impedance curve of a single driver (woofer) typically looks more or less like this...
