Usiing a resistor to increase impedance

[OldFarb]

I've heard that in theory you could add a 4 ohm resistor in series with a four ohm speaker to get and 8 ohm load. I'm really interested in increasing a 2 ohm speaker load to 8 or 10 or more.
Has anyone had experience with this, is it a good or bad idea? i assume it will have an effect on the sound of a guitar amp as well.
Thanks in advance.

[tubeswell]

I've heard that in theory you could add a 4 ohm resistor in series with a four ohm speaker to get and 8 ohm load. I'm really interested in increasing a 2 ohm speaker load to 8 or 10 or more.
Has anyone had experience with this, is it a good or bad idea? i assume it will have an effect on the sound of a guitar amp as well.
Thanks in advance.

If you add a resistor in series with the speaker, the resistor will use-up some of the current (and hence dissipate a proportion of the total available power), in proportion to the relative resistances of the resistor and the speaker. E.g.; take a typical 30W OT running 22 Volts 1.36A on the secondary - an 8R resistor + an 8R speaker in series = 16R in total, and the speaker will use .68A, and the other .68A will be burned up by the resistor. Therefore the speaker will only put out 15W of power, and the resistor would dissipate the remaining 15W (and would therefore need to be rated at least 15W otherwise it would burn).

Taking one of your examples, if you add a string of 3 x 2R resistors in series to your 2R speaker to make 8R in total, the speaker will use up 1/4 of the available power, and the other 3/4 of the power will be dissipated in the resistors (which will therefore need to be rated to withstand the power dissipation).

[OldFarb]

Thanks, that's what I wanted to know.

[Enzo]

This is not something you'd want to do.