Matching amplifier to speaker impedence
Posted: Tue Jul 28, 2009 11:58 pm
Hi all, can anyone tell me a way of converting amps that have rated output impedence of 4 or 8 ohms to speakers rated at 3 or 15 ohms.
Thanks
Thanks
Hi
Provided the impedance of the speakers is equal to or greater than the minimum rated impedance of the amplifier you won't have a problem. However, the output power of the amplifier will be less at higher impedances. One way to adjusting the impedance is to connect a number of speakers in series or parallel, or even some combination of the two. The formulae for series / parallel impedance is the same as for resistance (see the calculators menu at the top of the page).
E.g. 2 x 3 ohm speakers in series would present a load of 6 ohms to the amplifier
or 2 x 15 ohm speakers in parallel would give a 7.5 ohm load, both suitable for the amplifier.
How powerful are the speakers - matching impedances becomes more important in larger systems, where the difference in output power for greater impedances is more substantial. At the other end of the scale, for small speakers less than 1 watt (e.g. intruder alarms or small stereos) where quality isn't so important you could put a suitable resistor in series with the speaker, e.g a 1 ohm resistor with the 3 ohm speaker to give 4 ohms, suitable for the amplifier.
Just to re-iterate, ensure the impedance of the speaker (or combination of speakers) is not less than the specified minimum impedance of the amplifier.