Which Receivers Are Capable of Driving 4 Ohm Speakers
Most receivers are designed to handle 8 ohm speakers. Likewise, most household speakers on the market today are 8 ohm speakers. However, there are plenty of 4 ohm speakers out there ranging from high-end reference system type speakers, to speakers that someone has just had for a long time and they happen to be 4 ohm speakers. The range of reasons for wanting to use 4 ohm speakers varies similarly from someone not wanting to buy new speakers and just wants to use the ones they have, to someone who has carefully evaluated several speakers and the best ones for their situation happen to be 4 ohm speakers.
The main issue with using 4 ohm speakers with a receiver designed for 8 ohm speakers is that doing so increases the current used to drive the speaker. Make no mistake; most good receivers have plenty of power to be able to drive 4 ohm speakers. What they do not have, is a way to deal with the additional heat that results from doing so. Most customers don’t want a fan making noise inside their receiver, which limits the options for dissipating the heat that results from driving 4 ohm speakers.
As a result, most receivers cannot handle 4 ohm speakers. The most basic way to tell if a receiver can handle 4 ohm speakers is price. The cheaper the receiver, the less likely it is that it is rated to push 4 ohm speakers. If you didn’t spend at least $1,000 (new) for your receiver, then the answer is most likely, “No my receiver cannot handle 4 ohm speakers."
For a more definitive answer, check your receiver’s specifications. The easiest place to find them is in the manual. Also, if your receiver is still on the market, many home audio theatre retailers publish specs on their websites. Name brand receivers have manufacturer websites that allow for both viewing the specifications and downloading the manuals. Check for “Speaker Impedance" or something similar.
For example, the Onkyo TX-SR507 has a speaker impedance rating of 6 ohms – 16 ohms, which means that this receiver cannot handle 4 ohm speakers.
Lastly, some receivers come with a switch which allows the end user to switch from 8 ohm to 4 ohm or in some cases, 6 ohm speaker resistance settings. In this case, the inclusion of such a switch means that the receiver can be used safely to power 4 ohm speakers. However, several experts have stated that such a switch merely reduces the maximum power available to run 4 ohm speakers to a lower level where the receiver is capable of handling the heat.
In the end, even most audiophiles may be better served by matching their good quality speakers to the capabilities of their receiver, instead of the other way around.