Combiing 4 ohm and 8 ohm speakers

4 ohm speakers do put a heaver load on the amplifier than do 8 ohm speakers. Some receivers have a switch for use when you have lower impedance speakers. It reduces the output voltage so the output drivers don't overheat. This also limits the maximum output volume. This lower setting can be used for both 4 and 8 ohm speakers.


If you calibrate the sound levels, then mixing speakers that have different impedences and efficiencies shouldn't matter.


However, mixing speakers of different types, regardless of the impedance, can cause "problems" just because they sound different. Ideally you should have identical speakers all around. That way someone's voice (or other source) will sound the same no matter which channel it comes from.


You can get an impression of how well timbre matched your speakers are by carefully listening to the pink noise that your receiver uses for calibrating each channel. If the different speakers sound significantly different, you might want to consider replacing some of them.


The home theater setup DVDs ("Avia" and "Video Essentials") also include tests with the same person's voice coming from each of the speakers.


I hope this clarifies things a little.

Patrick: You haven't mentioned what Receiver you are using and whether or not it is a Dolby Digital or older ProLogic model. If you are using DD, you are much better off having the same speakers front, rear and center. If you are not, they don't need to be equal. This is because ProLogic doesn't have full power to the rear or center. It doesn't even have stereo in the rear. Depending on the Receiver you are using, 4 ohm speakers are not appropriate for many brands which prefer an 8 ohm speaker load. The fact that you are using inefficient speakers on the front, means that you will use more of the amps output to produce an adequate level of sound. Your Receiver uses a separate power amp for the rear and for the center channel. Because of the difference in impedance and efficiency between your front and rear speakers, it will be necessary for you to pay closer attention to balancing each channel.