Yes, but you should ensure that the amplifier can handle the output impedance. If you are using different speakers for the front and rear channels in a home theatre (HT) system, mixing brands, power ratings, or impedance should not be a problem as long as the speakers and the amplifier are matched. Don't use a 4-ohm speaker with an amplifier channel that recommends a minimum load of 8 ohms. Both the left and right front speakers should match one another. The centre channel may be different, but should produce articulate and intelligible audio, as well as having the same timbre as the left and right speakers. Voices are mixed predominately into the centre channel in most recordings, but can be completely isolated in the centre channel in others. The left and right rear speakers should also match one another and the timbre of the remainder of the system. If you refer to adding additional speakers to an existing pair, wiring them in parallel, you must be aware of how the speaker load is affected. Two 8-ohm speakers in parallel, for example, produce a combined load of 4 ohms, while two 4-ohm speakers will have a 2 ohm load. An amplifier that is limited to an output load of 8 ohms or higher cannot be used in such a situation. The actual equation for calculating parallel loading is: 1/Load_total = 1/Load_1 + 1/Load_2 + 1/Load_3 + ... + 1/Load_N For example, if you have a 6-ohm and an 8-ohm speaker wired in parallel, the combined load is: 1/Load_Total = 1/6 + 1/8 Load_total = 3.4 ohms You should never run an amplifier into a load less than the rated minimum. This can cause excess current draw from the amplifier, increased distortion, and an increased risk of damaging the speaker output or the speakers themselves.