In theory, an amp rated at 128 wpc, will deliver a sound level of 110 dB at 1 meter when paired with 89 dB speakers. However, it will only deliver about 104 dB at 3 meters...which is where most of us listen to our music.
Also, at about 60% of the amps rated power, distortion will start to creep in. Consequently, we must reduce the theoretical output of the amp by another 3 dB if we want clean , undistorted sound.
Conclusion = Not accounting for the many other factors which may further reduce the sound level (listening room acoustics, age/condition of components, headroom to cover peak dynamics, etc., etc.), we will be lucky if our 128 watt amp delivers 101 dB of "clean" power at 3 meters.
HG
Also, at about 60% of the amps rated power, distortion will start to creep in. Consequently, we must reduce the theoretical output of the amp by another 3 dB if we want clean , undistorted sound.
Conclusion = Not accounting for the many other factors which may further reduce the sound level (listening room acoustics, age/condition of components, headroom to cover peak dynamics, etc., etc.), we will be lucky if our 128 watt amp delivers 101 dB of "clean" power at 3 meters.
HG