01-12-10: Kijanki
>With 4ohm you gain 15.7% of perceived loudness but loose almost 100% of damping factor (120 vs. 230).
1. FTC amplifier ratings are an over-reaction to the 1970s amplifier spec wars which have little bearing on actual music. A nice jazz recording has 18dB between average and peak power. FTC power ratings are five minutes of sine waves with 3dB crest factors. That's preceded by an hour of "preconditioning" with a 1KHz sine wave with average power 1/3 rated power (prior to 2000) which is actually the hard part (they reduced it to 1/8 power).
When you plan to use the amplifier for music instead of science experiments you should get peaks 3dB higher into a 4Ohm load than an 8Ohm load.
2. The damping factor is only relevant when you solder the output devices to the speaker terminals and use active cross overs. Keeping the active cross-overs but adding 8' of 12 gauge cable will drop the numbers to 83 and 42.
In the 4 Ohm case you'll have at worst a .2dB peak at the bass driver resonance which is generally believed to be inaudible so it doesn't matter.
Of course, with an odd order passive Butterworth electrical filter the damping factor will be just 2.4 at the cross-over point and even order Linkwitz-Riley filters will have a damping factor of 1. Moving into the stop band the damping factor will be less than one.
If you think damping factor is important you need to stop using passive cross-overs instead of worrying about amplifiers.
>With 4ohm you gain 15.7% of perceived loudness but loose almost 100% of damping factor (120 vs. 230).
1. FTC amplifier ratings are an over-reaction to the 1970s amplifier spec wars which have little bearing on actual music. A nice jazz recording has 18dB between average and peak power. FTC power ratings are five minutes of sine waves with 3dB crest factors. That's preceded by an hour of "preconditioning" with a 1KHz sine wave with average power 1/3 rated power (prior to 2000) which is actually the hard part (they reduced it to 1/8 power).
When you plan to use the amplifier for music instead of science experiments you should get peaks 3dB higher into a 4Ohm load than an 8Ohm load.
2. The damping factor is only relevant when you solder the output devices to the speaker terminals and use active cross overs. Keeping the active cross-overs but adding 8' of 12 gauge cable will drop the numbers to 83 and 42.
In the 4 Ohm case you'll have at worst a .2dB peak at the bass driver resonance which is generally believed to be inaudible so it doesn't matter.
Of course, with an odd order passive Butterworth electrical filter the damping factor will be just 2.4 at the cross-over point and even order Linkwitz-Riley filters will have a damping factor of 1. Moving into the stop band the damping factor will be less than one.
If you think damping factor is important you need to stop using passive cross-overs instead of worrying about amplifiers.