Ok, I admit it. I couldn’t resist the allure of “amp damp” when what I mean is the more mundane amplifier damping factor.
I still get asked what damping factor means and because I am also going to start talking about the differences in the new Power Plants and the older ones I thought this might be a good place to start.
The amplifier’s damping factor is a number that tells us how much control the amp exerts over the loudspeaker. The higher the number the greater the control.
Why would speakers need to be controlled? There are several reasons. First, because they are reactive. But more importantly, a woofer’s heavy mass needs taming. Let’s focus on the latter.
What we demand out of a woofer is obedience. Go where you’re told, when you’re told, and go no further. Unfortunately, the bigger and heavier the woofer the less obedient they are. Below about 150Hz woofers get unruly. They don’t stop their motion when ordered and generally act as anarchists. An amplifier that’s in control can fix that.
The key ingredient of loudspeaker control is amplifier output impedance. The lower the impedance the greater the control.
Here’s how damping factor is calculated. If we divide the speaker impedance (let’s say 4Ω) by the amplifier impedance plus the wire impedance, we get the damping factor. So, if the amp’s output impedance is 0.005Ω and the wire is 0.1Ω then we get 0.105Ω into 4Ω which then equals 38 (4÷0.105=38). Now, if you were to just use the amp’s output impedance of 0.005Ω and the speaker’s 4Ω you’d have a whopping high damping factor of 800. (So the wire impedance means a lot for low frequency sound).
Tomorrow we’ll dig a bit deeper.
Oh, and BTW. If you hadn’t noticed we finally acquired the number 1-800-PSAUDIO. Been a long time coming and a lot of wangling and money changing hands but it’s an easy one to remember.