The damping factor of an amplifier is important for tidal lows. So the higher the damping factor the better? Well, kind of. I wonder if there's a name for urban legends that live on the web. Suggestions are welcomed for there are many urban legends on the web about audio. One such legend is about the damping factor of an amplifier. As with most urban legends, it started out with a bit of truth, but is exaggerated every time it is passed on to the next person. Yes, the damping factor is an indicator for the control an amplifier has over loudspeakers base behavior. And yes, a high damping factor is better than a low one. But the amplifier with the highest damping factor does not necessarily provide the best base. So what is a damping factor? The damping factor is calculated by simply dividing the loudspeaker impedance by the output impedance or the amplifier. The impedance is the resistance for alternating current like audio signals. Let's make it more graphical. This is a simplified diagram of an amplifier and speaker setup. I have divided the amplifier into a voltage source and the output impedance. The loudspeaker has its own impedance. Now let's name the amplifiers output impedance ZA and the loudspeaker impedance ZL. The formula is damping factor equals ZA divided by ZL. We can now calculate the damping factor. Let's do some examples. If the output impedance is one ohm and the speaker impedance is eight ohms, the damping factor is eight. If the output impedance is 0.1 ohm and the speaker impedance stays eight ohm, the damping factor is 80. And if the output impedance is 0.01 ohm, we get a damping factor of 800. We can make the same calculations for use with four ohm speakers and you'll see the damping factor is half of that of an eight ohm speaker. The damping factor of an amp is usually specified for eight ohm speakers. When the voltage source generates a voltage, a current flows via the loudspeaker cable through the loudspeakers back to the negative of the voltage source. Sound is a variation in sound pressure and when converted to an electrical signal, that signal will vary in voltage and thus will alternate between positive and negative. This alternating current generates an alternating magnetic field in the voice coil that will push the loudspeaker cone in and out. The speaker is built using a tubular permanent magnet that is terminated by N-plates and is mounted on a basket that supports the cone. In this drawing, I cut the tubular magnet in half. The N-plates move the magnetic poles to a more purposeful position. The voice coil is glued to a cylinder made of cardboard that is situated inside the N-plates. The basket holds the outer rim of the cone while the inner rim of the cone is glued to the voice coil assembly. So in essence, the speaker is a coil moving inside a magnetic field. There's an intended movement as a result of the current from the amplifier, but there also is an unintended movement due to storage of kinetic energy in the cone assembly. Formas emotion needs some time to halt again, especially at the resonance frequency of the loudspeaker. The construction of a moving coil in a permanent magnet is not only used for loudspeakers. You must have heard of the moving coil cartridge for turn tables. It generates minute voltages as a result of a coil mounted at the end of a cantilever and moved by the stylus, but also the bicycle dynamo uses this principle as do modern windmills. So a loudspeaker must also be able to generate voltages. And it is. On the desk you see a more than short loudspeaker I use in my setup 3. The roof is connected to the oscilloscope and when I move the cone by tapping on it, you will see a voltage on the scope. So whenever the cone makes a movement as a reaction on the musical signal, a voltage is generated by the speaker. This causes a current towards the amplifier speaker terminals, which can cause problems in amplifiers since most amplifiers today use negative feedback. Here the output of the power amplifier is fed back to be compared with the input signal of the amp. The difference is of course distortion and can be compensated for by adding the inverse signal to the input signal. The problem is that the voltage generated by the speaker is added to the feedback signal having the amplifier correct for errors that were never done. When the output impedance is very low, say 0.1 ohm, the speaker sees almost a short circuit, so that voltage is almost completely short-circuited. So that's clear then. We want an amplifier with a very low output impedance and thus a very high damping factor, right? Well, not really. First, it is generally accepted that a damping factor higher than 20 does not bring further improvements. Second, an extremely low output impedance is often achieved by high negative feedback ratios, which not always lead to a better sounding amplifier. And there are probably exceptions as there always are in audio. Tube amps have relatively high output impedances due to the output transformer used, but they often use low negative feedback ratios. Some even don't use negative feedback at all, and thus are less or even not sensitive to the voltage generated by the loudspeakers. There's another factor that influences the control an amplifier has over the speaker. The ability to deliver current. This has to do with the quality of the power supply used and the impedance of the loudspeaker. If a loudspeaker behaves like an atom resistor, it will not be a difficult low to the amplifier, but if the speaker has a low impedance at a given frequency and a very poor phase behavior at that point, ship loads of current are needed to keep in control. That is why the TrueBrewBox cobalt DA amplifier I reviewed last week has the option of a double power supply. And that is why I mentioned the demo on the BMW 802 Nautilus speakers that go down to three ohms with zero degree phase angle at 100 hertz and do four ohms and minus 55 degree phase angle at 60 hertz. And there are a lot more factors than defined audio quality of the amp. In the end, the only way to evaluate the audio quality is listening under controlled conditions using loudspeakers that you are going to use. My audio physics corpio loudspeakers in set up one are an easy load. Those Nautiluses aren't. So I can use my two times 15-watt audio note solo single ended tube amplifier on the corpios, but absolutely not on the Nautiluses. Horses or courses is the expression if I'm right. I fully understand that people seek simple to understand figures to select gear, but it's making life a lot harder than listening to a product over your own high-fi. Make sure you only change the product you want to judge. Never change more than one product at a time unless it is clear that the resulting combination would not work. Listen for a longer time. Don't switch from one situation to the other in minutes. And when switching, always listen to the product for about the same time and don't judge after the first switch. Your ears adapt to a given sound and any change might be judged as poorer or more spectacular. Also make sure you measure the loudness so you evaluate products at the same loudness for louder products will always be favored. So go and evaluate new audio options this week for it's a great hobby. I love to see you back next Friday at 5pm Central European Time in a new video. If you don't want to miss that subscribe to this channel or follow me on the social media so you will be informed when new videos are out. If you like this video give it a thumbs up. Many thanks to those viewers that support this channel financially. It keeps me independent and thus trustworthy. If you like to support my work too the links are in the comments below this video on YouTube. I'm Hans Bakehausen, thank you for watching and see you in the next show or on the hbproject.com and whatever you do enjoy the music and keep safe.