september.org> 69fd7f17   
   On Monday, July 2, 2018 at 1:41:13 PM UTC-4, G wrote:   
   > I understand effects of electrical damping of woofers. I'm wondering how It   
   > may affect midranges and tweeters. Is it the same, or does it dimish at   
   > higher frequencies. Remove any crossover components for direct feed to amp.   
   > Tone bursts should Show any difference in DF. Without testing, I'm   
   > guessing.   
      
   To cut to the chase: forget about "damping factor." It's essentially   
   a made-up "spec" that indicates very little about the performance of   
   loudspeaker drivers. Really. The important number, if you're worried about   
   how well a driver is controlled at its resonance, is it's total Q   
   factor: in the case of the driver itself, it's the Qts of the driver.   
      
   The Q of any resonant system is a measure, essentially, of the   
   ratio of the amount of energy stored in the resonance to the amount   
   of energy dissipated. In the case of a driver, you have essentially   
   three ways by which that energy is dissipated, or lost or, if you prefer,   
   how it is removed from the system. These are:   
      
   1. Electrical losses, which, for most drivers, is the largest   
      loss mechanism (and is usually specific Qes),   
      
   2. Mechanical losses, which, for most drivers, is secondary   
      to the electrical losses (designated as Qms),   
      
   3. Acoustical losses, i.e., the sound that is actually radiated   
      into the room which, for almost all drivers, is an insignificant   
      loss mechanism (this is why speakers are so inefficient).   
      
   Now, #1 might seem contradictory to me declaration that damping   
   factor is essentially useless, since we are (I assume) talking   
   about electrical damping, but it becomes clearer once you realize   
   the fact that it's the total resistance in the circuit that's   
   responsible for the electrical Q. That not only includes the output   
   resistance of the amplifier (which is where the "damping factor"   
   spec comes from), it not only includes the electrical resistance   
   in the crossover (not impedance, not inductance, but resistance),   
   it also includes the DC resistance of the voice coil.   
      
   The problem is, far and away, the single largest resistance in that   
   collection is the DC resistance of the voice coil. That resistance   
   dominates all others, and attempting to reduce the other resistances   
   (crossover, speaker wire, amplifier) won't make a hill of beans   
   difference in the damping of the system.   
      
   Le's take a typical 8-ohm woofer, with an equally typical DC   
   resistance of about 6.5 ohms. Let's assume the mechanical Q   
   of the driver is 4, the electrical Q is 0.85, and the resulting   
   total Qts is about 0.701 (Qts = Qes*Qms/(Qes+Qts). How is this   
   going to perform with an amplifier whose damping fact is, say,   
   1000 vs one whose damping factor is 50. One might be inclined   
   to say that there will be a factor of 20 difference in the   
   damping of in each case (1000/50=20), but it turns out not to   
   be so.   
      
   Whatever with a damping factor of 1000, our "highly-damped"   
   amplifier has an output resistance of 0.008 ohms, while our   
   "not-so-well-damped" amplifier has an output resistance of `0.16   
   ohms.   
      
   The amplifier output resistance will increase the electrical   
   Qes: in the case of the first amplifier, it will increase it from   
   0.85 to 0.851 (Qes' = Qes * (Re+Rg)/Re. In the second case, it   
   will increase it from 0.85 to 0.87. NOt much.   
      
   But it's the TOTAL Qts that we're interested in. In the first case,   
   it will change from 0.701 to 0.702. In the second case, it will change   
   from 0.701 to 0.714. In both cases, the actual damping of the system   
   changes by less than 2%. This is less than the typical variation in   
   these kinds of parameters one finds from one sample of a driver   
   to another.   
      
   The situation with midranges and, especially, tweeters is even   
   more the case where these external resistances have little   
   effect, because in these cases, the total Qts is more heavily   
   dominated by the mechanical losses, and thus changes in the   
   electrical Q have even less of an effect. Further, in many systems,   
   the principle resonance is designed outside of the operating   
   bandwidth of the driver by the crossover, so it has even LESS   
   of an effect.   
      
   > Tone bursts should Show any difference in DF.   
      
   Tone bursts are very likely to tell you nothing useful at all.   
   They're not a terribly useful test in and off themselves and,   
   given the very small changes you're likely to encounter in   
   the changes you're proposing, a tone burst is not going to   
   reveal anything. Further, tone bursts are very hard to measure.   
   Bump your microphone a little bit, change its position, and   
   you'll measure a different tone burst   
      
   --- SoupGate-Win32 v1.05   
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