On 2/15/2017 12:42 PM, PStamler wrote:
Capacitors, unfortunately, don't become low impedance at high frequencies; since they're made of rolled-up layers of foil and dielectric, they have an inductive component, and at high frequencies this becomes the most important; real-world capacitors show an impedance that falls with increasing frequency up to a point, then bottoms out, and rises as the frequency increases.
Well, of course I'm aware that all capacitors have parasitic
inductances (and Equivalent Series Resistance, or ESR), which is the
reason why we keep leads lengths short in the radio frequency world,
when not using chip capacitors:
http://sound.whsites.net/articles/capacitors.htm#s30
But in the audio frequency world, where we are only concerned about
up to 22kHz or so, I we shouldn't see the impedance start rising again.
Let's assume from the above link that we have about 5nH of
parasitic inductance mainly due to lead length:
XL=2*pi*f*L
And using f=22kHz, and L=5nH, we still only get about 69 milli-Ohms!
Glad you had fun. Watch out, though -- speaker building is addictive.
No worries on that....as you can see, I'm shopping for
an already built PA speaker now.
Sometimes it's best to leave things to the professionals!
Peace,
The Other Paul