Please explain amplifier output impedance

Success! And in only six days...

:)

Success? I would consider damping over 20:1 to be excessive. I use master tapes for reference and one thing has become clear over the years: high damping factor equates to not getting the bass right; retentive (not in a good way) IOW punch without real definition and the first thing to go is always low frequency ambience.

Some speakers are intentionally designed for amps of higher output impedance (new paradigm, BTW) in order to take advantage of the benefits such amps offer. IOW there is no *ideal* value for output impedance- it all depends on the speaker...

The lesson here is that you have to pay attention to the speaker/amplifier interface regardless of the amplifier or speaker that you have chosen. To ignore this means you could flush thousands of dollars away to no good effect.

No success?

Oh well. I've learned a lot. You guys have fun.

Hi Gregm,

No problem, that's a fair question. I won't give a highly specific answer, but hopefully the generalities will be useful.

You can design a crossover with the values optimized to produce the desired transfer function with a minimum number of parts. Or, you can design a more complex crossover that uses what looks like redundant circuitry, such as parallel resistor legs at different places within the circuit. The more complex crossover gives you more options when you start trying to juggle the impedance without spilling the frequency response.

I worked within the minimum-parts-count topology to smooth the impedance, but at best was only able to keep it between 7 and 27 ohms above the bass peaks (a nearly 4-to-1 spread). The 27 ohm maximum was at about 3 kHz, which is not a good place to have a response anomaly.

Switching to a what-the-heck-high-parts-count topology, I got the impedance down to between 8 and 13 ohms above the bass peaks, and the 13 ohm maximum is at 400 Hz where an extra dB or so helps offset the baffle step a bit.

The topology and combination of values that produced a good impedance curve without spoiling the frequency response was largely the result of trial and error. My modelling program did not do a very good job of predicting what the impedance curve would be, perhaps due to non-ideal behavior of the components. So I spent a lot of time changing crossover parts, measuring frequency response, and measuring impedance. I'm sure there's a better way.

Duke

Success. I think we all agree if you accept that my persepctive is "old school" (from electronics text books, linearity, accuracy etc.)

Furthermore, I fully agree with Atmasphere that a low frequency ambience or bass definition is what a tube amp or an amp with a lower damping factor does to the sound.