Please explain amplifier output impedance

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.

I have been following this thread with interest and doing my own novice research on this topic and it seems that there is no right answer here in terms of whether or not damping factor is a relevant spec. Here are some of the tidbits I have picked up:

1. The mechanical damping of the speaker plays the largest role in terms of how the cone movement is damped

2. The effect of any damping factor above 10 is impossible for humans to hear

3. A static damping factor number does tell the entire story since both amp and speaker impedance changes with frequency.

4. A high damping factor is misleading as it could mean the use of a lot of negative feedback which could have adversely affect the sound

These are just some bits of info I have picked up from reading about dampiing factor so please refrain from blasting me with flames. I am by no means an expert in this area.

I think there is no real good rule of thumb. Everyone has to just listen to the amp/speaker combo and decide for themselves.

I think there is no real good rule of thumb. Everyone has to just listen to the amp/speaker combo and decide for themselves.
Tboooe (System | Reviews | Threads | Answers)

Not to necessarily critique Tboooe's comment, but it prompted a thought.

It seems to me that if considerable discussion is had by several contributors to this thread, all of whom appear to know what they're talking about (at least to this non-technical layman), specifically identifying output impedance and/or damping factor as it relates to speaker impedance and how they affect sound. And, if mathematical relationships are developed that correlate and explain amp/speaker performance, which is what I gather has been discussed in these posts...then, to toss it all away by saying that there is no good rule of thumb and everyone simply has to listen to amp/speaker combinations and decide for themselves, is to disregard science and engineering and instead throw up our hands at any attempt to use specifications to narrow down choices for the best potential amp/loudspeaker matches.

I come away from these discussions believing the audiophile hobby is overcomplicated. This is undoubtedly due to the large numbers of boutique specialists who build their products in a semi-vacuum choosing to place ease-of-use and ease-of-matching at the bottom of the priority list. I understand this can be a benefit insofar as it allows almost infinite possibilities to tailor a system's sound, but it can also work to a cross purpose by keeping the goal elusive.

Please accept this as a comment from a music loving end-user who is not an electrical engineer, technophile, or DIY'er.

Someone could make a fortune by simplifying. I suppose Linn has been the most successful at this concept...and perhaps NAIM to a lesser extent, but these two manufacturers still haven't cornered enough of the market for me to believe there isn't room for others on a smaller scale and budget.

Thank you. Please remember to tip your waiter or waitress... and try the veal.