Would you change your amp selection knowing...?

Adding a network to an amplifier to correct for a cable is a tailspin, just adding eq to eq.

I’d like to see how Goertz calculates a Z of 4 or 8Ω at audio frequencies from their geometry.

SS amplifier outputs are a tiny fraction of 8Ω which is what gives rise to large damping factors. Characteristic impedances are beneficial when the source and load impedances are matched. Almost no speaker is a flat 4 or 8Ω impedance, largely negating any supposed benefit. Typical impedance variations of 4:1 are common and 10:1 is not uncommon.

See Cable Snake Oil Antidote Amplifier Output to see how amplifier output impedance can interact with cables.

@almarg
I’ve never used (L/C)^0.5.

I conceptualize cables as a (SERIES LR with PARALLEL C) x Length. First sum the LR impedances and then add the inverse of the LR sum to the inverse of the C impedance. Z=1/(1/(ZL+ZR)+1/ZC) * Length. It's actually more complicated because ½L is in each lead and R is in both leads with the cap between them

Using the numbers on the link for Divinity, 4nH .98mΩ 1.5nF / ft, I come up with ~0.05Ω @ 1KHz. The impedance is impressively flat relative to a 2 wire standard, but nowhere near 4Ω.

This impedance is in parallel with the amp and speaker. Since the value is so low relative to the speaker impedance, the impedance remains low well past the audio band and can cause some amplifiers problems, particularly if the speaker has a very low Z minima.

A ’benefit’ of plain old speaker cable is its impedance is rising, thus preventing amp problems. The downside is the rising impedance, quadrupling in the region where the ear is most sensitive, is reacting negatively in terms of phase.

@almarg 

Hi Al,
good spotting. ~<|:-/

Actually, I've never seen the formula Z = ( L / C )^0.5.
Where does it originate?

1) 25 foot length as that is what was shown on the MI/AG site in Fig 4. 

3) I mistyped. Conceptually, the cable LR are in series and the C is parallel with the load. 

4) I understand characteristic impedance. A 75Ω cable is designed to be driven by 75Ω source and terminate in 75Ω load impedances. I dealt with PCB impedances for years in high speed digital and have fixed innumerable CATV issues by changing splitters or  terminating open jacks with 75Ω loads for friends and family.

Zip Cord is ~15pF/ft, Belden 1311A ~22pF/ft so 150 to 220pF for 10' is 'normal'. Some Goertz is 100 times as much and that is high.

If bi-wiring, how would these capacitance numbers work...simply additive? or something else??

Parallel doubles capacitance and halves inductance and resistance.

Bi-wiring separates the load into two parts. Response for each part differs from a single drive.

Don't know a thing about Clear Day and they provide no technical information. From reading their information, it seems their product comes from 'messing about' and may be very specific or just generic. Solid core will be stiff. Price seems too low for pure silver of a reasonable gauge, say 18. That's about 4oz of pure silver ~$65. 18ga solid silver hookup wire is about $9/ft. 32 feet for two 8' runs is ~$288. Add in connectors, heat shrink and labor and the price is too low.