Edgar

No, but for an experiment like this you could even use the headphone output from your phone as a source.

Try this (never make or break connections while the amp is powered): Keep the right channel connection from the preamp to the amp, but disconnect the cable from the left channel output of the preamp to the left channel input of the amp completely. You should hear loud sound from the right speaker, and possibly very low-level crosstalk from the left speaker. Reconnect the left channel output from the preamp to the left channel input of the amp. Disconnect the right channel output of the preamp to the right channel input of the amp. You should hear loud sound from the left speaker, and possibly very low-level crosstalk from the right speaker. If both of these work as I stated, then the problem is not in your amp. To eliminate the preamp as a possibility, do as @CWOReilly says, above.

Plugging the right output into the left output? I'm sorry, but I'm still not following what is happening here.

I'm having difficulty understanding exactly what you mean in the statements above, but overall what I think you are hearing from the left channel is crosstalk from the right channel. That means that the left channel input on your amp is no longer connected to the left channel output in your amp. That might mean that some component in the left channel low-level signal path has failed.

https://stlouis.craigslist.org/ele/d/house-springs-klipsch-forte-ii-speakers/7504759111.html No affiliation.

Yes. I typically mount them directly to the driver terminals. That way everything upstream of the driver (and Zobel) see nearly constant impedance.

Absolutely! For my last crossover I measured dozens of capacitors, inductors, and resistors. (At one point I even contemplated winding my own inductors, but it turned out that I had appropriate values on-hand.) I fine-tuned with SPICE simulation. My results agreed with yours. If you really want to put the final touch on your results, implement Zobel networks, too.

Assuming that the 8 Ohm driver will be 3 dB more sensitive than the 16 Ohm driver may or may not be valid -- you'd have to check with Altec or GPA about that. If the assumption is valid, then for the same voltage input to the circuit, below 1 kHz both drivers will have the same acoustic output -- 3 dB more attenuation in the circuit compensated by 3 dB more sensitivity in the driver. At 20 kHz, where both versions have about the same voltage output regardless of the driver impedance, the 8 Ohm driver will be 3 dB louder than the 16 Ohm driver.

Well, yes. The 8 Ohm version has 3 dB more attenuation below 1 kHz than the 16 Ohm version.

Looks more like a HF horn driver compensation circuit. HF response starts to roll-off at some high frequency due to mass reactance. Boosting the highs (or attenuating the lows) in the HF circuit compensates for that. Some horns compensate by collapsing the coverage angle in favor of the on-axis response, in which case the circuit is not needed. https://sound-au.com/project173.htm

There is no notch filter in that circuit. SPICE simulations using 8 Ohm and 16 Ohm resistive for HF:

Yes. Then we can discuss the merits of gold-plated, cryogenically-treated, oxygen-free, aligned with the earth's magnetic field, demon-exorcised, audiophile-approved battery technologies.

Eliminate the cryo breaker. Eliminate the audiphile socket and line cord. Run everything off of DC. https://community.klipsch.com/index.php?/topic/165417-just-laughing-outloud-at-this-high-end-nonsense/&do=findComment&comment=2047925

Yeah, sorry, that was a bit out of context, but it wasn't intentional. I was just comparing my reaction with that of @Dave A, and threw-in a little too much information.

For me it's the hair on the back of my neck. It took a long time before digital sources could make that happen, while good vinyl could do it regularly. As my system, and digital recording, have improved over the years, I've found that digital can do it, too.

No, I meant the degree to which they care about what they hear, not about what they listen to. 😉

I have found that most people hear pretty well, once taught what to listen for. What really distinguishes audiophiles from non-audiophiles is the degree to which they care about what they hear.

A few years ago I had a job interview at Harman. I got to speak with their chief amplifier designer, so I asked him what he does differently when designing a consumer amp for Harman Kardon vs. a pro amp for Crown vs. an audiophile amp for Mark Levinson. He answered that the circuits were the same, he would just choose parts that were appropriate for each application -- e.g., 1% resistors for Levinson vs. 5% for Harman Kardon, bigger heat sinks for Crown, etc.

"Mundane claims require mundane evidence." Rarely is there any evidence at all, save for claims of either extraordinary hearing abilities or extraordinary equipment.

And the subjectivists accuse the objectivists of being "closed-minded"? Everyone is free to believe whatever they want. Just don't present opinion as fact. "Extraordinary claims require extraordinary evidence." - Carl Sagan

Superstitions run deep, and are almost impossible to eradicate.

I believe you're thinking of the NS-10.

Physics and mathematics work! 👍

@babadono, great minds think alike.

Were the two unused wires connected to loads? The induced voltage is likely to be higher with an open circuit than with terminations. Try it with a few Ohms on one end (loudspeaker proxy) and a few milliOhms on the other (amplifier proxy). Last time I triamplified my speakers, I braided the cables. That way each one crosses the others at an angle, reducing mutual coupling.