Don Richard

I must have pulled that quote by Jeff from you quoting him, and the forum software flaw will not allow me to edit the quote. Sorry about that, Those words are what Jeff wrote, and I completely agree with what you said about the source. Back to time alignment for a moment. The higher the crossover frequency, the shorter the wavelength and the smaller the "sweet spot" becomes. Time alignment does not have to be pinpoint - as long as the alignment is within 1/4 wavelength, you get coherent summation of the two wavefronts from the lower frequency transducer and the higher frequency transducer. As an example, at a 6000 Hz crossover frequency the wavelength is 2.26 inches so alignment within .565 inches works, but the sweet spot at the listening position is small. Now take the well designed Jubilee, a 2 way design with a crossover of about 400 Hz or thereabouts. The wavelength of a 400 Hz soundwave is 33.9 inches, and 1/4 wavelength is 8.475 inches. This results in a much larger sweet spot that does not require one's head to be clamped in a vise, and is an important factor in the high quality sound of the Jub. Another great improvement is the MEH that Chris A has been working on and is also sold commercially by Danley Sound Labs as Synergy Horns. There is no vertical separation of the drivers as they are all using the same horn, a design that results in a perfect point source within the radiation angle of the horn. The Jubilee and Chris's horn use digital crossovers and biamping while Danley's Synergy horns use a passive crossover. None of this is opinion, these are FACTS, except perhaps the exact crossover point for the Jubilee.

Facts can be misapplied, however in this particular case the facts as stated are correct. This is an opinion. Not only that, it is an uninformed opinion. Rest assured I will give your uninformed opinion all the consideration that it truly deserves. Huh? Another uninformed opinion.

This is a reasonable claim. However, this alignment is accurate for one point in space. Moving the listening position forward or backward a few inches can be used to fine tune the alignment once the tweeter is within +/- 1/8 inch. This is also true for speakers besides a Cornwall.

The Shadow knows.

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Sometimes I just can't help myself...

That's about 16 thousandths of an inch. You would have to lock your head in a vise to keep it from moving enough to upset the alignment, unless you were listening from 100 feet away. It's all about the angular difference from moving your head. Trigonometry proves you wrong.

The first time I heard a Khorn mirrors Roy's story. It was a jaw dropping experience - I expected the powerful bass but it was the midrange and high frequency clarity that surprised me. It sounded like live music, more realistic reproduction than any loudspeaker I had heard before. I was a poor college student at the time and couldn't afford a pair, but when I left college and got a job I began to save my money. When I had enough money to buy a pair and rent a house with two good corners I made my dream a reality. That was 50 years ago - many amplifiers, receivers, turntables, cartridges, CD players, and houses have come and gone but the same Khorns are still with me, upgraded over the years, but still here.

What about non-inductive resistors used in crossovers? Do they have a specific orientation too? 🙄

Designed for studio use.

A good explanation of tube output stages: http://education.lenardaudio.com/en/14_valve_amps_4.html

All of that writing to say that SS amplifiers are generally voltage source amplifiers and tube amplifiers are generally current source amplifiers. Of course there are exceptions to the rule.

He described tube amplifiers as "elegant", which I believe is true. He does a good job describing the differences between tube and solid state amps, and the differences between different types of tube amps. He may upset some people with some of his conclusions, but he seems to be correct in his technical assessments. Edit: His writeup on output transformer design and construction is the best I've seen.

For the lengths involved, 16 gage is more than adequate, but using larger wire won't hurt a thing. I rewired a friend's Khorns with #14 because that's what I had laying around.

I remember reading about null tests done by engineers who designed one of the large analog mixing consoles that were used in recording studios at that time. The engineers looped a signal from a channel output to another channel input, then ran the null test on the second channel's output. They looped over a dozen channels in series before artifacts could be heard. I don't remember exactly how many opamps and discrete components were in each channel strip, but there were quite a few.

Problem solved!😀

This would be a good way to find any microphonic tubes. Or make them microphonic if they aren't already.

Yes, but I don't even do this once a month. As a homeowner, you are entitled before 10 pm to enjoy music at your residence. What disturbs me is when the next door neighbor cuts his grass at 7 AM with his loud mower. That's legal, and I don't complain. What disturbs me is when their kid tunes his drag race car up at 8 PM. That's legal, and I don't complain. What disturbs me is when their kid takes his racer out on the street and does burnouts at 8 PM. That's both illegal and dangerous, and I call the cops. What disturbs me is when those same neighbors complain when I occasionally play my stereo loudly, which is less than 50 dB right outside my house. Unbelievable!!

You can stage a rock concert with that👍

DJK, RIP, had written about the PPSL design here and on other audio forums. If you search the archives there are several threads about PPSL bass bins, both here and elsewhere.

There were two local guys in the late 60s who made a no holds barred stereo PP class A tube amp that featured regulated DC filament power and regulated B+, two separate channels in one enclosure with a cable connecting the power supplies to the amplifier. The power supply was bigger and heavier than the amplifier by quite a bit. That, and the one you linked are the only ones I've seen like that to date. Any idea what the dynamic headroom is for your amplifier?

What's cool is that distortion is lower at those low power levels, probably lower than any other type of speaker. The clarity of horns in a home setting is truly amazing.👍

Most test results I've seen are for solid state amplifiers, and stiffly regulated supplies with those result in less dynamic headroom. Can you show me a schematic of a very highly regulated supply in a typical tube amp? Mostly I've seen filter circuits with an input cap, a choke and an output cap, but it's been years since I've messed with tube circuits. I have built tube circuits that had regulated bias voltage, but the B+ had no regulators for the most part.

This is correct. FTC standards do not apply to home theater equipment, pro sound, or auto sound. QSC provides FTC numbers for some of their amplifiers, and some home theater products give FTC numbers for 2 channel operation, but that's not commonly done.

Dynamic power is a result of the Federal Trade Commission standards for home stereo equipment. During the FTC method of power rating the amp is run at 1/3 power for an hour before testing, then the power is measured up to a defined distortion level. That is the continuous average power rating, erroneously called "RMS power", of the amp. An amplifier may be able to put out more power than the FTC rating without the preconditioning at 1/3 power, for a shorter period of time, and perhaps at a different distortion level. That is the "dynamic power" of the amp. Unlike the FTC power rating, there are no standards for the dynamic power number. In general, amps with a stiffly regulated power supply will have less dynamic power output than amps with unregulated or less stiffly regulated power supplies. Peak power for a sine wave is 1.4 times average (RMS) power. For non sinusoidal signals the crest factor of the signal is a determining factor in computing peak power.