Bill Fitzmaurice

A pair of 212s vertically stacked will sound better and makes for a much easier haul.

Oh come on, you don't know what fun is until you've had 470 volts make their way through your body. 🙄

The impedance would be 2.4 ohms.

Why wouldn't I? Unless you think commercial cabs are somehow better. FWIW right around the same time I designed the Jack 12 I also designed an award winning, as in 'Speaker of the Year', 1x12/6 for a manufacturer. I took both prototypes out on a few gigs. The J12 design ended up on my website, the J12 prototype is still my main cab. The drivers used in the other prototype are on a shelf in my basement, the cab is fertilizing my garden as wood ashes.

This ain't FRFR:

The good ones do. They'll take a DI for the lows, a mic for the mids and highs. The reason for the DI lows is to minimize stage rumble that a mic will pick up, and to get a better low frequency signal than the speakers can deliver. The limitation is that to do this the board needs enough channels to devote two to the bass.

Firing the amp up without a speaker wouldn't bother a Fender, the speaker jack is switched to short the output transformer secondary when there's no plug inserted. Electrolytic power supply caps dry out, whether the amp is used or not. 25 years is the usual life span.

The power supply caps. They were about 20 years overdue for replacement.

A PA speaker might do, but the number of those which have SPL charts is dwindling as well. Much of the reason for that is the proliferation of powered PA speakers with on-board DSP. They don't need flat native response from the drivers, the DSP sees to that.

Before the voice coils burn out, yes. Before they reach xlim, the excursion before mechanical damage occurs, probably. Before they reach xmax, which can cause evrything from moderate low frequency compression to high level harmonic distortion to full on farting out, no way to know unless the manufacturer reveals that information. The number who do so can be counted on the fingers of one hand, with at least two fingers unused.

Neutral means no coloration, ie., flat response. You can have flat response with any driver size. Finding a manufacturer who publishes measured response charts that prove their cabs have flat response is probably a fruitless quest, though.

As far as volume fluctuation goes if you're playing is a lot louder with a pick I'd say you're hitting the strings too hard. A soft pick would probably encourage that.

I use the same settings with and without a pick. I switch from fingers to pick, and vary the angle of the pick and where I strike the strings anywhere between the end of the neck and the bridge, for different tones. I use D'Addario Delrin, very stiff. I use the same picks with bass and guitar. Light picks don't give me enough control. I don't know if they even make these any more, bought a gross of them many years ago, and they never break.

My guess is at least thirty, give or take.

That does result in narrower dispersion than having them vertical, though not as much as having them horizontal.

That gives two benefits you don't get if they were side by side. The stack is higher than it is wide, which makes the dispersion pattern wider than than it is high, and the uppermost drivers are closer to ear level.

My 2x cabs are all vertical. If you use two they should be stacked vertical. There's no reason why they would have less mids/highs than the TC. The TC RS cabs look to be an improvement over the usual 2x10, but at least in their advertising they don't show the upper cab in a vertical stack inverted as it should be.

The issues with lessened midrange dispersion and high frequency combing when drivers are side by side are eliminated when one side of drivers is low passed, meaning they have no midrange or high frequency content. It's a very simple concept, so simple that one can't help but wonder why it's not universally employed in 4x, 6x and 8x cabs. I don't do so in any of my cabs, because I don't do a 4x, 6x or 8x. But I did describe why it should be done and how to do it on bass forums ten or more years ago.

I assume that one of the drivers is low passed, one run full range. If that's the case the best way to have them vertically stacked is with the full range driver at the top of the lower cab, with the upper cab placed upside down, so that the two full range drivers are adjacent.

Vertical. Horizontal narrows the midrange dispersion angle by over half, creates comb filtering in the highs, and makes it much more difficult for the player to hear the mids and highs. There is no loss of low end, as the drivers are all fully mutually coupled and acting as a single driver in the long wavelengths which benefit from the boundary reinforcement the floor gives. It may seem that there's a loss of lows, but that's not the case, it's just that you can hear the mids and highs with a vertical stack far better than with a horizontal cluster.

Don't forget about Geddy Lee- Whirlpool.

As has Sting, but Martin and Clair Brothers aren't your average PA cab. One does have to pay the bills.

Passive PA cabs within the same price range as bass cabs tend to be not all that much different where the woofers are concerned. The usual difference is larger HF horns that cross over at lower frequency than tweeters is bass cabs. You may prefer that, especially with larger than ten inch woofers, but there's only one way to know and that's to try before you buy.

Most of what makes tubes sound like tubes is compression in the output tubes and output transformer, which you can't really duplicate with anything in the front end, including tubes. Still, if you're going to get any improvement it will be with a good compressor.

No load connected isn't very low impedance, it's very high impedance. It's not quite infinite, as there would be some load provided by the output transformer itself by losses within the windings, but almost. All of the power produced by the tubes still goes into the output transformer primary windings, but with no speaker connected it has no way of flowing out the secondary windings. Bad things ensue. That's also why too high an impedance load can injure both the output transformer and tubes. The power put into the primary windings can't flow out of the secondary windings as easily as they should. SS is the opposite. With no load no current passes, so no harm no foul. With too low a load impedance too much current passes, stressing both the output devices and the power supply.