Bill Fitzmaurice

That depends on the PA. The current preferred topology is mains that work from between 80 and 100Hz and up, with subs handling below that. This is in stark contrast to PA up to about 20 years ago that usually ran the full bandwidth in a single cab. Those systems didn't go particularly low and loud, in fact they had low frequency response not all that different from electric bass cabs. Modern subs do have low frequency response significantly different from electric bass cabs, which in tasteful hands can be a good thing, in tasteless hands a very bad thing. If you have mains that only go to 80-100Hz and you want to put low frequency sources in the PA you need subs, but you need someone at the helm who knows what he's doing, not just the proverbial friend of the band.

The #1 reggae cab is the 'Fridge, and it's by no means a sub. A real sub on the back line is a bad idea, since you won't know what it's doing out in the room. Even real subs on PA can be problematic when the FOH engineer doesn't know what the electric bass is supposed to sound like. Those who do will high pass the bass channel between 60 and 80Hz, to end up with response in the PA similar to the back line amp. That means if the PA is well engineered most of the electric bass content coming out of the subs is between 60 and 100Hz. The worst bass mix I ever heard was Greg Lake. His stage tone might have been good, he was using an SVT. But out front a moron sound man had him so loud below 80Hz that when Greg played anything below a D note it drowned out the rest of the band, while anything he played above that literally disappeared and wasn't heard at all. If Greg had heard what that sound man was doing he'd have pummeled him.

You don't even have to search out other threads, why it's not useful in general has been explained in this thread, repeatedly, including just a few posts before this one. The only reason to want a 4 ohm/8ohm 112 cab is to allow using it with a valve amp that needs a maximum 4 ohm load and with an SS amp that won't take a 4 ohm load.

Damping factor is a non-issue. It was highly touted as being important when SS was introduced, but only as a sales tool to convince people to abandon valves. http://www.cartchunk.org/audiotopics/DampingFactor.pdf

If all is the same a 4 ohm and 8 ohm cab will sound the same. But all else is seldom the same. The usual reason why someone would be driving a 4 ohm load is they have two 8 ohm cabs. Two cabs will almost always sound better than one. For a low power amp to get a real benefit from 4 versus 8 ohms it would probably have to be rated 25% or less than the speaker power rating.

They did disappear for a while, then came back. I stopped taking them seriously when I saw an interview with the owner, whose name escapes me, where said that he got the inspiration for his speakers in a vision from God. I might have thought better of it had he said it came in a vision while doing peyote and listening to Clapton.

JBL does make some unusual dual coil drivers, which they call Differential Drive. Instead of the usual one coil over another on the same former they have a front coil and a rear coil, along with front and rear neo magnets that don't use a pole piece, front plate or back plate, because they're small enough to fit inside the coils. I don't think they have the ability to choose between series and parallel wiring of the coils.

Not that I can think of. The original reason some sub drivers used dual coils was to sum the L/R channel low frequency content, back in the days before receivers had LFE outputs and subs went from being mainly passive to being mainly self powered. They're becoming less and less common as there's no real need for them anymore.

OK, once more, but this time with feeling: Use a dual voice coil driver. One coil 8 ohms, two for four ohms. I don't know if that's what Hartke does, but it's one way to do it.

It was, and it was a fraud. He put a capacitor in series with one of two paralleled woofers, with a switch that bypassed it. When you measured the DCR with the switch off the cap stopped the DC from the meter from reaching the voice coil of its associated woofer, so the meter only read the DCR of one driver. With the bypass switch on the meter read the DCR of both drivers. One possible explanation of why Accugroove pulled this is that the owner, who's a bit of a loon, didn't know the difference between impedance and resistance. The other is that he was aware that it didn't work, but thought no one would catch him. I lean towards the latter, because the magic component, a capacitor, was encased in epoxy, to prevent anyone from seeing what it was. Interestingly before the AccuSwitch scandal broke someone posted the question on a forum, maybe even this one, if a circuit of this sort would work. I told him why it woulldn't.

Use a dual voice coil driver. One coil 8 ohms, two for four ohms. I don't know if that's what Hartke does, but it's one way to do it.

Your amp power is moot, you'll never run the amp at anywhere near full power. Besides, with 3mm xmax that driver will fart out at well under 100 watts anyway. Tune the cab to 50Hz Use two 2" ports 5 inches long.

Penn-Elcom makes a tilt back folding foot.

The answer remains the same.

There are many considerations involved, so many that you need to use a speaker modeling software program, like WinISD, to determine the correct port sizing.. http://www.linearteam.org/ If you don't have the driver Theile/Small specs you can't use modeling software. If it's a guitar driver it won't work anyway, for a variety of reasons, any more than you can use guitar strings on a bass.

I only took a full 470 once, exploring my '65 Bassman, discovering that capacitors store charge for a long time. Working on AC outlets I probably got hit a hundred times over the years, too lazy to make my way to the breaker box to turn the circuit off. That's common with electricians here working with 110v. I suspect on your side of the pond with 220v they tend to be more careful.

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.