Bill Fitzmaurice

The ground lift wouldn't affect the level. It's only purpose is to prevent ground loop hum.

The total load capacity is 2 ohms. Daisy chaining and individually connecting them to the two outputs is the same, parallel wired, and in both cases the total load is 2 ohms. There is a very slight advantage to connecting them individually, as that way you don't have one cable carrying the current drawn by both cabs. For that advantage to be meaningful your cables would have to be much too long and of too light a gauge.

You can get a Real Time Analyzer app for your phone. It may not be laboratory grade, but it will enable you to make comparisons between different cabs.

Driver manufacturers yes, speaker manufacturers, no. Your plot appears to be that of a raw driver mounted in a wall. What's seen will remain pretty much the same when mounted in an enclosure above roughly 200Hz, but below that where the enclosure is a much responsible for the result as the driver it will be completely different. That same driver in ten different enclosures will have ten different result in the lows. Even without the enclosure information one can tell that it won't do well in the lows, as the impedance plot shows a resonant frequency of 65Hz, which is at the upper end of useful for an electric bass driver. That's to be expected with a driver with that sensitivity.

Not really. Most Eminence drivers have always had a rising sensitivity in the mids, peaking in the 2kHz-3kHz range. They have not changed that with their neos. The same is true of Celestion and Fane. What you are seeing is more use of European brands, like B&C and Faital Pro, which tend to have flatter response, with all their drivers. They're fairly common now, but were hardly ever used in electric bass cabs as recently as fifteen years ago.

None. There are many factors that influence both sensitivity and frequency response. The magnet material is not one of them. By no means are neo magnet drivers or newer design drivers more sensitive. One of the highest sensitivity drivers ever made at 101dB/1watt was the original JBL D-130. It had an AlNico magnet, it was created in 1947, and it wasn't a musical instrument or PA driver, it was originally intended for hi-fi. It also had poor low frequency response, with a 100Hz F3 and 45Hz F10, but in 1947 that was sufficient for the program material that was available.

The answer is complicated, because most of the Thiele/Small specs contribute to the driver sensitivity, as does the enclosure. There's no reason why you'd need a lower sensitivity speaker per se, but by and large what contributes to higher sensitivity also contributes to less low end extension, and vice-versa. For that reason if you see a single driver speaker rated at more than 98dB/1w it probably doesn't go very low. By the same token if a single driver speaker claims to be -3dB at 35Hz it can't have much more than 93dB sensitivity. And lastly, if a small speaker claims both low extension and high sensitivity they are, in a word, lying. It's all summed up by Hoffman's Iron Law.

That's the key question. Some manufacturers play fast and loose with their sensitivity ratings, quoting, for instance, what it measures in the midrange, rather than in the lows where it really matters. For this reason ignore sensitivity ratings that aren't accompanied by a chart of sensitivity across the full frequency spectrum. SPL (sound pressure level) charts are common with better PA speakers, but they're totally unknown in the electric bass cab industry.

Venting the cab may help, but you can't just willy nilly cut a hole in it. The area and depth of the vent is critical to a good result, as is the cabinet volume, and both are determined using the driver Thiele/Small specs with speaker modeling software. Or the driver specs may not be suited to a ported enclosure at all.

You're the bassplayer, that makes you the smart one in the band. Really. The majority of top tier engineers and designers who also play an instrument are bass players. My personal experience, that many others have also stated, is that since the equipment demands of bass are so challenging they more or less had to learn the science. It's a more than worthwhile endeavor. I made a tolerable enough living as a musician when that was my primary source of income, but I made my fortune as an engineer. To be more helpful with your issue I'd need the particulars on the driver and enclosure.

The speaker thermal rating is almost meaningless, and for that matter so is the amp output. Where the speaker is concerned this is what matters: https://www.eminence.com/support/understanding-loudspeaker-data/

I haven't seen mention of it but if the DI output is XLR then it should have a low output level, otherwise it could overload the board input.

If the EQ is flat at noon what it gives you is the same result as if they weren't there at all. They're not supposed to be merely for decoration. It's a far cry from the 60s, when we all played valve amps with mediocre speakers. The usual protocol then was to turn everything to '10', unless of course you had the option to go to '11'. 😎

"If it sounds good, it is good". Duke Ellington. Even before the current FRFR craze there was the 'set it for flat response' craze, where players would automatically set all the tone controls at noon, resisting advice to do otherwise, because they wanted flat response. It was a silly notion, because nothing in the signal chain is flat, starting with the pickups, ending with the room. If they somehow had managed to get truly flat response it would have been as bland as flat beer.

It's listed as -10dB at 50Hz. That's not full range. It's what you'd expect from a main intended for pole mounting, with subs handling below 80Hz. The only advantage I see to it is that the 1.8kHz crossover from the woofer to HF horn makes far more sense than the usual 3.5kHz or higher crossover from woofer to tweeter in bass cabs. Not that a 3.5kHz or higher crossover from a woofer to tweeter makes any sense. It doesn't. 🙄

Your Ashdown is a passive speaker.

Valves need a load because current always flows through the output transformer primary winding. SS needs no load because when there's nothing plugged in to the output no current flows from the output devices.

Hoffman's Iron Law and the presence of standing waves are not related. Phil Jones cabs are not line arrays.

The power handling chart has limited value, as power alone doesn't reveal maximum SPL capability. By the same token the transfer function magnitude chart doesn't reveal sensitivity. IMO the chart order of importance is SPL, Maximum SPL, Impedance, Rear Port air velocity and then Maximum Power. The primary use of Maximum Power is to plug that value into the Signal Source window, then check the Rear Port air velocity to see if it's no higher than 20 within the intended pass band.

I wouldn't mic so close to the cab in a live situation that it would make any difference.

The SM57 and 58 use the same cartridge, only the grille is different. https://www.shure.com/en-GB/support/find-an-answer/sm57-vs-sm58

I've never cared to hear anything coming out of my rig other than me, it's very distracting.

Plan B is OK assuming the speakers are not part of your backline. You'd be a very unhappy camper were that the case.

Crossing over at the usual 80Hz there's little to no vocals in the subs anyway, nor guitar. But there's plenty of content above 80Hz from both the bass and the kick that should be in the PA. Even when I don't bother with subs I always run the bass and full drum kit through my PA, not for volume, for dispersion.

You'll need more than one. Power and driver displacement requirements go up exponentially as you go down in frequency. If you have a pair of ten loaded tops it will take a pair of eighteen, or very high end fifteen, loaded subs to keep up with them. If it's an outdoor gig you'll have no low frequency boundary reinforcement, which means doubling the sub count for the same result as indoors. All things considered you're best off renting.