Bill Fitzmaurice

He may have claimed to be a sound engineer, but he was not. That's the Myth of Wave Propagation, see my previous post above.

A pair of 210, vertically stacked, is a good option, but IMO the best option involves spending the least, which is the case if you tilt back your 115, perhaps with a touch of lift as well, which you get from a number of stands.

Your ears are to either side. They're quite capable of hearing midrange coming from behind you, which is a very good thing in the event that said midrange is the breathing of a Sabre Tooth Tiger. That's not a major concern today, but it was when our hearing evolved to become what it remains. I don't care to have my rig in front of me, if only out of 56 years of habit. It just doesn't feel right. Floor wedges are placed where they are because they have to be to prevent mic feedback. Where the OP is concerned since the 115 is what you have tilt it back, by whatever means, so that the center of the speaker is aimed more or less at your head. If you need more output then you'd want to stack a second identical 115 on top. As for the 410, it's the worst possible speaker configuration, unless one of the vertical banks of drivers are low passed. AFAIK the Barefaced Four X 10 is the only 410 with that feature.

You don't need to try a driver to know how it works. The data sheet SPL chart shows how it works in the mids and highs, speaker modeling software shows how it works in the lows. That said, the 320 is quite a bit better than the 300.

It's common for the low end of a speaker to be hard to hear when standing close to it. Reflections off nearby walls and the ceiling create low frequency null zones. If you're standing in one of those null zones the bass will disappear. When you move away from the null zone the true output of the cab will be heard. This effect gave rise to the myth of wave propagation, that it takes a minimum distance from a source for the bass wave to be heard. But if that was true headphones wouldn't work, nor would car subwoofers.

The US is having problems with the supply chain of everything from fuel to food for the lack of truck drivers. Many of those laid off during the height of the pandemic moved on to other higher paying jobs. One reason why ships can't off load their containers is the lack of trucks to transport them from the ports.

It mostly has to do with the Asian side of that other pond. Outsourcing just about everything to there made economic sense when it was done, but not so much when there are hundreds of cargo ships loaded with hundreds of thousands of containers anchored off the West Coats of the US unable to offload. I would imagine similar scenarios exist on your side of the pond.

I can't imagine not having a stand or other method of tilting my speaker back to hear the mids and highs.

If you have to ask then chances are slim that you'd have the chops to do it yourself. The good news is valve amps are easy to work on, if you know what you're doing, and parts are readily available, so it's worth having a tech look at it, if you can find one who works on valve amps. SS is a different story, and the newer they are the harder they are to repair, if it can be done at all for less than the price of a new amp.

https://calculator.academy/speaker-impedance-calculator/

Cabs don't create hiss. They reproduce hiss that amps create, so don't blame the cab on that. Why is everything at 12:00? That gives the same result as if those knobs weren't there. Use them. You should be getting 90dB with less than a watt, so some output voltage testing with a pink noise source is in order. However, I wouldn't put a lot of faith in phone app meters.

It may not be that simple. Is the output balanced or unbalanced? Line or mic level? You need to know to determine what you'll need.

Where what you're hearing is concerned the narrower vertical dispersion of two stacked cabs versus one on the floor is more than compensated for by the higher position of the upper cab.

That's not the one I recall. Mesa does call it a passive radiator, the one I can't remember didn't. In general PRs are smaller than ported cabs for the same result, because a PR takes up less space than a port.

A passive radiator costs more than a port. 🙄 I recall that someone made one, but I don't recall who. I also recall that they didn't call it a passive radiator, they used a different term that implied it was something new and unique, but it was a PR.

Elevate the cab, or at the very least tilt it back so you're on the driver axis. Adding a 410 to a 115 seldom works well, as most 115s can't keep up with a 410. 90% of the time you'll get the best results with two identical cabs.

That would do. The larger the cab the lower and louder it can go with not much power. That's why even in home hi-fi big cabs ruled through the 1940s, when 25 watts was a monster amp, and they still do with Singled Ended Triode amp aficionados.

A tiny cab will have a tiny, as well as tinny, sound. It has nothing to do with power. In fact the less power you have the better result you'll get with a larger versus smaller cab. Google 'Hoffman's Iron Law'. Then have it tattooed on your arm. It is probably the single most important law of acoustics where bass players are concerned.

The advantage to playing open notes is it frees the fingers to fret other notes. JJ would have avoided open E for the same reason we all did back then, the speakers couldn't handle it.

You don't need to use identical drivers, but they should be spec matched as close as possible, as should the enclosure. There's no need for a low pass filter in the extension, the woofers aren't doing much above 3.5kHz anyway. That's one reason why a 2kHz capable tweeter gives a better result. If you're going to run into problems it would be using an 8 ohm 210 along with the 8 ohm 110. That puts half the power into the 110, half into the 210. Doing that you might as well have the extension be a 110 as well.

I doubt that had anything to do with how standard orchestral tuning of the double bass was arrived at. How they decided on E I can't imagine, it's not an octave below the cello, which has a C as it's lowest note.

I play Classic Rock and R&B. They didn't go below E, neither do I. For that matter I doubt that James Jamerson ever hit a low E. That's not a key for horns.

What I can't do with four strings I don't need. 😊

It seems that one's IQ is inversely proportional to the number of strings on the instrument. I remember using those on my bass back in the day, and they were horrid in how they killed the mids and highs because of their capacitance and inductance, two terms not in the vocabulary of most six-stringers. 😊

The only way they'd sound different direct versus daisy chained is if the cables are seriously undersized. All cables have some voltage drop, and when you daisy chain that drop is higher compared to when each speaker has its own lead to the amp. But with the length and gauge of correctly sized speaker cables the voltage drop in either configuration should be virtually unmeasurable, let alone audible. I keep seeing these references to getting more headroom with lower impedance loads. I imagine the reason for this notion is the higher power output into a lower impedance load. That notion should be divested. What happens with a lower impedance load is that for the same voltage output from the amp you get more SPL from the speaker. That's all well and good, but you also draw more current from the amp, so from the standpoint of current you don't have more headroom, you have less.