Bill Fitzmaurice

It may not, the loop could be on the back side of the input stage but before the gain control. The manual should say.

The mass of the steel of the frame is dwarfed in comparison to that of the top and bottom plates, so it's a minor concern.

Cast aluminum baskets are used for two reasons. With heavy ceramic magnets it's to be stiff enough so that the frame doesn't flex. With neo magnets it's to act as a heat sink. Steel is OK with lighter weight ceramic magnets, and with lower power neo magnet drivers that don't require much heat sinking. Eminence uses steel for their 150w Basslite series, cast aluminum for the 250w and higher Delta Lite and Kappa Lite. Where frame stiffness is concerned there are two requirements for very high sensitivity. One is a high flux magnet, the other is a tight magnetic gap. If the magnet weight causes the frame to flex it can cause voice coil rub with a tight gap. That was a problem with the 1968 Electro-Voice SRO 15, later re-badged as the first generation EVM. It had a cast aluminum frame, but with only four spokes, so it would flex under the weight of the 16 pound magnet structure. The second generation EVM cured that by going to an eight spoke frame.

There's very little difference in the sensitivity of different cabs, but a lot of difference in their response and mechanically limited power. The only way to be sure of a good match is with identical cabs.

There's not much sensitivity difference between different drivers. Where going loud is concerned that's a matter of excursion/displacement, which is pretty much a matter of price. Longer excursion/higher displacement drivers cost more than shorter excursion/lower displacement drivers. The only manufacturer I'm aware of that reveals displacement is Barefaced, which doesn't aid in making comparisons, since you don't know the displacement of other brands. But suffice it to say that no other brand exceeds Barefaced, and very few, if any, equal it.

Download the manual. It may have a thermal switch.

A good example. Xmax of the Greenback, and for that matter most guitar drivers, is very short. The result is high distortion at moderate power levels. This relates to us in the form of the original 1969 SVT. It was loaded with short xmax musical instrument drivers, as there were no long xmax tens in 1969. Even eight of them couldn't run clean with the 300w SVT head. The cabs were rated at 240w thermal, while the mechanical capacity was at best 120w. That's why those who could afford them used the Ampeg recommended two cabs.

In most cases the xmax isn't available. The mechanical power limit of drivers averages around half the thermal limit. Some are higher, some are less. Some even have a mechanical capacity equal to or greater than the thermal. But those are high cost premium drivers that are seldom seen in electric bass cabs. Here again don't take my word for it, verify it yourself with speaker modeling software. As a for instance, the Eminence Deltalite II 2510 is the most popular neo ten inch platform. The thermal rating is 250w. The mechanical limit in the critical 80-100Hz region is 100w. And the 2510 is better than most. The most popular ceramic ten platform is the Eminence Beta 10. The thermal limit is 250w. The mechanical limit is 60w.

No doubt Ampeg is one of the more honest manufacturers. Their power ratings are conservative. But the fact remains that without xmax or Vd one simply cannot calculate max SPL. Try it yourself, using any of the common loudspeaker design programs, leaving xmax/Vd out of the parameters. You can calculate response, impedance, phase, group delay, port velocity, but when you go to the max SPL chart it's left blank for the lack of the required specs. This isn't picking on Ampeg by any means. AFAIK Barefaced is the only manufacturer that provides that critical bit of information.

A rig of that sort will only sound as good as the crossover allows it to. That means having sufficient high pass slope to prevent over-excursion of the midranges. It also means low passing the woofer cab, otherwise the woofers and midranges will fight each other where they're operating in the same frequencies. MIdrange drivers are a good idea, but as is the case with all good ideas it's the execution that determines success versus failure. If the bright box doesn't have a jack to send a low passed signal to the woofer cab the execution was flawed. If they didn't do that then the high pass filter, if it has one, is also likely to be inadequate.

Probably, but thermal power capacity has no relationship with maximum SPL. A 100w driver with 5mm xmax will go 3dB louder than a 200w driver with 3.5mm xmax.

Without xmax you can't calculate maximum SPL.

3dB higher sensitivity from the fifteens, which is easy to come by, makes 200 watts the equivalent of 400 watts into tens. Of course not all fifteens will have 3dB higher than all tens, but most will. Going to a pair of 210s would likely be competitive with a pair of 115, but that's not one of the options he mentioned.

Decibels is a matter of speaker sensitivity and frequency response. On average fifteens have higher sensitivity and lower frequency response than tens, so on average two fifteens will go louder and lower than two tens, even when driven with less power.

Since it's loaded with Eminence OEM probably built on the Alpha 10 chassis 95dB is a reasonable expectation. So is a high Fs and short xmax.

Not any American I know. 😉

It's also harder to mess up parallel. That's the only reason I can think of for Ampeg using 32 ohm drivers in the 810 SVT.

You can in Italy. For that matter it's mandatory.

Wire it parallel for 4 ohms. Tube amps aren't bothered by lower impedance loads than the tap rating. It's higher impedance loads that they don't care for.

The Rumble 200 plus extension would be louder. It's not about watts, it's about decibels.

Even in 1961 it was second best to Ampeg. 🙄

Correct. At 3kHz, for instance, 1/2 wavelength is 2.25 inches. That means it's impossible for electric bass woofers to fully couple to 3kHz. The highest tens will go is roughly 675Hz, so 'ideal' spacing is impossible. That's why vertical placement is key, so that the effects of spacing beyond 1/2 wavelength won't be heard on the horizontal plane. The opposite. The CTC from the top woofer to the bottom woofer doesn't matter, it's the spacing between adjacent woofers that counts.

There are two factors in play. In the lower frequencies where the two woofers are spaced close enough to mutually couple, which means they act as one, the dispersion angle across the sound field with vertical alignment is twice that of horizontal alignment. In the higher frequencies where they're too far apart to mutually couple their outputs alternately reinforce and cancel each other as you go across the sound field when placed horizontal, what's referred to as comb filtering. When placed vertical the response is constant across the sound field. Standing next to the cab you wouldn't notice it. Further away standing in one spot you wouldn't either. But when you're even a few meters out they will sound different as you walk across the sound field. Where comb filtering occurs they'll sound different in the highs with as little as a few inches of listening position shift. Long before I knew a Hz from a dB I knew that two cabs made a world of difference. This was in 1967, when I got a second cab for my '65 Bassman. With one cab the Bassman was barely usable. With two it was tolerable. Wanting to know why was the impetus for my heading to the engineering section in my college library the following year. There I found 'Acoustical Engineering' by Harry Olson. Even though it was written in 1957 it remains to this day the Bible of loudspeaker designers. A year later I began designing and building my own.

If they're identical sensitivity and maximum output go up by 6dB, the equivalent of quadrupling power. Intelligibility of the mids and highs for you increases by having the source closer to ear level.

By the same token isolation doesn't work either. Isolation can reduce the vibrating of a cab atop a soft floor, which is vibrating as the result of acoustic resonance excited by the speaker output. What it can't do is reduce the vibration of the floor, as that's acoustically sourced, not mechanically. http://ethanwiner.com/speaker_isolation.htm https://www.bassgearmag.com/submit-article-bass-amplifier-isolation/