Bill Fitzmaurice

It had four notch filters for feedback control. Their frequencies weren't adjustable so they weren't very effective.

I bought my first SM58s in 1973. I doubt they were around much before that. They were an updated version of the 565. They were the first low impedance mics I owned, before that it was all high impedance, with 1/4" plugs. Mixers as we know them today hadn't been invented yet. The only mixers that could use low impedance mics were recording and radio broadcast mixers. I had to add another gain stage to the first generation Shure Vocal Master we were using to get it to work with the 58s.

It's not likely, with the exception of drum mics. But two points. First, sub output is omni-directional. Be they in front or in back of you the mics will still pick up the same content in the sub frequencies. Second, there's no need to put them in back of the band to wall load them. They can go off to either side, as not only are the subwoofer frequencies radiated omni-directionally, they're also not directionally locatable with our hearing. No matter where they are the directional cues for their content won't come from them, they'll come from the harmonics of the low frequency content which comes from the tops. If you're at all serious about PA the comments made here by Downunderwonder, Phil and myself are Gospel. Where low frequencies are concerned getting it right with PA is far more complicated than with bass amps, as nothing about how sound below 100Hz works is instinctive. You have to be taught. The guys who automatically put subs under mains split to either side have not been.

Lots of things aren't particularly noticeable if you're not able to make side by side comparisons. When you put subs under tops you not only lose boundary loading, by not have them close to a wall, you also can have cancellation notches when they're 1/4 wavelength out from a wall. If they're split by less than two wavelengths you will have power alley comb filtering. That's the science, and the science is never wrong. There are three reasons why people put subs under mains. #1: "That's how everybody does it". #2: "It's the only way we know to do it". #3: "We don't know any better way to do it/we don't know why it's the wrong way to do it". Now you know.

Replacing drivers is both a science and an art, and if you don't know what you're doing you shouldn't attempt it. For instance, the 250 watt rating of your cab is thermal. In most cases what limits a cab's output isn't the thermal rating, it's the mechanical rating. You could load it with a pair of 300 watt drivers that have no more mechanical capacity than what you have now. How would you know? You have to be an expert to make that determination. IMO if you want to get the most possible from a 2x10 and you're not an expert spend the money and get a Barefaced. They have the highest mechanical capacity available.

It shows how in the manual. Of course if you actually read the manual you run the risk of this:

I don't see the point either when there's plenty of PA oriented forums, but it seems more than a few members here seem loath to go to them.

Use ten loaded mains and either fifteen or eighteen loaded subs. You can't do it right with full rangers. Mains need smaller woofers for midrange dispersion and they have to be pole mounted for projection. Subs need to be on the floor, clustered not split, preferably close to a wall for loading. For small gigs leave the subs at home. You can't do any of that with all in one box PA cabs. As for owning the PA, if you do you can get gigs providing sound that will pay for it.

Assuming you're only running the board and not playing as well you've got to ride the sliders. If not then you've got to hire someone to do so.

Agreed. It seems out of place where it is now.

Where voltage conversion is concerned it's far more likely that it's done with dual primaries rather than multiple output taps. When there are multiple output taps that's usually to provide more than one voltage supply, as in one for the tube B+, one for the tube heaters, and in the case of hybrid SS/valve amps three for the SS voltage rails, +,- and earth. https://www.electronics-tutorials.ws/transformer/multiple-winding-transformers.html

I'm not overwhelmed by Lebihan's knowledge base: “If you think of where Sunn came from, that was an environment where amps just weren’t loud enough – the Kingsmen had the same issues with being heard as the Beatles and Stones. They just needed a louder amp, and that’s what the Sundholm brothers put together – a loud amp, using completely different technology". The problem everyone had in the 60s wasn't the amps, it was the PA. The PA wasn't able to be heard by the audience, and there was no such thing as stage monitors so performers could hear each other or themselves. Sunn amps didn't use different technology either, it was quite commonplace. The only thing that made them louder than most amps of the day was the ported cabs loaded with JBL, as I mentioned already. That advantage didn't last long. The 200S cab was totally outclassed by the Altec or EV loaded Ampeg V4B cab, which really was a folded horn, and the similar designs by Acoustic.

The last thing a marketing department will tell you is that you only need one cab. Their goal is to sell you as much as they can, not what you actually need.

That's the advertising claim, but how often do you see truth in advertising? About as often as you see an honest politician. 😄

It's possible that the power transformer has dual primary windings that will allow it. A schematic would probably show if that's the case. Singapore is a tech center, so finding someone knowledgeable shouldn't be difficult.

In case anyone wonders why a 9x10 the answer is impedance. If you use 8 ohm drivers you can't wire eight of them for an 8 ohm load, you may only get 1, 4, 16 or 64 ohms. You can wire a 9x10 as triplets in parallel, the three groups in series for an 8 ohm load. Or you can wire nine 4 ohm drivers for a 4 ohm load. That gave Ampeg more driver options than the 32 ohm they used in the 8x10.

It has to be for the look. The actual need for those died with the invention of the true electric bass specific ten and good PA.

I'd get the 212. The vertical driver placement gives wider midrange dispersion than a 410.

Despite the size it's not a sub, it's a bass guitar speaker. Used as a sub performance won't be great. https://products.electrovoice.com/binary/18BX Engineering Data Sheet.pdf Used for bass guitar it will work pretty well, although the midrange dispersion angle would be narrow.

Not really. At least 90% of what we know about loudspeaker design today was quantified by Harry Olson in 'Elements of Acoustical Engineering', published in 1940. The only major omission was Thiele/Small parameters, which date to 1965. Olson's work was very well known by Hi-Fi and theatrical sound manufacturers. I doubt one in ten musical instrument speaker manufacturers are aware of his work even today. I'd be surprised if even one in a thousand bass players are aware of his work, even though where giants of loudspeaker design are concerned he stands head and shoulders above most. FWIW the violin first appeared circa 1530. Stradivarius started making his circa 1660.

It's what's caused me to walk out of the last two concerts I went to. 😒

Hum could be power amp sourced, but not necessarily. A bad connection somewhere in the amp could be the cause, as could a blown component in the power supply. DC doesn't cause hum, because DC doesn't make any sound. Loud hum indicates AC that shouldn't be there, as in the case of a bad power supply.

Where bass cabs are concerned refer to an earlier post: the radiating surface of the 4x10 is wider than that of the 1x15, so its midrange dispersion isn't wider than the 1x15, it's narrower. Placing cabs side by side makes the radiating surface wider, so horizontal dispersion is narrower, by half. Vertical stacking also gets drivers closer to your ear level, so you hear the mids and highs better on stage. That's subwoofer placement, not bass cab placement. Subs don't radiate midrange, so side by side and vertical gives the same result.

I suspected that. The damping reduces internal reflections back to the cone. Those reflections arrive back at the cone at various degrees of phase, depending on the distance from the cone to the reflecting surface, and the frequency. They can cause both peaks and valleys in the speaker response. Valleys tend to not be particularly audible, but peaks are.