Bill Fitzmaurice

At full power most amps don't put out twice the power into a halved impedance load due to power rail sag, but unless you've got a particularly anemic amp you'd seldom if ever push it at full power. At more reasonable levels the 6dB figure is spot on. The reason you get 6dB is because the amp puts out the same voltage into two speakers as it does into one. That results in doubling the system cone displacement, which gives 6dB additional output.

That's not how it works. How it does work is that by adding the second cab identical cab stacked on top of the first, with no changes to any of the amp settings, the output will go up by 6dB. That gives the same result as would quadrupling the power into the one cab, if it could take it.

Power Alley is most problematic in small venues, not large. Unless they're separated by at least 15 meters subs should usually be clustered, and wall loaded. You can't wall load a sub that's under a main that has to be in front of the band to prevent mic feedback. But to be frank your entire setup is AFU. Fifteens are for subs, not tops. Tops should only be run above 100Hz, and above 100Hz the only thing fifteens give you is poor midrange dispersion from cabs that are too big and too heavy. Then there's the matter of driver displacement and cab size. The demands of both double with each octave lowering of the pass band, so to match up with a pair of 2x15 mains you'd need at least eight 1x15 subs. It's just like an iceberg. What you can see above the water is the mains, what you can't see below the water is the subs. Of course one wouldn't expect that you'd make wholesale system changes at this point, but since you now have a pair of subs the next logical move is to get rid of the 2x15 mains in favor of a pair of 1x12 mains.

That's not an option.

https://mediadl.musictribe.com/media/sys_master/hdb/h4f/8849699995678.pdf

You still need a crossover. EQ doesn't provide the necessary roll off slope or depth of out of pass band attenuation.

A load that's too low in most cases will trigger protection circuitry that shuts the channel down, often resetting itself after the heat that caused it to shut down dissipates. If you don't have protection circuitry, rare these days, the amp could blow. You should not be using subs plus mains on the same channel . You should be using an electronic crossover and a separate amp for the subs, or one channel for the mains and one channel for the subs if the loads per channel aren't too low.

If you like the tone of your Ampeg add another. If you don't find something else entirely.

That capacity is thermal, not mechanical. The average cab has a mechanical capacity no more than half the thermal capacity.

It might be OK, since Gibson has no meaningful presence in the guitar amp market. If they'd been bought out by Fender you could expect the brand to disappear.

In semi-defense of guitarists they need to overdrive the speakers for tone. The problem is how loud that's going to be with even a 1x12, let alone anything larger.

You can use too much damping in a ported cab. An inch to inch and and a half is sufficient. I mainly use open cell foam mattress topper, which works better than acoustical egg crate foam at a much lower cost. Omni 10 was replaced by the Jack 10 in my lineup twelve years ago. I feel that if you can't carry on a conversation when in a small rehearsal place it's too loud. If you ask Pete Townshend's opinion on the subject, or any subject, his usual reply will be "sorry mate, I can't hear you!"

Roof insulation is the wrong material, but in any event a bare cab interior doesn't brighten the sound, if anything it dulls it. Without damping sound waves reflect off the panels back to the cone, causing peaks and dips, mostly dips, in the midrange response, and if anything a boomy tone in the midbass.

When you get the 'driver data fails integrity check' message it's usually because many data sheets only go to two decimal places, while WinISD goes to three or more. The resulting data may be off, but not by enough to be of any consequence. With a direct radiating fifteen I prefer 100L, with 40Hz tuning, otherwise you don't take advantage of what a fifteen can do on a low B, and it takes over-excursion down low out of the equation. If you don't do low B then I'd lean towards 50-55 Hz. When designed in the 80s there was no point in going larger with the TL606 when using the recommended low Qes EVM-15L. Other aspects of the TL606 that I haven't employed since the 80s is 3/4 inch construction, cleats in the corners where they're not required, and no panel to panel bracing that is required for maximum strength with minimum weight.

Not necessarily. The WinISD driver data base dates to 2004. Drivers introduced after that won't be there. Even those that are there may have incorrect specs. Back in 2004 Eminence had to change their voice coil former supplier, as DuPont stepped away from the Kapton former business. As a result the specs on most of their drivers changed, some slightly, some significantly. At that same point Eminence switched to Klippel Analysis, and remeasured the entire line with it. Over the years as I've modeled with Eminence one by one I replaced all of the old entries with the most recent. As for the TL606, it was a good enough box where first generation T/S designed cabs were concerned, but was obsolete even before EV stopped making the EVM drivers it was designed for.

That's not so much using a pick as it is having a new set of light gauge round wounds. Entwhistle got very close to that tone finger style, though you wouldn't know it after ham fisted mouth breathing producers were done. Listen to 'My Generation', one of the few tracks that managed to get past them with his real tone.

I'd run dual mono. There's no advantage to running one side only.

Is it worth it? From the standpoint of output, yes, because a 212 isobaric only plays as loud as a standard configuration 112. But you can't just pull one driver out of the 212 box and expect it to function optimally. You'd need to build two cabs, with the cab design compatible with the driver Thiele/Small specs.

You can use the gain to add some edge and grit to the tone. Set it with the master volume low at first, then bring the master up. The sound with a bit of overdrive is related to the sound of drivers being pushed too hard, but it's not the same. Overdrive sounds the same no matter where the master is set. Over-excursion distortion gets worse as you turn the master volume up, disappears when you turn the master volume down.

Seems logical, but the position of the knobs doesn't limit the output of the amp. All you can say with any certainty is that with the gain set at 4 it won't be as loud as when it's set at 6. How much power either will result in one can't say, as it doesn't account for the other half dozen or so variables. What one can say with certainty is that if you hear the drivers straining to handle the low notes you're approaching mechanical failure, so back off on the gain or volume or bass EQ or instrument output or all of the above.

I'm afraid not. With no changes to any of the amp controls a hotter input signal will result in increased power output.

If it distorts turn it down. The power required to do that is moot, as you have no way of knowing how much power you're pushing anyway.

The loop is used with line level effects, whereas instrument level effects are used before the amp input. By and large if it's a stomp box it's instrument level, if it's not it's line level.

Bass cabs are usually ported, but the ports have ducts that tune the speaker response for the low frequencies of bass. The size of the speaker has very little to do with the result, the size of the box it's enclosed in does. As for coping with a low B at anything above bedroom practice levels, you won't find anything either small or on the cheap. Even powered PA cabs loaded with fifteens aren't made to go that low, being intended to be used with subs for the lower octave or two.

Don't literally stuff the cab. You do that with sealed cabs, but not with ported. Ported cabs are lined with damping material to reduce internal reflections. Sealed cabs are stuffed to both reduce internal reflections and to lower the speaker Q. You can find out what that means and a lot more here: https://www.ht-audio.com/pages/SpeakerBasics.html