Sparky Mark

An amp doesn't deliver an impedance, it sees that load which means it can deliver up to its maximum output. A 212 cab may be able to utilize more than the 300 watts if it isn't hitting its limits/maximum output already. Thermal ratings have little to do with volume, just how much heat the speaker can dissipate. A high sensitivity/efficient speaker will get loud with less power and then have to dissipate excess input energy as heat. A larger speaker should be able to move more air and dissipate more heat.

Noon for the EQ controls on all the Markbass heads I'm aware of is nominally flat. The VLE and VPF filters should be fully counter clockwise for nominally flat. You may be thinking of amps that have passive tone stacks where the noon position for bass, middle and high gives a mid scoop.

VLE= Vintage Loudspeaker Emulator which cuts the high frequencies more as you turn it up. The VPF may give you a slightly smoother mid presentation whilst boosting the lows and highs. A little of this might help if the mids are too present. With everything at noon and filters off the amp will be pretty flat but as Lozz said the speaker is designed to assist bass to cut through the mix. An outboard graphic eq might help.

A 300 watt solid state amplifier has the same power output as a 300 watt valve amp, it's the way that valve amps start to break up at their limit which makes them appear louder. A watt is a watt is a watt whether it's from a class A, AB or D or any other type of amp. If you EQ a 250 watt amp with lots of lows (and hi if you want to blow the tweeter too) and push the volume too high you will hear what is best described as a farting/distorted sound. You may also hear a clicking sound as the voice coil bottoms out on the yoke (back plate) of the speaker. Square wave clipped distorted output from amps can damage speakers capable of handling many times more powerful clean (sine wave) signals. If you hear farting or hard clicks from your speaker then immediately back off the lows and some volume. Once you've blown your first speaker it'll become common sense. My first (and last) was when I destroyed an 18" PA sub with a Sound City 120 and my Shergold Marathon bass back in 1977. Lesson learned.

You could easily blow a 400 watt cab with a 250 watt amplifier if you don't listen for distress.

I assume you mean that each individual speaker gets equal power, i.e., 66% going to the 410 cab and 33% to the 210 cab?

It's not just about the centre frequency of the EQ controls, it's also how much the frequencies either side of the centre are affected. Looking at the frequency curve of the LM3 low EQ shows it also boosts and cuts quite a broad range of frequencies.

Can these cabs be used together and get equal power to each of the individual 10" speakers? The 410 is available as an 8 or 2 ohm variant and the 210 is switchable between 4 or 12 ohms. Does an 8 ohm 410 plus 12 ohm 210 split the power equally?

The TTE have a different pre amp section which some users report as not giving them control over the low end as well as the LM2 or LM3 one.

I'm a Markbass fan and would recommend you find a LM2 or a pre 2012 LM3 or SA450. These are class AB power amps which have a certain fullness to their tone that the later class D don't.

Never had a fuse blow on any amp.

I have owned both ABM and MAG Ashdowns. The MAG differ in the pre amp stage being solid state only 5 band EQ with bright and deep switches. Both have compressor and sub harmonics. The MAG didn't have the much mis-used pre shape button which I think is responsible for some players thinking Ashdowns are wooly without definition. I actually preferred the clearer punchier MAG600 over the ABM until the latest ABM600 evo iv came along. The MAG heads can be found secondhand for next to nothing and the 600 is very powerful.

I found the concentric EQ pots far too small/fiddly and close together to adjust on the fly. Sounded good but did switch to protect mode at one (its last) gig.