I dont understand how so many others run their amps at half ohm even though they're not stable. Do they not have that kind of protection circuitry or do they just turn up and fight against the protection feature?
.....Should I fight the protection circuitry?
The people that I know that truly and safely run .5 ohm have expensive amps and run a ridiculous amount of electrical now, like multiple alts and a lot of wires and high voltage charging. A lot of these people’s dc voltage never fluctuates much.
The box type is related to electrical flow in the amp, with the way the box controls the cone movement and therefore how the coil moves through the magnet guass/field, which then changes the impedances your amp sees at relative frequencies. Box size, port size, location, type of box, so many things can factor into electrical control of the amp over the woofer, due to how it changes cone movement across frequencies.
So, some people can run .5 ohm, or I even know people who’ve competed at .25 ohm, because they have expensive amps, super expensive/extensive electrical setups with huge capacitance of higher voltages (like charging at 15ish volts), and the box is designed to help control impedance spikes and dips, especially playing music, which is a huge factor in stressing your amps.
How your sub moves in and out directly changes the active resistance against electrical flow in the woofer at that specific point of movement. Audio is a bunch of small things that all add together that allow you to maybe be able to run .5 ohm.
I ran 1.4 ohms on 2 strapped amps, so 2 ohms is like 1 ohms, and it would cut out rarely, but always during a large frequency changes, like a sweep or punch or just low to high note; those are the things that seem to wildly change impedance, which wildly changes the fluctuating stresses with the amps. One key thing to sense impedance from the driver’s seat is to always have an accurate reading of a dc voltage meter plugged directly into the amp 12v terminals. Voltage drops are heavily related to woofer movements and the struggles your amp faces from impedance changes.
Like if your woofer unloads playing 25 hz below the tuning of a ported box and is over xmax or high xmax just flopping around, that can be like jackhammering your amp with large impedance changes over and over, and you may see wild fluctuations in dc voltage. When I design walls or certain high powered systems, I tend to find out the electrical situation before I even start designing, because the nature of the box needs to match the strength of the electrical system, so that the electrical system can properly control the woofers at full volume. It’s just like higher quality amps will allow you to play further away from tuning frequency with ported, where lower quality amps wouldn’t be able to keep the woofer under control, electrically.
So, there’s lots of reasons. You just have to understand what you’re aiming for and what you truly want out of your system.