Dafaseles

@Ron36and @Kyblack76 are both absolutely right. when a manufacturer uses the term "max RMS", it's kind of deceiving. Can it handle 1000 watts? Maybe. Should you put 1000 true watts through it? Maybe not. When they actually have a specific measurement for "max", it's usually in reference to the thermal handling of the coil(s), but most of the time, wack companies slap a max value on the box to sucker in customers who are new to car audio and just see this huge number. Just worry about matching the RMS of the sub, to the RMS of the amp (say 500 watt RMS sub to a 500-700 watt RMS amplifier at the desired impedance), and setting your gains correctly. That will get you started on the right path. Stick around and ask questions. There's a lot of real knowledgeable O.G's on here. You'll learn a lot. I know I have

That rack is so damn clean!

My personal opinion, if the SIA is small enough, I would go with that.

Hella small. There might be smaller, but I don't know about them https://caraudiobargain.com/sundown-sdx-1200-1/

If you decide to go lithium, you should get an external regulator for your alternator. Read this carefully. Especially the part about charging voltages

Not even by turning the head unit volume all the way up? Edit-i just read it again. Your subwoofer level is at 0? I've read in some instances, a sub level of 0 is actually only 50%. Try turning your sub level up, and retry setting your gains. See if that helps. The great thing about the DD-1 is it'll detect any distortion. So, if you torn up your level, and get no distortion, then you're introducing no distortion, so you're not amplifying any distortion.

If you smell it, you're clipping the shit out of it (or reaching it's mechanical limits, or something asking those lines. Either way, your coil is burning). It could very well be ruined already. What subs are they? What amp are you running? Any electrical upgrades to the vehicle? What size and tuning is the enclosure you're running? What are the crossovers on the amplifier set to? How did you set the gain on the amp(s)? All these could be contributing factors to why you're smelling your voice coil(s)

It will blink sometimes. It's the DD-1 stepping up the level or something (I can't remember exactly what it's doing. The DIY audio guy on YouTube talks about it on his video about the DD-1 and DD-1+. It's normal). Keep increasing until the light stays on. Then knock it back.

I don't know if I told you, but after all that, I spoke with Tony from mechman. For GM trucks, they make a whole bypass setup that also will fool the charging system into thinking the VRC is still in control. No battery light on the dash, and a constant 14.7v from the alternator. I had to order a new alternator though. A 2 pin input instead of a 4 pin. With the max charge of the Cyber 12k betting 14.8v, the constant 14.7 will be way safer than the fluctuating voltage from the VRC.

My truck has one a well. What i've learned is that it's important to not send grounds to the engine block/ alternator without passing through the "ring" first. You can ground to the frame, but the frame grounds should come back up to the negative battery terminal, then through the ring, then to the block. If you pass by the ring, it can cause havoc on the system. What actually happens? I don't know. Just read "don't do it" lol.

Steady voltage at night might have something to do with the headlights and taillights. At night, the automatic lights will turn on all the lights needed for night driving. In turn, the voltage controller says "well then we'll need more voltage", and at accordingly. Try turning your lights from automatic, to just flat out on during the day, and see what results you get.

Damn, another windshield sacrificed to the bass gods

So yeah, you're not pulling much, but those high end JL amps are hungry. That alternator with even your current battery is more than enough. 1 big 3 will be plenty right now. Though 2 runs of 1/0 from your alternator positive to your battery won't hurt. I say that just to be a little overkill, so you won't ever exceed the rated amperage of the cable. Mechman rates their alternators at 1800 RPM. So at 1800 RPM, that alternator can put out 400ish amps (I have one as well) and at 800 RPM (about idle) they usually put out around 200ish amps. So that can kind of give you an idea of how much current that alternator will be pushing out the majority of the time while driving. Good 1/0 OFC car audio cable is usually rated around 350 amps. I always tend to try and steer people away from using CCA car audio cable because, basically, it's cheap, and can't handle the amperage OFC can. Welding cable is pure copper, which in my opinion, is just fine to use in daily driver systems, with some asterisks. Car audio cable is oversized, so it can handle more. Welding cable uses the AWG standard. So 1/0 welding cable is usually rated around 300 amps. Also, depending on who you ask, the cable sleeve of welding wire can be less protective than car audio cable (I have never tested this claim). Some say OFC is even more resistant to oxidation than pure copper (I've never tested this myself either). If you ever get to put in a second HD1200.1, then I would recommend dropping coin on 2 high output AGM batteries. Replacing your current battery and your truck has space and kits to add a second battery under the hood, so finding space shouldn't be an issue. That should keep both fed just fine. The reason I like those type battery terminals is, at least for me, it was easier to attach all the ring terminals I needed, and liked a lot cleaner, than stacking everything together on a "pole".

It's a fun hobby, but one that can get expensive, just like fixing up a car lol. By industrial cable, do you mean welding cable? As far as getting into it deeper than you expected, you do it right the first time, you won't have to worry about anything in the future. If you don't mind me asking, what gear are you running? Amp, and subs specifically. 2nd battery? In the interest of keeping things clean looking, I prefer something more like this https://skyhighcaraudio.com/copy-of-sky-high-car-audio-6-flat-battery-terminals/ Or input style of you prefer https://skyhighcaraudio.com/sky-high-car-audio-sae-4-0-xl-2-0-xl-or-1-0-4-input-set-screw-battery-terminal/ They make different sizes and different configurations. This is just to give you an idea. And to expand on what @TheBKGsaid, I think he's referring to something like these https://skyhighcaraudio.com/sky-high-car-audio-dual-1-0-to-1-0-gauge-inputs/ They also come in different sizes and configurations as well

What battery do you have under the hood now, so I can see a picture of what you're referring to. Yeah, that 8/0 is hood, and expensive. I thinks it's $1000 for 50 ft lol. I was just throwing that out there because I thought it was interesting. 2 runs of 1/0 is rated higher than 1 run of 4/0, so you can go wrong with 2 runs of 1/0. Just of you REALLY wanted to have just a single run, 4/0 will handle it.