truck stutters when bass hits

So what do I do?

Try using one battery for the truck, and 2 for the amplifier.

i am an idiot wrote: Try using one battery for the truck, and 2 for the amplifier.

I have. Nothing has changed anything. Gone from stock to now 3 batts 2 alts and frustration.

voltagexdt wrote: So what do I do?

Get a bigger engine. Disable the 2nd alternator when idling (that means (say) 12.5V battery voltage for the amps instead of the higher alternator/charging voltage). Increase idle speed (when the amp is on - ie, an air-con idle speed booster {enable in ECU if appropriate and connect SCU sensor}). Various solutions.

voltagexdt wrote: I did some research and numerous forums show that the field or excite wire needs to be connected to 12v switched. So I assume that's why stinger said to link between them

That Field has nothing to do with connecting their regulators - you'd have to have a very old vehicle (like mine) or a non-OEM alternator for that to have any relevance. (The regulator looks after the field winding.) Modern alternators with integral voltage regulators - excluding ECU-interacting DP etc alternators - are usually single-wire - ie, a charge Light circuit called D+ on most single wire alternators or L on 2- or more-wire alternators. (We don't count the heavy +12V often B or B+ to battery +12V nor the alternator GND as wires.) A second wire is usually a Sense (S) wire that goes straight to the battery +12V terminal (maybe via a fuse or resistor) - eg, common "SL" type regulators/alternators. Rarely is a third "I" for IGN +12V/on used, but they do exist - eg, SIL type alternators (Nippon Denso, some Hitachi etc). Hence maybe your 3rd wire can be commoned, but NOT the other 2. If one the other two, either you are commoning the D+/L circuit which risks a +12V to GND short that may ruin both alternators (or rather, their voltage regulators), or you are commoning both Sense circuits to one battery which means eventual death to the 2nd battery(s), and maybe a fire or explosion seeing as it's an Optima. (And with TWO "permanently" paralleled Optimas on that #2 alternator output - man, you don't even need the alternator for the fire from 2 of those in thermal runaway...) Find out what wire you have paralleled before you wreck your alternators, or - maybe later - allow your vehicle to burn to the gnd.

i believe each field wire needs to go from each alternator to whatever batteries that alternator is trying to charge. as it stands now, both alternators are only charging when they sense your main battery voltage dip, which is almost never because the amp is not hooked to it. so this is probably causing a bad voltage drop at the amp's batteries, i dont know what else you have connected or how, but maybe your rear audio batteries are finding a way to pull power from the main when they drop voltage. and since one alternator would have trouble charging all those batteries it might cause your trucks voltage to drop enough to make the truck run badly(weak spark plugs). thats my theory... solution, make sure every piece of audio equipment is getting power from your extra batteries so that there is no possible path for the two systems to bleed into each other. this means the radio, any eq's, line drivers, crossovers, capacitors, etc all need to get their power from your audio batteries. you need to run a fresh field wire from your audio alternator to the audio batteries and it needs to be ran through a relay that is switched from the ignition, this way there is only a connection when the truck is running.

Thanks for the advise but so far no one is really paying attention. It's a 91 chevy k1500. The alternator has a plug with 1 wire in it. It is the excite wire. Nothing more. It's not a sense wire. Furthuremore I'm getting 14.8 volts from both alternators.

You say you mounted the second alt on the A/C mounting studs. I assume it's being driven by the same serpentine belt as the OEM alt? If so, then a big load on the audio alt WILL put load on your engine, cause it to slow momentarily and could cause other issues with the OEM alt. Or the belt could be slipping. In any case, the issue is your system is placing a large load on the alt. That's all. The only way to "fix" this assuming it's all hooked up correctly is to live with it. It's one of the down sides of trying to run a large audio system. Set the engine to a higher idle RPM and make sure all your belts are 100% properly installed.Support the12volt.com

voltagexdt wrote: ...a plug with 1 wire in it. It is the excite wire.

That excite wire is what many call D+ or L - the charge light circuit - often called 'I' in chevy etc sources. Chevy's 'A' or 'A+' is akin to S = Sense; Chevy 'S' is the Stator's star centrepoint which is an indication of the alternator charging - ie, it turns on the Field Relay hence turning off the charge-Lamp (I); And F = F = rotor field - its current varies in order to maintain the required (say) +14.2V at the battery. But with modern integrated or internally regulated alternators you don't normally have access to the Field nor Stator. However I was even more confused than those that wrote the web refs I saw. Many contradict, and others were ambiguous enough to be inconclusive (ie, whether charge-Light I output can be connected to the Ignition, though older external electromechanical regulators often could be without direct damage)... I'd have to work out what's what from appropriate wiring diagrams... But normally a single extra wire means it's a D+ aka L. For some alternators, there must be a resistive connection to IGN +12V to guarantee rotor excitation (whether directly or via intermediate regulator circuitry) and that tickle or trickle current is supplied through the charge light or resistor or other bulbs connected to IGN +12V. But many L/D+ terminals supply +12V when charging (and thence turn on {electric...} chokes or fuel stops or fuel pumps or battery isolators). Some D+/L terminals are merely the centre (30) of a 2-way or SPDT relay with 87 to GND and 87a to Alternator +12V output terminal (aka our B/B+). You do not want to connect those D+ outputs together!    But unlike integral regulators, many externally mounted electro-mechanical voltage regulators could tolerate that - but who'd use an e-mag vreg these days? Even if external, it could be electronic. But for modern vehicles with ECUs and user-added PCs & big audio, internally regulated is the way to go. I would connect the 2nd alternator's wire thru a 12V 2W or 3W bulb to IGN +12V, else see if it already has a ~15 Ohm to IGN +12V. If it extinguishes once the engine is running, then the alternator is charging. (Or rather, when it is lit, it is not charging {sufficiently}.) And if it is a Sense wire, the above will not do any harm. But you should always check each battery's 'rested' voltage (to preempt failure) and each batt's charging voltage (eg, normally not above 14.4VDC long term, and usually above (say; preferably) 14.0V - 14.2V under any load and any speed. However Optima specify different voltages and charging regimes (below whatever max temperature) so you can align your voltages to them. And hence the advantage of the S = Sense circuit (ie, typical 2-wire S & L alternator) so that even with the alternator up the front and battery down the back, the alternator can regulate its output to provide the proper voltage across the battery terminals (ie, 14.2-14.4V). But a Sense wire almost always be connected to the battery else over-voltage can occur (typically limited to ~15.5V on Jap SL & SIL type alternators).