i hereby call into fuse theory

I may need correction here, but Im stating to call into question the "rule of thumb" for car audio fuses. I was brushing up on the words of wisdom from the folks on the internet and came across the usual formula for finding appropriate fuses. RMS for this amp is rated at 1000W (arc audio 2500-cxl), the manual states that I need a 150A fuse, the peak power draw is 135A and the math also matched up (1000W*2/3.8= 145). Now when I put this system in nearly 10 YEARS ago, I didn't really car about "theory" so I used the fuses that came with the blocks. Yesterday, I discovered that the fuses in both the inline fuse near the battery and the fuse at the distribution block are.... 60A. 60A?! Is ignorance bliss? Ive been running a 60A inline fuse and 60A amplifier fuse on this RMS 1000W amp powering 3 Jl Audio 6ohm subs (for a total of 4 ohms) for 10 years, and probably the original alternator without any problems. Do I play it loud... um, yes. Very. Do I listen to demanding tracks? Um, definitely. If my logic is correct, I call into question the "rule of thumb", since the only was I could get even a 60A draw from this amp would be to bench test. So, I dunno man. Ok, lemme have it

Sorry about the typos, trying to do this from my phone. Ugh. *I hereby call into question "fuse theory" *1000W*2/13.8= 145 *the only WAY I could get 60A etc

I don't see how it relates to fuse theory. 150A or thereabouts is the correct size for a 1kW amp. And those fuses are not there to protect the amp, but the distribution to the amp. Maybe the amp has not put out full power for long enough to blow those fuses? A 60A fuse is likely to handle a 10% overload for 4 hours (midi type bolt in fuses) & 50% overload = 90A for 90 seconds. Assume your amp is 1kW out @ 14.4V with 80% efficiency, hence input current = 1000/14.4/0.8 = 87A. Hence a 60A fuse should handle a 90 second "burp" (assuming full input signal). Design wise, that 87A load should not load the fuse by more than 90% tho usually 70% is a typical max loading, hence the fuse should be 87/0.7 = 124 => 125A minimum. If the rated 1kW is at the old standard voltage of 13.8V, then 87A becomes 91A - no significant difference there. However, such amps use SMPS which should mean that the lower the input voltage, the higher the input current - eg, at 10.5V it should pull 120A (compared to 87A or 91A) and hence a 170A fuse, or a 150A fuse with 20% margin (ie, running at 80% of fuse rating instead of 70%). I don't know if the above accounts for the max stated draw of 135A and hence the 150A fuse or if it's an efficiency issue. Despite SMPS, many amps specs I have read state reduced output power with reduced input voltage - in fact many seemed to behave like perfect resistors else constant current loads (ie, output power varied either to the square of input voltage else in direct proportion to it - neither of which IMO is consistent with SMPS design nor behaviour...). Have you ever measured the output power or input current of your amp at full volume? I don't think many people could tell the difference between 900W output and 1000W (maybe even 800W & 1kW...).