Hi guys,

I am running an MTX Jackhammer JH404 (RMS 100x4 @ 2Ohms) to power my 4 Infinity Kappa Components 680.9CS (RMS 90W @ 2Ohms). I am using very large wire not only to feed the amplifier but to feed the speakers, so the amp is definately seeing 2Ohms on each speaker.

My problem is that on hot days, the amp will cut off if I play my music loud for too long (20 min or so). I'd rather not buy a more powerful amp, so I thought I'd modify this one. I'm an electronics engineer, so it shouldn't be a problem. What do you guys suggest? I was thinking of removing the fans and replacing them with ones that have a greater CFM airflow?

Thanks!

 

where is the amp actually installed, where is the amp grounded

 

It's in my trunk. It has adequate ventilation (about 6in on each side) and is mounted to the floor. It's grounded with the largest possible wire (4AWG, I think) about a foot away on a sanded hole I created. The install is great, it just runs hot on the 2Ohm loads.

 

I would definitely go with better cooling. Those MTX amps aren't exactly the highest quality. The 4 gauge wire should be plenty on that small an amp. I had a MTX road thunder amp that liked to overheat and I slapped an 80MM 12 volt computer fan on the case, worked like a charm.

 

Infinity speakers marketed at 2 ohm loads generally present 2.4 to 2.6 ohms of DC Resistance, which means they are closer to 3 ohms nominal. If they were a true 2 ohm driver, I would expect the DCR to read at 1.x ohms.

 

That DMM honestly might not be real reliable for anything other than voltage... When I just had my cousin's Craftsman I always had to borrow the other techs' multimeters when I needed to check resistance, theirs and my Snap-On one always give different readings from what the Craftsman one does... There are some things you should buy Craftsman and some you should buy Snap-On... Just saying.

 

My Craftsman measures resistance within 5% of a family member's calibrated Fluke. The Craftsman may not be a precision instrument, but it is close enough to measure resistance on an alleged 2 ohm driver. FWIW, his Fluke meter measured 2.5 ohms on the same speaker.

Now, if I were measuring resistance in fractions of an ohm to repair something, I would borrow the Fluke!

 

Back to the original question...

A trunk is just a hot box. Find a way to duct cool air into the trunk, and also find a way to exhaust the hot air from the amplifier out of the trunk.

 

i guess just add cooling fans somehow, the reason i asked about where it is mounted is because some dont know that when mounted upside down the amp will run hotter

 

the 2 ohm infinities are the problem. You might be able to help it cool a little better but even with a new amp it will run hot with those speakers. You might be able to help it cool a little better but I just avoid those speakers to avoid these problems