So I installed my new JL HD750/1 amp in my Integra and I can't turn it up without blowing the fuses. I mean I can listen to it pretty loud and it's fine but if I really want to turn it up the fuses just go. I'd say anything over 70% power and it will blow the fuse within a miniute. I'm using the reccomended 60amp fuse. The speaker is a RE audio SE 12" wired at 1ohm. The JL amps are only stable down to 1.5ohms but with all the wirings resistance added it works out. When I measure the resistance with my multi-meter at the speaker leads out of my box I get 1.5-1.6 ohms, so I figure this should be perfect for the amp.

Any ideas? It's pissing me off, as soon I turn it up and it really starts pounding and sounding good it cuts out. I know this amp/sub has so much more in it than what I'm getting out of it right now.

 

How big is the power wire?

 

4 guage. Grounded out to a seatbelt bolt under the back seat.

 

You're using a 60 amp fuse for 4 gauge.. I fine that too less. I would use atleast 100 amp fuse.

 

wire to 4ohms.. i think the 1.5 is best suited for the JL 3ohm series not a dual 2ohm wired to 1

 

Yea but 60amp is wha JL Audio reccomends for this amp. I highly doubt JL would tell you to use a fuse that can't keep up with the amp.

It shouldn't matter, the amp puts out the same RMS from 1.5ohms up to 4 ohms. What would it change if it was seeing 1.5ohm from a 3ohm sepaker or 1.5ohm from a dual 2ohm? The amp still sees 1.5ohm, the speaker shouldnt matter.

And I would wire it to 4ohm, but once you add in that extra .5 ohm in all the wirings resistance I'll actually be getting 4.5ohms which will be to much for the amp and not allow me to get full power. I tried it this way at first and this is when I realized I would be a .5ohm over whichever way I wired it. So I switched to to wire it at 1.5ohm and it made a pretty big difference.

 

even though the mm reads your sub at 1.5 it doesnt mean the amp is actually stable at 1.5 flat.. usually tolerance of wiring is already figured in when the manufacturer rate these amp
although your amp spec claims 1.5 ohm stable.. the amp itself is made to compliment jl 3ohm subs along with dual 4 paralleled and some two sub configurations that are within its capabilities... so... try running a friends dual 4 sub wired to 2ohm @high vol if it still pop the fuse then my bad...

 

Well since your blowing fuses.....maybe you should switch it back and see if they still blow.

I'd suggest looking at all the settings on the amp. Where is the bass boost set? the gain? the filters? all that stuff, and make sure they're set up right.

 

what you may not know is speakers are a resistive load....the impedance changes with tone and volume. sure your amp is stable to 1.5 ohm but for how long? Well your fuse blowing is one way of telling you " I am having an issue here...". They way i describe it is like being stopped at the light. light turns green,you stomp on the gas revving it up to 5k ,shifting, acelerating then stomping on the brakes at the next light only to repeat the cycle. Not good for your car...or your amp.

 

So I called JL up and you guys were right, it was too low of a load for the amp. What sucks though is when I wire it at 4 ohms it is seeing a 4.5ohm load which really seems to effect it's performance. There is no way I'm getting 750W out of that amp when wired like that. It's only a 600W RMS speaker and with the gains almost all the way up it doesnt really make the speaker move all that much. Seems underpowered even though it should be getting like 150 more watts than it's RMS. So something is definitely not right.

 

I would get rid of that 2ohm DVC speaker and get a 4ohm DVC speaker and wire it for 2ohms.

 

The JL Audio HD750/1 uses a regulated power supply it's output, [RMS watts] is the same, [1x750W RMS] into 1.5-4 ohms @ 11-14.5VDC.
http://mobile.jlaudio.com/products_a...hp?page_id=252

Lower then 1.5 ohms will over heat amp, higher then 4 ohms will result in lower output.

You may also have a current problem, not enough current getting to the amp because of connection issues.
What type of fuse and fuse holder are you using?
How are terminals connected to the power and ground cables?
How long is the ground cable?
Have you "beefed up" the batt. to chassis ground? 94

 

The fuse holder is a kicker I think and the fuses are the AGU ones.

The terminals were crimped on and blowtorched/soldered.

Ground cable I'm not exactly sure about because I would have to remove my back seat to measure, but it is not long. Amp is mount on the back of seat and the ground is connected to a seatbelt bolt under the seat, so whatever that distance would be.

And I havent beefed up any factory grounds.

 

You should replace the fuse with an ANL fuse w/post type fuse holder, AGU fuses are not very good for passing current, [high resistance].

Run a 4ga ground from the batt. to the cars chassis, shock tower studs make good ground points, or any point on the frame rail.

I would pull the rear seat and make sure the grounds ring terminal is making direct contact with the cars floor pan, all dirt/paint must be removed down to bare metal. 94