# running 2 ohm speakers on an amp only rated for 4 ohm



## brandontw (Jan 21, 2012)

I totally spaced the fact that the component speakers I had laying around were actually 2 ohm speakers (JBL P660C)

I picked up an Alpine KTP-445u 4 channel amp to run them, with the intention of bridging it and running just the front speakers off of it.

Can I get away with running these 2 ohm speakers on this little amp if i bump the gains down a touch??


----------



## Lycancatt (Apr 11, 2010)

honestly? probably not. it will work sometimes but will not be happy as volume goes up so you'd do better to run it 2 ohm stereo and use the other channels to do something else. sorry for the bad news..


----------



## brandontw (Jan 21, 2012)

Lycancatt said:


> honestly? probably not. it will work sometimes but will not be happy as volume goes up so you'd do better to run it 2 ohm stereo and use the other channels to do something else. sorry for the bad news..


Well, I did the install this weekend, and went ahead and wired it up anyway...

I located the amp under the front seat rather than behind the dash for a couple reasons... better airflow in case it gets hot, and it will be easy to replace the amp if it fries, or doesn't perform well.

The install took pretty much all my free time over the weekend with running wires, installing HU, woofer-tweeter-crossover mounting, sound deadening, and interior disassembly/reassembly. 

So I didn't have a ton of hours listening/tuning, but it appears to be working out fine so far.

When you say it wont be happy at higher volumes, what should I be looking out for? Overheating or decreased sound quality?

I looked around a bit, and there seems to be some controversy on the actual impedance of this P660c component set. Some have said the it isn't really 2 ohms. I heard 3.6 ohms tossed around, but haven't had a chance to measure it myself because my DMM has gone missing, and my analog one isn't trustworthy enough to get a good measurement. I'll try to hunt down my meter and get a legit measurement before i put the right door panel back on.


----------



## diy.phil (May 23, 2011)

lol it comes with some JBL magic!! The specs on their website says 2 ohm and then their literature/flyer said "HIGHER EFFICIENCY. Like our GTO models, these speakers feature reduced impedance of 2 ohms for increased efficiency, while maintaining full compatibility with 4-ohm amplifier output stages, as on standard head units". You might be about ~ok there!!


----------



## brandontw (Jan 21, 2012)

diy.phil said:


> lol it comes with some JBL magic!! The specs on their website says 2 ohm and then their literature/flyer said "HIGHER EFFICIENCY. Like our GTO models, these speakers feature reduced impedance of 2 ohms for increased efficiency, while maintaining full compatibility with 4-ohm amplifier output stages, as on standard head units". You might be about ~ok there!!


Yeah. That piece of wording is a mystery. Especially since my hu manual specifically says it's not compatible with 1-3 ohm speakers.


----------



## rton20s (Feb 14, 2011)

DCR on the P660c set is 2.27 Ohms. For most manufacturers, they would probably call this a 3 Ohm nominal impedance. Also keep in mind that we do not have impedance plots for these drivers. What is the frequency range that the driver drops down into the lower twos? It is broad or fairly narrow? It very well could be perfectly safe to driver these with a bridged amp only rated for a 4 ohm load. Without more info, it is tough to say for sure.


----------



## bugsplat (Nov 7, 2014)

I'd test the drivers impedance first. I had a set of GTO's and they were marked 2ohms but when I tested them they were 3.7ohms. Ran them off a 4ohm amp for years with no issues. I think JBL might be pushing the marketing envelope a little here. I always test my drivers after they have been wired up. Lengths of wire will effect the resistance. Not much but if you are dorky enough to be here on this site your probably geek out off such details


----------

