Ohms are a measure of resistance and the more ohms the more resistance yes. The amp will run cooler and easier with a 8 ohm verses a 4 ohm load because it is doing half as much work (half the current). This also means that your sub is only getting half as much current. The sub and amp should be carefully matched to get maximum safe output.

You should read up on basic DC electricity to better understand the relationship between resistance (Ohms), Voltage (Volts), power (Watts) and current (amps). I'm sure others here can suggest better reading but here is one site that explains it.
http://www.caraudiohelp.com/ohms_law/ohms_law.htm

The amp can only provide a given amount of voltage to the load (the sub). The higher the resistance of the load the less current (amps) will be supplied since the voltage is fixed. So as the resistance is lowered the current goes up which results in more power to the sub. This is good up to the point that the load is lower than the amp is rated for resulting in overloading the amp (or reaching its maximum current output capacity.)

Hope this helps,

JeffA

 

bingo on link - it words the realtionships so that I now get why the amp works less when ohms are high - I was thinking the amp would work harder to get thru the resistance to supply what the speakers need.

We think the sub went bad - I just hooked it up to another amp - same thing - it does not give deep bass - as I turn up the sub volumn it more or less goes from not much quality bass to an ugly thumping - it did not do this for the first day - this time replacing with a dual 2 ohm

 

All is well now with the install of a replacement jl - this time dual 2 ohm wired in series