ohm questions

[JacksonsMen]

ok, i know 8ohm+8ohm=4ohm and so on.......but i get lost in the 8+4, 4+2 sittuations

ive got an 8 ohm cab and a 4 ohm cab and an amp that isnt rated to go below 4 ohms....the amp has two separate speaker outs (stereo i assume) would i be safe to put the 4 ohm load on one output and the 8 ohm load on the other? just a thought

Hartke HA2500 amp before you ask

 

[KJung]

ok, i know 8ohm+8ohm=4ohm and so on.......but i get lost in the 8+4, 4+2 sittuations

ive got an 8 ohm cab and a 4 ohm cab and an amp that isnt rated to go below 4 ohms....the amp has two separate speaker outs (stereo i assume) would i be safe to put the 4 ohm load on one output and the 8 ohm load on the other? just a thought

Hartke HA2500 amp before you ask

8 and 4 results in 2.67 ohms... so, if it is a mono amp, that's a no-no unless the amp is safe to run at that level.

If it is a 'stereo' amp, then each cab will be independent... with one side of that amp seeing a 4ohm impedance, and the other side seeing an 8ohm impedance. That situation would be fine IME.

It will be VERY important to determine which of these situations you have.

Edit: Just looked at the website... the 2500 is mono... rated for safe operation 4ohms or above... so DO NOT CONNECT BOTH CABS....

 

[JacksonsMen]

thanks.....question, how'd you come up with 2.67.....rule of thumb or whats the equation?

 

[WillPlay4Food]

If running in parallel, use the following equation:

     1     
-----------
(1/r1 + 1/r2 + ... 1/rn)

Where r1, r2, ... rn is the resistance in ohms of each cabinet.

In this case you end up with:

     1     
-----------  = 2.67 rounded
(1/8 + 1/4)