Cab Impedances

[RacerX]

OK! Let's see a pic! (I could use some more laughs today!)






(gets pic of funny cat going LOLOL ready)

[jackson1]

Oh man, we're ruining James' thread, but what the hey it's 2 late... i'll be back..

<Henrik going to the big computer database..>

[jackson1]

[RacerX]

[MountainDog]

An impedance rating of a speaker varies with the frequency being played thru the speaker. The impedance term we usually talk about is 'nominal impedance' and represents the impedance over the majority of the bandwidth of the speaker.

For guitar applications, we are normally concerned with either 4 or 8 or 16ohm as options. A quick way to check this is by measuring the DC Resistance of the speaker coil with a simple Volt/Ohm meter (Radio Shack has them for like $20). Note that DC Resistance of a coil is usually less than the rated impedance, so an 8ohm impedance speaker will usually read 6 ohms on the meter. (The rule of thumb is to multiply the meter reading by 1.3 to get impedance).

To measure a cabinet, simply plug in a speaker cable to the cab input, then put the meter so it will read 0 to 20 ohms, then put the black meter lead on the barrel of the jack of the other end of the speaker cable and the red meter lead to the tip of the jack, and check the reading on the meter. If you see 3-4 ohms then its a 4 ohm cab, 6-8 ohms, then its an 8 ohm cab, 12-16 ohms, then its a 16 ohm cab.

Here's a link that explains reading with the meter as I mention above (see the last paragraph of page 1).
http://www.transparentsound.com/measurements/Tomi_Engdahl.pdf#search='speaker%20impedance'

[Chad]

Good info MountainDog. If you are going to a lot of different clubs with a lot of different cabs, then I would definitely recommened getting a multimeter and checking them before you hook your amp up. I think everybody should own a multimeter anyway as they can be handy for lots of other tasks as well.

[Mr White]

Mountain dog - Thanks a lot! Thats the perfect answer!

Jackson 1 - Get your shitty cabinets off my thread!!!

I never mind thread hijacks it gives me something extra to read!

Thanks guys!


James

[sl2lover]

Ya when I first got mr Rivera KR100/4x12 cabinet i was running it at 4ohms. Well the 4x12 is an 8ohms in mono. Well my amp would occasionally shut down and would freak me out! Well thank god it has an automatic shut off built on when it starts to overheat! Otherwise I woulda fried the thing!

[MetalMedal II]

Note that DC Resistance of a coil is usually less than the rated impedance, so an 8ohm impedance speaker will usually read 6 ohms on the meter. (The rule of thumb is to multiply the meter reading by 1.3 to get impedance).

I figured this out the hard way a couple years back when trying to figure the impedance of an unknown speaker. Using my own speakers as a reference, I was shocked to find mine measuring at 6 and 12 ohms!

[JCTommie]

Someone mistook the left cab for a toilet?

That's like glue from the tolexification process. Every Marshall I have is like that on the inside!

Mojo amp stuff page does a good job of explaining the dealio.
GO ON CLICK IT>>>>CLICK IT!