#1
I've been using my JCM900 4502 combo as my main amp recently and have a question about driving another cabinet with it. I have a VS4x12 slant cab rated at 8 Ohms.
If I use the combo's speakers and the cabinet together, do I need to switch the speaker setting over to 4(16) or leave it on 8 Ohm?
Thanks in advance.
#2
IF The combo speakers and the cabinet are different ohms then you cant use the cabinet. if they ate the same its ok.
Gear:
Fernandes Revolver Elite
Schecter C1 Exotic
Schecter C1 Classic
Peavey JSX head
Hartke 4x12 cab
Boss GT-8
BBE 362 Sonic maximizer
#3
*are
Sorry its early
Gear:
Fernandes Revolver Elite
Schecter C1 Exotic
Schecter C1 Classic
Peavey JSX head
Hartke 4x12 cab
Boss GT-8
BBE 362 Sonic maximizer
#4
If both the cab and internal speaker are 8 ohms each, then you'll have to switch to 4 ohms to connect both, since they will be connected in parallel.
Guitars: Custom Lado Earth 2000-3, Custom ESP Explorer, BC Rich KKV, Gibson LP Studio, Greco SG, El Degas Stratocaster, Agile AL-3000, LTD EX-351

Rig:Marshall JVM410H + Marshall 1960A, Boss Noise Suppressor
#6
Quote by Gutch220
how many ohms are the internal combo speakers running at?

8 Ohms.
#7
yea, so just set your amp to 4 ohms when usung two 8 ohm cabinets.
If you ever get confused, just use this formula to figure out what the ohms should be for a couple cabinets.

R is Resistance

(R1 x R2)/(R1 + R2)= ohms you should set your amp to

i.e.

8x8/8+8= 4 ohms
#8
Quote by Gutch220
yea, so just set your amp to 4 ohms when usung two 8 ohm cabinets.
If you ever get confused, just use this formula to figure out what the ohms should be for a couple cabinets.

R is Resistance

(R1 x R2)/(R1 + R2)= ohms you should set your amp to

i.e.

8x8/8+8= 4 ohms

Gotcha, thanks
#9
The formula is even easier than that. Technically, that's the correct formula for calculating impedance in parallel. In the case of guitar amps, you can't mix and match cabs of different impedances. You have to match them. So whenever you match a pair of speakers (or 2 cabs, a speaker and a cab, etc..), the total impedance is always 1/2 of the impedance of the one speaker / cab.

2 x 16 ohm = 8 ohm
2 x 8 ohm = 4 ohm
2 x 4 ohm = 2 ohm (not many amps will handle this)
Guitars: Custom Lado Earth 2000-3, Custom ESP Explorer, BC Rich KKV, Gibson LP Studio, Greco SG, El Degas Stratocaster, Agile AL-3000, LTD EX-351

Rig:Marshall JVM410H + Marshall 1960A, Boss Noise Suppressor