GunpointMetal
Well-Known Member
So I have an amp that outputs 75 watts at 4 ohms. What kind of wattage will my cab see if its rated at 8 ohms?
Ohms to Watts Question
- Thread starter GunpointMetal
- Start date
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Blazerok
Well-Known Member
An easy way to find out is to take the lower wattage seaker on the cab and multiply it by the number of speakers.
I.E: you have two V30 (30w speaker) and two V60(60 w) in your 4x12 cab.
The total wattage of your cab will be 120 watts, not 180.
edit: i misread the question. sorry, dumb post. I think your answer is here http://www.marktaw.com/recording/Electronics/OhmsAmpsandSpeakers.html
I.E: you have two V30 (30w speaker) and two V60(60 w) in your 4x12 cab.
The total wattage of your cab will be 120 watts, not 180.
edit: i misread the question. sorry, dumb post. I think your answer is here http://www.marktaw.com/recording/Electronics/OhmsAmpsandSpeakers.html
GunpointMetal
Well-Known Member
thanks! so I guess I'm looking at about 37 watts into that cab....good to know.
Wrecklyss
Custom Speaker Cabinet Builder
A lot depends on the amp. It's RMS out to Impedance will most likely be logorithmic, not linear. On average, 8 ohms will see 33-66% of what a 4 ohm speaker sees. 37 is probably close, but there is a chance of variance.
VBCheeseGrater
not quite a shredder
That sounds like a generalization, judging from real world experience...
Some amps have an ohm switch - For instance, my 100watt tube amp doesn't turn into a 25watt head when i use a 16ohm cab on the 16ohm setting, and it sure as hell isn't 400watts @ 4ohms - if it's matched it should stay the same
My Peavey Bandit goes from 80watts at 8 ohms to 100watts at 4ohms.
what gives with the peavey?
Some amps have an ohm switch - For instance, my 100watt tube amp doesn't turn into a 25watt head when i use a 16ohm cab on the 16ohm setting, and it sure as hell isn't 400watts @ 4ohms - if it's matched it should stay the same
My Peavey Bandit goes from 80watts at 8 ohms to 100watts at 4ohms.
what gives with the peavey?
GunpointMetal
Well-Known Member
I have a PEavey Special 212 that is rated 120 watts at 8 ohms and 220 at 4 Ohms...must be in the power amp design?
VBCheeseGrater
not quite a shredder
^^^ That makes sense to me.
SpaseMoonkey
Well-Known Member
Wow how the heck do I word this...
I know in car audio they have all sorts of factors. They will list it as 100w but it is really rated at 50w RMS and the 100w is peak power. Does this apply to music gear as well?
I know in car audio they have all sorts of factors. They will list it as 100w but it is really rated at 50w RMS and the 100w is peak power. Does this apply to music gear as well?
GunpointMetal
Well-Known Member
I've noticed that with car audio..they like to tell you the peak output/input for some reason. My experience with musical equipment has been that unless its something off-brand or special design, the RMS output is usually whats given.
Wrecklyss
Custom Speaker Cabinet Builder
Car audio values are usually listed in PEP rating (very short spikes of power surges), professional audio and musician/home stereo is normally rated in RMS (Root Mean Squared) power, or the amount of power it can sustain continuously.
Watts are the product of the voltage and the amperage. With a speaker load, watts are calculated by impedance x amperage^2 or voltage^2 / impedance. How many watts are produced per impedance load depends on what kind of voltage and amperage numbers your amp produces. Tube guitar amplifiers use different taps off a transformer to provide RMS power for whatever speaker load you connect them to.
Watts are the product of the voltage and the amperage. With a speaker load, watts are calculated by impedance x amperage^2 or voltage^2 / impedance. How many watts are produced per impedance load depends on what kind of voltage and amperage numbers your amp produces. Tube guitar amplifiers use different taps off a transformer to provide RMS power for whatever speaker load you connect them to.
