#1
Looking at PA stuff again because I need one.

If I have a power amp that can put out at 2, 4, or 8 ohms, with more power being put out at each lower ohm setting;

And I have a speaker at 8 ohms with X amount of continuous power handling:

Is it safe or possible to output a lower amount of ohms from the power amp to the speaker?

Because I can't seem to find any speakers that are anything other than 8 ohms, and if they have to be matched or if they're incompatible, that seems to make the vast majority of poweramps kind of useless.


EDIT: Do the speaker ohms determine how much power the poweramp puts out? Cause I don't see an ohm selector on the poweramps I'm looking at.
Spin 'round carousel when your horse isn't screwed in.

My band:
Fractured Instinct
(For fans of Death/Groove/Prog Metal)

Ibanez RGA42E
Ibanez S420
LTD H-301
Ibanez RG520
Peavey Predator USA
Douglas Grendel 725
Line 6 Pod HD500X
Last edited by Offworld92 at Sep 21, 2013,
#2
Just keep the resultant speaker impedance over 2 and you are golden.

You'll lose just under 3dB every time you double the impedance, give or take.


Edit. I am assuming it's a modern SS PA and not an old Fender PA100.
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Last edited by Cathbard at Sep 21, 2013,
#3
So even if the speaker says 8Ohm, it really doesn't care?

This is the amp and speaker in question.

http://www.guitarcenter.com/Peavey-PV-2600-Power-Amp-104006242-i1145615.gc

http://www.guitarcenter.com/Peavey-SP-15M-15--Monitor-Speaker-105186167-i1459118.gc

EDIT: I would be running a pair of them, of course.
Spin 'round carousel when your horse isn't screwed in.

My band:
Fractured Instinct
(For fans of Death/Groove/Prog Metal)

Ibanez RGA42E
Ibanez S420
LTD H-301
Ibanez RG520
Peavey Predator USA
Douglas Grendel 725
Line 6 Pod HD500X
Last edited by Offworld92 at Sep 22, 2013,
#4
The general rule is more power than the speaker can handle. This is because it allows you more clean headroom, and also because the controls for most PA stuff is much more linear than guitar oriented stuff.

Most poweramps do not have an ohm selector. You just plug in what you have, and don't go under the manufacturer rated minimum ohms.
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#5
Quote by Offworld92
Looking at PA stuff again because I need one.

If I have a power amp that can put out at 2, 4, or 8 ohms, with more power being put out at each lower ohm setting;

And I have a speaker at 8 ohms with X amount of continuous power handling:

Is it safe or possible to output a lower amount of ohms from the power amp to the speaker?


the power amp is loaded by the speaker cabinet. however many ohms the speaker(s) is/are rated for determines how many ohms (how much impedance) the amp 'sees'.

so if an amp has an 8 ohm speaker hooked to it, it can output the amount of watts it is rated for at 8 ohms.

Quote by Offworld92
Because I can't seem to find any speakers that are anything other than 8 ohms, and if they have to be matched or if they're incompatible, that seems to make the vast majority of poweramps kind of useless.


you can find 4 ohms speaker cabinets out there, most are 8. but if you hook up two 8 ohm cabinets in parallel to one output (by daisy chaining the cabs or using parallel outputs on the amp) then the amp will see 4 ohms. most people do this with power amps.

Quote by Offworld92
EDIT: Do the speaker ohms determine how much power the poweramp puts out?


you can think of it that way, but it is not quite that simple

Quote by Offworld92
Cause I don't see an ohm selector on the poweramps I'm looking at.


you won't see one on a solid state power amp like that peavey, as mentioned earlier: however many ohms the speaker(s) are rated for determines how much impedance the amp operates at.

Quote by Offworld92
So even if the speaker says 8Ohm, it really doesn't care?

This is the amp and speaker in question.

http://www.guitarcenter.com/Peavey-PV-2600-Power-Amp-104006242-i1145615.gc

http://www.guitarcenter.com/Peavey-SP-15M-15--Monitor-Speaker-105186167-i1459118.gc

EDIT: I would be running a pair of them, of course.


Stereo Mode: 4 Ohms: 900 Watts RMS x 2
Stereo Mode: 8 Ohms: 540 Watts RMS x 2

that is the amp's output, if you hook one of your 8 ohm cabinets to one of those stereo outputs the amp will output 540 watts. if you hook two 8 ohms cabinets in parallel to one of the stereo outputs then the amp will output 900 total watts ( the power will be divided between the two speakers so each each speaker will see ~450 watts a piece)
punk isn't dead, it's always smelled that way.

"A perfection of means, and confusion of aims, seems to be our main problem."
-ae
#6


Awesome, thank you for the info!

That gear is just what looks best from GCs current stock price and power-wise - any cheaper alternatives that I might want to look for used? Assuming around the same amount of power of that stuff.
Spin 'round carousel when your horse isn't screwed in.

My band:
Fractured Instinct
(For fans of Death/Groove/Prog Metal)

Ibanez RGA42E
Ibanez S420
LTD H-301
Ibanez RG520
Peavey Predator USA
Douglas Grendel 725
Line 6 Pod HD500X
#7
Quote by Offworld92


Awesome, thank you for the info!

That gear is just what looks best from GCs current stock price and power-wise - any cheaper alternatives that I might want to look for used? Assuming around the same amount of power of that stuff.


not really, looks like your getting about as much bang for your buck as you can get.

i use a crown power amp, but they are a bit more expensive. i think that setup will suit you just fine.
punk isn't dead, it's always smelled that way.

"A perfection of means, and confusion of aims, seems to be our main problem."
-ae