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Forum: General Discussion

Topic: Speaker Impedence Question

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Can any 8ohm PA grade speaker run safely at 2ohms if you ensure the RMS rated output is adhered to?
 
Inviato Fri 01 Feb 08 @ 6:07 am
You should not have any problems with the speaker if it is receiving the right RMS input regardless of ohm load... it is the amp you have to worry about. Many amp manufacturers will state huge power amounts at the 2 ohm point but I would not go there. I have taken Crown amps (Macrotech - touring grade) to stupidly low loads as an emergency measure, but I would not intentionaly go below 4 ohms.

What speaker and amp combination do you have in mind?
 
I was thinking of running 3 pairs of 8ohm speakers all rated at 300w RMS (2 pairs which are bins and the other pair mids) of an amp which the manufacturer states runs at 2ohms stable generating 975w per channel.

I was then looking to run a pair of 250w RMS bullet tweeters of an amp which generates 300w per channel @ 8ohms

I was planning on using a cross over to seperate the frequencies to each amp.

So in theory this would give me a maximum safe output of 1800w for bass & mids and 500w of tops (2300w in total)

 
As perviously stated its not the speaker you should worry about
it's the AMP...

General rule: 2 8 ohm speakers connected in parrallel = 4ohm (roughly) 3=2
if you connect them in series it will double the ohm
So some people use tricks... 2 8 Ohm speakers in Series = 16 then 2 more connected in Series but connected to the original 2 in parralel
= 8 ohms (I confused me too, hahaha)

see this linky http://www.audioholics.com/education/loudspeaker-basics/loudspeaker-impedance-series-parallel-connection-basics


Even tho the creator say it will run safely at 2ohms, the lower the ohm the more power
but the drawback is.. The Amp works Harder and HOTTER!! so you can't play for longer periods

I would not run a amp below 4 ohms.

Also remember more speakers are blown due to underpower not overpower
A speaker that states 300Watts is actually 600Watts Program and about 1200Watts Peak
you really want to provide power as close to the PROGRAM Rating as you can get. (500 - 600 Watts)


Thanks,
DJ SMG
 
Can you give me very specific speaker and amp models? (Need complete name and model number). Do you already own or work with these are they something you are thinking about purchasing? I can give you a more educated answer with all the specs.

Be sure to take a second look at the previous posters response and link... good info.

haz0rd - I get confused too... I hate formulas! 20 years of sound reinforcement experience in a simple general formula... (one amp + many speakers = bad)
 
haz0rd wrote :
As perviously stated its not the speaker you should worry about
it's the AMP...

General rule: 2 8 ohm speakers connected in parrallel = 4ohm (roughly) 3=2
if you connect them in series it will double the ohm
So some people use tricks... 2 8 Ohm speakers in Series = 16 then 2 more connected in Series but connected to the original 2 in parralel
= 8 ohms (I confused me too, hahaha)

see this linky http://www.audioholics.com/education/loudspeaker-basics/loudspeaker-impedance-series-parallel-connection-basics


Even tho the creator say it will run safely at 2ohms, the lower the ohm the more power
but the drawback is.. The Amp works Harder and HOTTER!! so you can't play for longer periods

I would not run a amp below 4 ohms.

Also remember more speakers are blown due to underpower not overpower
A speaker that states 300Watts is actually 600Watts Program and about 1200Watts Peak
you really want to provide power as close to the PROGRAM Rating as you can get. (500 - 600 Watts)


Thanks,
DJ SMG


Very good answer. I agree. The AMP is what you have to worry about.
 
With my QSC amps I can run 4 speakers per channel wired in parallel at low volume levels with no problems. If I am going to have the volume loud I generally only put 3 speakers on each channel. Still that gives me a total of 6 speakers running on one amp. The problem is that in actuallity an 8 ohm speaker sometimes dips below 8 ohms depending on the frequency. 8 ohms is the measured average. So sometimes that speaker is as low as perhaps 6.8 ohms at certain frequencies. So you can see how wiring 4 speakers on a channel will sometimes create a very low load, perhaps as low as 1.5 ohms! Also keep in mind the amp runs hotter and draws tons of current from the wall outlet at 2 ohms! It's better to get a 2nd amp! Let each amp run 2 speakers per channel....
 
thank you so much for the easy explaination.........one amp = one speaker............that makes my next decision easier. I have a Peavy 1500 amp and was gonna buy the 3000 for the bigger SD speakers I just got but based on your explaination.......it would be better for me to just run 2x1500...........right????

DJ Extreme
 
but one thing to remember is watch the breakers and see if there a 15, 20 30 amp breakers i usally run in to 20 amp breakers and get away with it but i have to run cords to differant outlets that are on differant cirrcets

nothing sucks worse that blowing a breaker in the set, thats why i run a UPS battery back up small amp 240 watts total an mixer and cd player all combinded it only 12 amps so i can still play even if i blow the breaker saved my ass to many times.
 


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