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Topic: The old ohm question |
Richard Tipple
From:
Ohio, USA
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Posted 13 Jul 2006 2:06 pm |
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I can never remember ,,,,,,
I have a Peavey power amp that delivers 230 RMS into a 4 ohm load.
I run two speakers ,one off each side of the power amp, they are 8 ohm speakers,so I presume I am only getting about 115 Rms per side.
If I run out of one side of the power amp to a speaker and jack that speaker to the other using just one side of the power amp, can I get a 4ohm load ?
In other words,,how would one connect two 8 ohm speakers together to get a 4 ohm loading
,would they need to be wired in series or paralell.
Also does series mean from the - of one speaker to the + of the other and so on, or would it be from the + to + and - to - to each speaker,,,WHEW !! man am I mixed up  |
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Mike Wheeler
From:
Delaware, Ohio, USA
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Posted 13 Jul 2006 3:15 pm
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Series would be the amp's + terminal to + terminal of 1st speaker, then - of 1st speaker to + of 2nd speaker, then - of 2nd speaker to - amp terminal. The impedances simply add together. 8ohms + 8ohms = 16ohms
Parallel would be the amp's + terminal connected to both speakers' + terminals, and the amp's - terminal connected to both speakers' - terminals.
(I'll give you the simplified rule of thumb for calculating parallel speakers) In parallel, as long as you're combining an EVEN number of speakers ALL OF THE SAME OHMAGE, you can simply divide the impedance of ONE of the speakers by the number of speakers. Four 4ohm speakers...4ohms divided by 4 = 1ohm. Two 4ohms speakers...4ohms divided by 2 = 2ohms. (i'll leave the real formula explanation for parallel connections to our very capable experts)
Connecting more than one speaker to the amp depends on the amps specs. They're not all created equal. The back of the amp should display the output specs for that amp. You get the best power transfer to the speakers when you follow the maufacturer's recommended impedances/loads.
OK, let's hear from our engineers for the exciting details (or corrections) lol |
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Vernon Hester
From:
Cayce,SC USA, R.I.P.
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Posted 13 Jul 2006 4:16 pm
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PRALLEL= Speaker one, times speaker 2,divided by speaker1,plus speaker 2.
speaker one 8 ohms X speaker 2 8 ohms=64
speaker one 8 ohms + speaker 2 8 ohms=16
Total load+4
series connection simply add.
Vern |
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Dave Mudgett
From:
Central Pennsylvania and Gallatin, Tennessee
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Posted 13 Jul 2006 7:30 pm
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Two 8-ohm speakers in parallel gives 8*8/(8+ = 4 ohms
Two 8-ohm speakers in series gives 8+8=16 ohms.
In the general case, if you have two impedances, Z1 and Z2, the total impedance in series and parallel is given by the following formulae:
Z(series) = Z1 + Z2
1/Z(parallel) = (1/Z1) + (1/Z2)
or, equivalently
Z(parallel) = (Z1*Z2)/(Z1+Z2)
If this is a mono amp that puts out 230 watts into a 4-ohm load, then you clearly want to wire your two 8-ohm speakers up in parallel. Many speaker cabinets I've seen have two jacks each, which allow you to simply jump the connections to hook them up in parallel. With such speakers, you can just jump the speakers and connect one of the remaining jacks to the amp output. If you have any question about the impedance of the jumped speakers, just check the resistance of the jumped pair with an ohmmeter - if they're really in parallel at 4 ohms, your ohmmeter should read around 3-3.5 ohms - this is pure resistance, not complex impedance.
You speak of "sides" of the power amp - is this a stereo or mono power amp? If it's 230 ohms per side stereo, then probably the best thing to do - if you just have two 8 ohm speakers - is to run one side each into a separate speaker. You won't get 230 watts per side, but the amp will run cooler that way and you'll probably get as much power as if you just run both speakers parallel out of one side.
Never run a solid-state power amp into a lower impedance than it's rated for. It's OK to run it into a higher impedance speaker - you won't get maximum power transfer, but it will not hurt the amp, in fact the amp usually runs cooler. But never run a solid-state amp into a lower impedance load than the minimum rated impedance - this can damage the amp. This is fundamentally different than a tube amp, which expects a matched load for maximum power transfer - in other words, if it says it wants 4 ohms, you should give it 4 ohms, not 2 or 8. If the transformer is overdesigned, it may be OK to be somewhat mismatched, but sometimes the impedance matching is pretty important.
All this without even getting into "bridging" a stereo amp, which I don't like to do anyway. Be very careful if you bridge a stereo amp - bridging mistakes are probably the number one cause of PA power amp failure I've seen.[This message was edited by Dave Mudgett on 13 July 2006 at 08:37 PM.] |
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Mike Brown
From:
Meridian, Mississippi USA
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Posted 14 Jul 2006 7:37 am
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All Peavey solid state amplifiers are thermally protected at the output and can operate all day long without a speaker load.
Mike Brown
Peavey USA |
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Ray Minich
From:
Bradford, Pa. Frozen Tundra
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Posted 14 Jul 2006 7:47 am
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Great Mike!. I like that news. Now if you could only get them to survive a dead short...  [This message was edited by Ray Minich on 14 July 2006 at 08:47 AM.] |
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Richard Tipple
From:
Ohio, USA
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Posted 14 Jul 2006 1:12 pm
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The amp is a Peavey M 2600 Stereo 230 Watts Per side.
I sure thank you guys for the help |
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