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-   -   8 Ohm, 4 Ohm or 2 Ohm Configuration?? (http://www.diyaudio.com/forums/pa-systems/219172-8-ohm-4-ohm-2-ohm-configuration.html)

apexdjs 6th September 2012 05:01 AM

8 Ohm, 4 Ohm or 2 Ohm Configuration??
 
I am working on replacing an old sould system for a very large skating rink and am trying to decide on which amps and speakers i should purchase.

I am probally going to replace the 4Ohm large speakers with multiple Yamaha 8 Ohm speakers that I can position in more directions for better coverage.

My main question is whether or not I should buy smaller amps and run each channel to (1)500 watt 8 Ohm speaker or purchase larger amps and run (4) 8 Ohm speakers on 1 channel at a 2 Ohm load giving me 500w per speaker.

Would running in a 2 Ohm load be bad for amps and speakers if the power is rated perfect or should I stay away from running a 2 Ohm load?

Enzo 6th September 2012 06:14 AM

Some guys will argue with me, but if an amp is of a reputable manufacture and is rated to 2 ohms, then it ought to handle 2 ohms. Some guys feel there is something magic about 2 ohms and should never go there. The same thing used to be said about 4 ohms a few decades ago. It is all a matter of what the amp is designed to do. Crown used to make the MA-10,000. This behemoth was rated at 10,000 watts into one half an ohm - yes 1/2 ohm. it was intended for large stadiums and such.

Here is where I worry: if I see a rating like 200W into 8 ohms, 400W into 4 ohms, and 180W into 2 ohms. That much reduced 2 ohm rating tells me they are willing to tell you it will take 2 ohms if you never turn it up. Forget that. Now look at another amp rated 200/400/800W into 8/4/2/ohms, well that sounds more like a serious amp rating.


Do you need 500 watts per speaker? You don;t say what their use will be. Background skating music? Live entertainment? Will the people be paying attention as they skate? Or will even live acts be background sound to the skaters? Drunken skaters are probably a lot less interested in the snorting bass and sparkling highs than would be concert goers.


Regardless, if you plan to have 500W per cab either way, then have you priced it out? List the amps you would need. How does the total cost stack up?

And give some thought to power distribution. If you are daisy chaining the speakers in your 2 ohm setup, then that needs to be some heavy speaker wire, versus lighter wire for the single speakers.

Have you looked into powered speakers? That way you can distribute just the line level signal from the mixer to as many speakers as you want. NO impedance worries in combining speakers. Just about all the speaker makers have powered speakers in their lineups, including the Yamaha. And that might make it easier to zone the place if that has any value.

apexdjs 6th September 2012 08:05 PM

The speakers would be used for just background music and announcements but at higher levels from time to time depending on the type of session the skating rink has. This is a very large area to cover and the speaker wire from amp to speaker will be long runs of up to 200' away from each other. I am leaning towards having two yamaha 8 Ohm 500 watt speakers in each corner of the rink linked together for a 4 Ohm load on Amp. I am wanting to use the QSC Powerlight 3 PL340 which is even rated as low a s a 2 Ohm load. I really don't want to have to run larger speaker wire for a 2 Ohm load. The speakers that they have now are 4 Ohm and I was planning on reusing the wire.

I would prefer powered speakers but then electrical would have to be run to every speaker and that could be very exspensive.

Another question I have, if I connected two 8 Ohm speakers to one channnel of the amp with two individual wires, would it make the load 4 Ohms like connecting 1 wire to amp and to first speaker and from speaker 1 to speaker 2 with another wire?

Cal Weldon 6th September 2012 08:08 PM

Quote:

Originally Posted by apexdjs (Post 3154856)
if I connected two 8 Ohm speakers to one channnel of the amp with two individual wires, would it make the load 4 Ohms

Yes.

Enzo 6th September 2012 08:22 PM

Remember it is a system, not just parts. If powered speakers is attractive, then figure out the costs. Yes, you would need to run AC power to them, but you would no longer need amplifiers back at the booth. WHich costs more? How much more do powered speakers cost than the same speakers in passive form? Powered speakers with signal and power lines or passive speakers with speaker lines and amplifiers, who winds that toss up? I know you have speaker wire already, but if you had to get signal cable instead, add it up

The whole question is the system, not 8 ohms or 4 ohms. Propose a system to yourself. Let us assume the mixer or other signal source is a given for all systems we consider. Sit down and add up all you need for your proposal - Yamaha speakers, QSC amps, speaker cords, whatever. Now do the same for any alternative you are considering. Got a third possibility? MAke up a sheet for that. Then add in reasons for and against each idea. Maybe one system would be more flexible than another, or lend itself to expansion later.

mickeymoose 6th September 2012 08:48 PM

How large is large? How many seats?

I myself would go for the highest impedance available. A 250' pair of 14 gauge wire has a resistance of about 1.3 ohm and you loose a lot of power in the wire (16% with 8 ohm speakers at 250'))

I also would discount powered speakers. If something goes wrong, it is most likely the electronics, not the speaker. Renting a bucket truck (unless there are catwalks) to fix the speaker gets pretty expensive (and tedious) very quickly! E

Original Burnedfingers 6th September 2012 09:57 PM

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