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Old 09-09-2012, 01:18 PM   #1
Tim the Rocker
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PA Speakers

Heeeeeeeey,


So, I'm setting up our rehearsal room and I've got two speakers (8ohm 250watt) for the singer, but I've also got a monitor for him (8ohm 250watt).

Now, the amplifier/mixing console has two outputs for the XLR (that's the name, right?) and two for jacks. I'll connect the two main speakers through the XLR outputs, but can I connect the monitor in series with either one of the other speakers, or would that overload the ohms? It would be connecting two 8ohm speakers in series from an 8ohm output.
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Old 09-09-2012, 01:47 PM   #2
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Two 8ohms in series = 16ohm. So you'd have one 8ohm speaker and one pair that would total 16ohm. It shouldn't cause any damage (it's really only valves that get hurt by mismatched impedance), but it may not sound particularly good.
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Old 09-09-2012, 02:13 PM   #3
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Quote:
Originally Posted by MrFlibble
Two 8ohms in series = 16ohm. So you'd have one 8ohm speaker and one pair that would total 16ohm. It shouldn't cause any damage (it's really only valves that get hurt by mismatched impedance), but it may not sound particularly good.

Nah, it'll sound fine. Nearly all solid state amps have no issues with running at a higher impedance than rated , solid state amps usually don't even mind running without a load connected altogether (infinity ohms!).

However, the available output power is highest at the rated load impedance and becomes lower if the impedance is higher. So thats the only thing you lose when hooking up a higher impedance speaker(s).
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Old 09-09-2012, 02:22 PM   #4
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Quote:
Originally Posted by Tim the Rocker
Heeeeeeeey,


So, I'm setting up our rehearsal room and I've got two speakers (8ohm 250watt) for the singer, but I've also got a monitor for him (8ohm 250watt).

Now, the amplifier/mixing console has two outputs for the XLR (that's the name, right?) and two for jacks. I'll connect the two main speakers through the XLR outputs, but can I connect the monitor in series with either one of the other speakers, or would that overload the ohms? It would be connecting two 8ohm speakers in series from an 8ohm output.

Are these powered speakers or passive? I am thinking passive since you said 8 ohm.

What is the amp you are using? If it is a powered mixer what is it?

When you said XLR out, those are signal only and require some kind of power amp.
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Old 09-09-2012, 02:31 PM   #5
Tim the Rocker
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Passive speakers, active mixing console (Behringer PowerMaxx 8 Channel 100Watt, decent enough for what I need, but one day soon it'll be changed) and by XLR I mean speakon cables, cables for speakers.
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Old 09-09-2012, 08:30 PM   #6
gumbilicious
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Quote:
Originally Posted by MrFlibble
but it may not sound particularly good.


why? i don't see any reason this would do anything other than reduce the output of the power amp.

Quote:
Originally Posted by Tim the Rocker
So, I'm setting up our rehearsal room and I've got two speakers (8ohm 250watt) for the singer, but I've also got a monitor for him (8ohm 250watt).


so if this is a rehearsal room, with no crowd, wouldn't all the speakers be monitors to hear yourself? in other words, i don't think you'll need to use any more than 2 speakers for rehearsal.

i am guessing the 'two speakers' are 2-way, square box enclosures. i am guessing the 'monitor' is a 2 way wedge. if this is for rehearsal, then just put the speakers on stands and be done with it. the monitor will help when you start playing live.

Quote:
Originally Posted by Tim the Rocker
Now, the amplifier/mixing console has two outputs for the speakon and two for jacks. I'll connect the two main speakers through the speakon outputs.


yes. and this is all you need.

Quote:
Originally Posted by Tim the Rocker
but can I connect the monitor in series with either one of the other speakers, or would that overload the ohms? It would be connecting two 8ohm speakers in series from an 8ohm output.


most likely your product is solid state (i can't really find anything on a behringer powermaxx). solid state has a minimum impedance requirement. as long as you meet the min requirement your fine.

so Rtot = R1 + R2 = 8 + 8 = 16 ohm

but there IS a problem. unless you are doing something pretty funky, you would actually be connecting these speakers in parallel and not series. those jacks on the back of the cabs are almost exclusively wired in parallel, so if you are daisy chaining cabs then you are connecting them in parallel, this means you use this math

1/Rtot = 1/8 + 1/8 = 2/8
Rtot = 8/2 = 4

and this would NOT provide the minimum impedance needed.

basically: do not daisy chain these cabs to one of your inputs if it requires a min 8 ohm load.
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Last edited by gumbilicious : 09-09-2012 at 08:31 PM.
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Old 09-09-2012, 08:43 PM   #7
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Originally Posted by gumbilicious
why? i don't see any reason this would do anything other than reduce the output of the power amp.
Because one side will be getting half the juice of the other. That's disconcerting for a singer who needs an accurate and even representation of the sound.
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Old 09-09-2012, 09:08 PM   #8
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Originally Posted by MrFlibble
Because one side will be getting half the juice of the other. That's disconcerting for a singer who needs an accurate and even representation of the sound.


then i'd just use the inverse square law to my advantage.
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Old 09-10-2012, 12:24 AM   #9
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From what you are describing the speakers will be in parallel, not series. Listen to gumbi.
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Old 09-10-2012, 12:33 AM   #10
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I asked my friend about this last night, funnily enough. I used to run the school's PA systems while I was at highschool, and at one point I was switching between using 4 outputs on the amplifier and using 2 outputs to main speakers, then daisy chaining them to run smaller wedge speakers. I never had any issues with stuff blowing up (then again, they had load protection), but I was wondering how it was all likely to be running.
The one I used from memory was 400 watts output at 8 or 4 ohm or some such, and the speakers were all about the same. It had two outputs for L and R speakers, and the speakers were all passive, with (as far as I am aware and can remember) both input and output jacks.

Nothing ever blew up, and it sounded pretty good for what I pushed through it, so I can only assume I was doing /something/ right.
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Old 10-20-2012, 09:40 PM   #11
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Sorry to bring this back from the dead, but it also matters if you are pushing a mono or a stereo signal to the speakers, too. Full range mono has a great deal more flexibility. Another thing you can do is buy a cheap aux amp, and run the monitors off of that.
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Old 10-20-2012, 10:20 PM   #12
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Originally Posted by Shawn Hughes
Sorry to bring this back from the dead, but it also matters if you are pushing a mono or a stereo signal to the speakers, too. Full range mono has a great deal more flexibility.


i am a little confused by this statement. how exactly is a 'full range mono' more flexible? are you talking about the signal or the PA?

unless you have some insight i am just not aware of, i find this pretty misleading


Quote:
Originally Posted by Shawn Hughes
Another thing you can do is buy a cheap aux amp, and run the monitors off of that.


that is true, but it was brought up earlier that having a separate main/monitor in a practice space is pretty redundant. if you are already using the mains as monitors then there isn't much need to run more monitors.

but if you gig out, it would be a nice way to scale the PA system up for gigging conditions.
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Old 10-21-2012, 11:28 PM   #13
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Well, it may be redundant, but some people think they should practice like they play. Getting sound from one teeny speaker at your feet is a lot different to me than getting them from your house mains. I base this off playing a teeny bit both ways, but mostly from having my own PA, and running a little sound reinforcement for others.

Also, feedback loops and delay is different.

Quote:
am a little confused by this statement. how exactly is a 'full range mono' more flexible? are you talking about the signal or the PA?



What I am referring to is the output from your speaker power amplifier(s). If all you are providing is full spectrum mono, it's just a little math to keep values in a range the output transistors like. Each speaker provides the entire signal, so you can put a speaker anywhere. Using an L pad, you can even attenuate individual speakers.

If you are running multiple amps, each for a monaural segment of frequency (two amps for lows, one for mids, one for highs), it gets more complicated.

If you are providing stereo output, that's the hardest. You can't just throw a speaker anywhere you want. You'll only be providing your talent a part of the complete output.

Better?
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Old 10-22-2012, 12:41 AM   #14
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With the exception of a few really good venues with top end PA's set up by an expert, stereo mixes are more trouble than they are worth. In most venues only two people will get any benefit from it and the rest of the crowd get an out of balance mix. We normally pan everything to the centre so everybody gets the same mix so whether it's a stereo amp or not it doesn't really matter shit.
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