daisy chaining monitors

[PastorJason]

guys, first a little vent- just taking over as worship pastor with the duties of AV set up, etc... (Im the youth pastor too). After spending 4 hours today setting up our system for our 1st service (pretty much stripping it down and starting over since morons pieced it together "because we had the pieces") I am seeing resistence with my team. When I left 2 of them went in and put it back to "the way it should be". the big issue is that they were ticked that I daisy chained 4 monitors together. Is this ok or not? a friend who helped me that I trust said it is ok for the Ohm leval is high enough for each. Then googled and heared that you divide your omh rate by number of monitors and if its positive then you are ok.... A little advice before I lose my mind.

Thanks.

[kbob]

the answer unfortunately is "it depends"

In this case, the variables are several:

What ratings does your amp support? Is it rated for 8 ohms? 4? 2?

What are your speakers rated at in terms of ohms? (Understand that while it's a single figure, actual resistance, which is what ohm's measures in simple terms, varies by frequency)

Finally, how are you daisy chaining the speakers? Using speaker jacks built into the speakers themselves? Or simple "Y"-splitters.

If the built ins, then it also depends on whether they're wired internally for series or parallel usage (series adds resistance of each speaker, parallel divides it-again in simplified terms). If they're wired for serial use, then it shouldn't be a problem...

If the speakers are wired in parallel, or if you're using the simple "Y" splitters, then you have to reference minimum ohm ratings from your amp versus the divided resistence of the speakers-

As an example, 2 8 ohm speakers wired in parallel will yield a resistance of 4 ohms, while 4 8 ohm speakers will yield a resistance of only 2 ohms. Note the math here can get complex very quickly if the speakers have different ohm ratings...

If I remember correctly, the formula goes something like R(x)/N, summed and averaged for all the speakers in the load.

where R= the resistance of each speaker
(x)=speaker 1, 2, 3, 4 etc...
N=total number of speakers

so, for 4 8 ohm speakers, wired in parallel, the math would go something like:

8 divided by 4 equals 2
2+2+2+2=8 (sum of the divided resistances), divided by 4 (total number of speakers) equals 2 ohms, for the average load for the four speakers involved.

On the other hand, 2 4 ohm speakers wired in series will give you a resistance of 8 ohms, or two 8 ohm speakers wired in series will result in a load of 16 ohms....somebody else feel free to jump in here-please!

Typically, it's much worse to provide too little resistance than too much-and I've not seen amps actually rated for less than 2 ohms. You can mix and match series and parallel wiring-but be very careful, as two much resistance will make your amp's available power seem to go way down, and too little can quickly overtax an amp and lead to failure.

[Brad Weber]

Originally Posted by PastorJason

Is this ok or not? a friend who helped me that I trust said it is ok for the Ohm leval is high enough for each. Then googled and heared that you divide your omh rate by number of monitors and if its positive then you are ok.... A little advice before I lose my mind.

You are on the right track but a little off on a couple of factors.

When you daisy chain speakers they are wired in parallel. The idea of dividing the impedance (Ohms) of a monitor by the number of monitors to calculate the total impedance works for this arrangement as long as all monitors are the same impedance. If they vary, say some speakers are 4 Ohm and others 8 Ohm, then it gets a little trickier and the total impedance is 1/((1/impedance of speaker #1) + (1/impedance of speaker #2) + (1/impedance of speaker #3) + (1/impedance of speaker #4)). If all four speaker are rated 8 Ohms then this is 1/(1/8 + 1/8 + 1/8 +1/ or 2 Ohms, that same as diving the 8 Ohms by the four speakers. But if two speakers are 8 Ohms and two are 4 Ohms then it becomes 1/(1/8 + 1/8 + 1/4 + 1/4) or 1.33 Ohms.

Once you determine the total impedance of the speakers, then you have to consider whether that is compatible with the amplifier driving the speakers. Just being a positive number is not relevant, in fact there is actually no way for the total impedance to not be positive and greater than 0 no matter how many speakers you have, as you add speakers it approaches 0 but never gets there (asymptotic towards 0 for the mathematicians). What is relevant is that the total impedance of the speakers, or the load, be greater than or equal to what the amplifier is capable of supporting.

That gets into looking at the amplifier. Typically amplifiers have different ratings depending on how they are configured, e.g. stereo per channel, parallel mono per channel or bridge mono. So the first step here is to identify the operating mode of the amplifier, usually set with a switch on the rear panel and typically stereo or sometimes bridge mono. Once you know the operating mode, you can find the amplifier specs and look at the loads it is rated to drive in that mode, you might normally see 8 Ohms and 4 Ohms and maybe 2 Ohms. You typically do not want the total impedance of the speakers to be lower than the lowest rated load listed for the amplifier, for example if it is stereo mode and the specs show ratings for 4 Ohms and 8 Ohms in stereo mode then you do not want the total speaker impedance to be below 4 Ohms.

So using your situation, if all four speakers are rated at 8 Ohms the resulting total load is 2 Ohms and the amplifier driving them would have to be rated to drive a 2 Ohm or lower load as configured. Many higher end professional amplifiers are rated to drive 2 Ohm loads in some operating modes but many amplifiers may not support it. So depending upon the speakers and amplifier involved, daisy chaining four speakers may not be the best idea. Even if the total speaker load was 2 Ohms and the amplifier had a minimum rated load of 2 Ohms, with four speakers involved then for several reasons I might still be a little hesitant to run it that way.

[waynehoskins]

I'm always cautious about putting a 2-ohm load on a power amplifier, because older ones and cheaper ones (and especially older cheaper ones) aren't rated for it, aren't 2-ohm stable. Lower impedance means heavier load.

Just because you can plug something into a jack doesn't mean it's a good idea to.

I might encourage you to actually talk with your group of morons. They might actually know something, perhaps. The putting it back how it should be reminds me of something I did years ago as the youth tech intern at the church I was at. We were in a room with the worst acoustics I had ever heard, and one of the youth pastors decided we should try to move the stacks from stacks to wedge positions in front of the first row, meaning nobody past the first row would be able to hear. After they left, I returned the stacks to how they should be, because I knew it was a stupid idea. Your morons are probably using at least the same train of thought.

Do they have much experience? I would think so, seeing that they didn't want a 2-ohm load on a power amp, and that you were unaware that it might even be an issue. Don't alienate your tech crew. Don't, as a musician and youth pastor and not-audio-tech, make them rebuild the PA; that's like me making up a setlist that you should play.

[Esoteric]

I am with Wayne on this. I don't assume someone doesn't know anything until I know for sure. For example at my church I know there are several volunteers that really don't know anything. How do I know? They have broken scenery trying to move it without enough people, they run Source4 750w fixtures at 100% from 18 feet away, the projectors are off center when they set them up, there are huge piles of cable spaghetti on the stage (from the audio guys), the audio mix sucks, etc.

They have proven to me that they don't know anything. But I always try to give people the benefit of the doubt. I do not doubt their work unless I KNOW 100% for sure that they are wrong.

Mike

[DrowningnHim17]

just taking over as worship pastor with the duties of AV set up, etc... (Im the youth pastor too). After spending 4 hours today setting up our system for our 1st service (pretty much stripping it down and starting over since morons pieced it together "because we had the pieces") I am seeing resistence with my team. When I left 2 of them went in and put it back to "the way it should be"

Since they got you covered on your monitor dilemma. All I will say is if I did what they did the way they did it, I would lose my job. No, I'm not saying get rid of them because as Mike and Wayne said, they most likely do know something. Maybe some team meetings with an open discussion could help?
just my thoughts

[Esoteric]

Yeah, there are several different things at play here.

1. Insubordination in ones subordinates can not be tolerated. Period. If I asy something is to be done a certain way, that is the way it is to be done. The lone exception being something that is physically dangerous. Barring that there is no excuse for deliberate disobedience. Many other things can be tolerated, after all people make mistakes, but you are the one that was hired to oversee this, therefore your word is law to those below you (consider it written in stone).

2. But, you are dealing with volunteers. As such if you get a reputation as a hard butt, you will have a hard time filling your positions come Sunday morning. It is a fine line to walk, as some who have been volunteering for some time may feel a sense of entitlement and may be resentful toward you.

This is a delicate situation, you are staff, they are volunteers. That means your word is law. There can be no dissension once you have made a decision.

In this case I would call everyone together over a good dinner and have a meeting. Admit that you were wrong in this case if you were (not getting off on the strongest foot, but they will trust you more if you admit it instead of covering it up), but make it clear that if someone believes you are doing something wrong you value their opinion, but it should be expressed in private. That going behind your back and changing things is not acceptable under any circumstances. Use this time to get a feel on who knows stuff and who doesn't and how far their knowledge extends.

But make sure that the Pastor and elders are behind you as you do this.

Mike