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[Ivan Beaver]

Bradford "BJ" James wrote on Sat, 06 June 2009 15:31

Got a ZM-104. I'll be able to go in and measure these mysterious speaker lines, but won't have easy access to the horns. What is the math for figuring out total wattage with this tool when the only info I'll have is impedance? Thanks, BJ Edited to add: I found it. watts= 4900/impedance

You REALLY need to do an impedance CURVE on a line-NOT just a single freq.

Let's say the "average" impedance of a loudspeaker that is tapped @ 1watt is 4900 ohms.  Fine.  But let's also say that you meter is only measuring at 1Khz (as the 104 is), AND the loudspeaker in question has an impedance peak at 1Khz that is 2-3 times that of the average.

What the meter will show is in gross error in figuring out the actual impedance load on the amp.  Yes at 1Khz it will be correct, but not at the other freq.

You HAVE to look deeper to get a REAL idea of what is going on.

For every complicated question-there is a simple easy to understand WRONG answer.

[Bradford "BJ" James]

I had thought of that after reading a  previous post of yours on here, Ivan.

Anyways, I just came back from the site. What a mess.
1 pr read 4ohms, 1 pr read 8 ohms, and 1 pair read 350 ohms. Only one pair is actual stranded speaker cable, the other 2 are solid wire telephone cord.
They are going to have to start from scratch, and I'm simply going to submit the quote recommending new amp, new horns and new wiring. Acutally I'll submit 2 quotes with the second having a bigger amp(for possible future expansion) and volume controllable zones.
I think I got the buzz fixed. Will know for sure Monday night.

Is standard install cable acceptable if it will be exposed? It has to be run along ibeams and truss.

Thanks so much for everyones input. So far so good.
BJ

[Bradford "BJ" James]

Ivan Beaver wrote on Sun, 07 June 2009 12:33

You REALLY need to do an impedance CURVE on a line-NOT just a single freq. Let's say the "average" impedance of a loudspeaker that is tapped @ 1watt is 4900 ohms.  Fine.  But let's also say that you meter is only measuring at 1Khz (as the 104 is), AND the loudspeaker in question has an impedance peak at 1Khz that is 2-3 times that of the average. What the meter will show is in gross error in figuring out the actual impedance load on the amp.  Yes at 1Khz it will be correct, but not at the other freq. You HAVE to look deeper to get a REAL idea of what is going on. For every complicated question-there is a simple easy to understand WRONG answer.

I'm just borowing the ZM-104. But I need to buy my own. Is there a meter that has this capability? The Goldline?
BJ

[Ivan Beaver]

Bradford "BJ" James wrote on Sun, 07 June 2009 14:47

Ivan Beaver wrote on Sun, 07 June 2009 12:33 You REALLY need to do an impedance CURVE on a line-NOT just a single freq. Let's say the "average" impedance of a loudspeaker that is tapped @ 1watt is 4900 ohms.  Fine.  But let's also say that you meter is only measuring at 1Khz (as the 104 is), AND the loudspeaker in question has an impedance peak at 1Khz that is 2-3 times that of the average. What the meter will show is in gross error in figuring out the actual impedance load on the amp.  Yes at 1Khz it will be correct, but not at the other freq. You HAVE to look deeper to get a REAL idea of what is going on. For every complicated question-there is a simple easy to understand WRONG answer. I'm just borowing the ZM-104. But I need to buy my own. Is there a meter that has this capability? The Goldline? BJ

A stand alone meter is going to be faily expensive.  You can get computer based units for less money, but you have to drag a computer along to run them.

Price vs convience.  

My portable unit is the Audio Toolbox-Contractors edition.  It can only do 1/3rd oct measurements on impedance, but that gets me pretty close in the field.

I use TEF for shop measurements.

[Bradford "BJ" James]

So, a stupid Behringer Hum Eliminator fixed the buzz. Just found out today that the ringer worked properly last night with no buzz.
BJ

[Ivan Beaver]

Bradford "BJ" James wrote on Tue, 09 June 2009 16:05

So, a stupid Behringer Hum Eliminator fixed the buzz. Just found out today that the ringer worked properly last night with no buzz. BJ

So the isolation transformer did it.  Physical isolation is a good thing.

[Mac Kerr]

Ivan Beaver wrote on Wed, 10 June 2009 13:13

Bradford "BJ" James wrote on Tue, 09 June 2009 16:05 So, a stupid Behringer Hum Eliminator fixed the buzz. Just found out today that the ringer worked properly last night with no buzz. BJ So the isolation transformer did it.  Physical isolation is a good thing.

Which would have been the 2nd, 3rd, and 4th responses to this thread once the ringer issue was mentioned.

Mac

[Bradford "BJ" James]

Thanks for pointing that out, Mac. )

As I mentioned, I had a XLR iso transformer that should have worked with the proper adapter cables. It didn't. I didn't have a 1/4" laying around, but thought it would be worth a try to get one. It worked.

Thanks for everyones suggestions. I really appreciate it.
And thanks to Mac for bringing this back up and reminding me to express my thanks.

BJ

[Bradford "BJ" James]

We landed the job. I'm installing a 12 zone 50w/zone 70V amp and mixer and 20 horns to start with.
Next question: the mixer and amp will be located in a front room, but the warehouse at the rear will require that I have 12 runs of speaker cable go from the front to the back, and then split off to the separate zones from there. We're probably not going to implement all 12 zones to start, but I want to run all 12 pair to the rear while it's being done. All I can find is 2 pair install cable. Is there more pairs available in an install multi cable? Even 4 pairs would make life easier.
Thanks,
BJ

[Hal Bissinger/COMSYSTEC]

Belden 9741, 12 pair/18ga. Looks like 18ga is the best you are going to do and I would think it should be OK with only 50w @70.7v unless you are going long distances.

-Hal