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Author Topic: Voltage  (Read 6929 times)

Ron Steigmajer

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Voltage
« on: June 15, 2008, 12:44:23 am »

Hey everyone,

I'm in need of a little help & advice.

I'm trying to get the best method to obtaining the voltage from my amp (Crown XTi2000) & speakers (Yamaha S215V) to match in stereo mode.

I've got this method for my speakers (not to sure if it's correct) voltage = sq root of watts X impendance = 500 watts X 4 ohms = 2000 then hit sq root = 44.721 volts AC. (500/1000/2000 is the rating of the speakers at 4ohms)

I currently don't have limiters set So I'd be getting the full 800 per channel.

I was wondering which type of Wave I should use to get the most accurate reading (i.e. Sine Wave, Pink Noise). I've got a volt meter ready to do testings.

If you need more information, let me know. I've left a attachment, which includes a frequency range and specs of the speakers. I don't know how to read the information by myself.
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Rob Timmerman

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Re: Voltage
« Reply #1 on: June 15, 2008, 01:36:06 am »

If you're using an AC voltmeter, you want to use a sine wave, preferably around 60hz as a test tone.  The speakers need not be hooked up for this test.  There were a few (2-3) threads on setting limiters in the past month or 2, so you might try a search...
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Ron Steigmajer

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Re: Voltage
« Reply #2 on: June 15, 2008, 01:51:08 am »

Hi Rob,

I've tried a Sine Wave at 60Hz before but I got a maximum of 18.8ACV and after that I've been told not to use a Sine Wave. The 18.8ACV was at maximum gain with no limiters set.

Edit: Unless I'm doing something wrong  Confused I run the amp straight to the computer and use winamp as an application.
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Don Boomer

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Re: Voltage
« Reply #3 on: June 15, 2008, 09:42:11 am »

You are measuring the output of the power amp ... correct?

Yes use a sine wave since that's what an RMS voltmeter is meant to read.

It's unlikely that you'll ever drive the amp to get 800 continuous watts out of it using music.  You should be in good shape with the amp at full as long as you don't clip the amp (does the amp have built-in clip limiters) or do something really careless.  Your 800W amp is compared to the 1000W program rating of the speakers.

read this ...

peavey.com/support/technotes/poweramps/HOW_MUCH_POWER.pdf
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Don Boomer
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Ron Steigmajer

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Re: Voltage
« Reply #4 on: June 15, 2008, 10:33:41 am »

Ah k,

I think I've got it worked out. I was using a normal voltmeter instead of a RMS voltmeter (never knew something like this existed) thats why I only got 18.8ACV.

Would someone be able to attach a Sine Wave file which I can just open using winamp to test it.

Can you use a normal volt meter to get the same reading as the RMS voltmeter?
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Todd Rasmussen

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Re: Voltage
« Reply #5 on: June 15, 2008, 10:41:43 am »

Ron,

Have you considered getting some experienced hands-on help getting your gear set up?

Seems you've been struggling with all this for quite a while now.

Just a thought...
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Rob Timmerman

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Re: Voltage
« Reply #6 on: June 15, 2008, 01:21:08 pm »

Ron Steigmajer wrote on Sun, 15 June 2008 10:33

Ah k,

I think I've got it worked out. I was using a normal voltmeter instead of a RMS voltmeter (never knew something like this existed) thats why I only got 18.8ACV.

Would someone be able to attach a Sine Wave file which I can just open using winamp to test it.

Can you use a normal volt meter to get the same reading as the RMS voltmeter?


With a pure sine wave, an inexpensive AC voltmeter and a true-RMS AC voltmeter should give the same reading.  A true-RMS AC voltmeter will give more accurate results with non-sinusoidal waveforms.  I believe Lee Pazitus did some testing a few years back on the magnitude of this difference, and posted the results here.  ISTR that the differences are small.

I'm guessing that your problem is that your computer doesn't have enough output to drive the amplifier into full output, and the maximum of 18.8V is limited by what is input to the amplifier.  Perhaps try adding a mixer in front of the amplifier to increase the level you can drive the amplifier with.
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Don Boomer

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Re: Voltage
« Reply #7 on: June 15, 2008, 01:46:12 pm »

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Don Boomer
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Ron Steigmajer

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Re: Voltage
« Reply #8 on: June 15, 2008, 09:43:22 pm »

Hi todd,

I have considered getting some experienced help, I've been to all the music stores that sell PA gear and all they asked me was "Where did you get the gear from?" and I said "Big Time Audio (in USA)" and then they say "We can't help you because you didn't buy the gear from us etc". There are only a few stores in Perth that sell this gear.

Well I did ask Big Time Audio, they told me to use the -6dB limiter and not to clip the amp. 6db below full output is a rough guess of 200? from a 800 max output amp. Which is kinda useless.

Anyway, I think that Rob could be correct. It could be that my sound card doesn't put out enough input for the amp. I've got to have a look at that.

I appreciate all the help guys. Thank You Don aswell for the website for the test tones.

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Ron Steigmajer

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Re: Voltage
« Reply #9 on: June 18, 2008, 09:45:48 am »

Well guys, I've done some more testing and my XTi2000 starts to reach clipping light at ~23ACV, the clipping light shows clipping at full output (800), so I'm using these calculations

23/800 = 0.02875 * 500 = 14.375ACV (to get 500)

So I've hooked up a volt meter and using a Sine Wave from http://www.binkster.net/extras.shtml I've turned up the dial on the amp to reach a maximum of 14.375ACV (this is when my inputs are all maxed out).

This should keep me safe, I usually run inputs at 75%, so I should be good because that will give me less than 14.375ACV. Until I get some further information I will use these settings.

Please let me know if I've done wrong calculations etc.
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