Reply posted by A Hamilton on August 20, 2000
Miles,
I apologize if this info is buried in this thread but.... www.woodworx.com has a polarity tester that is rather inexpensive (around US$60). You'll need a CD player. The tester comes with a CD that contains pulses you use to check the spkr's relative polarity. The CD also contains sweeps, pink noise, songs, etc for other tests on you rig.

I think the tester is named "Sound Check" or else that is the link on their site to find info on it. You can order directly from them.

Hope this helps....
Alan

Reply posted by Miles Langham on August 20, 2000
Is this the device that the two Brits, including Alan Parsons put together? I have sent two emails and got no response. I have been having trouble with SW Bell email servers though.

Thanks, I'll look into it.

Miles

Reply posted by Curtis List (Too Tall) on August 21, 2000
Well boss, do you have access to a computer?

If so, there are free and demo FFT programs around that should solve your problem. This also gives you other capabilities beyond merely checking polarity on drivers. For one thing you can look at time alignment for your separate boxes

For polarity you need a pulse of known polarity and you are there. If you can't find one to use I can email you one if it comes to that. Let me look around and see if I can find the websites for the programs.

One thing to be aware of is a single "click" pulse does not do well going through transformers. You might still be able to tell polarity (perhaps?), but you can not trust anything past that (IF it goes through at all.)

Mobile polarity checkers are nice, but for in the shop there are other ways.
If you can figure a way to monitor SPL off your test mic you can take matched elements of the PA and place them face to face very close together (less then a meter).

Place your mic dead center between them then run signal through the pair with one speaker input 180 out of phase. Now repeat the test in phase.

You can use pink noise or one to many sine freqs.

Too Tall

Reply posted by Miles Langham on August 21, 2000
Thanks for the info Too Tall. I have several computers to use. Hell I could dedicate one to sound system testing.

Let me take a look at the information you kind folk have given me and I'll come back for more info.

If anyone is passing near NW Arkansas and needs a grunt for a show let me know in advance. I'll trade the load in/out labor for picking your brain.

Yes that includes you Jim.

Miles

Reply posted by Doug Fowler on August 21, 2000
-"Place your mic dead center between them then run signal through the pair with one speaker input 180 out of phase. Now repeat the test in phase."

Curtis:
Do you mean with reversed polarity, rather than 180 degrees out of phase? In order to make the signal 180 degrees out of phase it would require an all-pass filter with a phase adjustment, I believe. You could do this with an Omnidrive, which offers phase adjustment on the outputs.

It seems as though it would be much easier to reverse the polarity than jump through hoops trying to change the phase, which of course is frequency dependent.

doug

Posted by Curtis List (Too Tall) on August 21, 2000
That would be me being sloppy with terms.

Please compare the SPL with the inputs to the negative and positive terminals on the driver hooked up normal and swapped. ( I KNEW I was going to called on this but was too lazy to change it. Serves me right!)

Too Tall

Reply posted by Doug on August 21, 2000
I knew you know the difference ;-)

doug