Testing my tweeters

[Kaptain John]

Ok, so I received 24 of my 36 ordered tweeters today for my DR250 build. I am currently testing all of them. They all seem to work ok, but I'm not sure how to check if any of them are out of phase. I've hooked them all up individually to my stereo tuned to static and they all pretty much sound the same. So I selected one, hooked up the (+) lug to the (+) and (-) lug to the (-) on the output, then ran another wire off of the other side of the lugs to connect the next tweeter.
When I hook up the next tweeter, (+) to (+) and (-) to (-), the volume seems to increase. When I switch the wires, same result. Shouldn't the volume go down when I switch the wires? Am I even testing the right thing?

[LelandCrooks]

Give away my trade secrets here.

You need this: http://www.natch.co.uk/downloads/SigJenny/SigJenny.html

And something like this if you want to get really picky:
http://www.4pockets.com/product_info.php?p=48
or any rta.

Connect your pc to a stereo, run sigjenny sweeps from 8k to 18k. Listen for oddities. At some point between 12k and 18k you won't hear anything, depending on how good your hearing is. I still hear surprisingly to 15k. What you will hear are odd resonances from some of them at 1/2 of whatever freqency is being swept. Sometimes very loud. Those are losers. The very faint ones that only do it above 15k could be used with no ill effects. I don't, but that's because somebody's paying me to do it. For my own use I'd use those.

After that sort, then you run pink noise at a pretty good volume and spl match using the rta. It goes pretty quick, as the first sort will weed out most problem children right off the bat.

You'll find about a 10% failure rate.

[Kaptain John]

Thanks! Running the sweep through them definitely exposed some deficiencies.

[glenfolly]

Hey Leland, what a fabulous little program that SigJenny is ! The combination of audio oscillator and visual oscilloscope in one window is great. The oscillator goes down to 10Hz and I like being able to see the phase relationship visually.
There are going to lots more uses that I am going to find for this little program. Thanks Leyland for the link.

PS. I discovered that Mic inputs on laptop PCs output the bais voltage for electret microphone capsules- you know those little ones about the size of a pea. Just put 2 wires on the electret capsule and wire onto a 3.5mm phone plug and away you go. No need to worry about bias resistors and stuff.

[rwalkerphl]

Please excuse my ignorance as a newbie...

I've just created an 8 tweeter melded array for an O10 - do I test each one individually, then re-test as I add each one to a bank, or once each individual has been tested per Lelands description, all should be good?

Thanks!
Robin.

[LelandCrooks]

I test them all individually. Build the array, test individually again, then wire and test the entire array with pink noise.

[rwalkerphl]

Thanks Leland!