Rune Bivrin wrote:At 4kHz the wavelength is about 8.5cm = 3 3/8". You need to bring them really close. The long edges should be parallel and touching.
+1
Here's how I did mine.
Test jig halfway through construction.
Finished test jig, rear pizzer is fixed, that's my reference. The one in front is pressed into the cup and starts making noise as it makes contact with the copper wires.
On the left is my source: phones output of an old transistor radio, tuned between FM stations.
While the headphone out from the IPhone worked, I wasn't sure I was getting the results I should. So I rewired the tester to get power from and old PA head. Got more volume, but the results were the same.
Every piezo worked, but I got an increase in volume regardless of whether it was proper polarity or reversed. The only difference I heard was pitch change in some cases.
I also ran every one of them through a 2k-20k sweep and everything worked so I guess I'm good to go. Should I be surprised that none of them were reversed wired?
"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."
"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."
Bruce Weldy wrote:Should I be surprised that none of them were reversed wired?
No, I don't think I ever found a reverse either. And the difference isn't huge, it's just that the pair with one reversed plays just a little softer than a single, instead of a little louder.
Still I'm glad to have tested for it anyway. I dislike tearing parts out of a finished cab that does not perform as intended, looking for a single bad element in a large array. Much easier to sort out the individual pizzers before gluing them together.
AntonZ wrote:I dislike tearing parts out of a finished cab that does not perform as intended, looking for a single bad element in a large array
Especially now that the elements seem to be glued in place.
I had the same experience where they were not noticeably quieter when phase reversed. They did seem slightly louder when in phase, but the best test I found was to put my head fairly close (12" or so) so I started to get some stereo separation. Then I would move my head side to side in the stereo field. Tweeters that were in phase sounded even across the field and the sound image stayed centered. Basically, they sounded like one tweeter centered in front of me. Out of phase sounded like two different sources coming from two different directions.
AntonZ wrote:I dislike tearing parts out of a finished cab that does not perform as intended, looking for a single bad element in a large array
Especially now that the elements seem to be glued in place.
I had the same experience where they were not noticeably quieter when phase reversed. They did seem slightly louder when in phase, but the best test I found was to put my head fairly close (12" or so) so I started to get some stereo separation. Then I would move my head side to side in the stereo field. Tweeters that were in phase sounded even across the field and the sound image stayed centered. Basically, they sounded like one tweeter centered in front of me. Out of phase sounded like two different sources coming from two different directions.
I guess if it's really that hard to discern, then all should be well when slammed together in an array.....
"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."
I can reverse the polarity on all 4 of my DR's through my DCX-2496 and not really hear a difference.I'm going to hook some different speakers to the DCX and see if i hear a difference.If i do i'm gonna be inclined to think i have something wrong.
Built:
2 Autotuba's MCM 55 2421
8 T48's 24"wide 3015 LF
2 DR 250's melded Deltalite II 2510
2 DR 250's flat Deltalite II 2510
2 SLA HT systems
1 Table Tuba Dayton DCS 255-4
2 T 39's 20" wide 3012 LF
1 T-18 13" wide MCM 55 2421
2 SLA Pro's
djtrumptight wrote:I can reverse the polarity on all 4 of my DR's through my DCX-2496 and not really hear a difference.I'm going to hook some different speakers to the DCX and see if i hear a difference.If i do i'm gonna be inclined to think i have something wrong.
If you reverse 'em all - they'll be in phase with each other and you won't tell a difference. You'd have to reverse half to see if there was a difference.
I tested until I was blue in the face.....so I went on with the cutting.
Here's my army of piezos with the straight cuts finished. Heading back out in a few minutes to start the 45s.
This isn't hard word, but it is tedious. Took awhile to get my jig squared up - had to use a little masking tape to build one side up a little as I was off 1/32".
"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."
