Bad alternative tweeter wiring

[gdougherty]

Two examples of melded array wiring:
On the left hand side is my old wiring scheme where I've had problems. Green is the "series" connection between the parallel wired banks. The elements in blue are ones that die a relatively quick death after only a few hours of use, especially if I push any sort of volume out of them. The entire array tends to have problems with distortion that sounds like overdriven piezos and the distortion problems only get worse over time. When I pulled them, every single array in my 4 OT12's had near dead tweeters in those spots. Last time out distortion in the upper frequencies was horrible and I cringed that I had no alternative speakers to use.

I've always used this type of wiring, even on straight sets of 6, series in the middle and amp connections in the middle two with current flowing out to the sides. Had distortion problems there, but not as bad for some reason and only after a long while of use. My biggest problem with the straight sets was getting them loud enough to keep up with the woofer.

On the right is my new wiring schematic after seeing David Carter's question when I realized maybe something was terribly wrong with mine. I've only rewired arrays, not fired them up and RTA'd as a full system yet. I did rewire one array kind of like this and had significantly better results the other evening, but I still had the green series wire on the other set of posts for the bottom tweeter and the amp leads wired in on the others where the green wire is in the picture. Wiring to the amp on the top side of the array in that configuration had very low output and very high current draw through the amp. Yes, it is a bad idea to wire negative to negative and positive to positive in a series wiring setup...

Hopefully this resolves all my tweeter problems and serves as a warning to others.
Now to go back and reconnect the array on the TLAH I helped build... doh.

[Bill Fitzmaurice]

I'm not going to attempt to figure out your scheme, for fear that if I didn't suffer from dyslexia before that I would after. The scheme used by David, save for the extra wire between the banks in his original, is what's in the plans.

[Sydney]

There is an old maxim: Electricity follows "The path of least resistance"
In your left hand example the feed goes in to one of the left blue piezos across the series bridge to the other bottom blue piezo and back to the amp.
That is the easiest ( least resistive ) path for electrons back to the amp
Measure the resistance between blue + input to the end of the + on the top ( after it has gone through 4 jumper wires.
The difference though small is what leads me to believe - Those 1st 2 - 4 piezos take the bulk of the load. They don't see the added resistance of the chain of wire links.
I was taught the best to distribute power absolutely evenly is with vertical buss bar type layout - all leads the same. similar to an AC entrance panel.
So all paralleled paths have the same resistance to the distribution points

[Tim A]

I think Sydney's on the right track.

Just looking at it logically, you could snip any one of the cross-jumpers between blue piezos left and blue piezos right, and the two blue ones on the left will continue to work. In fact, the two blue piezos on the left are their own little array in series.

On the other hand, ANY wire snipped on the plans version would cause the whole array to shut down (I think?). The signal must enter one end and go through every piezo to get back.

That tells me you have more than one path to the amp within the array itself, and there is certainly a shortened path as Sydney points out.

I hope that make sense. I have to go see an eye doctor now....

[Sydney]

ANY wire snipped on the plans version would cause the whole array to shut down

Correct! That's why tapping off side buses ( T'eed off ) has an advantage over a daisy chain jumper. A breaker in a buss jumper takes out ONLY 1 device. Circuit integrity is less dependent on any 1 connection - with the exception of the SERIES bridge connection.
The crude analogy I was taught early on: Is it's like water distribution in a plumbing system - Sort of like having the shower on it's own distribution line from the toilet - instead of T-eed on a shared line ( to avoid "flush scald" ).

[gdougherty]

I'm not going to attempt to figure out your scheme, for fear that if I didn't suffer from dyslexia before that I would after. The scheme used by David, save for the extra wire between the banks in his original, is what's in the plans.

I think Tim nailed the summary, on the left it's two sets in parallel but they're all tied on to the "mini array" of the first two. It's basically like a straight array just wrapping back and forth as it progresses to the end of the set.

[LelandCrooks]

I'm not going to attempt to figure out your scheme, for fear that if I didn't suffer from dyslexia before that I would after. The scheme used by David, save for the extra wire between the banks in his original, is what's in the plans.

[DaveK]

Electrically, both circuits are the same. With all the upper bank + terminals bussed together and all the - terminals bussed together, you should be getting equal current flow through each tweeter in the bank. The jumper to the lowe bank is on the same tweeter as the input, but it shouldn't matter since the resistance across the tweeter is much higher than from one end of the buss to the other.

Here are some troubleshooting ideas.

1) Check that the wiring really does match the diagram.

2) Measure the resistance from one end of each buss to the other. It should be an ohm or two. If more, look for a bad connection.

3) Feed a sine wave signal to the array and measure the AC voltage on each + terminal. It should be the same on every tweeter in the bank.

4) Check for mechanical problems like proximity to a hot woofer magnet

[jbell]

I thought piezo's were capacitive load, not resistive load.... And, electricity always finds the shortest path. So even though they 'look' the same, they are not.

Just to make sure each element is driven evenly, I was considering using dual cat5, running a distinct pair to each piezo, and then parallel/series wiring them together back inside the cabinet. That way, each piezo has exactly the same length of wire going to it.

[Bill Fitzmaurice]

That way, each piezo has exactly the same length of wire going to it.

Totally unnecessary. You really have to stay away from sites populated by oddiophiles.

[Sydney]

gdougherty
So, in summary every time you used the "end fed" wiring scheme on the left - the piezos ( colored in blue - closest to the amp feed, and series bridge ) ALL showed the same behavior and fate?
Did you have a resistor in the piezo circuit ( it's not indicated on your drawing )
Did you test resistance as per DaveK idea #2.

[jbell]

oddiophiles ?? Maybe I resemble that remark and since I'm a computer geek by day.. yes, I use an excessive amount of cat5, and since I'm a musician/geek, I balance everything, even wiring length.

In the diagram to the left, the shortest electrical path is between the left middle 2 piezo's, so they'll take 90% of the power, fail, and then it's on to the right middle pair, fail, etc... till they're all gone.

In the diagram to the right, power has to make it through the entire length (down and back up) there is no 'shorter path.' so all piezo's have a chance at providing useful output.

[gdougherty]

gdougherty
So, in summary every time you used the "end fed" wiring scheme on the left - the piezos ( colored in blue - closest to the amp feed, and series bridge ) ALL showed the same behavior and fate?
Did you have a resistor in the piezo circuit ( it's not indicated on your drawing )
Did you test resistance as per DaveK idea #2.

Up till now I've not had a resistor in-line, no. I've always used amps that had no problems with the piezos (Peavey GPS2600 and QSC PLX3602). As I'm putting these back together though I'm adding a resistor just in case it does make a difference.

Yes, in every scenario where I've used a wiring scheme similar to the left side I ended up with dead piezos in those blue spots. Of the 4 arrays I just pulled apart and tossed all 12 tweeters, all 4 had 4 dead or near-dead piezos in the middle.

In the melded array I've always had issues with distortion even at moderate volumes, I'm guessing because those middle sets were being fed too much power and overdriving while the others did fine. All the individual piezos tested out normal without distortion and a similar sound. I'm picky enough about the sound that I toss about 1 in 5 to get a semi-matched set.
On the distortion I've been told check my gain structure and I have. Based on the signal levels I ran from board input to crossover output I find it unlikely that any of the chain is the problem. My inputs everywhere are at lower volumes and the amps are wide open, limiting is at the crossover at -20db in the DCX and I never hit it. Also, my piezo loaded Wedgehorns never exhibited any distortion problems despite sharing a good chunk of the signal chain but the wedgehorns are wired like the diagram on the right.

I'm going to play sometime in the next day or two with the full system again and test things that consistently gave me distortion but I'm now pretty sure my wiring was the issue.

Another interesting note, with a 12 element melded array wired like the right hand side diagram, the middle of the array sounds louder than the sides when you listen up close with the array in free space. I have the same behaviour on all 4 arrays. Further back you can't tell.

[gdougherty]

Electrically, both circuits are the same. With all the upper bank + terminals bussed together and all the - terminals bussed together, you should be getting equal current flow through each tweeter in the bank. The jumper to the lowe bank is on the same tweeter as the input, but it shouldn't matter since the resistance across the tweeter is much higher than from one end of the buss to the other.

I thought the same thing, but I'd already swapped the elements on one full array before because it seemed to be having problems, and now I've done all 4 as well. That's after only about 20 hours of moderate use indoors. You're welcome to wire them like the left hand side, but I just spent $100 and 8 hours swapping 4 arrays and I'm not conforming to the definition of insanity by doing the same thing and expecting different results.

1) Wiring matches the right hand side, it really did match the left before.
2) & 3) I may do that now, but if they work fine, I'm not going to bother.
4) It's in an OT12, woofer is on the wrong side and doesn't run hard enough to get that hot.

[Sydney]

If you intend to follow the right hand wiring scheme I would "replace" the green jumper with the recommended resistor ( 8 -10 ohms?)
* IF I ever get to the point of making a piezo array I 'll use a distributed buss ( like mentioned above, for the reasons listed above )