BLEW ANOTHER HORN

[Jerrold Tiers]

The factory horn is an aftermarket CTS Peizo tweeter Similar to KSN1188A

I literally MELTED the first one, the copper winding was actually melted together and the plasic housing was dripping. There is a circuit board on the inside of the cabinet which reads Dayton Audio ( car audio / audiophile manufacturer) but I cant guess what kind of resistor stage it might have, but I'm thinking it's insufficient. The bottom line is, IMHO, that a 1000 watt rated cabinet needs a sturdier horn than the one it has.

Most horns are efficient enough that they MUST have attenuators, which limit the power getting to them..... and mean the horn need not handle super-high power.

The piezo driver in the link claims it has a transformer inside it to boost the signal and efficiency. That sounds similar to a "LeSon" type, which is made in Brazil. May be a copy of it, since the patent has probably expired.

That type DOES use a "real" crossover, with capacitor external to the driver, usually, and the internal transformer operating as the coil of the L-C filter.

Sounds correct, due to mention of the "melted coil".

If it is that type, it HAS to have the external capacitor, or it will burn right up, melting etc, as described. Maybe that capacitor croaked the first time, and the second tweeter then had no chance.

Normally, those "boosted piezos" are efficient enough that they require an attenuator, as noted...... maybe the attenuator got burned up and let full signal through?

A regular piezo is less efficient.... needs more signal, but also can handle more.

If it were a regular old-type piezo, it would act like a "lossy capacitor", and you could attenuate it with an external capacitor of a proper value. Or, using the application note at the link to the part (partsexpress), there are a bunch of other ways to attenuate and control frequency response. Most of those do NOT apply to the type with the transformer, though.

The slow rolloff of a piezo that has NO extra filtering usually leads to the tpical "piezo quack". I would assume Basson had something in there..... which now is suspected to be bad, due to all the damage caused to the tweeter itself.......

 

[Thor]

Pablomigraine, the 'link' didn't work for me.

I see, there are 2 http syntaxes in there.

I noticed a little article on partsexpress that
enumerates everything I don't know about piezo
tweeters.

Invalid Link Removed

I'm going to have to save that somewhere, very informative.

 

[steveksux]

I thought I heard piezo's had lower impedance for higher freqs, and high impedance for lower freqs. Essentially they act as their own crossover. If that's true the piezo is already blocking the freqs the cap would be added to block.

So if that's true, they're redundant, which could be basically the same as what Bill Fitz said in a slightly different way.

Randy

 

[Jerrold Tiers]

I thought I heard piezo's had lower impedance for higher freqs, and high impedance for lower freqs. Essentially they act as their own crossover. If that's true the piezo is already blocking the freqs the cap would be added to block.

So if that's true, they're redundant, which could be basically the same as what Bill Fitz said in a slightly different way.

Randy

A straight piezo IS a capacitor, pretty much, but it can still be attenuated with a capacitor, or a resistive attenuator....

Problem is, it is a 6 dB per octave rolloff, which is REALLY slow, and lets through way too much low end, usually, hence the "piezo quack", which unfortunately is not "just ducky".

The Le-Son type setup, with a transformer inside, using a "real" crossover, MUST have the external cap or it burns up. Without it, there is a low-value coil from hot to ground...... draws plenty of current..... With the cap, there is an L-C filter for crossover, and a step-up transformer to increase the voltage and hence the output from the horn.

IF the link is correct, then it is that type....... and presumably need a cap.... Otherwise, who knows. The Basson website does not go into great detail....

But the regular old-type piezo wouldn't have any "copper coil" to burn up........

 

[Thor]

That is very interesting, thank you for the explanation.

 

[The Clap]

Sorry Joe, not true. You're entitled to your opinion on the worth of tweeters for bass but your opinion doesn't alter the facts, and the facts are that the harmonics of the electric bass go beyond the range of human hearing. If you choose not to have them in your signal that's all well and good. But please stop telling the rest of us that we're not entitled to hear what we want to from our instruments.

No kidding! For all the numbers Joe Beets passed around in that rant, there was a distinct lack of knowledge and understanding behind every contentious premise. At least I don't see anything about the 'Threshold of Farting' in this thread yet.

 

[ZoomBoy]

I have completely melted yet another comression horn driver in my Basson Cabinet. Now, Basson has been awesome, and has replaced them for free, but I just don't think the tweeter they use in thier cabs is up to par with the speakers. By the time you're throwing enough juice into the cab to get those huge frikken magents pumping, you're already in danger of frying the little horn.....anybody know where I can get really heavey duty horn replacements?

When I blew mine they made me pay for it and I've talked to Shawn many times on the phone during the order process etc. Nice. Oh well. I don't use my Basson cab much anymore. I just turn the fricken tweeter off now. I'll probably trade it towards a Bergie.

Jeff

 

[rpatter]

A straight piezo IS a capacitor, pretty much, but it can still be attenuated with a capacitor, or a resistive attenuator....

Problem is, it is a 6 dB per octave rolloff, which is REALLY slow, and lets through way too much low end, usually, hence the "piezo quack", which unfortunately is not "just ducky".

The Le-Son type setup, with a transformer inside, using a "real" crossover, MUST have the external cap or it burns up. Without it, there is a low-value coil from hot to ground...... draws plenty of current..... With the cap, there is an L-C filter for crossover, and a step-up transformer to increase the voltage and hence the output from the horn.

IF the link is correct, then it is that type....... and presumably need a cap.... Otherwise, who knows. The Basson website does not go into great detail....

But the regular old-type piezo wouldn't have any "copper coil" to burn up........

This reminds me of something I ran into on a pair of PA speakers I repaired once. They had off the shelf 12db/octave crossovers in them. The guy was running them with one of the QSC RMX amps and said the horns kept blowing. Once I got them opened, I found out why. The coil on the high pass side must have been only 22-20ga and in both speakers they had gotten so hot, the bobbins were melted down! Somehow the coil was so fried that the horn was only seeing the capacitor, which was not enough. After replacing the diaphragm in the horn and building a 3rd order fuse protected crossover for the horn (with heavier gauge coils) the problem went away.

Ralf

 

[pablomigraine]

well, there's a couple of very interesting ideas about possible problems before the tweeter. I have a a meeting today with VIctor Basson, and per his message he thinks he's sorted this all out. Whatever it turns out to be, I'll post here immediatly, that is unless this whole string hasn't degenerated into a Horn Vs. No Horn cage-match.

One thing I want everybody to bear in mind here, I've had this cab for three months, gigged it probably 20 times. I told Shawn Green at Basson about the problem. This is what he said:

Mon, 8 Aug 2005 09:18:00 -0700 --- Hi Paul,

Horns are not a problem for us unless the end user is doing something
odd.
I can't explain why your having the problems you're having and I'm not
going
to make excuses. We will gladly refund your money. Please return it to
Rhythm Section and we will deal with it from there.

Sorry for your trouble.

Shawn Green
Basson Sound

Now, try and get that kind of service out of Ampeg, Fender, or anybody other than the high end makers once you've owned it for 90 days.