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Youthman

Possibly Have a Bad AA Crossover in One LaScala - Need Help

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23 minutes ago, JohnA said:

 

Mostly.  The K-77/T-35 has a hair-sized leads

-  I always thought the T35-T35A-T350- ST350    used the same diaphragm 

 

I have a few pairs of used /unused   T35 -T35A-T350-ST350  ,  some are 8 ohms DCR ,  some 6 -6.2 ohms  DCR - 

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I did some additional testing today and it's definitely the crossover. Swapped XLR cables for Left and Right channel on the processor, swapped XLR cables for left and right channel on the amp, replaced speaker wire to left speaker, all with same results.

 

I just reached out to JEM Performance Audio - https://jemperformanceaudio.com/

 

Klipsch has authorized them to repair Heritage speakers to factory spec. Most others modify or "upgrade" the crossovers with what they feel are better components. I would prefer to keep them as close to what PWK designed.

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10 hours ago, Youthman said:

 

 

I just reached out to JEM Performance Audio - https://jemperformanceaudio.com/

 

Please shoot us a picture of the repaired Crossover --it would be neat to see the end result as far as the new capacitors  they may use in the rebuild of the AA xo--

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14 hours ago, Youthman said:

I did some additional testing today and it's definitely the crossover. Swapped XLR cables for Left and Right channel on the processor, swapped XLR cables for left and right channel on the amp, replaced speaker wire to left speaker, all with same results.

 

I just reached out to JEM Performance Audio - https://jemperformanceaudio.com/

 

Klipsch has authorized them to repair Heritage speakers to factory spec. Most others modify or "upgrade" the crossovers with what they feel are better components. I would prefer to keep them as close to what PWK designed.

Can't you just disconnect one of the zener diode wires and re-test?  It is under a screw, simple to do.

 

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1 hour ago, RandyH000 said:

Please shoot us a picture of the repaired Crossover --it would be neat to see the end result as far as the new capacitors  they may use in the rebuild of the AA xo--

They will just stick some Mylars in there.

 

I wonder what they do if it's a bad autotransformer? 

 

 

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What they mean by. Factory specs is this
Using the same value of a capacitor to replace the Klipsch oil can capacitors. I am almost 99.9% sure they’re not gonna put in Klipsch oil can capacitors . you’re gonna be paying 4 to 5 times more just for them to do this , as opposed to getting a Bob’s crossover kit and putting it in yourself. His kits even come with the instructions on how to do it. You were able to remove that Tweeter and switch it to the other speaker? Then you’d be able to upgrade your crossovers yourself. It is super easy


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33 minutes ago, Deang said:

 

I wonder what they do if it's a bad autotransformer?

very logical  , a bad autotransformer  or solder joints  in the circuit   -

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These things are starting to get very old. I stopped doing rebuilds using the original parts when they began showing up with the windings on the T2A's completely off the core. I could hold them up and shake them, and the whole deal would move up and down the core. I would imagine most of them are doing this by now. Just because something still works, doesn't mean it's ideal -- and they do fail -- just ask Carl. 

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12 minutes ago, carlthess40 said:

What they mean by Factory specs is this: Using the same value of a capacitor to replace the Klipsch oil can capacitors.  I am almost 99.9% sure they’re not gonna put in Klipsch oil can capacitors.

The old cans were polyester in oil, but they were film and foil (not metallized). Those no longer exist. I''m pretty sure they are just going to use an axial wound metallized polyester/Mylar. My guess is that they are getting them from Erse (which just so happens to have every Klipsch value ever used). 

 

https://www.erseaudio.com/Products/PEx250v

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The leads to the diodes are soldered to the spade for the tweeter.  You can't just remove the spade.  You can unbolt one of the diodes with a small wrench, ~3/8", and let it hang.  Too easy not to try. 

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On 8/25/2020 at 11:57 PM, codewritinfool said:


8c1e9a3ad778f75f004bccb41b495da3.jpg

I will attempt layman’s terms...

The zener diodes are the two things on the metal bracket in the center of the photo above. Each of them has a wire that goes to the tweeter part of the terminal block. Disconnect at least one of those wires.

Those devices clamp the signal going to the tweeter should there be an overvoltage transient, thereby protecting the tweeter from damage. That’s the idea, anyway. The can go defective and that could affect the frequency response. Some people don’t like them in the circuit at all.

I’m not certain what parasitic effects these might have during normal, correct operation.... you might not get exactly the same response when you’re done between the center / right and this one once you take the diodes out of circuit. If it fixes the gross curve error, you probably found your culprit.

Please post results

Youth, you can just take the nut off the back of one of those zener diodes and remove it from the metal plate. This will break the connection. No need to cut wires or un solder. Just then don't let any part of it touch anything else. Wrap in electrical tape would be prudent.

 

Apologies to John A, I did not see your post at first.

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Don't intend to hijack this thread, but are there any benefits to disconnecting the zener diodes from my LaScala wuth AA networks (rebuilt about 12 years ago with Sonicaps)? I currently have the SMahl with DE120, so I understand that the diodes aren't necessary. If so, do I just remove one nut and let it hang as has been suggested in this thread?

 

Thanks

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34 minutes ago, Ray_pierrewit said:

Don't intend to hijack this thread, but are there any benefits to disconnecting the zener diodes from my LaScala wuth AA networks (rebuilt about 12 years ago with Sonicaps)? I currently have the SMahl with DE120, so I understand that the diodes aren't necessary. If so, do I just remove one nut and let it hang as has been suggested in this thread?

 

Thanks

Yes, you certainly can remove them from the circuit that way. Not pretty but an open circuit is an open circuit is an open circuit.

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Long while since I have posted in the Klipsch forums. I have watched your vids about the left speaker location and have a possible theory why it's happening. I hate typing much so if you are interested in discussing send me a PM here or over on AVS and we could discuss via the phone.  

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On 8/27/2020 at 12:48 PM, Ray_pierrewit said:

Don't intend to hijack this thread, but are there any benefits to disconnecting the zener diodes from my LaScala wuth AA networks (rebuilt about 12 years ago with Sonicaps)? I currently have the SMahl with DE120, so I understand that the diodes aren't necessary. If so, do I just remove one nut and let it hang as has been suggested in this thread?

 

Thanks

it's a very good protection circuit  for any tweeter --the only difference being that the DE 120 has a higher  power rating -but it's still a tweeter 

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The de-120 will take 40 watts. You don’t need the zeners. If you’re paranoid, put in a polyswitch paralleled with a 200 ohm 10 watt resistor. 

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Considering the relatively meager investment, you might consider an ALK "Super AA" crossover. I think it's about $120 for the pair. What they do is take your old crossovers, and send you a pair of modded AA's (still on an original Klipsch crossover board) that have been fully tested, keep the diodes in the loop, and in the unlikely event that your unit does have a faulty autoformer, he will charge you a replacement fee for a new one. Considering the investment, and quick turnover time (assuming there isn't a long waiting list) you will remedy any issues with out of spec or faulty parts. The biggest benefit to me (and I'm just another mere mortal with subjective tastes) was the improvement in sound over the stock units, as well as the Crites xover with the 4500hz cutoff on the squawker. I will say the the Crites CT-120 tweeters are damn good, and since I needed them for higher power handling with the lower crossover point, and work great with the ALK Super AA's if you wanted more power handling. Also, if you were curious to try the Crites xover (which you may prefer to the ALK unit I mentioned), you will have the tweeters recommended for them. 

So, start small and try the least expensive option with the rebuilds and you can keep your K77's and if you don't yield a significant improvement, you can drop an extra $500 to try the Crites

A4500 and CT-120 tweets, or about $350 on Crites' AA units and keep your K77's.

Again, I found the ALK to be more musical and balanced throughout the frequency spectrum than the A4500. I would only recommend the ALK to another member because it's the least expensive way to get started. This advice is coming from someone who dropped a whole lot more $$ on the ALK extreme slope xovers than I ever envisioned when I initially bought my La Scala's second hand to fulfill my teenage dream to own a pair. I just finished my final upgrade with the aforementioned xovers and a pair of Elliptrac 400 midrange horns (I swear honey, I won't spend any more money on stereo equipment ;)). I just posted a picture in the technical modification section if you're curious.  

I'm a greenhorn on this forum, but I grew up with single Klipschorn in my living room powered by a Mac 30 and a Fisher FM-80 mono tuner. This was over 55 years ago so stereophonic sound was still an option/upgrade for many folks. Audio has been my hobby for almost fifty years, and I have been tinkering with things the entire time. 

Thanks to the research I did on this forum, I was able to embark on this journey without running into any costly dead ends. Albeit, not inexpensive if you go whole hog, but all money well spent because I was able to resell my crossovers on ebay, and both pairs sold within days (if not hours) after I listed them. 

Hope I didn't bore or piss off anybody, and may you resolve your problems quickly and painlessly.

 

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On 8/27/2020 at 12:48 PM, Ray_pierrewit said:

Don't intend to hijack this thread, but are there any benefits to disconnecting the zener diodes from my LaScala wuth AA networks (rebuilt about 12 years ago with Sonicaps)? I currently have the SMahl with DE120, so I understand that the diodes aren't necessary. If so, do I just remove one nut and let it hang as has been suggested in this thread?

 

Thanks

 

 

Yes.  The diodes chop off the waveform going to the tweeter at about 2 watts.  The result is a harsh, hashy sound that is unpleasant.  The original K-77 had to have them when larger SS amps got popular.  K-77-Ms need them in pro use and it one of the reasons people hate La Scalas when used in bars. 

 

40 watts is +16 dBW.  +105 dB/w/m = 121 dB continuous.  That is more than your ears can take. 

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7 minutes ago, JohnA said:

 

 

Yes.  The diodes chop off the waveform going to the tweeter at about 2 watts.  The result is a harsh, hashy sound that is unpleasant.  The original K-77 had to have them when larger SS amps got popular.  K-77-Ms need them in pro use and it one of the reasons people hate La Scalas when used in bars. 

 

40 watts is +16 dBW.  +105 dB/w/m = 121 dB continuous.  That is more than your ears can take. 

ok , so say , You have the K77 round magnet in Heresies and CW  ---in B and E  networks  -but no zener diodes -------and they still sound harsh ------any suggestion

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