GabeS Posted January 11 Share Posted January 11 Hello everyone, I recently purchased a pair of vintage 1978 La Scala and overall they sound amazing. I believe they are all original with k 55 v midrange driver and k 77 tweeter and Type AA crossover. On certain recordings (maybe 1 out of 10) I'm hearing distortion from what I assume is the mid-range tweeter. In particular, if distorted piano sound or sometimes guitar comes from that side of the soundstage, it will be prominent. It sounds like an extreme distortion just from the speaker and is usually brief but reproducible on certain tracks. The general soundstage and music aren't distorted - just a distorted sound coming from the speaker. Is there a way for me to figure out what is causing the rattling/distortion? What is the most likely cause? I really appreciate your time and expertise. Gabe 2 Quote Link to comment Share on other sites More sharing options...
wuzzzer Posted January 12 Share Posted January 12 If it’s only in one speaker, swap the L/R wires and see if the problem switches speakers. The very first thing I do with any vintage Klipsch I buy is loosen and tighten all the input and output screws in the crossover. That will remove decades of oxidation and give a much better signal path to everything. Even more so to speakers like the LaScala and Klipschorn that have their crossovers exposed like they are. If the problem is still there, it could be the old oil can capacitors. Contact JEM Performance Audio or forum member DeanG for new capacitors to bring your crossovers back to spec. 2 Quote Link to comment Share on other sites More sharing options...
GabeS Posted January 12 Author Share Posted January 12 Thanks for responding! I will try your suggestion of loosening/tightening the screws. I did swap the speaker cables and it is only the one speaker that has the problem. I'm pretty new to this - I don't think I have the Oil capacitors - and I'm not sure what type they are (or if they are good). I'll try to attach a picture. Is it possible that a capacitor problem would cause a problem at just a single frequency/type of sound? Again, appreciate your input. GSC81F430E-0B4A-40F8-AF64-9F9D8084C220.heic Quote Link to comment Share on other sites More sharing options...
GabeS Posted January 12 Author Share Posted January 12 Here is one more picture. Sorry, running up to the size limit. Maybe there is a better way to post pictures. Thanks again. GSC8B7DB73-A0A9-4152-98E2-4B1618D5A6B5.heic Quote Link to comment Share on other sites More sharing options...
Schu Posted January 12 Share Posted January 12 Probably a bad/leaking Cap 1 Quote Link to comment Share on other sites More sharing options...
OO1 Posted January 12 Share Posted January 12 4 hours ago, GabeS said: Hello everyone, I recently purchased a pair of vintage 1978 La Scala and overall they sound amazing. I believe they are all original with k 55 v midrange driver and k 77 tweeter and Type AA crossover. On certain recordings (maybe 1 out of 10) I'm hearing distortion from what I assume is the mid-range tweeter. take an Ohmmeter and check the resistance for both midrange drivers ....... what are the results for the right and left speaker , the mids are 16 Ohms Quote Link to comment Share on other sites More sharing options...
Marvel Posted January 12 Share Posted January 12 Those caps have been replaced, as Klipsch didn't use the Sonicaps. When you are hearing the distortion, I would check around the upper back to try and isolate where the distortion is coming from, i.e., something loose, wires rattling together. Easy things to notice. Even make sure the k55 is screwed on tight. Welcome to the forums! 2 Quote Link to comment Share on other sites More sharing options...
Invidiosulus Posted January 12 Share Posted January 12 I would pull the white electrical tape off and check the (hopefully) soldered joints where the capacitors were replaced. Is the noise happening on both sides? If you think it’s the midrange you could try swapping the midrange drivers and see if the issue follows the driver to the other speaker. Sometimes if the driver isn’t screwed in snugly, or the gasket is dried up and hard, it can cause some odd buzzing with certain sounds. Is the distortion sound reproducible every time with a specific recording? Does the sound happen only when playing at a certain volume? In some cases the diodes in the tweeter protection circuit can be going bad and cause some irregularities in the response. If the crossover is wired up correctly, and you aren’t cranking a ton of power through the LS, then it should be safe to temporarily disable the tweeter protection by unbolting one of the diodes from the metal bracket. you would want to make sure the unbolted part was isolated and not going to short out against anything. 1 Quote Link to comment Share on other sites More sharing options...
KT88 Posted January 12 Share Posted January 12 8 hours ago, OO1 said: take an Ohmmeter and check the resistance for both midrange drivers ....... what are the results for the right and left speaker , the mids are 16 Ohms 16 Ohms is Z, I just measured the unconnected KV55A with new but original diaphragms at 10,3 Ohms DC to give you a ballpark. 1 Quote Link to comment Share on other sites More sharing options...
GabeS Posted January 12 Author Share Posted January 12 (edited) I really appreciate everyone weighing in and helping me try to figure this out. As I mentioned, the speakers sound great on most songs. Even the distorted songs are only one instrument frequency like a guitar will be distorted in a few parts of the song. The vocal (other instruments) that is playing at the same time won't be. I will try to borrow a friend's Ohmmeter to see how they measure. I did take off the white tape and it seems like the wires are soldered. The same recording will always buzz during the same section - which makes me think a certain frequency is causing something to vibrate. And it does seem to be worse at louder volumes. If it was a bad capacitor could it behave like this or would you expect a more constant buzzing. When I reproduce the sound it sounds like it is coming out of the front of the speaker rather than something I can hear by sticking my head through the back. I can't feel anything vibrating or sounding loud from behind. The screws are all tight. I was also curious what people thought of the capacitors in the picture. Would I be better off trying the capacitors from JEM audio? Appreciate all the help! GS Edited January 12 by GabeS Quote Link to comment Share on other sites More sharing options...
OO1 Posted January 13 Share Posted January 13 13 minutes ago, GabeS said: Would I be better off trying the capacitors from JEM audio? yes Quote Link to comment Share on other sites More sharing options...
KT88 Posted January 13 Share Posted January 13 46 minutes ago, GabeS said: I really appreciate everyone weighing in and helping me try to figure this out. As I mentioned, the speakers sound great on most songs. Even the distorted songs are only one instrument frequency like a guitar will be distorted in a few parts of the song. The vocal (other instruments) that is playing at the same time won't be. I will try to borrow a friend's Ohmmeter to see how they measure. I did take off the white tape and it seems like the wires are soldered. The same recording will always buzz during the same section - which makes me think a certain frequency is causing something to vibrate. And it does seem to be worse at louder volumes. If it was a bad capacitor could it behave like this or would you expect a more constant buzzing. When I reproduce the sound it sounds like it is coming out of the front of the speaker rather than something I can hear by sticking my head through the back. I can't feel anything vibrating or sounding loud from behind. The screws are all tight. I was also curious what people thought of the capacitors in the picture. Would I be better off trying the capacitors from JEM audio? Appreciate all the help! GS To be honest, I had exactly the same problem with my 1977 LaScala...as long as the Sonicaps were in it. There were certain frequencies that were very annoying, especially some single coil PU guitar tones that hurt my ears. In my case it was actually the Sonicaps. Since I swapped them for polyester types, this annoying effect has disappeared completely. In your case, I would also start with the capacitors and order the caps from JEM and try them out. I can't guarantee that it will have the same positive effect in your case because I don't know what else is going on with your speaker. But trust me that switching away from the sonicaps had a significant effect. Not just in terms of eliminating shrill guitar tones. The bass also got better timing and no longer sounded boomy. Roy once said that the Sonicaps didn't just have a different Q value (responsible for shrill notes). They also have a different ESR than the JEM caps, so they mess up the impedance of the whole Xover. Hence the impression of a better bass with the JEM caps. What I'm trying to say is that your capacitors are not bad in the sense of broken. They are simply unsuitable in terms of their sound character. And yes, what others also say, I have interrupted these protection diodes. They are connected in parallel to the tweeter. All you need to do is remove a wire to one of the two diodes. Back then, with the early powerful transistor amplifiers, the loud plops when switching on or off were sometimes the tweeter killers. But the sound suffers with the use of the diodes. I've had my LaScala without diodes for many years and the K77s are still intact. I also listen loudly from time to time, it is important that the xover is wired correctly so that the tweeters are protected. Remember that the tweeters in the previous type A crossover had even more unhealthy bass, and there were no protective diodes in this type of crossover at all. The sound is better without diodes. It's fine as long as your amp doesn't make loud plops when you switch it on. Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted January 13 Share Posted January 13 From your description, there is a good chance you have a bad diaphragm either in the tweeter (K77) or the midrange driver (K55V). Play the distorted passage with your ear beside the midrange and alternately, the tweeter to determine the offending driver. (Piano music is usually good for revealing a bad midrange horn diaphragm.) The original drivers can be repaired. Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted January 13 Share Posted January 13 I have a tone generator app on my iPhone that will produce audio spectrum frequencies; it is useful for identifying room resonances, bad speakers drivers, et cetera. I use a free app called Sonic. A word of caution: Be careful with cranking the individual frequencies of the audio spectrum as it can damage your system. Ex: cranking 20,000Hz trying to hear it can fry your tweeter (“It was only 146dB, but I can hear it!!), or cranking 20Hz trying crack the foundation of your house can damage the woofer. Moderate levels and common sense are recommend. Quote Link to comment Share on other sites More sharing options...
GabeS Posted January 13 Author Share Posted January 13 Thanks again everyone. I think I will try and order some of the JEM capacitors to see if it makes a difference and possibly switch the midrange driver between speakers to see if I can isolate it to that. Is there anything special I need to do to make that change? If it is the driver are they available to replace (I do see some on ebay) or do people get them repaired and if so is there a good source to fix? I do have a local vintage audio store that I likely could bring it to, but not sure if it would be a very specialized repair. Overall the sounds is great on 95% of the recordings, so I'm not in a rush but I appreciate the help from this group. GS 1 Quote Link to comment Share on other sites More sharing options...
GabeS Posted January 13 Author Share Posted January 13 Sorry if this is an ignorant question. I also have a pair of Heresy 3 speakers. I'm guessing they have K-53-TI 1.75” (4.45cm) Titanium diaphragm compression driver based on the spec sheet. It's not possible/advisable to use these in the la scala. Overall the la scala has been a really big improvement over the Heresy. Thanks. GS 1 Quote Link to comment Share on other sites More sharing options...
OO1 Posted January 13 Share Posted January 13 6 hours ago, GabeS said: Is there anything special I need to do to make that change? If it is the driver are they available to replace (I do see some on ebay) or do people get them repaired and if so is there a good source to fix? I do have a local vintage audio store that I likely could bring it to, but not sure if it would be a very specialized repair. Overall the sounds is great on 95% of the recordings, so I'm not in a rush but I appreciate the help from this group. GS unscrew gently , lay the Mids driver down , tighten the 6 screws of the top plate until they are snug tight , the driver is composed of 2 halves sandwiched between a rubber gasket , a loose top cover can cause vibrations or an irritating sound . an Ohmmeter can pinpoint to a problem with the driver's diaphragm if the resistance reading is way off between both drivers , typically a good k-55 diaphragm should measure from 9 ish to 10,5 Ohms , anything lower than 9 Ohms indicates a worn out diaphragm , the replacement is a breeze 15 minutes with a soldering iron and a flat screwdriver Quote Link to comment Share on other sites More sharing options...
OO1 Posted January 13 Share Posted January 13 1 minute ago, GabeS said: It's not possible/advisable to use these in the la scala. correct Quote Link to comment Share on other sites More sharing options...
wuzzzer Posted January 13 Share Posted January 13 If the gaskets on the midrange drivers are original, they could also be contributing to what you’re hearing if they’re dried out. Might as well replace them while you’re at it. 2 Quote Link to comment Share on other sites More sharing options...
GabeS Posted January 13 Author Share Posted January 13 Is there a good source to buy the diaphragm/gaskets? I don't see them listed on the JEM website. GS Quote Link to comment Share on other sites More sharing options...
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