Klipsch Cornwall 1 Midrange Horn Question...

[Scott Grammer]

So my 1968 Cornwalls are still dead stock, except for adding crimp-on connectors to the wires connecting the drivers to the crossovers. These were in storage for about 20 years, and have just now been put back in service. All screws tightened, crossover caps test OK but not perfect. A couple of solder connections have been touched up. Here's my question: I kept noticing a particular frequency, if excited by whatever music I was listening to, would be extremely resonant and bothersome. I knew it was in the upper mids, but over the weekend a little spectrum analyzation and a little tinkering with a parametric EQ and tone generator have narrowed it down to approximately 2,300Hz, and it appears to ring out about 8-10dB louder than the rest of the midrange, in both speakers. Any suggestions as to what it could be and how to fix it? 

 

The Q of the resonance is so high that on certain songs one does not hear it at all, while other songs are unplayable because of it. 

 

Thanks in advance for all responses.

[wuzzzer]

Might be possible that the midrange gaskets are old and brittle enough that they’re the culprit.

[OO1]

  klipsch genuine capacitors  would make a big difference in the sound

[billybob]

Going to be interesting to troubleshoot.☕

[Scott Grammer]

15 hours ago, OO1 said:

  klipsch genuine capacitors  would make a big difference in the sound

As far as I know, these are original Klipsch oil caps. The crossover is a real Klipsch type B, and the caps look to be fully original. They still measure fairly well.

[Scott Grammer]

16 hours ago, wuzzzer said:

Might be possible that the midrange gaskets are old and brittle enough that they’re the culprit.

That's possible. I believe they're probably original, and of course they would be 55 years old now. I'll pull them this weekend and take a look at them.

[OO1]

..55 years old  .

[Scott Grammer]

3 hours ago, OO1 said:

55 years old  .

Almost as old as me!

[gigantic]

If your capacitors are 55 years old, they're likely due for replacement. Even if they measure correctly for capacitance, their ESR is likely well out of spec. The resonance could be due to the gasket between the K-55 and the horn- at their age, they're likely dried out, but in my experience that often expresses as sibilance and distortion, but ymmv. Definitely replace the gaskets and definitely recap your networks. It may or may not solve your resonance issues, but it will definitely improve the sound. If the resonance is coming from the horns themselves, there are ways of taming that, but I'm not sure that we're allowed to discuss those things here.

[OO1]

there are no issues with the Klipsch  K-600  horns  

 

[Scott Grammer]

17 hours ago, gigantic said:

If your capacitors are 55 years old, they're likely due for replacement. Even if they measure correctly for capacitance, their ESR is likely well out of spec. The resonance could be due to the gasket between the K-55 and the horn- at their age, they're likely dried out, but in my experience that often expresses as sibilance and distortion, but ymmv. Definitely replace the gaskets and definitely recap your networks. It may or may not solve your resonance issues, but it will definitely improve the sound. If the resonance is coming from the horns themselves, there are ways of taming that, but I'm not sure that we're allowed to discuss those things here.

I actually tested the caps for value, esr, and loss, and they were a tad off. I want to keep things as stock as possible until and unless I decide to go off the deep end and do things that, as you suggested, are not to be spoken of here. 🙂 The gaskets, on the other hand, I will replace and see if that improves matters. Thanks.

[henry4841]

Hey guys, Scott is a tech who makes a living in electronics and understands capacitors better than me and probably most on this forum. My thoughts are a room problem peaking the response and has nothing to do with film caps that rarely fail in a X-over network. 

[Scott Grammer]

On 8/21/2023 at 7:20 AM, henry4841 said:

Hey guys, Scott is a tech who makes a living in electronics and understands capacitors better than me and probably most on this forum. My thoughts are a room problem peaking the response and has nothing to do with film caps that rarely fail in a X-over network. 

Thanks for the kind words.

[henry4841]

2 hours ago, Scott Grammer said:

Thanks for the kind words.

No thanks necessary, just stating the truth. I visited you website and if everything true there you have been doing it a long time. Anyone with a education in electronics understands that modern film caps rarely if ever need replacing. 

[Deang]

A 50 year old motor run that is sweating oil should be replaced. Doesn’t matter how it measures. You don’t have to see it, you can smell it. Also, since when is a 50 year old motor run an example of a “modern day film cap”?

 

There is a good ohm difference between the oil cans in series versus new axial wound dry polyesters. It’s audible. Well, unless you’ve lost a good deal of your high frequency hearing. 

[henry4841]

1 hour ago, Deang said:

A 50 year old motor run that is sweating oil should be replaced. Doesn’t matter how it measures. You don’t have to see it, you can smell it. Also, since when is a 50 year old motor run an example of a “modern day film cap”?

 

There is a good ohm difference between the oil cans in series versus new axial wound dry polyesters. It’s audible. Well, unless you’ve lost a good deal of your high frequency hearing. 

When I was referring to modern film cap I meant the sealed ones instead of the old wax capacitor one sees in really old equipment. Nelson Pass made a comment on a technical forum that he recently tested the capacitors in one of his 40 year old amplifiers and they all tested fine. And the majority are electrolytics. Just saying. 

 

Do not mean to step on your toes Dean but as we both know we do have a disagreement on capacitor replacement. I understand your position on this forum as a long time member building and selling crossovers. Just a friendly disagreement and nothing more, I hope. I am just from the old school if it ain't broke do not try and fix it. I certainly do not want this thread to get into another capacitor debate on this forum. They seemed to always end bad. The forum has seen plenty of that over the years. 

[henry4841]

For any new member or lurker that does not know Dean is Klipsch's authorized dealer for new crossovers and the capacitors the engineers at Klipsch deemed the best sounding for replacement for those that desire to do so. Quality work and fair pricing.

 

I would trust him with my money which says a lot in my book. 

[Scott Grammer]

On 8/22/2023 at 6:48 PM, henry4841 said:

I certainly do not want this thread to get into another capacitor debate on this forum. They seemed to always end bad. The forum has seen plenty of that over the years. 

OK, so while I have been working in audio electronics for a while (since 1977), I am the new guy here, and I understand my place as such. So I definitely would not like there to be a "capacitor war" on my account.

 

That said, I believe there's a lot more to cap replacement in crossovers than "is the old cap really bad." Changing from bipolar electrolytics to film caps can change the sound of a speaker, and not necessarily for the better. Sometimes, a crossover designer will voice a speaker with a certain kind of caps (and inductors, as well) that have maybe a bit more than the minimum ESR (or DCR in the case of inductors). Replacing these with "better" components can change the sound of a speaker considerably. I have a pair of smaller Advents on my main workbench as test speakers, and a couple of years ago I recapped the crossovers (it was necessary, the caps were seriously leaky) and I replaced the bipolar electrolytics with thumb-sized Nichicon film caps. This got rid of the excessive midrange reaching the fried egg tweeters (which is why I checked out the crossovers in the first place), but the VERY low ESR of the Nichicons made the top end brighter than normal. I've gotten kind of used to it, but at first it was bothersome. I may still add some 1 ohm resistors in series with the tweets to tame them down. That is, if I ever have time to fool with it....

 

The Cornwalls I have include what I believe to be the original oil caps. They tested well, and they're not physically leaking oil (and yes, you DEFINITELY can smell it when that happens), so I don't plan on replacing them any time soon. I don't think they're the root of the problem. I will be replacing the horn gaskets soon with some supplied by a friend who used to build PA speakers, and we'll see what that does. I just have to get them - and some time - first.

[Deang]

^This. 
 

Welcome to the forum Scott. 

[Scott Grammer]

Just now, Deang said:

^This. 
 

Welcome to the forum Scott. 

Thank you, sir.