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Help for my father-in-law's Cornwalls


BT Raulerson
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Hello.  My name is Brian Raulerson and I'm hoping to get some helpful info for my father-in-law.  He retired recently from the Florida Theatre as the sound technician.  He has owned these speakers for quite a while now but hasn't been using them.  I gave him a Harmon Kardon digital receiver to take advantage of them to go with the TV I got for him.  Based on what I've read on the forum here the speakers are Raw Birch Cornwalls built in 1979.  As far as I know there has been no maintenance done to these speakers so I would assume that the caps are shot.  I would like some advice on a few things regarding these speakers.  1) Should I replace the caps regardless of condition?  2)  The speaker cabinets appear to be painted.  Should I refinish them with stain/poly?  3)  The class D amp doesn't seem to satisfy these speakers.  Any recommendations as far as amps go?  I built a 200 wpc amp using ICE power boards (made by Bang and Olufsen).  Would that work or do these prefer analog power?

 

Thanks for any information you can give.

 

P.S. Sorry for hijacking that other post!

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Hello @BT Raulerson, and welcome to the forum. Cornwalls are fun. They come alive the moment sound comes out of them.

 

Looks are secondary to sound for me so let’s get to that first. You mentioned the amp used now doesn’t seem to satisfy these speakers. What is it that is lacking to your ears, which are all that matter.

 

I was fortunate enough years ago to have a pair of ‘79 Cornwalls at the same time I had a pair of ‘84 Cornwalls. I preferred the ‘84s so I sold the ‘79s. I think a lot of that had to do with the design of the crossovers specific to each production run though. Neither were re-capped.

 

Up until ‘81 they had the “B” crossover with simple first order crossover slopes, the harder you push them the harsher they sound. They “fall apart” fast.

 

From ‘81 to ‘83 they had the “B-2” crossover with second order filters on the woofer and tweeter using the same drivers that are in your ‘79s. 

 

From ‘84 until the release of the Cornwall 2 in ‘86 they had the “B-3” crossover, but it used a different midrange so it is not applicable to your ‘79s

 

If you replace the caps you will hear more energy in the squawker and tweeter, for better or worse. If you change to a B-2 crossover you will likely find an improvement in the sound you perceive. New caps are probably the way to go, but there are several philosophies on which to use. Hopefully others will chime in with their direct experiences with these. 

 

But that tweeter in your ‘79s should be the very fragile round magnet Alnico version so you if you listen too loud you could blow it easily. I think they are rated for 2W (!).

 

When I auditioned the ‘79 Cornwalls before buying them the seller had them hooked up to an AV receiver that had some inherent EQ and they sounded amazing. Upon further inspection at home I found one tweeter was in fact blown. I replaced them both with the more robust square magnet K-77-M before eventually selling them.

 

As to your amp, all woofers love watts, but gentle slope crossovers don’t. Give that 200 watter a go and be careful with the volume. Somewhere around 9 o-clock should give you a big smile without frying your tweeters.

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Thank you for all of that info.  My father-in-law has quite a few stories about these speakers.  Sadly most of them would probably qualify as abuse stories.  I'm no audiophile but to me it sounds like the speakers are starving for power.  There is almost no bass response at all.  I used a little bluetooth tube amp and ran some modern 'music' from Youtube and turned the treble down and the bass all the way up  and they would shake the floor with the amp I made.  Running them on just the HK receiver there is almost no detectable bass.  The speakers are very close together and about 8" from the wall.  Certainly not what I would call an ideal set-up.  I am going to see if he will allow me to do a crossover swap with modern parts and see what that gets us.  I figure that as long as I don't use Mundorf caps I can get away with about $35 for both crossovers.  Someone from the help desk emailed me a link to the Cornwall crossover designs here.

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Hi Brian,

 

If possible get them in the corners angled towards the listener; it will make a huge difference in the way they sound. Paul Klipsch had plenty to say about the advantages of corner placement, including considerable bass reinforcement. 
 

Secondly, Paul Klipsch liked the sound of 1st order crossovers, but went to steeper slopes mostly to help protect the tweeters from abuse. Keep the Type B networks and replace the caps. I personally like the General Electric motor run capacitors (inevitability, disagreement always erupts over “which caps”, but the GE caps test remarkably well on the bench with spot on capacitance and very low ESR - plus they sound good).  You will need 2 2uf and 2 4uf caps for the job. Use 2 sided clear Gorilla tape to stick them to the board. You can put the old screws back in the holes for safekeeping. 
 

If you keep the power clean, you should be able to turn the Cornwalls up very loud without damage.  Abuse would be clipping the amp with the treble control turned all the way up; that is a great way to fry your tweeters. For home use, even at impressive levels, you should be just fine; just keep it clean and “sub-ridiculous.”

 

Your cabinets are raw birch that look to be stained, not painted (although it is hard to tell from the pictures). If they are stained, you could mix boiled linseed oil and minwax stain and go over the cabinets with the mixture and a green superfine scotchbrite pad. Buff lightly with the grain and then wipe off any excess with the best bath towel you can find. 
 

Just my opinion. Let us know how it turns out. 
 

Andy

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With regards to no bass, I wonder if the HK receiver has it’s main speakers set to “small” instead of “large” or whatever the HK equivalent nomenclature is?

 

I had an Onkyo (still do) that cut off the bass under 80hz when set to “small”. 

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I got a used HK AVR 1510 for him from Facebook marketplace.  It shows it is rated for 75 watts per channel but the thing was probably only 5 or 6 pounds.  It was really, really light.  My brother's old Sansui receiver from the 80s has to weigh 60 pounds.  I know, class A vs. class D.  I'll check the settings when I visit him next.  

 

Klipschguy, I have a question.  Why do you prefer the 'industrial' caps versus 'audiophile' caps?  I dabble in crossover design and DIY speakers and I have a lot to learn.  I would love to hear what you've discovered by using different caps.  

 

I will admit that the way speakers work in general is almost like magic.  I don't understand how or why they work but there is something so special about great sounding speakers.  Add to that your source and amplification as well.  It's a team effort.   You play the right music on a great set-up and it can lift your spirits, help you relax, get you crunk, or put you 'in the mood'.  It is literally a disc shaped thing flapping back and forth in a wooden box and it somehow changes the way your brain works.  I don't know what else to call that but magic.  I'm hoping I can restore some of that magic for Tommy and his old Cornwalls.  

 

Thank you all for your help with this.

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1 hour ago, BT Raulerson said:

I got a used HK AVR 1510 for him from Facebook marketplace.  It shows it is rated for 75 watts per channel but the thing was probably only 5 or 6 pounds.  It was really, really light.  My brother's old Sansui receiver from the 80s has to weigh 60 pounds.  I know, class A vs. class D.  I'll check the settings when I visit him next.  

 

Klipschguy, I have a question.  Why do you prefer the 'industrial' caps versus 'audiophile' caps?  I dabble in crossover design and DIY speakers and I have a lot to learn.  I would love to hear what you've discovered by using different caps.  

 

I will admit that the way speakers work in general is almost like magic.  I don't understand how or why they work but there is something so special about great sounding speakers.  Add to that your source and amplification as well.  It's a team effort.   You play the right music on a great set-up and it can lift your spirits, help you relax, get you crunk, or put you 'in the mood'.  It is literally a disc shaped thing flapping back and forth in a wooden box and it somehow changes the way your brain works.  I don't know what else to call that but magic.  I'm hoping I can restore some of that magic for Tommy and his old Cornwalls.  

 

Thank you all for your help with this.

I have experimented with a bunch of different capacitors, both in listening tests and on the bench. I like the way the GE oil filled capacitors sound (others will disagree, which is fine).  The quality control is always tight in my findings as well. Their caps are rated at +/- 6%, but I usually find them closer to 1%. ESR numbers look good too. Also, in my mind, I like to think the oil damps microphonics (but I may be reaching a bit here). I have replaced a bunch of old Klipsch oil filled caps (for others and myself); the ESR creeps up on those old caps causing the highs to sound rolled off.  The new GEs have ALWAYS made an improvement to my ear that was not subtle.  After decades of experience with Klipsch Heritage speakers coupled with a good ear: replace your caps. 

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19 hours ago, JRH said:

21T174 shipped 8/10/79 to Stereo Systems, Inc.  I would not change the oil-filled caps unless they are leaking oil (or if you measure them to be off-spec).  DF is very low.

I am not necessarily in disagreement with JRH. Most of the old, oil-filled caps have an ESR value which is creeping up and should be replaced, but an exception I have seen is the 13uf caps in Khorns; many of those test good as new. One thing for certain, the old caps are not getting any better with time. 

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  • 2 weeks later...

They sound wonderful and wide... airy and not harsh or over analytical. Exactly what I was going for. The k75-10 bypass caps are still coming in the mail. Mbgo-2's did a great job. I feel like I upgraded drivers. Next I will be trying a comparison between k75-10 and ksg silver/micca bypass caps on tweeter and mid squalker. 

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Very happy to hear of your success with the Russian MBGO-2 caps.  I made a similar change from cheap Solen polypropylene caps to equally cheap Russian MBGO-2 caps, and the improvement was astounding:  a more natural dynamic full bodied sound well textured, better depth.  Can not believe all that cap nonsense I read about for so long was true....

 

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On 7/31/2022 at 3:51 PM, BT Raulerson said:

...... I'm no audiophile but to me it sounds like the speakers are starving for power.  There is almost no bass response at all.  I used a little bluetooth tube amp and ran some modern 'music' from Youtube and turned the treble down and the bass all the way up  and they would shake the floor with the amp I made.  Running them on just the HK receiver there is almost no detectable bass.  The speakers are very close together and about 8" from the wall.  .......

 

The very opposite is true.  People run Cornwalls with 2 watt tube amps.  You have a room placement issue.  They should be at least against the wall and as least as far apart as the listener is back from them.  There could be other issues with the room, too.  Cornwalls do not lack bass unless a woofer failed.  Check and turn off all EQ in the receiver and set the speaker size to "Large".  Set the receiver to "No Subwoofer" and 2 channel only until you add other speakers.  If there is an adjustment, set the speaker impedance setting to 4 ohms so the amp will deliver the current the 4 ohm woofer needs. 

 

Listen a while before changing the caps to be sure they need them.  Do not use cheap caps; each one should be a film and foil cap and you should expect to spend $70 each, or more, to provide the quality the speaker deserves.  Metalized foil caps will sound gritty. 

 

I will recommend lining the openings for the squawker and tweeter with heavy felt to absorb reflections off that edge.  Perhaps unneeded, but lining the woofer opening won't hurt. 

 

P_20190826_152541_1.thumb.jpg.833dcbf17d5fa098e4c26827d5aec82d.jpg

 

Unless your F-I-L intends to so with surround sound, a stereo receiver would be a better, and simpler, choice. 

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A lot of interesting points in post above.  Speaker placement is paramount, and will take many iterations and adjustments.  While against the wall will produce most bass, there can be a compromise there in terms of balance and depth of image.  Toe in will also greatly affect imaging, but some may prefer little or no toe in.  Find your own best spot after moving the speakers around methodically for a month or two.  I still bump mine ever so often, then bump them back.

 

The quote of OP and the nature of the amp used point towards very poor amp to speaker match not producing the desired bass output.

 

Finally, the felt lining the edge of the horns very interesting ( I mean that in a good way, not the usual vague whatever ).  Believe felt can be used to good effect in other spots too, your mileage may vary.

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I read an paper discussing foam around the mouth of audio horns to absorb reflections/diffractions.  Since many foams are short lived and too thick, I used 3/4" felt.  Clean and easy and it's been there since 2000 or so.  Other things made more audible difference, but I'm still a little subject to audiophoolery.  🙃

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