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Inherited 6 La Scalas - Need some assistance please


Ed Wolinski

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Hi. New to the forum. Been looking at a lot of posts; very helpful! So here I am...Proud owner of 6 (yes 6) Klipsch La Scalas that I recently acquired. I am going thru them one by one testing the components. I have a few questions that perhaps some could possibly help me with. First, these are one piece cabinets. First, it looks like I need the proper ohm reading for the tweet, squawk and woofer (so I am sure if good or bad). One tweet reads zero; I will have to find a viable supplier.  These solid black cabinets are circa 1980ish... Serial numbers are as follows: 1966, 1967, 2002, 2003. These have AA crossovers. Serial numbers (with aluminum exterior framing) 1430& 1433 have AL crossovers. Second, I will assume that most responses will say to replace the caps in the AA xovers, which I can easily do. The AL xover I am not too sure about. Looks a lot more sophisticated with more electronic parts. Reading the forums, would also assume that the AL xover needs to either be modified/upgraded or replaced. Any help would be greatly appreciated. Thanks in advance!

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Jim from JEM is also very knowledgeable and helpful. We speak regularly and he’s done a great job updating his page with some of the more relevant things we’ve talked about. 
 

The AL looks intimidating but it’s really not that bad. Two 4’s will be paralleled for the 8uF, and I found 15uF polyester at Solen that can be paralleled for the 30uF. I actually  don’t see the issue with an electrolytic here, since Klipsch used them in the AL-3.
 

I would personally use the AL-3 in place of the AL, since the AL, like the AK-2 - was part of the EV mixup and is improperly balanced. 
 

EDIT: I forgot to add that since JEM is an authorized Klipsch dealer, they also sell replacement diaphragms for the K-77.

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Ed, your aluminum La Scalas with the AL crossovers are the “Industrial” version, LSI (La Scala Industrial). They should have a different woofer than the others, the K-43. I quite prefer the K-43 in a LaScala. It’s all that and a bag of chips in this application.
 

You could quite easily do an apples to apples comparison with your windfall.

 

Take a pair of AAs from two of your non industrials and swap them into the LSIs. Run a pair of each, regular and industrial , with the AAs for a while with familiar music and see which sounds better, apples to apples. 
 

When you have decided, throw the ALs back in the LSIs and see if it appeals to you.

 

The AA crossover is a benchmark.

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Thanks for all of the rapid and helpful replies!  I really appreciate it.   I understand that JEM is in Bethel Park, PA. I am actually not to far from there. I will contact him soon for the K-77 diaphragms. Picture? No problem; 1 attached! (I had to crop it to get to the 2 MB max limit)... I'll get a few more up tomorrow. Inside the xover/squawk horn area is remarkably free of dust for cabs this old. Can I please have the correct ohm readings for the drivers and woofer? I am seeing variances from 5.6 to 10.5 ohms...Next project on the board is pull the 15's, inspect cones and remove dust. I will take up the advice on swapping the AA/AL and advise. Would all of you agree that recapping the AAs at this point is the ticket? IF so I will get them from JEM also. Thanks again for the help. I really appreciate it. Some of the other boards (especially home distilling) I am on really diss the new guy. Not like that here ands it is really nice. One really off the wall Non-Klipsch question, if I may....anybody have a Biamp model 1642 or 2442 sound board collecting dust? I have one in near perfect condition; my board repair service guy says it needs a transformer and he cannot find one anywhere. 

6 Klipsch.jpg

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I have read thru some of the postings about the advice about replacing the 'magnetic' screw with brass or stainless steel, and plan to replace them all today. My questions on this are: exactly how does the magnetic screw affect the sound, and, given the crossovers are 40 some years old, will this make any discernable difference? 

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1 hour ago, Ed Wolinski said:

  how does the magnetic screw affect the sound, 

 

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  On 12/29/2020 at 10:34 PM, baron167 said:


Tested and confirmed screw is magnetic. Were the screws used during development and testing not magnetic? What is the significance of it being magnetic and why do they need replaced? Thanks

 

correct , the screws were messed up during production  , they were meant to be non-magnetic -The AA  tweeter circuit   has a 245uH air core inductor with a non-magnetic screw  ,   with a magnetic screw  , the 245 uH bumps to 350 uH - 

 

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22 hours ago, Marvel said:

The ones I had in my first pair sounded terrible.

 

But at the time, correct caps weren't available.

obviously , there was something wrong with the crossover caps or the drivers or the driver combination , to my ears , the AL sounds great  with the EV /K-55M  , and  Finally as you said , JEM  offers a kit for the AL (  Approved  by @Chief bonehead  )  .

 

 

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Thanks for the quick reply 001. I can understand the 'bump". I have already checked the screws. All are magnetic. Once I get everything sorted out, cleaned and working, I will take a few moments and road test the audio with and without magnetic screws. Might be awesome to actually hear the difference. 

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In my humble opinion; the magnetic screws sound “better in” per my Khorns (a closer approximation to a live performance - “fidelity”).  Maybe it was a 10+ year production mistake through the 1970s, maybe it wasn’t, but the bit of extra “oomph” in the lower treble makes a big difference, especially with vocals and acoustic instruments. When I took mine out, it robbed some of the speaker’s magic, so back in the screws went. Your mileage may vary, just do whatever sounds best to your ear. The 18db/octave slope should provide plenty of tweeter protection either way. (For a commercial La Scala you may actually want to err on the side of more tweeter protection and use brass screws.)

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10 hours ago, Ed Wolinski said:

I have read thru some of the postings about the advice about replacing the 'magnetic' screw with brass or stainless steel, and plan to replace them all today. My questions on this are: exactly how does the magnetic screw affect the sound, and, given the crossovers are 40 some years old, will this make any discernable difference? 

I steel/iron/ferrous screw near an inductor, generally will lower the value of the inductor, thus changing the crossover frequency. 

 

However, based on a conversation one Forum member had with Bob Crites, about 10 years ago, a crossover with a screw that was “magnetic” apparently bumped up the 245 uH value inductor to 350uH.

 

If you have a multimeter that measures inductance you can check them yourself (which I highly recommend) to see. I can’t speak to what this equates to in the amount of change in XO frequency, and whether it is up or down. @Deang or @Edgar can address that.
 

It is also my understanding that you don’t want a screw that is magnetic or conductive. A conducive screw can also cause changes that can’t be measured, so the preferred material would s nylon/plastic. Some use hot glue to secure inductors to the board, or nylon zip ties. Again, Dean and “Edgar” would know way more about this, what works best, if worth worrying about etc.

 

I’m not sure the magnetic screws were the “wrong screws.” I think what this relates to is the misunderstanding that stainless steel is not magnetic. Some types of SS are more magnetic than others, and even within a type, the amount of nickel can be within an acceptable range and meet spec. The chromium is the key for corrosion resistance and the only tight number “18” for example is it is at

least 18% chromium. When nickel is high in price they put less in and more magnetic that batch becomes. The process on how they make the screws can also magnetize them (cold processing to make heads and threads will cause magnetization for example).

 

Like I say, Edgar and Dean have a lot of experience with what the best way to secure an air core inductor to an XO board would be.

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9 hours ago, Klipschguy said:

When I took mine out, it robbed some of the speaker’s magic, so back in the screws went. Your mileage may vary, just do whatever sounds best to your ear. The

Sound advice.

 

Seriously, go slow, one at a time, to know what you are dealing with, especially if unable to measure the inductance.

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9 hours ago, Travis In Austin said:

I steel/iron/ferrous screw near an inductor, generally will lower the value of the inductor, thus changing the crossover frequency. 

 

However, based on a conversation one Forum member had with Bob Crites, about 10 years ago, a crossover with a screw that was “magnetic” apparently bumped up the 245 uH value inductor to 350uH.

 

If you have a multimeter that measures inductance you can check them yourself (which I highly recommend) to see. I can’t speak to what this equates to in the amount of change in XO frequency, and whether it is up or down. @Deang or @Edgar can address that.
 

It is also my understanding that you don’t want a screw that is magnetic or conductive. A conducive screw can also cause changes that can’t be measured, so the preferred material would s nylon/plastic. Some use hot glue to secure inductors to the board, or nylon zip ties. Again, Dean and “Edgar” would know way more about this, what works best, if worth worrying about etc.

 

I’m not sure the magnetic screws were the “wrong screws.” I think what this relates to is the misunderstanding that stainless steel is not magnetic. Some types of SS are more magnetic than others, and even within a type, the amount of nickel can be within an acceptable range and meet spec. The chromium is the key for corrosion resistance and the only tight number “18” for example is it is at

least 18% chromium. When nickel is high in price they put less in and more magnetic that batch becomes. The process on how they make the screws can also magnetize them (cold processing to make heads and threads will cause magnetization for example).

 

Like I say, Edgar and Dean have a lot of experience with what the best way to secure an air core inductor to an XO board would be.

Hi Travis,

 

Someone modeled the ferrous versus non-ferrous screw in another thread; the subsequent rise in the inductor value (I measured about .34mH) shifted the crossover frequency from 5800 to 4800. Every AA from the 70s I have seen has had the ferrous screws. My ‘81 Khorn had brass.  It took me a while to figure out why I liked my ‘76 better. At first I thought it was the dual phase plug K55 in the ‘81 vs the single phase plug K55 in the ‘76, but when I swapped the K55s, the difference persisted (I could not hear a difference in the single vs dual phase plug K55s and the ‘76 still won the day). Then I changed the caps, but still basically the same (‘76 was still better). THEN, I changed out the non-ferrous screw; the ‘81 & ‘76 suddenly sounded the same (outstanding) - easy fix!  I shared my findings here, but some received the findings better than others. Maybe the ferrous screw was intentional, maybe it was not, but either way the Khorn is a great speaker. I do know the official spec is for .245mH not .34mH, so to each his own. 
 

Respectfully,

 

Andy

 

 

Edited by Klipschguy
Corrected the inductor measurement
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4 minutes ago, Klipschguy said:

Someone modeled the ferrous versus non-ferrous screw in another thread; the subsequent rise in the inductor value (I measured about .32mH) shifted the crossover frequency from 5800 to 4800. Every AA from the 70s I have seen has had the ferrous screws. My ‘81 Khorn had brass.  It took me a while to figure out why I liked my ‘76 better. At first I thought it was dual phase plug K55 in the 81 vs the single phase plug K55 in the 76, but when I swapped the K55s, the difference persisted (I could not hear a difference in the K55s and the 76 still won the day). Then I changed the caps, but still basically the same (‘76 was still better). THEN, I changed out the non-ferrous screw; the 81 & 76 suddenly sounded the same - easy fix.  I shared my findings here, but some received the findings better than others.

That’s fantastic info. That a pretty significant shift in the XO. Obviously audible. In terms of preference, doesn’t surprise me a bit that that an accident/mistake/anomaly could be preferable by one, some or many. 


Sorry I didn’t recall that (I may have missed it b/c of the great zener diode depart that was raging at or near the time.


Nothing ever goes well that bursts the myth of ears vs. readings. Kind of like choosing Pepsi over Coke in a blind test. PWK wrote in Dope From Hopes of dealers identifying problems with dips, or peaks, etc. and he would check them out, confirm, come up with a correction, and usually a kit. He would credit and thank the dealer or person who identified the problem/issue.
 

what I really like to is your approach once you identified a difference/preference. Step by step, one variable at a time. 
 

So we know for sure they went to brass around 80 or 81? I will ask Jim Hunter what he knows about this.

 

Travis

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