K 500-5000 crossover help, please.

[Klipschguy]

I am helping to restore a pair of vintage Khorns from the late 50s.  The drivers are Stephens 103LX2 woofer (4 ohms, measured), K5J/SAHF squawker, and a 16 ohm K77 tweeter.  I want to use the K500-5000 crossover with the T2 autotransformer (not the T2A with 5 taps, but the old one with only 4 taps).  My problem is there are several versions of this autotransformer crossover (the early 500-5000 with the 3 chokes did not use an autotransformer; I am not interested in that one). 

 

One version has the tweeter running wide open straight off the + input lead only passing through a 2uF cap before reaching the K77.  The squawker is tapped. (I think this is the version used with the Stephens/SAHF/4401, so my focus is more about the other versions utilizing the K77.)

 

Another version has the squawker hooked up to tap 3, and tweeter hooked up to tap 2 (then passes through a 2uF cap before reaching the tweeter).

 

Yet another has both the squawker and tweeter coming off tap 3.

 

All the cap values are the same (an 8uF and a 2uF), they are just tapped differently through the autotransformer.  The tweeter varies from wide open, to tap 3 to tap 2; that is a pretty wide range.  I could use some help gathering information for the correct set up.  Maybe somebody has some vintage Khorns that sound balanced in the highs and mids could take a look at their crossovers and tell me which version they are listening to?

 

Thanks in advance,

 

Andy

[JohnA]

The differences must be due to the squawker and tweeter drivers.  One of the early T-35s was 3 dB more sensitive than the other.  I don't know which one Klipsch used.  The SA-HF was used for a long time, but I don't know whether there are different sensitivities from versions of it.  I cannot find a cut-sheet on the SA-HF or 4401 tweeter.  A teat with a signal generator, volt meter and amp is where you are headed. 

 

From the attached price list, you can see that the T-2 autoformer was available in '57, likely part of the K-500-5000-W2.  I doubt there are any differences besides the extra tap in the T-2A.  You will have to test it with a signal generator and amp to be sure.  Using the T-2 in later versions of the K-500-5000  could have been a voicing decision or in response to different woofers. 

 

Send a PM to funkyhambone before you buy too much test gear.  He has '50s K-horns. 

 

Where in the world are you?  Perhaps there is someone nearby who can help with the testing. 

[Klipschguy]

Thanks, John.  You are always helpful.  I decided after some research and a little time with some test equipment to go with the K 500-5000 that uses tap 3 for both the tweeter and woofer*.  I measured the inductances of the taps on the T2A (five taps) and the 500-5000 autotransformer (4 taps).  Tap #3 on the K500-5000 autotransformer has a little less impedance than tap #4 on a T2A, so it will likely run the drivers a touch hotter. 

Andy

 

*footnote: schematic credited to Bob Crites

[Deang]

5mH is the correct value for that particular Stephens. 

[Klipschguy]

The later K500-5000's move to the 2.5mH inductor probably had more to do with trying to lift the Khorn's intrinsic, sagging response in the 300Hz to 500Hz range rather than the 4 ohms Stephens woofer requiring a 5mH inductor.

 

[windashine]

Hello, when I bought my 54. the sellers had a network modification letter from Klipsch of how to update the 54 network to a late 57, I'd be glad to post it here if your interested, just to view.... nevertheless, it might be noted, I'm just reading this forum post to gain some insight on my crossovers too....

[Deang]

Bob makes things so easy for us, you just have to pay attention. 

 

Check out this thread. I’ll try to get back in here later tonight - I’m covered in solder right now. 

 

 

 

[Deang]

2 minutes ago, windashine said:

Hello, when I bought my 54. the sellers had a network modification letter from Klipsch of how to update the 54 network to a late 57, I'd be glad to post it here if your interested, just to view.... nevertheless, it might be noted, I'm just reading this forum post to gain some insight on my crossovers too....

That would be interesting to see. Please post. Thanks!

[windashine]

just an fyi here, for a Saturday afternoon...

[windashine]

attached... the bulletin mentioned in the above letter

 

 

[windashine]

this schematic is from an earlier post in the forum, referencing a 1955 K500-5000 , but with a red line added, for which my memory escapes me at this junction...

 

 

[Klipschguy]

Thank you for posting, Windashine; that answers a lot of questions! Amazing wealth of information out there.

 

BTW, the Stephens Trusonic 103LX2 is a 4 ohm woofer.  I measured the original, unmodified Klipschorn Stephens' voice coil as 4 ohms (around 3.2 DCR).  The Trusonic 103LX is not the same as the 103LX2; the LX2 is the version found in the Khorn (I think the similarity in model numbers causes confusion and possibly misapplication of a perceived replacement woofer).  Others on this forum have measured their 103LX2 woofers at 4 ohms as well.  Klipsch may have used a 16 ohm version of a Stephens Trusonic in another speakers (like the K-Ortho Shorthorn), but to my knowledge, not in the Khorn.

 

Andy

[windashine]

@JohnA  posted the Schematic for the crossover a couple of lines above, which can be found on the first page of the older topic in this tech/mod for crossovers, which is 12 pages, pinned to the top of the topic list

[windashine]

Andy, will any pictures of your crossover's and K5 squawker or tweeter be forth-coming ?  Will you also be including discussion about exploration of another metal oil can capacitor, such as a Cornell Dubiiler from an electric motor perhap's ?

[Klipschguy]

I will post some pictures when I get a little time.  Also, the oil capacitors are being replaced with Sonicaps.  I wanted to use some paper in oil can caps, perhaps out of nostalgia, but it seems after some research the modern caps are probably a more sound decision.  I am not against can capacitors; I used some metalized poly/oil GE caps to rebuild some Cornwall crossovers about 10 years ago when the GE caps still tested well.  I think companies like GE and Aerovox are now making their oil cans in China, which I do not have a problem with, but my understanding is the quality control has fallen and the caps do not test well.

[Deang]

Nice documentation @windashine thanks for posting it.

 

After looking over everything, it does seem to make more sense to use the 2.5mH. 

 

I don’t understand why you would want to use the original autoformers - those parts are 60 years old. Why not a modest investment in a pair of Bob’s 3654? 

 

When I rebuilt a set of these, I used the recommended 8uF value, but it sure left me scratching my head a bit. I can only surmise that the K-5-J has a much higher Fc than the K-400. 

[JohnA]

Funny, on my own I added an L-3  inductor to my Type AAs.  My center channel Heresy is similar and essentially a Type HIE, now, with an added L-3 and a K-22 from an H700 (SP-12B) 

 

 

[windashine]

@JohnA  I don't have an HIE, but looking at an older cad drawing of one crossover, the tweeter and squawker +'s driver connections are drawn from the - input.... ???  Reverse polarity...

Edited October 1, 2018 by windashine
an hour of reading, without posting, except for this edit add-on

[Klipschguy]

Dean,

 

I decided to use the old T2 autotransformers in lieu of just buying a new T2A pair for a few reasons:

 

1. There are very few moving parts in the autotransformers, so the service life these things is incredibly long.  Except for the yellowed varnish on the old T2 outer casings, they are in great condition.

 

2. Besides having a different number of taps, the T2 taps have a little different inductances versus the T2A. (BTW, I measured the autotransformers for your viewing pleasure; see the chart below.)  I figure the voicing of these crossovers was done by PWK using the T2, so I am trying to keep the voicing of the crossovers the same.

 

3.  The old wiring diagrams for the K 500-5000 show a T2, not a T2A which could lead to confusion in the future for someone else trying to work on the crossovers.  For example, if they hook the leads to tap 3 of T2A, they will be in a totally different zone versus tap 3 of a T2.

 

T2 inductance relative to the 0 tap:

1 = 6.7mH

2 = 15.7mH

3 = 35.9mH

4 = 98.5mH

 

T2A inductance relative the 0 tap:

1 = 2.7mH

2 = 6.2mH

3 = 16.1mH

4 = 39.9mH

5 = 110.8mH

 

 

 

[Klipschguy]

The K400 reaches just a little lower than the K5J (around 50hz or so).  See this thread*:

*Thank you Bob Crites for all your hard work.