K 500-5000 crossover help, please.

[windashine]

Thank you for posting that, I saw that earlier this evening and thought about putting it up here, but just glad you did... one topic had me over in the Dope from Hope section lol... the Jan 66 vol 7 no 1 was relative to the L2, just take PWK's word.... 

[Deang]

13 hours ago, Klipschguy said:

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

 

 

 

 

The varnish is yellowing because it's breaking down and becoming brittle. It's dried out and cracking.

 

Coils block high frequencies. The series inductance is so high it's effectively not doing anything. Replacing half century old autotransformers isn't going change the voicing.

 

If you're worried about maintaining the voicing, then use the capacitor type recommended by PK (clearly marked on the schematic). :-)

[Klipschguy]

On ‎10‎/‎1‎/‎2018 at 10:05 AM, Deang said:

 

The varnish is yellowing because it's breaking down and becoming brittle. It's dried out and cracking.

 

Coils block high frequencies. The series inductance is so high it's effectively not doing anything. Replacing half century old autotransformers isn't going change the voicing.

 

If you're worried about maintaining the voicing, then use the capacitor type recommended by PK (clearly marked on the schematic). :-)

 

Well, for all practical purposes, the Klipsch autotransformers do not block the highs.  Yes, the T2/T2A autotransformers have inductance as measured across the taps, but the autotransformer is not acting as an inductor in the circuit, but rather it is acting as a transformer.   [And just in case someone may be interested: When an autotransformer receives a resistive load on the secondary winding (from a voice coil), the resistive load is then reflected as a higher impedance in the primary winding, commensurate with the turns ratio (autotransformer has taps).  The higher impedance in the primary winding is then presented to the amplifier.  When the amplifier sees the higher impedance, it results in less power to the driver, hence attenuating the relative volume of the driver.  An iron core inductor, on the other hand, does not have primary and secondary coils like a transformer, it is just a 2 terminal wire wrapped around an iron core.  Inductors do indeed come in handy for blocking high frequencies.]  Admittedly, not all of the Khorn crossovers use the autoformer for the tweeter leg of the circuit (like the Klipschorn AA network, for instance), but other Heritage speakers, such as the Cornwalls, do use it and the "inductance laden" T2As certainly pass the highs effectively.  Should autotransformers be used at all?  Well, that question is for another day. 

 

Also, the old varnish on the T2's metal screw down strap won't affect the sound in the least; the strap's only function is support the iron core autotransformer so it can be held to the crossover board with the 2 wood screws. (Why is there even varnish on the strap? Corrosion resistance? Who knows.)  The iron core, magnet wire assemblies retained within the straps are in perfect condition with no evidence of drying, or cracking, or corrosion.  The pair of T2s I am using test well within spec on the bench and all taps test within 10% of a newer T2A I have (Klipsch specs allow 15% variance from published specs); there is no reason they are not just as good as the day they left the factory.  Additionally, the taps match the old wiring diagrams to avoid possible future confusion.  Does the additional inductance and resistance of an extra tap in the circuit affect the voicing?  (The crossover does have the full inductance of autotransformer between the + and - inputs.)Well...maybe, maybe not. 

 

Regarding using the correct capacitors to voice the crossover?  Um, of course...that goes without saying (but I am pretty sure you were joking).

 

No worries,

 

Andy

[Deang]

4 hours ago, Klipschguy said:

Well, for all practical purposes, the Klipsch autotransformers do not block the highs.

Right, that is what I meant, the inductance is so high, they aren't blocking any higher frequencies -- so how does not using the original T2 impact voicing? In your initial response to my recommendation to dump the old units, you said:

 

On ‎10‎/‎1‎/‎2018 at 11:05 AM, Deang said:

... the T2 taps have a little different inductances versus the T2A ... 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

All the T2A did was add an extra tap. Newer versions add even more taps. All that matters is the attenuation level you use -- the inductance doesn't matter

 

Varnish or wax is used to displace the air and hold the windings in place. If the windings become loose, they move off of the core. The windings can also rub against each other - neither are desirable. I just don't see any benefit from using parts that old, yet see several upsides to replacing them. 

 

No, I wasn't joking about using paper in oil or something like a Jupiter. These parts sound much better than metallized types.

 

Thanks for the autoformer lesson. Too funny.

[Klipschguy]

Here is an old thread that has some information about the K400, the K5J, and the K500-5000 that someone may be interested in if they run across this thread while researching older Khorns.

(Dean, I am glad you enjoyed the transformer lesson - it was pretty fun typing it. Also, my T2 windings are solid, tight, and have no loss of wax or any cracking of the enameled wire; the yellowed varnish is on the stamped silver metal strap with the screw holes in it as a some type of protective coating.  We are just on different wavelengths with that varnish thing - too funny.)