Jantzen Cross-Cap?

[PaulMB]

I have to order about half a dozen crossover caps and a local supplier has these Jantzen "Cross-Cap," which I've never seen mentioned or recommended. They are cheap, but I was wondering if anybody has used them. I'm not after anything sublime, just something that does the job adequately for a low-budget restoration.
Thanks in advance.

 

[James]

They are fine. I've used them before. They are the blue ones in this picture.

 

[PaulMB]

Thanks, James! If you used them that is a guarantee in itself.

I'm just re-doing a friend's old AR-7s, which have a 6.0uF electrolytic from around 1978. So I'll combine 2 of these Jantzens to get close to 6.0, say 2.2 + 3.9, or 5.6 + 0.39 or something.

Thanks again, and I hope you are still working on your wonderful speakers. If you were not on the other side of the world or I'd ask if I could drop in and have a listen.

 

[oceanobsession]

cross caps are black , z caps are blue ,

 

[James]

cross caps are black , z caps are blue ,

You're absolutely right. Sorry Paul. That said, I haven't had anything duff from Jantzen.

 

[awkwardbydesign]

I have them in my crossover. I don't know anything against them at their price point.

 

[James Evans]

Yes, I've used them as well. Good for the money.

 

[PaulMB]

Thank you, all. I'm sure they'll be OK. Certainly better than the 40+ year old electrolytics.

Thanks again.

 

[Pac1]

A word of caution. Polys and electrolytics have different ESR values and you can shift crossover points if replacing electrolytics with polys. Mundorff do good quality, cheap bipolar electrolytics which almost certainly will outperform older 'lytics. I'm guessing at 6uF though, this will be in the HF section, so ESR values won't be significantly different at the frequencies involved. It is an issue for the LF part of the circuit in most speakers though. (just worth a mention)

The other inexpensive Polys worth considering are good are Solens, available from Falcon Acoustics.

 

[PigletsDad]

The ESR of even a crap electrolytic when fresh is a small fraction of an ohm, at most 0.2, typically less.

In the context of an 8(ish) ohm impedance environment, this can only shift the crossover point very, very slightly; if you push the complex number math through, you are looking at changes of about 2% at most, vastly less than the tolerance obtainable in the capacitance value itself for an electrolytic.

The one place it might make a difference is the low pass section; the effect will be keep the rolloff going further above the crossover point, which is probably a good thing anyway; but this will only be an issue about five octaves or higher up; most systems are way down by then, if this frequency is even in the audio band.

To summarise; losing the ESR will not change the crossover shape significantly in almost all real world circuits.

 

[Pac1]

The ESR of even a crap electrolytic when fresh is a small fraction of an ohm, at most 0.2, typically less.

In the context of an 8(ish) ohm impedance environment, this can only shift the crossover point very, very slightly; if you push the complex number math through, you are looking at changes of about 2% at most, vastly less than the tolerance obtainable in the capacitance value itself for an electrolytic.

The one place it might make a difference is the low pass section; the effect will be keep the rolloff going further above the crossover point, which is probably a good thing anyway; but this will only be an issue about five octaves or higher up; most systems are way down by then, if this frequency is even in the audio band.

To summarise; losing the ESR will not change the crossover shape significantly in almost all real world circuits.

It depends on the cap and on the frequency. The ESR at say 100Hz can be as much as 1 ohm and that is not trivial in terms of LF crossover point shift.

ESR at say 3KHz upwards is much less, as you say, 0.1 to 0.2 Ohms depending on caps.

I have designed, built, or refurbished enough speakers by now, to have learned (by measurement and listening) that swapping out 'lytics in LF and lower bandpass sections of older crossovers will alter the speaker's voicing. Just good advice provided in good faith. People are free to take it or ignore it.

 

[PigletsDad]

I would view a cap with an ohm of ESR as basically shot, and ripe for replacement. Certainly agree it can change the voicing!

As such the change can be better or worse in the context of the particular system.