Internals of the RF7 lll

[parlophone1]

What does the letter "J" stands for on the iscriptions on capacitors? Just curious.

[mustang_flht]

2 hours ago, MechEngVic said:

It looks pretty good compared to other high end Klipsch crossovers, at least it has air cores for the small coils, and no 0.05 cent caps.

 

Now we just gotta find the coil values. Double check my sketch for mistakes.

 

Experience and cheaply change C1 2.1μF (you can for example put 1.8 + 0.3 to make 2.1) and C2 8.2μF by higher quality capacity: Clarity Cap, Jantzen, Solen, ...

 

[STSOE]

47 minutes ago, mustang_flht said:

Experience and cheaply change C1 2.1μF (you can for example put 1.8 + 0.3 to make 2.1) and C2 8.2μF by higher quality capacity: Clarity Cap, Jantzen, Solen, ...

 

I am pretty sure i am going to use a 33 from Mundorf and Jantzen on the other two.

[mustang_flht]

The parallel components have less influence on the sound than the serial components, change first 2.1 and 8.2 μF for a better sound 😉

[STSOE]

13 minutes ago, mustang_flht said:

The parallel components have less influence on the sound than the serial components, change first 2.1 and 8.2 μF for a better sound 😉

Exactly. That's why i count on Jantzen on those two and Mundorf on the 33 just because it's a bit cheaper but still resonably good.

Edited December 9, 2019 by STSOE

[pzannucci]

Don't forget to swap the in-line resistor to a Mills or better.

[STSOE]

14 minutes ago, pzannucci said:

Don't forget to swap the in-line resistor to a Mills or better.

I know. But i haven't made a final decision which ones i am going for yet.

[STSOE]

3 hours ago, MechEngVic said:

It looks pretty good compared to other high end Klipsch crossovers, at least it has air cores for the small coils, and no 0.05 cent caps.

 

Now we just gotta find the coil values. Double check my sketch for mistakes.

 

Man, i haven't made one of those for years. But yeah i thing you got it right. 👍

Edited December 9, 2019 by STSOE

[glens]

Except (at least) he's showing metal cores on the two high-pass coils...

[pzannucci]

25 minutes ago, glens said:

Except (at least) he's showing metal cores on the two high-pass coils...

🙂 not air core.  We get the picture though 😉

 

[mustang_flht]

In my opinion, R2: 12 ohms + L2 is just an impedance adapter for the filter, so there is no need to replace them because it's not for the sound.

[Deang]

I wouldn't worry about C3. That part is perfectly fine for that position.

 

A 2uF is going to run very close to 2.1 anyways. Just use a 2uF.

 

https://www.parts-express.com/audiocap-ppt-theta-20uf-200v-film-foil-capacitor--027-724

 

This for the 8.2uF

 

https://www.parts-express.com/jantzen-audio-82uf-alumen-z-cap-100-vdc-aluminum-foil-capacitor--027-4620

 

Those are film and foils. If you're going to do this, might as well do it right.

 

Use Mills resistors. There is only one better resistor and they're overkill for this project. The best source is www.soniccraft.com

 

[glens]

So, Dean, please describe the effect of those components being swapped in.

[Deang]

Metallized polyesters out, polypropylene film and foils in. The Mylars sound harsh/brash. Good film caps don't have that quality. The sound is cleaner and more relaxed - not strident. Very noticeable at the volume levels most around here use. 15 years of doing this has convinced me that people are listening much louder than they care to admit. Some cheap metallized capacitors have a grainy quality at low volume levels, this also goes away when you use films.

The following was written by Bob Stout, and industry insider. He was good friends with a lot of people, including Tom Danley:

 

Following are my personal guidelines which others have found to be useful:

1. Film and foil is superior to metallized film, if you can tolerate the size. By superior, I mean primarily, lower noise. Capacitor noise is generally caused by flaws in the dielectric or poor terminations. The reason film and foil is "better" than metallized foil is one of metallized film's special "features". You will hear vendors speak of metallized foil as self-clearing. All this means is that if there's a pinhole in the film, a temporary arc will vaporize the metal around the pinhole. This is great for long term viability, but bad for noise since each time this happens, it adds noise. Also, most don't tell you that this only happens when the leakage current through the pinhole is adequate to heat the metallization to the point of vaporization. This is primarily a factor in polypropylene, since of all the popular high-stability dielectrics, it's the softest and therefore most likely to: a) have pinholes as received from the film vendor, and/or b) develop pinholes during winding. Finally, although the theory is that this only needs to happen once per pinhole, after which the metallization around the hole is blown away, it often doesn't work that way in practice. In the real world, all the metallization around the pinhole won't necessarily be cleared by the first (or second or third or…) peak.
2. Especially with polypropylene, the best caps used two layers of film. Doing so virtually guaranteed that the inevitable pin holes wouldn't line up. Single film and foil polypropylene is, unlike Teflon and polystyrene, only somewhat better than metallized film. Note: Most manufacturers consider whether or not they use two layers of film to be a trade secret, so you'll almost never see it advertised. However, it's often a safe bet that film and foil capacitors with excellent reputations are quite likely to be using them. At one time, AudioCap Theta's were noted as using two layers of film, but you won't find that factoid in any current official information. One notable exception is Intertechnik, whose Audyn-Cap Plus premium caps are advertised as "double wound".
3. Although significantly heavier, tin foil is generally preferable to aluminum foil, although the degree of improvement is debatable. Presumably, this is due to fact that tin is softer, resulting in less residual stress and reduced susceptibility to microphonics.
4. Stacked foil caps are generally better than wound caps since the material isn't stressed during assembly.
5. Impregnated paper caps (the paper is typically kraft paper and the impregnant is usually either oil or wax) can be quite good for audio, although for a number of non-technical reasons, they're less convenient and economical to use than plastic film types. Offering extremely low leakage/high resistance (but at the expense of high dissipation factor and often high inductance), they're still one of the best choices for high voltage work, but that hardly applies to audio. Of the choice of impregnants, wax offers significantly improved mechanical damping, but only at low temperatures - at higher temperatures, the wax melts and any advantage is lost.
   There are very few sources of impregnated paper caps for the simple reason that most manufacturers simply don't want to mess with them. Whether they offer audible improvements in crossover designs is a debate I really don't care to get into - akin to the tube/valve vs. solid state or LP vs. CD debates. As with the tube/valve vs. solid state debate, there are measurable differences and no shortage of explanations on both sides why people might prefer one over the other.
6. Polyester (Mylar®) capacitors should be avoided for all critical applications! If your budget's tight, try using them in trap or Zobel circuits before putting them in the signal path. With poorer electrical characteristics across the board than polypropylene or polystyrene, Mylar® is the entry level for film capacitor dielectrics. For non-critical systems where cost is a major issue, they're at least better than NP electrolytics.
7. Polystyrene is a dielectric which is superior to just about all others. It's electrical properties improve on polypropylene and even Teflon®. Some premium crossover capacitor lines are made with polypropylene, but do they offer any audible improvements? As with many other issues, the improvement of polystyrene over polypropylene has been hotly debated. Many of polystyrene's electrical advantages (e.g. lower temperature coefficient) are irrelevant for crossover work where temperatures are relatively stable and drivers have looser tolerances which drift much more with temperature than crossover components. What's not arguable is that polystyrene has a much lower dielectric constant (K) than other dielectrics, so polystyrene capacitors are correspondingly larger for the same values.
8. Avoid oval caps! They're made by winding them round, then flattening them in a clamp while the epoxy sets. This leaves a lot of residual tension which can lead to value creep and microphonics.
9. Everyone buys their raw film from the same suppliers. Any vendor claiming to use, e.g., "premium" polypropylene film is, at best, exaggerating. Note that this applies generally to *virgin* film. You can also buy recycled PP film which is generally used for non-critical applications such as packaging and wrapping, or where only the mechanical properties are important. Although I don't know of any capacitor vendors who exclusively use recycled PP film for capacitors, it would be naive to assume that none do. Certainly, the type and class of capacitors I was discussing (MIL spec, low-noise, high reliability) all use virgin PP film.
   "Raw" polypropylene typically comes in pellets, either from a chemical company (usually virgin) or a recycler. Further clouding the issue, pelletized PP may contain a mixture of virgin and recycled material. The pellets are then fabricated into film by a mill, which may, or may not, be related to the raw material supplier. Finally, the mills are the folks who actually supply the film to the capacitor vendors. In the case of metallized films, yet another intermediate vendor is usually involved.
10. The biggest difference in vendors is QA of the winding operation (for wound vs. stacked foil caps, obviously). Constant light tension is required. This is especially critical with polypropylene since it has such little mechanical strength and stability (i.e. it stretches, tears, develops pinholes, and permanently deforms easily!)
11. The attachment of the metallization/foil to the leads is critical. This has to be a relatively low temperature operation or the film will be compromised. Poor attachment increases ESR and can introduce noise caused by rectification and/or thermoelectric effects.
12. If the rest of the structure is sound, the lead material is immaterial. Tinned OFHC is as good as you'll ever need.
13. Popular audio voodoo is that there's some magic in which lead is attached to which foil. These are all non-polarized parts! Since there are such wide tolerances in the component materials, capacitors are wound to a target value, then unwound as required to achieve the exact target value and tolerance. Until then, which foil is which is undefined.
    A couple of final notes are in order…
    Some well-regarded brands do sell exactly the sort of flooby dust that the preceding discussion attempts to debunk. As we all know by now, there's very little correlation between audio quality and marketing hype. I'd never rule out the possibility of a capacitor vendor marketing flooby dust, while still delivering top quality parts. The trap and the fallacy is in thinking that the parts' quality derives from the marketing claims, rather than simply sound engineering and manufacture.
    DIY'ers spend ridiculous amounts of money for voodoo caps, when they could buy better caps, in most cases, from a wider variety of vendors if they only knew what to order. "Audiophile" caps are priced around the same as MIL spec caps, yet often have less to back up their claims of superiority.

 

I am not convinced the resistors sound different, however, I do go back and forth on this. I once swapped them out for some Ohmites and thought they sounded a little brighter. I always wondered if the inductance in a resistor is actually accounted for, and what happens when you remove it - or if it even matters. Some smarter than me claim is may affect a tweeter's response. Sound aside, the Mills feature all welded construction and you can lift them off the boards. One could justify their use just on build quality alone.

 

http://www.vishay.com/docs/31801/mra.pdf

[Deang]

10 hours ago, parlophone1 said:

What does the letter "J" stands for on the inscriptions on capacitors? Just curious.

 

The tolerance. J = +/- 5% K = +/- 10% M = +/- 20%

[MechEngVic]

19 hours ago, parlophone1 said:

What does the letter "J" stands for on the iscriptions on capacitors? Just curious.

The J is the tolerance of the resistor, J is +or- 5%

[MechEngVic]

9 hours ago, Deang said:

 

The tolerance. J = +/- 5% K = +/- 10% M = +/- 20%

you beat me to it.

[STSOE]

12 hours ago, Deang said:

I wouldn't worry about C3. That part is perfectly fine for that position.

 

A 2uF is going to run very close to 2.1 anyways. Just use a 2uF.

 

https://www.parts-express.com/audiocap-ppt-theta-20uf-200v-film-foil-capacitor--027-724

 

This for the 8.2uF

 

https://www.parts-express.com/jantzen-audio-82uf-alumen-z-cap-100-vdc-aluminum-foil-capacitor--027-4620

 

Those are film and foils. If you're going to do this, might as well do it right.

 

Use Mills resistors. There is only one better resistor and they're overkill for this project. The best source is www.soniccraft.com

 

Hey. I'm glad you chimed in. I was hoping you would see this thread at some point.

Have you done any Rf7 lll crossovers yet?

I know you where popular with the older ones.

 

Also very pleased to see that you recommend the Alumen cap. That must mean that i am on the right path at least.

I don't know the Audiocap though. Why not use an Alumen for the 2.1 too? Is the Audiocap better?

And thanks for the resistor recommendation. 👍

Do you have any thoughts on the internal wiring?

Edited December 10, 2019 by STSOE

[glens]

Thanks for the synopsis, Dean.  I'd reckon any wound-resistor inductance would most certainly not affect anything below where the tweeter tops out anyway.

 

So if you bought a new pair of recent Heritage (or Pro with some) you'd yank the caps?

[STSOE]

4 minutes ago, glens said:

Thanks for the synopsis, Dean.  I'd reckon any wound-resistor inductance would most certainly not affect anything below where the tweeter tops out anyway.

 

So if you bought a new pair of recent Heritage (or Pro with some) you'd yank the caps?

I seem to remember that you were pretty sceptical a couple of pages back? Are you a believer now? 😉