Late to the thread too. Didn't know this one was here.
I got on a similar wavelength recently. I replaced my Mundorf Supreme resistors with Duelund Standard Graphite/Silvers and could describe them similarly to your Cast Duelunds Joman. I am sure yours are better, Duelund obviously knowing what they are doing, but the Standard Graphites are very transparent...like no resistor.
I also have some 3.3 Jupiter flat stacks sitting in my cart waiting for the big decision between Mundorf Silver in Oil (SIO), Mundorf Silver/Gold/Oil, Audyn True Copper, Jupiter Copper, or just staying where I am. I definitely am at a really good place and should/might just stop.
Over the years I have been experimenting a lot with small caps "bypassing" my 3.3 Mundorf Supremes, improving the Supremes beyond adding a little value. It is amazing how a 0.1 cap can influence a 3.3! Difficult logic there for me, but real. It generally makes the big cap better and can morph its sound toward that of the little cap.
Going back and forth between 0.33 Mundorf SIOs, and 0.1 Jupiter HTs doubled, and mixed with 0.1 NOS Russian K40Y-9 (my chosen bypasses for years before trying these more "boutique" caps), I could go either way, both great improvements. But I seem to be settling on the SIOs so far. It is so complete, powerful, and natural sounding without being obvious about being "natural." I am seduced by the vast micro information conveyed so smoothly and quickly....less so by the power, the power being more demanding, but it too can be seductive.
doukhobar.
Yes, the higher cap value increases the high frequency range, lowering the point at which the tweeter falls off. I think it is 6 dB/per octave in this case of using just a resistor followed by (in series) caps before the tweeter.
Resistor value can be great to explore also. In that case, the higher value attenuates the tweeter more...a relatively clean volume adjustment. When I was first exploring Mundorf M-Resist resistors, I ended up with a slightly lesser value 2.7R (and more tweeter volume) because that resistor sound is solid, smooth, dense and powerful...quite detailed, but the detail is less obvious with these other traits. Whereas, I think I get more sense of subtle, supple and spacious highs with a greater value 3.0 Duelund, the Duelund having greater transparency. I like the Mundorf sound a lot...just different signature choices from very good designers, though at this point, the Duelund's "not being there" is more to my liking.
I think most tweeters on ERRs are like those on the HR1s a 5 ohm ribbon. Bob may have been using a variation on that tweeter for a little while, that one being 6 ohms.
Here is a calculator where you can enter cap value and impedance and arrive at the slope-off frequency.
http://www.carstereo.com/help/Articles.cfm?id=1If you have the tweeter that looks like the HR1 pictures, yours is likely 5 ohm. If it has a rectangular ribbon area that is wider, then I am guessing this is 6 ohm ribbon tweeter variation from the same maker, but check with Bob for verification if you get serious about this.
If you calculate 3.3 uF and 3.9 uF, you will see the difference.
Where the mid/bass driver and tweeter cross, and how they do that has some flexibility. Generally speaking, folks tend to recommend staying within 10% of the original calculated cap value, though as JD found, this is not absolute. As I recall, I think the phase can drift if the value is changed too much. Also a very small "bypass" can apparently improve the sound by a fair bit as per the Duelund Silver Bypass with a value of only 0.01 uF. The humblehifi guy says these improve about any cap by about 2 where his scale rarely gets above 12.
http://www.humblehomemadehifi.com/Cap.htmlLately I am preferring mine with a 10% "bypass," my 3.3 Mundorf Supreme (stock value for the HR1) wired parallel with the 0.33 Mundorf SIO....together in parallel 3.63.
With my 5 ohm tweeter, this changes the tweeter bottom frequency slope-off from 9636 Hz to 8760 Hz. Pretty big change. In my case, looking at the charts for my mid/woofer, this is a relatively realistic choice, bringing the crossover points closer together, but so is Bob's design choice of 3.3, more relaxed. However you choose to go, you can let lower highs through more or less. But a "bypass" can also be heard, changing the character of the original workhorse cap while doing a better job of bringing out the whole top with more clarity and coherency if the bypass is an equal or better cap.
What I hear from it is more detail, space, and absolute clarity across the spectrum. Between Mundorf Supreme bypasses of the same 0.33 value and the Mundorf SIO, the SIOs "disappear" more with more micro information, emptier background and more speed. I am always impressed how much the top end effects most every bit of the sound we hear...not just space, air, and shimmer....Deeper "black" with speed, and with smooth and musical accuracy, equals more texture, better ambient and spacial information, better attacks and decays, more nuance....bringing out all levels of subtle information. The mids and bass are richer and more complex with the Duelund resistors and SIO "bypasses."
Though I need more time to come to clear conclusions as to what I keep in, bypassing speaker caps is a very good option to paying more for full value caps, also allowing more tuning flexibility.
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