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Modified RF-25 cross overs, Mundorf supremes and North Creek Inductors

Dave: for those who are interested which series of Mundorf did you use? I am assuming they were one of the paper in oil versions?
 
For those interested I used Mundorf, text copied and pasted from a vendor.
The M-CAP® Supreme has been internationally acclaimed as the ultimate high-end capacitor. It's outstanding sound performance is achieved with a unique combination of advanced technologies. No matter where you use the M-CAP® SUPREME – as a coupling capacitor in your CD player or amplifier, or in the crossover of your speakers, you always get the same surprising and impressive performance.
I have these exclusively in my cross overs and I use the Mundorf Silvers as couplers in my amps. Very smooth and open. SET12 has had good luck with other brands as well but for me these are a slam dunk.
 
The
MCap
®
SUPREME
has been interna-
tionally acclaimed as the ultimate high-end
capacito
r. It is considered today by many
users as a milestone in the modern audio-
phile capacitor generation. Its outstanding
sound performance is achieved with a
unique combination of advanced techno-
logies: Special induction-free SUPREME
winding technolog
y. (see also page 9)
Its subtle
fi
ne gradation of the high tone
range invigorates the entire sound produc-
tion; voices and instruments take shape and
become extremely diverse.
T
echnical specifi
cations:
D
ielec
tric
: Polypropylene
Dielec
tri c s
treng
h:
1 200/800 VDC
Los
s fac
tor
: tan
∂
= 0.0002@1 kHz; 0.0001@10 kHz
D
L
sup8
Supreme capacitors
Capacity
Body
Wire
[μF] ±2%
VDC
 
For some time I've wanted to work on reducing resonance on the plastic cabinet parts of my RF-25s, especially the tractrix horns. There are several sound deadening mats available under different names, Dynamat is kind of the "universal" name for the material. Our local audio store sells a brand called "MOJO MAT" it's a butyl product and seemed good quality. My goal was to apply it to the backs of the horns in an effort to dampen them. This was a very easy project that took about an hour. I completed one speaker and giving the horn the tic tic with my fingernail it was clear that the horn became very solid sounding when compared to the untouched unit in the other cabinet. I also put some squares on the back sides of the lower panels with the same result. After both speakers were finished and re assembled I turned them on and noted a refinement of the sound quality. The area that seemed to get the best results were female vocals although everything came across with a better, more lush sound. I'll be spending the evening doing some critical listening.
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Well they use the exact same design idea in the K510 which is the next pro model down from the K402 (top of the line) the mumps (can't remember where the name came from (Roy Delgado I think) breaks up problems in the corners of the horn. Newer models use the mumps so it obviously works very well. Easy to implement and listen to to see if yo like it.. I think I have said before that I like the Karlson K-Tube design especially the double cutaway with the solid sections of the tube facing to the left and right of the room. The double cutaway version is on the left in the image below. I position these at seated ear level parallel to the floor set up so that from the seated position you are able to look straight down the barrel of each one. I fill the tube with a piece of 25 ppi open cell foam. I prefer these to any of the horns that I have owned for near field listening. Male my tubes out of a two layer roll of standard graph paper. Stores next to no energy does not ring looks like a joke but sounds so good I have no interest in building a more substantial one. One of those "but it's not broken moments".
Try some 25 ppi (pores per inch) open cell foam in the throats of your horns for the first third of the horn length. the kind of foam they use in drum humidifies will work fine easy to find. cleans things up a lot. No negative only positive impact. hope this all helps. Play away. moray james.
 

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I've listened to my system about 4 hrs since this modification to the horns, my opinion is that everyone should do it. The crossover mods took 95% of any edge off these speakers and the sound deadening mat cleaned up the rest.
 
Today I purchased a pair of Duelund 0.01uf tinned copper foil bypass capacitors, I had to buy them they were on sale. My question is that the crossover has 2 caps in the tweeter circuit, Which one will do better with the bypass installed around it? 3 years since my last post on this forum, love the sound of these speakers with the mods.
 
Dave C said:
Today I purchased a pair of Duelund 0.01uf tinned copper foil bypass capacitors, I had to buy them they were on sale. My question is that the crossover has 2 caps in the tweeter circuit, Which one will do better with the bypass installed around it? 3 years since my last post on this forum, love the sound of these speakers with the mods.
Click to expand...
do you have a copy of the schematic?
 
Hey Morey, it's been a while! They changed the production run on the crossover and I have this copy but I'm not sure if it's got correct values on the caps. I've linked it here but would need to verify when I pull the covers off my modified cross overs. I bought 2 caps, thinking that would get the job done. Now I see there are 2 in that circuit on each speaker.
 
I clipped one of these Duelund bypass caps parallel to the last cap in the high cross. With my ear to the speaker there was absolutely no difference in sound. However, sitting back on the couch I felt I could hear more depth from the speaker I installed it on. I put it in and took it out several times with the same result, even turned it around. I went to the humblehomebuilt hifi cap page and read basically what I was hearing. On that page he suggested installing it over the low pass side as well. That's my next mission. I'm going to pick up some small clips and attach them to the caps so I can move them around and pick the location that works best. (before ordering more of them!)
 
The experimenting continues, right now I have these caps crossing the low pass caps. The result is very fine to my ears, it seems to liquefy voices and lower frequency string instruments. This might be where they stay.
 
Dave C said:
The experimenting continues, right now I have these caps crossing the low pass caps. The result is very fine to my ears, it seems to liquefy voices and lower frequency string instruments. This might be where they stay.
Click to expand...
Those Duelund's might lonely for other caps of their own king maybe you should start a progressive "bring home the Duelund saving fund" and repopulate your entire xover with them?
 
Hi Morey, My plan is to order 4 more and cross all the Mundorf Supremes with a .01 Duelund. I've got a busy life but will report the results when I get it done.
 
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