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

I sold a coworker a very simple, affordable system. It is the first decent stereo he has owned. You'd think he had the most advanced system in the world, from the way he describes it. I try not to disenchant him, only encourage him to listen to other systems. He has yet to come over to hear some of my bigger systems.

It really sounds like you had a fun day with your buddy - that is really special when another person can appreciate your stereo like you do.
 
tensleep, it is always interesting to get a neighbor or friend that hasn't heard good sound and set them in the sweet spot. Once I hit the play button on the CD player I just watch the look on their face. 9 times out of 10 they are impressed.
 
Dave C said:
I've got him thinking pretty hard about how good it can sound, we'll see how it goes but he knows I'd offer a hand with his system as needed.
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tensleep said:
It really sounds like you had a fun day with your buddy - that is really special when another person can appreciate your stereo like you do.
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Dave C said:
tensleep, it is always interesting to get a neighbor or friend that hasn't heard good sound and set them in the sweet spot. Once I hit the play button on the CD player I just watch the look on their face. 9 times out of 10 they are impressed.
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Inspiration by demonstration has a way of spreading no doubt :music:

Dave was inspired the same way just as I was from North Creeks work only Dave got to hear North Creeks while it was intuition for me that North Creeks Inductor FAQ's were correct, that gave me inspiration to take what a Klipsch could do perhaps to another level and I was not disappointed. Dave was inspired enough to take the chance as well and if you ask me after hearing his RF25's his work was well rewarded with some beautiful :music:

Certainly the valves helped and it was an easy decision for him to build his 300B's. As he already had PP then he was introduced to world of SET.

For me though it took a little :bash: over the head from another audio buddy to understand what could be heard from valves but finally I got it enough to build a couple of amplifiers of which have been aspiring to others as well.

In the end its really the whole system that counts, Dave is a lucky man to have some of the nicest SET sound I have heard especially with his modified Klipsch, a sound that IMO would be difficult to beat. A sound that I marvel at.

SET12
 
SET12 said:
In the end its really the whole system that counts, Dave is a lucky man to have some of the nicest SET sound I have heard especially with his modified Klipsch, a sound that IMO would be difficult to beat. A sound that I marvel at.

SET12
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Well SET12, You started it all with your invite to hear your system! You introduced me to SET sound and North Creek. Any readers out there that have recapped speakers should also consider replacing inductors with North Creek units, the difference is huge. I was lucky to get a heads up start on all this from SET12. My experimentation has given me a system that is a true joy every day that I sit down to listen to it.
 
Dave C said:
The sound is improved a lot from stock. I need more time with it though. First impressions are it is warmer and better balanced. I'm just not sure the highs are a perfect fit for my ears yet. (real close though!) Looking back, the highs were a bit harsh with the factory cross overs. I'd come to like that I guess. On a side note these speakers are rated at 8 ohms. Just for kicks I put an ohm meter across them today and the meter reads 3.8 ohms. I didn't check them before they went under the knife. Does that sound reasonable?
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This is a really old thread, and that the quote above is from earlier in the thread, but because I am considering some Cornwalls or CornScalas as an interim speaker for my Shindo Haut Brion and Sophia Electric 91-01 amplifiers, speaker impedance is on my mind - my goal has been a pair of Devore O/96's, but too cost-prohibitive right now.

I would be surprised if you designed your 300B amp to handle a 4 ohm load - to my knowledge very few are (except for certain godzilla tube amps). As you may well know, if the speaker impedance is too low, the sound will be restrained in all frequencies, including highs. The whole set up can sound wrong; grey and un-alive. Worse, you could fry a transformer or some caps.

If it were me, unless my amp were designed for 4 ohm loads, I wouldn't use it with this crossover until I got the impedance back to a stable 8 ohms or above - at that point, the high frequencies would likely punch through with more verve. At the very least, I wouldn't spend too much time and parts voicing the crossover until I knew that the impedance was a good match for my amp.

However, since you are very happy with the sound, it is clear that you've done a good job. I'd be very interested to hear from SET12 and Dave C about the current impedance of Dave C's speakers and if his amp has experienced problems. I'm very interested in modifying a pair of Cornwalls and it sounds like the crossover is ripe for fun and relatively cheap mods. Because my Shindo is pretty sensitive to impedance drops, I want to be sure the mods are well executed.
 
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Jceaves, you did a careful job of reading this thread! I have used my amps and speakers together on a daily basis the entire time since this thread started and have had 100% trouble free operation. Because of your input I checked the impedance of each of my speakers again. 3.1 ohm and 3.2 ohm were the results. Yes I never gave much thought to it but the amps are wired to the 8 ohm outputs. Just by chance I purchased and received a set of Plitron output transformers for my amps today. I'm thinking about starting the conversion tonight, mounting is way different and new holes need to be drilled in the amp chassis. After taking these readings tonight I guess I should attach the 4 ohm wires from the new transformers rather than the 8 ohm wires. Anyone with input on this conversation please post your view.
Dave C
 
Correction of details to the last post. OPTs rewired to the 8 ohm taps this morning. When reading speaker ohms through the cross over the readings are not the same as the readings measured on the speakers in the cabinets. Sounds are much nicer wired at 8 ohms. I have gained greatly in sound from the Plitron OPTs, the entire frequency range sound much more linear. The 4 ohm vs 8 ohm experiment was a learning experience relearned.
 
Dave: if your opt has both 4 & 8 ohm taps then using the 8 ohm taps will usually sound better since you are loading the entire secondary winding of the opt yes a little less current but no big deal better than having a huge amount of winding unloaded. Best regards Moray James.
 
After reading this thread, I'm sold on the idea of upgrading the crossover network on my RF3-IIs. Plans are to (as I believe did Dave C) use the Mundorf Supreme caps, along with North Creek 10ga inductors. I do have a pair of 4.7 ohm Duelund resistors, I'm expecting these will tame the somewhat (to my ears) hot upper frequencies. Aside from the deviation in resistor rating from the stock 2 ohm unit, I'll replace all other components with ones of the same value. Taking a queue from Dave C, I'd like to build an enclosure out of 1/4" PVC sheet. My hope is the net results will justify the effort and expense, with a much improved listening experience.
 
javazqu, I think you will love the results! You will need to play around with the Dueland resistor a bit to get the right blend of horn to woofer. I went from 3 ohm to 5 ohm and was happy but an ohm at a time makes a big difference here in how the image comes across.
 
Dave C said:
javazqu, I think you will love the results! You will need to play around with the Dueland resistor a bit to get the right blend of horn to woofer. I went from 3 ohm to 5 ohm and was happy but an ohm at a time makes a big difference here in how the image comes across.
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Dave C, thank you for the feedback! With respect to the Mundorf caps, is there a forum (or other) vendor I can source them from? I'd ask the same question about the Duelund resistors, considering there may be some experimentation to arrive at the best selection for my set-up. The ones I currently have were purchased from an online auction site.

Regards,
José
 
Dave C said:
Jose, I have bought from several places over the years, Audiokarma advertiser
http://www.partsconnexion.com/ has been a reliable source for Mundorf and Dueland for me.
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Dave C, thanks once again for your help. I've got an RF-3 schematic I'm reviewing in preparation for ordering parts but as there may be differences between the RF3/RF3-II networks, I'll pull one from a speaker and confirm. This is going to be a fun project!

Regards,
José
 
I spent the weekend at the Rocky Mountain Audio Fest, I did all the rooms, 11floors of them! I found my system, 300B powered RF25 s to rank with the most transparent, open sounding systems at the show. I also learned that I prefer speakers of 8" or less cone size. In most cases the larger speakers lacked the transparency that I enjoy. I also learned that to my ears the new digital formats are harsh sounding compared to CDs or vinyl no matter what they run them through. All in all I would recommend everyone attend a fest to learn more about how they enjoy listening to music, everyone's ears are different.
 
javazqu said:
Dave C, thanks once again for your help. I've got an RF-3 schematic I'm reviewing in preparation for ordering parts but as there may be differences between the RF3/RF3-II networks, I'll pull one from a speaker and confirm. This is going to be a fun project!

Regards,
José
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from what I recall there is no difference in the RF3 and the RF3 ll network the difference was the use of monster wire, exciting I know. They are the same. I believe they did use a different woofer in the RF3 ll and I expect the roll off of the Mk ll woofer is better behaved and that accounts for the improved performance.
 
Very interesting read gentlemen! Would it be possible for someone to explain or provide a reference to how a person would figure out what values of inductors and caps a person would need when modifying crossovers to this extent? I see it mentioned several times that some of it is experimental as everyone will hear differently. I own many Klipsch speakers and would really like to try these upgraded crossovers to see what happens. The only bad thing will be, as impressive as everyone has been with the modded crossovers, one would be tempted to mod all of them. Thank you for the great read!!!
 
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That is exactly what happened to me! and unfortunately I can not live with the stock networks performance after the experiences of these extreme networks.

With most of the networks one can find the schematics.. Newer speakers might require measurements of the inductors as I did for my R-28F's large air core inductors IMO are the real key to enhancing the performance.
 
I would concur with SET12, the first improvement to make on crossovers is good inductors. Solen and North Creek would be my choices. Second thing is better capacitors, do your research here or open your wallet and buy Mundorf, you won't be sorry. There isn't really a need the first time through to play with the values. Quality components in this area of your system are very important.
 
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