Rebuilding Duntech Sovereign Crossovers

jkess114

Member
2013-02-06 2:59 pm
I just picked up a pair of older Sovereigns. Ouch. I'm making preparations to rebuild the Crossovers. I have settled on Mundorf MOX resistors, but have not settled on which capacitors. There are some rather large caps in there and I can't see a voltage rating on them, so I cannot even know where to start. Each X-over has:

2 @ 50uf (Giant. approx 4" long and 1 3/4" diamter.)
5 @ 20uf (also huge for 20uf. Certainly the same voltage rating.)
7 @ 10uf
4 @ 3.3uf

All of these must be rated at the same voltage. Do any of you know what that is?


Next question is: What are y'all using to recap these? Pros? Cons?

Thanks very, very, much,
josh
 

VaNarn

Member
Paid Member
2010-12-11 12:39 am
Ivanhoe
A picture would help.I have an idea that the capacitors may be of the same type used in early Australian built Dynaudio speakers and these were power factor correction metallised polypropylene types rated for 250 V. a.c. operation.If this is the case then you may not in reality be upgrading unless you can test the capacitance value to the tolerance used by the designer and actually improve on dielectric characteristics etc. of the exiting components
 

kouiky

Member
2009-06-18 4:42 pm
In all seriousness, I would simply use metal film resistors (no carbon types), non-inductive wirewound in higher current areas, and simple film capacitors rated for the highest voltage feasible for a lower ESR. Match them at a close tolerance and bypass the larger values with small bypass caps. I had my day with expensive caps, what a waste.
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
The reputation of Duntech particularly with the Sovereign would have me cautious about changing anything. In particular, you should identify the capacitors which are of the type that don't typically change with age, and leave those. Same with the other components but check carefully for damage, particularly evidence of heat damage while you have them out.

If you didn't like the sound of them then that would be another story.
 

jkess114

Member
2013-02-06 2:59 pm
Hi again-

Before I continue, I'd just like to thank you very kind people for chiming in and offering your wisdom. . .its much appreciated. I'll add some backstory: I am a musician and I've played professionally all of my adult life. I also have run and owned a recording studio for 12 years, specializing in tracking, mixing, mastering, film scoring, & overdubbing. As a rule, I think that people have gone insane with audio-quests. I have spent a lot of time ABX testing components and in my time come across, surprising results - in both directions. At one point I was convinced that I was getting a different result when mixing digitally that just wasn't there upon prodding from others to test my results with different methods. Also, I have debunked major manufacturer claims of recreations of equipment, aided by my main tech and his AP2500.

Another story. . . we were doing some intense AB comparisons between console modifications and upon patching some cables in at one point we both looked at each other at the same time and said nothing. We both heard a difference between different colored patch cables. This was repeatable and we could each tell the which color was being used in the patch. Two things about that: 1) We were working on other more important things at the moment, so after ten minutes of playing with that and checking our sanity we did nothing further with regard to that experience. 2) From that day to present, I care not which color patch cord goes into what, and only think about that to remind myself what is important.

So on to these speakers and their crossovers. While I know my way around recording gear very well, repairing said gear, and having spent more time behind a soldering iron than just about anyone who isn't a technician, I find that I feel stupid in the world of HI-FI. I have no idea really, which components or technology fall under "technically superior" or "silly wastes of money". At the end of the day, its all electrons anyway.


Here is a link to an album containing all the pics for my speakers, including shots of the crossover. Sent to me was a photo of someone else's rebuilt crossover. I sent pics of my crossover to Duntech and the response was that I would hear a very worthwhile degree of improvement if I were to rebuild them. I called Madisound and their techs opinion was I would notice an improvement as well.

So what say you folks who've been around the block a time or two? Here is a link to pics of my speakers and crossovers:

Duntech Photos by jkess114 | Photobucket


Thanks so very much!!!

josh
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
Notwithstanding legitimate maintenance, changing components can sometimes make a small difference. Sometimes this is due to distortions they may contribute to, and sometimes these distortions are a desired thing. Sometimes this is pursued in an attempt to mask the more important speaker issues that ought to be dealt with first. This is all I'd like to say on this issue.

If Duntech themselves suggested a rebuild, I'd want to be interested in why they believe so. Did they give any clues or make any suggestions?
 

jkess114

Member
2013-02-06 2:59 pm
Thanks for the link. One poster seems to thought the rebuild was worth it. I called madisound and they recommended Clarity SA or ESA capacitors. I haven't a clue what the difference is between these series, or, Clarity and any other high end Capacitor. Like so many things in audio, there are generally a few plants that make the stuff, and then its farmed out to other people who paste "marketing jazz" on the outside and let the visuals sell their wares. Who can know whats going on in the capacitor world? Can anyone shed some light for my blinded eyes?
 
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jkess114

Member
2013-02-06 2:59 pm
Allen, Duntech just expressed that newer components/tech do indeed sound better. They said the difference would be rather noticeable. From cursory searching, I am finding components that push this between $402 & $1010. The cheaper version would be going with Solen Fast caps and the more expensive would be Clarity SA's. Both cases factor in Mundorf MOX resistors. Obviously, one can get even spendier, but for what? Are there really fifteen different capacitor factories of high end caps?

I know I sound like i don't know much about this stuff, but thats because I don't. I must assume that chunks of my experience port over to Hi-Fi, but how much I can't say. I do have very sensitive hearing having been a musician my entire life and an audio engineer for 12 years.
 
It really is impossible to generalize in any meaningful way about what capacitors to use in upgrading a particular speaker. Opinions range all over the map regarding the sonic qualities of caps. Some (many on this forum) claim different caps will have little to no effect on sound quality. Others will say they have an immense effect. (I am in the second group.) If you want to explore some reactions to different capacitors, glance over this very lengthy thread:

AudiogoN Forums: Capacitor log Mundorf Silver in Oil

Personally, I would be very hesitant to change any caps in the Duntech crossovers. From your description, they are somewhat complex and use some rather high value capacitors. If it sounds good to your ears in its present state, I would leave it just like it is. If you want to explore some differences in sound, then by all means try a couple cap swaps and see what you hear. Just make sure that you keep the originals so you can put them back in if the "new and improved" versions are not as satisfying. I would try the tweeter caps first since they make such a large difference IMO.

Be very wary of recommendations of specific brands and types of capacitors. In this area price and hype mean very little in terms of actual sound quality. Unfortunately, the only surefire way of finding out what caps you like is to try a number of different ones and that quickly becomes expensive.

Just because a speaker is a decade or two old does not mean that its crossover parts are worn out. I have tested non-polar electrolytic caps in speakers much older than your Duntechs and they have tested just fine. Same thing with the resistors and chokes. There's no reason to think they need to be replaced just because they're old.
 

jkess114

Member
2013-02-06 2:59 pm
Hi Sal electric-

Thanks for the reply. When I have a second I'll check out the link. I will add that I became interested in this strictly because the manufacturer claims that the rebuild will quite noticeably improve the sound quality since my speakers are twenty years old, something that they have nothing to gain from telling me.

But again, thank you for sharing your experience. I will check out the link when I get a long minute to relax.

Super best,
josh
 
I would also add that a good sounding capacitor that is not too expensive is the Mundorf Supreme (not to be confused with its more expensive siblings the Silver Supreme, Gold Supreme, etc.). The regular Supreme has a more full-bodied sound which I prefer to the more expensive versions that all sound too bright and too thin to my ears. Another very good sounding capacitor is the Clarity MR series. I personally do not care for the lower price Clarity caps. Lastly, a pretty good sounding cap that is quite reasonably priced is the Sonicap Gen 1 series. I have used them a number of times and they are used in a few good sounding commercial speakers. It is only available as far as I know for Sonicraft. Here's a link:

Sonicaps
 
Ok, old thread hence late reply. Just killing time in the middle of the night is South Australia, yep the State where Duntech Sovereigns were made!!!! And yes I can claim to have hand built these speakers back in the mid 80's. So just as a point of clarification I can tell you with 100% confidence that the caps are Rifa branded caps and are 250AC rated. What you see is a stripped down version of the cap because part of the manufacturing process was to take all components that went into any of the PCL range and test them for their actual value and hence tolerance. You can see the hand painted markings on the components, they are in fact placed there by us mere mortals to record the tolerance we measured for each component using the standard resister colours codes to represent 1%, 2% etc etc... Then a certain tolerance component had to be used in particular sections of the crossover circuit. You can see that when you study the components on the board. You should find that caps or resistors that appear in the same location on each board will have the same colour markings on them. So your caps were broken out of the PVC casing that they came in, the legs, that we hand wound loops into, were soldered on, heatshrink applied and then they were tested for tolerance and marked accordingly. Yes all very labour intensive but Dunlavy was fanatical about these things. This is why every driver that came in was also tested and paired for each system. That is, 4x 12 inch bass, 4x 6 inch midbass, 4x 2inch dome mids and the 2x tweeters were carefully matched for each pair and yes test results recorded for each driver and drivers marked accordingly. If I sit in a quiet room I think I can still hear the sweeps that were used all the time right near my work space to test these drivers day in and day out :) That yellow sticker on the back of the bass driver I am pretty sure is one of the stickers placed on the driver to identify it to its test results, but I cannot see any number written on it from the image?



Thanks for posting these images as it bought back some great memories for me. I loved these speakers and just wish that more were sold in Australia as I would love to own a pair myself. I have never heard another speaker that moved me the way these speakers did. For their time, and I would like to say even now, they are/were truly amazing speakers. I hope whatever you do to the crossovers only makes them better as I would hate to think you changed them for the worse!



Enjoy your awesome speakers and make sure that they have the room they deserve and they will shine.. I heard them at their best in the specially designed sound room we had at Technology Park at the factory, they were just sublime... every day when there was a demo it was like I was sitting outside of a jazz club, a church, a theatre, the venue basically, it was when I realised that this was Hi Fi... who cared about a sweet spot when this speaker convinced me that if I walked through the doors into that room I would find the performers there before me they changed the way I assessed audio from then on. You are a lucky person to have some.