Mundorf cap in a Druid.

jameshuls · « **on:** 17 Dec 2008, 07:42 pm »

I just wanted to post a tip for anyone interested in modding their Druids. I have a Druid MK IV (pre '08) which had a high pass filter consisting of a 1.0 uF Kimber Cap and a 12.5 Ohm Mills resistor. Having picked up a number of different 1.0 uF caps (Mundorf Silver/Gold in Oil, V-Cap TFTF and OIMP, Jantzen Superior and Silver Z-Caps and Obligatto) for coupling purposes in my various Hagerman projects I am working on, I thought it would be intersting to see how these caps might change the character of the Druid. As the Mundorf is said to be one of the best for speaker applications, I figured I might as well start with that one (not to mention, the Silver/oils are what Zu uses in the Presence and the Definition). A couple buddies, a couple hours and couple beers later, the job was done - the cap was soldered in with Mundorf silver/gold solder (with 8.5 % silver and 0.1 % gold). Upon firing up my melody 2A3 integrated and playing a few reference albums (has anyone heard Bon Iver - For Emma, Forever Ago? If not, check it out!) it was obvious there was a change. The highs were more pronounced, sparkly - off-axis listening improved greatly, and when in the listening chair, there was more life and air to the music. The soudstage also blossomed. However, there was also some stridency that was fatiguing. On went the radio for a week of Burn-in... Upon returning to the listening chair, the situation had improved. All the benefits, without the fatigue. These are definitely staying there, until I can afford some Duelands, that is! Overall, for about $200 and a few hours of work (if you're drinking beer and having fun maybe work is not the right word!), my speakers took a significant jump in performance. I guess Zu doesn't use these in the first place due to their cost - $200 worth of components probably means another $4-500 on the price tag, pushing the speaker into a price range that may impact sales, over what the improvements wrought. The only caveat - if your system is already bright, you may find this change takes things a bit too far, unless of course you change the resistor value to compensate. That brings me to my next mod - replacement of the Mills wirewound with a Dueland resistor - at about $30 for the pair it's hard to go wrong. I'll post again once it is complete!

dspringham · « **Reply #1 on:** 17 Dec 2008, 08:45 pm »

Good observation.

I have a pair of Druid IV (pre '08) and also a pair of Mark IV's with the latest drivers & networks.

Before I bought the last pair of IV/08's I noticed in a print ad that Zu was offering a FREE "Signature Tweeter" upgrade with the purchase of the pre 08 Druids.
The "Signature Tweeter" upgrade comprised a new, mechanically reworked tweeter with a network utilizing the Mundorf Supreme Silver POIL cap with Mills resistor. The assembly also included Zu's proprietary "B3" wiring harness with cold crimped (solderless) connections.

I ordered and installed the Sig Tweeter upgrade and found that the improvement on the high end was similar to what James experienced above. At the factory before being sent out, Zu put in the necessary hours to break-in the tweeter, network components and wiring harness. On my assembly it sounded great right out of the box. This upgrade was directed towards Zu's current goal of increasing the high end resolution throughout their speaker line in order to bring the sound a little more inline with modern audiophile expectations. The upgrade has definately accomplished that goal by temporing the slightly dark or recessed sound of the original Druid.

My Mark IV/08 version has the Kimber Cap network and does not include the B3 cable harness. I haven't made direct side-by-side comparisons but I liked the Signature tweeter upgrade enough to install in my the '08 version Druids and put the Kimber cap version in my pre 08's.

Speaking with Sean at Zu, his suggestion was that the Sig version would probably have more to offer with acoustic and small jazz ensenble type music (which is what I prefer to listen to). He also mentioned that the B3 cable harness on the Sig Tweeter would offer additional sonic benefits. Unfortunately, it was decided that the Signature upgrade would be discontinued due to the cost of the Mundorf caps and B3 wire as well as the overall labour cost to produce the network cable harness.

The one critisism of the original Druid was the slightly rolled-off high end response and lack of ultimate resolution. All in all, I think that the Signature Tweeter upgrade took the Druids to a whole new level making them an unbeatable value. The new 08 Druids with the Kimber Caps accomplish the same thing but, I believe without the same level of refinement of the Signature version.

Compared to my Harbeth Super HL5's, the Signature Druids don't have quite as much high-end sparkle (although the Harbeths with Super tweeter are not know to be super resolving and bright), however the Harbeths don't have the "you are there" presence of the Druids which is very exciting and involving (especially with SET amps). These two speakers (in my system/room) actually sound more alike than different. I've heard the Druids referred to as "high-efficiency" Harbeths. I would agree and this puts the Druids in very good company indeed.

Dave

jameshuls · « **Reply #2 on:** 17 Dec 2008, 09:34 pm »

Dave, Interesting to note you had the same outcome with the Mundorfs - they really do take the speaker to another level, particularly, as you say, with intimate settings where you can really appreciate the improvements the Mundorfs provide. With high female vocals and jazz horns in particular, the music is more than ever of the hair-raising caliber - listening to Miles Davis - Kind of Blue - WOW! The emotional intent is really communicated! I wasn't aware of the signature upgrade, but it sure makes me pleased aa that a little DIY project I decided to undertake was actually something which Zu did to improve the speaker, but ultimately ditched due to economics. I wonder, do you still think the 08 tweeter worth it if I could just get the tweeter, or do you think the addition of the Mundorf cap takes you most of the way in performance? Also, how did the wiring harness differ from what is in there now - was it just a short stetch of B3 cable between the it the full-range and the cap? If that's the case, I would think putting some high quality OCC silver solid core might be another easy mod to squeeze out the extra performance this tweeter is capable of. Finally, do you think the '08 Druid is a significant upgrade over the Mk IV (particularly a modded one). I would welcome any other feedback people might have, or suggestions for other modifications. That being said, a google search turns up NO results for Zu Druid Mods/tweaks etc. Perhaps I am a vanguard in this respect!

45triode · « **Reply #3 on:** 12 Jan 2009, 08:47 pm »

Dear James, dear Dave,

honestly, i was searching for this kind of info for a long time. i own pre ´08 druids as well. After about a year of playing the druids i changed my amplification from a rogue atlas el34 amp to a yamamoto A08-S, a single ended 45 amp with (maybe) 2 watts. This resulted in better HF but it also revealed a metallic, sharp tone of the druids tweeters. everynow and then it really disturbes me, because i have a shindo claret pre that can really sound nice. i also contacted Sean from ZU about half year ago about this, he offered the signature upgrade, but i couldn´t spend another 450$ plus shipping and customs.

So I was hoping for some information about tweaking those nevertheless wonderful speakers. Thank you Dave for starting this thread. I intend to duplicate your capacitor change but have one more question: i learned that the druids are voiced with a 3 db dropoff for the supertweeter. If one wanted to have less of a dropoff, what kind of modification needs to be done?

Excuse my english, i am a technical idiot and from europe.

Best, Oliver

jameshuls · « **Reply #4 on:** 12 Jan 2009, 09:35 pm »

Hi Oliver,

I am not sure how to change the slope of the roll-off of the tweeter using passive components, short of installing a complex multiorder crossover. This would defeat the whole purpose of Zu speaker design.

However, changing the value of the cap and /or resistor in the high pass filter will change where the cross-over frequency occurs, as per the following formula:

f = 1/(2piRC)

Where f is in hertz, R is in ohms, and C is in farads.

For example, the high pass filter in the druid has a 1uF (0.000001F) Cap and a 12.5 ohm resistor.

Therefore, the x-over frequency (f) is calculated to be

= 1/(2)(3.14)(0.000001)(12.5)
= 12,738 Hz

As you can see, even small changes in the values of the capacitor or resistor can produce significant changes in the cross-over frequency.

This might allow you to slightly revoice your speaker by changing the cross-over frequency. For example I will soon be replacing the 12.5 ohm Mills resistors in the high pass filters with Dueland units of 12 ohm resistance, changing the cross-over frequency to 13,270. I am not sure what effect it will have, but it will be a fun and easy experiment nonetheless. Personally, I think I will be able to balance any change with some tuberolling in my 2A3 Melody integrated or in my PhonoStage.

You may also want to experiment with placing the speakers on different materials. For example, granite slabs vs. maple or other wood slabs.

Finally, you may want to experiment with placing some damping materials somewhere on the tweeter. I haven't tried this myself, but apparently one of the improvements made to the new '08 druid tweeter was better damping characteristics

I hope this helps!

floobydust · « **Reply #5 on:** 12 Jan 2009, 09:55 pm »

Did you forget to include the impedance of the tweeter in your calculation? If the Cap and resistor are in series with the tweeter than you also need to need to add the impedance of the tweeter to the calculation. The value of R would be equal to the impedance of the tweeter plus the 12.5 ohm resistor.

Regards, KM

jameshuls · « **Reply #6 on:** 12 Jan 2009, 10:31 pm »

Right! Thanks for pointing that out - I completely forgot. I think the impedance of the druid tweeter must be very low, as Zu quotes a crossover frequency of 12,000 Hz, compared to my calculated (minus the speaker) crossover frequency of 12,738. This would mean that the impedance of the tweeter must be 0.77 ohms as the impedance required to achieve this crossover frequency would be 13.27 ohms. I guess this means my actual crossover frequency will end up being 12,470 Hz upon installation of the Dueland resistor.

floobydust · « **Reply #7 on:** 14 Jan 2009, 10:22 am »

That would be an extremely low impedance tweeter... perhaps they have a padding resistor built into it, or they could have just had a custom unit made with an ultra-low impedance. In any case, do post back when you get the Dueland resistor added.

Regards, KM

45triode · « **Reply #8 on:** 14 Jan 2009, 08:19 pm »

thank you james for your reply.

i have contacted ZU about the impedance value of their pre ´08 tweeter. still waiting for their answer, will post the information if i get it.

cheers, oliver

45triode · « **Reply #9 on:** 22 Jan 2009, 03:54 pm »

hi, i received sean´s comments and post them here:

On the tweeter, The Mundorf silver/oil is a good tweeter. Another to consider is the V-cap, though it takes a bloody long time to burn in. I would recommend keeping the value at 1.0uF. Both caps will give you a bit more treble energy than your traditional Au/poly cap such as the Kimber or Solan. Depending on your version, and by the sounds of it you might have the original network on your pair, with a Zobal and the extra padding on output. Essentially the original network had a 20 Ohm pad on it, the current Mk4 version uses a simple 1.0uF Kimber Kap followed by the Mills 12.5 Ohm. This yields an even output from both drivers when matted to transformer output tube amps, and a slightly warm tone with good solid state like a Pass XA30.5 or the like. If you are using mostly solid state then I would run a 10 Ohm resister in place of the 12.5 Ohm. The impedance of the tweeter in the 10k region is about 20 Ohms.

after a second request he clarified further:

Likely yours have the Mk3 network. A 12 Ohm is going to be just as good as the 12.5 Ohm. We use Mills, a US aerospace company, they make a good resistor, but there are others as good. I love the A08 Yamamoto, killer amp! These values are going to be a good match. The Shindo pre might be a bit soft in treble, with the combo an 11 Ohm is likely going to work best.

I hope this gives further insight to this discussion. also i would like to express my sincere thanks to sean from ZU, always a helpful fellow.

oliver

jameshuls · « **Reply #10 on:** 23 Jan 2009, 03:31 am »

Wow, that is some good info - I'm not sure why I didn't email Sean myself, as he has helped me out on some other questions I have had. Anyways, thanks for the post. I hope to put the Dueland resistors in this weekend so i may have more to post soon.

naggots · « **Reply #11 on:** 4 Apr 2009, 07:09 pm »

After reading this I purchased 2 x 12ohm (actually 12.5 ohm matched) Duelund resistors ($13 ea)and some Duelund 0.5 oil/silk silver foil hookup wire ($7 per ft)and Mundorf silver oil 1.0uf ($45 ea) matched caps from Parts Connexion and am going to upgrade my 08 Druids......Thanks, you cant go wrong for $130.

jameshuls · « **Reply #12 on:** 5 Apr 2009, 05:46 pm »

Naggots, IMO it was money very well spent! I am still not sure the effect the Dueland resistors had. There was a change but I foolishly did it only a week after hooking up a new Hagerman Cornet 2 phono stage I had just completed. The painful break-in of the teflon V-caps i used overshadowed any subtle changes wrought by the Dueland resistors. I any case, the system is sounding better than ever right now, so I think it was a good move.

Enjoy!

James

P.S. Changing the hook-up wire will be my next step. If you have the patience, I would recommend changing one thing at a time, just to see what changes arise, probably starting with the caps first, as they made a more dramatic change for the better.

technobear · « **Reply #13 on:** 23 Apr 2009, 07:16 pm »

<sigh> I only joined this forum today and already you guyz have got me spending money!!!

So's I don't have to do any unnecessary disassembly, where is the cap in the Druid MkIV?

jameshuls · « **Reply #14 on:** 23 Apr 2009, 10:28 pm »

The cap is between the main driver and the tweeter. You will have to remove both to most easily do cap upgrade. I would recommend having at least another set of hands to do the cap change, although 2 other sets is ideal. The resistor change is a little easier to accomplish on your own and only requires the removal of the tweeter. Again, another set of hands really helps though. Good luck! aa

petermich2009 · « **Reply #15 on:** 24 Apr 2009, 05:48 am »

Druid MK IV this item isn't best to used?

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jameshuls · « **Reply #16 on:** 24 Apr 2009, 02:24 pm »

Mine are the Druid Mk IV, and the upgrade was definitely worth it.

naggots · « **Reply #17 on:** 26 Apr 2009, 06:28 am »

Well I couldn't wait so I did the upgrade in 1 hit.

The Duelund resistor and Mundorf sio are 3-4 times larger than the existing so care is needed when stuffing them back into the cabinet. I needed 2 ft of the Duelund 0.5 silver foil with oil silk, 1 ft per side as the resistor and cap together are this long even with shortened leads. Pretty easy job as the only soldering is onto the tweeter.

The sound has changed significantly. The treble is so smooth now, it could be a tad harsh/bright in spots before. Overall the smoothness is fantastic, there may be just a little more treble energy overall but it is so controlled and refined in comparison.

People who talk about Druids being closed on top have not listened to Mk4/08......especially with Mundorf caps.

On a side note, when I had the tweeter out I noticed its markings said APT 50/3......the same as the Presence. The Zu literature says APT30 for the Druids. The Presence also has the Mundorf caps along with the Def 2, Six Moons did a review on the new Presence saying the treble was the best yet from Zu.....however a ribbon may be better!

technobear · « **Reply #18 on:** 28 Apr 2009, 07:52 pm »

I thought that before I order the caps I would just pop a tweeter out to check what's in there. Not so fast! What the **** are these strange bolts with square cut-outs??? I've never seen anything like that before. Is it an American design? Where do I get a driver? What size is it? Help!

Don_S · « **Reply #19 on:** 28 Apr 2009, 08:17 pm »

Chris, Are they screw size or bolt size? In other words would you be looking at a screwdriver or a wrench? If they are screw size my guess is you would find the size you need in a driver/bit kit available at good hardware stores. What I mean is a screwdriver that accepts inserts for numerous bit types and sizes (TORX, Phillips, slotted, square, etc.). The kit comes with a driver and multiple bits. Not all that esoteric. Easy to find and not expensive. I tried to find some good pics to post but did not have any luck finding one that showed enough detail. This one does not have any square ends but I know they exist because I have two kits. One is a Black and Decker.

http://www.widgetsupply.com/page/WS/PROD/screwdriver/SAB3-56173