Fullrangedriver Forum

Hi Freddy
I don't have the capability to measure the Zu driver. It isn't something that a DIY'er could replicate easily anyway. They apparently have at least two iterations of the 10 inch driver from its initial introduction over a decade ago. It is fairly obvious to me that Eminence provides the majority of the components used in the fullranger and the tweeter.
The tweeter is fed by a 1 mfd Kimber Kap resistor through a 12.5 ohm mills resistor. The tweeter appears to be an APT-50/3 that is  not stock. I don't know what mods have been done to it. I had dreamed about cloning the druid but now I just don't have the time so purchasing a good used pair was my ticket to  experience these unique speakers. So far I am extremely pleased with their performance. I have been able to listen literally for more than 6 hours without any headache or listener fatigue. My 12lt's are good for only about 2 hours and then I am tired of listening to them. I can't explain why this is the case but it really is the truth. I hope that this will continue to be the case. I still get the sensation that they continue to improve the more I run them.
Best wishes
Ron Brady

Hi Norm
I think that you will end up with a winner using the b102 for your next project. I am now able to A-B between my beta 12lt's and the Druids and it has caused me rethink the alignment of the 12lt's. The most noticeable difference between the two is that the 12lt's play louder at the same amp settings. Probably just the difference in impedence (8 ohms vs. 12 ohms). The 12lt's produce more deep bass in their 5 cu. ft. boxes so that is noticeable as well. But where the druids really excell is in their speed. They have a much more powerful motor than the 12lt's and a little more excursion and they use every bit of it to great effect. The druid enclosure design allows for bass tuning to fit your room and it is very effective. The b102 uses the same basket and motor assembly as best as I can tell but the voice coil is 12 ohms so it is a little different and I think that the paper cone and whizzer are a little different. I'll bet that the b102 will be very similar in its sound and presentation. The main driver in the druids by themselves are not that impressive but combined with the eminence apt 50/80 compression driver tweeter the combo is very dynamic and very airy and life-like it their presentation. ZU has developed a system which gets the initial attack just soooo right that you are intrigued to listen further and deeper to the presentation. I have now removed the parallel notch filter from the 12lt's and the BSC and the polite 1" silk dome tweeters and I am running them directly to the amp. I have orderd a pair of APT 80 tweeters and some misc. caps and resistors to help integrate them with the 12lt's. I will let you know how that goes as time allows.
Best of luck with your new project-----I think that you will probably like the speed and slam of the b102's!!!
Maybe freddy can give you more on his impressions of the b102.
Ron Brady

Hi Norm
I can certainly understand your reluctance to jump at the b102 drivers even though I am convinced that they aren't very much different than the ZU custom driver. The ZU driver on its own is quite boring and unimpressive except for its speed but it doesn't sparkle as well as the 12lt without a tweeter. The real star for ZU is the APT 50 compression driver and the way it is integrated with the main driver. The two of them together produce and very entertaining and easy to listen to system. It sounds very natural and free and unrestrained and I can listen for hours at fairly high volumes and not feel burned out. I am waiting for a pair of APT 80 tweeters with 80 degree horns to arrive so I can work on integrating them with the 12lt's in hopes of capturing some of the ZU magic in speakers of my own design and construction. I was always satisfied with the 1" silk dome tweeters that were in my system before but after listening to the dynamics of the ZU's APT 50 tweeters it is obvious to me that the silk domes were just too polite and wimpy for a larger room like I have now. I will post my progress with the 12lt-Apt 80 integration as I progress through the process. So far my friends also agree that the Druids are about as good as any of them have ever heard and are always wanting to come over and listen for a while---it is a lot of fun to hear their comments even though most of them are not really into audio stuff.
Best wishes
Ron Brady

I've got a fever so don't know where I'm at.   Zu's claim of 12 ohms is suspect as that is what they said for the old model tested by Soundstage in 2002 showing considerable area around 8ohm.  Despite the old B102's qts, I thought it was mellow - of course a tweeter brings it to life.  The new model sometimes shows a smaller magnet and higher qts.  Newer Beta 10cx have the same surround as the new B102 (and a Delta 10) and I could have fun with Beta 10cx in  K-coupler as mine sounds decent for the money.  One reality check on the Druid woofer might be to measure its dcr.  I like Druid's form factor and assume my guess of a floor coupled straight pipe to be correct (?)  12LTA has ~0.80" overhang so is sensitive but can't bang like the 95oz magnet 12" in K12 - its still a good driver - wonder if there's a good cone dope for it which would actually improve its tone overall?

Last edited by karlsonkab (2010-08-20 22:11:04)

how do we know the new Zu version isn't 45oz?

Hi Norm and Freddy
I took a DCR measurement of the Zu with nothing connected to it and it measured at 7.6 Ohms. I think that the spl curve from eminence had it reaching 12 Ohms somewhere above 2kHz. I didn't measure the APT 50 but I'll bet it is probably about the same except maybe up at 12kHz. They use a 1.0mfd Kimber cap in series with a Mills 12.5 Ohm resistor between the positive positions of both drivers so with an 7.5 Ohm tweeter the circuit would total about 20 Ohms. No zobel is used. I don't know what size the magnet is on the 10"er but it does look like the one in the pictures of the b102. I don't know how they can claim a 12 Ohms unless somehow magically the impedance is averaged when operating with both circuits in parallel. The single capacitor used to couple the tweeter means that it is coupling at a rate of only 6db per octave. Which means that if the tweeter is conducting at 100% by 12kHz then it is only down 6db at 6kHz and only down by 12db at 3kHz which when added to the 2-3db rise you mentioned below 10 kHz then clearly the tweeter is producing over a substantial frequency range. This explains why the 10"er is rather dull when the tweeter is covered up. I suspect that the rating of 101db efficiency at what I assume was measured at 1kHz may not be correct. I think that the first version of the druid used a large inductor to roll off the 10"er at some point and that may explain the 12 Ohm number. But on my version the inductor is not used. I also measured the DCR of my 12lt's and they are both at 7.7 Ohms. I'll bet that they probably share the same voice coil. The newer 12lt specs claim that the xmax is 3.3mm where mine were rated at .8mm. The B102 is rated at 3.3mm also IIRC. So I would bet they use the same pole piece. Only the magnets are different. The diameter of the magnets look to be about the same but the one on the ZU is 50% thicker and seems to have a rubber boot on it. When I look at the spl curve for the b102 it makes sense when I listen to the ZU with its tweeter covered up. What I hear pretty much matches what the b102 curve shows. My preliminary conclusion is that the two drivers are probably close to being twins. I had some friends over last night to listen for a few hours and we did that test and everyone agreed that the 10"er by itself is great at producing tight fast bass but is weak through the upper mids and the treble is very much missing. With the tweeter they all loved the druids. They will play very loud without any distortion until a big sub woofer note comes along and then they demonstrate their only shortcoming. I have read others complain about the bass performance but I must disagree. I find them able to produce very satisfying and fast articulate bass with nice attack.  The 12lt's are not as good in the attack department but in their 5 cubic foot boxes they will go a half octave lower.
I have read the various articles regarding the tweeter cap upgrade and someday I may try that but at $100 bucks for two boutique capacitors it will be a long while away---especially since my 57 year old ears would probably not be able to tell the difference but $100 bucks can buy a lot of pizza and beer and a few more listening sessions with my friends (some of which are young enough to hear the difference).
Well I guess that is it for now. Let me know if you have any more thoughts about the druids and b102's.
Norm
The APT 80 on the parts express site has a different curve than the apt 50. I suspect that the apt 50 without a horn to load it may have an odd spl curve. The horn used by Zu is 80 degrees and so is the APT 80. These tweeters should arrive next week sometime and I will be working to mate them to the 12lt's. Should be a lot of fun.

Best wishes
Ron Brady

Last edited by ronbrady (2010-08-22 23:44:36)

Hi Norman
I think that I have heard the apt 50 on the zu hit resonance a few times so the 40-50 ohm resistor across the poles of the apt 50 sounds like a good idea. I almost hate to do it but from what I have read the druid sounds better with the mundorf. I wonder if it would make any difference since I am using jantzen superiors to couple into and out of my home made preamp. Even though they are each bypassed with a small teflon cap I have often wished that I had spent the money and improved their quality but up until now I have not had a supertweeter that could show those weaknesses. I personally cant hear any problems with the kimber caps so I will leave them in for a while longer.
Introducing the apt 80 to the 12lt should be fun. I still have a zobel filter accross the terminals of the 12lt which should help with impedance matching the tweeter. I will simply set the apt 80 on top of the cabinet where it will be easy to substitute components in and out. I will also try removing the zobel circuit to see if the 12lt sounds any different running free, unleashed and wild. It has such a steep impedance curve and looks exactly the same as the b102. I am still convinced that they share the same voicecoil. Clearly the 12lt and the b102 dont have a shorting ring  or shorted winding other wise the impedance would not rise to over 70 ohms at by 10kHz.
As far as the 12lt mods go, I have removed the dust caps years ago and installed my silk dome tweeters on 2 inch diameter Pvc pipe to the pole piece to time align them. They also serve as the phase plug so the highest frequency peak on the 12lt spl graph has been eliminated. It was caused by an echo from the pole piece back to the dust cap. Removing the dust cap really cut the upper treble a lot but it made voices sound richer. In a small room the silk domes worked fine but in my larger room they are just lost in the background. My seatin position is about 10 or 11 feet from the spakers so the domes wide dispersion pattern caused them to sound weak at that further distance. I am hoping that the apt 80's can help them to perform more like the zu's. I will consider cutting the whizzer down only as a last resort but I have been thinking about it for some time now since the zu 10 incher seems much less peaky with a much smaller whizzer.
Best wishes
Ron Brady

cap upgrade almost always help, just not big improvements for the price, but improvements nevertheless.  $10 cap to a $50 cap in a 6db series crossover should make a big difference.  Look into 47uf bypass caps for your power supply rails and .1uf added to coupling caps and feedback caps in amplifier.

My buddy at work didn't care for the sound of zobels, as was an article on a zobel added to a fostex full range online.
But I also read a zobel helped a 108 sigma, so who knows.

Since we seem to now know that the tweet setup is the mvp (having so much to do with its sound), definitely try the 50ohm, otherwise the inductance of the tweet (especially at resonance) changes polarity then discharges back into the cap.  They ring back and forth till energy is dissapated.

Yea, trimming a whizzer, you have to get to hate a driver to do that.

And yes, it would be neat if we could get either 12lta or b102 with a bit more magnet and the included graphs.

The apt 50 now made is worse than the original.  They were made in Poland until 2 years ago, but Eminence stopped making them there, like that.  The current ones are junk.  The cheaper clones are even worse (like the cheap piezos now also).  I'm thinking definitely the b102 plus something, but I still have some work to do on a tweeter that can roll in at 6db and get the spl right near 93db.  Ideally it would be ultra small to get closer to the b102.  I'm thinking a selinium driver plus horn may work and be rugged enough not to melt.

Norman

Last edited by norman bates (2010-08-23 19:09:37)

I always thought these looked good. See the glowing reviews !

http://www.parts-express.com/pe/showdet … viewShow=1

http://www.parts-express.com/pdf/294-605.pdf


Never heard them, but they sure measure pretty nice.



............................Blake

I know how to do piezos (transformer coupling is a pain), but to get it to roll 6db into a full range driver, that's tough.  I loved my motorola 1038a using active crossover 24db LR at 5khz (500hz above resonance) with a 62ohm resistor in series with it.  Soon as you moved the crossover point down, it became spitty and splashy (giving piezos a bad name).  Problem is a med/large piezo has a resonance 4-8khz that is hard to swamp or trap out.  But the smaller motorola 1016a and 1038a ring at 4.5khz, just cross above that 24db and they are competitive with the best ribbons.

Interesting that the 12lt is lacking in dynamics, specially when a bit louder than 102b but weaker qts and lighter cone for the area.  I think the really strong apt50 driver even padded down is what is helping the dynamics in the zu, especially down to 5khz.

The b&c ain't too cheap, and I don't see a plane wave tube response either (bumps = resonances), I'd hate to have only 15 degrees of dispersion past 10khz due to a horn by pinching it so much that it picked up 15db past 10khz.  I mean you could roll a jbl 2407 on the round mcm 6" horn even.

I havn't given up on the druid clone, just need a rugged tweeter 93db 1w/1m that can take a 6db pole at 5khz............
Maybe a ribbon or a big 1" morel dome tweeter might do it, then again, keeping up with a pa 10" sitting 10' away.......
Compression drivers are also an option, like a 6db pole at 20khz that rolls in perfectly.

Norman

Last edited by norman bates (2010-08-24 06:51:36)

Hi all
Here is a link to a seller of Piezo tweeters who has a list with a few specs. There a quite a number of them to choose from.
http://www.mark1electronics.com/piezo_tweeters.htm
The apt 50 is used with the eminence coaxial reinforcement drivers such as the beta 12cx and 15cx. Eminence even makes a crossover with L-pad for that combination. For some reason most of the suppliers of apt 50's and 80's are are currently "our of stock". I ordered mine from US Speaker and  they sent me a message asking me if I would be willing to wait a month or so for their "back order" to be filled. Parts express, Madisound and  many others are also claiming "Out of Stock". So I cancelled my order. Maybe I can find something better. But I will guarantee you that I won't spend more than $100/pair for compression drivers for this project. Buying the Zu's pretty much ate up my DIY audio budget for a couple of years!! I will look again at the FT17H tweeters a little more seriously. Actually Fostex offers several interesting compression drivers---I don't know the prices though!!!
Oh well----back to work!!
Ron Brady

I don't think the fostex ft17h would work, it has an fs of 5,000, right where a 6db pole would be perfect for rolling into a wide open b102 driver (5-6khz anyway).

A morel cat378 (semi horn loaded dome) might roll in nicely, or be a db too low ($61).
https://www.madisound.com/store/product … ts_id=8475

Norman