Here's a head scratcher. I had some Merlin-supplied Zobel R/C Networks for their TSMs and never liked them. The TSMs went in for an upgrade, so I tried the Zobels on a lovely little pair of Celestion 100s I keep for backup. Voila, the effect on these was fabulous. Highs very much smoother. Whodathunkit? I guess the word is try it. |
Hi Sean,
Stan Warren said 3 Watts for the woofers, and 1-2 for the tweeters....
Lou |
Out of curiosity, what wattage rating were used on the resistors for the various units ? Did you "zobel" all of the drivers, just the mids or woofers, etc ??? Sean
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I tried the zobels and in my opinion they worked very well.
first of all clarity and detail are extremely noticeable. before the zobel there was a slight smearing in the treble and the midrange that is virtualy gone now. also i was suprised how much better the bass got very tight and musical. We did one speaker at a time so we could AB there was no doubt the zobeled one was better. One thing to keep in mind if you want to try this. The parts cost very little about $30.00 and if they don't work for you you can just remove them. Once again thank's for all your input! |
I completely agree with the above post now that we understand where each other is coming from. For what some of these products cost, there should be NO cost cutting or "oversights" at all. Then again, MOST of the profit on these items is NOT made by the manufacturer but by the dealer. If things were slightly reversed, we would see better products and dealers that were more motivated to work with you. Sean
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Sean, I appreciate your backing me up on Zobels. In terms of my description of John Dunlavy, I want to state that I DO think he is an electrical genius! I just don't think he (or anybody for that matter) is an ABSOLUTE electrical genius. Is there anybody on this planet that knows everything?
It has been my experience that many highly respected designers of ultra high end loudspeakers, amplification and digital can miss something in their overall design execution, which although may be just minor oversights, are oversights none the less.
When we are talking about very expensive products such as $25k+ speakers, $10k+ amplifiers , or $5k+ digital that can be easily improved with inexpensive modifications, I feel that my "dropping the ball" description is very appropriate. A product at these price points should not be easy to improve with minor, inexpensive modifications. |
Ehider, your comments about Stan understanding how various gain stages of an amp are affected and Dunlavy ( along with other speaker designers ) "dropping the ball" cracked me up to say the least. Anyone that knows about Dunlavy's background and past products knows that he IS an electrical "genius".
As a case in point, John was building / designing super high speed / ultra wide bandwidth circuitry LONG before most of the other audio "EE's" ever thought about doing such. I would consider David Spiegel to be at the forefront of that movement in the early 70's and Dunlavy just a bit behind him. He is well versed in both AF ( audio frequency ) and RF based circuitry, understands transmission line theory, has built, designed and patented one of the most widely used antenna designs known to man, etc...
This is NOT to say that Stan does not have his moments of brilliance and is able to "work magic" by simply taking a good thing and making it better. I have owned some of his past products and am familiar with his work. This is also NOT to say that John does not cut corners on some of his production models or gets everything "right" or "as good as possible" to begin with. This also is NOT to say that i agree with all of Dunlavy's points of view, even if i do acknowledge his vast level of experience and education. There are reasons why both men are well respected in their fields.
There is one thing that i do agree with in your post though. Individual Zobel networks for each driver is a FAR superior design than trying to use a Zobel for the whole system. I have never seen anybody try to do an "all in one" network though, although i'm sure that someone has attempted it. Sean
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I also think that Jud needs to open his mind. I really like Dunlavy speakers but why should we assume that Dunlavy (or any other respected designer for that matter) is an absolute electrical genius? Other than not using Zobels, he also implements cheap (yet competent for the price) midrange and tweeter drivers, which can be easily improved with the substitution of better drivers (for instance: change that cheapo Vifa tweeter for a Morell MDT 33).
What John (and other competent designers) brings to market are extremely competent designs that compare to others at, or above their price points. For anyone to assume that a designer has not dropped the ball somewhere on a detail or two, is very shortsighted and a bit naïve.
Something to note about Zobels: a single Zobel network used within a crossover IS NOT THE SAME as multiple individualize Zobels networks that are wired in parallel across each of the speakers driver terminals. The latter is the one that Stan Warren is recommending, not the former.
Stan is an expert of how different amplifier gain stages react to different loads, and how they will sound accordingly. This is where Dunlavy (and many other speaker designers drop the ball). If a Zobel is implemented correctly, it will be a WIN/WIN scenario with no downfalls. Each driver's voice coil has an inherent reactive inductance that if tamed, will allow the amplifier to do a better job operating that driver. With properly measured and implemented Zobel networks in place, the drivers inherent phase vectors
are drastically reduced, allowing the amplifiers' gain stage to better react to the changing
dynamic demands that would be worse if the individualized driver/zobel networks were not in place. Again this is not the same as implementing a crossover Zobel network, which is no where near as effective as individualized driver Zobel networks.
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So Fleeceba, did they sound better? What was your actually experience trying them (you said previously you were going to).
Here are some links to Zobel info:
http://www.trueaudio.com/st_zobel.htm
http://www.selectproducts.com/calculator_zobel.html |
So Jud, are you saying even if the speaker ends up sounding better it may not be better? or are you saying i should'nt mess with John's design? |
A zobel for a particular speaker is a basic part of the design of the crossover - the single most difficult part of loud speaker design! Dunlevy has forgotton more about crossover design than most designers will ever know, let alone the rest of us.
Leave your speakers alone. Home rolling of speakers is grand folley, and you can certainly change the sound but will you ever know if is actually better.
Best regards, Jud Barber - Joule Electra |
Due to mass confusion (!!!), Stan Warren's number was deleted. In case someone wants to contact him, he can typically be reached at (541) 344-3696 in the evenings. Sean
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Lou thank you and everyone for your input i've talked with Stan Warren and he'll be coming over to my house tonight.
we'll zobel one speaker and see how it sounds. |
Hi Fleeceba,
Stan Warren recommend doing exactly what you are doing, and knows the correct values, though you may have to get the inductance measurements for each of your drivers for best results. He says it reduces smearing, a phase related distortion that exists because the driver's inductance has not been compensated for, or words to that effect. It is supposed to make a very big difference, which is said to be even more noticeable if you are used to electrostatic or ribbon speakers.
Hope this helps,
Lou |
I have no idea as to where you can find a good yet simple explanation of how or what a zobel does. In layman's terms, it is simply an impedance compensation device typically comprised of a resistor and capacitor wired together in series. This in turn is wired across the load ( or part of the load ) in parallel. Changing the parts values ( amount of resistance, capacitor values, etc..) changes the "tuning" of the circuitry.
These "circuits" can be used to help stabilize circuitry from oscillation, maintain relatively constant impedances, etc... Since it is connected at the output of a device, it too becomes part of the load and dissipates some of the signal. As such, resistors and capacitors used in these circuits need to be able to dissipate both sizable amounts of power and heat when used at speaker level. This is the type of "impedance stabilization" that Goertz supplies with their speaker cables ( if needed ).
In terms of zobels used for speakers, what one is trying to accomplish is an even impedance across the audio spectrum. Even though a driver may not be operating at anywhere near full output ( like a woofer at 8 Khz ) due to a signal dividing / crossover network, it is still part of the electrical load that the amp sees and the acoustical output that you hear. The use of a zobel helps to keep reactance down to a minimum and reduce the driver output level that is trying to operate "out of band".
As to Fleeceba's idea of mounting them directly at the driver, i see no problem with such. Most designs incorporate them into the crossover board for ease of wiring / configuration during mass production. Since you're dealing with something that is already a "finished product" and don't want to muck with the factory product, your approach seems the best and easiest to take. Sean
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Where is there more information on zobel? Is there a website by chance? I had not heard of these before. |
actually sean i'm talking about putting the network on the drivers them selfs. |
Zobel networks can be used in several different ways. I assume that you are talking about installing them in the speakers themselves in each section ( woofer, mid, tweeter, etc...) of the crossover network ?
I have heard through the grapevine that Dunlavy's sound noticeably better with the use of such devices. I have no first hand experience in this specific area, but know others that are interested in Dunlavy's and checked into it. Supposedly, Stan Warren is a proponent of installing Zobel's in Dunlavy's. Quite honestly, i would have thought that Dunlavy would have been using Zobel's in his design to begin with.
From personal use, i know that Zobel's increase power consumption of the speaker for a given SPL. They can also give you a notably more linear frequency response. More than a few folks have complained about a "flatter" presentation i.e. "loss of dynamics" after Zobel's have been installed though, so this is something that may not be for everyone. Most speakers that make use of Zobel's are known for being "power suckers", so the loss of dynamics may be due to requiring more "horsepower" to attain the same peak output. Sean
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