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In Reply to: Re: Zobel's attenuation on driver posted by BKing on May 03, 1999 at 11:38:08:
Not so certain about several of your points. Speakers that use ferro fluid could also have their impedance curve "flattened out" also with the use of a Zobel. Also it will make any Lpad affect the output in a more linear way across the frequency range of the tweeter.Finally the response can be attenuated by the addition of a Zobel but not the same way a Lpad or resistor will. I would site the example in the fifth edition of the LDC as an example of zobel attenuating the upper portion of a SEAs (I think) tweeter. It is in the passive crossover chapter. I can get the page numbers if needed. I also found this to be true at least with the Focal Ti90TiO2 tweeter, but as you mentioned it is not fluid damped.
Edp- I mentioned ferro fluid tweeters because they won't benefit much from use of a Zobel. As for attenuation, I interpreted the original question to mean attenuation as in an "L" pad. I have the 4th edition of the LDC and I know of the section you are referring to and the tweeter in question is a Peerless 105DT.
In my experience, a tweeter with ferrofluid tends to make a conjugate superfluous, not the Zobel, which most will still need.Jon Risch
With most ferrofluid drivers, the resonance of the tweeter is all but completely damped by the ferrofluid. In fact, if you try to go by the Z curve with ferrofluid in the unit, and try to compensate the tiny remaining bump you see, often, the overall Z curve will get worse, as the actual resonance is not the little remaining bump you see!Jon Risch
To me, a conjugate is a specific network, designed and tuned to neutralize the fundamental resonance of a loudspeaker; it is a series network placed in aprallel with the driver. A notch filter is used to reduce an amplitude bump, and in order to prevent an imedance dip in the region of a nominal Z, it usually has to be a parallel circuit in series with the driver.Jon Risch
1) CONJUGATE
0---+-----driver----+---0
| |
+---L---R---C---+
2) NOTCH FILTER
+---L---+
| |
0---+---R---+-----driver----0
| |
+---C---+
I usually refer to them both as notch filters. I just stipulate that #1 is for a voltage-source & #2 is for a current-source. But then again, I can't keep the parallel & series XO straight either. I think it's:
1) PARALLEL
+---C---tweeter---+
| |
0---+ +---0
| |
+---L---woofer----+
2) SERIES
0--+--tweeter--+--woofer--+--0
| | |
+-----L-----+-----C----+
I just stipulate that once again #1 is for a voltage-source & #2 is for a current-source.
Do not comparmentalize the various topologies into voltage source and current source use, as in BOTH of these cases, it is incorrect and misleading. Undoubtedly, it would lead to confucsion when trying to analyze or think through the operation and action of a particualr topology or network in use.You do have the crossover names correct, and the proper diagrams associated with my prior post.
Jon Risch
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