Tweeter Zobel, or more accurately, RC network.

LNeilB2

Member
2001-10-23 6:41 pm
VT
This is not often discussed, but I've been told that adding an R-C network to some tweeters helpd to refine their sound. I came across this on the LDSG:
"The MDT33 tweeter has a very devoted following. Some have also recommended the use of a Zobel to sweeten the top end."

Your thoughts/experiences?

TIA

Neil
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
LNeilB2 said:
This is not often discussed, but I've been told that adding an R-C network to some tweeters helpd to refine their sound. I came across this on the LDSG:
"The MDT33 tweeter has a very devoted following. Some have also recommended the use of a Zobel to sweeten the top end."

Your thoughts/experiences?

TIA

Neil


How is the RC added? Totally different designs may have different purposes.
 
I have used Zobels on tweeters before, usually around 2uF or lower, using them did seem to make a cheap tweeter better, but Rod Elliot or perhaps LDC said it make the load on the amplifier better, remembering that this load should be at least flat to 2 octaves above highest reproduced, so if tweeter goes to 25k then the load should be as flat as possible to 100k.

This is where you need to experiment, a small cap and 5W resistor won't set you back more than a dollar, and I always set my Zobels on the back of the driver anyway so very easy to do with-out pulling the XO out
 
This is not often discussed, but I've been told that adding an R-C network to some tweeters helpd to refine their sound. I came across this on the LDSG:
"The MDT33 tweeter has a very devoted following. Some have also recommended the use of a Zobel to sweeten the top end."

Your thoughts/experiences?

Neil

A Zobel or conjugate circuit is usually used to flatten out the impedance, specifically the inductance rise. I don't know how it would "sweeten the top end" of a tweeter. They are more typically used on woofers where the flatter impedance may help make crossover design easier. In the case of a tweeter it has less impact on the crossover because it is on the top side of the band rather than near the crossover point.

In either case it can't sweeten the top end unless it changes the response of the crossover network. The amplifier doesn't care either. Most amps are happy to drive a gently rising inductance.

David S.
 
This is not often discussed, but I've been told that adding an R-C network to some tweeters helpd to refine their sound. I came across this on the LDSG:
"The MDT33 tweeter has a very devoted following. Some have also recommended the use of a Zobel to sweeten the top end."

Your thoughts/experiences?

TIA

Neil

Can you please post exact link to this article.
 
I tried to calculate the RLC Serial Resonant Circuit. It looks work.

But in the low-freq area , it needs big value of caps and coils and will cost very high.

yes to my knowledge RLC is the way out. it makes crossover see same impedance all over the frequency range. So the crossover behave as expected (remember while designing crossover we calculate values based on driver impedance.). Probably this is the reason why tweeters too sound better with this RLC. Still I haven't come across any tweeter using RC. cause this would hamper the high frequencies at tweeter. you will many people has shared experience about connecting RC (zoeble) to woofer.
 
yes to my knowledge RLC is the way out. it makes crossover see same impedance all over the frequency range. So the crossover behave as expected (remember while designing crossover we calculate values based on driver impedance.). Probably this is the reason why tweeters too sound better with this RLC. Still I haven't come across any tweeter using RC. cause this would hamper the high frequencies at tweeter. you will many people has shared experience about connecting RC (zoeble) to woofer.


Thanks. Some tweeter also exhibit a rising impedance with increasing frequency so I confused that add the RC-Zobel for the tweeter.
 
I tried to calculate the RLC Serial Resonant Circuit. It looks work.

But in the low-freq area , it needs big value of caps and coils and will cost very high.

Why are you adding Zobel or conjugate circuits? If you think you should add them automatically to make something "sound better" this is the wrong approach.

Try to design the network without them. If you have a problem getting the voltage curve at the driver terminals that you need, then add the type you need, but not as a matter of course.

I've been designing networks for 30+ years and I think I've added conjugates to 3 networks.

David s.
 
Not Some, but all do. Finally even tweeter coil has inductance. ... so technically it has to have RLC to compensate it. I would be eager to see the examples where just RC is used.


RLC will deal with the resonace peak of the impedence and RC will deal with the rising impedance with increasing frequency(because of the coil inductance).

Above is what I knew from some text.
 
It all depends on the values, of course, but added after an existing crossover it will act as a shelving filter and roll off the treble (but there will be some interaction with the crossover as well, so the result is really undefined). Unlike a simple tweeter level control which hinges at the crossover point (and also moves the crossover frequency) adding an additional filter lets you pick where the rolloff begins. Again, that depends on the values chosen, as does the interaction with the existing crossover. Whether added HF rolloff will "refine the top end" or "sweetens the sound" is, of course, a matter of taste.

Included as part of an original crossover design it will do the same, but more predictably (it's part of the design, after all). Just model the crossover (in something like Passive Crossover Designer or Sound Easy) to see the effect.

In an active system (no crossover between the amp and the tweeter) even large values will have no effect except to load the amp (there already may be a small-value RC network in the amp to insure stability with varying loads, but those values will not effect frequency response in the audio range).

It is unlikely that you would hurt anything trying it, but it is also unlikely (without modeling) that you would get the result you desire, or expect.