[brj]

As I browse the internet for audio topics, I'd recently been reading about Zobel networks.

Is anyone aware of any downside to using a Zobel network to flatten out the effective impedance seen by the amp?

Despite my ongoing search, I have yet to find a drawback (aside from the cost of the components, which is usually not excessive).  About the worst I've found so far is that Zobels are not always needed for a given amp/speaker cable/speaker combination.  I'm not used to finding things in audio without drawbacks, so I was curious as to whether I'd missed something!

Thanks!

[Pete Schumacher]

Other than not being necessary with most solid state amps, there's no drawback.

For amps with higher output impedances, the zobel network can help maintain a flat output response if the speaker impedance is climbing with frequency.  But if a speaker load has a large peak in its impedance in the middle of the band, a zobel alone will be ineffective at flattening that bump.  In those cases, you need to add an inductor as well, choosing values that form a complex conjugate of the impedance bump.

[brj]

Thanks, Pete.

Yes, I understand the behavior and purpose of Zobel.  I was just curious about downsides, as I couldn't seem to find any, which struck me as unusual.

(This was a question borne out of pure curiosity.  I don't need a Zobel at all at the moment, as I'm putting together an active system powered by very stable SS amps.)

[FullRangeMan]

Is anyone aware of any downside to using a Zobel network to flatten out the effective impedance seen by the amp?

When one insert a inductor, resistence, capacitor or any eletric part between the amp and the speaker driver the musical harmonics gone, they are transformed in heat.
The musical harmonics time integrity are the called fullrange effect.
The less bad is the inductor, the worst is the capacitor.

[Vapor Audio]

When one insert a inductor, resistence, capacitor or any eletric part between the amp and the speaker driver the musical harmonics gone, they are transformed in heat.
The musical harmonics time integrity are the called fullrange effect.
The less bad is the inductor, the worst is the capacitor.

Sorry, can't think of anything to say other than 

[Davey]

A Zobel is a shunting network and not a crossover filter.  I've seen a number of full-range systems that employ impedance leveling devices.

That shouldn't violate the "fullrange" mandate/requirement, should it? 

Dave.

[FullRangeMan]

Seems it use a capacitor or resistence.

[Pete Schumacher]

I've never heard a fullrange speaker that can compete with a well designed two-way for realism, smoothness of response, and distortion. 

It's just physics . . .

[Tyson]

Seems it use a capacitor or resistence.

They are indeed evil.  Hence, we shouldn't stop at eliminating them just from speakers, but should eliminate them from amps, DACs, and preamps as well.

[Rclark]

I've never heard a fullrange speaker that can compete with a well designed two-way for realism, smoothness of response, and distortion. 

It's just physics . . .

See that makes sense to me.. and I've heard a single driver speaker but it was woefully low end, and never heard a high end single driver setup. Since 2 ways are technically better (or 3 ways, and what have you), why do certain people swear by single "fullrange" driver setups? Is it a hearing thing? I read that a lot, that older people like fullrange speakers. If it's a hearing loss thing, then fine, they're not hearing the top end of a 2 way anyhow. Ok, fine again, but why do these same people then swear by the midrange, or whatever attributes fullrange afficianado's seem to prefer, when a 2 way system should still be technically superior in the range they can still hear in?

I don't get it. I find fullrange speakers consistently downplayed by a majority of people I've come across, but loved by a very few. What are they hearing as superior that technically, they shouldn't be?

[srb]

I don't get it. I find fullrange speakers consistently downplayed by a majority of people I've come across, but loved by a very few. What are they hearing as superior that technically, they shouldn't be?

They're hearing, or rather not hearing, distortions and phase anomalies caused by the crossover network in the important and more noticeable mid frequency range.  A majority of two-way speakers have a crossover right in the critical midrange area of ~ 2500 Hz to 3500 Hz.  Some rarer two-ways with a very low crossover frequency of ~1000 Hz or 1200 Hz are less affected, as are three-ways with midrange to tweeter crossing over at ~ 5000 Hz and above.

Some speakers run a fullrange driver and add a tweeter for the very high end above 10 KHz like some Zu and Tekton models, still preserving the "midrange magic".

That being said, I have not found the magic in the single driver fullrange speakers I have heard mostly due to the missing high frequencies, but I have only owned or heard relatively low cost ones with CSS and Fostex drivers, and have never heard any of the fullrange speakers that had the more costly Lowther or very expensive Feastrex drivers.

Steve

[Freo-1]

I've never heard a fullrange speaker that can compete with a well designed two-way for realism, smoothness of response, and distortion. 

It's just physics . . .

 
 I remember reading about Paul Klipsch performing a demo with K-horns comparing live music to his speaker, and the audience could not readily tell which was which. 

[brj]

The question was not intended as a platform to debate single driver speakers vs multi-driver speakers.  Nor was it intended to argue whether a Zobel was needed in a given design or not.  It was intended to determine what penalties a Zobel might impose if the designer felt that it's impedance flattening benefits were justified to begin with, for a given combination of speaker, cable and amp.

Any further insights would be appreciated.  Thanks.

[Quiet Earth]

I don't need a Zobel at all at the moment, as I'm putting together an active system powered by very stable SS amps.

Hmmm.... are you sure that going active means you can automatically eliminate the zobel?

Going active means the crossover is before the amp, and the amp will not intentionally produce any out of band signals to the driver. But the impedance conditions still exist between the output of the amplifier and the raw, untreated driver. I think that a zobel is still required to keep the peace between the two devices, because even though the input of the amplifier is under control, the output is not. There will always be harmonics and other intermod products on the output of the amp where the zobel may come in handy. Plus, how perfect is the entire active chain to begin with?

Not saying you have to have a zobel, just saying there is probably no free lunch.

[Quiet Earth]

if the designer felt that it's impedance flattening benefits were justified to begin with, for a given combination of speaker, cable and amp

Isn't that all that matters? If it helps more than it hurts, then it's a good choice.

[FullRangeMan]

I've never heard a fullrange speaker that can compete with a well designed two-way for realism, smoothness of response, and distortion. 

It's just physics . . .

I glad you dont mention three way. Personal taste apart, any audio equip will sound better with the few parts possible.
Iam thinking in stick with headphones due the huge detailed sound and yet a hi SPL capability.

[Davey]

The question was not intended as a platform to debate single driver speakers vs multi-driver speakers.  Nor was it intended to argue whether a Zobel was needed in a given design or not.  It was intended to determine what penalties a Zobel might impose if the designer felt that it's impedance flattening benefits were justified to begin with, for a given combination of speaker, cable and amp.

Any further insights would be appreciated.  Thanks.

I don't really see any penalties....and they have a number of up-sides. 

Pete's comments in post #2 are 100% correct.

For active systems they would most likely not be needed, but with inductive drivers the load on the amplifier effectively disconnects at high frequencies.  Adding a Zobel to level the inductive load is a good thing.

Also, there may be some benefits to adding a high-frequency Zobel to the far end of the speaker wire to terminate it for high frequencies and prevent possible antenna action from invading the output of an amplifier.

All of this depends upon the particular amp/transducer combination.

Cheers,

Dave.

[mboxler]

The question was not intended as a platform to debate single driver speakers vs multi-driver speakers.  Nor was it intended to argue whether a Zobel was needed in a given design or not.  It was intended to determine what penalties a Zobel might impose if the designer felt that it's impedance flattening benefits were justified to begin with, for a given combination of speaker, cable and amp.

Any further insights would be appreciated.  Thanks.

You may have already read this from Rod Elliott, but...

The Zobel network will flatten the impedance of the speaker, but at the cost of power dissipation, and a slightly lower than expected overall impedance. Naturally, the power dissipated by the resistor is turned into heat, not sound, reducing effective efficiency. The lower impedance may cause some stress to certain amplifiers, but most should be able to cope with the slight extra loading. It must be understood from the outset that the flattened impedance curve does not make the speaker perform any better at the higher frequencies - the sole purpose of the Zobel network is to ensure that the impedance presented to the crossover network remains essentially constant over the frequency range where variations would cause an unacceptable frequency response variation in the filter network. The determination of the required values for the Zobel network is most easily done by measurement and experimentation.

Once determined, the Zobel network must be treated as part of the loudspeaker. All measurements or calculations for the crossover network must include the Zobel network and loudspeaker driver combined. If correctly done, the combination of the two will give an acceptably flat and very usable impedance across the entire crossover region. This will result in a crossover filter with the minimum error possible.

[neobop]

Vance Dickason says much the same. 
All voice coil drivers exhibit a rising impedance and a zobel ensures woofer or midrange low pass to operate at proper frequency.  Also used on tweeters to smooth response or present proper imprdance for frequency response correction.

In practice, it doesn't always work out.  Sometimes you're better of adjusting the values of the crossover components IMO.  It can make a driver sound dead, lifeless, although it can be effective in smoothing out the high end of a driver, even tweeters. 

What Elliott implies is overly optimistic.  Even with high powered solid state amps, the sound of the driver will change.  The power absorbed by the resistor might present an even impedance to the amp, but will also absorb power that would have gone to the driver.
It might be beneficial though, depending on the driver. 

Zobels are particularly effective as ultrasonic filters used with extended bandwidth amps.  If you have a problem with RF, you'll hear a reduction of intermodulation distortion. 
neo

[Quiet Earth]

The power absorbed by the resistor might present an even impedance to the amp, but will also absorb power that would have gone to the driver.

You mean it will absorb power that would not have gone to the driver. (Or not used by the driver, or reflected back into the amp, etc.,)