[Pete Schumacher]

You're saying if I hook up a zobel to an 8" full range driver which is connected directly to an amplifier, it will sound the same as w/o the zobel?

I find this hard to believe.

neo

That is correct, hard to believe or not.

If we are talking tube amps, with higher output impedance, then the difference between zobel and no zobel might be audible because the frequency response would change by as much as a 1dB or more depending on frequency, driver impedance variation and output impedance of the amp.

But with a solid state amp, with LOW output impedance, the voltage across the driver will not change appreciably (less than .1dB) and I dare say that such a change would be inaudible.

[neobop]

I've never built a fullrange speaker so I can't say from experience, but I've read just the opposite from what you're saying about changing the sound of such a driver.  Maybe there's more to it than voltage across the terminals, but I don't know exactly what that is.   I've also read about smoothing the sound of a tweeter with a zobel.  Usually a high pass filter was used, but no low pass.  I quoted Vance Dickason and he said the same thing.  I suppose he, and numerous others are imagining things.

Do you design Vapor speakers?  If so, do you use zobels?   
neo

[Pete Schumacher]

I've never built a fullrange speaker so I can't say from experience, but I've read just the opposite from what you're saying about changing the sound of such a driver.  Maybe there's more to it than voltage across the terminals, but I don't know exactly what that is.   I've also read about smoothing the sound of a tweeter with a zobel.  Usually a high pass filter was used, but no low pass.  I quoted Vance Dickason and he said the same thing.  I suppose he, and numerous others are imagining things.

Do you design Vapor speakers?  If so, do you use zobels?   
neo

I don't know what Vance Dickason's context is, so I really can't comment.  But when you're talking about tweeters with HP filters on them, the use of a zobel can prevent the tweeter output from rising with frequency.  I've done that myself when using the SEAS 27TBFC/G, which happens to have a significant impedance variation over its usable range.  If there's some padding on the tweeter (series resistance) to bring its sensitivity down to the woofer its paired with, the tweeter output can rise significantly in the upper octaves.  The use of a zobel helps prevent that and maintain a smooth response.  Of course, none of that matters if the solid state amp is directly across the tweeter leads since its now being driven by a voltage source.

Fullrange speakers tend to be higher sensitivity drivers, and more often than not, paired with tube amps because of that.  In those cases, a zobel will have an effect on the sound since it is altering the load impedance.  Tube outputs are more sensitive to load impedance variation than solid state. 

But I've seen very few full range drivers that would not benefit from the use of a few passive crossover components to smooth out the response, whether connected to SS amps or Tubes.

I do help with the design of Vapor Audio speaker systems.  We use no zobels on any tweeter networks.  And we only use "zobels" on woofer networks to modify the filter Q, since the woofers we use all have very flat impedance profiles through their usable range.  In other words, we don't use zobels in the traditional sense, for flattening the impedance curve of the driver.  Our Breeze models use a total of 4 crossover components, with one of those being a resistor on the tweeter.  No zobels at all in either model.  The crossovers are 2nd order acoustic slopes.