Purpose of the wizzer cone?

tomchr

Member
Paid Member
2009-02-11 12:58 am
Calgary
www.neurochrome.com

Erknie

Member
2016-02-25 11:27 pm
Hey all!. I have this question about dual cone full range drivers. Is the wizzer cone an emissive high frequency diaphragm OR a horn to the dome/ dust cap
that would be the high frequency emissive part?...

The whizzer cone is rigidly attached to the voice coil, so it moves with it, unlike the main speaker cone which will usually has some compliance at the join to the voice coil to detach it from high frequency movements, letting the voice coil with whizzer move faster. You can't just put a whizzer on any old speaker, it needs the main cone to be compliant at the join, so it doesn't dampen the voice coil movement, you have to design it that way from the start.

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Maybe I'm way off base, but I'm not so sure that the majority of FR drivers - with or without whizzers- will have the degree of compliance implied above at the joint between voice coil and main cone. Indeed past a minor amount, wouldn't there be some some degradation of low level higher frequency signals, particularly in whizzer-less designs - some of which use different materials and interesting profiles on the "dust cap" to act as HF emitting surface.

I always thought it was the material and design of the rear suspension (spider) that was engineered to provide the compliance at that end of the drive train.
 
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I think the compliant material is the glue.


Well, there's glue, and then there's glue - for cabinetmakers, think Gorilla moisture cured polyurethane vs Sikabond construction adhesive - both stick things together, but the former is far less resilianat (more brittle) than the latter.

But time to step down from my little soapbox, and contribute something meaningful to these forums, and STFU

cheers
 

Shoog

Member
2002-08-15 10:16 pm
Eire
There is always going to be interference between the wave coming off the back of the whizzer and the wave coming off the shaded portion of the main driver. This will result in muddied and uneven response in the critical human voice range.
I have never heard a whizzer cone driver I liked and then have never matched up to drivers with ultralight paper cones with controlled flexure. To my opinion they are a sticking plaster to make over heavy diaphrams work as fullrangers. An unacceptable compromise to my mind.

Shoog
 
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The comb filtering between the back of the whizzer and the main cone can be seen clearly on some drivers freq response, but it is easily fixed with some foam or polyfill stuffed behind the whizzer (the 99c tweak). It's been a while, but IIRC it was from about 3 or 4k to about 6k on the old Radio Shack 1354, so technically it's out of the voice range. The 99c tweak mostly corrects it, but the improvement is rather subtle by ear.

Strangely enough, for decades the prevailing theory was that the whizzer itself decoupled from the voice coil, and somehow resonated at HF leading to the illusion of extended range. I always thought that theory was bassackwards. Glad that it seems to be corrected in the current paradigm.

RE glue: no doubt a compliant glue will help mechanical decoupling, but IMO it's not necessary, as the mass and compliance of the main cone itself will cause it to decouple in the high frequencies. I suspect that is the main mechanism in most cases. Think of it as a large surround or spider for a small cone tweeter. Functionally, it is much the same.
 

Erknie

Member
2016-02-25 11:27 pm
The purpose of the compliant material at the join is not to stop the main cone from trying to move at high frequencies, it's to stop the main cone mass slowing down the movement of the voice coil at high frequencies. The compliant material is very important for a good whizzer setup.
 
Lowthers and whizzers

There is always going to be interference between the wave coming off the back of the whizzer and the wave coming off the shaded portion of the main driver. This will result in muddied and uneven response in the critical human voice range.
I have never heard a whizzer cone driver I liked and then have never matched up to drivers with ultralight paper cones with controlled flexure. To my opinion they are a sticking plaster to make over heavy diaphrams work as fullrangers. An unacceptable compromise to my mind.

The only whizzer drivers I have used are Lowther DX4 drivers and I have tried them a number of ways. I don't agree with the hypothesis that the whizzer causes a muddiness in the midrange. If these drivers are used as widerange drivers, then reproducing bass is a primary reason why Lowther drivers can sound muddy. Removing the bass from Lowthers (and reproducing the bass using a separate woofer) helps significantly to clean up the Lowther midrange.

Using the Lowthers in backloaded horn cabinets makes the midrange muddy as well, most likely because the sound from the back of the driver is reflected quickly back through the thin driver membrane, and this sound is 180 degrees out of phase with the sound coming of the front of the driver. The compression chamber for the back horns can cause the Lowther cone to deflect which could also cause the Lowther drivers to sound muddy. Lowthers are much more clearer sounding when they are mounted on open baffle or in front horns.

Finally, I borrowed a pair of Lowther drivers which were treated with EnABLe. This made a substantial improvement in the quality of the midrange (particularly, less muddy midrange). I don't know if the improvement is mostly due to the dots added to the cone or the conformational coating, but Lowther drivers are much improved with EnABLe. But, these drivers still had the whizzer cones, and this seems to demonstrate that if used in its best configuration, the Lowthers are outstanding midrange drivers (essentially as good as anything out there).

I recall that there was a shootout between compression drivers in front horns and Lowthers in front horns, and most preferred the Lowthers.

Another data point, Nelson Pass once commented that the best midrange drivers that he ever heard are Feasterex and Field Coil Lowthers.

I can understand if you have had limited experience with whizzer style drivers why you would conclude that it could be the whizzer. Based on my experience, I suggest otherwise.

I think that if you made reference to the poor quality of higher frequencies reproduced by whizzer cones, which are sourced largely from breakup modes, you would likely receive little to no complaint. Although, I was surprised when I heard the EnABLe treated Lowther drivers, because the high frequencies were much better as well.

Retsel
 

Shoog

Member
2002-08-15 10:16 pm
Eire
Its an inescapable fact that there will be a comb effect of interference between the whizzer and the main cone and it is very clearly visible on the frequency response curve on most of these drivers from 7khz up. The cancellation and addition effects can be well over 6db.

Look at the graphs if you don't believe me.

Shoog