Anybody done the research on AR/KLH "Hot Cross Bun" treatment?

[tgmartin]

I'm curious about the why and how of the "hash tag" or "hot cross bun" application of stiff glue or something on some AR and KLH woofers. I own a pair of KLH Model 30s that have this treatment from the factory. I've also seen it in web pics on some others:

KLH Model 30


KLH Model 32


AR4


AR4x


The KLH Model 32 pic above shows the treatment sitting on top of the cone and looks like it would add some mass and possibly stiffness, maybe damping some modes of vibration. The crossover in the Model 32 is like the Model 30 in that there is no low pass inductor to roll off the woofer's contribution to mid-range chatter and I wonder if the treatment *may* tend to roll off the upper range of the woofer.

The picture of the AR4x looks like the treatment was absorbed into the cone material, so I have no notion of what it may do ... Any ideas? Thanks in advance for any light you could shed on this!

 

[tgmartin]

... crickets ... The silence is DEAFENING ... I ain't skeeered ... Do you think it's PRIMARILY for mass loading the cone to lower Fs? Or is it a double-bill to also modify/damp the higher frequency modes of vibration of the cone?

... probably more crickets ...

 

[A400]

I suspect it’s to modify cone breakup, given the location and probably minimal filtering in the crossover. A brief search suggests this info is already within the classic speaker pages.

For mass loading I’d expect it to be heavier and nearer the voice coil, or distributed to increase stiffness.

 

[tgmartin]

Guess I need to sharpen my search strings ... THANKS! I'll dig a little deeper.

 

[loudnoises]

My klh 5 also has these iirc. Definitely was more visual than mass.

 

[RVT1K]

Based on nothing but a gut feeling, it looks like some sort of tuning process that drivers went through during manufacturing.

 

[tgmartin]

Well, I've tried a number of things when searching the Classic Speaker Pages and haven't come up with any info regarding the "cross hatch", "hot cross bun", "hash tag" pattern ... Admittedly, I'm not a member there as I tried THAT too, with no success! FAIL, FAIL FAIL! After a few search attempts I get the "Don't try search for 5 seconds" warning and it freezes completely.

I think A400 probably has it right but it would be interesting to read any educated threads ...

 

[A400]

I searched a bit more and either couldn’t find my earlier search, or it initially looked more promising than it was. I did find the thread below though and a quote from the legendary Zilch:
KLH speakers

Damping spurious resonances of the cone.

AR did it on early AR4xs.... :yes:

 

[tgmartin]

Thanks for checking back with that, A400!