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"stiff" woofer


jwc

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Again, the woofer plays music but no low end and the multimeter impedance check matches the other three woofers.

 

I uninstalled it....which was a PITA.  It's like the cone is glued.  Won't move at all.

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1 hour ago, jwc said:

Again, the woofer plays music but no low end and the multimeter impedance check matches the other three woofers.

 

I uninstalled it....which was a PITA.  It's like the cone is glued.  Won't move at all.

Do you the know the make and model of the woofer? Does it have a vent hole in the magnet? There seems to be enough movement to make sound waves but something is limiting the travel. So, a warped coil former, loose coil winding or something in the gap.

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On 1/7/2019 at 1:05 PM, jwc said:

I haven't measured distortion.  Plays music clearly....just lacks punch.    Sounds like a 6" woofer.

Looks like you found the problem. Thermal compression in driver occurs in the range of 10-20% of rated power handling. This is why horns are great because they reduce the power required to generate a given Sound Pressure Level by their 10-16 db in efficiency gain, with proportional reduction in Voice Coil heating and movement to approximately 1/8th vs. a direct radiation with the same driver. Hence, the reason very few horn drivers ever blow like that. Care to guess as to how many 15's and 18's used in PA systems get reconed every year? I think it's what keeps Eminence in business!!

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  • 2 months later...
On 1/8/2019 at 12:24 PM, BEC said:

Our buddy Terry Cruse sent me a K-33 out of a Cornwall to see why it did not work many years ago.  He had just reached (I believe) 124 db and suddenly the woofer was just silent.  When I cut into it found the voice coil had come out of the magnet gap and then just impacted back into the top of the magnet assembly crushing it in the process.  Might be what happened to yours.

 

Bob Crites

 

Sounds like he threw a rod.

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