whats the purpose of a magnet rubber boot?

PreSapian · 28th April 2011, 10:11 AM

my dayton rs180 came with a magnet rubber boot that can be taken off. and when i do, the sound becomes more 'ambient' with better defined lower mids. when it's put back on the sound is 'cleaner' with a tad better imaging but overall feel muffled comparison. you may already have guessed that i like it better with the boots off..

but i'd still like to know if this ambiance i'm hearing is the magnet ringing from eliminating the boot to serve it's purpose. so what are the rubber boots for?

AllenB · 28th April 2011, 10:29 AM

Sure, they must provide some damping, and also some protection. They may also add percieved value to the driver and a sense that the magnet is larger than it is.

One question, are they covering up a pole piece vent?

PreSapian · 11:01 AM

no, it's just a ring surrounding the side of the magnet. but i'd like to know the sound of magnet ringing can attribute to more 'air' and resonance around the notes, or if that's entirely a positive side effect from the boots coming off.

Max Caliber · 28th April 2011, 11:53 AM

Hi PreSapian

It’s probably like the rubber gasket that JBL used in the 80’s when they replaced the smaller but more powerful alnico magnets (that had a metal magnetic shield cover) with the heavier ceramic magnets where a larger metal shield cap would have added much unnecessary weight.

The original purpose of this metal cap was to refocus the stray external magnetic field back into the voice coil gap which allowed them to use a smaller magnet assembly. It was also a major selling point for them at the time where they were showing off how their drivers had little stray magnetic fields because of the metal end-cap. However when JBL came out with the ceramic magnets on their drivers they wanted to maintain this closed magnetic shielding for both the publicity and the extra power it delivered into the VC gap but a bigger metal cover was just too costly so they used a ferromagnetic rubber that was intended to replace the steel cover.

Later on with the advent of home cinema the importance of magnetic shielding to protect CRT displays became the main reason for using this shield.

Yes removing it or keeping it can and will affect the performance of your drivers and this could also be a major concern if you have a vacuum tube CRT display close-by as it will eventually magnetize the color shadow-mask of your TV.

Cheers

Philip

badman · 28th April 2011, 04:15 PM

I had no idea it was ferric, always thought it was just there to protect the magnet. Must be a lot of iron in it if it's to be effective... seems odd....

speaker dave · 28th April 2011, 08:20 PM

They weren't "ferric". They were just rubber boots to dress up the appearance. Ceramic ring magnets aren't pretty and are also very sharp edged. the Alnico pots with the gray crackle paint had a classy appearance and the rubber tires were added to diminish the difference.

(I was there.)

David S.

Robh3606 · 28th April 2011, 09:19 PM

Quote:

They were just rubber boots to dress up the appearance.

Not only that but on drivers installed into systems most drivers didn't have a foil label or the boot installed. They just had a white stencilled part number. They saved the rubber boots for drivers that were sold individually for apperance sake as David says.

Rob

simon7000 · 28th April 2011, 09:28 PM

Rubber rings are placed on the ferrite magnets of drivers that can be sold as individual units to dress them up and keep the magnet from getting struck and chipping. As they are powerful magnets they will tend to smack into each other or anything magnetic nearby.

badman · 28th April 2011, 10:15 PM

Quote:

Originally Posted by speaker dave

They weren't "ferric". They were just rubber boots to dress up the appearance. Ceramic ring magnets aren't pretty and are also very sharp edged. the Alnico pots with the gray crackle paint had a classy appearance and the rubber tires were added to diminish the difference.

(I was there.)

David S.

Quote:

Originally Posted by Robh3606

Not only that but on drivers installed into systems most drivers didn't have a foil label or the boot installed. They just had a white stencilled part number. They saved the rubber boots for drivers that were sold individually for apperance sake as David says.

Rob

Quote:

Originally Posted by simon7000

Rubber rings are placed on the ferrite magnets of drivers that can be sold as individual units to dress them up and keep the magnet from getting struck and chipping. As they are powerful magnets they will tend to smack into each other or anything magnetic nearby.

Indeed, that's what I thought, some of my own JBLs are "PL" versions, standing for "protector-less", and came out of the SR4725.

aptquark · 28th April 2011, 10:43 PM

my JLAudio subs have them. Also, they help alot when you accidentally drop a sub on your toes.

28th April 2011, 10:11 AM	#1
PreSapian diyAudio Member Join Date: Sep 2009 Location: seoul	whats the purpose of a magnet rubber boot? my dayton rs180 came with a magnet rubber boot that can be taken off. and when i do, the sound becomes more 'ambient' with better defined lower mids. when it's put back on the sound is 'cleaner' with a tad better imaging but overall feel muffled comparison. you may already have guessed that i like it better with the boots off.. but i'd still like to know if this ambiance i'm hearing is the magnet ringing from eliminating the boot to serve it's purpose. so what are the rubber boots for?

28th April 2011, 10:47 AM	#3
PreSapian diyAudio Member Join Date: Sep 2009 Location: seoul	no, it's just a ring surrounding the side of the magnet. but i'd like to know the sound of magnet ringing can attribute to more 'air' and resonance around the notes, or if that's entirely a positive side effect from the boots coming off. Last edited by PreSapian; 28th April 2011 at 11:01 AM.

28th April 2011, 04:15 PM	#5
badman Custom Title diyAudio Member Join Date: Sep 2003 Location: Sunny Tustin, SoCal	I had no idea it was ferric, always thought it was just there to protect the magnet. Must be a lot of iron in it if it's to be effective... seems odd.... __________________ I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!

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28th April 2011, 10:29 AM	#2
AllenB diyAudio Member Join Date: Oct 2008	Sure, they must provide some damping, and also some protection. They may also add percieved value to the driver and a sense that the magnet is larger than it is. One question, are they covering up a pole piece vent?

28th April 2011, 11:53 AM	#4
Max Caliber diyAudio Member Join Date: Jul 2010 Location: Laval	Hi PreSapian It’s probably like the rubber gasket that JBL used in the 80’s when they replaced the smaller but more powerful alnico magnets (that had a metal magnetic shield cover) with the heavier ceramic magnets where a larger metal shield cap would have added much unnecessary weight. The original purpose of this metal cap was to refocus the stray external magnetic field back into the voice coil gap which allowed them to use a smaller magnet assembly. It was also a major selling point for them at the time where they were showing off how their drivers had little stray magnetic fields because of the metal end-cap. However when JBL came out with the ceramic magnets on their drivers they wanted to maintain this closed magnetic shielding for both the publicity and the extra power it delivered into the VC gap but a bigger metal cover was just too costly so they used a ferromagnetic rubber that was intended to replace the steel cover. Later on with the advent of home cinema the importance of magnetic shielding to protect CRT displays became the main reason for using this shield. Yes removing it or keeping it can and will affect the performance of your drivers and this could also be a major concern if you have a vacuum tube CRT display close-by as it will eventually magnetize the color shadow-mask of your TV. Cheers Philip

28th April 2011, 08:20 PM	#6
speaker dave diyAudio Member Join Date: Nov 2009 Location: Toronto	They weren't "ferric". They were just rubber boots to dress up the appearance. Ceramic ring magnets aren't pretty and are also very sharp edged. the Alnico pots with the gray crackle paint had a classy appearance and the rubber tires were added to diminish the difference. (I was there.) David S.

28th April 2011, 09:28 PM	#8
simon7000 diyAudio Member Join Date: Nov 2008 Location: Oakmont PA	Rubber rings are placed on the ferrite magnets of drivers that can be sold as individual units to dress them up and keep the magnet from getting struck and chipping. As they are powerful magnets they will tend to smack into each other or anything magnetic nearby.

28th April 2011, 10:43 PM	#10
aptquark diyAudio Member Join Date: Jun 2010 Location: MS Blog Entries: 1	my JLAudio subs have them. Also, they help alot when you accidentally drop a sub on your toes.

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