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  #1  
Old 10-19-2005, 09:09 AM
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Speaker Protection using Lightbulbs??

Recently I was looking at the BOSE 301 speakers (NO BASHING!) and came across a webpage (german though) which showed the inside of the speakers. Every BOSE speaker has this " Automatic Protection Circuitry" which prevents the speakers from being "overdriven".

I didnt know what it was but now looking at the pictures and doing some translating, apparently a lightbulb turns on inside the speakers when the voice coil gets hot? This is very interesting!

http://www.avguide.ch/index.cfm/show/page.view/uuid/392EFDF8-8A11-97B0-4619C4153CA42F96

Anyone care to explain more?
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  #2  
Old 10-19-2005, 09:13 AM
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I think what it does is use the temp resistance characteristics of the bulb filament to limit the spikes which will heat the filament.increasing the resistance at that moment and threerfor disipating the spikes.or limit them from the resitance as the filament heats.....I believe I read a description of how that works almost 2 decades ago.....
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Old 10-19-2005, 09:19 AM
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Hi-end manufacturers avoid this and the use of fuses for protection. The audio signal has to pass through a filament in this case... no thanks!
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Old 10-19-2005, 10:45 AM
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Agreed! What's the point of running expensive zero-gauge oxygen-free copper wiring to a set of speakers whose final signal path is a thin piece of tungsten?
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  #5  
Old 10-19-2005, 10:56 AM
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Quote:
Originally Posted by G-Benz
Agreed! What's the point of running expensive zero-gauge oxygen-free copper wiring to a set of speakers whose final signal path is a thin piece of tungsten?
Or a fuse, binding post, or cheesy crossover ?
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  #6  
Old 10-19-2005, 10:57 AM
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Quote:
Originally Posted by crash9
Or a fuse, binding post, or cheesy crossover ?
My speakers don't have crossovers! I can tell you that it DOES make a big difference to my ears, FWIW.
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Last edited by cscmc1; 10-19-2005 at 11:15 AM.
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  #7  
Old 10-19-2005, 11:07 AM
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So when does this lightbulb turn on? When I crank the speakers and leave it cranked?
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Old 10-19-2005, 11:10 AM
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Quote:
Originally Posted by BenzOnline
So when does this lightbulb turn on? When I crank the speakers and leave it cranked?
Probably just during transient peaks. I had a set of DCM speakers (I think) that had a feature like this. The bulb was visible (a "gee whiz" thing that helped sell speakers, I am sure) and lit once in a while. I guess it just transforms what could be damaging spikes to light energy by charging that filament. Dunno... surely the US-spec Bose have the same thing (?). Did you check their site?

Edit -- *I* just checked the US site and they're not mentioned. Just that that speaker has "protection circuitry." Presumably the same light bulb.
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  #9  
Old 10-19-2005, 11:16 AM
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Yeah checked the site and this is known as "Automatic Protection Circuitry" which prevents the speakers from being overdriven at high volumes it says.

All of their speakers have it.
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Old 10-19-2005, 11:21 AM
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Quote:
Originally Posted by BenzOnline
Yeah checked the site and this is known as "Automatic Protection Circuitry" which prevents the speakers from being overdriven at high volumes it says.

All of their speakers have it.
I never quite got that. There's a greater risk of damaging a speaker by UNDER-driving it than by over-driving. Just listen... when distortion occurs, turn it down! Duh! Maybe in mega-watt PA applications there is a risk of melting the voice coils of woofers with too much power that you won't hear as distortion, but in home use? I have never run into any such thing.

One year at CES, Hartley demo'd the durability of one of their big-a$$ subs by hooking it up to an AC line. McIntosh's biggest solid state amp can supposedly be used to arc-weld in a pinch.
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  #11  
Old 10-19-2005, 11:31 AM
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BOSE:

Automatic protection circuitry
Circuitry protects drivers from being overdriven and provides increased reliability without interfering with the listening experience.
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Old 10-20-2005, 01:17 PM
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Quote:
Originally Posted by cscmc1
McIntosh's biggest solid state amp can supposedly be used to arc-weld in a pinch.
Jeez, welding with a/c...what a PITA!
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Old 10-20-2005, 02:03 PM
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Quote:
Originally Posted by R Leo
Jeez, welding with a/c...what a PITA!
You said it. My jaw dropped when I read that (I think it was in a Stereophile or The Absolute Sound review).
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  #14  
Old 10-22-2005, 06:06 AM
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Quote:
Originally Posted by G-Benz
Agreed! What's the point of running expensive zero-gauge oxygen-free copper wiring to a set of speakers whose final signal path is a thin piece of tungsten?

Why bother paying all that money for a percieved effect?
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Old 10-23-2005, 08:10 AM
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The same folks that do so buy all sorts of snake-oil gadgets...but they have the means to do so.

I know a guy who mounted large concrete blocks on top of his tract-home priced mono amps to isolate signal path vibrations caused by "capacitor clatter"!
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