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The Basement
speakers start on fire at Local Hockey Rink
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<blockquote data-quote="Ivan Beaver" data-source="post: 50070" data-attributes="member: 30"><p>Re: speakers start on fire at Local Hockey Rink</p><p></p><p></p><p>While amps are often quick to be blamed-I would argue that most of the time this is not the case.</p><p></p><p>Let's take the case of the typical amplifier that goes "DC" and does not have any protection against this DC getting to the output/speaker.</p><p></p><p>The loudspeaker on the other end (in most cases) would die a VERY quick death. This would produce very little heating of anything except the voice coil. The driver would open up before anything else could get hot.</p><p></p><p>And if the crossover would start to be suspected of the cause of the burn-let's look at that. On the high freq side the first thing in line is a capacitor. That would stop the DC from going any further-(capacitors act an open to DC) so no damage there.</p><p></p><p>On the woofer side of things-the "basic" crossover is a coil in series and possibly a cap in parallel with the woofer. So the coil will pass the DC just fine (as if it were a piece of wire-which it is at DC) and onto the woofer voice coil. The voice coil would open-and then the current flow would simply stop. There is nowhere for the voltage on the other side of the coil to go-remember that the parallel cap will block the DC.</p><p></p><p>So while the loudspeaker will "die" from an amp "going DC"-it is not likely to cause it to catch on fire.</p><p></p><p>It is real easy to "jump to conclusion", but often we have to look a bit further into what the REAL causes may be.</p><p></p><p>I HIGHLY doubt it is was an amp that "went DC". An amp that was oscillating-however- would be a different story.</p><p></p><p>Another note about the Crown DC300's. I hear them "blamed" at lot for "going DC". I think this is mostly in the name. THe name is there because the amp does not have any capacitors in the signal path-so that it can have a response all the way to DC. In fact they have often been used as a DC power supply-I have done it myself to power a console.</p><p></p><p>In all my years as a bench tech-both for music stores and my own repair businesses-I have NEVER had a DC300 come in for repair that had "gone DC". I'm not saying they can't, but I never saw it in all of my years. It was usually a distortion at higher power levels (once it got past the class A stage) that was the cause.</p><p></p><p>I do have an "official" Crown service manual for the DC 300. The name is "300 watts and a puff of smoke".</p><p></p><p>All I am saying is there are MANY MANY things/ideas in this industry that get "thrown around" without any first hand experience or any basis. Somebody says it-and it gets passed on and on and on etc.</p></blockquote><p></p>
[QUOTE="Ivan Beaver, post: 50070, member: 30"] Re: speakers start on fire at Local Hockey Rink While amps are often quick to be blamed-I would argue that most of the time this is not the case. Let's take the case of the typical amplifier that goes "DC" and does not have any protection against this DC getting to the output/speaker. The loudspeaker on the other end (in most cases) would die a VERY quick death. This would produce very little heating of anything except the voice coil. The driver would open up before anything else could get hot. And if the crossover would start to be suspected of the cause of the burn-let's look at that. On the high freq side the first thing in line is a capacitor. That would stop the DC from going any further-(capacitors act an open to DC) so no damage there. On the woofer side of things-the "basic" crossover is a coil in series and possibly a cap in parallel with the woofer. So the coil will pass the DC just fine (as if it were a piece of wire-which it is at DC) and onto the woofer voice coil. The voice coil would open-and then the current flow would simply stop. There is nowhere for the voltage on the other side of the coil to go-remember that the parallel cap will block the DC. So while the loudspeaker will "die" from an amp "going DC"-it is not likely to cause it to catch on fire. It is real easy to "jump to conclusion", but often we have to look a bit further into what the REAL causes may be. I HIGHLY doubt it is was an amp that "went DC". An amp that was oscillating-however- would be a different story. Another note about the Crown DC300's. I hear them "blamed" at lot for "going DC". I think this is mostly in the name. THe name is there because the amp does not have any capacitors in the signal path-so that it can have a response all the way to DC. In fact they have often been used as a DC power supply-I have done it myself to power a console. In all my years as a bench tech-both for music stores and my own repair businesses-I have NEVER had a DC300 come in for repair that had "gone DC". I'm not saying they can't, but I never saw it in all of my years. It was usually a distortion at higher power levels (once it got past the class A stage) that was the cause. I do have an "official" Crown service manual for the DC 300. The name is "300 watts and a puff of smoke". All I am saying is there are MANY MANY things/ideas in this industry that get "thrown around" without any first hand experience or any basis. Somebody says it-and it gets passed on and on and on etc. [/QUOTE]
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