Blown" speaker question

David Cobb · Post by **David Cobb** » 28 Mar 2004 4:57 pm

1. What is it that's happened inside a speaker when we say "it's blown"?
Is there physical damage to a speaker component?
2. What determines the speakers' signal handling capacity?
Why is one good for only 100W and another rated for 350W?

John Floyd · Post by **John Floyd** » 28 Mar 2004 7:31 pm

<BLOCKQUOTE>quote:<HR>1. What is it that's happened inside a speaker when we say "it's blown"?
Is there physical damage to a speaker component?<HR></BLOCKQUOTE>
The voice coil has opened due to to excessive current being drawn thru it this can be caused by a couple of things.
1. Being overdriven by a power amp which exceeds the speakers power rating.
2. A solid state amplifier which has blown or shorted out put transistors causing excessive current to be drawn thru the Speaker Voice coil.
<BLOCKQUOTE>quote:<HR>2. What determines the speakers' signal handling capacity?
Why is one good for only 100W and another rated for 350W?<HR></BLOCKQUOTE>
The gauge and type of wire used in manufacturing the Voice coil and the type and weight of the speaker magnet. Heavier components usually means more power handling capability

David Cobb · Post by **David Cobb** » 28 Mar 2004 9:36 pm

John,that helps.
I guess I'd have to dismantle a ruined speaker to get a better grasp of what's happening.
Your mention of how a failing power amp could stress a speaker is something I hadn't heard of.
What I'm hearing is less than silky smooth and so far I'm blaming the preamp and/or the power amp.

Dave Boothroyd · Post by **Dave Boothroyd** » 28 Mar 2004 10:38 pm

John describes a speaker coil which is truly "blown", in that the voice coil has melted under too much current.
If your speaker is still working, but sounding rough, that has not quite happened.
It could be that the coil has got hot enough to become partially detatched from the cone.
Alternatively, there could be debris in gap between the coil and the magnet, or the cone itself may have been damaged.
Finally, it might be a case of garbage in -garbage out. The speaker might be faithfully reproducing the sound of a distorting amp.
Cheers
Dave

Murnel Babineaux · Post by **Murnel Babineaux** » 30 Mar 2004 12:46 am

The voice coil material, and more importantly, the diameter of the voice coil are crucial factors for power handling and limiting distortion at medium to high power levels. For woofers, the Xmax (voice coil overhang-excursion maximums are important for moving air, typically between 2.5mm and 18mm.
www.cajunsteelguitar.com [This message was edited by Murnel Babineaux on 30 March 2004 at 12:54 AM.]

David Cobb · Post by **David Cobb** » 30 Mar 2004 2:58 pm

I feel like I'm learning a bit.
Until I can get the equipment checked, I'm going with the damaged output transistor theory.
I wonder what the maximum sized voice coil is, if bigger is better. 4"?