[Peter Wieck[_2_]]

RANT WARNING!

Guys and gals, there is common sense (which isn't), and then, there is received wisdom (AKA: Religion) when it comes to audio. Typically, but not always, they are mutually exclusive. Also commonly practiced in this hobby/religion are several common fallacies, the most prominent of which a

1. Leaping to conclusions: My cat is grey, therefore all cats are grey.
2. Begging the question: Given that all cats are grey, therefore my cat must be grey.
3. False premises: My cat is wet, therefore it rained last night.

What brought this on was Trevor's post on fuses, which more-or-less encompasses two 1 & 3 of the above, with a glancing blow to 2.

Some Math:

If Output Watts = V^2/Speaker Impedance
Then V = Square Root of output watts x Impedance

OR: If watts =30
Impedance = 8
Voltage = 15.5
Amps = watts/volts
OR: 2 A in this model

Which, of course, will vary as the actual impedance differs from the nominal impedance.

A 4 amp fuse will not even warm up under normal operating conditions - and well-designed speakers will be able to handle a 30-watt input all day and all night as long as there are no/limited DC components. Sources of DC components could be from clipping in an amp with limited protection circuits, or catastrophic failure in one-or-more internal components. At which point the fuse comes into play. Aren't you glad that it was?

Other problematic speaker-damage sources: A user chooses to send a pure sine wave into a speaker at full volume. The fuse WILL NOT protect the speaker in this case, and 30 watts is 30 watts = heat. Even the very best voice coils will not withstand a constant 30 watts at a single frequency. Similar damage may be caused by a feedback loop.

Point being that a fuse is a line of defense that when deployed protects your speakers better than _ANY_OTHER_OPTION_.

That fuses can add distortion at audible frequencies does not mean that they do add distortion.
That a fuse once added distortion does not mean that all fuses add distortion.
That the speaker is distorting does not mean that the fuse is the cause.

And, of course, I could get started on the many types of fuses out there - including an entire cohort based on audiophoolery.

Peter Wieck
Melrose Park, PA