Re: Protection of investment

Patrick Turner wrote:


Phil is correct here and some amps could be be damaged if the tweeter is disconnected if a fuse in series with it blows.
I have had to repair the damage done with over driven amps at end of school year parties where the speakers have fried, but amp fuses
didn't blow, then the crossovers melted, and finally the amp thermalled out with lots
of fused output and driver bjts. The amp fuses only blew after major heat damage
had occurred.
Fuses to each driver ahead of crossovers were not fitted, and not even
polyswitches.
But I have seen exploded polyswitches, so apart from active protection which shuts down the amp then fuses can if chosen well, help
stop the smoke.

Okay, I don't plan on over driving any amps, I have a Carver M 1.5t and a Bryston 4B and they stay well below clipping. I am most worried about as someone mentioned earlier sudden spikes and such and I know distortion is the enemy more than power and the Mirage M1s are recommended for an amp of 100 to 500 watts. So I may be overly worried about a ghost here since neither amp should cause damage if kept below the clip point and used with certain reason. And as I said the damage could have been done by the former owner. I'm just grasping at trying to keep from blowing what is now a non existent component.



If there is a C&L second order crossover filter then this becomes a low
impedance resonant LC circuit
of low Z at the Xover F without being loaded by the the tweeter if a
fuse blows.

To be able to place a safety fuse of LOW AMP VALUE in series with a
tweeter where there is an L&C filter, the fuse should be ahead of the C&L filter.

If there is only a C in series with the tweeter, the fuse should still
be ahead of the C.


Well, IDK WTF is in there. I can dig in and see the crossover in the M7si speakers by removing the front woofer, but not in the M1 speakers. There are wooden baffles inside the cabinet that keep you from seeing them. Now both the M1 and M7si are wired to be biamplified and they have jumper wires for using a single amp. The fuse could be placed at that point, but I'm sure there would be a consequence of a fuse that would protect the tweeter would be too small and blow too easily when put in front of both midranges and tweeters. I should also mention that on the M1 there is two of everything, high, mid and low.



The lowest value fuse should be used without causing nuisance blows at
normal levels.

Continuous power handling by tweeters is often no more than 10% of the rated continuous input power so if it says 100W on the box, assume the
tweeter could take no more tha 10 watts.

A tweeter of 5.2ohms with 10 watts can take only 7.2Vrms applied, or
1.38 amps,rms,
so a 0.5A fuse could be tried first. If that blows at levels desired,
use 1A,
and if that blows, don't ever assume that a 1.5A will stop a tweeter
from frying itself to death.

Patrick Turner.

This is what I had exactly planned, BUTT... what the plan was and recommended by a number of people to put it in line at the tweeter. But if this has a high chance of causing damage to one of these two amps without blowing the fuse in the amp, I'm not so sure about doing it. Hell the M 1.5t doesn't even have speaker fuses but that amp is a bit different. But like I said when said fuse blows the amp is not going to be in an "abused" state, it may be at clip point but just barely.

Another point on previous abuse. The M1 is an extremely inefficient speaker. I've run the Carver amp on Altecs, Electro Voices, Wharfdales, University, JBL, B&W and Snell and the previous owner on Thiels, and Von Schweikert's and it is incredibly hard to clip that amp, especially at 4 ohms. On the M1s I can "exhaust the headroom" in an instant, so I can see how a previous owner could have easily knocked out a tweeter. More than once....
.

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