Speaker damage due to amp malfuntion

[diy didi]

Vrystaat, ek is ook 'ou vrystaater. Ek sien baie drivers en tweeters wat blaas agv die amplifier self wat "gaan".
Nie 'n goeie idee om die relay te oorbrug nie!!! Baie keer is daar 'n protection circuit wat gekoppel is aan daai relay. MAW, daar is gewoonlik 'n rede hoekom die relay nie click nie.

[KatieandDad]

The Pass amps are virtually Bomb Proof, Its so unlikely thet output device failure will occur that you can dispence with relays in the output circuit.

Crap amps will fail. These amps will benefit from some sort of protection, but that wll cost in the fidelity stakes.

[indianajo]

I've lost two unmatchable tweeters from speakers with a tube amp with output transformers. That trashes the whole speaker pair if you have good ears. (I'm an amateur musician of some skill). It is not the cost of the speaker, it is the testing required to get good sound with the cheapo replacement speakers in stock at the distributor. The music instrument resale shop near me is full of speakers with new (cheap) woofers, and old amplifiers with shiny new output transistors. Make your own conclusions about the frequency of output transistor shortouts.
The first transistor amp I bought had a speaker protection capacitors between the output transistors and the speakers, so the 2 output transistor shortouts that occurred didn't hurt anything. Quite a fireball the last time it happened. (Now I have heatsink fans). But it will be a cold day in **** before I connect this split supply direct coupled transistor amp I'm working on now to an actual speaker. It came with the crowbar SCR traces completely burned off the PCB, and after I patched the PCB, burned the PCB again when I had bargain output transistors short out in it. The second blow up, the circuit breaker did not trip. It is an economy line PA amp, which means the only speaker protection is the SCR crowbar, and that is just to prevent speaker fires. I will change it to use the DC detection circuit that formerly tripped the SCR to open a power supply disconnect relay I install myself before I allow that $55 amp to be connected to my $1200 a pair (new) speakers. As Vibroking$ said, I'll use 2 pole relays on the power supplies. That means, I think, that significant voltage on the PS rails should allow the use of cheap copper contact relays instead of using the gold required for reliability after the Output Transistor's if you were running the output at 1 VAC. Also the relay contact is in the feedback loop if it is installed between power supply caps and the output transistors.

[danielwritesbac]

When I built my test speaker, I was unaware that an L-Pad on the tweeter could leave it vulnerable. After replacing the tweeter and scorched cables, I added a 4.7uF Nichicon ES series to the tweeter, right at the tweeter and for additional protection. The replacement tweeter is now many years old and has not failed.

[danielwritesbac]

Originally Posted by indianajo

I've lost two unmatchable tweeters. . .

Due to the qualities of today's dome tweeters, most of which will waste your time, may I suggest that you duke it out with an electrostatic instead. If one requires a deep voiced treble section, well that is a bit harder, but a midrange plus an electrostatic tweeter could be appreciable and not waste your time.

There's not really a substitute for a small collection of reasonable value inductor coils; however, Nichicon ES and ordinary Polyester caps can put in good service as tweeter caps, and those smaller 5w (and 3w) resistors are less inductive. So, the prospect of crossover adaption does cost something but not a terrible amount. The thing is, you will need options so as to choose the most favorable. And, price does not equate to performance.

I said all this hoping it wasn't a series crossover in your speaker. Although no doubt a finer quality, those are more reliant on driver matching. You'd end up running a parallel crossover atop that series crossover (makes DeVore crossover). But, if you've got a regular parallel crossover, well, get busy and fix your speaker already. This is not difficult, but it is slow--extremely slow with dome, so get some electrostatic types so you can have a good time.

[ric-paul]

I had a chipamp fail on me (possibly my own fault, I designed the PCB) and put 40Vdc on a 120W, 4ohm speaker. It didn't survive and now acts as a passive membrane covering its brother from cat-paws. (Isobaric looking config)

The same cat-paws that hacked into the surround of my HPM-60 speakers after I had the whole drivers replaced . I re-foamed the old drivers, but the glue used wasn't up to the task hence buying new drivers.

[carlmart]

I just made a similar comment on another topic here on output relays.

Solid-state relays and SCR protection have been reported by many as affecting the quality of the audio. I don't see how a common relay can add distortion, except if the circuit controlling it is not doing its job.

We are talking metal to metal contact here, and I think that is as less prone to distortion as it can get. We may argue on the metal quality or the plate quality, or how good that contact strength is, but I don't think that can be improved by any solid state relay where the interface is "sand" that does add distortion to the signal.

Am I wrong?

[DennyG]

Originally Posted by Vrystaat

Good evening all,
Just out of a matter of interest, how many of you people have had speaker damage due to an amp malfunctioning

Happened to me once upon a time. One channel of a Lecson AP1 went bad and took out a very good speaker!