dead diamond tweeter

[Cohibaman]

If DC is getting through, it would toast tweeters pretty quickly. I’d grab a meter and measure the DC voltage, AT THE TWEETER TERMINALS.

[AudioGremlin]

Originally Posted by Cohibaman

If DC is getting through, it would toast tweeters pretty quickly. I’d grab a meter and measure the DC voltage, AT THE TWEETER TERMINALS.

Not knowing the crossover network but usually a capacitor/s would block any DC from a suspect amplifier. As the OP says listening at higher levels then is the power amplifier output wholly sufficient to drive without any significant hf distortion, as thats what usually destroys tweeters. Just my 2p's worth, not a criticism

[W9TR]

A shorted series cap in the tweeter crossover will cause low frequencies to be sent to the tweeter, causing it to fail over time. This type of crossover capacitor failure may not manifest itself as something clearly audible.

An underpowered amp driven into clipping will also fry a tweeter but I would guess this would happen in both channels, not just one.

I would at least have the crossover in the suspect speaker tested. Any electronics tech with an LCR meter can do it.

[Art Vandelay]

Originally Posted by Jem666

Could it be a defect in the crossover, sending midrange and or bass frequenies to the tweeter. These signals have much more power and could easily overwhelm a tweeter to breaking point.

Unlikely but possible. The tweeter's high pass filter consists of a single 4.7uF polypropylene capacitor - with a whopping 1200V rating. Typically, these types of capacitors exhibit very low leakage, and being highly derated as is the case here it's unlikely to fail under any imaginable operating condition.

However, given that it's predominantly one channel that's failing it's still definitely worth testing the capacitor for leakage as well as capacitance. It might be that the cap is outside the stated 5% tolerance and hence out of spec. As an owner of 800D2's I've actually replaced my Mundorf 4.7uF SGO's with a matched pair that were 5% low in value, which errs on the safe side, and thus far no blown tweeters.

If I was designing the crossover myself I would add a parallel LCR network across the tweeter to precisely compensate for the vc resonance at 800Hz, because I suspect that this contributes to the unusually high failure rate of diamond tweeters.

[W9TR]

Thamks for posting the crossover schematic. I agree it is highly unlikely that C3 would fail but worth checking.

[andrewmr]

I don't have any idea of what it takes to move a crossover, but if it weren't too complicated I'd be tempted to move/swap the crossovers from the left and right speakers.

If down the road you blow the tweeter in the "other" speaker then I'd start looking into the crossover.

[edkoz]

Thanks for all the suggestions. Before I replace the tweeter I will take a look at the crossover and see if there is anything amiss. Hey,,, you never know!
Ed

[Dilettante]

I've owned the 800 D3 for over 3 yrs now and so far never had blown tweeter(s). At times I had driven them at pretty high levels.

[Art Vandelay]

Originally Posted by Dilettante

I've owned the 800 D3 for over 3 yrs now and so far never had blown tweeter(s). At times I had driven them at pretty high levels.

The latest D3 models don't appear to suffer from the problem. Perhaps the revised dome geometry has made the tweeters more robust in the D3's. Crossovers are essentially the same.

[Dilettante]

Originally Posted by Art Vandelay

The latest D3 models don't appear to suffer from the problem. Perhaps the revised dome geometry has made the tweeters more robust in the D3's. Crossovers are essentially the same.

I believe so. As long as you don't drive them with an AVR. lol. I have a friend here who's thinking to get the 802 D3 but he is going to drive them with his current $900 Marantz AV receiver (Marantz SR5011). He isn't willing to upgrade from his AVR. He currently has the Martin Logan ESL EM, which is the smallest entry level electrostats from Martin Logan. I told him even his current Martin Logan deserves much better than his AVR. And I told him if you he isn't willing to significantly upgrade from his $900 Marantz AV receiver don't even bother getting the 802 D3.