This question is aimed to TRUE Elec Engineers, not fuse or wire directionality believers.

Back to back MOSFETs suggested here will work but they need a 10V floating voltage source or some photovoltaic coupler to a DC detection circuit. These have time delays. The tweeter should be able to handle a short single spike. Average power will be low.
Power requirements for a tweeter is very low so driving from a 100V source kinda don't make sense. Bi amping using low power amp for tweeters does.
Tube amps have transformers isolating from DC and typically sound good.
A normal mechanical relay has a delay time as well, like 8 - 20 ms  so some energy will reach the tweeter. I would think there is a cap in series with the tweeter, that will block DC. A small relay could be placed after the cap maybe even a reed relay.
As some have posted here, a fast crowbar circuit is used to blow a fuse where extreme protection is needed.
If a power amp has glitches that puts DC on the output it should be fixed or else replaced. 
Additionally, HF energy can pass the speaker high-pass filter and some protection for the tweeter is needed here.  I have burned up tweeters with amp stability problems. Perhaps limit the max frequency the tweeter is exposed to. 
DC on the output of audio amps is a problem that was solved 40 years ago, as I can recall. This really should not be an issue.

@rodman99999
I'm not saying the tweeter was not damaged. I am saying it was damaged for a different reason than the capacitor not doing what caps do (which is block DC).

The premise that I’ve been testing, is that NO DC voltage would get past a non-polarized capacitor. At least, that’s what’s been proffered in this thread.

 You don't need to put a tweeter on the cap. Just put a resistor. Let it sit there for a while (the bigger the value, the longer it has to sit) and then measure the DC voltage across the resistor. There will not be any- because the cap is charged. This assumes a working capacitor of course.


Capacitors, especially electrolytics, have a little bit in common with a battery. They can be charged up and hold a charge but unlike a battery, the time it takes is very dependent on the resistance in series.


The tweeter was damaged because there was significant inrush current to charge that particular cap. Once charged no more current flows. That is how an exponential charging curve works. 

@cakyol Has any of you ACTUALLY worked with and recommend a SSR which does not introduce any audible distortion on the speaker line and which can operate with a large range of trigger voltages (12 - 48 VDC, may need to have on board voltage regulator for this range). I am building a speaker DC protector and do not want to use electro mechanical relays becoz of DC arcing and contact erosion issues. It needs to be capable of switching up to 15 amps at about 100 volts.Only TRUE engineers reply please.Thanks

Please begin a question without an abbreviation of the most important item.

Solid State relays typically employ SCRs which will have a dead zone at the zero crossing. Try to measure it Its large and will cause a lot of distortion. Crossover distortion is the worst. Rail fuses are your best bet. They are in the feedback loop, and do no harm and no zero crossing.

Other than that a good relay is useful though rail fuses, not speaker fuses, are far better.

BGW used a parallel clamp when DC was detected. The front panel circuit breaker/power switch then opened and all was well. Great solution if your devices can pull the breaker.

Ok, I bought a pair of these from down under:

https://holtonprecisionaudio.com/collections/diy-audio-products/products/audio-solid-state-relay-hpa...

I will post on this thread later when I have time to add them to my circuits.

Thanks

1) "Finally, although it’s more of an academic point than one having practical significance, if a large DC voltage is suddenly applied to a capacitor, and a large current briefly flows corresponding to C(dv/dt), the nearly instantaneous change in voltage means that spectral components are present at non-zero frequencies, at and near that instant. Which by definition means that the voltage is not DC, at and near that instant." 2) "The tweeter was damaged because there was significant inrush current to charge that particular cap. Once charged no more current flows. That is how an exponential charging curve works." That explains why transients both blew the tweeter and caused the pops from the woofer, when the discharged capacitor and battery were reconnected. Whatever was passed through the nonpolarized capacitor ("spectral components"/DCV/Dark Energy?), it blew the tweeter and created sound(however briefly) through the woofer. Again, I wish I had a scope, with which to better record the duration and amplitude of the spike.   Apparently, no one out there with a scope, cares enough to perform such a simple experiment, to either confirm or disprove my results.