it would not.
you have to be sure of what you're doing.
I see it as a protection against amplifier damage (overloading with too much signal IE; gain set too high)
also, big DC offset will blow the fuse before the tweeter coil blow shall the amplifier had damage.
this cover enough for me to feel comfortable.
Why the film cap in parallel? doesn't this just add to the total capacitance?
So you are saying that quality doesn't matter if well out of the crossover freq, is that right?
Sorry about that. You're quite correct and in that case I would use a cap as cheap insurance but I truly can't remember the last time I had a power amp fail.
I need to read more carefully.
G²
The smaller cap is to prevent the large electrolytic's ESR from becoming and issue at higher frequencies, at the top of the tweeter's output range.
I considered many approaches but none seemed as sure to protect against (even very small) amounts of DC, except a servo. All others will not know the difference between AC and DC.
I considered many approaches but none seemed as sure to protect against (even very small) amounts of DC, except a servo. All others will not know the difference between AC and DC.
Cool thread, I use a cap, 2.2UF 700v Supreme on a compression driver (PSE 144 Horn) simply as idiot protection in case of a poor choice of poor choice of mouse click with the DSP.
Something I have done since the early days with Car Audio saves problems with Customers cooking their tweeters after playing about in DSP settings.
Other than that wouldn't use anything unless unfamiliar with the DSP although in some cases seemed to aid EQ at the crossover transition, where some drivers can get ragged if pushed
Something I have done since the early days with Car Audio saves problems with Customers cooking their tweeters after playing about in DSP settings.
Other than that wouldn't use anything unless unfamiliar with the DSP although in some cases seemed to aid EQ at the crossover transition, where some drivers can get ragged if pushed
Depends on usage. A solid film cap as part of the overall tweeter filter will see very little power and be essentially neutral but materially protect against miswiring and turn on/off thumps. Amp failure needs management unto itself.
The rest of the discussion has unfortunately gone off the rails. :/
Just to be thorough, if you have the datasheet/can import the impedance curve of the tweeter in use, then any number of freeware xover programs (or heck RC filter calculators if the impedance is well behaved in the passband of the filter) will be able to calculate the necessary capacitor. Want an LR4 target filter at 4 kHz? Aim for a 1st order passive filter (aka a series cap) of ~3.8 kHz, which would more or less be a 6.8 uF capacitor for a 6 ohm tweeter load.
Then dial in your digital crossover to cover the rest of the LR4 filter.
I don't use a protection cap with my active speakers and haven't done now for many years. Of course you're going to want your amplifiers to have DC fault protection and turn on thump elimination.
Ironically the one time I actually lost a tweeter was when I did have a protection cap in place...not that the cap caused the tweeter to fail.
I can appreciate that you don't want to connect a Be dome directly to the amplifiers output though.
Ironically the one time I actually lost a tweeter was when I did have a protection cap in place...not that the cap caused the tweeter to fail.
I can appreciate that you don't want to connect a Be dome directly to the amplifiers output though.
The lack of damping factor from using "protection" capacitors caused multiple failures to Dave Rat's TAD 4001 Be drivers which often shattered when testing his "Rat Trap's" adjacent components with high level pink noise. Eliminating the capacitors eliminated that problem..
After 34 + years, "using", it's been about six years since I ditched "protection" capacitors to clean up sonic and phase performance, though I'd still use them with amps that have no DC protection as you mention.
Then again, I don't like loosing woofers either, so have eliminated amps that have no DC protection...
How do SETs behave in regards to DC? Can generalizations be made for this type of amps?
Single Ended Triode amps are a subset of tube/valve amps.
Generally, most tube amps audio outputs are transformer coupled, and transformers don't pass DC.
There are also some transformerless tube amps, some outputs directly coupled with a DC offset control, others capacitively coupled.
Some tweeters voice coils can melt with very little continuous DC voltage, I'd be inclined to use a "protection cap" if the amp was directly coupled with a DC offset control.
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Reviving this old thread; assuming the amp in question has DC protection and very low DC offset, would your conclusion be any different if the tweeter was an Apogee ribbon ?
A timely revival of this thread. My tweeter is an AMT, not so different from a ribbon. I'm driving a Beyma TPL protected with cheap 37uF cap and driven by a 45-type SET which shouldn't output DC current per above posts), and been thinking about trying without the cap or replace with good quality cap. One concern is the noise (pop) when digital sampling rate changes, and the other is DC current. How can I measure DC current output by the SET?
That's not just a lack of damping factor, that's surely a resonance between the tweeter's inductance or mechanical impedance and the capacitor. A resistor across the tweeter (and/or in series with the cap) would surely help a lot, and a (low power) frequency sweep with and without a resistor would show the problem. Now that I read about this, I wouldn't want to use a capacitor by itself without something to damp such a resonance.
Most volt/ohm meters can be used to measure DC current. Check how in the manual, should be something like this:
https://www.electricaltechnology.org/2021/06/measure-current-using-multimeter.html
I don't know the power rating of your Apogee ribbon, or what you consider "very low" DC offset.
As an example, one side of a Hafler DH-200 amp (200w@8ohms) had voltage on one channel that slowly grew from a small fraction of a volt to 5 volts over the course of 20 years.
5 volts into a “100watt 8ohm” Tannoy PBM 6.5 woofer's DC resistance of around 4 ohms, just 6 watts, was enough to cause the woofer's voice coil to burn, as the DC held the voice coil in a fixed position, allowing little cooling as the speaker sat powered, but idle.
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