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Best DC blocking, AC transparent capacitor for tweeter protection (not crossover)

mike7877

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The capacitor is especially important because it will be the only thing between the tweeter and amplifier. I'm in the final stages of acquiring everything necessary for my passive to active speaker conversion - exciting!

Before recommendations, you need to know the capacitor's performance is actually even more critical than you might be assuming. How?
The tweeter itself, is exceptional. Beyond exceptional, actually - and not only that - so's the amplifier.
And the amplifier's source? It's even better, still

I really don't think it's wise to just throw a nice low-ESR 50uf bipolar electrolytic in series with my beautiful tweeter and call it a day... I'd like to make sure that the cap I use doesn't, I'll borrow the FCC's annoying language here... "cause undesired operation".

I can only describe, with certainty, the end result I want:
I want the cap I use to prevent accidentally generated DC from cooking the coil of my tweeter (if it's generated at some point), and I want minimal added HD and IMD to the signal. I don't want the capacitor's impedance to change (appreciably) through the tweeter's operating spectrum

I've been reading some about caps, and have a new respect for them - capacitors are their own special thing, you could literally become a specialist in capacitors, the different types, how each behaves, how their different behaviours make them good for specific things, which types of caps you should use in what situations (to not waste money or to get maximum performance or to minimize associated component count, or however you might want to optimize something, caps are crazy.

I want the cap to be as transparent as possible for a target of $50USD. If the best option is $30, I don't need to waste $20 on something inferior, and if $60 gets something significantly better than $50, I'll spend the extra 10.
 
The capacitor is especially important because it will be the only thing between the tweeter and amplifier. I'm in the final stages of acquiring everything necessary for my passive to active speaker conversion - exciting!

Before recommendations, you need to know the capacitor's performance is actually even more critical than you might be assuming. How?
The tweeter itself, is exceptional. Beyond exceptional, actually - and not only that - so's the amplifier.
And the amplifier's source? It's even better, still

I really don't think it's wise to just throw a nice low-ESR 50uf bipolar electrolytic in series with my beautiful tweeter and call it a day... I'd like to make sure that the cap I use doesn't, I'll borrow the FCC's annoying language here... "cause undesired operation".

I can only describe, with certainty, the end result I want:
I want the cap I use to prevent accidentally generated DC from cooking the coil of my tweeter (if it's generated at some point), and I want minimal added HD and IMD to the signal. I don't want the capacitor's impedance to change (appreciably) through the tweeter's operating spectrum

I've been reading some about caps, and have a new respect for them - capacitors are their own special thing, you could literally become a specialist in capacitors, the different types, how each behaves, how their different behaviours make them good for specific things, which types of caps you should use in what situations (to not waste money or to get maximum performance or to minimize associated component count, or however you might want to optimize something, caps are crazy.

I want the cap to be as transparent as possible for a target of $50USD. If the best option is $30, I don't need to waste $20 on something inferior, and if $60 gets something significantly better than $50, I'll spend the extra 10.
Any reasonable metal film capacitor is going to work.
Panasonic, for instance:
WIMA are nice too.
These all work with regular amps and tweeters.
Or one of the Dayton Audio caps.
None of these is going to have measurable distortion compared to whatever tweeter you may have or 'cause undesirable operation', and you won't find any boutique capacitors that exceed the performance. All of them block DC, it's fundamentally what a capacitor does.
I think fishing for a 'transparent cap' is a mistake. Get one of the correct capacitance value and voltage rating. Your aversion to electrolytic is misplaced. Also note that the DC blocking capacitor on a tweeter is about the least critical application of all time, tolerance doesn't even matter.

Have you considered building the active tweeter filter using the blocking cap as one of the filter poles? It is a very good way to implement. Allows a much smaller value than 50uF. Has advantages.
 
I've been reading some about caps, and have a new respect for them - capacitors are their own special thing, you could literally become a specialist in capacitors, the different types, how each behaves, how their different behaviours make them good for specific things, which types of caps you should use in what situations (to not waste money or to get maximum performance or to minimize associated component count, or however you might want to optimize something, caps are crazy.
Only in audiophile legend. In reality, for best performance use an absolutely non-exotic mass-produced, non-audiophile polypropylene foil cap. Something from WIMA or Panasonic or Vishay or other major producer.

Avoid Teflon/PTFE like the plague. Ditto any "audiophile" brand.
 
I've built a FEW tweeter protection circuits and you can use a single cap if you're willing to buy a tweeter from time to time. I gave up on single-component
6db first order a LONG time ago when I purchased my first 300.00 tweeter. They are just too sloppy. Most of the tweeters I use require at least 18db or 3
components for reasonable protection and not having a tweeter working well below what I want them cut off at.

24db is a lot better by most speaker builder's standards. 3-4 components and even a fuse if your using a cheap amp. When I say cheap I mean CHEAP.
If an amp pops turning it on/off it's a good bet you will buy a tweeter before it's all said and done. You can also ADD a frequency collection cap or it is
sometimes called a bypass cap. I like WiMa 2% in that position, if you're using a good cap with a FC cap. It doesn't have to be expensive just accurate. I like
Teflons/WiMa. TrT Teflons/WiMa or Mundorf Blue Teflons/WiMa. I'm a point to point kind of guy too. Not to hot on boards in passive XOs either.

I mechanically join the wire to the driver terminal too. unless I'm messing with XO points. BUT I haven't had to do that for 25 years. I don't solder the
subs or the bass drivers but everything else usually get a good cleaning, a good mechanical joint and good silver solder if the driver has good spades
heatsinked in. I use a LOT of ribbons so you do have to be careful soldering at the terminal ends of the diaphragms/ribbons.
If you are going to use butt connectors make sure you use a dimple tool that pressure welds the two together. DON'T buy the cheapos made from aluminum
Buy good tinned copper, or copper connections and cover the connection with a contact protector and contact enhancers.

I've repaired 200 GREEN connections on tweeters, if I've repaired one. Infinity used to be horrible for using that GD first-generation Monster cable. I hate
that stuff. Belden SC silver clad is one of the best for mids and highs makeup wire. I've stripped a LOT of Monster cable out of the old RS series Infinities
and NEVER one time with Belden SC. # 18 or 20 is perfect for 300+ watts to mids or mid/tweeter array. PTFE SC Belden, it does make a big difference in
longevity. But you can use bailing wire if you listen to some people. I usually have to repair their work at some point. The cloth hanger crowd. LOL

You're good if the butt connector pliers have the black/orange handles. That is an identifier on 90% of ALL union job sites. They have to make a dimple or
you can bet on a loose connection over a period of time, if there is any kind of sub/bass in the cabinet or close to your cabinets.

Regards
 
You already queried about this and received some good replies. Why are you starting another thread?

Dave Reite.
 
The capacitor is especially important because it will be the only thing between the tweeter and amplifier. I'm in the final stages of acquiring everything necessary for my passive to active speaker conversion - exciting!

Before recommendations, you need to know the capacitor's performance is actually even more critical than you might be assuming. How?
The tweeter itself, is exceptional. Beyond exceptional, actually - and not only that - so's the amplifier.
And the amplifier's source? It's even better, still

I really don't think it's wise to just throw a nice low-ESR 50uf bipolar electrolytic in series with my beautiful tweeter and call it a day... I'd like to make sure that the cap I use doesn't, I'll borrow the FCC's annoying language here... "cause undesired operation".

I can only describe, with certainty, the end result I want:
I want the cap I use to prevent accidentally generated DC from cooking the coil of my tweeter (if it's generated at some point), and I want minimal added HD and IMD to the signal. I don't want the capacitor's impedance to change (appreciably) through the tweeter's operating spectrum

I've been reading some about caps, and have a new respect for them - capacitors are their own special thing, you could literally become a specialist in capacitors, the different types, how each behaves, how their different behaviours make them good for specific things, which types of caps you should use in what situations (to not waste money or to get maximum performance or to minimize associated component count, or however you might want to optimize something, caps are crazy.

I want the cap to be as transparent as possible for a target of $50USD. If the best option is $30, I don't need to waste $20 on something inferior, and if $60 gets something significantly better than $50, I'll spend the extra 10.
The caps will be acting as coupling caps. Any half decent bipolar cap will do for that reason. No reason for paralleling a smaller value either.
The reason is that the capacitor does not work as a crossover filter and will work perfectly for the filtered band.

Of course you can make it as expensive as you want. That will help for FOMO for sure but you should remember .. that is just FOMO and not a technical issue.
 
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Any reasonable metal film capacitor is going to work.
Panasonic, for instance:
WIMA are nice too.
These all work with regular amps and tweeters.
Or one of the Dayton Audio caps.
None of these is going to have measurable distortion compared to whatever tweeter you may have or 'cause undesirable operation', and you won't find any boutique capacitors that exceed the performance. All of them block DC, it's fundamentally what a capacitor does.
I think fishing for a 'transparent cap' is a mistake. Get one of the correct capacitance value and voltage rating. Your aversion to electrolytic is misplaced. Also note that the DC blocking capacitor on a tweeter is about the least critical application of all time, tolerance doesn't even matter.

Have you considered building the active tweeter filter using the blocking cap as one of the filter poles? It is a very good way to implement. Allows a much smaller value than 50uF. Has advantages.
Only in audiophile legend. In reality, for best performance use an absolutely non-exotic mass-produced, non-audiophile polypropylene foil cap. Something from WIMA or Panasonic or Vishay or other major producer.

Avoid Teflon/PTFE like the plague. Ditto any "audiophile" brand.

Are there types or editions of electrolytics which are known to keep their ESR to at least within 30% of what it is at 1kHz, over the entire audible spectrum, or at least from 120Hz to 10kHz? There just aren't charts for ESR, often just 1kHz, 10kHz, or just 1kHz, or 1kHz and 120Hz, or just 120Hz. or 10kHz or 100kHz (.......you get the idea. I was trying to learn about the various characteristics of the slightly different caps by observing their behaviour in datasheets, but what they give you is minimal, even the expensive and specialty places!! They definitely aren't all the same... I don't want to have to order 10 different flavours and spend 4 hours making sure one of them fits specification, then wasting time individually packaging and returning the failures lol
 
Have you considered building the active tweeter filter using the blocking cap as one of the filter poles? It is a very good way to implement. Allows a much smaller value than 50uF. Has advantages.
I did consider using a first order cap instead, but the size it'd need to be to avoid the impedance hump, I don't know....
The tweeter reaches 24ohms (from 5.4) at somewhere just below 1kHz (it's wide, too, - still about 10dB at 1.8kHz and 450... (actually, it might be worse)

It'd be a very involved and not cheap process, probably. I'm trying to not do any equalization above 160Hz, too (only modification planned is a +12dB low shelf centered at @55Hz, Q of 1.07 (55Hz is the speaker's -6dB point in its sealed box, its Q is also just above 1 - I'm going to do better for the ringing eventually, but that's software customization that can be done at any time but now lol)
 
You already queried about this and received some good replies. Why are you starting another thread?

Dave Reite.

Actually, that's different - I was going to do a first order crossover in addition to active, but that's not the plan anymore! This cap is for a different purpose.
I did forget about that thread, though. I'll read it, thanks :)
 
I don't want to have to order 10 different flavours and spend 4 hours making sure one of them fits specification, then wasting time individually packaging and returning the failures lol
The ESR of a foil-film polypropylene cap will be low and highly stable.
 
The caps will be acting as coupling caps. Any half decent bipolar cap will do for that reason. No reason for paralleling a smaller value either.
The reason is that the capacitor does not work as a crossover filter and will work perfectly for the filtered band.

Of course you can make it as expensive as you want. That will help for FOMO for sure but you should remember .. that is just FOMO and not a technical issue.
Are you sure that they don't start behaving weirdly when they age, or at different frequencies? It could be pretty catastrophic with the 24 ohm peak at 900something Hz which spans over two octaves before returning to single digits (which is still double 5.4....)
The ESR of a foil-film polypropylene cap will be low and highly stable.
I think I have a couple of 50V 10 or 20uf'ers (lol "you f'er!")
I bought them 5 years ago to spruce up some older speakers I never ended up using because the process was a failure ESR was MUCH too low...
I left the originals taped to the back of the speakers, so I can either salvage and restore, or rip open, rip off, and discard.
The speakers aren't that good and spring cleaning's coming

Free is the best! I forget what I paid for them new, but I think it was $25 - that sound about right? They're like 3/8" deep by 1/14" wide, by 7/8" tall, maybe 10-20% bigger
edit: I think it was "metalized film"
define: metalized film - foil....?
maybe it's even better
 
I did consider using a first order cap instead, but the size it'd need to be to avoid the impedance hump, I don't know....
The tweeter reaches 24ohms (from 5.4) at somewhere just below 1kHz (it's wide, too, - still about 10dB at 1.8kHz and 450... (actually, it might be worse)

It'd be a very involved and not cheap process, probably. I'm trying to not do any equalization above 160Hz, too (only modification planned is a +12dB low shelf centered at @55Hz, Q of 1.07 (55Hz is the speaker's -6dB point in its sealed box, its Q is also just above 1 - I'm going to do better for the ringing eventually, but that's software customization that can be done at any time but now lol)
You are wrestling with datasheets. You should be measuring and modeling. The ESR among polypropylene metal film capacitors on the order of milli-Ohms, and negligible in any application with your tweeter, and your proposed application (DC blocking capacitor) is about the least critical.

You are being circumspect with the data you do have.
24 ohm peak at 900something Hz which spans over two octaves before returning to single digits (which is still double 5.4....)
I really can't make sense of this. Actually quite confusing.
The tweeter reaches 24ohms (from 5.4) at somewhere just below 1kHz (it's wide, too, - still about 10dB at 1.8kHz and 450... (actually, it might be worse)
Even more confusing.
The tweeter itself, is exceptional. Beyond exceptional, actually - and not only that - so's the amplifier.
And the amplifier's source? It's even better, still
This wasn't useful either.

Just give some simple data, like the drivers and measurements. Do you have some actual data, perhaps in VituixCAD? Or is this a datasheet exercise? Seems like you could use the help.
 
Are you sure that they don't start behaving weirdly when they age, or at different frequencies? It could be pretty catastrophic with the 24 ohm peak at 900something Hz which spans over two octaves before returning to single digits (which is still double 5.4....)

I think I have a couple of 50V 10 or 20uf'ers (lol "you f'er!")
I bought them 5 years ago to spruce up some older speakers I never ended up using because the process was a failure ESR was MUCH too low...
I left the originals taped to the back of the speakers, so I can either salvage and restore, or rip open, rip off, and discard.
The speakers aren't that good and spring cleaning's coming

Free is the best! I forget what I paid for them new, but I think it was $25 - that sound about right? They're like 3/8" deep by 1/14" wide, by 7/8" tall, maybe 10-20% bigger
edit: I think it was "metalized film"
define: metalized film - foil....?
maybe it's even better

You're making a mountain out of a mole hill. First thing you need to do is learn how to calculate the xover point for simple crossovers. Then just go by a 50uF electrolytic cap, like a motor run cap.

Problem solved, nothing to worry about for 20 years
 
I think it was "metalized film"
Metallized film is like the Mylar party balloons, a vapor-deposited metal (usually aluminum) coating. They're a step down from foil/film in terms of current handling, and they're usually smaller and less expensive. Foil/film is theoretically better by a small margin, but honestly not much to worry about unless you think you'll be driving a LOT of power into the tweeter.
 
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