Hello Folks,
I am planning to do an active setup but I am confused on tweeter protection. I am trying to protect my tweeter from overload, dc, or pops.
I read up on capacitors and bulbs but I am unsure how to hook them up. Do I install them in series on the positive wire? Will the bulb go first, next capacitor, and finally tweeter? Or capacitor, bulb, and tweeter?
Specs
Tweeter Model: Vifa NE25VTT-04
4ohms| 80watts RMS | Freq Response 733-25,000 Hz
Amp Model: Rockford Fosgate Punch 400a4
RMS Power (4 ohms) 50W x 4
The high pass setting is configure for 2500 Hz Linkwitz-Riley 48db/oct. I am planning to use a Dayton Audio 33uF 250V Polypropylene Capacitor.
Anyone knows?
Thanks!
I am planning to do an active setup but I am confused on tweeter protection. I am trying to protect my tweeter from overload, dc, or pops.
I read up on capacitors and bulbs but I am unsure how to hook them up. Do I install them in series on the positive wire? Will the bulb go first, next capacitor, and finally tweeter? Or capacitor, bulb, and tweeter?
Specs
Tweeter Model: Vifa NE25VTT-04
4ohms| 80watts RMS | Freq Response 733-25,000 Hz
Amp Model: Rockford Fosgate Punch 400a4
RMS Power (4 ohms) 50W x 4
The high pass setting is configure for 2500 Hz Linkwitz-Riley 48db/oct. I am planning to use a Dayton Audio 33uF 250V Polypropylene Capacitor.
Anyone knows?
Thanks!
Unpleasant as it may be to hear, this is how speakers blow -
"It is never overpowered or underpowered amps that blow speakers, it is always the guy running the volume control.
The best protection for your tweeters is - don't be that guy.
The crossover network protects the tweeter. You seem to have a reasonably high crossover with steep slopes, so there shouldn't be any problem with the tweeter unless you are playing at insane volume levels.
The lamp will protect the tweeter, but it also steals dynamic range. Every time the voltage surges, part of it is lost across the lamp. That has something of a compression effect on the tweeter.
There are also thermal Circuit Breakers make specifically for audio applications. When the current and corresponding heat get too high, the Circuit Breakers trips and opens the circuit. When it cools, it closes again, so it never needs to be reset.
Fuses are also possible, but if the fuse blows, then the speaker is down until you get around to replacing the fuse.
With both these, we have the problem of determining at what current level we want to set the breaker or fuse. Set too low and it is blowing or tripping all the time. Set too high and it doesn't protect the speaker.
However, few speaker have light bulbs, fuses, or circuit breakers. Most rely on the user to use common sense and reasonable restraint when using the speakers.
There are two potential problems with tweeter and actually with any driver -
1.) Excess Excursion - If the crossover is too low or the slope is too shallow, you can cause physical damage to the driver.
2.) Excess Heat - Which is cause be excess current for an excessive amount of time. This can literally melt the voice coils.
Both are caused by poor design and/or inappropriate use of the speakers, both are user errors.
Given the tweeter and crossover you describe, I don't see much of a problem.
Steve/bluewizard
"It is never overpowered or underpowered amps that blow speakers, it is always the guy running the volume control.
The best protection for your tweeters is - don't be that guy.
The crossover network protects the tweeter. You seem to have a reasonably high crossover with steep slopes, so there shouldn't be any problem with the tweeter unless you are playing at insane volume levels.
The lamp will protect the tweeter, but it also steals dynamic range. Every time the voltage surges, part of it is lost across the lamp. That has something of a compression effect on the tweeter.
There are also thermal Circuit Breakers make specifically for audio applications. When the current and corresponding heat get too high, the Circuit Breakers trips and opens the circuit. When it cools, it closes again, so it never needs to be reset.
Fuses are also possible, but if the fuse blows, then the speaker is down until you get around to replacing the fuse.
With both these, we have the problem of determining at what current level we want to set the breaker or fuse. Set too low and it is blowing or tripping all the time. Set too high and it doesn't protect the speaker.
However, few speaker have light bulbs, fuses, or circuit breakers. Most rely on the user to use common sense and reasonable restraint when using the speakers.
There are two potential problems with tweeter and actually with any driver -
1.) Excess Excursion - If the crossover is too low or the slope is too shallow, you can cause physical damage to the driver.
2.) Excess Heat - Which is cause be excess current for an excessive amount of time. This can literally melt the voice coils.
Both are caused by poor design and/or inappropriate use of the speakers, both are user errors.
Given the tweeter and crossover you describe, I don't see much of a problem.
Steve/bluewizard
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With that slope, yes, 15 uf should be fine, but in case you want to experiment later with lower crossovers at shallower slopes why not go to at least 24 uf, if not in the 30s?
I agree with Steve, you shouldn't need caps. I am not that guy with the volume control and I cross my drivers appropriately. I am, however, they guy who managed to blow a rail fuse with an errant voltmeter probe at the cost of my tweeter. I don't know if the cap would have saved my tweeter from a 65V transient, but at least I know it won't see any DC no matter what I drop into my amp. Again, user errors, but I feel better with a cap.
I agree with Steve, you shouldn't need caps. I am not that guy with the volume control and I cross my drivers appropriately. I am, however, they guy who managed to blow a rail fuse with an errant voltmeter probe at the cost of my tweeter. I don't know if the cap would have saved my tweeter from a 65V transient, but at least I know it won't see any DC no matter what I drop into my amp. Again, user errors, but I feel better with a cap.
A lot is being said, with good or no practical use/information for you QikoCB7, besides what you need to evaluate in a good proposition. In your case (you are not a designer in the hard sense) some pros have their professional or market ideas (manufacturers), either they use it for PA or to protect their warranties with their equipment/material misuse (read "stupid" proof and accidents). That require a lot of work to calibrate i.e., a PTC for let's say Hi Fi or for a Eminence CD, sometimes with a series of blown drivers in the factory floor. Others use a Compressor/Limiter type of pro audio/amps equipment. No matter what you are using or designing for, in your case, from post #1, what I know (and I don't have experience with active/xover speaker systems) I also was told is that you should use that cap whatever the situation, for protection of LF, a mistake that can be very expensive for not having it or if you leave to chance 
I have active system too and I have blown two ribbon tweeters - accidents happen! Just disconnecting/connecting pre-poweramp cables with power on... switching on/off preamp when poweramp is on...
I have a 6.8uF cap now because I didn,t have anything else available. It affects response curve yes, but that is not a problem with minidsp xo/eq. When I have the surge, I,ll buy some 20uF caps or like that. They don't come with quality, but they are not in the passband anyway then
I have a 6.8uF cap now because I didn,t have anything else available. It affects response curve yes, but that is not a problem with minidsp xo/eq. When I have the surge, I,ll buy some 20uF caps or like that. They don't come with quality, but they are not in the passband anyway then
I mostly agree with that Steve except for the underpowered amp bit. Yes it is excessive current that causes voice coils to blow. One of the ways that you get that excessive current is driving the amp into clipping. You are more likely to drive an underpowered amp into clipping than an overpowered one. Of course if the overpowered one is turned up past the capabilities of the tweeter that will also cause the tweeter to blow (even if clipping didn't occur). So yes the result is the same, ie some one turned the volume past where they should have
I've blown a lot of tweeters (and even some midranges) early on. Back in the days when people used to ask me to bring my amp and speakers to parties.
There was a line on the amp's volume control and everyone was told don't turn it up above this line, but invariably someone did. I always thought that the speakers just couldn't handle the power above that point and that some day when I could afford it I'd buy some high powered tweeters. It wasn't the case, I found years later when I had a scope that that line was the point where the amp would start clipping if fed a 2V sine wave. I eventually put some polyswitches in and never blew another driver
Tony.
Spot on Wintermute, it's those under powered amps that cause the trouble. People also tend forget that tweeters can only handle about 5 watts. I don't have experience with active speakers but the slope you're using should surely be enough protection, my 12 dB slopes on my passives have always been good enough because if you drive the system too hard the woofers distort way before the tweeters take strain.
I should add, that if the amp is very underpowered it won't be a problem. That is if the speakers can handle 20W and you drive a 1W amp into severe clipping it still won't be able to provide enough power to melt the voice coil. If however you use a 15W amp with the same speaker and drive it into severe clipping you will almost certainly blow the tweeters (because a clipped signal delivers more power than a pure sine wave does).
Tony.
Tony.
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Overpowered and Underpowered amp -
Well ... what constitutes underpowered? People who make the claim that Underpowered amps are more dangerous than overpowered amps never quite define what qualifies as underpowered.
And I still say overpowered or underpowered, the problem is the guy running the volume control.
For many years (decades really), I had a 45w/ch amp, is that underpowered, because it sounded fine and drove several sets of large old-school speakers (though not at the same time)? But I understood the limits of my equipment and used the equipment accordingly. For the record, I never blew a single driver in something like 40 years of serious music listening.
As to the system under consideration, are these active speaker with amps and crossovers built-in, or, as I suspect, are the raw speakers with external amps and external crossovers?
If everything is build in, you have a lot more control. Values can be fixed, the appropriate power amps can be determined. However, if this is using external amps and external crossovers, then you are at the mercy of your idiot friends and your (probably misplaced) trust that they will not screw with your equipment.
Even is a HiFi system with external amps and crossovers, you are somewhat at the mercy of those same idiot friends. If you can keep an iron fist on things and keep people away, then perhaps you don't have to worry about protection. But, if you throw a party, you throw it for others; you play host and guard the equipment with your life.
The idea of using a 12db(or 18dB) active crossover combined with an internal 6dB Capacitive crossover might be an idea to consider. But I'm wondering if the 24dB isn't fixed in the external crossover. If so, then that idea might not work.
If I understand the concept correctly, the capacitor is large enough that the functional crossover is WAY BELOW the actual working crossover, as such, when everything is working right, no real frequencies should be fed to the capacitor. That is, functionally, the capacitor is a short circuit to any signal it receives. However, should a spike or DC be present, it would block that.
Just a thought.
Steve/bluewizard
Well ... what constitutes underpowered? People who make the claim that Underpowered amps are more dangerous than overpowered amps never quite define what qualifies as underpowered.
And I still say overpowered or underpowered, the problem is the guy running the volume control.
For many years (decades really), I had a 45w/ch amp, is that underpowered, because it sounded fine and drove several sets of large old-school speakers (though not at the same time)? But I understood the limits of my equipment and used the equipment accordingly. For the record, I never blew a single driver in something like 40 years of serious music listening.
As to the system under consideration, are these active speaker with amps and crossovers built-in, or, as I suspect, are the raw speakers with external amps and external crossovers?
If everything is build in, you have a lot more control. Values can be fixed, the appropriate power amps can be determined. However, if this is using external amps and external crossovers, then you are at the mercy of your idiot friends and your (probably misplaced) trust that they will not screw with your equipment.
Even is a HiFi system with external amps and crossovers, you are somewhat at the mercy of those same idiot friends. If you can keep an iron fist on things and keep people away, then perhaps you don't have to worry about protection. But, if you throw a party, you throw it for others; you play host and guard the equipment with your life.
The idea of using a 12db(or 18dB) active crossover combined with an internal 6dB Capacitive crossover might be an idea to consider. But I'm wondering if the 24dB isn't fixed in the external crossover. If so, then that idea might not work.
If I understand the concept correctly, the capacitor is large enough that the functional crossover is WAY BELOW the actual working crossover, as such, when everything is working right, no real frequencies should be fed to the capacitor. That is, functionally, the capacitor is a short circuit to any signal it receives. However, should a spike or DC be present, it would block that.
Just a thought.
Steve/bluewizard
As the capacitor is in series with the tweeter all the signal passes though it. Using a bigger value and therefore shifting the crossover frequency lower doesn't change this. The same 90 degree phase shift happens, it's just that it all happens below the passband.
It's the same as a coupling cap in an amp etc. where a large value is used so there's no low frequency rolloff. Well there is but it happens below the passband. Signal, all of it, still has to go though it so the quality of the cap matters. Otherwise it wouldn't matter what cap you used, quality wise as long as it was a really big one.
I'm currently using a 3rd order BW filter for the tweeters, comprising a passive 1st order (a cap) and an active 2nd order (DSP) both tuned to the same frequency to achieve maximum cutoff.
It's the same as a coupling cap in an amp etc. where a large value is used so there's no low frequency rolloff. Well there is but it happens below the passband. Signal, all of it, still has to go though it so the quality of the cap matters. Otherwise it wouldn't matter what cap you used, quality wise as long as it was a really big one.
I'm currently using a 3rd order BW filter for the tweeters, comprising a passive 1st order (a cap) and an active 2nd order (DSP) both tuned to the same frequency to achieve maximum cutoff.
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