Just thinking out loud - I know what can happen with a cone speaker with something going wrong with upstream equipment (DC Offset, turn on/off thump, oscillation, etc) - the voice coil just melts, and your left with a locked / unmovable cone...
But are planar (Magnepan), ESL (Acoustat) or ribbons (Apogees) better able to handle such issues? I see there is a much larger air gap, and should help with these upstream amp / preamp issues, no?
I ask as I wonder if I should be worried about not having any amp protection on any of my amp project builds on my speakers...
But are planar (Magnepan), ESL (Acoustat) or ribbons (Apogees) better able to handle such issues? I see there is a much larger air gap, and should help with these upstream amp / preamp issues, no?
I ask as I wonder if I should be worried about not having any amp protection on any of my amp project builds on my speakers...
In general, yes, better immunity.
Except for the obvious exception of loosely suspended ribbon drivers....Maggie tweeters, Apogee tweeters, etc. Big transients and/or DC deflections would not be good for those. Generally, they will have a series capacitor to help out, but it's not 100% effective.
Dave.
Except for the obvious exception of loosely suspended ribbon drivers....Maggie tweeters, Apogee tweeters, etc. Big transients and/or DC deflections would not be good for those. Generally, they will have a series capacitor to help out, but it's not 100% effective.
Dave.
Ummm... DC will have no effect on any tweeter (ribbon or not) that has a passive HP crossover in front of it because the DC will be blocked by the cap.
Thumps, technically are not DC. Very LF AC is what that is.
ESLs are generally run using a step up transformer, so no DC can pass.
Planars and true ribbons vary depending on if they use a HP filter and/or a transformer. A true ribbon or a HF planar will often use both. LF planars, like an Apogee speaker will not have any DC blocking for the LF section. They are subject to damage due to high current DC passing through the diaphragm.
Oscillation will not be something that any of the above will be able to avoid damage. HF oscillation can and will damage almost any speaker. ESLs being least susceptible to this type of damage. The main reason being that most step up xfmrs will exhibit poor throughput (frequency response) at frequencies that are typical of parasitic oscillations. Also there is no element to overheat since the transfer is electrostatic.
Any speaker section with a LP filter (or bandpass) will attenuate HF parasitic oscillations substantially, so little chance of damage in this area.
Most "amp protection" will not help much in the event of a catastrophic failure - it tends to "close the barn door after the cows get out".
Fuses may prevent some speaker failures, but in reality the fuse needs to be sized near the max capability of the driver/speakers and it's hard to say if the fuse or the driver will blow first, since there needs to be a time delay factor before the fuse blows (or else it will blow all the time) and also fuses are non-linear resistive elements in series with the speakers (ie. sources of distortion).
_-_-
Thumps, technically are not DC. Very LF AC is what that is.
ESLs are generally run using a step up transformer, so no DC can pass.
Planars and true ribbons vary depending on if they use a HP filter and/or a transformer. A true ribbon or a HF planar will often use both. LF planars, like an Apogee speaker will not have any DC blocking for the LF section. They are subject to damage due to high current DC passing through the diaphragm.
Oscillation will not be something that any of the above will be able to avoid damage. HF oscillation can and will damage almost any speaker. ESLs being least susceptible to this type of damage. The main reason being that most step up xfmrs will exhibit poor throughput (frequency response) at frequencies that are typical of parasitic oscillations. Also there is no element to overheat since the transfer is electrostatic.
Any speaker section with a LP filter (or bandpass) will attenuate HF parasitic oscillations substantially, so little chance of damage in this area.
Most "amp protection" will not help much in the event of a catastrophic failure - it tends to "close the barn door after the cows get out".
Fuses may prevent some speaker failures, but in reality the fuse needs to be sized near the max capability of the driver/speakers and it's hard to say if the fuse or the driver will blow first, since there needs to be a time delay factor before the fuse blows (or else it will blow all the time) and also fuses are non-linear resistive elements in series with the speakers (ie. sources of distortion).
_-_-
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DC will negativley effect the performance of the transformer in all transformer coupled speakers such as Ribbons and Electrostatics. It can lead to saturation, especially if the transformer has no "air gap" as commonly found interstage coupling transformers in valve amplifiers.
Small amounts of DC will have less effect than large amounts of DC.
Transfomers can still be destroyed by DC if its significant to draw a large amount of power, but unless the electrostic speaker bias voltage is fully discharged until after amplifier start up, the switch on of the amplifier is more likely to casue the speaker to overload before its anywhere near enough to destroying the transformer.
In summary DC offset is bad, for all speakers, but for small values trasnformer coupled Ribbon / ESL speakers might be less effected but it will be implementation specific.
Small amounts of DC will have less effect than large amounts of DC.
Transfomers can still be destroyed by DC if its significant to draw a large amount of power, but unless the electrostic speaker bias voltage is fully discharged until after amplifier start up, the switch on of the amplifier is more likely to casue the speaker to overload before its anywhere near enough to destroying the transformer.
In summary DC offset is bad, for all speakers, but for small values trasnformer coupled Ribbon / ESL speakers might be less effected but it will be implementation specific.
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I'm not sure if you're disagreeing or not.......but.....
There is charging associated with any capacitor so current can flow (for a short time) and deflect a fragile ribbon. (The larger the capacitor the greater the deflection.) Steady state DC will obviously be blocked, but turn on/off/on transitions with amplifiers that have significant DC offset, or a malfunctioning amplifier has the potential to damage a ribbon over time.....even with a capacitor inline.
I see many users bi-amping and recommending a large value series "protection" capacitor in their tweeter leg. It's not a 100% solution. 🙂
Cheers,
Dave.
It depends on a lot of factors.
An ESL speaker with a toroid step - up trafo without significant series resistance(or a large capacitor) can saturate significantly from even low DC offsets, causing increased distortion by the least.
No way to make conclusions without knowing what exact systems are in comparison.
An ESL speaker with a toroid step - up trafo without significant series resistance(or a large capacitor) can saturate significantly from even low DC offsets, causing increased distortion by the least.
No way to make conclusions without knowing what exact systems are in comparison.
The OP was talking about destruction, not distortion. Fwiw.
The big issue on "thumps" includes deflection of a ribbon or a cone, and also that if the rise time is sufficiently fast that leading and trailing edge will be routed to the tweeters. Most thumps are pretty slow in electrical terms, so that's not usually a big problem.
Best idea is to not use amplifiers with thumps. The next idea is to not make big mistakes or you will blow some drivers from time to time, and/or eardrums.
It's a high stakes game, this high performance audio stuff. A lot like Indy, Formula or dragster racing. 😀
_-_-
The big issue on "thumps" includes deflection of a ribbon or a cone, and also that if the rise time is sufficiently fast that leading and trailing edge will be routed to the tweeters. Most thumps are pretty slow in electrical terms, so that's not usually a big problem.
Best idea is to not use amplifiers with thumps. The next idea is to not make big mistakes or you will blow some drivers from time to time, and/or eardrums.
It's a high stakes game, this high performance audio stuff. A lot like Indy, Formula or dragster racing. 😀
_-_-
Not all ribbons need to be transformer coupled.
My (2 ohm) Maggie IIIa ribbons are connected directly to my ribbon amp. 🙂
Andy
Well this definitely clears it up!!!
I made a bet with a fellow worker about this and decided to bring it to the experts...seems you are slightly better protected, but maybe not much...
Anyway, all the amps I built do not have turn on thump, have been checked for HF oscillation and DC Offset and dialed in. But I am NOT very careful when live swapping components...Considering i now have Maggie 20.1 (not exactly cheap) I just need to be more careful than I was with my $350 restored Acoustat 2+2 (one hell of a performer and a bulletproof speaker, BTW).
I made a bet with a fellow worker about this and decided to bring it to the experts...seems you are slightly better protected, but maybe not much...
Anyway, all the amps I built do not have turn on thump, have been checked for HF oscillation and DC Offset and dialed in. But I am NOT very careful when live swapping components...Considering i now have Maggie 20.1 (not exactly cheap) I just need to be more careful than I was with my $350 restored Acoustat 2+2 (one hell of a performer and a bulletproof speaker, BTW).
True-ribbons use transformers. Maggies are planar speakers. If the ribbon element is the voice coil, that shows a short to an amplifier; therefore it is transformed to a more easily driven impedance. Planars such as Maggies have an etched conductor on the surface of a membrane material, and therefore have higher inherent impedance, and do not require the transformer.
You see- both are types of 'ribbon' elements/drivers, but they are operated/constructed differently.
Later,
Wolf
Well, many folks would argue with you that the ribbon tweeter in Magnepans IS a true-ribbon tweeter. 🙂 (Some semantics I suppose.)
Regardless, the Maggie "ribbon" tweeters do not utilize a transformer and do not have any DC protection other than series capacitors(s).....which in Andy's case he's removed. But he knows to be careful.
Dave.
Regardless, the Maggie "ribbon" tweeters do not utilize a transformer and do not have any DC protection other than series capacitors(s).....which in Andy's case he's removed. But he knows to be careful.
Dave.
I believe you are mistaken. Magnepan True Ribbons Tweeters (some 2.x, 3.x, and 20.x) have no diaphragm or membrane material - just a pleated Aluminum ribbon strip between two magnets, and get their higher resistance (to be used without transformer) due to width and thickness of ribbon, while the QR ribbons are "Quasi Ribbons" Mids and tweeters are as you describe (on a diaphragm). Some Apogees are also as you describe, while Scintillas, Full Range, and Divas Mids / tweeters are True Ribbons, like maggies True Ribbons, and have no membrane attached to the aluminum ribbon.
My Scintilla Mids are about 2" wide and bare pleated aluminum and .1 ohm. There is a maze of aluminum strips to in series for an additional .7 ohms, to get the approx 1 ohm (there is a series inductor offering up its dc resistance in there somewhere too)
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What I said was that all ribbons that do use a transformer... not that all ribbons use a transformer... but yes, those that do not use a transformer do not use a transformer. 😀
As they say before a boxing match, "protect yourself at all times".
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As they say before a boxing match, "protect yourself at all times".
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Yup....all it takes is one slip up...
Like I said, powering up I am careful to start my tube pre, wait 30 seconds, then power up my amp (both DIY), and power down in reverse sequence.
I did have two slip ups with my Krell KSA-50 Clones, where, luckily, the rail fuse saved me...
I would not call a 1 ohm load a safe load for most amplifiers. I may be mistaken in terms of the tweeter in 2-way Maggies, but I was speaking from what I have seen in ribbon designs in general. Their large panels are planars.
In general what I stated is not atypical.
Later,
Wolf
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