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" Why not use a polyfuse ? " Too slow. A 561 or 211-2 is about right. It will have less insertion loss than a Polyswitch, and after a few 10's of milliseconds of overload it will heat up and attenuate the signal in a smooth fashion (instead of cutting out like a Polyswitch). " In series with the positive wire or negative? " Either, makes no difference. Klipsch used to use a 0.9A Polyswitch in the KG4 and I had to replace tons of diaphragms when high-school students played their 50W NAD amps at too-damm-loud volume levels. Installed lamp, end of problem. It also made them sound much smoother when the amps got harsh during clipping. I even had students wanting the lamps when they had never blown a tweeter. The KG//2 products originally had clear cones and the lamp would light up the cones when you played them too loud. I originally noticed the 561in the Boston Acoustics C700 loudspeakers, the 211-2 is easier to solder to (its a 561 with tinned end caps). I've seen these in just about everything in the decades since. EV had a tweeter protector for the T35/K77 product that was based on a relay, it would cut-out like a Polyswitch, but was much faster. Then later on they had a bulletin showing how to add a lamp in parallel with the relay to make things work smoother. I've been thinking about duplicating the later EV version with the lamp (for the purest that wants the lamp out-of-circuit completely at low volume levels).

"I am interested from the academic point of view. Also i might require to make for 2" compression driver. This will also increase my knowledge about the subject. " "I am also waiting 4 ur details/new thread about the klipsch protection circuit" OK, let's keep on with it here for a while. Drivers fail for two reasons: Excess average power Mechanical damage Clipping will not hurt anything if it does not cause the above problems. After larger amplifiers (above 50W) became common, problems with high frequency units self-destructing became a problem. A tweeter like the EV T35/Klipsch K77 could handle 5W continuous, 50W for 10mS peaks, so normal program material wasn't the problem. The tweeters were dieing from mechanical failure. The voice-coil was wound with aluminum wire that ran out to the terminals on the frame (self-termination). Shallow slopes in typical crossovers (6dB) combined with higher drive levels produced failures. Copper wire was tried instad of aluminum (aluminum work-hardens in a very short time). Still, the failures continued. Klipsch switched to the 18dB crossovers in the very early 70s. This helped with the excursion failures. Now, 100W+ amplifiers became common. Klipsch went to cathode-to-cathode connected zener diodes. These clipped off the peaks that were mechanically destroying the tweeters. Things went well for about ten years. In the early 80s it was time to try and get rid of the expensive band-aid (the zener diodes). EV changed the lead-out wire from the self-terminated copper voice-coil wire to a flat BeCu wire like used on expensive JBL and Altec type compression drivers. A new network was designed with an elliptical filter with 50dB of attenuation only a half-octave away from the crossover point. A fast- acting instrumentation fuse was added. Problem solved? The new version of the tweeter used a UV cure adhesive vs the old thermo-set adhesive. After the fuses blew from modern program material (about the same time as the introduction of the CD), they got replaced with fast-blow types (which offered reduced protection). The special instrumentation types were very expensive, and very hard to find. The new UV cure adhesive got soft, bubbled, and failed quite easily. A PolySwitch was tried. Too slow. The old thermo-set adhesive came back. The combination of the super-steep crossover, the flat BeCu lead-out wire, and the PolySwitch seemed to work (with the old adhesive). The zener diodes were retired for mainly two reasons: cost, and limited dynamic range. The AA networks used a pair of 5.1V 10W zeners. These only allowed about 2W RMS through before they started clipping off the peaks (a 4W peak square-wave) . With the advent of digital program material, 2W of undistorted program material no longer seemed adequate (about 97dB at 10 foot). The zeners limited the maximum distorted output to about 100dB at 10 foot. Removal of the zeners allowed exploitation of the 50W/10mS rating of the tweeter, about 14dB more output capability (referenced to the 2W RMS zener clamp). What did EV do for products sold under their brand? The STR tweeter protector was developed for this use. Later it was modified by adding a lightbulb in parallel with the relay contacts. I hope this give a little insight into what is needed for tweeter protection, and how we got to where we are. Vifa, Dynaudio, and others offer a choice between self-terminated tweeter lead-outs and a braided (or tinsel) type lead-out. The difference in cost for the braided type is worth it in my book. Most manufacturers of lower-priced product do not spend the money for this, or better crossovers either (although I am seeing lighbulbs and/or PolySwitches in some inexpensive product). Crossovers and tweeters must be designed to avoid mechanical damage in normal use (correct slope, frequency, and lead-out wire for the intended use). Long-term thermal protection is worthwhile. Some sort of switch device (relay, PolySwitch, fuse) in conjuction with a lightbulb seems to be the most cost-effective. Due to the long time constant of lightbulbs, most use does not seem to demand the switch (which shorts out the lightbulb in normal use). Suggested current levels: For 1" coils (tweeters), about 1A. The 561 or 211-2 automotive lamp has worked well in this application. For 1-3/4" coils (1" compression drivers), about 2A. The 1156 type automotive lamp has worked well in this application. For 3" (kapton) to 4" (nomex) coils (2" throat 16 ohm compression drivers), about 2A. I have found a 1.5A AGC (or 3AG) type fast-blow fuse will pass 400W of program material in normal use, and blow almost instantly if bad feedback is encountered. A pair of 1156 automotive lamps wired in series with each other, and then wired in parallel with the fuse will allow the show to go on when the fuse blows, and still offer some protection. If the fuse blows in the course of normal use, you need additional HF drivers, horns, and amplifiers. __________________ Candidates for the Darwin Award should not read this author. "As for using a L pad attenuator the idea of this is to maintain the same Resistance - Impedance as the Driver ie 8R0 to allow the crossover components to correctly filter the frequency. So how does this increase the loading? " Is this a trick question? It would seem obvious that the size of the lightbulb would need to be changed for every different attenuation value (if it's to be of any use). "So a 500W amplifier will deliver over 700W power to the driver if clipped hard enough." Really? Power goes with the square of the voltage, so it goes from 500W to 1KW, but that has little or nothing to do with why the drivers blow. Clipping can damage speakers, but not for the 'urban legend' reasons. "If you’re getting the idea I don’t believe in the clipping/ harmonic theory, you’re right. So let’s investigate the phenomena further. WHEN SINE WAVES CLIP When sine waves clip severely they resemble square waves in shape, introducing massive distortion. In the extreme case, a perfect square wave has the highest level of harmonic components (See Figure 1). A less clipped sine wave has components at the same frequencies but at lower levels. Let’s look at the square wave example shown in Table 1 (at left). Fourier analysis shows the harmonic structure. As you can see, the total amount of instananeous power left to make it through an ideal 1kHz crossover (and on to the tweeter) is less than two watts (0.83 + 0.589 = 1.419W). Hardly a problem. And remember, this simulates severe overdrive of a 100 watt amplifier with a sine wave to make an ideal square wave. Driving it harder will not increase the harmonics. This analysis shows if a small tweeter that only handles 5 or 10 watts is used in a 100 watt speaker system it would not blow out, even under square wave conditions. Yet it does. It takes a lot more than this to cause major failure. " Consider a worst case situation, an amplifier overdriven by 10dB or so. The bass content of the program material causes the amp to clip, the excess HF content from clipping harmonics fed to the tweeter is trivial. However, the average level fed to the speaker at mid and high frequencies is elevated as much as 10dB (due to the input overdrive) during non-clipped passages. WOOFER MECHANICAL DAMAGE (assume the design has sufficient x-max for in-band signals) It's not the clipping per se, but the poor design of the amplifier causing this. The pole in the feedback loop is generally poorly chosen and lower in frequency than the input pole, and above the power supply/load pole, so the poorly designed amplifier pumps out rail-to-rail signals at the feedback pole every power supply time constant. Good design reduces or eliminates this problem (although it seems like 99% of amplifiers have this problem). The easiest way to fix this is to change the poles so the feedback pole is at a higher frequency than the power supply pole, and the input pole is higher than the feedback pole. It also helps to put clamp diodes across the feedback cap. Another way to fix this is to put an input clipper on the amplifier. NAD amplifiers have this kind of a circuit (they call it 'soft clipping') and it tracks the supply voltages so you get the maximum power the amplifier is capable of. Since the input clips before the feedback loop clips, it's always stable. I used to put 50W NAD amplifiers in clubs with four Klipsch Heresy on them, you wouldn't believe how loud this combo will play driven a few dB into clipping. "2) Many crossovers barely handle the rated power of a speaker system, let alone the effect of a clipping amplifier. When inductors saturate, the tweeter gets not only the normal signal at high power, plus the distortion products from the clipping, but also back EMF from the saturating inductors and signals below the normal crossover frequency because the filter system in overload." Only the cheapest of speakers use low quality parts these days. Back-in-the-day a network needed the tweeter cap replaced (if it was an electrolytic) or the tweeter inductor (if the tweeter cap was a film type) after the tweeter burned out and the operator continued to play the system. In 30 years I can pretty much count on one hand the woofer inductors that failed in hi-fi use, these all developed shorted turns (causing damaging infrasonic woofer excursions). In pro sound I saw quite a few woofer inductors fail from too high of a DC resistance (causing the insulation to burn off the wire and the inductor to short out). The last KW is the most important, how it behaves at the limit. A well behaved amplifier with no dynamic off-set when driven 6dB into clipping sounds much better than a wimp amp with a built in limiter, even if it is twice the rated power. (This is tiresome as I have explained it many times before. The above was a compilation of many old postings of mine, I hope it is intelligible) __________________ Candidates for the Darwin Award should not read this author.

From an old post of mine: Drivers fail for two reasons: Excess average power Mechanical damage Clipping will not hurt anything if it does not cause the above problems. After larger amplifiers (above 50W) became common, problems with high frequency units self-destructing became a problem. A tweeter like the EV T35/Klipsch K77 could handle 5W continuous, 50W for 10mS peaks, so normal program material wasn't the problem. The tweeters were dying from mechanical failure. The voice-coil was wound with aluminum wire that ran out to the terminals on the frame (self-termination). Shallow slopes in typical crossovers (6dB) combined with higher drive levels produced failures. Copper wire was tried instad of aluminum (aluminum work-hardens in a very short time). Still, the failures continued. Klipsch switched to the 18dB crossovers in the very early 70s. This helped with the excursion failures. Now, 100W+ amplifiers became common. Klipsch went to cathode-to-cathode connected zener diodes. These clipped off the peaks that were mechanically destroying the tweeters. Things went well for about ten years. In the early 80s it was time to try and get rid of the expensive band-aid (the zener diodes). EV changed the lead-out wire from the self-terminated copper voice-coil wire to a flat BeCu wire like used on expensive JBL and Altec type compression drivers. A new network was designed with an elliptical filter with 50dB of attenuation only a half-octave away from the crossover point. A fast- acting instrumentation fuse was added. Problem solved? The new version of the tweeter used a UV cure adhesive vs the old thermo-set adhesive. After the fuses blew from modern program material (about the same time as the introduction of the CD), they got replaced with fast-blow types (which offered reduced protection). The special instrumentation types were very expensive, and very hard to find. The new UV cure adhesive got soft, bubbled, and failed quite easily. A PolySwitch was tried. Too slow. The old thermo-set adhesive came back. The combination of the super-steep crossover, the flat BeCu lead-out wire, and the PolySwitch seemed to work (with the old adhesive). The zener diodes were retired for mainly two reasons: cost, and limited dynamic range. The AA networks used a pair of 5.1V 10W zeners. These only allowed about 2W RMS through before they started clipping off the peaks (a 4W peak square-wave) . With the advent of digital program material, 2W of undistorted program material no longer seemed adequate (about 97dB at 10 foot). The zeners limited the maximum distorted output to about 100dB at 10 foot. Removal of the zeners allowed exploitation of the 50W/10mS rating of the tweeter, about 14dB more output capability (referenced to the 2W RMS zener clamp). What did EV do for products sold under their brand? The STR tweeter protector (relay based) was developed for this use. Later it was modified by adding a lightbulb in parallel with the relay contacts. I hope this give a little insight into what is needed for tweeter protection, and how we got to where we are. Vifa, Dynaudio, and others offer a choice between self-terminated tweeter lead-outs and a braided (or tinsel) type lead-out. The difference in cost for the braided type is worth it in my book. Most manufacturers of lower-priced product do not spend the money for this, or better crossovers either (although I am seeing lighbulbs and/or PolySwitches in some inexpensive product). Crossovers and tweeters must be designed to avoid mechanical damage in normal use (correct slope, frequency, and lead-out wire for the intended use). Long-term thermal protection is worthwhile. Some sort of switch device (relay, PolySwitch, fuse) in conjuction with a lightbulb seems to be the most cost-effective. Due to the long time constant of lightbulbs, most use does not seem to demand the switch (which shorts out the lightbulb in normal use). Suggested current levels: For 1" coils (tweeters), about 1A. The 561 or 211-2 automotive lamp has worked well in this application. For 1-3/4" coils (1" compression drivers), about 2A. The 1156 type automotive lamp has worked well in this application. For 3" (kapton) to 4" (nomex) coils (2" throat 16 ohm compression drivers), about 2A. I have found a 1.5A AGC (or 3AG) type fast-blow fuse will pass 400W of program material in normal use, and blow almost instantly if bad feedback is encountered. A pair of 1156 automotive lamps wired in series with each other, and then wired in parallel with the fuse will allow the show to go on when the fuse blows, and still offer some protection. If the fuse blows in the course of normal use, you need additional HF drivers, horns, and amplifiers.

The #561 or #211-2 automotive lamp has a cold resistance of about 0.5Ω, it will pass transients of 10mS or so (typical musical program material) without heating up.

"! A light bulb gets higher resistance when it heats up, but a tweeter will blow long before a light bulb will heat up! What's needed here is the Polyswitch used in the later Klipsch networks. " Well spoken by someone who has not bothered to measure either device! The 561/211-2 is MUCH faster to respond than a PolySwitch. http://ps.circuitprotection.com/docs/RXE050_rev_G.pdf Uhh, it is rated for 4 seconds to trip at 500% of the hold current. The lightbulb only takes a few 10s of milliseconds to heat up. For a two-way speaker like the Kg4 the lightbulb by itself may be TOO FAST. For the tweeter in a three-way it is just right. For the two-ways I recommend wiring a 2.2 ohm 2W resistor in series with a 561 or 211-2 bulb, and parallel this with a RayChem RXE050 PolySwitch. This goes in the hot lead to the tweeter. The resistor forces most of the signal to go through the PolySwitch. After the PolySwitch trips most of the signal goes through the lightbulb. If you overdrive it hard, the lightbulb will glow very bright. On old Kg models with clear cones, they will light up when driven too hard. On newer models with opaque cones a LED may be mounted where it may be seen behind the grill. No electrical connection is required for the LED, just get the lightbulb somewhere near it (IOW, the LED is just a colored lense). For the audio purist that objects to having what is in effect a semiconductor in series with his tweeter, and views the 1.75dB loss associated with the 1.17 ohm post trip resistance (this is what you actually get in the LaScala type AL networks), you have several choices. Run naked and risk it. Run the lightbulb only. Build the EV STR tweeter protector designed for this tweeter. This substitutes the relay for the PolySwitch (no loss when not tripped), with the lightbulb in parallel with the relay. Effectively out-of-circuit until needed. B&W also uses this circuit in some models, their trade name for it was APOC.

Replace both diaphragms, the newer ones are a bit different. If you add a #561 or #211-2 automotive dome lightbulb in series with the tweeter it will virtually eliminate failures, JBL (and many other companies) do this in various models.

Your speakers are either damaged or were improperly repaired. The KP-201 has a minimum impedance of 4.5 ohms, so two per channel on a newer Crown may be too much. If you have a Power Base 1, Power Tech 1, or a D150 it will blow up. I used to put sets of four of these in bars with a 50 watt NAD to drive them and they can rip your face off. Get them looked at, and get a different amp (no more than 100 watts). Take apart the tweeters and see if the voice coil is dis-colored, add a #561 dome lamp in series. Make sure the woofers all work and they are in phase. If a woofer does not work it will cause the amplifier to shut down or blow up! Check the 33µF cap in parallel with each woofer. Examine the woofer inductor. If the wire is dis-colored, replace.

The lightbulb solution is faster than a fuse or polyswitch, and less invasive of the sound. If you want the ultimate tweeter protection get the EV STR and do the lightbulb mod. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=47092&item=3769716750&rd=1&ssPageName=WDVW The light bulb mod is described on an addendum sheet and also covers modding the STR for use with the 1823/24 midrange drivers. For out interests though, all that need be done is slap a #561 in parallel with the relay contacts.

"Man, I must intimidate the tar out of you!" No, you just hand out bogus advice. "You just live to pick apart anything I say.." I do tend to hold you to a higher standard because you tend to hold yourself out as an expert. "Maybe it's because you are afraid I can do anything you can do withOUT the BSEE degree." You can't, plus I flunked out of high school the second half of 10th grade. "You and I could have learned a lot from each other but instead you prefer to try to make me look bad at every opportunity. I am sick of it!" Sounds like a personal problem to me. "Why don't you just call me an idiot like you have in the past?" I just show how foolish some of the things you say really are. A lightbulb is really a very high tech protection device. The only real problem with small ones is they may be too fast. "The fact is that I once built a quelch circuit out of 2 lamps like that and two resistors in a bridge circuit around a speaker for a communications receiver back in about 1972. It worked very slowly!" Different application, not a valid comparison. "Light bulbs change their resistance in proportion to their brightness." No kidding, that's whay they work as a tweeter protector. "What's faster, a tweeter diaphragm hitting a phase plug or a light bulb heating up?" You didn't even bother reading the spec sheet on the PolySwitch, did you? At 200% of the hold value they can take up to ONE HOUR to trip, at 500% of the hold value they still take 4 SECONDS. The diaphragm hitting the phase plug has to do with the crossover slope and frequency, and nothing to do with the thermal protection we are discussing. "Next you are going to tell me to protect a tweeter with an instrument fuse." They work faster than a PolySwitch, and I must say that an AGC-1A blows faster than an AGC-3/4A does, so in this case the bigger fuse offers more protection. "I stand by what I said.. A light bulb is TOO SLOW!" A 1KW PAR64 is slow, a 10W 561/211-2 may be TOO FAST for a two-way. I, of course, have measured the resistance ratio changes using a current probe and an oscilloscope. "GO AWAY or try acting like you have not been elected by Klipsch to be the personal Al K watcher." As soon as you quit handing out bad advice.

A 561 or 211-2 automotive lamp is the correct one to use. On an ALK network you must check and see if the connections to the 0.2mH tweeter inductor are OK. Put a jumper lead across the 6µF cap, use an ohmeter across the tweeter leads, it should measure close to a dead short if everything is OK. Some people have problems stripping, tinning, and soldering that litz wire. The best protection scheme is to use the EV STR tweeter protector designed for the T35/T350 tweeters. It uses a relay that pops open on overload, under normal use it shorts out the lightbulb. If you have old style tweeters that don't have the BeCu flat ribbon lead-out wire they will eventually just die from metal fatigue at some point. The flat ribbon style made with the clear adhesive on the VC will fail. The ones with the flat ribbon and the green adhesive are the best. The clear was a UV-cure, the green is a thermo-set. EV used thermo-set originally, tried UV-cure, and then went back to thermo-set.

Buy a pair, the new ones are different than the old ones. If you don't want this to happen again then go to an auto parts store and buy a pair of 561 lamps and wire one in the hot lead to the tweeter in each speaker.

An XR600 'breadloaf' mixer is 200W at 4R. Pre 1985 Heresy speakers are OK for light duty PA, the Heresy II is for all intents and purposes 4R and only one per channel may be driven. To prevent woofer failure a 50hz high pass filter (sometimes called a low filter or subsonic filter) must be used. The E type Heresy networks that you have should be partially updated to E2 type by adding a 0.245mH inductor in parallel with the output to the tweeter. A 561 or 211 automotive dome light bulb must be added in series with the hot lead to the tweeter or it will burn out about the third time it goes into feedback. Eventually you will want to add a subwoofer if you need to run program material with bass through the system. A friend of mine ran his Heresy for PA like this for ten years before upgrading. It was just vocals and acoustic instruments for a duo, but he could fill the local 1900 seat theater with good sound.

Hey Klipschguy, a K33E only has a 2" coil behind the 4.5" dustcap.Same as yours.Take an ohm meter to yours.I bet they measure 4 ohms too.Two ways to kill a woofer A) overheat the coil.An AGC3 fuse will take care of that. B)overexcursion.Limit yourself to a 200 watt amp maximum and use a 30hz high pass filter with a Q of one.I have never seen a blown Klipsch midrange.I have had to repair a couple of the K52,57 mids due to a bad leadout wire.Tweeters burn due to clipping.An automotive type #561 lamp in series will cure that.

>>First, a MC2200 does not have meters!!!!!!<< Yeah Bill,you're right.I went back and edited it to read MC2205.I guess the point was that a 1A fuse can pass 300W peaks without blowing.BTW the fuse would blow instantly if you turned off the powerguard.I really feel that the lightbulb is the answer for people that like to play it loud every now and then.Klipsch had such a problem with their KG tweeter diaphragms blowing that they started putting .9A self resetting fuses (Raychem PolySwitches) in some of their models.These are too slow/too big to work 100% of the time so I resorted to the 561 lightbulb trick.I did this back when the diaphragms were $4 each.Now that they are $40 a pair.....>>BTW-- Does anyone know of an equipment (stereo) rack, ya know the kind that's only 19" wide on the inside and all your stuff can just bolt into some mounted angle-irons on the component's rack ears? I'd like to have one that is furniture grade, not industrial looking, on casters and 22" deep or more. << Just buy the rack rails from Mid Atlantic and bolt them into a furniture rack.18 space rails (31.5") are only $20 a pair.

Go to an auto parts store and buy a pair of 561 dome light bulbs.Wire one in series with the hot lead of each tweeter.Don't bother with your class A question.It is meaningless.99% of solid state amps are class AB.The A part is usually 20mA or so of bias.Power is the square of current times impedance(.02*.02)*8=.0032W.If you were an engineer I would refer you to Douglas Self's site to read why class B amps have less distortion than class AB.