Very cool solution

[NOZ]

Ever since I installed my ALK crossovers I have blown out three tweeters in my mains.

I e-mailed AL and he said it could be that the AL I used to have had tweeter protection and the ALK's don't.

A friend of mine gave me a great solution, which I did and found it works great.

Putting a 12 volt automotive lightbulb in the positive line of the tweeter curcuit in the crossover. As the power is turned up, the light glows. As you get to very high levels the light flashes very bright, thus taking away alot of the current going to the tweeter. It also lets you know when to back off with the volume.

I thought this was very cool.

[NOSValves]

Just how high are you cranking them K Horns ? I'm curious because I push the living hell out of my Lascalas with all protestion removed from my AA networks and never have a problem yet knock on wood I also did this with the ALK's I built for a friend and had no problems

[artto]

Yeah, the lamp trick is pretty cool. Has been used for a long time. Many professional amps have done similar approaches. I had an old 68' Standel bass amp that had a small neon light bulb inside the chasis that was used as an overload limiter. Later they moved that bulb to the front panel where you could see it.

I put in some JBL D140 drivers & cut the bulb out. Man, did the amp whale then!

I don't think a fuse will sound any better. I had my speakers fused for several years. Due to another problem, I was systematically tracking down, I removed the fuses. Big change in sound. I had to wonder what I was listening to with the fuses in. Later I also removed the zener diode protection on the tweeters. More improvement.

I've had my system playing ear splitting loud. Sometimes loud enough to make the CD player skip. Or feel the ground vibrating on the patio 20 feet out from the house. Outside lighting fixtures & siding audibly vibrating. And haven't blown any tweeters ('knock-on-wood')in 25 years. So, I don't know, but you've got to be doing something, or have something wrong somewhere. You shouldn't be going through tweeters like that.

[Cut-Throat]

OK - You've protected your tweeters. Are you at all concerned with your ears ? (Most expensive audio gear you own - Priceless!)

I drive my Belles with 3.25 watt per channel Moondogs, and I cannot bear to turn the Volume past halfway.

I am sure the sound tends to distort from Vibrations on your source at that level.

[Malcolm]

Neat trick, isn't it? The reason the light bulb works is because its resistance when hot is about 10 times its resistance when cold. Keep the volume down, it doesn't get very warm, and presents a relatively low resistance. Crank the volume, it gets hot, and presents a relatively high resistance. This is why your incandescent light bulbs at home almost always burn out when you turn them on, not after they have been on for a while.

[Audio Flynn]

something is definitely weird here.

with all that SS power; you are pushing some auditory damaging dbs potentially.

15 wats should be blowing your face off.

???

[lynnm]

NOZ

I would get that amp and your ALK's checked out pronto !

Is the bulb wired between the amp and the Xover or between the Xover and the tweeter driver? The difference is important.

My thinking is that it may be that a component or components, ( or perhaps a connection error ) in the Xover are permitting the full power/range of the amp to feed to the tweeter w/out being frequency filtered. In that case your tweets may be getting what they are designed to handle plus the midrange and woofer frequencies. Definitely a bad deal for the tweeters.

1 watt is a little over 2 volts and with the Lascala that would result in uncomfortably loud sound levels. A little over 2 volts will be unlikely to cause any perceptible heating of the bulb's filament. To cause that bulb to light up brightly would require several times that amount of power.

There is definitely something wrong here !

You have not solved your problem but perhaps have inadvertantly provided us with a clue. It is obvious that too much power is whacking your tweeters and bulb or no bulb more trouble (and expense lays in wait). Best guess is that the amp is being driven into clipping ( user problem - too gawdammit much volume) or the amp is clipping at what should be normal power levels The amp may be overdriving because of a problem in its preamp stages resulting in excessive signal levels being fed to the PA stage leading to clipping or the Pa stage may be saturating for some reason other than being overdriven.

Clipping eats tweeters !

Do a search on Google for a description of clipping.... Briefly clipping results when an amp is driven beyond its capability to provide clean power and what happens is that the amps output devices pump every bit of power they can muster into the highest frequencies for inordinately long periods. The high frequencies are where by definition tweeters live and die. Tweeters unfortunately are the least robust components in a speaker.

Ordinarily the tweeter's lack of power handling capability is a non-issue because it takes very little power to reproduce the highest frequencies even at high overall volumes and in any event the high output is required for at most tiny fractions of a second. When clipping occurs the tweeters are treated to the full output of the amp for rather large fractions of a second causing the voice coils to heat up and eventually melt.

Sometimes a user will say something to this effect - This is strange because I have listened loudly for a long time without a problem and then suddenly the tweeters quit at lower volumes. That is the result of the Voice coils having been overheated. Every time a voice coil is overheated the wire in the coil becomes a little degraded with respect to its power handling capability. Thus each time clipping occurs the tweeter's power handling ability is reduced by a small margin. The cumulative effect is however that at some point the tweeter will fail and might well fail at what most would see as a reasonable power level.

[WMcD]

This has been around for a while.

I never paid much attention to it because I've never blown a tweeter. Oh, except for that time when I inadvertly fed it a very loud test tone. The first reaction was to get away, the second was to get to the volume control before the voice coil blew. I lost that race.

When the solution was more widely circulated, there was a particular part number for the bulb. I'd imagine that only wattage is critical.

So, what sort of lamp did you use?

Gil

[Audio Flynn]

Lynn,

Good point the bulb is not treating the root cause; only a symptom.

Blown tweeters are not a cause just an effect.

Amp clipping is most unlikey when using a Klipsch; unless you are throwing a party in an airplane hangar for a 747.

Why is it clipping?

i remain confused...

[djk]

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.

[NOZ]

Thanks for all the replies.

I am well aware of most of the concerns as well. I will check the crossovers for the connection on the litz wire. I was very careful in strippng each strand, and tinning them as well.

I was a bit puzzled when both of my mains went as well, because it didn't happen while I was listening to it.

I'm pretty sure when it happened, while I wasn't around

I turned on the system one day and thought, hey this sound weird. I put my ear to the tweeters and nothing.

I do turn it up once in a while just to remind myself just what the system is capable of.

I don't know if the sound is affected at all by this because I am using k76-k's temporarily, until my new diaphram kits arrive. I'll get them sometime next week.