I bought over a year ago a pair of Brand new Budget Skytec cabs, they each have 2*15inch speakers,
a Horn and 4 Piezo tweeters,


Although they have hardly ever been used "I use my Proels" , I have never heard the horn give out any sound ? the 4 tweeters , yes, so I have opened them up for a look I found wired in line with the Flared Horn, a small oblong ceramic component about an 1 1/2 inches long and marked

" 10W 250 and what looks like an upside down horseshoe marking & J "

Now I removed this ceramic and joined the wires & the horn started working , I used my electrical test meter and there is continuity through this ceramic component , so why does the horn not work with this connected. Is is unsafe to run without this "Thing" fitted



The 4 pezios are not wired through any components like this, they are connected straight from the amp input on the inside of the speaker box.

Chris ???

Not being that clever on components - it may be a 'breaker'.

Modern speakers like EV use technology to prevent speaker damage through, in basic terms, 'sound clipping' prevention.

I'm probably wrong. I reckon this is a question for the Timelords of sound..... !

Its a ceramic resistor to prevent you blowing the horn to pieces, the upside down horseshoe thingy is an ohm sign! Yes it should be in place, however when one of mine went west the shop gave me a card with ten ordinary resistors on it, used one of them instead and it worked perfectly and I still have nine spare!

QUOTE

I found wired in line with the Flared Horn, a small oblong ceramic component about an 1 1/2 inches long and marked " 10W 250 and what looks like an upside down horseshoe marking & J "

This component is called a resistor, and like its name suggest's it creates a resistance in the circuit ( I Always wanted to be a Physics Teacher, does it show). Basically, it lowers the current reaching the horn, and helps to protect it in the case of severe overdriving.

Yes the horn will continue to work without it fitted, although I would be vey careful as to how much "Hammer" you give the speakers without it. These resisitors usually only give very small amounts of protection to the driver in any case.

It sounds like the horn may be a piezo type?, was there any other component connected before / after the resistor?, some horns are also fitted with a capacitor which filters out the bass content of the music signal, if there is a capacitor fitted, then you will definetely need to keep that connected!

QUOTE (The Spindoctor @ May 12 2003, 05:27 PM)

Its a ceramic resistor to prevent you blowing the horn to pieces, the upside down horseshoe thingy is an ohm sign! Yes it should be in place, however when one of mine went west the shop gave me a card with ten ordinary resistors on it, used one of them instead and it worked perfectly and I still have nine spare!

If it is a resistor , will this mean that I wont hear the horn untill the Amp is cranked up to a high volume to get power through this resistor?to the horn , the speaker at the moment is sounding better without this resistor , but thats a low volume in my house , as you say it may blow the horn at disco sound levels ?? ..

Why are the piezo's not protected in the same way ??

The resistor (as its name suggests) will drop the voltage passing to the Horn, and this may stop it from operating at very low levels. You will need to have some form of resistor in place if you use it for Disco use, although I would try to lower the value somewhat. Usually 22 ohm 10W resistors are ideal.

The piezo's don't need an external resistor since I'm guessing that they are wired in series (Daisychained) together, by combining them in the same circuit, in series they increase the power handling since the current has to flow through each one. So by connecting 5x 50W piezos in series, effectively you get 250W power handling capacity, although it is safer to run it at 200W

If you only use them for home use then keep the resistor disconnected, since most horns will run directly upto around 50 - 75w RMS. However if you use them for both home & Disco, then try either a 22 ohm 10W resistor or a 10ohm 10W resistor in series with the horn.

QUOTE

The piezo's don't need an external resistor since I'm guessing that they are wired in series (Daisychained) together, by combining them in the same circuit, in series they inrease the power handling since the current has to flow through each one. So by connecting 5x 50W piezos in series, effectively you get 250W power handling capacity,

So would it also work if for now , If I daisy chained the Horn to the tweeters to lower the power reaching the horn ?

Would I find the needed resistors anwhere ?? ..


I have tried disconnecting the 2 *15 inch speakers and the 3 tweeters , then connecting only the horn with this ceramic resistor , and can hear no sound at all from the horn.

No, don't start playing about with combinations!. chances are that its not a piezo horn, and won't work when connected in series with the tweeter.

With regard to the resistor, I'll see what a rummage in the workshop produces

Back again

I am finding this Ohms stuff interesting , so sorry if I am boring you all

I have measured the ceramic resistor from the speaker , I found an ohms tester on my meter

The meter reading on the resistor reads .241K ohm, "note the point before the 241" .

and printed on the resistor is 250 Ohm J , does this mean the resistor is reading its correct value , and only appers to be too high a resistance for the horn to work properly.

I have another make of 3 way budget speaker and I can hear its horn fine even at low levels..

.241k is close as dammit to 250 ohms (.241k = 241 Ohms), allowing for the resistor tolerance of +/- 5 %.

Although 250 ohms is a little over excessive for a Horn, I reckon if you reduced it to around 22 ohms then you would be okay.

Knowing Skytec they've screwed up, and somewhere there is an Amplifier overheating because its got a 22 Ohm resistor in it instead of a 250 ohm one!

Well never mind!! It aint really worth me answering this post as chris as done it for me LOL!!!

well me and chris are electronic engineers, dont know about anyone else on here

Take Care

Rick

Have you checked the resistance of the horn??? It may be open-circuit.
Sorry to disagree with the expert, but I would never advocate driving the horn in a full-range cab without the limiting resistor.
If it wasn`t needed it wouldn`t be there.

I'm not advocating driving the Horn without the limiting resistor, and never was. If you check the spec of most horns then you'll find that they will happily work at upto 75w RMS, some even run upto 100W, and indeed this is how they are run in active systems - i.e no dropper resistor, just a small wattage amplifier driving the horn directly with HF. Assuming that Ninelives is running the Skytec's from a 35 W amp for hi-fi use, then he'll never need a limiting resistor.

It's also worth considering that most Piezo horns will run even higher, and in fact the resistor is there to protect the amplifier in the event of failure of the Piezo circuitry. Should the Piezo fail short circuit then it will drag the amp down and maybe take out the fuse. However if the dropper resistor is in series in this situation then it will continue to present a "dummy" load to the amp .

All motorola piezos are also fitted with filament lamps which prevent any serious overload. I can verify that no harm will result from fitting a 22 ohm resisitor in place of a 250 ohm one. Most crossovers have resistors of no more than 47 ohms in systems running 600W RMS.

QUOTE

Have you checked the resistance of the horn??? It may be open-circuit.

Wrong - if it was open circuit it wouldn't work at ALL, regardless of whether the resistor was in circuit or not

QUOTE

Assuming that Ninelives is running the Skytec's from a 35 W amp for hi-fi use, then he'll never need a limiting resistor.

Whooops !

I better get them un hooked from my old big black Phonic Amp , untill I get those resistors then ;)

I am only tickling the speakers with the amp just now as they are in the house and do have neighbours

QUOTE (Chris_Pointon @ May 12 2003, 10:48 PM)

Wrong - if it was open circuit it wouldn't work at ALL, regardless of whether the resistor was in circuit or not

I`m sorry Chris - I thought that`s what he was saying??

>Although they have hardly ever been used "I use my Proels" , I have never heard the horn give out any sound ? the 4 tweeters , yes, so I have opened them up for a look I found wired in line with the Flared Horn, a small oblong ceramic component about an...........<