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Kemo ultrasonic generator mo48n

Mr diode

New Member
Hello all , I wonder if anyone can give me some advice. I bought a kemo mo48n device to work with a piezo tweeter to create ultrasonic sound to deter a barking dog, I bought a 20 watt piezo speaker and everything works after I hooked it all up , but I do not think it is very loud . Of course you can not hear the ultrasonic sound high freq , but when you can hear it when adjusted down with the dial , it does not seem very loud. I can not get a response from kemo on what power the mo48n is putting out. I then bought a kemo mo32n 12 watt amplifier to boost the signal , but after hooking it all up exactly how the instructions say , it did not work very well. So my question is .. what can I use to increase the output of kemo mo48n ultrasonic generator ? Like I guess you can not just use any old amplifier , and my local electronics shop has so far been no help. { a guy wanted to sell me a kit form amp , only $10 , but it was rated at 1 watt ???? ] useless . Can anyone give me any advice on what to actually get and how to hook it up properly. I am powering the kemo mo48n with a 15volt , 2 amp power supply , so there is heaps of power going in. I also checked the connections and there is 14.7 volts at the input. Also the kemo mo48n does not have pos or neg on the wires coming out for the speaker , but I am sure the piezo speaker has a positive and negative. I have tried swapping the wires around , but nothing much happened.

best regards tony.c
 

Nigel Goodwin

Super Moderator
Most Helpful Member
With no schematic it's impossible to know what's coming out of the kemo mo48n, but a singled ended amplifier can output 4W to a 4 ohm speaker, and a bridged amplifier can output 16W to a4 ohm speaker.

As piezo's don't have a 'fixed' impedance, it's difficult to know exactly what's going on.

However, it's impossible to tell if it's 'loud' or not, as it's ultrasonic, and even turning it down to audible frequencies means it's still high frequency, and won;'t sound loud either.

You really need to get an oscilloscope on the output, to measure what's coming out.

There's also the problem that there's plenty of questions about them stopping barking dogs anyway.
 

gophert

Well-Known Member
Most Helpful Member
Sounds like we are solving the solution rather than solving the problem (barking dog).
 

Mr diode

New Member
With no schematic it's impossible to know what's coming out of the kemo mo48n, but a singled ended amplifier can output 4W to a 4 ohm speaker, and a bridged amplifier can output 16W to a4 ohm speaker.

As piezo's don't have a 'fixed' impedance, it's difficult to know exactly what's going on.

However, it's impossible to tell if it's 'loud' or not, as it's ultrasonic, and even turning it down to audible frequencies means it's still high frequency, and won;'t sound loud either.

You really need to get an oscilloscope on the output, to measure what's coming out.

There's also the problem that there's plenty of questions about them stopping barking dogs anyway.
Hello , ok thanks. Im not even sure if the ultrasonic is working with the mongrel or not. Kemo do not respond . They give you details about it in the instructions , but nowhere does it say the output. They claim you can hook up to 5 piezo tweeters to it. I very much doubt that . Had to get it from Germany as no one sells them here . The ultra sonic stop barking device is useless . did not work at all. Wasted $100 on a piece of crap . If some one could build a high output ultra frequency generator and sell it to the public they would be super rich. And I have no idea if the kemo mo48n is a single ended amp or bridged amp. cheers t.c
 

Nigel Goodwin

Super Moderator
Most Helpful Member
If some one could build a high output ultra frequency generator and sell it to the public they would be super rich.
You're assuming rather a lot - for a start will it stop dogs barking? (why should it - it's just as likely to make them bark), and not to mention the legalities of broadcasting high power ultrasonics at the public (it causes ill effects in some people, particularly children).

Electronically it's trivial to do - but no one will get 'super rich' from it - although they could get 'super poor' after the court cases.
 

Mr diode

New Member
You're assuming rather a lot - for a start will it stop dogs barking? (why should it - it's just as likely to make them bark), and not to mention the legalities of broadcasting high power ultrasonics at the public (it causes ill effects in some people, particularly children).

Electronically it's trivial to do - but no one will get 'super rich' from it - although they could get 'super poor' after the court cases.
Well the research that has been done says that dogs do not like high frequency sounds . It has been used for a long time to train them . There is no law that says you can not have a high frequency device. Where I am pointing the device , there are no children or elderly , or sick etc. The only people that get ' ill effects ' are the ones that have to listen to loud barking mongrels , that bark at anything that moves , 24/7 . No one will end up in court , unless it can be proved your device actually did something to someone . Maybe my alternative is to lean over the fence with a m14 rifle and put a few into the mutt ? Then.. I would be in court .
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Well the research that has been done says that dogs do not like high frequency sounds . It has been used for a long time to train them . There is no law that says you can not have a high frequency device. Where I am pointing the device , there are no children or elderly , or sick etc. The only people that get ' ill effects ' are the ones that have to listen to loud barking mongrels , that bark at anything that moves , 24/7 . No one will end up in court , unless it can be proved your device actually did something to someone . Maybe my alternative is to lean over the fence with a m14 rifle and put a few into the mutt ? Then.. I would be in court .
And as I said, it's absolutely trivial to make a high power ultrasonic generator, which according to you would make someone 'super rich' - I've never noticed any such devices, nor anyone having got super rich from them?.

I presume the 'research' doesn't mention preventing dogs barking?, which is why you didn't mention it.

The trivial 'device' by the way, is simply an audio amplifier (with the high frequency range extended slightly, if needed) fed from an ultrasonic oscillator.

High frequencies don't travel that well, so it's likely to be a relatively short range device.
 

audioguru

Well-Known Member
Most Helpful Member
1) Your piezo tweeter is made to produce sounds, not ultrasonics.
2) The Kemo M032N amplifier produces 12 Whats of "music power" into 4 ohms which is only about 5 real Watts into 8 ohms that the piezo tweeter is referenced. An amplifier that produces 20 real watts into 8 ohms at the ultrasonic frequency would be a little louder.
3) The amplifier has no detailed spec's and is made for audio so maybe it produces reduced levels at ultrasonic frequencies.
Then of course the ultrasonic level is low.

Find a tweeter and amplifier that show that they can produce ultrasonics at the power you need.
I agree that the dog will bark each time you use it.
 

Mr diode

New Member
1) Your piezo tweeter is made to produce sounds, not ultrasonics.
2) The Kemo M032N amplifier produces 12 Whats of "music power" into 4 ohms which is only about 5 real Watts into 8 ohms that the piezo tweeter is referenced. An amplifier that produces 20 real watts into 8 ohms at the ultrasonic frequency would be a little louder.
3) The amplifier has no detailed spec's and is made for audio so maybe it produces reduced levels at ultrasonic frequencies.
Then of course the ultrasonic level is low.

Find a tweeter and amplifier that show that they can produce ultrasonics at the power you need.
I agree that the dog will bark each time you use it.
Hello audioguru , your advice is the best I have received so far . I am still a bit confused about a few things. I thought piezo tweeters were the right choice for ultrasonic sounds as that is what kemo recomends when you purchase a kemo mo48n . My piezo tweeter is rated at 20 watts . I do not think mo48n is putting out anywhere near that amount of power. I have managed to hook up mo32n to mo48n and both are working . But on the audible level , it still does not sound real loud . mo48n and mo32n do not say what is positive or negative on the output for the tweeter . Are tweeters meant to have positive and negative inputs ? I am a bit disapointed in kemo so far as you do not get all the information you need . Is it true that high frequencies do not travel well. I need my sound to travel about 8 to 10 meters . is that pushing it you think ? I am going to hook up my multimeter and see how much power mo48n is drawing from the power supply . same with mo32n . I may be over reacting a bit. I get good days and bad days with noise. probably just getting old and cranky . cheers tony.c
 

Mr diode

New Member
1) Your piezo tweeter is made to produce sounds, not ultrasonics.
2) The Kemo M032N amplifier produces 12 Whats of "music power" into 4 ohms which is only about 5 real Watts into 8 ohms that the piezo tweeter is referenced. An amplifier that produces 20 real watts into 8 ohms at the ultrasonic frequency would be a little louder.
3) The amplifier has no detailed spec's and is made for audio so maybe it produces reduced levels at ultrasonic frequencies.
Then of course the ultrasonic level is low.

Find a tweeter and amplifier that show that they can produce ultrasonics at the power you need.
I agree that the dog will bark each time you use it.
Can you tell me what to get ? thanks
 

audioguru

Well-Known Member
Most Helpful Member
1) Audio is AC, not DC. Therefore a speaker does not have "+" wire and a "-" wire, they use + and - so that speakers can produce the same phase so they do not cancel. You want all speakers to push at the same time and pull at the same time.
2) I do not know which type of tweeter you have or its part number. Does it have a detailed frequency response graph? But most graphs do not show ultrasonic frequencies because speakers usually are not used for ultrasonics.
3) The Kemo L003 piezo tweeter with transformer says it produces 105dB at a distance of 1m which is 99dB at 2m, 93dB at 4m and only 87dB (not loud) at 8m but they do not say at what frequency.
3) The Kemo M048N ultrasonic generator has absolutely NO spec's.

Don't you live in a civilized city that has an anti-noise bylaw? Don't you pay city property taxes? Phone your cityhall and have them deal with it.
 

Saltshaker

New Member
Hello all , I wonder if anyone can give me some advice. I bought a kemo mo48n device to work with a piezo tweeter to create ultrasonic sound to deter a barking dog, I bought a 20 watt piezo speaker and everything works after I hooked it all up , but I do not think it is very loud . Of course you can not hear the ultrasonic sound high freq , but when you can hear it when adjusted down with the dial , it does not seem very loud. I can not get a response from kemo on what power the mo48n is putting out. I then bought a kemo mo32n 12 watt amplifier to boost the signal , but after hooking it all up exactly how the instructions say , it did not work very well. So my question is .. what can I use to increase the output of kemo mo48n ultrasonic generator ? Like I guess you can not just use any old amplifier , and my local electronics shop has so far been no help. { a guy wanted to sell me a kit form amp , only $10 , but it was rated at 1 watt ???? ] useless . Can anyone give me any advice on what to actually get and how to hook it up properly. I am powering the kemo mo48n with a 15volt , 2 amp power supply , so there is heaps of power going in. I also checked the connections and there is 14.7 volts at the input. Also the kemo mo48n does not have pos or neg on the wires coming out for the speaker , but I am sure the piezo speaker has a positive and negative. I have tried swapping the wires around , but nothing much happened.

best regards tony.c
Tony,
I am actually working on a very similar project for the same problem. I will be using 2 piezos with the Kemo 40 watt amp. The trick is getting the voltage right since the Kemo amp has an input rating of <500mv. So I am trying to get that down with a resistor network. Yet my output on the amp doesnt get that much higher....so I am working on that. Plus you need to make sure your amp can handle those frequencies that the generator is producing. In this case you need to be 20-24,0000HZ which is why I got the 40W. I dont think your amp goes high enough and is peaked at 20,000. Plus the voltage on your amp is <80mv .
When I hook up my piezos, which are modded into a PVC cannon, they are very loud. When I lower the frequency to and audible level, it actually hurts my ears. So if nothing else, you should be able to get a similar result straight off your generator. Through your amp is probably a different story based on the specs I see.
 

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