Piezo Tweeter for Dogs

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freddi

freddi

Member
Joined 2005
I've used the little Kemo oscillator module w/o any additional amp with 2 paralleled KSN1005 knockoffs - dogs and cats seemed to ignore it but one young UPS guy could hear it 75 feet away. :D A stepup transformer can be used with the CTS type to raise sensitivity to around 103dB at 2.8v
 
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Caramello

Member
Joined 2018
weltersys said:
Caramello,

I have used the APT-80 in a number of loudspeakers. Decent driver for the price, but I don't think the UHF output would be near that of an array of KSN 1165.
I would not use KSN 1165 for any "Hi-Fi" use, but for annoyance factor, they rate very "high" ;^).

1) Since the KSN 1165 is around 30-50 ohms at 20kHz, around 8 volts would be needed for "1 watt", the "93dB sensitivity" is more equivalent to 100 dB. Using 8 drivers would increase on axis sensitivity by around 9dB, near 109 dB.
Some good information here about similar piezo drivers:
Pulsar Developments Ltd - Piezo Tweeter Application Note

2) The relatively high VHF sensitivity is due to narrowing directivity.

3)All of the dozen or so APT-80 drivers I owned had rapidly falling response past 17kHz.
The look more similar to the APT50 measurement on the H290H horn, which has around 95dB sensitivity at 20kHz after the 17kHz peak.
The measurements below were of a APT-80 with no crossover (raw) and of two different crossover designs used in stage monitors.

4) Fairly typical, though other manufacturers "sensitivity" may use 2.83 volts for lower impedance drivers. As mentioned in #1, Eminence would use a much higher voltage to measure a driver with equivalent impedance to the KSN 1165.

5) The APT-80 VHF dispersion is similar to the KSN 1165, the throat angle of the APT:50driver itself being roughly the dispersion at 20kHz. In fact, the horn used on the driver will have no effect on the VHF response, for use at 20kHz the phase plug assembly virtually is the horn.

6) The APT-80 coil will burn if used much more than it's rated 35 watts, about 17.75 volts RMS at 20kHz. The voice coil heating will raise it's impedance considerably at that drive level, reducing sensitivity, "power compression".

7) For wide VHF coverage, an array of either driver would be needed.

Cheers,
Art
Click to expand...
Art, there's a lot of food for thought there, and now I'm a bit stuck as to which to choose.

It's a classic "horses for courses" problem. In my particular situation
A. I know what success I have had with deterring my neighbour's dogs so far, and how I achieved it, and it's possible that I can introduce acoustics as a remote substitute instead
B. I have limited resources for acoustical experimentation
C. Without going into details, the footprint will have to be small, possibly under a short and narrow gap under a fence

Let's discuss the specific issues in relation to the above
1) The Quad 405 that I intend to use can only reach 80 volts pk-to-pk which is 28 volts RMS. Across 30 Ohms only gives 26 Watts RMS i.e. a further 14 dB gain on 1 W SPL. So even if the KSN 1165 is 100 dB at 1W at 1 metre at 20kHz that's still only 114 dB at 1 metre, losing 18 dB to reach 8 metres, giving an on-axis SPL of 96 dB at 8 metres. I don't know what frequency/ies will be required, or what SPL will work, but I could experiment with a large array over the top of the fence when the neighbours are out, but, setting up and aiming an array of 8 tweeters (albeit 4 wired in parallel on each channel) will be cumbersome and time consuming. The same could be said for the APT-80 of course (assuming that the datasheet for the APT-80 is correct at 103 dB at 1 metre at 20 kHz).

2) yep, that's what I thought, it's the same way that RF antennas work (although it's called "forward gain" instead of sensitivity)

3) If you're correct (and I'm not doubting you) then their datasheet for the APT-80 is wrong ? The APT-50 driver is mentioned in their main datasheet for the 80/150/200 , I hadn't though of looking for a datasheet on the APT-50, which does show an alarming roll-off. But do they call an APT-50, attached to different horns, as 80/80S/150/150S/200/200S ? There's also the LA-WG10 and LA-WG14 line array waveguides available. I might have to contact them to find out.

4) Yep I assumed it is typical, but at least they give detail on how their measurements were made. It's annoying that they don't give off-axis response as well.

5) So have they got a different version of horn to produce the graph showing APT-80 at 103 dB at 20 kHz ?

6) That's a very pertinent point, but it won't be on for long periods of time, just a few seconds here and there.

7) Yep, and that could be the killer in my situation, I don't fancy setting it up to experiment with, and it can't be like that on a permanent basis anyway.

But overall, the major issue that I have is how to drive the KSN 1165 from a Quad 405, while getting at least 100W from the 405 into the piezo. I've had a look at the Application Note, and it's a gold mine of info but, unless I missed it, nothing on how to get the power into piezos at normal or even low amplifier output voltages.
 
freddi

freddi

Member
Joined 2005
you could use a little 25 volt matching transformer "backwards". Put some resistance in series with the piezo so at high frequencies, the reflected load will be reasonable.

DJK (R.I.P.) used 2nd / 3rd order highpass with the scheme. A 100uH/8R resistor was used as the Zobel network. I tried it with just a 1uF cap - it was around 103dB 2.8v 1M on the 5 watt tap. Sorry for the blurry image as its a screenshot thumbnail of a deleted imageshack image. For your application you won't need a pad. Perhaps a handheld portable version could be made with a stepup transformer.

E7wNxVS.jpg
 
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Caramello

Member
Joined 2018
freddi said:
you could use a little 25 volt matching transformer "backwards". Put some resistance in series with the piezo so at high frequencies, the reflected load will be reasonable.

DJK (R.I.P.) used 2nd / 3rd order highpass with the scheme. A 100uH/8R resistor was used as the Zobel network. I tried it with just a 1uF cap - it was around 103dB 2.8v 1M on the 5 watt tap. Sorry for the blurry image as its a screenshot thumbnail of a deleted imageshack image. For your application you won't need a pad. Perhaps a handheld portable version could be made with a stepup transformer.

E7wNxVS.jpg
Click to expand...

If I go down the piezo route instead of voice-coil, this is the way I would prefer to do it.
Would that be a standard mains transformer, do they work at 20 kHz ?
 
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Caramello

Member
Joined 2018
Pano said:
Yes, for "Commercial Sound" installations. 70V is common in the USA, 100V in Europe. And there is 25V. They can often be found on eBay for cheap.
Click to expand...

My knowledge of "commercial sound" installations can be written in felt tip pen on a pin head LOL

Are those "peak" voltages ?
i.e. 25 RMS is common in the USA, 35 RMS in Europe. And there is 9 RMS.

or are they RMS voltages ?
i.e. 200 peak is common in the USA, 280 peak in Europe. And there is 70 peak.

and what are distribution transformers used for ?
 
Pano

Pano

Administrator
Joined 2004
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weltersys

weltersys

Member
Joined 2008
Caramello said:
Art, there's a lot of food for thought there, and now I'm a bit stuck as to which to choose.

It's a classic "horses for courses" problem. In my particular situation
A. I know what success I have had with deterring my neighbour's dogs so far, and how I achieved it, and it's possible that I can introduce acoustics as a remote substitute instead
B. I have limited resources for acoustical experimentation
C. Without going into details, the footprint will have to be small, possibly under a short and narrow gap under a fence

D. If you're correct (and I'm not doubting you) then their datasheet for the APT-80 is wrong ? The APT-50 driver is mentioned in their main datasheet for the 80/150/200 , I hadn't though of looking for a datasheet on the APT-50, which does show an alarming roll-off. But do they call an APT-50, attached to different horns, as 80/80S/150/150S/200/200S ? There's also the LA-WG10 and LA-WG14 line array waveguides available. I might have to contact them to find out.

E. So have they got a different version of horn to produce the graph showing APT-80 at 103 dB at 20 kHz ?

F.But overall, the major issue that I have is how to drive the KSN 1165 from a Quad 405, while getting at least 100W from the 405 into the piezo. I've had a look at the Application Note, and it's a gold mine of info but, unless I missed it, nothing on how to get the power into piezos at normal or even low amplifier output voltages.
Click to expand...
A. Possible, if they are not deaf or floppy-ear dogs.
B. Makes success less likely ;^).
C. UHF will be absorbed by grass, over the top pointed down would probably be preferable.
D. From all the samples of APT-50/ APT-80 I have tested it appears to me that the APT-80 graph is not representative of average samples. The same APT-50 driver is used on a variety of Eminence horns, and can be threaded on to other brands too. The LA-WG10 would require the S2B thread on to bolt adapter. If a narrow "wave guide" was attached to the LA-WG10, it's 15 degree vertical dispersion might increase on-axis gain a bit.
E. 20kHz is only about 5/8" long, the "horn" for that frequency is within the throat of the APT-50 driver.

The actual wave-forms used have perhaps as much bearing on effectiveness as the SPL..
Although "DIY" is always a learning experience, I'd be inclined to purchase something like the "Dog Silencer Max", which may be less $$ than all the parts needed, and has a 45 day return policy.
If you have the same results as Freddi, that "design feature" would be very useful :^).

Art
 

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Caramello

Member
Joined 2018
weltersys said:
A. Possible, if they are not deaf or floppy-ear dogs.
B. Makes success less likely ;^).
C. UHF will be absorbed by grass, over the top pointed down would probably be preferable.
D. From all the samples of APT-50/ APT-80 I have tested it appears to me that the APT-80 graph is not representative of average samples. The same APT-50 driver is used on a variety of Eminence horns, and can be threaded on to other brands too. The LA-WG10 would require the S2B thread on to bolt adapter. If a narrow "wave guide" was attached to the LA-WG10, it's 15 degree vertical dispersion might increase on-axis gain a bit.
E. 20kHz is only about 5/8" long, the "horn" for that frequency is within the throat of the APT-50 driver.

F. The actual wave-forms used have perhaps as much bearing on effectiveness as the SPL..
G. Although "DIY" is always a learning experience, I'd be inclined to purchase something like the "Dog Silencer Max", which may be less $$ than all the parts needed, and has a 45 day return policy.
H. If you have the same results as Freddi, that "design feature" would be very useful :^).

Art
Click to expand...

A. Without going into details of how I "trained" them to respond to me banging on the fence, it's the same technique that I will use to get them to go indoors when ultrasound is switched on. At extreme SPL, that should also drive them indoors when the "owners" are in.

B. By "limited resources" I don't mean money, I mean time and space (cryptic, but nothing to do with Einstein LOL)

C. Nothing in the way under the fence, it's LoS

D. Got it. I'm 90% convinced.

E. 95% convinced.

F. I realise that, but I have a Gould sig gen, and also the circuit-board out of one of those rubbish battery-powered "dog scarer" things

G. Money is not the issue, and I believe that extreme SPL out of the frequency range of adult humans, is the key. In July 2017 I contacted the main "US Inc" provider of "Dog Silncer Max" and although they tried to be helpful and stated its SPL was 115 dB, they could not say at what distance the 115 dB was measured e.g. if it's 115 dB at 25cm, then we're already down to 103 dB at 1 metre, so the "300 ft reach" will likely be less than the SPL of a turboprop aircraft overhead at 5,000 ft. Also, the legal return policy for a distance-seller in the UK is based on "changed your mind", meaning that once the seal is broken and the product has been used, a UK distributor cannot legally re-sell it at retail price, unless they return it to manufacturer for inspection, hence money-back "return if not satisfied" is rare in the UK, and zero if they're a US distributor. If I buy direct from the US shipped to the UK, I have no legal guarantee in any way.

H. Now that I understand the concept of "constant voltage" speaker systems, I'm now thinking of going down the piezo route. But rather than use a single transformer, I'm going to use true double transformers, one at the amp, the other at the piezo, and adjust the tapping(s) to get the max SPL out of the piezo. I'll need 4 transformers, 2 for each channel, but although they won't be on for long, I'd rather get 50 or even 100 Watt rated if possible. Needless to say, their spec has to be up to 20 kHz. !!
 
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