potential of the ksn1005?

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Just to share some thoughts about xover for the motorola/csn ksn1005

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.


I'm planning some PA monitor with this piezo and bg20 driver from visaton where i would cross them at 5k since bg20 altough tehnically a fullranger isn't very well behaved above this and cuts off at about 10k anyway.

So I'm collecting some input here regarding the crossover for the 1005 - could the above scheme work in practice?

Normally the 1005 is thought of as very harsh sounding what can be credited to that nasty 5dB peak at 5k due to cone resonance.

The above graph shows response w/ and w/o crossover simulated in BoxSim software (kudos to UweG btw.)

I'm gonna try this out anyway when I will be building the boxes (can't really object the $10 cost if it doesn't work out) but I would like to hear your thoughts about this (has anyone attempted something similar)
 
looks good - nice software. a stepup transformer can be used to improve sensitivity. IIRC KSN1016 had ~ 1/4 of 1% HD with 5029Hz sine and ~100-103dB output

can you make a nice "helper tweeter" crossover for coming in around 7-11Khz which removes the 5Khz bump?

I didn't try a 2nd order highpass - that might help protect things

An externally hosted image should be here but it was not working when we last tested it.
 
I've been fidling around with LRC values in Boxsim and came up with this design
1. 30 Ohm paralel
2. series resonant circuit L=0.47mH C=3.3uF R=2Ohm connected PARALELL to the tweeter
3. 0,68 uF cap series to all this

It does not remove the bump completely but pushes it 15 dB down.
-3dB point is around 8500 Hz
around 10k is 0 dB

after 8k it rolls of 12 db/oct
and after 5k around 25 db/oct due to combined natural roll off

the sensitivity is 94,5 dB, you can reduce this 6dB by adding series 0.13uF cap to the tweeter - with bigger values you reduce it less -this doesn't affect overall response



All of this is assuming this simulation works correctly, than we will both be happy with our motorolas
 
sreten said:
Hi,

A thorough understanding of the wiki on piezo's will help with c/o design.

http://www.diyaudio.com/wiki/index.php?page=piezoXO

Crossing over capacitive loads is not intuitive, e.g. using capacitors as attenuators.

:)/sreten.

Yes, thanks but I've read that allready. I have that motorola's pdf about piezos usage. But it doesn't say anything about using inductors in piezo x/o. I suppose a piezo output depends on rms voltage aplied to it, that is absolute value of complex and real parts of it or V*cos(phi).

Anyway, the resistor voltage divider im my circuit makes the piezo act as purely resistive load with very little reactance so I guess that from that on you can use any standard crossover designs on it. And 1005could use some.
 
:confused: What? What's up with the offensive attitude?

I'm no loudspeaker acoustics specialist, but as a electronics engineer i think i have some insight into LRC networks which include crossovers.

Anyway, inductors are nothing new to the piezos, even some factory models have transformers in them akin to what freddi showed.

I'm looking here for what other people's expeirience with the 1005 or similar were like and whenever has someone tryed x/o like this and with what results.
 
Hi,

I did not intend to come across as offensive.

How to deal with the peak before roll-off is decribed in the Wiki,
and the expense of inductors / transformers is not really needed.

A "standard" c/o would need 8 ohm loading - and presumably someway
of adjusting driver level - neither of which the shown circuit offers.

:)/sreten.
 
sreten said:
Hi,

I did not intend to come across as offensive.

How to deal with the peak before roll-off is decribed in the Wiki,
and the expense of inductors / transformers is not really needed.

A "standard" c/o would need 8 ohm loading - and presumably someway
of adjusting driver level - neither of which the shown circuit offers.

:)/sreten.

I tryed running the sim with various x/o mentioned in the link, and while with corect cap values i could make the 5k bump smaller, it never quite did go away completely. But I'll trust you on this, and since i have no means to measure the actuall response with different x/o, so i must relly on simulation to get something usable, and get it cheap.

Looking at the various csn piezo's response curves i've come to conclusion that 1005 can be made the most flat above 5k.

Can you suggest me another piezo with decent response from 5k and if possible lower?. I'm not looking at a serious output here, about 50W max. so Powerline series would be an overkill for this applic.



Cal Weldon said:
A very interesting thing happens when you run a 2 mH inductor in series, yes series, with a piezo. Try hooking one up and you'll see what I mean. It's a little different than you'd expect.

Are you trying to get me to fry my amp? :D
C'mon thats not even funny.
 
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I have used KSN 1188 on CT 1955 horn with 4,7uf series, next 20R shunt, next 10R series to piezo. Mated well with some 12inch 300W Peavey. Tried a shunt coil also just after the cap but proved cutting sensitivity even more, when power handling was robust already. No adverse effects in using it in that system though, just too much.
 
I'll be using some unused 40W amp module in the speaker, and decided to go with biamping since the amp is stereo and the other channel would othervise be wasted. The sensitivity is of less importance then since one channel can easly be turned down.

BG20 is really causing me trouble in the upper end, it's difficult to cross it over properly without it invading in tweeters range and at the same time retaining enough midrange.

I would go with any other (cheap) piezo if it can go low enough to cross it with bg20 at 3k and can be made flat with relatively simple crossover.
 
The bump is caused by cone resonance at around 5k. IMO loading it with different horns or even making the cone heavier by coating i with something would allow us to shift the resonance peak down, possibly extending the usable range down, but also (in case of coating) increasing the peak itself a few db. It's really up to the experimentation , and i would love to do it, if id have the measuring equipment (MLS) to do so. Thats also why i dont use the KSN1188 or any other separate driver/horn combination since differnt horn affects the response differently, and there's no way i could mate it to the BG20 without measurring it first.

The bumpy nature of the piezos is IMO caused by low amount of negative electromechanical feedback that piezo crystal provides, so at the resonance freq. cone rings almost freely, hence the 'bump'.

The lack of literature on this subject also puzzles me somewhat, at this point the piezo research seems to be on the level the conventional speakers were in the '60's
 
I don't like piezos but I can tolerate them if I use the choke.

Low Rider said:
Are you trying to get me to fry my amp?

I'm not smart enough to know if it's a problem to an amp. I run the choke to the piezo paralleled with a standard motor driver (PA type) with it's own smaller choke. No other XO components. Is that a problem?

Plus or minus on the 2mH according to your tastes. This is subjective testing, as we're discussing piezos here.

Your immediate thought might be what can that possibly do to improve the sound? Or why did he even try that? Can't answer on either count, I'm not technical.

Try it. You might be surprised.
 
Cal Weldon said:
I don't like piezos but I can tolerate them if I use the choke.



I'm not smart enough to know if it's a problem to an amp. I run the choke to the piezo paralleled with a standard motor driver (PA type) with it's own smaller choke. No other XO components. Is that a problem?

Plus or minus on the 2mH according to your tastes. This is subjective testing, as we're discussing piezos here.

Your immediate thought might be what can that possibly do to improve the sound? Or why did he even try that? Can't answer on either count, I'm not technical.

Try it. You might be surprised.

Hello. I thought that was tongue-in-cheek, since 2mH choke+ .15 uF cap like the piezo would push the amp into oscillation around 10k
in microseconds and, if theres no short-circuit protection, let it's output stages blue smoke out :)

I'm not sure what would running the piezo parallel to bass speaker's choke do, but if it sounds good without causing trouble for the amp, why not?
 
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Low Rider said:
The bump is caused by cone resonance at around 5k. IMO loading it with different horns or even making the cone heavier by coating i with something would allow us to shift the resonance peak down, possibly extending the usable range down, but also (in case of coating) increasing the peak itself a few db. It's really up to the experimentation , and i would love to do it, if id have the measuring equipment (MLS) to do so. Thats also why i dont use the KSN1188 or any other separate driver/horn combination since differnt horn affects the response differently, and there's no way i could mate it to the BG20 without measurring it first.

The bumpy nature of the piezos is IMO caused by low amount of negative electromechanical feedback that piezo crystal provides, so at the resonance freq. cone rings almost freely, hence the 'bump'.

The lack of literature on this subject also puzzles me somewhat, at this point the piezo research seems to be on the level the conventional speakers were in the '60's

-Don't think that you can predict the response based on published measurements on some IEC baffle (maybe) for any driver. Horn loaded or not, the moment you mount it on something else than where it was tested for reference, you get another story. Measurement gear is a must if you want real control.
-On top of their piezo resonance physics they are living in little plastic compression chambers full of gremlins. Piezo done in luxury can be PHY. They are conceived as cheap jobs, so they carry sins. That said, if treated with respect they can give very robust, dirt cheap and surprising results.
 
Quoting Low Rider "I'm not sure what would running the piezo parallel to bass speaker's choke do, but if it sounds good without causing trouble for the amp, why not?:

Low Rider. I don't think that's what Cal meant, but it's not a bad idea. The high Z of the tweeter won't effect the crossover much, even with a 22 ohm shunt. Peerless and SEAS have used series crossovers.

I have no absolute proof, but I think the piezo element has a series R component. One would think Cal's method would produce a peak at 10K, and, as you suggest, a difficult load to drive.

What Cal has noticed, could be due phase correction.

regards,
Geoff.
 
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