Dear diy ERS
This is my first post at the forum . I have a stereo amplifier which I got it from a friend of mine with no brand name all I know is that it a 8ohm transistor amplifier which has a output of 450 w including left and right . I have slowly build up a 3 way system and I have today bought a pair of new piezo tweeters which is a Motorola KSN 1129A . and I have read in the forums that adding a resistor calms them down . out of what I have heard they are the best piezo tweeters. But the problem is I don't know what value of resistor should I add and how to add them. Please excuse me if I have posted in a wrong area I'm basically I am a newbie and I have been a reader of diy audio from a long time . cheers .
This is my first post at the forum . I have a stereo amplifier which I got it from a friend of mine with no brand name all I know is that it a 8ohm transistor amplifier which has a output of 450 w including left and right . I have slowly build up a 3 way system and I have today bought a pair of new piezo tweeters which is a Motorola KSN 1129A . and I have read in the forums that adding a resistor calms them down . out of what I have heard they are the best piezo tweeters. But the problem is I don't know what value of resistor should I add and how to add them. Please excuse me if I have posted in a wrong area I'm basically I am a newbie and I have been a reader of diy audio from a long time . cheers .
Greets!
These normally answers all folk's questions:
Frugal-phile | Piezo Tweeter Crossovers | J Risch
Pulsar Developments Ltd - Piezo Tweeter Application Note
GM
These normally answers all folk's questions:
Frugal-phile | Piezo Tweeter Crossovers | J Risch
Pulsar Developments Ltd - Piezo Tweeter Application Note
GM
Not sure if the same info maybe is in the other links posted, but this seems informative:
Using piezo tweeters wisely: a "how to" - AudioKarma.org Home Audio Stereo Discussion Forums
Using piezo tweeters wisely: a "how to" - AudioKarma.org Home Audio Stereo Discussion Forums
Thanks for the info GM and Kris0603 I went through all the info you guys sent me and I added a 8ohm resistor in parallel and voila ! I didn't go for the 22ohm resistance idea though cause I didn't want to take any sort of risk with the amp or crossover. From the sound quality I hear now I think they are better than the peerless 1inch 8 ohm metal dome tweeter many people recommend. The highs are shrill but in a good way ,instruments like violin sound excellent. Thank you guys for all the help.
I'll ask here rather than open a new thread
Just opened a box I offered to look at
Somebody has "Improved" a standard party speaker until they no longer work.
One speaker has the piezo tweeter shunted with 10W47R the other is miswired with the 10W47R in series with the piezo tweeter
Woofer is run open and a pretty standard cheap 6R 12 inch
New owner does charity gigs at for OAPs so I don't want to do anything that costs him too much.
I was thinking of 4uF and 1R1 in series but should I replace the shunt with a lower value or is 47 Ohms OK?
Just opened a box I offered to look at
Somebody has "Improved" a standard party speaker until they no longer work.
One speaker has the piezo tweeter shunted with 10W47R the other is miswired with the 10W47R in series with the piezo tweeter
Woofer is run open and a pretty standard cheap 6R 12 inch
New owner does charity gigs at for OAPs so I don't want to do anything that costs him too much.
I was thinking of 4uF and 1R1 in series but should I replace the shunt with a lower value or is 47 Ohms OK?
Piezo tweeters do not require any form of crossover due to the attributes of the elements used. It is a good idea, in larger systems, to fit a 24Volt 10Watt bulb in series with the tweeters. This reduces the high power and will reduce the risk of damage to the piezo element. Smaller systems will improve with a 4R7 to 22R0 resister in series, depending on the quantity of tweet required. One can use a 22R rheostat.
I just found an original Motorola document on-line
Tweeter in these boxes is the KSN 1016A
I'd like to give these boxes back "Better" than when made if possible
Some-one tried to make these a 4-way by adding an after market XO and adding in a midrange and a tweeter and stuffed up the wiring
http://linear1.org/i/piezo.pdf
Tweeter in these boxes is the KSN 1016A
I'd like to give these boxes back "Better" than when made if possible
Some-one tried to make these a 4-way by adding an after market XO and adding in a midrange and a tweeter and stuffed up the wiring
http://linear1.org/i/piezo.pdf
The proper use for the 47r resistor is in series with the capacitive (Piezo) tweeter .
resistor in parallel on the other cabinet is obviously a miswiring and does nothing useful, it only sucks power from the amp and turns it into heat.
If the tweeter is too loud , you can pad it 6dB which should be more than enough with a 47r resistor in series and another 47r resistor in parallel with the tweeter.
You could add a switch which connects/disconnects the 47r resistor in parallel with the tweeter, the series one should be always there.
resistor in parallel on the other cabinet is obviously a miswiring and does nothing useful, it only sucks power from the amp and turns it into heat.
If the tweeter is too loud , you can pad it 6dB which should be more than enough with a 47r resistor in series and another 47r resistor in parallel with the tweeter.
You could add a switch which connects/disconnects the 47r resistor in parallel with the tweeter, the series one should be always there.
Yeah, this is the way I've always done piezos. Simple and makes sense to me.
I didn't learn about the technically correct way until I'd been on the net for awhile when Wayne Parham 'corrected' me, but I'm a 'don't fix what ain't broke' kind of guy, so I've never bothered to try it the 'right' way, just post it for others to maintain the status quo.
Nice to know I'm not the only one doing it 'wrong', so thanks for the link!
GM
Well given all of the information received I'm going to wire up as given if the first link [ John Risch] as then all I need to purchase is a 10W22R resistor for the shunt and put the 47R back in series on both tweeters
I'll throw in some batting as well I guess and charge the feller a six-pack
I'll throw in some batting as well I guess and charge the feller a six-pack
Resistors etc
RE - Using piezo tweeters wisely: a "how to" - AudioKarma.org Home Audio Stereo Discussion Forums
The guy in there contradicts himself, first saying resistors are not needed, then admitting they are, on some models. Leaving aside the Powerline ones with built in protection, then ALL others should have an series resistor Directly connected to it/them. Some models had one already fitted. Whether they still do ?
The Original Motorola models included an undocumented 10R 1W carbon resistor under the back cover of for eg KSN 1025A. I discovered this many moons ago whilst examaning one after it stopped working. The resistor had burnt out, but shorting it out brought it back to life. I replaced it with a round 3W wirewound type of the same size, & never had any more problems with it. From then i always replaced them, even if new.
Interestingly, i could hear a small increase in output if i shorted out the resistor on working units, even though in theory you shouldn't be able to.
If you look @ the datasheet http://www.bestgrouptechnologies.com/doc/KSN-1025A-Datasheet.pdf you'll see the fr varies + - 5dB between 2kHz - 20kHz ! And the sensitivity is 90dB - 99dB !
CTS are no more, according to this.
In my experience, Piezos "can" be made to sound ok, if you use a 6dB octave Xover, one capacitor, about an octave above their stated lower fr. For eg, for 1.8kHz = 3kHz & above. But you MUST place an for eg 8R 7W - 10W resistor in parallel with the piezo's terminals, for it to work correctly.
RE - Using piezo tweeters wisely: a "how to" - AudioKarma.org Home Audio Stereo Discussion Forums
The guy in there contradicts himself, first saying resistors are not needed, then admitting they are, on some models. Leaving aside the Powerline ones with built in protection, then ALL others should have an series resistor Directly connected to it/them. Some models had one already fitted. Whether they still do ?
The Original Motorola models included an undocumented 10R 1W carbon resistor under the back cover of for eg KSN 1025A. I discovered this many moons ago whilst examaning one after it stopped working. The resistor had burnt out, but shorting it out brought it back to life. I replaced it with a round 3W wirewound type of the same size, & never had any more problems with it. From then i always replaced them, even if new.
Interestingly, i could hear a small increase in output if i shorted out the resistor on working units, even though in theory you shouldn't be able to.
If you look @ the datasheet http://www.bestgrouptechnologies.com/doc/KSN-1025A-Datasheet.pdf you'll see the fr varies + - 5dB between 2kHz - 20kHz ! And the sensitivity is 90dB - 99dB !
CTS are no more, according to this.
In my experience, Piezos "can" be made to sound ok, if you use a 6dB octave Xover, one capacitor, about an octave above their stated lower fr. For eg, for 1.8kHz = 3kHz & above. But you MUST place an for eg 8R 7W - 10W resistor in parallel with the piezo's terminals, for it to work correctly.
Piezo horns are loud and very harsh, full of phase distortion. That is why disco speakers use them. They are cheaper than compression drivers.
If you use a series resistor, that will cut the sensitivity to the level you want.
Correcting the wiring mistake helped, they sound better returned to a 2-Way then they did as a bad 4-way and the owner was happy. I also got him back a few dB by taking the restrictive coil from in front of the 12inch midwoofer
While it wasn't all fun I learned something and that's important
While it wasn't all fun I learned something and that's important
Now what I did was add a 8ohm resistance in parellel as the XO in my system has a 3.3uf cap for the tweeter. But the problem now is it was working fine for past 3days and now it has a strange issue the tweeter on the left makes a clipping sound when a piano track is played. And this is the only issue. I have swapped the left speakers with right and the same thing happens with right speakers . I have tried everything . cleaning the pots .recapping the amp and cleaning the connectors. Am I doing something wrong with the piezos here ? My only guess is that I should try changing the power transistors on the amplifier. And as soon as I decrease the 500hz band in the equalizer it stops crackling and clipping. So should I just bypass the terminal and attach a .47uf cap to the piezos. Or is there something surely wrong with the amplifier . the amp body has no name . only when I opened the body I saw TRD JDM 3055 450W written on the circuit borad .
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