Step up air coil of the HLQ-02 could be used.
Will bring +10 decibels.
Would be nice to learn how the coil is wired for lowering impedance.
Then you won't need to rob the other driver.
Will bring +10 decibels.
Would be nice to learn how the coil is wired for lowering impedance.
Then you won't need to rob the other driver.
Found a nice discussion already in 2002, Planet 10 mentioning covering paper cones with art metal foil. My words.
https://www.diyaudio.com/community/threads/piezo-vs-voice-coil-tweeters.3005/post-23900
They even wanted to initiate a fan club!
https://www.diyaudio.com/community/threads/piezo-vs-voice-coil-tweeters.3005/post-23900
They even wanted to initiate a fan club!
Sorry, I didn't mean the horn. The piezo I linked ( https://www.parts-express.com/GRS-PZ1188-Piezo-Horn-Driver-Similar-to-KSN1188A-292-450?quantity=1 )
claims -
Specifications: • Power handling: 400 watts max • Frequency response: 800-20,000 Hz • SPL: 93 dB 1W/1m • Dimensions: Diameter: 3-7/8", Depth: 3".
I'm not certain that I believe a piezo will play that low? But I haven't tried one of those 1188 types. Maybe you should give it try and let us know...
Well, no.
Compared to the natural raw response of KSN 1005, serial 33 ohm resistor (without other components from the "ultimate filter"!) is causing only 0.4 - 0.5 dB attenuation between 6 kHz and 10 kHz, 0.8 dB at 16 kHz, 1 dB at 18 kHz - see the picture below.
Somewhat bigger attenuation is happening only at the SPL resonances at 5.3 kHz ( -0.9 dB) and at 13.9 kHz ( -1.1 dB) - which actually is a good thing. Besides, 33 ohm resistor is protecting amplifier from eventual oscillation problems.
Picture below shows high-pass filter frequency response of my "ultimate filter" with 33 ohm resistor (green curve) - there is only 0.3 dB attenuation at 15 kHz and 1 dB at 18.6 kHz. Again, there is beneficiary attenuation of 0.8 dB at SPL peak at 13.9 kHz.
Red curve shows high-pass filter frequency response of the "ultimate filter" if 33 ohm resistor is replaced with 0.1 mH inductor. There is even 1 dB amplification between 10 kHz and 20 kHz due to the resonance between 0.1 mH inductor and capacitance of the piezo disc - not a good thing!
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I agree that the 33ohm resistor can help with regards to an amplifier that has instability problems > But I wouldn't buy or use one.
I beg to differ that the 'super high' frequency gain is a bad thing > This region is where human hearing is usually compromised.
It also adds 'AIR' to the reproduced sound.
A 10ohm resistor is fine, but not 33ohms.
Using VERY fine wire, you can add the inductance + DCR.
PS.
This thread is about "CHEAP PIEZO's" and your referring to a genuine high priced Piezo.
I beg to differ that the 'super high' frequency gain is a bad thing > This region is where human hearing is usually compromised.
It also adds 'AIR' to the reproduced sound.
A 10ohm resistor is fine, but not 33ohms.
Using VERY fine wire, you can add the inductance + DCR.
PS.
This thread is about "CHEAP PIEZO's" and your referring to a genuine high priced Piezo.
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High frequency gain is a bad thing, because it is coming from a resonance - which always is a bad thing.
My "ultimate filter" topology for piezo tweeters can add gain (but that is a bad idea!), simply by choosing different values of the components (or leaving out some components entirely, as 27 ohm resistor) - see the pictures below:
As you can see, I am stubbornly keeping that pesky 33 ohm resistor, but in spite of that, up to 16.7 kHz my ill-modified "ultimate filter" (green curve) has bigger gain than your filter (red curve), adding (according to you) even "more 'AIR' to the reproduced sound".
One more time: avoid gain in passive circuits - at any cost!
My "ultimate filter" topology for piezo tweeters can add gain (but that is a bad idea!), simply by choosing different values of the components (or leaving out some components entirely, as 27 ohm resistor) - see the pictures below:
As you can see, I am stubbornly keeping that pesky 33 ohm resistor, but in spite of that, up to 16.7 kHz my ill-modified "ultimate filter" (green curve) has bigger gain than your filter (red curve), adding (according to you) even "more 'AIR' to the reproduced sound".
One more time: avoid gain in passive circuits - at any cost!
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No, I am not. My "ultimate filter" topology is applicable to any piezo tweeter, including the cheapest one in the world.
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Now found a thread on the topic of using piezo tweeters with a step up winding
https://www.diyaudio.com/community/...use-for-the-8-ohm-primary.412619/post-7681454
https://www.diyaudio.com/community/...use-for-the-8-ohm-primary.412619/post-7681454
Step-up autotransformer is OK, but it advisable to be used with genuine high-pass filter. Otherwise, high voltage low-frequency signal may burn piezo disc, although air-core transformer will attenuate somewhat the low-frequency signal. That is way iron-core autotransformer for piezo is not a good idea with simple high-pass filters - it should be air-cored.
Bifilar winding (two wires in parallel) 1n:3n surely will result in better coupling, but I think autotransformer ("one wire only, one third length...") 1n:3n will be good enough There is a minimum number of n for good transformer action (it depends on impedance), but I don't know it.
As you stated, your ultimate XO was designed with a genuine Motorola in mind.
Regarding very high frequency performance, there is a massive difference between cheap generics and the genuine devise.
Even over-all 'flatness' is poor with cheap generics.
Your 'even more extra gain' (green) example is obviously something neither of us would recommend > I think the red curve speaks for itself.
Regarding small amounts gain generated via resonance > Many thousands of third order filters use resonant gain in the first C/L 'half' and
then use the final capacitor to remove it. Such filters wouldn't be universally accepted if 'resonance' was a 'totally bad and wrong thing'.
Because the actual capacitance of a Piezo element is that of a "Leaky Capacitor" AND using series 10ohms + coil = a poor Q inductor,
the actual gain & resonance IS NOT extreme or objectional.
I actually think your XO/filter is really good > it creates a nice bandwidth that very effectively removes that 'UGLY PIEZO VOICE'.
The whole and only point of me mentioning a .1mH inductor was to address the sound at VERY HIGH FREQUENCIES. It works 🙂
Please define "very high frequency response" - starting from which frequency?
Yes, that is true. But it not negate the usefulness of my "ultimate filter" even for cheap piezo tweeters.
You can't surgically remove one crucial part of the third-order filter to "prove" your point. Good third order passive filter filter is not "resonant" second order filter plus "band-aid" first order filter! Good third order passive filters don't have resonant behavior - that is why they are universally accepted.
Pure C-L (without resistors) second-order filters may exhibit resonance with the inductive voice coil (traditional moving-coil tweeter), but that is easily fixed with resistor in front of C. Voila - bad second order filter turning into a good one!
Even the simple first order filter (single Capacitor) may exhibit resonance when inductive rise of the tweeter voice coil impedance is reacting with that capacitor. Again, it is easily fixed with resistor in series with C.
It is not extreme (+1 dB), but may be objectional. My point is - that rise it is not needed, because piezo tweeters usually have higher sensitivity than typical hi-fi midrange/woofer. You can always leave higher output of piezo at highest frequencies and below that attenuate to level with the midrange/woofer output.
Thanks!
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I DON'T find the gain & 'air' in any way objectionable. ( in actual practice I find the gain to be +2 dB )
Cheap $10 piezos don't really have an efficiency advantage over todays good dynamic tweeters.
You shouldn't solder directly onto the connection pins of a piezo, the heat goes to the piezo element through the leads and damages the crystal, lowering the level or make it fail completely. That's also the reason you should never buy used piezos with soldered connectors.
Hey, I wanted to pop in and post that I have added a notch filter in to the speaker to deal with that 11 or 12 kHz peak. Here's what I did!
I haven't gotten a confirmation measurement yet, but earlier measurements matched XSIM pretty well. I did use a cheap / small inductor for L3 similar to what I linked in post #30, tho it's before R1... I could have gone after R1 and been lower current but needed higher inductance... This seems to work out. I don't notice a difference as a screeching peak, but the speaker does sound a bit more relaxed, I think. Hard to say for sure since the time involved to make the change prohibits a quick A/B listen.
I'll attach the xsim file... Have fun!
- A
I haven't gotten a confirmation measurement yet, but earlier measurements matched XSIM pretty well. I did use a cheap / small inductor for L3 similar to what I linked in post #30, tho it's before R1... I could have gone after R1 and been lower current but needed higher inductance... This seems to work out. I don't notice a difference as a screeching peak, but the speaker does sound a bit more relaxed, I think. Hard to say for sure since the time involved to make the change prohibits a quick A/B listen.
I'll attach the xsim file... Have fun!
- A
@AdamThorne
sophisticated network, showing how piezos can be linearized without dsp.
I use piezos with minimal filtering like 100 ohm across plus and minus and 20 ohms in line with one capacitor to block the lower frequencies.
Together with a fullrange I only test the right polarity and then using rough overall EQ for the most important adjustment.
I am sure piezo drivers can give very decent results. The more so if some damping of the back cavity can be added, too.
For my part I add some thin aluminium covering one sided at the paper cone.
making at the moment a fun box for outside beach parties with a 30cm bass driver converted to fullrange by removing the dustcap and aluminizing the paper cone, too.
wood and work for the boxes are in egypt 50 dollars a pair from the carpenter with full wood 20mm
8cm big reflex port 55cm long in 70 liter enclosure
beach party will be here
sophisticated network, showing how piezos can be linearized without dsp.
I use piezos with minimal filtering like 100 ohm across plus and minus and 20 ohms in line with one capacitor to block the lower frequencies.
Together with a fullrange I only test the right polarity and then using rough overall EQ for the most important adjustment.
I am sure piezo drivers can give very decent results. The more so if some damping of the back cavity can be added, too.
For my part I add some thin aluminium covering one sided at the paper cone.
making at the moment a fun box for outside beach parties with a 30cm bass driver converted to fullrange by removing the dustcap and aluminizing the paper cone, too.
wood and work for the boxes are in egypt 50 dollars a pair from the carpenter with full wood 20mm
8cm big reflex port 55cm long in 70 liter enclosure
beach party will be here
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the aluminium on the piezo paper cone does not change anything concerning its frequency response nor the burst decay. But changes the sound completely for better transients and attack. Never did distortion measurements on this but maybe something can be seen there