Hi there,
First of all I havn't posted on this forum since 5 years. Lot's of things have changed around here ( for the best).
I have more free time ( Even with newborn 2 kids ) and I dug all my vintage full rangers off the closet.
Now......
I mounted myself some bookshelf OB's with a nice full range.
Since the fullranger goes to 15khz I created a "PHY HP" tw-37 "clone" with a motorola piezo.
Now... the question part:
I dont seem to get any serious frequency response changes when using different crossovers.
First: Here's the frequency reponse of the driver with no crossover.
NO XO: http://tinyurl.com/3zhs9k
Then the conventional 20 ohm resistor across piezo terminals and a small cap (5.3uF) , to roll off at 15khz. That should be a first order 6 db per octave roll off.
Here's the Frequency response.
6DB XO: http://tinyurl.com/4kh8kq
Then, seeing it did not do the job (I want 15KHZ!!!!) I did a 12db/octave at 15khz.
It was done using a 8ohm resistor across the piezo terminals because I only had those coil valus off hand. caps is 6.6uF and coil is 169 uH
Here's the Frequency response.
12DB XO: http://tinyurl.com/5x9h6q
Now... does anyone see anything wrong?
I'm about to get angry and start creating gainclones and active crossovers.
Thanks for any input on this issue.
First of all I havn't posted on this forum since 5 years. Lot's of things have changed around here ( for the best).
I have more free time ( Even with newborn 2 kids ) and I dug all my vintage full rangers off the closet.
Now......
I mounted myself some bookshelf OB's with a nice full range.
Since the fullranger goes to 15khz I created a "PHY HP" tw-37 "clone" with a motorola piezo.
Now... the question part:
I dont seem to get any serious frequency response changes when using different crossovers.
First: Here's the frequency reponse of the driver with no crossover.
NO XO: http://tinyurl.com/3zhs9k
Then the conventional 20 ohm resistor across piezo terminals and a small cap (5.3uF) , to roll off at 15khz. That should be a first order 6 db per octave roll off.
Here's the Frequency response.
6DB XO: http://tinyurl.com/4kh8kq
Then, seeing it did not do the job (I want 15KHZ!!!!) I did a 12db/octave at 15khz.
It was done using a 8ohm resistor across the piezo terminals because I only had those coil valus off hand. caps is 6.6uF and coil is 169 uH
Here's the Frequency response.
12DB XO: http://tinyurl.com/5x9h6q
Now... does anyone see anything wrong?
I'm about to get angry and start creating gainclones and active crossovers.
Thanks for any input on this issue.
A piezo-elecric driver's reactance is capacitive in nature, so it will not simply act as a uniform load to the 1st order filter - as might a moving coil do, more or less.
20 Ohm + 5.3 uF gives a -3dB point at 1500Hz. (ignoring the reactance of the piezo element at 1.5kHz whatever that might be, but its not going to be realy small)
20 Ohm + 5.3 uF gives a -3dB point at 1500Hz. (ignoring the reactance of the piezo element at 1.5kHz whatever that might be, but its not going to be realy small)
Thank you for the reply Steerpike,
I based my calculations on these piezo application notes:
http://www.pulsardevelopments.com/products/detail/piezoan.html
These are the same as provided by CTS I think.
Any references to calculation formulas taking the capacitive nature of the piezo in account?
[EDIT] I'm sorry on the original post I wrote 5.3 uF when I meant 0.53uF [/EDIT]
I based my calculations on these piezo application notes:
http://www.pulsardevelopments.com/products/detail/piezoan.html
These are the same as provided by CTS I think.
Any references to calculation formulas taking the capacitive nature of the piezo in account?
[EDIT] I'm sorry on the original post I wrote 5.3 uF when I meant 0.53uF [/EDIT]
http://www.zillaspeak.com/Crossover.asp
I think you need to be using smaller capacitor values. Hope the chart above helps.
Godzilla
I think you need to be using smaller capacitor values. Hope the chart above helps.
Godzilla
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.