Hi,
 
I have one dynamic speaker and one balanced armature.
 
I'd like to cut off HF from dynamic speaker (that will be my bass) and cut LF from BA (that will be my tweeter). Generaly for mid range some from first some from second one.
 
How to calculate what inductor and capacitor I need? 
 
Can I only figure it out from formula using i.e. this calculator? http://www.learningaboutelectronics.com/Articles/Cut-off-frequency-calculator.php
 
I need low-pass and high-pass filters.
 
Thanks for any advice! 

noumen said:

  Hi,
 
I have one dynamic speaker and one balanced armature.
 
I'd like to cut off HF from dynamic speaker (that will be my bass) and cut LF from BA (that will be my tweeter). Generaly for mid range some from first some from second one.
 
How to calculate what inductor and capacitor I need? 
 
Can I only figure it out from formula using i.e. this calculator? http://www.learningaboutelectronics.com/Articles/Cut-off-frequency-calculator.php
 
I need low-pass and high-pass filters.
 
Thanks for any advice! 

Click to expand...

 
I think what you're really looking for is crossover calculations.  Those are easily available for speakers.  Assuming what you describe is analogous to a 2-way speaker, there are several choices:
 
http://www.diyaudioandvideo.com/Calculator/XOver/
http://www.erseaudio.com/CrossoverCalculators/Second-Order-2-Way
http://www.erseaudio.com/CrossoverCalculators/First-Order-2-Way
http://www.erseaudio.com/CrossoverCalculators
 
What you haven't mentioned - which is absolutely critical - is what are the impedances of the two components you're proposing to use?

What you haven't mentioned - which is absolutely critical - is what are the impedances of the two components you're proposing to use?

Click to expand...

Hi, thanks for reply!
 
Impedence for dynamic driver is probably 16ohms, I don't know impedence of aramture drive becouse I did't chose one yet (I will be one from Sonion with good HF response or good HF and mid). For bass I'll use dynamic speaker (If it's beter I can find 8 or 32 ohms dynamic driver).

OK, is this mean that:
 
tweeter will play above 1000Hz, and woofer bellow 1kHz?
 

 
What if ther is no capacitor/indutors. I'll have to round it up or down?

First off, make sure you are using the dynamic impedance of the driver at the cut-off frequency you desire.
If a driver is listed in a catalog as, say, an 8 ohm driver, if you hook up your multimeter across the voice coil,
that is roughly the reading you will get. With the driver playing music, the actual impedance will vary. It can
go as low as the static resistance, but will more likely be several hundred ohms at higher frequencies.
You need to get the impedance plot for the driver and go from there.
Just use the closest standard value (up or down) from your calculated values.

avro_arrow said:

  First off, make sure you are using the dynamic impedance of the driver at the cut-off frequency you desire.
If a driver is listed in a catalog as, say, an 8 ohm driver, if you hook up your multimeter across the voice coil,
that is roughly the reading you will get. With the driver playing music, the actual impedance will vary. It can
go as low as the static resistance, but will more likely be several hundred ohms at higher frequencies.
You need to get the impedance plot for the driver and go from there.
Just use the closest standard value (up or down) from your calculated values.

Click to expand...

I have something like this for dynamic driver. They say it's 16ohms speaker.
 

That's just a graph of it's frequency response.
It doesn't tell you anything about it's impedance characteristics.

avro_arrow said:

  That's just a graph of it's frequency response.
It doesn't tell you anything about it's impedance characteristics.

Click to expand...

On graph DCR: 15 ohms, manufacture provide 16 ohms.

avro_arrow said:

Just use the closest standard value (up or down) from your calculated values.

Click to expand...

 
Is there any difference I use: 10uF -  4, 10, 16 or 35V?
 
i.e. (both are 10uF)
 
this one: http://allegro.pl/kondensator-tantalowy-smd-b-10uf-16v-x10-i5121018343.html
or this one: http://allegro.pl/kondensator-10uf-6-3v-10-x7r-0805-smd-kpl-20szt-i5088800129.html

noumen said:

 

avro_arrow said:

  That's just a graph of it's frequency response.
It doesn't tell you anything about it's impedance characteristics.

Click to expand...

On graph DCR: 15 ohms, manufacture provide 16 ohms.

Click to expand...

 
That's just a label.  What Avro is getting at is that many drivers can have varying impedances, depending on the frequency in the audio band.  For instance, some headphones' plot of impedance vs. frequency may very much more than the graph you showed.
 
For instance, take a look at the "Electrical Impedance and Phase plot on this page:
http://www.innerfidelity.com/images/SennheiserHD650.pdf
The magenta curve is the impedance curve vs. frequency of the HD650 (a dynamic driver).  Notice that at 100 Hz - a point where you might very well want to crossover from a dynamic/bass driver to the balanced armature, the impedance is over 500 ohms.  Try to calculate/design a crossover filter at that point and use the headphone's nominal impedance (300 ohms) and you will end up with a lousy design that doesn't crossover where you want.

tomb said:

   
That's just a label.  What Avro is getting at is that many drivers can have varying impedances, depending on the frequency in the audio band.  For instance, some headphones' plot of impedance vs. frequency may very much more than the graph you showed.
 
For instance, take a look at the "Electrical Impedance and Phase plot on this page:
http://www.innerfidelity.com/images/SennheiserHD650.pdf
The magenta curve is the impedance curve vs. frequency of the HD650 (a dynamic driver).  Notice that at 100 Hz - a point where you might very well want to crossover from a dynamic/bass driver to the balanced armature, the impedance is over 500 ohms.  Try to calculate/design a crossover filter at that point and use the headphone's nominal impedance (300 ohms) and you will end up with a lousy design that doesn't crossover where you want.

Click to expand...

OK, I get it. Thank you for information.
 
Still I have to put some data into calculator to know which capacitor use. 
 
Also question, why cut off at 100Hz? Shouldn't it be 300Hz?
 
Or like this:
 
1. dynamic driver as a bass and mid --> cutoff at 3k, BA as a tweeter
2. dynamic driver as a bass --> cutoff at 300Hz, BA as a mid and tweeter

noumen said:

 

tomb said:

   
That's just a label.  What Avro is getting at is that many drivers can have varying impedances, depending on the frequency in the audio band.  For instance, some headphones' plot of impedance vs. frequency may very much more than the graph you showed.
 
For instance, take a look at the "Electrical Impedance and Phase plot on this page:
http://www.innerfidelity.com/images/SennheiserHD650.pdf
The magenta curve is the impedance curve vs. frequency of the HD650 (a dynamic driver).  Notice that at 100 Hz - a point where you might very well want to crossover from a dynamic/bass driver to the balanced armature, the impedance is over 500 ohms.  Try to calculate/design a crossover filter at that point and use the headphone's nominal impedance (300 ohms) and you will end up with a lousy design that doesn't crossover where you want.

Click to expand...

OK, I get it. Thank you for information.
 
Still I have to put some data into calculator to know which capacitor use. 
 
Also question, why cut off at 100Hz? Shouldn't it be 300Hz?
 
Or like this:
 
1. dynamic driver as a bass and mid --> cutoff at 3k, BA as a tweeter
2. dynamic driver as a bass --> cutoff at 300Hz, BA as a mid and tweeter

Click to expand...

I was only taking a guess at the crossover to illustrate a point.  The use of the word "might" was in there, too.  Please don't take my examples literally.

tomb said:

 
I was only taking a guess at the crossover to illustrate a point.  The use of the word "might" was in there, too.  Please don't take my examples literally.

Click to expand...

Yes, yes, I get it. Thanks once again for teoretical info.
 
So, in this my case manufacture provide 16ohms +/-15% - so i put in the calculator 16ohms, right?

That means it could be as low as 13.6 ohms or as high as 18.4 ohms.  Why not plug those numbers in along with 16 ohms as the baseline?  Then compare how that changes the values of the components in the crossover vs. the changes in the crossover point.  You need to find a calculator where you can also plug in the component values to give a crossover point, or use trial and error.  The idea is to get a feel for how far you'd be off relative to that +or- 15% variance in the driver impedance.  Make the best judgment from there, after you've evaluated all the alternatives - including the worst cases of 13.6 or 18.4 ohms.
 
This is not unlike most engineering design in the real world.  You're not going to get exact values all the time and you have to make a judgment call for what may work best, given the worst case scenario vs. ideal.
 
I have no specific experience in IEM crossover design.  It may be that these difference don't amount to anything significant.  Or, it could be that they are monumental.  You're the one that has to decide.  If you can't, then experimentation is next: try some values and see what you get.  If it doesn't work, try different values.  Analysis can only get you so far, because chances are that you never really know all of the variables.  At some point, you have to build it to find out.