I am owner of a pair of Kirishima with full range Fostex 208 Sigma (older model close to ES-R) but when I had them built I also gave them a tweeter to support the last 3-4000 Hz where the Fostex fail a little (loosing some 6-9 dB over 15500 Hz).
I never put in a capacitor cause the man helping me building them insisted that I should have a complete filter installed dividing the frequencies to each speaker which I have later understood was making my full range more of a two way speaker.
I have later removed the filter since I realized that it was destroying more than it did good so now I am running the Fostex and JBL titanium tweeter in parrallell without any filter at all.
I have thought about i a lot since I have read about Fostex speakers and everywhere I find a cap for the tweeter at about 1-1.5 uF and I want to install that cap so I save the tweeter a little and since it is to support only the last, say 4-5000 Hz I don't have to have the tweeter fighting lower frequencies at all.
My question is how do I know how many uF to use to high pass only the last 5000 Hz?
I have checked a lot of calculators but since they all refer to RC filtering I am in doubt cause I don't need the R (the tweeter is matching the full range speaker just perfect as it is) and if I try using the calculators with R set to zero I get Error as answer so how do I calculate a fair value since Fostex themselves recommend 1-1.5 uF when using their L-Pads?
As I understand the L-Pad is an attenuator (variable resistor) ranging from 0 to 40 dB but what does that mean in Ohms?
Whould like to clear this out so I can put in my cap sooner than later.
I never put in a capacitor cause the man helping me building them insisted that I should have a complete filter installed dividing the frequencies to each speaker which I have later understood was making my full range more of a two way speaker.
I have later removed the filter since I realized that it was destroying more than it did good so now I am running the Fostex and JBL titanium tweeter in parrallell without any filter at all.
I have thought about i a lot since I have read about Fostex speakers and everywhere I find a cap for the tweeter at about 1-1.5 uF and I want to install that cap so I save the tweeter a little and since it is to support only the last, say 4-5000 Hz I don't have to have the tweeter fighting lower frequencies at all.
My question is how do I know how many uF to use to high pass only the last 5000 Hz?
I have checked a lot of calculators but since they all refer to RC filtering I am in doubt cause I don't need the R (the tweeter is matching the full range speaker just perfect as it is) and if I try using the calculators with R set to zero I get Error as answer so how do I calculate a fair value since Fostex themselves recommend 1-1.5 uF when using their L-Pads?
As I understand the L-Pad is an attenuator (variable resistor) ranging from 0 to 40 dB but what does that mean in Ohms?
Whould like to clear this out so I can put in my cap sooner than later.
Use the tweeter's impedance, let's say it's 8 ohms, for R in the calculator.
For a 5kHz crossover, you have C = 1 / [2 X 3.14 X 8 X 5000] = 4uF.
If the levels of the drivers did not match so well, you'd need a resistor
or two to pad down the tweeter, which can affect the calculation.
Lovely, this explenation is just what I have been missing too long. I will get to it directly in the morning, thank you.
A 1.5uF capacitor will pass the frequencies above 15,000Hz to an 8 ohm tweeter.
This is because the reactance of a 1.5uF capacitor at 15,000Hz is 7 ohm, which is a close match for the 8 ohm tweeter.
This is the calculator you need:
Capacitive reactance calculator reactance capacitor frequence - sengpielaudio Sengpiel Berlin
Do not run the tweeter without a capacitor as the low frequencies will damage the tweeter.
An L-pad offers a load of 8 ohm regardless of its setting.
This is because the reactance of a 1.5uF capacitor at 15,000Hz is 7 ohm, which is a close match for the 8 ohm tweeter.
This is the calculator you need:
Capacitive reactance calculator reactance capacitor frequence - sengpielaudio Sengpiel Berlin
Do not run the tweeter without a capacitor as the low frequencies will damage the tweeter.
An L-pad offers a load of 8 ohm regardless of its setting.
It appears that you want to crossover at 15,000Hz, not 5,000Hz as rayma has posted.
It is a 1.5uF capacitor that you need.
Quite right rayma!
And it will be quite a change from running the tweeter full range, as currently seems to be the case!
Quite right rayma! And it will be quite a change from running the tweeter full range,
as currently seems to be the case!
I'll bet that FR tweeter was buzzing and rattling around a bit.
Tnx to all!
I started the morning with the Fellowship of the Ring instead of the speakers (vacation you know) but after lunch I took out the Fostex FE208 Sigma and measured the impedance and got it to 6.8 and 6.7 Ohm respectively.
Used the calculater at (Sample)RC Low-pass Filter Design Tool - Result - to verify that I would need something around 2-2.5 uF to get it to filter from around 10000 Hz.
Checked around in the basement and realized that I did not have anything like that so after some discussion with myself I decided to go for two caps in series and of same make and model.
Took 4 Jansen caps measuring 4.7uF and put them in, two and two, in series to have 2.35 uF which mean in reality that the cut of frequency is rather 9900 Hz and since it is a simple 6 dB slope on that filter it worked out really nice.
Cleaned up the highs and middles neatly and now I enjoy music again but without a lot of muddyness, the whole sound stage cleaned up also.....
Thank you all, I have learnt how to do and why to do...
lesson learned.
I started the morning with the Fellowship of the Ring instead of the speakers (vacation you know) but after lunch I took out the Fostex FE208 Sigma and measured the impedance and got it to 6.8 and 6.7 Ohm respectively.
Used the calculater at (Sample)RC Low-pass Filter Design Tool - Result - to verify that I would need something around 2-2.5 uF to get it to filter from around 10000 Hz.
Checked around in the basement and realized that I did not have anything like that so after some discussion with myself I decided to go for two caps in series and of same make and model.
Took 4 Jansen caps measuring 4.7uF and put them in, two and two, in series to have 2.35 uF which mean in reality that the cut of frequency is rather 9900 Hz and since it is a simple 6 dB slope on that filter it worked out really nice.
Cleaned up the highs and middles neatly and now I enjoy music again but without a lot of muddyness, the whole sound stage cleaned up also.....
Thank you all, I have learnt how to do and why to do...
lesson learned.
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