[Jian]

I am doing some experiments with my Sound Lab speakers. Would you please design a crossover for me based upon Mr. Linkwitz's active crossover? I need a one way, high pass at 500 hz, 6 db crossover.

Thank you very much!

[Davey]

A one-way "crossover" is just a filter.  (First order is just a simple series capacitor.)

The capacitor value should be.....1/(2pi * 500 * ampinputR)

Add a shunt resistor in parallel with your amplifier input resistance to "adjust" it so a standard value capacitor is yielded from the computation.

Cheers,

Dave.

[Jian]

Hi Dave!

It is very nice to meet you here!

I didn't state it clearly. I meant to build an active crossover. Sound Lab speakers have two step up transforms. One is for frequency over 500 hz and another one is for under 500 hz. Basically, I am trying to replace the passive crossover with an active one. I will use the active crossover for high/mid step up transform while runing the bass transform full range.

I just bought a cheap dbx 223 to try it out and am going to try it to see if I can get good results. So, I don't need it for now. If the result is promising, I may find better sounding active crossover.

Thanks again!
Jian

[rw@cn]

Hi Dave!

It is very nice to meet you here!

I didn't state it clearly. I meant to build an active crossover. Sound Lab speakers have two step up transforms. One is for frequency over 500 hz and another one is for under 500 hz. Basically, I am trying to replace the passive crossover with an active one. I will use the active crossover for high/mid step up transform while runing the bass transform full range.

I just bought a cheap dbx 223 to try it out and am going to try it to see if I can get good results. So, I don't need it for now. If the result is promising, I may find better sounding active crossover.

Thanks again!
Jian

Have you contacted anyone at Sound Lab ?

[neolith]

For what you want to do, there really is no neded to go to an active 1st order HP filter.  As Davey said you just have to insert a cap in series with the input of the amplifier. The formula at  500 hz simplifies to 318/R nF where R is the impedance of your amp in kOhms. If C is an not a E-12 value, then you can use the next E-12 value above C and calculate a new R (318/C) and then place a shunt resistor in parallel with amp input to change load impedance to match R. The shunt resistor will equal R*Z/(Z-R) where Z is the amp impedance. 
Using a series cap in this manner was what Magnepan did with their XO-1 units for biamping the IIx and early IIIx  speakers.

[Jian]

Thanks neolith! I understand it now.