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Active filter board GB

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cotdt

Member
Joined 2005
Looking at the schematics, I have never seen this sort of arrangement for the HP and LP sections. It seems different from typical LR circuits. Can anyone create an example of a speaker system using these boards? I would rather throw them into the simulation program and tweek it into something I'm happy with than start from stratch. Specifically I want to integrate a set of 10" woofers with my existing 2-way bookshelves, crossover at around 250Hz.
 
JensRasmussen

JensRasmussen

Member
Joined 2002
cotdt said:
Looking at the schematics, I have never seen this sort of arrangement for the HP and LP sections. It seems different from typical LR circuits.
Click to expand...

First of all there is no such thing as a LR circuit. LR is a response of a circuit. Here the topology is an adaptation of the Sallen and Key filter.

It's not really very different from the original design topology, I added an output buffer to enable the builder to select freely between unity gain filters and filters with gain, but without having to think about what happens to signal levels and so on in the filter with gain.

A manual is underway to help the builders get started

To bob: I got your email, but have not had time to read it all yet

\Jens
 
BobEllis

BobEllis

Member
Joined 2003
cotdt - if you are in a hurry, you can visit Jens' site and download the active filter two manual. Go into the tables of values used on page 8 and 9 and choose values to give you the desired response. For a fourth order Linkwitz Reilly response, set the Q of each stage at .71. This won't look like the topology you are used to seeing for L-R, but it will be the same response (try it in a circuit simulator)

You can use the MOX resistor calculations tab of the spreadsheet I posted for frequencies or capacitor values other than those listed.
 
BobEllis

BobEllis

Member
Joined 2003
Scheduled ship date is 29 March. With UPS ground shipping, I expect the boards to arrive here 3-4 working days after that.

There are still a few unpaid orders, I'd appreciate prompt payment or let me know if you are no longer interested. I'll update the WIKI later today to include all who have ordered.

Pinkmouse, I reserved 6 boards for you based on your comments earlier.

If all who expressed an interest still want boards, there are 15 boards available. A few more will be available after everyone who prepaid receives their boards.

I'm still working on a manual. My goal is to have it ready for Jens' review this weekend. He's the real EE, I just stayed in a Holiday Inn Express last night (that is a spoof of a TV commercial for those outside the US)
 
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