Subwoofer Filter PCB with LFE sensing, EQ sections, 12/24 dB LR cutoff - Page 3 - diyAudio
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Old 12th December 2011, 04:45 PM   #21
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Location: Metro Washington DC
Originally Posted by Mfly View Post
Finally got some time to work on the board... Sorry for you people who have been waiting.

I've added a rumble filter and a phase switch. I also moved the power input to the top of the board. I have decided to keep the equalizer sections as they are, because they have more flexibility for adjustment compared to a parametric equalizer and take a lot less space on the control side. A subwoofer will probably be in the same room for a long period of time so there shouldn't be any need for continuous adjustment.

I am now almost finished with the board, have to find a solution for 1 trace and do some error checking.

I'll upload the new schematics and board in the coming weeks (before the end of the year, I promise!). I will also collect all calculation tools for the equalizer, linkwitz transform, etc.

For people still waiting, thank you for your patience!
Thank you!
"All measurements are wrong! Thus, measurement is the art of handling errors."
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Old 31st December 2011, 01:48 PM   #22
Mfly is offline Mfly  Netherlands
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Location: Utrecht
All right, still a few hours left till new years...

Here we go:

The new schematic. Changes:

-full phase switch (for > 180 degrees control)
-rumble filter

Subfilter Schematic.jpg

New top layer:

Subfilter Top.jpg

New bottom layer:

Subfilter Bottom.jpg

Calculating tools:


There are 2 spreadsheets in the zipfile, one is called 'Linkwitz Transform Calculator', this is a handy little tool I found to calculate the possibilities for the Linkwitz Transform section. This includes effect of the rumble filter, needed power, Xmax, and so on (credit to Mr. Linkwitz and mr. John L. Murphy).
The other is called 'Active Filter Four'. The sheet 'Notch and boost EQ' contain 2 different tools for calculating the equalizer sections (credit to mr. Bob Ellis).

Then there is the LFE sensing circuit. This is a design by mr. Rod Elliot, for a full explanation of the circuit, including values for timing:

Signal Detecting Auto Power-On Unit

Any other changes you would like to implement (range of the low pass section or range of the phase section), there are several tools easily found on the internet. I maybe have a LTspice model somewhere for the phase section. Let me know if I need to look it up.

I am still thinking about a solution to do the power supply lines all from the top part of the board, but haven't thought of something satisfying yet. If I think of something soon I'll let you know. Otherwise I'll go with this design (if any of you don't find any errors..)

Happy new year everbody!
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Old 5th February 2012, 01:55 PM   #23
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I hope this will turn into a GB...
"All measurements are wrong! Thus, measurement is the art of handling errors."
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Old 8th March 2012, 06:05 PM   #24
Mfly is offline Mfly  Netherlands
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Well, if nobody finds any serious issues with the design. I think this will be the final version.


-Better power supply lines (shorter and all from the top)
-Option for larger output capacitor (Wima MKS type (larger just wasn't an option on this board))
-Made it possible to use both types of EVOX capacitors for C700 (10mm base and 15mm base)
-Options for both Bourns 90 series, as well as 91 series for the phase and volume control (and many others if you put them off board of course)(the Bourns 904 for the filter frequency is still the only ready available 4-gang pot I have found so far)
-Removed the via and found an on board solution

The Top:


The Bottom:


I have a BOM with Mouser part numbers. I'll clean it up and upload it.

And I'll PM people who have shown interest, see who's still interested and get a quote for production. Everybody else interested: feel free to show your interest here or via a PM.

By the way: no matter what the volume, I will order this board .
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Old 8th March 2012, 06:39 PM   #25
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Location: Fort Worth , Texas , USA
Hi , I'm in for 2-4 depending on final outcome, Kind Regards , dean
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Old 8th March 2012, 08:38 PM   #26
Nisbeth is offline Nisbeth  Denmark
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Interested as well, one - three boards depending on price.

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Old 8th March 2012, 08:45 PM   #27
Ryssen is offline Ryssen  Sweden
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Location: Sweden--> Here
Interessted in 1 maybee 2
Regards Åke
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Old 8th March 2012, 09:05 PM   #28
parb is offline parb  United States
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im interested in 2 boards.
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Old 8th March 2012, 09:35 PM   #29
F1 FAN is offline F1 FAN  Canada
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Interested in 1 price dependant.
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Old 8th March 2012, 09:51 PM   #30
Bikeman is offline Bikeman  Australia
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I'd be interested in 2 boards


Mmmm, bike!
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