Subwoofer Filter PCB with LFE sensing, EQ sections, 12/24 dB LR cutoff

[Solve]

Hello all,

Here is a LTSpice model for the following filter sections: summing circuit, 4th order Linkwitz Riley filter, 1 EQ section configured as notch filter, Linkwitz Transform section, Allpass section (phase) and an output buffer with volume control.

summing+LR4th+Notch+LTransform+allpass+volbuf.asc

-Simulation from 20-100Hz with 100 sample points/decade

I started building my board but are not to skilled with LTSpice.
If I follow the "Bill of materials" in LTSpice with your model do
i get the standard variable 20-100Hz filter?

[APK]

Hi Mayday

PM Sent

[Mayday]

My boards are sold, they went fast.
As I have a working, but maybe not optimal, solution today, an active x-over for my woofers will have to wait.

[presbel]

Got my boards yesterday. Thanks

[Mfly]

Originally Posted by Solve

I started building my board but are not to skilled with LTSpice.
If I follow the "Bill of materials" in LTSpice with your model do
i get the standard variable 20-100Hz filter?

Sorry for the late response. Been busy . However:

In LTSpice I believe R400, R401, R402, R403 are now 130kOhm? That would result in a filter frequency of ~26Hz. Fill in other values for R4xx and the frequency will change. If you follow the BOM, R4xx is composed of a 30k resistor plus the value of the potentiometer (0kOhm - 100kOhm). This will give you a range of 26Hz (@ 130kOhm) to 113Hz (@ 30kOhm). You can change the range for example from 24Hz to 85Hz by putting in 40kOhm resistors at R4xx.

In LTSpice you have to change the values of the R4xx resistors manually to change the crossover frequency. You can use the calculator at the bottom of the page of project 09 from Elliott Sound Products to easily calculate these values for any given crossover frequency.

Hope this helps!

[Solve]

Thanks!That sure helped.

[Mfly]

Dear all,

I finished my build and got the sensing circuit working as well. Man, I'm glad everything works . Which brings me to the following:

The library part I used for the mosfet in the sensing circuit (Q1) has another pinout than the ZVN4210A part (and the BS170 and BS270 have yet another pinout). So you'll have to swap the pins. When looking at the silkscreen with the potentiometers at the bottom; the left pin is 'source', the middle pin 'drain' and the right pin 'gate'. So for the ZVN2410 you'll have to swap the middle and the right pin. The BS parts you'll have to put in the other way (turn them 180 degrees) and swap the same pins. So please have a good look at the pinout of the device you're using!

Another thing: Because the solder pads are small and the hole diameters are small as well, desoldering of parts is quite the challenge. So if you are not sure about component values (e.g. for the equalizer sections), I would recommend soldering in sockets to place your components. This prevents some frustation when you have to swap parts. These for example: 01-0513-11H Aries IC & Component Sockets

Happy soldering!

[Mfly]

And one other thing:

The momentary switch to release the relay in the sensing circuit (S2) is designed for a 'toggle' type momentary switch (switching between two poles). The part I'm using (and is in the BOM) is a single pole however. To make this work just solder a bridge (or connect another way) between pole 2 and 3 (middle and right pins viewed from the top). Don't forget to do this, otherwise the circuit will never release automatically.

[Solve]

I started to build mine, but if i dont want to use any S3 switch, do i bridge 1-3 and 4-6?
And where are the hole numbers?

[Mfly]

Originally Posted by Solve

I started to build mine, but if i dont want to use any S3 switch, do i bridge 1-3 and 4-6?
And where are the hole numbers?

There are no hole numbers on the silk screen, my apologies for this. You can have a look at the schematic. When not using S3; connect 1+2 and 4+5 for a 0-180 degrees section and connect 2+3 and 5+6 for a 180-360 degrees section. Looking with the potmeters at the 'bottom' and silkscreen on top:

1=top right
2=middle right
3=bottom right
4=top left
5=middle left
6=bottom left