Is there a way to use the Altec Lansing VS4121 Subwoofer as a stand alone? I adopted the Altec Lansing VS4121 subwoofer but do not have the satellite speakers. I was hoping to just use it as a subwoofer for my TV or to use it in combo with other brand speakers for my computer. Does anyone know how to change the wiring so the subwoofer will work on it's own?

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Normally these low end systems components that depend on each other and cannot be interchangeable from other system. So if one of the components (sub woofer or right control satellite speaker) breaks or gets lost the whole system is unusable...
I was in the same situation. Got a sub woofer from VS4121 without original satellite speakers. I acquired satellite speakers from Altec Lansing 251 which used same connectors but the internal wiring was different and incompatible out of the box. Speakers are also glued together so it is impossible to open without damaging it. Not to mention there is no service documentation anywhere..
But if you like electronics you can try to make something based on the information bellow:
Altec Lansing VS4121 connector pinout
If you take the male connector (from right satellite speaker) and look at the pins and number them first row from left to right pins 1-3, second row pins 4-7, the bottom row pins 8-9 and the circle enclosure as 0
0 - Ground
1 - Speaker Right
2 - Treble (seems just like voltage control but may need to be confirmed: Min=0V; Max=voltage from Volume control Pin 9)
3 - Head Set Right
4 - Bass signal (not sure what the exact original design is as I have not opened the speaker) But seems like they use 50K potentiometer and some sort of RC low pass filter configuration. When potentiometer is set to Min it is shorted with ground. When set to Max it is taking signal from Right and Left Head Set (pins 3 and 5) combined through some larger resistors and low pass filter.
5 - Head Set Left
6 - Ground for Head set (grounds 0 and 6 seems to be connected in the subwofer but within the right satelite speaker they seem to be isolated with separate leads to sub)
7 - Power ON/OFF. When OFF or head set jack plugged = 0V; When ON and head set jack unplugged = 5V
8 - 5V Power in
9 - Volume (min=0V; max=5V). It seems they use 50K potentiometer but probably anything >10k should work.
At minimum for standalone sub woofer you will need to implement:
- Power On.Off (switch between pins 8,7)
- Volume control (50k potentiometer (probably anything beteen 10k and 50k will do)between pin 7 and 0 with variable output to pin 9
- Bass control - join two resistors R (I used 7k) and lets call this join point A. Attach other ends of the resistors to pins 3 and 5 respectively. Attach 50k potentiometer (I used 10k) between point A and ground 0. Attach Variable pin of the potentiometer to pin 4 (Bass input signal). Attach capacitor C between Pin 4 and Ground pin 0 (I used Electrolytic 1uF with negative end to ground) . Resistor R and capacitor C should make simple passive low pass filter (Google for formula) that should bypass anf frequency higher than 80-120Hz to ground and feed frequencies lower than 80-120Hz to pin 4.
PS: I managed to hack 251 control satellite speaker to somewhat work with VS 4121 Subwoofer but that is another subject. All electronic parts were salvaged from old broken TV so total cost was $0 but took several days of tinkering for speakers that I could buy used for $10-20 :)
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