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Grandma's got a Sony Bravia KDL-40L4000 flatscreen TV. For Christmas, we bought her a Logitech X-530 speaker system so she could hear better.

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Now, her TV only has stereo output with 2 RCA jacks (red-white). When I plug them into the speakers, only the two front satellites, the center one, and the subwoofer output sound. The back satellites don't play nothing but tiny noises, like filtered by the speaker system. The TV has no 5.1 output, only 2.0.

I'd like to know if I can build some kind of adapter that would

  1. send left channel from the TV to the front left + back left speakers
  2. send right channel from the TV to the front right + back right speakers
  3. average left+right channels from the TV to the center speaker and to the subwoofer.

Could that be achieved with just a few diodes and RCA jacks?

Like that :

TV LEFT    ------>|------\------>|---- FRONT LEFT
                          \----->|---- REAR LEFT
                          (>)--->|---- CENTER+SUB
                          /----->|---- REAR RIGHT
TV RIGHT   ------>|------/------>|---- FRONT RIGHT

What to put at the (>) "joining point" ? How to wire the grounds?

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is there a amp in the system, that should be able to do the 2->5 conversion? see if the manual says anything about it – ratchet freak Dec 25 '11 at 21:33
The closest I have found in the manual says that if you plug a 2.0 source, it'll do some kind of surround sound effect. That is the awkward "tiny noises" I mention -- I want grandma to hear the voices coming from the back speakers, not only the highest tones of the background music they're currently outputting. So the most evident thing I found is to duplicate "front" to "back". – Cyrille Dec 25 '11 at 21:37
You got just speakers without a amp? My 10 year old Sony amp can take in a RCA source and "surroundify" it. It's not true surround, but then neither is the audio source – Aaron Dec 26 '11 at 16:59
Back in the late 90s, the only music source in my bachelor pad was the built-in sound card in my desktop computer. Sadly, it had artificial "surround" sound, which works by sending the rear channel a copy of what's going to the front channel, but delayed and at reduced volume. This might have been nice for movies and games but was HELL on music. Fortunately, it could be turned off - but it came back every time I rebooted. Eventually I bought a decent sound card. – MT_Head Dec 26 '11 at 23:42
What are you expecting from the rear speakers? Here is a quote from the product site "Your front left and right satellite speakers deliver the soundtrack and most special effects. Dialog and vocals come from the center channel—making it seem as if they’re coming straight out of the screen. The left and right surround speakers add ambient sounds and more special effects from behind you. And the subwoofer brings in the booming bass.". – Tester101♦ Dec 28 '11 at 13:52

closed as off topic by The Evil Greebo, Niall C., Tester101♦, BMitch♦, ChrisF♦ Dec 28 '11 at 19:35

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1 Answer

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There's something in the manual about a videogame console adapter. Try that, assuming it's in the package. You can do a custom adapter like you think you want, but it's a pain in the gluteus maximus with some potentially negative consequences.

Any kind of adapter is going to involve amplification in some way, shape, or form, which is the reason you're getting "tiny sounds" from the current setup - they're actually unamplified signals running into the surrounds and sub, and since the speakers in question expect larger currents than they are getting they are being "underdriven".

Your options are an adapter or a receiver/head unit/amp (same thing in this case). You can make your own adapter, but it can easily get you some blown speakers.

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The manual says there are two kind of inputs: 2.5mm jacks, either a single one (2.0 -- plugged in the "Front" jack) or the three of them (5.1). There's also another input for videogame console: two red/white RCA plugs. I have tried both solutions (single 2.5mm jack or two RCA plugs), the same effect occurs : rear speakers feel underdriven as you say. – Cyrille Dec 26 '11 at 9:53
Is there, or is there not, a console adapter in the box? the manual says there should be. – jamesson Dec 26 '11 at 16:09
There's no adapter. The French part of the manual says that to plug in a console, you need a (not supplied) two-RCA plug. – Cyrille Dec 26 '11 at 19:29
then you need either this adapter or a receiver. You can build a passive amp, but tat's like saying you can theoretically rebuild your own transmission – jamesson Dec 26 '11 at 19:53
If I'm not mistaken, there is an amplifier in the woofer box. I'm guessing the source cable is plugged into the woofer, and all the satellites are controlled from there. – Tester101♦ Dec 28 '11 at 13:56
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