Hey guys first post.

The issue I have is the only audio output of the sound bar for this TV is
optical and it appears thus far it can only send fixed volume output.
AFAIK I have been through all possible settings that pertain the characteristics of this output. I have also contacted LG support and a helpful tech said this is one of the primary reasons he gets calls and there is no simple solution...Yet.

I had used an optical converter to grab the signal and send it to the powered subs
RCA inputs. If the TV is at 75% volume, all good because the sub blends in very well.

My next option was to try an HDMI audio extractor and I presume the volume stays linear with the TV's sound bar. What I do not recall is if this audio is mirrored and part of the signal stay with the built in sound-bar or does completely extract.

The only next option I can think of is adding an AVR just to control the subs volume.

Can you give us some model numbers?

buzz, it is an LG OLED77W8PUA (it's in the title).


STTtech,
As you have already discovered, there is no way to accomplish what you are wanting to do. There is no factory way to acquire a variable signal anywhere, to run a dedicated sub. Your only recourse, is to install a whole sound system.
I would note that anyone really interested in doing a sound system with an LG OLED TV, would/should not choose the 77" W8 series. As it wasn't really designed with that in mind. You could have gone with the 77" C8 series and lost nothing in picture quality. With the money saved and a more conventional design, it would have been easier to integrate a full sound system. And the results would have still been better than using the W8 sound bar.
Unless the whole 'wall paper' TV thing was the 'cool' factor decision on this - then you have to live with what you get.

There is a way to add a subwoofer to this setup however. but it will void your warranty and not look as nice. Take the W8 sound bar apart, locate the speaker wire going to the internal woofers. Splice in a LOC (Line Output Converter) to give you a variable line level signal to run to a subwoofer.
Sound quality will also suffer a bit going this route, but it will probably sound fine for what you are wanting to do. It is very time consuming and you need to know what you are looking at and understand what you are hooking up. But it can be done.

Another scheme would be to use a TOSLINK to analog converter and an IR controlled analog Level control. You would would want to use a control system that would simultaneously step the LG's Volume and the IR control. This would be very crude because a Volume "step" on the LG would be a different size from a "step" on the IR Level control -- and, there would be no crossover for the signal sent to the subwoofer. Really, this would only be a less expensive variation of the scheme to add an A/V receiver simply to achieve control over the subwoofer level.

Does the subwoofer have a crossover? If so, this will help a little.

Or, alternatively, you could use this:
[Link: russound.com]

Connects via toslink. Learns volume up, down and mute commands from tv remote, which maintains volume control parity. Subwoofer out. Solves problem, maintains warranty.

Available, of course, through my favorite supplier

These are all great ideas, using the sound-bar's speaker outputs and sending them into the sub's speaker level inputs is an approach I did not even consider.
I believe I'm experienced enough to pull this off. Problem is the client would be there watching the entire time and most likely we will have to drill a hole in the sound bar to run the speaker outs... My other concern is how bad will this impact the sound of the sound bar, its already sub-par for such an expensive TV --we can't know until the damage is done.
I used to do this all the time in car audio in the 90's when I was an installer. I do recall being able to hear the degradation of audio--I have to think by now it's better.

Here is the sub we used:
[Link: sunfire.com]


This is not bad either, I think I can just use Snap AV's replica of this amp EA-MINI-3D-35
[Link: russound.com]

Like most subs, the input impedance on the speaker level input on that is 5600 ohms. so the amp and soundbar speakers wouldnt notice the subwoofer at all. There would be no perceivable difference in sound quality or volume.

but you need to make sure whatever you tap into is not crossed over in any way. at least not low pass.

good point. Low end may be electronically limited on a TV speaker.