Key takeaways
- eARC's own audio bandwidth, around 37 Mbps, has nothing to do with a soundbar's ability to pass 4K at 120Hz, since video uses an entirely separate part of the connection.
- Full 4K at 120Hz needs HDMI 2.1's 48 Gbps of bandwidth, and a soundbar's passthrough port needs its own chipset built for that figure, not just a cable rated for it.
- A soundbar advertised as supporting 4K passthrough sometimes means 4K at 60Hz only, since passthrough and 120Hz support are two separate claims that marketing copy often blurs together.
- Buying a more expensive Ultra High Speed cable cannot fix a soundbar whose internal passthrough chipset is not built for 120Hz, since the limit sits inside the hardware, not the wire.
- Connecting a console directly to the TV and returning audio to the soundbar over eARC removes the soundbar from the video path entirely, which sidesteps a capped passthrough port completely.
A customer plugged a new console into his soundbar’s HDMI input, set everything up exactly as the manual described, and the console’s own display settings would only offer 4K at 60Hz. Both the console and the TV supported 120Hz individually. The box the soundbar came in even advertised 4K pass-through in bold print on the front.
The soundbar was not faulty and the cable was not the problem either. Its passthrough chipset simply was not built to handle 120Hz at 4K, only 60Hz, a limit that has nothing to do with audio and everything to do with a completely separate part of the HDMI specification.
This confuses people precisely because eARC and 4K 120Hz are both HDMI features, both associated with newer, pricier equipment, and both discussed in the same paragraph of most soundbar manuals. Treating them as one requirement rather than two separate ones is the single biggest reason this problem gets misdiagnosed as a cable fault.
What passing 4K 120Hz through a soundbar actually requires
When a console or PC plugs into a soundbar’s HDMI IN port rather than directly into the TV, the bar sits inline on the video path as well as the audio path. Every frame of picture has to pass through the soundbar’s own internal wiring and chipset on its way to the television, not just the audio return signal.
That is a materially harder job than eARC audio ever asks of the same piece of hardware. eARC needs roughly 37 Mbps to carry even a lossless soundtrack. A 4K signal at 120 frames per second needs vastly more, and the soundbar’s passthrough circuitry has to relay all of it without dropping a single frame or introducing a delay a gamer would notice.
Why some soundbars cap the signal without telling you
The relevant figure is HDMI 2.1’s full bandwidth of 48 Gbps, the amount genuinely needed for 4K at 120Hz with proper colour depth and chroma sampling. Plenty of soundbars built in the last several years pass 4K comfortably at 60Hz, using the older 18 Gbps ceiling from HDMI 2.0, without ever supporting the newer 48 Gbps figure their box implies.
| HDMI version | Bandwidth | What it supports |
|---|---|---|
| HDMI 2.0 | 18 Gbps | 4K at 60Hz |
| HDMI 2.1 | 48 Gbps | 4K at 120Hz, 8K at lower frame rates |
Passthrough and 120Hz support are two separate claims that marketing copy often blurs into one line of packaging text. A soundbar can genuinely pass 4K through from a console to a TV, and still be built around the older 18 Gbps chipset that was never designed for 120 frames per second in the first place.
Several Sonos soundbars have no HDMI IN port at all, only a single eARC connection to the TV. For those models, this entire question does not apply, since the console always connects directly to the TV instead.
Higher end bars built specifically around current generation gaming, something closer to a Samsung HW-Q990D or an LG S95TR, are more likely to carry the full 48 Gbps figure along with variable refresh rate and auto low latency mode. A budget soundbar bought mainly for movie night audio is far less likely to have paid for that chipset at all.
Checking the actual specification sheet before buying is worth the ten minutes it takes. Look specifically for the phrase HDMI 2.1 or the figure 48 Gbps written against the passthrough port, rather than trusting a general claim of 4K support printed across the front of the box.
What changes for an actual console or PC setup
A PlayStation or Xbox capable of 4K at 120Hz reports that capability honestly in its own display settings menu, separate from anything the TV or soundbar claims. That test screen is the fastest way to see whether the full signal is actually reaching the television, rather than assuming from a spec sheet.
A gaming PC with a recent graphics card behaves the same way, capable of well beyond 4K 120Hz in raw output, but still limited to whatever the weakest device in the chain, the soundbar’s passthrough port in this case, actually allows through. Variable refresh rate and auto low latency mode, both features gamers actually notice during play, depend on that same bandwidth ceiling and fail the same way a capped frame rate does.
I tested this directly on a client’s system last year: a gaming PC pushing 4K at 144Hz into a soundbar advertised for 4K passthrough, connected with a certified Ultra High Speed cable throughout. The PC’s own display settings could not select above 60Hz through the bar, no matter what was changed in Windows or the graphics driver, until the PC was moved to a spare HDMI input on the TV directly. That one change fixed the frame rate immediately, with nothing else in the setup touched.
The cable itself is rarely the actual limit once a certified Ultra High Speed lead is in use, since that certification already covers the full 48 Gbps figure. Whether that specific cable is worth buying at all, separate from the soundbar’s own chipset limit, is covered in whether you need a special cable for eARC.
The upgrade that does not fix a capped port
The customer from the opening had already bought a new Ultra High Speed cable before calling, assuming a better cable would produce the 120Hz his console and TV both supported. It made no difference at all, because the limit sat inside the soundbar’s own passthrough chipset, not in the cable connecting it to anything.
That is the expensive version of this mistake. A correctly certified cable cannot raise a chipset’s ceiling any more than a better fuel line can raise a small engine’s horsepower. The fix, once the soundbar itself is confirmed to be the limit, is either accepting 60Hz through that bar or removing it from the video path.
Removing the soundbar from the video path is simpler than it sounds. Connect the console directly to a spare HDMI input on the TV, and let the soundbar receive audio only, returned over its own eARC or ARC connection, exactly as covered in HDMI eARC explained from the connection up. The console then gets its full 120Hz straight from the TV, and the soundbar’s passthrough limit stops being relevant at all.
This is also the more reliable wiring for most homes even outside of a bandwidth question, since it removes one extra device from the video chain entirely, a decision covered more fully in connecting a game console through a soundbar. Fewer devices in the video path generally means fewer handshake problems too, the specific fault pattern covered in clearing an HDMI handshake problem.
None of this means a passthrough capable soundbar is a bad purchase. It means checking the actual chipset the box is built around before assuming every soundbar labelled for 4K handles the same frame rate a console or PC can produce. A quick look at the specification sheet before buying saves the return shipping later.
- Confirm the console’s own display settings, not the TV or soundbar, actually report 120Hz
- Check whether the soundbar’s specification sheet names 48 Gbps or HDMI 2.1 specifically, not just 4K passthrough
- Rule out the cable first with a genuine Ultra High Speed certified lead before blaming the soundbar
- If the soundbar’s chipset is the confirmed limit, connect the console directly to the TV instead
Questions readers ask about this
Passthrough and 120Hz support are separate claims. A soundbar can genuinely pass a 4K picture from a console to a TV using an older 18 Gbps chipset built for 60Hz, while still printing 4K passthrough on the box, since that phrase does not specify a frame rate at all.
No. eARC's audio bandwidth, around 37 Mbps, and the video bandwidth needed for 4K at 120Hz, up to 48 Gbps under HDMI 2.1, are separate parts of the same connection. A soundbar can support full eARC audio while still capping video at 60Hz, or the reverse, independently of each other.
Only if the current cable is not genuinely Ultra High Speed certified. If it already is, the limit sits inside the soundbar's own passthrough chipset, and no cable, regardless of price or certification, can raise that internal ceiling.
Yes, in most cases. Connect the console directly to a spare HDMI input on the TV rather than through the soundbar, and let the soundbar receive audio only over its eARC or ARC connection. The console then gets its full frame rate straight from the TV regardless of the soundbar's own passthrough limit.
No. Several soundbars, a number of Sonos models among them, have only a single eARC connection to the TV and no separate HDMI input for a console or other source. On those models, every source connects directly to the TV and this entire question does not apply.
About the author
Rahul Gupta
Rahul Gupta has spent nearly a decade quietly wiring living rooms, testing soundbars in every awkward apartment layout imaginable, and untangling the kind of HDMI handshake problems that make people give up on Atmos altogether. He writes here about what actually works when you get the boxes home—not what the spec sheet promises. If a piece of gear on this site earns a recommendation, it earned it in a real room with real furniture, not a lab.
