Audio Corruption on KEF LS50 Wireless II via RAAT (ref#1JKPTU)

[fruity-crux-6p]

Hi! What’s not quite right with Roon?

· None of the above quite fits

None of the above quite fits

· None of these quite match

Tell us what's going on

· Hi Roon Support,

I’m experiencing a new reproducible playback issue between Roon Ready RAAT and my KEF LS50 Wireless II speakers.

System details:

Roon Server: v2.66 build 1658 Production
Roon Remote: v2.66 build 1658 Production
Core running on Mac mini
Endpoint: KEF LS50 Wireless II (Roon Ready)
Network: wired LAN via UniFi
Speakers firmware current
TIDAL connected

Symptoms:
Certain TIDAL FLAC/MQA tracks played via the KEF Roon Ready endpoint exhibit severe audio corruption:

phasey / reverberant vocals
“gargling” artefacts
rattling/distorted presentation

Example track:
Sky at Night from Northern Skies by I Am Kloot

Isolation tests already performed:

Same track plays correctly:
via KEF app directly from TIDAL
via Roon to headphones on local Mac output
via Roon → AirPlay → KEF LS50 Wireless II
via Spotify Connect to the KEFs
Problem ONLY occurs via:
Roon Ready RAAT endpoint to KEF LS50 Wireless II

Troubleshooting already attempted:

Restarted Roon Server
Restarted RAATServer
Restarted KEF speakers
Disabled/re-enabled KEF endpoint in Roon
Signed out/in of TIDAL
Set KEF device in Roon to “No MQA support”
Disabled MQA core decoder
Reduced max PCM rate to 96kHz
Tested with and without KEF Phase Correction
Verified issue persists only on RAAT endpoint

Additional observation:
Even after disabling MQA support in Device Setup, the live Signal Path intermittently continued to display:

MQA core decoder
MQA renderer
MQA signaling

The Signal Path UI appeared to mutate dynamically while expanded, which seemed abnormal.

This strongly suggests a RAAT negotiation/capability issue specific to the KEF Roon Ready implementation rather than:

the audio file
TIDAL source
speaker hardware
network stability
or general DSP issues

Given that:

AirPlay to the same KEF endpoint works correctly from Roon
Native KEF/TIDAL playback works correctly
only RAAT playback is corrupted

…the issue appears isolated specifically to the Roon Ready RAAT path with the LS50 Wireless II.

Please let me know if diagnostic logs would help.

Tell us about your home network

· unifi dms. all cat 6 wired

[vadim]

Hi @fruity-crux-6p, welcome to the community. The fact that this only happens over Roon Ready RAAT, and not via AirPlay or the KEF app, makes this a useful case to dig into on the Roon side.

There are two things I’d like to check next:

• In Roon, please open the KEF zone’s Signal Path and let us know exactly what it shows when the corruption is happening, especially whether any DSP is active and whether the path changes as you expand it.
• Please note the exact local time and date of the next affected track playback, along with the track name, and send that back here. We’ll enable diagnostics on your account so we can review the RAAT negotiation around that window.

One more useful detail: what is the exact model of your UniFi gateway or router, and is the Mac mini connected directly to the switch or through any intermediate network gear?

Once we have that, we can compare what Roon is reporting against the playback path and see where the corruption is being introduced.

[fruity-crux-6p]

N.B. MQA disabled. All diagnostics (reboot/relogin) performed and still shows this path
another example now playing swords - leftfield, rhythm and stealth - same path, same problem

Mac mini is connected to UDM SE via USW pro max (2.5gbe wired)

[alex_h (Alex)]

Hi @fruity-crux-6p,

Thank you for providing the screenshot of your Signal Path! This details exactly what is happening under the hood, and it gives us a very solid lead.

Looking at the Signal Path, we can see a clear conflict in how the MQA stream and the speaker’s internal DSP are interacting over RAAT.

Even though you have MQA disabled in the device settings, Roon is still running the MQA Core Decoder, followed immediately by the KEF Wall Mode DSP (kef_wall_mode).

In a standard deployment, applying any DSP or volume adjustment modifies the audio data, which should break the MQA chain.

However, Roon is still sending this stream over the network with an active MQA flag (IsMqa=True), causing the KEF speakers to activate their MQA Renderer on a modified PCM stream.

This desynchronization is almost certainly what is causing the “gargling”, phase shifts, and audio artifacts you are hearing.

To help us definitively isolate this bug, could you perform a quick 10-second test for us? We want to completely strip the MQA signaling from the stream before it reaches the KEFs.
Here is what to do:

1. Open the Signal Path for your KEF zone in Roon.
2. Click on MUSE (or DSP settings).
3. Enable Sample Rate Conversion.
4. Set the Configuration to Custom and force the output to a fixed rate, for example, 192kHz (or choose Max PCM Rate - Power of 2).
5. Play one of the affected tracks (like Sky at Night or Swords).

What this test does: By forcing a fixed PCM upsampling in MUSE, Roon will completely overwrite and strip out any residual MQA signaling flags.

The KEFs will receive a pure, heavy PCM stream and won’t attempt to engage the MQA Renderer.

Please let us know: Does the audio distortion completely disappear when this setting is active?

Your feedback on this will allow our engineering team to pinpoint exactly whether the issue lies in the RAAT flag handling or the KEF firmware’s renderer negotiation.

Looking forward to your results!

[fruity-crux-6p]

Hi Alex, yes. Audio distortion disappears with sample rate conversion of Max PCM rate (power of 2)
Lee

[vadim]

Hi @fruity-crux-6p,

Thank you for confirming — this is exactly the result we were hoping for!

The workaround is solid: enabling Sample Rate Conversion (Max PCM rate - Power of 2) in MUSE strips the MQA signaling from the stream entirely, so the KEF receives a clean PCM signal and the distortion disappears completely.

You can save this as a preset in MUSE so it applies automatically to your KEF zone every time — no need to think about it again.

Your workaround settings:

• MUSE → Sample Rate Conversion: Enabled
• Configuration: Max PCM Rate (Power of 2)

Thank you for the incredibly thorough troubleshooting you did upfront — it made isolating this so much easier. Enjoy the music!