Mark Levinson 21-speaker audio sounds terrible on the GX 550 Luxury + (4 Viewers)

[oldseniu]

Over the last few days, not sure if my speakers "broke in", but the system sounds so much better. On the Facebook Mark Levinson group, the recalled TX amps were all version 1200 or 1201, and the improved amps were all 1400 and 1401. All the posts on GX amps I have seen have part number 86280-60890 and version 1200, but looks like I have part number 86280-60891 and version 1400, so I'm wondering if I have a new amp? I have only had my GX for a few weeks. If this is correct, I thought maybe this could be good news that perhaps they are acknowledging a problem with the GX too, and perhaps they have a corrected amp that they are now installing in new builds. Seems like this could lead to a TSB being issued for GX and everyone can get the upgraded amp? Does any other GX owner have this part number and version? You can check by going to Settings>Software Update>Model Info, then scrolling down to AP SW section for Parts No. and Version.
View attachment 16268

Wait a moment, the part version No. on my GX, which built in Jan 2025 was 1300. the part No is 86280-60890. I guess 1200 was the version No. for TX?

 

[pnwgx550]

Over the last few days, not sure if my speakers "broke in", but the system sounds so much better. On the Facebook Mark Levinson group, the recalled TX amps were all version 1200 or 1201, and the improved amps were all 1400 and 1401. All the posts on GX amps I have seen have part number 86280-60890 and version 1200, but looks like I have part number 86280-60891 and version 1400, so I'm wondering if I have a new amp? I have only had my GX for a few weeks. If this is correct, I thought maybe this could be good news that perhaps they are acknowledging a problem with the GX too, and perhaps they have a corrected amp that they are now installing in new builds. Seems like this could lead to a TSB being issued for GX and everyone can get the upgraded amp? Does any other GX owner have this part number and version? You can check by going to Settings>Software Update>Model Info, then scrolling down to AP SW section for Parts No. and Version.
View attachment 16268

I have the same part number and version as you do and I’m not experiencing any audio difficulties or performance issues. My vehicle was built in July 2025 and delivered in late August 2025 .

 

[pnwgx550]

Over the last few days, not sure if my speakers "broke in", but the system sounds so much better. On the Facebook Mark Levinson group, the recalled TX amps were all version 1200 or 1201, and the improved amps were all 1400 and 1401. All the posts on GX amps I have seen have part number 86280-60890 and version 1200, but looks like I have part number 86280-60891 and version 1400, so I'm wondering if I have a new amp? I have only had my GX for a few weeks. If this is correct, I thought maybe this could be good news that perhaps they are acknowledging a problem with the GX too, and perhaps they have a corrected amp that they are now installing in new builds. Seems like this could lead to a TSB being issued for GX and everyone can get the upgraded amp? Does any other GX owner have this part number and version? You can check by going to Settings>Software Update>Model Info, then scrolling down to AP SW section for Parts No. and Version.
View attachment 16268

A few weeks ago, I was using ChatGPT to aggregate some data related to this issue as well as the TSB that fixed the issue in the Lexus TX. The following is the final output that resulted from a series of prompts asking if the Mark Levinson issue had been addressed in my specific 2025 GX550 Overtrail+:

On your AP SW screen you now have:

• Parts no.: 86280-60891
• Version: 1400

Here’s how that lines up:

Known TX “fix” reference

• The TX TSB (L-SB-0029-25) ties the correction to amplifiers in the 86280-0E3xx family, with software versions in the 13xx–14xx range after replacement. Owners report the fixed units show “Version 1400” (or higher) on their AP SW screen.

GX situation

• The GX550’s amplifier family is different: 86280-6089x, not 0E3xx. Catalogs list 86280-60890 as the “base” ML amp. Yours (…60891) is a later revision not yet tied to a public bulletin.
• The fact your software version is 1400 suggests you’re running the same generation of firmware that TX owners describe as the “fixed” set. That’s a positive indicator that your amp revision incorporates similar updates.
• But: Lexus hasn’t published a GX bulletin or campaign, so there’s no official confirmation that 60891/1400 is the GX equivalent of the TX fix. It looks promising, but not “documented.”

Bottom line

Your GX’s 86280-60891, Version 1400 strongly suggests you have a newer Mark Levinson amplifier revision with updated firmware, analogous to the TX’s fixed amps.

However, since the TSB is TX-only, Lexus hasn’t formally declared this a GX “fix.” So functionally you likely benefit from the update, but it isn’t recognized as a campaign item for your VIN.


I hope that this is useful to some of the members of the forum following this thread!

 

[Tin Ear]

Thanks Remmy for the detailed plan.

The Kicker Key amp sounds impressive with its built-in correction features.
I think where the confusion lies for some of us (and why I brought up the closed-loop system in my earlier post)
is that even with that clever tech, the solution primarily addresses the sub-bass (the rumble) and only for that new sub. It doesn't solve the other problems, like the very weak rear channels, muddy mid-bass from the door woofers, and the phasing issues across the 21 speakers in the cabin.
Using a signal that has already been high-pass filtered and EQ'd by the factory DSP is always a compromise. While your amp can work around it, it can't put back the audio information that the factory system has already removed or rolled off.
For audiophiles looking for a full, balanced, and perfectly tuned soundstage throughout the entire cabin, an aftermarket sub is a great addition, but the only real fix for the entire system's tuning flaws is a software update from Lexus.
I'll be following your install with interest, as it's a solid approach for those who just want more overall thump!

 

[cmfhsu]

My July 2025 production Luxury+ also has the 86280-60891 amp, version 1400.

The bass does not appear to fade in and out, but the default frequency and fader tuning is still pretty garbage, IMO. The 120-200hz-ish region of male voices is super over emphasized and "woof-y", like a poorly integrated, overpowered sub. I still get very little volume when fading the audio to the rear speakers.

My "okay enough, but not in love" tuning is to fade the audio to the rear two clicks, and turn down the treble by one click. I keep speed-sensitive volume and surround sound both on, because the speed sensitive volume seems to be very specifically tuned to the surround sound frequency response; bass and treble seem to get really oddly emphasized if I disable surround sound. It's a bummer, because I think surround sound worsens & disperses the pinpoint spatial imaging of vocalists.