I have a Roku Ultra 4800 and it is connected to a Samsung 70" TU700D 4K UHD LED TV. I previously had an older generation Roku Ultra and was experiencing some unrelated issues, so I decided to purchase a new one. I am using only the speakers in the television. The sound quality coming from the 4800 is not good at all. The volume is reduced and now the sound leveling feature does nothing when I change it from off to leveling or night. I have connected it through the ARC HDMI port as well as a standard HDMI port with no change. I really have no idea what is going on and I'd like to resolve the issue. Does anyone have any ideas of what might be my issue?
I just purchased a new Roku Ultra 4800 for the very same reason, and I'm having the very same issues. I am so frustrated. The sound leveling on the older model (4660) worked great and I was expecting the same on the new model, but nothing! And, I have absolutely no idea what the Dialog Enhancement "On for AC-4" does at all.
Not only does the volume leveling not work at all, but the general tv volume settings are no longer sufficient. I have to turn the volume up nearly all the way just to hear dialog properly and then getting blasted out of the room from background noises.
Problem with going back to the old model is that the remote to the 4660 is acting up and replacements are no longer available, but I'm on the verge of going back to the old model.
As for the "Dialog Enhancement" setting - that only applies to content/apps/services using the AC4 codec, which are practically none at this point (ATSC 3.0 uses it per spec) - it is more future proofing that anything else (akin to the AV1 codec, though there is more extant support for that). Some claim it works for them (no apps/services specified) - you'll have to experiment with different apps/services to see if it does for you.
As for volume levels, the newer models (2020+) use a new SoC series (RTD131x) that has different baseline volume levels than older ones, then on top of that the Dolby decoder included with the 4800/4802 can/does make a difference when active.
In the default (Settings/Audio/Digital output format) Auto mode, all non-DTS audio is transcoded to the highest detected Dolby level of the connected device, and the volume may be higher if your TV/AVR supports Dolby PCM MAT 2.x (since its PCM, and PCM volume levels are almost always higher in all devices). However, this is not the preferred or recommended mode, though it MAY result in higher volume in some scenarios.
In the recommended/preferred (Settings/Audio/Digital output format) Passthrough mode, all Dolby & DTS audio is passed through (with the exception of DD+ being converted to DD for legacy DD-only connected devices), and most non-Dolby/DTS audio (usually 2.0) is decoded to PCM for output. This generally results in 2.0/Stereo content being louder than multichannel, since its usually AAC 2.0 decoded to PCM. This is the preferred/recommend mode for most scenarios, as it allows the TV/AVR/SB to do the decoding.
If you are just connecting to a TV and have no need for multichannel (5.1/7.1) output via an AVR/SB etc, you might consider changing Settings/Audio/Digital output format = Stereo as that would force all output to be decoded to PCM, and thus generally have a louder volume in general than bitstreamed passthrough formats such as Dolby/DTS.
You can always use the 4800's remote with the 4660 - it'll work in IR-mode without pairing, but if you want to use the Voice/Headphones/Advanced features you'll need to pair it.
Otherwise you can get the Voice Remote Pro for $30 at Roku/Walmart/Amazon/etc - it'll work with your 4660 without issue, just remember to pair it if you want to use Voice/Headphones etc.