Not getting the full 16 increments when adjusting volume on Ventura

Question

I'm not getting the full 16 increments when adjusting sound on Ventura.

Here's what happens when I increase the volume from zero, step-by-step.

Step 1: Audio output goes to 0.082 (As seen in Audio Menu in System Settings or in MIDI app)    
Step 2: Still 0.082  
Step 3: 0.184  
Step 4: 0.327  
Step 5: Still 0.327  
Step 6: Still 0.327  
Step 7: 0.51  
Step 8: Still 0.51  
Step 9: Still 0.51  
Step 10: 0.735  
Step 11: Still 0.735  
Step 12: Still 0.735  
Step 13: Still 0.735  
Step 14: 1.0  
Step 15: Still 1.0  
Step 16: Still 1.0  

So as you can see, instead of the 16 incremental volume steps I should have, I only get 7, which is not enough.

Any idea why this is happening or how I can fix it?

Here's my system:

• Mac mini 2020 (M1)
• Ventura 13.3.1
• KEF LSX II speakers (connected through USB-C).

Answer 1

It's the USB DAC that controls volume increments

instead of the 16 incremental volume steps I should have, I only get 7, which is not enough....Any idea why this is happening or how I can fix it?

This is a function of the USB device; specifically the Audio DAC chip that sets the increments of the volume control. To illustrate this, let's take a look at a common DAC - the TI PCM27xx chip (I don't know the chip in your specific application). Reviewing the datasheet, we get this nugget of critical information about volume control:

^{(Feature Unit 3 is the block diagram that looks like an audio equalizer)}

Output terminal #2 is defined as a speaker (terminal type 0x0301). Feature unit #3 supports the following sound control features:

• Volume control
• Mute control

The built-in digital volume controller can be manipulated by an audio-class-specific request from 0 dB to –64 dB in steps of 1 dB. Changes are made by incrementing or decrementing one step (1 dB) for every 1/fS time interval, until the volume level reaches the requested value.

^{Emphasis Mine}

What this is saying is that for this particular DAC Audio Chip, there are 64 increments that are possible. As macOS uses 16 increments, this means that for every increment/decrement of volume up/down the chip will increase/decrease by ±4dB. Again, this is just an example of a USB audio chip as this datasheet is easy to obtain; if they provide amplified audio like this one, it will work in the same manner.

All this said, it doesn't preclude the manufacturer from introducing volume limits and increment values through firmware that translate "Volume Up/Down" to an increment of a different amount.

For example, if the firmware manipulates by 8dB up/down by sending 8 signals to increment/decrement at a time). There will be only 8 increments available to macOS. Meaning one press will increment and the subsequent press will do nothing. The third will increment and the fourth will do nothing, etc. This is just one example case, the firmware configuration for each will differ across manufacturers and even across models.

TL;DR

If the 7 or so increments isn't enough for you, you'll need to find a different set of USB speakers with a DAC that allows for more increments as it's the device itself and has nothing to do with macOS. The OS just sends the command to increase/decrease volume; it has no control over how the hardware interprets those commands.

Answer 2

Your KEF LXII speakers seem to be fairly sophisticated units; they're rather expensive, and the User Manual for the speakers is over 100 pages. I'm sure you've been through the User Manual, but there were a few items (one in particular) that struck me as potentially relevant to your issue, so perhaps it's worth re-visiting?:

From Section 14 of the User Manual:

There are, in Sections 14.8.3 & 14.8.4, two adjustments made through the "KEF Connect App" that may get to the heart of your issue:

• Speaker Volume Sensitivity
• Maximum Volume

As I read the descriptions here, this could easily explain how volume and sensitivity are being "translated" from your Mac's volume control to the speaker's volume controls. This is where I would concentrate my efforts; you want greater sensitivity, and (I suspect) a rather large Maximum Volume setting to get the finer 16-step Mac volume resolution.

But there are other passages in the User Manual that may be important:

From Section 12:

A couple of things:

1. Connect speakers to LAN before USB:

   The speakers must always be first connected to your local network before USB connection.

   This sounds as if it means you must first connect the speakers via your LAN before using the USB connection method.

2. Under Playback Controls (12.3) we find this statement:

   All playback controls (except adjusting volume) must be done on the connected device. The volume can also be adjusted on the remote control.

   This sounds a bit ambiguous, but I assume that "connected device" is your Mac, and that there is also a remote control device that can also adjust volume. If that's the case, is the volume control for the remote control as "coarse" as the Mac's 7-level control? Please refer to Section 14.8.1 - Volume Display Setting when considering this question; the - / + format may give you a comparison.

Finally,

There's a tip (# 4, page 86) for some setup in the KEF Connect App that may be useful when controlling volume from external equipment.