On Fri, 9 Nov 2018 08:01:05 +0100 (GMT+01:00), Libor Striz wrote:

I have not noticed a phone with a dedicated ringtone speaker.
I have noted only phones with an earphone speaker and a
loudspeaker, with the latter used for music, aloud calls,
singing and notification.

Thank you Libor Striz for being purposefully helpful by clarifying, where
it helps to pool our knowledge, since none of us are smartphone engineers.
http://www.bild.me/bild.php?file=3265064audio01.jpg

It would be nice to get a definitive answer, where what you're saying is:
o There is a really tiny earphone speaker, and,
o There is the larger "loudspeaker"
o But there is no specific "ringtone speaker".

But, there are independent HW audio channels like
Alarm
Multimedia
Voice call
System/Notification*
Ringer'

Usenet is a way for us to pool our knowledge interactively, where, in
another thread, it has also been intimated that the "circuitry" is
different for those tasks (e.g., perhaps a different pre-amp for example),
where you seem to concur.

Since an "alarm" and a "ringtone" seem similar, but certainly "voice calls"
are quite different as are "multimedia", I wonder if we can come up with
the minimum number of "speaker circuits" that phones use to direct their
circuitry?

See also the application A-Volume
https://a-volume-widget.en.uptodown.com/android
* The application has 4 or 6 volume sliders, but these 2 seem
interconnected , partially also with the ringer.

This is a great suggestion to look at what sound apps control!

Here's a quick survey that I found just now by searching...

o Quick Settings, by F-Droid
https://f-droid.org/en/packages/com.bwx.bequick/

o Volume Control, by Netroken
https://play.google.com/store/apps/details?id=netroken.android.persistfree

o Slider Widget, by hinterhofapps
https://play.google.com/store/apps/details?id=de.hinterhofapps.sliderwidget

o Volume Control Widget, by Adam Wolfe Gordon
https://play.google.com/store/apps/details?id=ca.xvx.volume

o Precise Volume (+ EQ/Booster), by Phascinate
https://play.google.com/store/apps/details?id=com.phascinate.precisevolume

o Volume Lock & Mute, by Dieter Thiess
https://play.google.com/store/apps/details?id=de.dieterthiess.stfu

o Volume + (Easy Control) Free, by yapps
https://play.google.com/store/apps/details?id=il.yavji.volumecontrolads

o App Volume Control, by SpyCorp
https://play.google.com/store/apps/details?id=com.spycorp.appvolumecontrol

o volume control widget for android, by Apps Prime
https://play.google.com/store/apps/details?id=net.appsprime.controller.fx

o Volume App Widget, jmjurado23
https://play.google.com/store/apps/details?id=com.application.volumewidget

o Volume Controller, by Gujarati Infoware
https://play.google.com/store/apps/details?id=com.bhbharesh.VolumeControler

o Volume Widget, by WTW Electronics
https://play.google.com/store/apps/details?id=com.william.soundwidget

Running some of those in quick tests, I see these audio sliders exist:
1. Ringer volume
2. Notification volume
3. Media volume
4. Alarm volume
5. Voicecall volume
6. System volume
http://www.bild.me/bild.php?file=3265064audio01.jpg