Device Behaviour

Device Behaviour

How the speakers behave in operation, as far as it is known. Tested hardware: KH 120 II (firmware 1_7_3) and KH 750 DSP (firmware 2_1_2; it reports its product as KH 750). KH 80 DSP and KH 150 are not tested on hardware (see Limits-and-Untested).

Source marks [measured], [khtool], [manual]: see the legend on Home.

Overview

Topic	Behaviour	Source
Standby	The speaker does not answer SSC at all (no TCP connection). It looks exactly like a powered-off speaker. Seen on KH 120 II and KH 750.	[measured]
Standby	Standby switches off the network interface, signal processing and amplifiers (KH 120 II/KH 150 and KH 750 DSP manuals).	[manual]
Wake-up	Standby ends when a strong enough input signal arrives; return to playback takes about 5 s.	[manual]
Settings persistence	KH 120 II and KH 750 keep their last settings through power-off and network disconnect.	[manual]
Explicit save	device/save_settings answers 404 on KH 120 II and KH 750.	[measured]
Explicit save (KH 80)	KH 80 needs {"device":{"save_settings":true}} for changes to survive a power cycle. Not tested on hardware.	[khtool] (issue tracker: maintainer statement, khtool issue 5)
Several connections	Simultaneous TCP connections to one speaker are served; probably 4 per speaker, the next one times out at connect (see SSC-Protocol).	[measured]
Answer time	One leaf query: 1–47 ms (mean 19 ms), always exactly one line.	[measured]
Push updates	The speakers support subscriptions (osc/state/subscribe, see SSC-Protocol).	[measured]

Standby and wake-up

Aspect	Detail	Source
SSC in standby	No answer, no connection - not merely rejected requests. Both tested models.	[measured]
Wake trigger	Sufficient input signal; about 5 s until playback resumes.	[manual]
Auto standby (KH 750)	Switched on and off only with the AUTO STANDBY switch on the back [manual]; device/standby/enabled and ui/auto_standby (ON/OFF) both follow the switch: with the switch on OFF they read false / OFF; back on ON, ui/auto_standby read ON at once, while device/standby/enabled still read false and read true about 5 s later; an untouched second KH 750 stayed true / ON [measured]. This explains why both refuse writes; writing the current value of ui/auto_standby answered 405 [measured]. With the switch on ON, the subwoofer goes to standby after 90 min without input signal; the delay and the standby signal level can be changed over the network [manual]: device/standby/auto_standby_time (1–240 min) and device/standby/level (threshold, −80 to −55 dBu), both write-tested [measured]. On firmware 2_1_2, LOCAL mode (CONTROL MODE switch) reports 19 min [measured]; the manual's 90 min (edition 02/21) may describe older firmware.	[manual], [measured]
Auto standby (KH 120 II)	Analog input: standby when the reproduced level stays below a threshold; digital inputs: without digital clock or with a muted digital signal; wakes when a digital signal is present [manual]. With CONTROL on Local the delay is fixed at 90 min and the threshold is internal [manual]. With CONTROL on Network both are set over the network: device/standby/auto_standby_time (1–240 min) and device/standby/level (threshold, −80 to −55 dBu) [measured], [manual].	[manual], [measured]

Standby paths

Path	Meaning	KH 120 II	KH 750	Source
device/standby/enabled	Auto standby on/off	read and write	read, follows the AUTO STANDBY switch [measured]; write refused (on/off is the switch [manual])	[measured], [manual]
device/standby/auto_standby_time	Delay, 1–240 min	read and write	read and write	[measured]
device/standby/level	Threshold, −80 to −55 dBu	read and write	read and write	[measured]

"Write" here means CONTROL / CONTROL MODE on NETWORK. With the KH 750 on LOCAL, writes are refused with 401 and auto_standby_time reads 19 instead of the network value (see Control mode) [measured].

Firmware

Aspect	Detail	Source
Version format	major_minor_patch with underscores, e.g. 1_7_3	[measured]
Firmware update duration	About 10 s per KH 120 II, about 1.5 min per KH 750 DSP (update via Neumann's own software).	[manual]
Reboot duration over SSC	Not tested on hardware.	-

Factory reset

Aspect	Detail	Source
SSC command	Write FACTORY_DEFAULTS to device/restore; the speaker's own osc/limits lists it as an option of the path (besides an empty string).	[measured]
Reading device/restore	Returns an empty string.	[measured]
Device reaction to an SSC-triggered reset	Not tested on hardware.	-
Manual reset, KH 120 II / KH 150	Power on; while booting (logo red), toggle the CONTROL switch up and down until the logo is white for a few seconds; it then flashes red quickly for a few seconds and returns to white.	[manual]
Manual reset, KH 750 DSP	Power on; while booting (power LED red), toggle the AUTO STANDBY switch until the LED is green for a few seconds; the LED then flashes red while defaults are applied and finally turns green.	[manual]
Manual reset, KH 80 DSP	While the logo is red during boot, toggle the SETTINGS switch repeatedly until shortly after the logo turns white.	[manual]

Settings persistence

Model	Behaviour	Source
KH 120 II	Keeps last saved settings when switched off, unplugged or disconnected from the network. device/save_settings is 404.	[manual], [measured]
KH 750 DSP	Keeps its settings when disconnected from network or power. device/save_settings is 404.	[manual], [measured]
KH 80 DSP	Needs an explicit device/save_settings. Not tested on hardware.	[khtool] (issue tracker)
Other models	Not measured.	-

Control mode LOCAL / NETWORK

Aspect	Detail	Source
SSC leaf	ui/control_mode, values NETWORK / LOCAL; answers a get on both models.	[measured]
Who sets it	The switch on the back (CONTROL on the KH 120 II, CONTROL MODE on the KH 750) selects Local or Network.	[manual]
Rear switch in LOCAL	The speaker ignores network commands; only the rear-panel controls work.	[manual]
LOCAL over SSC (KH 750)	ui/control_mode reads LOCAL with the switch on LOCAL and NETWORK with it on NETWORK. Reads keep working: every path read in LOCAL mode answered. Writes are refused with 401 authorisation needed, even one that sends back the current value (audio/out/mute false). Values change: the device uses its local settings instead of the network configuration: audio/out/level read 96.0 (100.0 on NETWORK) and device/standby/auto_standby_time 19 (60 on NETWORK); device/standby/countdown read 19 (audio was playing, so it was not counting down). Back on NETWORK, ui/control_mode read NETWORK, the time 60 and the level 100.0 again, and the same mute write was accepted (echo).	[measured]
LOCAL over SSC (KH 120 II)	A set (mute) was refused with 401 as well; a set of the read-only ui/control_mode still answered 405, so writability is checked before the switch. The value changes in LOCAL were not measured.	[measured]
Rear switch in NETWORK	Rear-panel controls marked with * are ignored; without an active controlling software the last network configuration is used.	[manual]
Writing over SSC	Refused: writing the current value NETWORK answered 405 "method not allowed" on both models, although osc/limits flags the field writeable. The mode follows the switch, so it cannot be set over SSC.	[measured]

Connections and timing

Aspect	Detail	Source
Parallel connections	Simultaneous connections are answered (two tested on a KH 120 II, three on a KH 750); a lingering socket blocks nothing while a slot is free. With one client connection open, a 4th extra connection timed out at connect on both models (no refusal), so probably 4 per speaker. On the KH 750, requests sent on two connections at the same time were each answered on their own connection (20 of 20 pairs, 17–80 ms).	[measured]
Leaf answer time	1–47 ms, mean 19 ms, exactly one line per answer.	[measured]
54 paths of a KH 750, one request each	1.55 s.	[measured]
Full schema walk	KH 120 II: 3.4 s for 64 schema paths; KH 750: 7.4 s for 143 (all typed leaves plus the untyped osc nodes), returning on each reply as soon as it arrived.	[measured]
Meters	m/in/level and m/out/level refresh about every 200 ms (5 Hz).	[measured]
Error replies	Arrive as one line like a value, with the error code nested in the request's address tree (see SSC-Protocol).	[measured]

See also: SSC-Protocol · SSC-Paths · EQ · Limits-and-Untested