Renoise is the only sequencer (that I’ve seen) to have both speed and bpm side by side, what is the relationship between the two?
All I know is that if you reduce the speed count the general tempo gets faster.
the time unit for all trackers (not only ReNoise, then) is the tick.
A tick represents the amount of time which passes from an audio processing to another.
The speed parameter represents the number of ticks which form a row.
So, if you set the speed to 2, each row will be formed by 2 ticks, while setting it to 6 (default) the row will be formed by 6 ticks, meaning that Renoise will process the audio 6 times during a single row.
In every tracker, BPM basically represents at which rate 24 ticks will be played.
Why 24? Because, being 6 the default speed, each beat related to BPM will be 4 rows long, which can be considered default in music (4/4 tempo).
All transforming effects (volume ramp, glide to note, and so on) have different weight on the sound, according to the speed parameter: the higher the speed (e.g.: speed 06 is higher than 03), the more a single command will have effect on the audio, because it will processed more time (e.g: processed 6 times rather than 3).
Maybe such answer should be added to Renoise manualReNoise manual; if you developers need a longer explanation for the newbies section, feel free to ask me.
… don’t think all trackers is correct though.
And anyway, this (a little bit confusing) speed parameter will
be replaced with something else in a later version.
See one of the pinned threads in “ideas and suggestions”
for a discussion about that.
The resulting effect is that the BPM setting only represents the correct value when speed is set to 6. Is that correct?
Cause i believe when i set speed to 2 (what i do mostly, in order to have a higher pattern resolution) renoise won’t be in sync with external devices (synth or fx-unit) that are set to the same BPM. Please correct me if am wrong 
Loolarge
when you set speed to 02, referring to a 4/4 tempo, each beat will last for 12 rows instead of 4.
If you interpret a beat as four lines, yes. If you interpret it as a number of ticks (24 to be accurate), then read It-Aliens post.
Sorry, i did not read It-Aliens first statement entirely. It allready does answer my question. When i set speed to 2, each beat will be 12 rows. So i’ll rather set it to 3, that way a beat is 8 rows. This way the BPM should be in sync with my other devices, right? (always using 4/4 tempo)
Thanks,
Loolarge