Hello,

Thank you for the answers, I was feeling a little bit alone !

Well, Chris, Let me try to answer, It is a kind of a challenge to work with
a 2" speaker and try to get bass, that is why I tried it.

May be you are right I will never succeed. But Bose SoundLink mini is not so
bad at this game.
It is one of the only Bose mass market product that is musical.
My challenge is to have a better system, I don't think I have succeeded yet,
although I don't have a Bose Soundlink mini to compare with.

Ok, that said, after a little time spent with the settings, I'm just able to
have more Boom Boom like a bad sono from the 80's. I could decrease the
settings though. 

I recognised that I hoped for something else...
By the way according to the box my 2" speaker is in, without any settings, I
can go down to less than 60 Hz ! But then, the size of the box is too big,
around 5L and I want 0.5L !

Now,there is something I didn't understand in your point:
/you are trying to give the impression of more bass by adding 
distortion? / YES 

/I think that trick works best when the speaker system can get down to 
within one octave of full bass response, so down to below 80Hz for sure, /
It is the case with the 5L box, I can even listen to 30 Hz although
attenuated !

/and you have to be careful to not apply enough distortion that everything 
sounds worse./ Right, just boom boom like a sono

/You may also need something like a speaker crossover, where 
only frequencies below the bass cutoff of the speaker system are sent to 
the distortion circuit,/
This is what I'm doing, a low pass that cuts everything above 200 Hz first.

/then the output of that goes through a high pass to get rid of the low
frequencies which cannot be reproduced by the speaker, / Why ? To lower
distortion ? What cut-off Frequency ? It will be very limited if I use the
0.5L box, the natural cutoff frequency of the box is around 150 Hz. 

/and the harmonics added back in to the original source to create the
illusion.  /
This is what I'm doing.

Fons, 
/It's not clear what the OP wants to do: /

/1. Create the impression of more bass by generating harmonics of the 
   bass signals that the speaker can't reproduce, or 
/ YES
/2. Create a new bass signal one octave below the original one. 
NO, that is not what I'm trying to achieve.
The latter would be pointless when using a 2" speaker./ 

/The first can be done in a limited frequency range. If your speaker 
goes down to 120 Hz or so you can get the impression of lower bass 
*by generating enough harmonics (both even and odd) of the 50..120Hz 
range. *If the speaker cuts of at 250 Hz or so then just forget it, 
it won't work. Some of the people I work with have tried to do this 
for the tiny speakers used in smartphones, all they got was distortion 
without more bass. Even in the frequency range where it works it's not 
an easy effect to get right. 
/
This is the problem, I was searching for  aplugin that generate all the
harmonics, and I could only generate second harmonic which translate in
shifting the signal one octave up, I could not succeed adding second, third,
forth, ... harmonics and I have no idea how to do it.

My speaker, in the 5L box (the one I'm playing with for this experience
before to apply it to the 0.5L box) can reproduce sine wave down to around
60 Hz with some volume (dB). So, I guess, it could be done according to your
saying. 
A little Hope here 

Thank you for thinking and for your answers/advices.

Best regards,
Jean

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