Wednesday, 7 May 2014

Current drive??

So we were on holiday.

Gave me time to rethink my last struggles with passive filters.
For years now we are aware of audible effects of components which do not directly relate to the electrical parameters of that component.
Sonic differences between the blue and the green cap..(green is always better :)
Also a conversation with a real horn loving tekno-head (those guys terrorizing former eastern europe countries with big piles of often home brew PA systems) and his love for Labgruppen PLM20000 amps made me rethink the whole concept of 'damping factor' in power amps.
I also recalled a remarkable experiment with (big) series capacitors on a (to us) well known and often used 10" speaker with my audio companion Sebastiaan.
And last but certainly not least all my experiments over the years with tube amps..

Serendipity made me stumble across:


A very well written book about the fact that the concept of a loudspeaker as a voltage to SPL converter is in fact totally wrong.
The principal of a electro-dynamic loudspeaker is based on:

F=B*i*L
Remember from high school? (and the grins: bil means buttock in dutch).
No V for voltage in this equation!

So today I did this experiment:

Two small hifi -isj cabinets (only the low speaker) one connected directly to the poweramp, the other one with a series resistor of 50 ohms to simulate (a partly) current source. To compensate for the obvious volume difference I made a quick Soundweb file, this gave me also the possibility (try) to equalize the magnitude difference caused by the impedance curve of the speaker in series with that 50 ohm.

Acoustic recording from a Argentinian choir craftly made by our Sebastian, and:

WOW!!
This is something!
Wierd things happening..
More to follow..