31-01-2019, 06:57 PM
Mike, what you are proposing is not what I would call an 'active' speaker - just a passive speaker driven by an amplifier with a wide range tone control.
The problem with audio, given decent quality speakers is the compromise between size and bas response and an active speaker can help here.
In the 70s, Philips introduced an active speaker which had a piezo accelerometer incorporated in the cone of the woofer to provide feedback proportional to movement of the cone which could be used to correct the drive power with frequency to obtain an extended level bass response.
The second UK issue of Elektor included a design to replicate this function in a way that didn't require the special Philips woofer but instead used a carefully controlled level of positive (yes!) feedback to achieve the same result.
Elektor demonstrated the prototype on their stand at an exhibition in either Earls Court or Olympia that I went to and the results were amazing! I can let you have a pdf copy of that issue if you are interested. You can still use your Sinclair amps if they do, on fact, work - the article describe the additional electronics that precede the amplifier inputs.
I know some Elektor designs can be found on the internet but I think they are rather fussy about copyright, so I'll put a copy of the file (37MB!) in my Dropbox and send you the link if you want it.
The problem with audio, given decent quality speakers is the compromise between size and bas response and an active speaker can help here.
In the 70s, Philips introduced an active speaker which had a piezo accelerometer incorporated in the cone of the woofer to provide feedback proportional to movement of the cone which could be used to correct the drive power with frequency to obtain an extended level bass response.
The second UK issue of Elektor included a design to replicate this function in a way that didn't require the special Philips woofer but instead used a carefully controlled level of positive (yes!) feedback to achieve the same result.
Elektor demonstrated the prototype on their stand at an exhibition in either Earls Court or Olympia that I went to and the results were amazing! I can let you have a pdf copy of that issue if you are interested. You can still use your Sinclair amps if they do, on fact, work - the article describe the additional electronics that precede the amplifier inputs.
I know some Elektor designs can be found on the internet but I think they are rather fussy about copyright, so I'll put a copy of the file (37MB!) in my Dropbox and send you the link if you want it.
