This topic applies to all audio applications. But I think it most likely to be of used with subwoofers.
The best theoretical loudspeaker book I've ever found:
High performance loudspeakers / Martin Colloms , 1991, is where I first learned of this idea. Colloms is convinced it will make for better sound.
Any thoughts, opinions, experience? Anyone built such? Anyone have a schematic? Any commerical products on the market?
A standard amp is a voltage source, and approximates zero ohms output impedance. A current source approximates infinite impedance.
The best theoretical loudspeaker book I've ever found:
High performance loudspeakers / Martin Colloms , 1991, is where I first learned of this idea. Colloms is convinced it will make for better sound.
Any thoughts, opinions, experience? Anyone built such? Anyone have a schematic? Any commerical products on the market?
A standard amp is a voltage source, and approximates zero ohms output impedance. A current source approximates infinite impedance.
With a high impedance source, the Qe of the driver disappears and the unit resonance is only damped by its Qm which Qt equals now.
High impedance idea may be a valid idea far above the main resonance. Its advantages as well as the restoration of the damping of the main resonance by motion feedback has been dealt by Hawksford :
http://www.essex.ac.uk/ese/research/audio_lab/malcolmspubdocs/C17 Current drive patent.pdf
and Greiner-Travis :
http://www.aes.org/e-lib/browse.cfm?elib=11756
High impedance idea may be a valid idea far above the main resonance. Its advantages as well as the restoration of the damping of the main resonance by motion feedback has been dealt by Hawksford :
http://www.essex.ac.uk/ese/research/audio_lab/malcolmspubdocs/C17 Current drive patent.pdf
and Greiner-Travis :
http://www.aes.org/e-lib/browse.cfm?elib=11756
Hi zenmasterbrian,
I have Colloms's book. He refers to Hawksford who says that current driven speakers exhibit lower distorsion. He shows some examples just as Greiner-Travis.
---It came up in another thread as a way to run a subwoofer below fs.---
Have you the reference ? I think of a misconception here.
I have Colloms's book. He refers to Hawksford who says that current driven speakers exhibit lower distorsion. He shows some examples just as Greiner-Travis.
---It came up in another thread as a way to run a subwoofer below fs.---
Have you the reference ? I think of a misconception here.
I may know the whole story about Colloms' idea about being convinced that current amplifier is the way to go, however I am confident that with his networking ability he knows many competent amplifier designers, I am confident that he could convince one of them to design one unit for him to test out.
Did this happen? I don't know. If it did what is the outcome.
Did this happen? I don't know. If it did what is the outcome.
If anything they would be more amenable to current drive since the headphone socket on 99% of amps is simply taken from the normal power output stage via a resistor of some 'significant' ohmage.
Nice module appearing on my website soon that can be used for current or voltage drive of headphones or line inputs
Nice module appearing on my website soon that can be used for current or voltage drive of headphones or line inputs
http://www.diyaudio.com/forums/showthread.php?threadid=3889&highlight=
http://www.firstwatt.com/articles.htm
http://sound.westhost.com/project56.htm
http://www.enjoythemusic.com/magazine/equipment/1204/firstwattf1.htm
http://www.enjoythemusic.com/magazine/equipment/0606/visation_nobox_bb_loudspeaker.htm
http://www.6moons.com/audioreviews/firstwatt/firstwatt3.html
http://www.6moons.com/audioreviews/firstwatt2/f2.html
possibly (don't speak/read german):
http://www.silbersand.com/
BM Universal Subwoofer (under the sitemap link)
http://www.firstwatt.com/articles.htm
http://sound.westhost.com/project56.htm
http://www.enjoythemusic.com/magazine/equipment/1204/firstwattf1.htm
http://www.enjoythemusic.com/magazine/equipment/0606/visation_nobox_bb_loudspeaker.htm
http://www.6moons.com/audioreviews/firstwatt/firstwatt3.html
http://www.6moons.com/audioreviews/firstwatt2/f2.html
possibly (don't speak/read german):
http://www.silbersand.com/
BM Universal Subwoofer (under the sitemap link)
zenmasterbrian said:
You are welcome -
That first DIY thread is probably the best source of information on the interaction between amp and driver you will find anywhere. (..and largely due to the contribution of Thorsten.)
Mr. Pass fills in the information on crossovers nicely.
Rod Elliot shows important (but marginally usefull) information on op-amp methodes to obtain impeadance that you won't find elsewhere. Mr. Pass's F1 manual has a schematic which also aids a builder of these amps (though with discreet transistors instead).
The other articles are just to show subjective impressions and in particular the graphs DO has done to show the alteration in bass extension.
Combined - its a start.
rinox, see that is what I'm wondering here. Tell me more about magneplanar.
See, maybe current source is or is not better. What made me bring it up here was discussions about running a driver below fs. So, its being run on both sides, and you want flat response.
Then, there is the damping issue. Maybe damping can be addressed with the enclosure?
I guess I'm saying, maybe current source has benefits, if its been worked into the whole design with the drivers and enclosures. Then there are also circuit issues of how to get the best current source.
See, maybe current source is or is not better. What made me bring it up here was discussions about running a driver below fs. So, its being run on both sides, and you want flat response.
Then, there is the damping issue. Maybe damping can be addressed with the enclosure?
I guess I'm saying, maybe current source has benefits, if its been worked into the whole design with the drivers and enclosures. Then there are also circuit issues of how to get the best current source.
I suspect damping ratio is defined differently in different situations. Probably if you drive current source, it is defined some how so that high Z works better.
If you drove matched, or mid level impedance, then you probably do have poor damping, but you could try to get it via the enclosure.
I'm not looking at matched, just current source. Likewise, crossovers have to be totally different for high Z.
But I'm only interested in multi-amping with active crossovers, so it is a non-issue.
If driver is connected to current source amp, such amp will give a correcting current for any induced by driver motion. So it is providing damping. Voltage source and current source are extreme cases. I think either provides high damping.
But there are other issues here. I'm looking at this for possibly going way below fs. That was how this came up. Can it be better there? That Elliot Sound might deal with this.
If you drove matched, or mid level impedance, then you probably do have poor damping, but you could try to get it via the enclosure.
I'm not looking at matched, just current source. Likewise, crossovers have to be totally different for high Z.
But I'm only interested in multi-amping with active crossovers, so it is a non-issue.
If driver is connected to current source amp, such amp will give a correcting current for any induced by driver motion. So it is providing damping. Voltage source and current source are extreme cases. I think either provides high damping.
But there are other issues here. I'm looking at this for possibly going way below fs. That was how this came up. Can it be better there? That Elliot Sound might deal with this.
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