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| Current source speaker amps |
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| spec:
Hi fonograph Kleinstein has the answer. Thought you may like to know that, with similar thoughts to you, I once made a current audio power amplifier to see what it would sound like driving a speaker. With small LowFi speakers it made little difference: they sounded as bad as ever. But on decent speakers the sound seemed to vary according to the type of enclosure. With an infinite baffle the sound was bass heavy but not unpleasant and the top seemed to be unchanged. Transmission line cabinets were more base heavy and base reflex speakers were even more base heavy. The general sound, apart from the base enhancement, was a clean effortless sound that was somehow unnatural. Hope that makes a bit of sense. :) At one time I think Phillips produced some speakers that had built-in current amps, but they were part of a servo loop that used a feedback transducer attached to the speaker cone. The servo speakers didn't catch on though. |
| Audioguru:
The resonance of an undamped speaker does not simply increase low frequencies, instead it increases ONE frequency (or only a few) like a bongo drum. I think a planar magnetic driver is normally coupled to a large panel that also has a bad resonance. The very low output impedance of a voltage amplifier cannot properly damp the panel resonance. |
| boB:
Mackie HR-824 powered monitors work this way for the woofer rather than using a feedback coil. It works very well, too. boB |
| bson:
--- Quote from: fonograph on November 25, 2018, 08:56:42 am ---Why dont we use current source speaker amplifiers? --- End quote --- Some do. Current-feedback amplifiers are becoming more common; I have a Marantz MM7025 in my lab (https://www.us.marantz.com/us/products/pages/ProductDetails.aspx?CatId=avseparates&ProductId=MM7025). There's a book, Current-Driving of Loudspeakers by E. Meriläinen which covers it in detail, although IMO with some serious misunderstandings (especially regarding the presence of back-EMF), but the basic concept makes perfect sense. I looked around a bit and can't recall where I bought my copy, but it's an interesting read (maybe not so exciting nowadays since CFB topologies are more commonplace). Edit: oh never mind, Amazon has it. Not sure how I failed to find it. https://www.current-drive.info/ |
| SiliconWizard:
Audio current amplifiers do exist. As I recall, they are more often used to drive electrostatic loudspeakers. I remember the "The current amp" project in the Elektor magazine in the 90's, it was designed to drive "ribbon speakers". |
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