No doubt, YOU are an objectivist... witch refuse evidence.
Yes, that must be it.
So, who ever said "all the amps sound the same"? Or did you just make that up?
I got and read Merilainen's book on current drive too, and despite his clearly being a man obsessed, realized quickly that he wasn't a crank at least. Just very frustrated! He mentions that the AES Journal refused to run an ad for the book! I gave it a cautiously positive review on Amazon, while I think mentioning that if one saw the author coming towards one, you might remember a suddenly-pressing engagement, like that long-overdue rearrangement of the sock drawer.
What makes it so difficult to evaluate current drive, which he claims is sonically superior over and above the elimination of voice coil heating effects, is that there are no loudspeakers available to use for a comparison. He is not saying drive any old speaker with a current source, but drive a purposely-designed one with a current source amp suitably equalized if need be, and compare it to a comparable one with voltage drive. But how in the wide wide world of sports do you do that---and in particular avoid frequency response variations that we know are among the easiest things to hear? I think it is barely possible, and that does not mean I disparage current drive as an approach.
But Steve, you are in the minority from my experience. Most of the transducer and system designers I know would like to keep their domain circumscribed. I got a lot of pushback when I proposed a displacement transduction technique to one such transducer guy, who quickly stated that he could accomplish the linearization scheme I suggested by tuning the motor, spider, surround... to which I said So why aren't you doing that? I think the subject was changed at that point.
Brad
Thanks Brad.
As a former employer said to me when I was very young, I wasn't one of the sheep, I didn't follow the leader so to say. You seem to also be in that camp, you can use your own knowledge and imagination to come up with new solutions and approaches to an engineering problem. With or without current drive it does seem to me that including the speaker in the feedback look makes a lot of sense. And I know that most speaker designers I have met and guys who work on the electrical side of things seem to compartmentalize this whole approach to design. I think we have gotten to the point where it is the only thing left to do that will make a dramatic difference.
As a former employer said to me when I was very young, I wasn't one of the sheep, I didn't follow the leader so to say. You seem to also be in that camp, you can use your own knowledge and imagination to come up with new solutions and approaches to an engineering problem. With or without current drive it does seem to me that including the speaker in the feedback look makes a lot of sense. And I know that most speaker designers I have met and guys who work on the electrical side of things seem to compartmentalize this whole approach to design. I think we have gotten to the point where it is the only thing left to do that will make a dramatic difference.
Geddes opinion seems to be that integrating speaker and amp, applying feedback or DSP won't fix anything he considers important
the simplified version of his claim after developing his metric is that small smooth nonlinear distortions are unimportant in listening tests - at least at those levels that can be achieved today with pro drivers ran at consumer levels
directivity control and some time response issues seem to be his concerns
the time response really is limited by the driver construction - we just don't have stiff enough well behaved cheap material to make rigid piston drivers over extended frequency range. large enough for any sound radiation efficiency at all
you need sensors and actuators for each mode if you want activel control to address such problems with current materials
the simplified version of his claim after developing his metric is that small smooth nonlinear distortions are unimportant in listening tests - at least at those levels that can be achieved today with pro drivers ran at consumer levels
directivity control and some time response issues seem to be his concerns
the time response really is limited by the driver construction - we just don't have stiff enough well behaved cheap material to make rigid piston drivers over extended frequency range. large enough for any sound radiation efficiency at all
you need sensors and actuators for each mode if you want activel control to address such problems with current materials
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I'd agree with Earl that smooth nonlinear distortions are usually of secondary concern. However for transducers with a large amount of excursion relative to the piston area, such as ones that prompted an idea about displacement transduction, the IM distortion gets severe if the device is reproducing a significant range of frequencies. This proved to be very deleterious for some desktop speakers I worked on---pitched transients like piano or vibraphone were just mutilated.
And directivity is indeed a problem, which some misguidedly attempt to correct with EQ, which efforts are mostly pointless or counterproductive.
I believe in the mid 80's Dick Marsh published in Audio Amateur a circuit for distortion reduction of a JBL 15 inch driver through current drive or feedback - have we come so far in the 30 years since ........
DSP speaker/room correction with sufficient bits and sampling frequency and well designed software may well be be the next step forward. Can I get beer while the bun fight over the number of bits and software starts?
DSP speaker/room correction with sufficient bits and sampling frequency and well designed software may well be be the next step forward. Can I get beer while the bun fight over the number of bits and software starts?
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While I agree with E Geddes on many things I also disagree on some of his generalizations about distortion and phase response. He and I have done much parallel development over the years and I'll leave it at that.
If anyone wants to look at the very old patent I once held and all the following devices that reference that patent here is a link. The most important parts of that patent were the first mathematical description of a sound chamber and a cone driver and the use of rigid polyurethane foam material to produce a horn. If you look you will find that all of Earl's development has also been with urethane materials.
Patent US4369857 - Loudspeaker and horn combination - Google Patents
The patent drawing were done by me, except for the numbering system for patent claims. The direction I was taking at the time was leading to cone drivers used with phase plugs to create a large scale cone driven compression horn.
Brad,
We do live very close together and one of these days I would love to meet you and discuss some of what I am doing.
If anyone wants to look at the very old patent I once held and all the following devices that reference that patent here is a link. The most important parts of that patent were the first mathematical description of a sound chamber and a cone driver and the use of rigid polyurethane foam material to produce a horn. If you look you will find that all of Earl's development has also been with urethane materials.
Patent US4369857 - Loudspeaker and horn combination - Google Patents
The patent drawing were done by me, except for the numbering system for patent claims. The direction I was taking at the time was leading to cone drivers used with phase plugs to create a large scale cone driven compression horn.
Brad,
We do live very close together and one of these days I would love to meet you and discuss some of what I am doing.
Modern J-Hang line arrays can be flown up in 20 minutes per array, usually four arrays plus floor subs.
The adjustable hanging point hardwares are NC manufactured works of art.
That 'Wall of Sound' pic makes me shudder at the labour for the load in, set up and sound check....no way it could be done nowadays for OH&S reasons if nothing else.
Still, I wish I was around at the time to hear it....kudos to you and road crew/production for getting it to work
.How good did it sound ?.
Dan.
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You got 2 and 1/4 hours to kick up your heels? ... https://www.youtube.com/watch?v=69ljEiTMmjo ...
Kindhorman, Brad, are you guys aware (probably yes but I will still mention it ;-) of what Klippel is doing with his pre-correction of drivers? As an example, current versus excursion transfer function for most drivers is different when moving forwards or moving backwards, and is quite consistent from driver to driver. So he does characterize that and 'pre-corrects' the drive signal through DSP. Avoiding the obvious issues with trying to put a mech system within a feedback loop.
Jan
Different half cycle excursion in free air or when fitted to a sealed enclosure ?.
Dan.
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