In clock work, the "organic"oils of the past gum up (attributed to oxidation and entrapment of other chemicals), typical run time is 3 to 5 years. Now, lots of synthetics are being used, and the belief is that there is no oxidation issue as with the non synthetics. Are FFluids using synthetic? My D205TI's have been ok so far, but they've only been in service for 15 years.
I used 16 ohm horn loaded mids back in '76.
So, the scale of a "system" means that doubling the number of turns doubles the efficiency, as in, physics no longer applies? Golly, I thought that the efficiency of a horn loaded driver would explain it...sheesh, what was I thinkin?
Ask me about "scale" someday. You seem to live under the misconception that what you do is "large"...
Once you've gone over unity, efficiency is not an issue. There, you need to worry about where to put the extra energy. That's why I asked Ed what impedance goes over unity.
John
vacuphile,
I wasn't looking at using the FF in a tweeter but perhaps in a bass/mid. It is a nice insurance policy for a long excursion voicecoil as far as rubbing and power handling but otherwise I would think to avoid the extra hassles of the fluid. The design takes into consideration the venting needed to keep the fluid in the gap but the gap is so long the amount of fluid was rather expensive, not a small volume like a tweeter would use. All the materials are compatible, like Kapton but not sure it is really a great solution for really high resolution audio.
I wasn't looking at using the FF in a tweeter but perhaps in a bass/mid. It is a nice insurance policy for a long excursion voicecoil as far as rubbing and power handling but otherwise I would think to avoid the extra hassles of the fluid. The design takes into consideration the venting needed to keep the fluid in the gap but the gap is so long the amount of fluid was rather expensive, not a small volume like a tweeter would use. All the materials are compatible, like Kapton but not sure it is really a great solution for really high resolution audio.
I think the inductance would be a problem.
See https://www.jblpro.com/pub/components/2451.pdf
Note that they use single numbers for either impedance driver.
N x I=2N x 1/2I
I used to get custom 32 ohm loudspeakers for distributed use, as did a few others.
JN,
I've had this discussion of the fluids base oils before and I do believe that Sy took a look at that and wasn't impressed with the stability of the type of chemistry they were using to hold the colloidal particles. There was a data sheet note about the viscosity rise over time of the base oil, something that just made me stay away from that solution.
I've had this discussion of the fluids base oils before and I do believe that Sy took a look at that and wasn't impressed with the stability of the type of chemistry they were using to hold the colloidal particles. There was a data sheet note about the viscosity rise over time of the base oil, something that just made me stay away from that solution.
ES,
Can we assume you used those 32 ohm speakers either in parallel or that you were using output transformers for a distributed system?
Can we assume you used those 32 ohm speakers either in parallel or that you were using output transformers for a distributed system?
I bought one like that, also expensive in the US. They are not that easy to use in terms of positioning the part and closing the gate. Better than nothing. Someone should make one where the SOT-23-3 just drops into an appropriate slot. Perhaps a job for a 3D printer expert.
Oddly enough, in the antique clock world, they use the term "synthetic", and "organic" to distinguish between oil types. Apparently, they really are trying to indicate the source of the oil, be it whales, dino's, or some vessel in some chemist's lab.
But yah, the general belief in the clock world is that synthetics do not oxidize and gum up like the "organics".
Take the quotes with a grain of salt. I'm a doctor jim, not a chemist.
John
Yes my method of avoiding distribution transformers in small higher fidelity ceiling systems.
Where on that data sheet is your equation?
On the data sheet (which certainly does not mention doubling turns, in fact...read below)
Note that the BL product of the 8 ohm is 12.7 Tesla-meters, and the 16 ohm unit is 18 Tesla-meters. Not double as you imply. Lets see, multiply 12.7 times 1.414, that is 17.957. So they increased number of turns by 41.4%, so double inductance.
Gap field is specified as 1.9 Tesla independent of which impedance.
Note also that the efficiency is stated only once. And it is 30%, with a sensitivity of 111 dB, written for both impedances, and for a power input, not a voltage input.
So your statement of half power/same output due to double turns is not supported by the datasheet you have provided.
So far, JBL is consistent with what I larned from woik..
John
Missed that. Did note the DC resistance doubles, so I guess I have to count the turns next time I replace diaphragms. Yes the change in BL should affect the output with the same current. So you might be right there is a bit of something going on to get the same output.
BTY Power input is misleading as it is actually the voltage that is measured and held constant. That is because the impedance is also not constant and no one uses a power amplifier as a "power" amplifier. Seems they really increase the voltage and then have to supply the increase in current as a result.
I am glad things are woiking out for youins.
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I would guess that they changed the gauge of the wire to accommodate the longer length. After all, with the same power rating, they can drop some copper.
41% more turns would show up as doubling of inductance, so you can measure good coils out of the box (and gap), and notice the doubling of the 16 ohm L over the 8 ohm L.
They specify 1 watt input, not voltage, for sensitivity. They also specify watts max.
They aren't. But thanks anyway for the thought. Hope all is well with you.
John
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Only have to make a measurement if the count gets past 20!
(Pretty sure they dropped the gauge for the higher impedance version, but if they dropped it enough to double with only 40% more wire then the current handling should decrease by about the 40%.)
Just got this from Audio Precision:
In the design of high-performance amplifiers and integrators, some analog designers are beginning to explore the virtues of cascading two op-amps running on different power supply rails within the same overall feedback loop. This architecture inherently eliminates two subtle forms of distortion: (1) input stage susceptibility to power supply interference caused by the non-linear load currents of the output stage; and (2) thermal modulation of input stage offset caused by power dissipation changes in output stage. These two forms of op-amp non-linearity are very real, and not the least bit insignificant.
Not yet posted at:
AUDIO.TST
In the design of high-performance amplifiers and integrators, some analog designers are beginning to explore the virtues of cascading two op-amps running on different power supply rails within the same overall feedback loop. This architecture inherently eliminates two subtle forms of distortion: (1) input stage susceptibility to power supply interference caused by the non-linear load currents of the output stage; and (2) thermal modulation of input stage offset caused by power dissipation changes in output stage. These two forms of op-amp non-linearity are very real, and not the least bit insignificant.
Not yet posted at:
AUDIO.TST
Beginning to explore?? People have been doing that for many years. As Scott points out some of it has been rendered unnecessary.
When I designed a computer-controlled attenuator for Harman R&D, circa 1997, sadly never completed, I used 797s and two AD811s per channel in ~parallel to drive a resistor network that was switched with Hg-wetted reed switches. It was a little tricky to compensate, but I wanted lots of drive current and wanted to remove most of the loading from the 797s.
Dear Kind, you can't use ferrofluid in anything that moves over a millimeter. It would slush around, get ejected from the gap. But, as I mentioned before, even than you shouldn't.
As to gumming up, Jan Didden had a pair of KEF|'s with FF in the gap which had dried up. The magnetic motor in that tweeter was fairly primitive, and it actually measured better with FF, than without. But with the aged FF, it was dramatic.
Vac,
I agree that the FF has problems from all the tweeters that have dried up and seized in the gap. At the same time there are plenty of Pro-audio bass drivers using fluid in long excursion drivers. You do have to design the motor for the fluid and balance the pressure on both sides of the gap and if you have fringing magnetic fields the fluid will be attracted to those and move outside of the gap. I've studied the fluid fairly well and actually designed the motor assembly to balance the pressure and make sure there was no hydraulic pressure to push the fluid out but I have just found I don't need to use the stuff, I don't burn voice-coils, it would just reduce any chance of a rubbing former when they are as long as I use. I think a double spider is a better solution to keep the former centered and not take the chance of failing fluid.
I agree that the FF has problems from all the tweeters that have dried up and seized in the gap. At the same time there are plenty of Pro-audio bass drivers using fluid in long excursion drivers. You do have to design the motor for the fluid and balance the pressure on both sides of the gap and if you have fringing magnetic fields the fluid will be attracted to those and move outside of the gap. I've studied the fluid fairly well and actually designed the motor assembly to balance the pressure and make sure there was no hydraulic pressure to push the fluid out but I have just found I don't need to use the stuff, I don't burn voice-coils, it would just reduce any chance of a rubbing former when they are as long as I use. I think a double spider is a better solution to keep the former centered and not take the chance of failing fluid.
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