40767
From: sumit, [barco-34-152-16-del.barco.com]
Subject: sloted magnet motor
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United States Patent no. 5,070,530 ( http://www.audioannals.com/05070530-Grodinsky-etal-txt.htm )describes a sloted magnet motor design. Does these kind of structure have an audioable advantage in subwoofer frequencies? I have the pictures ready to mail if someone wishes not to search the net.I don't know how to post it here. Thank u all for your efforts |
40781
From: Brian, [216-110-115-211.caribsurf.com]
Subject: Re: sloted magnet motor
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Looks interesting, though I thought that there was an easier method for dealing with eddy currents - copper-cladding the pole piece. The shunt resistor idea sounds a bit hokey to me though. The source impedance of the amplifier does a much better job of damping the driver's motion. Easy to test: using your favorite subwoofer, turn off the amplifier and tap on the cone. Then, turn back on the amplifier, set its volume control to zero and repeat the cone-tapping test. It should sound radically different - the amplifier's source impedance is now considerably damping the cone's movement. |
40790
From: djk, [tc111.cedar-rapids.net]
Subject: Re: sloted magnet motor
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"The shunt resistor idea sounds a bit hokey to me though" Its for use with tweeters, the cap blocks any amplifier control for them (unless using series crossovers). "Looks interesting, though I thought that there was an easier method for dealing with eddy currents - copper-cladding the pole piece." Takes a whole lot of copper for a big woofer, increase in gap volume requires a much bigger magnet, and the copper acts like a shorted turn on a transformer bleeding off power. Grodinsky is very talented. He was involved with the Koss electrostatic speakers, RG Dynamics expander, was concerned with power supply diode noise 20 years ago and has a patent for reducing same, 10 years before bi-wiring existed he had a reason for why it did something ( Thus the out of phase back EMF voltages from the separate speaker drivers are coupled across this common impedance to each of the other speaker drivers. In particular, the low frequency driver of the woofer generates the largest back EMF and the most distortion.), although his solution is different. |
Responses:
None
40788
From: sumit, [barco-34-152-16-del.barco.com]
Subject: Re: sloted magnet motor
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thanks Brian. what do u think about- 1)" It is also well-known that increasing the magnet size for a given loudspeaker driver design makes the loud-speaker sound slower and less responsive. This has been attributed to the additional magnetic back EMF damping of the more powerful magnets. In reality, some of this effect is from increased coupled signal losses in the larger magnets, a fact which has heretofore not been recognized by the prior art. Slotting the magnets so as to interrupt AC magnetic flux paths, in accordance with the invention, eliminates these losses and enables high efficiency, large magnet structures to exhibit exemplary transient response." 2-" the shunts shown at the bottom comprise single strips of magnetically permeable material that bridge magnet 10 and bucking magnet 44. The shunts should not electrically connect the top and the bottom plates and may be fabricated from 0.040 to 0.125 thick steel. From 3-6 shunts, equally spaced around and bridging the perimeters of the main magnet and of the bucking magnet, will produce a reduction in distortion. " thanks |
Responses:
None
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