Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: skyclad on February 26, 2010, 09:00:26 pm
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I just saw a picture of a JBL D130 F with stated impedance of 8 - 16 ohms. I couldn't see by the picture but am guessing is has one positive (black for JBL) terminal for 8 ohms and one for 16. What a great idea! Why don't more speakers have this feature?
sky
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I am sure it is not dual-impedance.
If you don't use ALL the copper in the magnet gap, efficiency goes away.
There are dual-4-ohm windings for car subwoofers. These can work fine when both coils are used; either as 2 ohms or as 8 ohms. (In car-sound which is stereo and where amp-channels are cheap, the one cone is often driven with two 4-ohm amps.) This also works because small woofers must be very inefficient. But trying to wind a 8/16 coil pretty much ensures complicated and lossy external re-connections, or far more mass in cone and magnet than you would want.
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Standard terminals. JBL used a 6.9 ohms voice-coil and called the D130 a 16-ohm model because it's average Z was closer to 16 than to 8 ohms. The K130 reconed or aftermarket 8-ohm versions are fitted with a 5.6 ohms VC.
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here's the one I was talking about -
(http://gallery.me.com/paulnabors/100051/JBL-20D130F-208-16/web.jpg)
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Pretty standard. The electrically identical Fender version was rated at 8-ohm.
(http://www.aingeal.com/D130F.jpg)
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Standard terminals. JBL used a 6.9 ohms voice-coil and called the D130 a 16-ohm model because it's average Z was closer to 16 than to 8 ohms. The K130 reconed or aftermarket 8-ohm versions are fitted with a 5.6 ohms VC.
Speaking of that I have a 15" JBL 130A marked 16 ohms that measures about 5.8 ohms