question about impedence
08-09-2003, 12:33 PM
#2
http://www.jlaudio.com/tutorials/dvc/point.html
DVC subs allow you to buy a sub(s) that matches up with your amplifier, allowing it to run your subs most efficiently, whether it is 1 ohm mono stable/2 ohm/or 4 ohm stable. A dual 4 ohm subwoofer allows you to wire the coils in series (8 ohm load) or in parallel (2 ohm load). A dual 2 allows you a 4 ohm final load, or a 1 ohm load (series impedances add directly, parallel add inversely). For a dual 4 ohm sub paralleled, you do 1/4+1/4= 2/4 then you invert that, so 4/2= 2 ohms. Hope this helps a bit.
DVC subs allow you to buy a sub(s) that matches up with your amplifier, allowing it to run your subs most efficiently, whether it is 1 ohm mono stable/2 ohm/or 4 ohm stable. A dual 4 ohm subwoofer allows you to wire the coils in series (8 ohm load) or in parallel (2 ohm load). A dual 2 allows you a 4 ohm final load, or a 1 ohm load (series impedances add directly, parallel add inversely). For a dual 4 ohm sub paralleled, you do 1/4+1/4= 2/4 then you invert that, so 4/2= 2 ohms. Hope this helps a bit.
08-10-2003, 05:53 PM
#4
500 Watt CAFz'r
Join Date: Jan 2003
Posts: 575
Well, you can hook up one voice coil, but it will only handle half the power ...
http://www.adireaudio.com/tech_papers/dvc_subs.htm
http://www.adireaudio.com/tech_papers/dvc_subs.htm
What about driving just a single coil, and leaving the other open? Well, as you would guess, the push is weaker. The system has a peakier resonance (for the techie types, Qts increases because Qes increases).
BUT - let's drive one coil, and short the other. Guess what? Things change from the original (both coils driven) situation, but they also stay the same. The driven voice coil is pushing and pulling, as normal. But what about the shorted voice coil? Well, it's trying to keep things at rest - it's trying to resist ANY motion! The net result is the overall peakiness of the resonance is the same as it was when both coils were driven, even though we are only using half the motor (driving one coil). The other coil helps "tame" the driven coil, so that the system basically behaves the same as before.
Hey, maybe we can exploit that! Actually, we can...
Say you want to use our Shiva driver. Say you like everything about it (especially the massive Xmax!), but for your intended application, you want a higher Q. Well, this is the way: drive one voice coil. But rather than just shorting the second coil, or leaving it open, terminate it with a resistor. The result? The Qts of the driver will change from the open to the shorted Qts as the resistance is decreased. That means you can tune the Q of the driver, with nothing more than a potentiometer!
In fact, for our Shiva subwoofer, operation in this mode allows one to literally dial in a Qts from ~0.4 to ~0.80. Now THAT'S flexibility! So a dual voice driver is actually amazingly flexible. Much more so than usually pushed. Use a dual voice coil driver, and you can use a much wider range of enclosures, and even have a system that can have a "Qts" **** on it, for changing the Qtc of a sealed system on the fly, according to your tastes.
BUT - let's drive one coil, and short the other. Guess what? Things change from the original (both coils driven) situation, but they also stay the same. The driven voice coil is pushing and pulling, as normal. But what about the shorted voice coil? Well, it's trying to keep things at rest - it's trying to resist ANY motion! The net result is the overall peakiness of the resonance is the same as it was when both coils were driven, even though we are only using half the motor (driving one coil). The other coil helps "tame" the driven coil, so that the system basically behaves the same as before.
Hey, maybe we can exploit that! Actually, we can...
Say you want to use our Shiva driver. Say you like everything about it (especially the massive Xmax!), but for your intended application, you want a higher Q. Well, this is the way: drive one voice coil. But rather than just shorting the second coil, or leaving it open, terminate it with a resistor. The result? The Qts of the driver will change from the open to the shorted Qts as the resistance is decreased. That means you can tune the Q of the driver, with nothing more than a potentiometer!
In fact, for our Shiva subwoofer, operation in this mode allows one to literally dial in a Qts from ~0.4 to ~0.80. Now THAT'S flexibility! So a dual voice driver is actually amazingly flexible. Much more so than usually pushed. Use a dual voice coil driver, and you can use a much wider range of enclosures, and even have a system that can have a "Qts" **** on it, for changing the Qtc of a sealed system on the fly, according to your tastes.
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