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Old 15th September 2004, 06:14 PM   #1
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Default LM4780 for SubW

hey guys, will be an LM4780 (bridged) good for an Subwoofer?

will be this comparable with Class D Amps?

i read the Class D Amps are the best for Subwoofers, but a lot of hard to design it too

please someone help me
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Old 15th September 2004, 06:55 PM   #2
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What power do you need ? With one 4780 you can get 120 W / 8 Ohm, with two pieces more than 200 W / 4 Ohm.
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Old 15th September 2004, 07:09 PM   #3
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well i need at least 300-400 Watts

its the description of the woofer that i maybe ill use

Tempest combines a low Fs (18.6 Hz), medium Vas (317L), and medium Q (0.38) with an incredibly long throw (16.9mm one way) for a subwoofer driver capable of huge deep bass output. And with a 750W power rating, you can use all that displacement, too. We've run a LOT more power through this unit than what we've rated it for. Tempest should be able to take a beating!

will be great to use 4 IC in bridged mode
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Old 15th September 2004, 07:21 PM   #4
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In normal connection is " border line " practically somewhere between 250 - 300 W / 4 Ohm, 'cos rails must be +/- 40 V max. . Bigger power you get only with lower load impedance.
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Old 16th September 2004, 02:58 PM   #5
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wich relation existe between the amount of bridget ICs and power supply?


i mean, can i bridge 10 ICs for example?

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Old 17th September 2004, 01:28 PM   #6
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No, you cannot. You can only bridge 2 chips (or 1 4780 - bridge the 2 amps in it). The reason is because bridging means that the positive of two amps drive half of a speaker.

What you can do is parallel 2 sets of 5 amps then bridge them. That would give you amazingly low impedence drive.
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Old 17th September 2004, 01:38 PM   #7
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sounds nice

some math !formula" to determine how much V and Amps i need in the power supply?
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Old 17th September 2004, 02:48 PM   #8
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Why don't you use this Excel file?

http://www.national.com/appinfo/audi...gn_Guide13.xls

http://www.national.com/appinfo/audi...sign_Guide.pdf
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Old 17th September 2004, 02:52 PM   #9
Electrons are yellow and more is better!
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Seriously, it's easier to design an amp for max 10 KHz or a bit less than that and use MOSFET's. Driving MOSFET's up to 100-200 Hz requires almost nothing in power, nor in complexity.
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Old 17th September 2004, 03:50 PM   #10
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thanks dude
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