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High Current what does it mean?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=37995
Printed Date: May 04, 2024 at 5:38 AM


Topic: High Current what does it mean?

Posted By: northballer
Subject: High Current what does it mean?
Date Posted: August 23, 2004 at 11:31 PM

Do high current amplifiers need alot more juice or what. I am looking at this clif design amp but am wondering what HC is for and if you need anything special to run the amp. Also are these good for bass.



Replies:

Posted By: Steven Kephart
Date Posted: August 24, 2004 at 1:37 AM

Well in amplifier design, you can choose two ways to get power.  Power is P=EI so you can either have high E (voltage) or high I (current) and have the same power.  There are advantages and disadvantages of each.  Usually a high current amplifier will be able to handle lower impedances easier.  They will also be a little louder at the same power levels as current is what drives the speakers motor (motor force being BLi), but at the cost of a little higher distortion from the speaker and lower efficiency.

Here's a great description by my boss, Dan Wiggins about this subject:

"All else being equal, current is current, BLi=ma, and how you get that current is immaterial. In car audio we tend to have lower impedance because back in the dark ages (the 80s - were some of you even alive then?) high voltage switching power supplies were expensive. So you used the least amount of voltage possible, meaning that to maximize current flow at that low voltage rail you used low impedance drivers.

Now days, with switching FETs being cheap and plentiful, a 3 kW switching power supply is quite affordable. We stick to low impedance mainly because of market inertia. This is one area that I have a lot of hope for 42V car systems - higher voltage systems allows use with higher impedances.

Why higher impedances? Go back to the top - that whole effiency thing. What is efficiency? BL and Mms. Guess how I can increase BL for really cheap - add more L...Go to an 8 Ohm voice coil, I can double the BL for free (as compared to a 4 Ohm voice coil). Meaning I don't need as much current to generate the given force, but I do need more voltage. Of course, with a 42V rail, we can get a clean +/- 40V into the speaker without a switching power supply, and that is a solid 200W into an 8 Ohm load! Into a 4 Ohm load, we have 400W of power. Imagine a head deck that can do 400Wx4 - yes, that's the benefit we get..."

Steven Kephart

Adire Audio



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