Resistance vs Wattage Question
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=29595
Printed Date: August 26, 2025 at 9:10 AM
Topic: Resistance vs Wattage Question
Posted By: jtoona
Subject: Resistance vs Wattage Question
Date Posted: April 03, 2004 at 3:24 AM
A friend of mine just picked up a DVC Infinity Kappa Perfect DVQ sub and I was helpin him look for a sutable amp for it. Well he can run it at 2 or 8 ohms and it takes 400W RMS. Now all the 2 channel amps I have seen are rated at 4 ohms in their bridged mode. My question is, if you were to run this sub wired up at 8 ohms on an amp rated at 400x1 @ 4 ohms, will the power going to the sub be cut in half? Looking at Ohm's law, it seems this is the case, but I was wondering if the practice verifies the theory. I would really like to set him up a nice system and have him not worry about anything. Thanks for any help on this.... Oh and would you guys reccomend used the line level inputs, or using a line output converter. We're going to be hooking it up to a stock head unit and I just wanted to know some opinions on both sides. Thanks again.
Replies:
Posted By: Clean Install
Date Posted: April 03, 2004 at 3:38 AM
have you guys looked into a mono amp at all? yes the wattage would be half ------------- If we learn from each success and
each failure, then we can improve ourselves
Posted By: jtoona
Date Posted: April 03, 2004 at 3:43 AM
Yeah I think that's what we're gonna end up doing. All this about 2 4 and 8 ohms is makin me crazy. So I told him to go with a mono sub with some speaker level inputs... I think he'll be happy after we build his custom box and hook him up right!
Posted By: t_808
Date Posted: April 03, 2004 at 3:55 AM
as far as whether to use line level or an output converter , always use the line levels. using an output converter takes an already amplified signal from the head unit (which isnt as clean a signal as an external amp provides)cuts this down to between 500mv-2volts so it can be amplified again,which puts more noise there too.(output converter)
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t-win
Posted By: customsuburb
Date Posted: April 03, 2004 at 7:12 PM
It dosn't really matter if you use a line level convertor or the amps high level inputs. If you buy a descent amp then the high level inputs on the amp should be fine. I would use a line level convetor if you dont have speakers close to your amp that are are accessible or if your amp dosn't have high level inputs. Nothing is wrong with using a line level convertor, it should not degrade the signal, unless your rca cables are run next to power cables and that could cause interference. If your amp has high level inputs then it bassically has a line level convertor built into it. For the infinity sub I would use a good mono amp like the alpine MRD-M301
Posted By: auex
Date Posted: April 03, 2004 at 7:25 PM
jtoona wrote:
Looking at Ohm's law, it seems this is the case, but I was wondering if the practice verifies the theory.
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Posted By: forbidden
Date Posted: April 03, 2004 at 7:57 PM
Infernal ohms laws and physics, why can't I have things the way I want.
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Posted By: Alpine Guy
Date Posted: April 03, 2004 at 8:09 PM
If your on a budget also look at the alpine mrp-m350, it puts out 350 wrms at 2 ohm, and the next step up is the mrd-m301 (this years model) and the mrd-m300 (last years). They all have high and low level inputs. ------------- 2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
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