Ohms and Resistors

Thread Starter

Joe1990Dirt

Joined Oct 27, 2011
1
I was wondering if it is possible to drop the ohms on a single voice coil sub using resistors. The sub is currently at 6 ohms but i wanna run it at 3 ohms?
 

Sparky49

Joined Jul 16, 2011
833
Drop Ohms using resistors?

You do realise that Ohms are the unit of resistivity, which is what resistors do?

What you're wanting to do (as far as your posts says) is the same as saying:

I want to eat a fruit salad by adding more fruit.


I think that your terminology has become mixed up. Have a quick check of what you're asking.:)
 

strantor

Joined Oct 3, 2010
5,329
The terminology is a common misnomer I have encountered in car audio circles. people will say like "you get more power if you run it at lower ohms". What people are usually referring to when they say that, they are referring to multiple speakers powered by the same amplifier. If you 2 6ohm subs in series, you get 12 ohms. if you put them in parallel, you get 3 ohms. If you have only one 6 ohm sub, and you put a 6 ohm resistor in parallel with it, you will have 3 ohms, but you won't gain anything except a hotter amp. its a bad idea IMO
 

Audioguru

Joined Dec 20, 2007
11,249
Resistors do not make sound, instead they make heat and also heat the amplifier.
A 3 ohm speaker produces double the power of a 6 ohm speaker if the speakers are the same. Double the power sounds only a little louder because our hearing's sensitivity to loudness is logarithmic.

In 1966 a car radio used output transformers (instead of bridged amplifiers) to step-up the output voltage swing to produce 4W per channel in 8 ohm speakers. 4W in 8 ohms requires an amplifier with at least a 20V power supply voltage without using the transformers.

My 2005 car uses 2 ohms speakers with bridged amplifiers for high output power of about 26 Watts (which is about 104 Whats) at clipping per channel.
 

crutschow

Joined Mar 14, 2008
25,396
I was wondering if it is possible to drop the ohms on a single voice coil sub using resistors. The sub is currently at 6 ohms but i wanna run it at 3 ohms?
In summary, a parallel resistor will lower the total impedance, but any extra power generated by the amp into the lower impedance load will just go into heating the resistor.
 

thatoneguy

Joined Feb 19, 2009
6,359
Resistors do not make sound, instead they make heat and also heat the amplifier.
A 3 ohm speaker produces double the power of a 6 ohm speaker if the speakers are the same. Double the power sounds only a little louder because our hearing's sensitivity to loudness is logarithmic.

In 1966 a car radio used output transformers (instead of bridged amplifiers) to step-up the output voltage swing to produce 4W per channel in 8 ohm speakers. 4W in 8 ohms requires an amplifier with at least a 20V power supply voltage without using the transformers.

My 2005 car uses 2 ohms speakers with bridged amplifiers for high output power of about 26 Watts (which is about 104 Whats) at clipping per channel.
Some newer cars with the upgrade sound system actually have step-up SMPS power supplies in their amplifiers now. Mostly for the sub amp in stock DVD/surround sound systems. No standard connections, though, so it isn't easy to re-purpose them, same with the displays. :(

To the OP:
Using a resistor to lower the impedance will only cause your amplifier to clip at a lower volume, the amp will be putting out more power, but none of it will be going through the speaker. The extra power will simply be heating the resistor as stated above.

If you want stiffer/louder bass, get a higher powered amplifier, and if that isn't enough, run 4 12" in parallel on a bridged output amp. Only look at the RMS power rating of the amp. If it says 1000W and only weighs half a pound, they are using the "peak" power, which is a useless parameter as nobody has a standard way of measuring "peak power". 400-500W RMS with 1 or 2 12" quality subs gives nice bass.

If you want to bass shake your windows/mirrors/doors off while still sounding good, prepare to spend several thousand dollars.
 

thatoneguy

Joined Feb 19, 2009
6,359
lol yeah "peak" power. I had a 150W rockford fosgate amp that would put my "1000W" pioneer amp to shame.
There was a stretch for a few years when the Good brands in audio were actually under-rating their amps, while the cheap ones were wildly over-rating theirs. Then in the late 90's, the ratings got fuzzy again when Rockford split between high end and more modestly priced amps (forgot their names, Punch and something else).

It was great in college to see a kid bring his "2,000W" Amp to lab and have it totally blown out of the water by a 75W/channel Coustic amp in every measurable parameter from peak power to power at 1% THD. The fun part of college were the labs when we got to play with test equipment we'd only read about in stereo magazines up until then.
 

strantor

Joined Oct 3, 2010
5,329
There was a stretch for a few years when the Good brands in audio were actually under-rating their amps, while the cheap ones were wildly over-rating theirs. Then in the late 90's, the ratings got fuzzy again when Rockford split between high end and more modestly priced amps (forgot their names, Punch and something else).
Yeah that was around '02 and my rockford was 3rd hand acquisition from the 90's. it looked like this, but wider, and minus the end caps. If I were to get back into car audio, I would hit ebay looking for another one of these before I would go to the store and get one off the shelf.
 
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