exactly what the title says, what would happen if i were to run an 8 ohm sub rated at 125 watts at 4 ohms?

 

if it is a DVC sub with 2 8 ohm voice coils then u can run it at 4 ohm. otherwise it is impossible (i think) if it is a 8 ohm svc sub then thats what the amp will read it as and will send the power accordingly. unless there is some other method i have never seen b4 there is no way you can disguise a 8 ohm load as a 4ohm

 

correct me if im wrong, depending on amp, it would cut the power rating in half. so u would get about 75 watts to it.

 

i sure as hell wouldn;t want to do that

 

what is the RMS and what type of sub is it?

 

The sub is a Kicker Comp vr10-8, it is rated at 125rms.

 

I have got some info on another one of my posts that i should bridge the two subs to the amp so it will read as 8 ohms. That way i'll get 250 watts from each.

 

ah thats a DVC that means if u wire it parrelell it will be ran as a 4 ohm load

whats the rms on your amp for a 4 ohm load and what type of amp is it?

 

the amp is a rockford fosgate 501s, at 4 ohm it is 125rms or 250 rms

 

I think i might return the subs and either get the 4 0hm version or go ahead and get credit for them and buy 2 better subs that will handle 250 rms better

 

my mistake there, at 40hms, 125x2, at 2 ohms 250x2

 

oh ouch

hummm let me look at the specs of the amp

 

ok it say that it has a peak bridged RMS power of 500X1 watts, im guessing thats at a 4 ohm load. u shoudl be fine as far as teh RMS being 125 on your sub i believe tahts per voice coil thus the rms would be 250

this is your amp http://www.sounddomain.com/sku/ROC501S


i couldnt find any specs on your sub are u sure its a VR with two 8 ohm coils?

 

it is a single coil. Right now i am looking at 2 MTX Audio Thunder6000 series 10" single coil subs. They are rated at 250rms and for two i could get them at 170 from sounddomain.com

 

if its a single coil its a c10 not a vr

DONT GET MTX subs NOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!

kicker is teh best u can get under 100 bux

ive gone through 11 subs trying to replace my kicker
stick with one or 2 kickers preferable one c12 4 ohm

my gosh my was beautiful

 

dont listen to anyone. they dont now wut theyre talking about. this is wut u do. since u have subs at 8 ohms each, run it parallel connection to the amp. which does 250. when u wire it into parallel, it will make the connection to te amp into 4 ohms. then u will get 250 from the amp and since u have 2 subs it will share the power which will make 125 to each sub.

stop re-asking the same ******* questions. go do that and stop asking anymore questions.

 

someone's a little pissy, but thanks for the help

 

Well actually you could run a good power resistor in parrellel with the sub and it would give you 4 ohms plus one other side effect. It would raise the Q of the speaker quite a bit.

Whats Q? Well its the quality of resonance at the resonant point of a driver.



So lets say you have a speaker that has a Fs of 60Hz (I know not something you guys would admit too, but its highly realistic) and the sub has a Q of 0.33. It would have a frequency response something similar to 1 in the picture. You can see it starts to roll off at 200Hz and by 70Hz your down by 12dB, which aint too bad for music, but many of you would probably be turning that bass up for the extra umph. Plus many of you set your Low Pass filters in the 100-120Hz range anyways so everything above that doesn't matter much.

Anyways back to the Q. Number 2 is a Q of 0.6 and 3 is a Q of 1.0. You can see that as the Q increases the freq response gets amplified around that point. Now this isn't very HiFi, but what it does give you is a very pronounced effect in the 120-80Hz range, which is the bass that you percieve as being the loudest, because you can feel it and hear it. Also notice that at 70Hz on Q1.0 your at -9dB, while the Q0.33 is at -12dB, well that translates into half the power needed to make 1.0 the same volume as 0.33. So now 50Watts is as loud as 100Watts was on the stock driver. Of course were doing this by adding a power resistor in parrellel, so thats gonna soak up some power, but the Freq response will have the biggest effect.

Remember your results may vary, please consult your physican, void in Montana, family and freinds are not eligible. This is food for thought.

There are better ways to extend low end, this is just one easy way.

EDIT: One thing I should add. Although a 8 ohm speaker and a 8 ohm resistor equal 4 ohms perfectly when in parellel, I should note that increaseing the resistance of the resistor will channel more current the driver, since it has less resistance, but will have little effect on the overall resistance.

for example
driver.....resistor.....parellel ohms
8...........8..........4
8...........9..........4.235294118
8...........10........4.444444444
8...........11........4.631578947
8...........12........4.8
8...........13........4.952380952
8...........14........5.090909091
8...........15........5.217391304
8...........16........5.333333333
8...........17........5.44
8...........18........5.538461538
8...........20........5.714285714

Plus as the resistor gets bigger more power will be diverted to the driver since electrons flow through the path of least resistance.



Modified by Westrock2000 at 6:30 AM 1/10/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by brickonwheels &raquo;</TD></TR><TR><TD CLASS="quote">someone's a little pissy, but thanks for the help</TD></TR></TABLE>

Pissy perhaps, but the most dead-on do what he said and get on with enjoying your kickers

 

have had excellent results with MTX and Kicker subs - its all about the box! Not just the sub. The reason the guy got a little "pissy" is that this is the most common problem in car audio - people think they know something and then apply it wrong, then someone else has to mop up the mess for something that should have been as simple as he explained it in his post the first time. You are just collateral damage. The good news is that if you do what he said (providing the subs are in the proper box/enclosure) your setup should rock!

 

Why do resistors only start having an effect at 80Hz? Doesn't seem like that is the target frequency of any music I listen to on a sub.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Torridcivic &raquo;</TD></TR><TR><TD CLASS="quote">Why do resistors only start having an effect at 80Hz? Doesn't seem like that is the target frequency of any music I listen to on a sub. </TD></TR></TABLE>

The resistor is doing nothing...its mearly emphasizing the sound of the speaker. The speaker has a resonance at that frequency...remember it was a hypothetical setup, your results may vary. That was a sealed enclosure set for 0.707 box Q. It could be totally different in a large ported enclosure tuned to 30Hz.

By saying you don't listen to much music in the 80Hz range what do you mean? Thats where most music bass is, in the 40-120Hz range....more like 50-100Hz.

 

i don't think he would be going for the resistor method, he just needs to read an audio book and his problems will be answered