Need help choosing subs & amps from the experts

UNCFMM

Member
2005-06-16 12:40 am
USA
Need help choosing subs & amps from the experts

Okay, I've been intent on putting a system in my car since I got my Jeep back in March but to be honest I really don't know THAT much about the various systems... I've pretty much narrowed it down to two different options. If someone who knows plenty about car audio could help me decide which choice would be the best way out I would be very thankful.


My car is as follows:
- White 1996 Jeep Grand Cherokee Limited with factory Infinity Gold speakers and standard deck.


Ok, here's the first setup:

- Dual 12" Infinity 1230W peak, 300W RMS subwoofers (On sale $53.99 a piece at Circuit City)
Full Description Here


- Q-Logic standard dual 12" subwoofer enclosure ($89.99 at Best Buy)
Full Description Here

- 980W max PowerAcoustik MOSFET amp, 220W continuous 2 x 4ohms ($199 at Best Buy)
Full Description Here

Total Cost: $397.97 + Installation


The Second Option:

- Loaded MTX enclosure with dual MTX Road Thunder 12" subwoofers 400W continuous & 800W peak power, and a MTX standard dual 12" enclosure. ($129.99 at www.CarDomain.com -has anyone ever ordered from there?-)
Full Description Here

- PowerAcoustik 2-channel 1920W amp MOSFET, crossover, 2ohm stable, bridgeable, HPF/LPF, bass booster. ($184.95 @ www.CarDomain.com)
Full Description Here

Total Cost: $356.85 (this includes shipping) + installation
 
I'd go with your first setup. It will hit harder and probably sound alot better while doing it. I have 3 1230W's in a sealed enclosure and love the way they sound. Quick enough to not disturb the busiest bass lines and can really pump out the volume when I feel like it. Quick is the word, probably the best sub for the money. Everytime I hear the MTX road thunders I'm pretty let down. Just doesnt sound that good. And dont forget that the speakers in your second system arent 400W continuous & 800W peak power each but thats the total(200W RMS each).Wasnt sure if you knew but that amp looks like overkill for a 400W system. How about using the amp from the second system for the first system?
 

Originally posted by richie00boy

CEA 2006 is an industry standard way of stating/measuring power ratings.

Thank you very much Sir.
I understand it is only related to car audio amps.
I see that it should be the continuous power output in Watts RMS measured with the amp powered from a 14.4V supply.
What I cannot understand is the following.
If an amp is able to deliver let's say 10 A RMS on a 4 ohm resistive load it should be able to source to deliver at least the same amount of amperes (10) also on a 2 ohm load.
Am I wrong ?
This figure of the max peak current is my present and recurring nightmare.
It seems something like a secret.

Thank you very much.
Kind regards,

beppe
 
Yes if it can do 10A with 4R load then it will be able to do the same current with heavier load. But bear in mind that keeping current the same and halving load impedance means that the output power is also halved, just that the required voltage swing is reduced to 0.707x that of the lighter load.

So if voltage swing is to be maintained the supply must be capable of supplying double the current when confronted with half the load impedance. If it can do this then the output power will also double.

Also to take into account is to what extent can big load increases can be tolerated and how long the power supply can sustain increased demands, which is what your proposed peak current capacity is all about. But it can be misleading as a big peak capacity does not guarantee a decent steady-state capacity.
 
richie00boy said:

Yes if it can do 10A with 4R load then it will be able to do the same current with heavier load.
But bear in mind that keeping current the same and halving load impedance means that the output power is also halved, just that the required voltage swing is reduced to 0.707x that of the lighter load.
So if voltage swing is to be maintained the supply must be capable of supplying double the current when confronted with half the load impedance.
If it can do this then the output power will also double.
Also to take into account is to what extent can big load increases can be tolerated and how long the power supply can sustain increased demands, which is what your proposed peak current capacity is all about.
But it can be confusing as a big peak capacity does not guarantee a decent steady-state capacity.

Thank you very much indeed again Sir.

Maybe you can think that I am quite obsessed by this thing of the current available from an amp, but my very limited and humble experience tells me that the final sound, when the speakers are driven by a so-called high current amp, has a remarkable authority. Very very nice indeed.

Thank you very much again.
Kind regards,

beppe
 
No problem Beppe. There is nothing wrong in doing research to verify your own experiences.

In fact, although some people have told you to change drive unit in your speakers, the fact that you have achieved your perfect sound with these speakers when used with a specific amp says to me that you do not need to touch your speakers. Rather you are correct in your quest to search for the right amp.
 
richie00boy said:
No problem Beppe.
There is nothing wrong in doing research to verify your own experiences.
In fact, although some people have told you to change drive unit in your speakers, the fact that you have achieved your perfect sound with these speakers when used with a specific amp says to me that you do not need to touch your speakers.
Rather you are correct in your quest to search for the right amp.

Dear Sir,
I would like to thank you for the umpteenth time for your generous, friendly and extremely valuable advice.
Kind regards,

beppe