chlutz214

I have been looking at everything i could find online to try to figure this sub/amp math and i cant find anything that really helps me... so anyone whoknows the math please help!

What part of the speaker power rating do you actually need to look at?
What role do ohms play in the combination?
How would multiple voice coils effect the math?
How do you account for multiple speakers?


I already get the idea of box and speaker size and ported/unported. I really just need to learn how to pick out appropriate amps for the sub(s).

Modme

iTrader: (17)

Here's a good website. Tons of information and calculators.

Basic Car Audio Electronics

JSolo

iTrader: (14)

If I remember correctly, ohms, is a unit of measure for electrical resistance - Ω. Most car speakers are 2, 4, 6, or 8 ohms. Generally, aftermarket speakers are 4, while subs can be 2 or 4, or even 8, depending how they're wired.

Resistance in a series circuit is a cumulative effect. So if you have two speakers in series that are 2Ω each, the effective resistance seen by the amp is 4Ω. OTOH, if you have 2 speakers in parallel that are 4Ω each, the effective resistance is 2Ω

The formula is (1/( (1/speaker1) + (1/speaker2) + (1/speaker(n) )).

What you're concerned with is matching the rms specification of the speakers to the amp. The idea is to have a balanced set, or at the minimum have an amp rated higher than the speakers. This way, you can always turn down the amp gain (to prevent blowing the speakers), but will have plenty of power (wattage) to drive them.

If you do the other way around - amp rated lower than speakers, then, because the amp will clip the signal because it lacks power, resulting in distortion and damage to the speaker.

When I had my camaro, I had a relatively simple set up.

Front - components
B pillar, midbass (~40Hz to 4kHz)
cubby hole in the hatch, 1 10" sub woofer

I had 2 amps running this setup.

Alpine mrv-f545 (125x4 rms into 4Ω), or 500x1 + 125x2 (also into 4Ω) in bridged mode
alpine amp from early 90's, 85x2 into 4Ω.

The mrv-f545 powered the front component speakers and the sub, while the other amp powered the midbass B pillar speakers. After adjusting everything and a bit of EQ tuning, the sound was superb. I did over do it on the amps. I figured better to have power in reserve than not enough.

(Which btw, if you're interested in that mrv-f545, it's listed in the classified section).

Good luck!

chlutz214

thank you for the link modme.

and thank you for the detailed explanation Jsolo.
so with the amp you mentioned as an example, you said it has 125x4 rms into 4Ω, or 500x1 + 125x2 (also into 4Ω). so going by the 2nd number i could run 1 500 RMS sub that is 4Ω AND 2 additional 125 RMS speakers at 4Ω each?

would i be able to run a 2 or 8 Ω on a 4Ω amp or does it have to end up at 4 Ω to work properly?

also do i look at the speakers "RMS" or "peak RMS"?

JSolo

iTrader: (14)

Answers in bold above.

chlutz214

right, so i look at rms, not the peak number.

and so you can use a higher resistance speaker, and you shouldnt use a lower resistance speaker, but it would be best to use a same resistance speaker?

do you know if there is any advantages or disadvantages to using a 2Ω setup vs 4Ω vs 8Ω?

UncleFunkle

Please start here. A great site. I go back to it several times.