You have an Alpine type X 1243D subwoofer you are trying to decide if running it at a 2ohm load at max power or a 4ohm load at two thirds of its power range will work better?

Answer 1

Multiple subs wired together must be the same coil type and impedance. If they’re not, the power won’t divide evenly between them, and some subs would probably be over-powered while others get under-powered. If you want to run different types of subs in a system, each type needs to have its own separate amp. Then, multiply the number of subs you have by the RMS rating of each, to get their total RMS rating. You want to make sure the amp you choose will supply no more than the sub system’s total RMS rating. Figure out the possible total impedance(s) that the subs can be wired together to form.

(SVC = single voice coil, 1 pair of terminals; DVC = dual voice coil, 2 pairs of terminals.) 1 SVC 2-ohms can only have 2 ohms of impedance

1 SVC 4-ohms can only have 4 ohms of impedance

1 DVC 2-ohms can have 1 ohm or 4 ohms of impedance

1 DVC 4-ohms can have 2 ohms or 8 ohms of impedance

2 SVC 2-ohms can have 1 ohm or 4 ohms of impedance

2 SVC 4-ohms can have 2 ohms or 8 ohms of impedance

2 DVC 2-ohms can have 2 ohms or 8 ohms of impedance

2 DVC 4-ohms can have 1 ohm or 4 ohms of impedance

3 SVC 2-ohms can have 6 ohms of impedance

3 SVC 4-ohms can have 1.3 ohms of impedance

3 DVC 2-ohms can have 1.3 ohms or 3 ohms of impedance

3 DVC 4-ohms can have 2.7 ohms or 6 ohms of impedance

4 SVC 2-ohms can have 2 ohms or 8 ohms of impedance

4 SVC 4-ohms can have 1 ohm or 4 ohms of impedance

4 DVC 2-ohms can have 1 ohm or 4 ohms of impedance

4 DVC 4-ohms can have 2 ohms or 8 ohms of impedance Look for an amplifier that can put out power up to the RMS wattage at an impedance load the subs can be wired to form. 8 ohms — figure on the amp putting out half the power it would at 4 ohms

6 ohms — figure on the amp putting out three-quarters of the power it would at 4 ohms

3 ohms — figure on the amp putting out the average of what it would at 2 ohms and at 4 ohms

2.7 ohms — figure the same as for 3 ohms, and add a few watts

1.3 ohms — use the 1-ohm spec and take away a few watts Example:

You have two Alpine S Series S-W8D4 8" subwoofers and you want the right amp for them.

They are DVC 4-ohm subs rated at 300 watts RMS each.

Two 300 watts RMS subs together need a maximum total of 600 watts RMS.

Using the chart in Step 2, 2 DVC 4-ohm subs can be wired together to form a 1-ohm, a 4-ohm, or a 16-ohm load.

The last is too high a load to be practical, so you’ll look for an amp that can put out up to 600 watts RMS into either a 4-ohm load, or a 1-ohm impedance load:

up to 600 watts RMS x 1 at 4 ohms, or

up to 600 watts RMS x 1 at 1 ohm

Among Crutchfield’s selection of amplifiers you’ll find:

Memphis Audio PRXA600.1 — 600 watts RMS x 1 at 1 ohm

JL Audio JD1000/1 — 600 watts RMS x 1 at 4 ohms

Kicker KEY500.1 — 500 watts RMS x 1 at 1 ohm

Any one of these high-quality amplifiers would work well with those subs. It doesn’t matter which impedance an amp plays through — 600 watts RMS through a 4-ohm load produces the same volume as 600 watts RMS through a 1-ohm load.

You have a Memphis Audio SRX500D.1 amplifier and you want it to drive two subwoofers

The amp is capable of 350 watts RMS x 1 at 4 ohms and 500 watts RMS x 1 at 2 ohms.

Let’s say you choose to maximize the amp’s potential and want the system to put out 500 watts RMS. This means your subs have to be wired to form a total impedance of 2 ohms.

Two subs on a 500 watts RMS amp will want about 250 watts RMS each.

So you’ll look for subs each rated for 250 watts RMS or more.

Using the chart in Step 3, for two subwoofers, a final 2-ohm load can be achieved with either two SVC 4-ohm subs or two DVC 2-ohm subs.

So, you’ll look for two subs that are either SVC 4-ohms or DVC 2-ohms, rated for at least 250 watts RMS each:

2 SVC 4-ohms, at least 250 watts RMS, or

2 DVC 2-ohms, at least 250 watts RMS

Among Crutchfield’s selection of subwoofers you’ll find:

You have a Memphis Audio SRX500D.1 amplifier and you want it to drive two subwoofers

The amp is capable of 350 watts RMS x 1 at 4 ohms and 500 watts RMS x 1 at 2 ohms.

Let’s say you choose to maximize the amp’s potential and want the system to put out 500 watts RMS. This means your subs have to be wired to form a total impedance of 2 ohms.

Two subs on a 500 watts RMS amp will want about 250 watts RMS each.

So you’ll look for subs each rated for 250 watts RMS or more.

Using the chart in Step 3, for two subwoofers, a final 2-ohm load can be achieved with either two SVC 4-ohm subs or two DVC 2-ohm subs.

So, you’ll look for two subs that are either SVC 4-ohms or DVC 2-ohms, rated for at least 250 watts RMS each:

2 SVC 4-ohms, at least 250 watts RMS, or

2 DVC 2-ohms, at least 250 watts RMS

Among Crutchfield’s selection of subwoofers you’ll find:

Alpine W10S4 10" — SVC 4-ohm, 250 watts RMS

JL Audio 12W0v3-4 12" — SVC 4-ohm, 300 watts RMS

Kicker 44CWCS104 — SVC 4-ohm, 300 watts RMS

Rockford Fosgate R2D2-10 10" — DVC 2-ohms, 250 watts RMS

Hope this helps! (: