TheRadioFlyer

The equipment is already chosen:
Amp: JL HD 900/5 Class D (Sub channel gets 500x1 1.5-4ohm stable)
Subwoofer: JL AUDIO 10TW3-D4 (dual 4 ohm voice coils)
Enclosure: 0.48 cuft sealed custom enclosure.

Question: I can wire the voice coils in parallel to get a 2 ohm load or in series to get an 8 ohm load. Is there any performance difference between these wiring options?

GettnBetter

2 ohm's will perform substantially better than 8 ohms in terms of sound pressure level. From the description the AMP should be able to handle 2 ohms. Worst case, the amp goes into a safety mode and just becomes silent..

TheRadioFlyer

I'm curious HOW

GettnBetter

Going back to electric school here and i'm a bit foggy with my math but a 2 ohm load has lower impedance than 8 ohms. Means the amp can deliver more watts from the same input voltage. Formula is I=V/R where I is current which equals Voltage divided by resistance. Since resistance at 2 ohms is lower, and we're assuming the voltage is constant, the current goes up. Current in this case equates to more watts as long as the AMP can handle it.

TheRadioFlyer

the amp is stable down to 1.5 ohms, so it should handle a 2 ohm load just fine. Also the sub's only rated for 400 RMS so I'll be running the amp gains VERY conservatively to protect the sub.

GCG

As GettnBetter explained, changing an amplifier's load will affect it's capacity to deliver power.

Power and Load are inversely proportional: P = U² ÷ R, so ideally in a Conventional Amp, by halving the load it could provide up to twice the power. In reality, physical limitations (power supply, output stage) kick in first and power gets capped before reaching the theoretical value, unless it is a very high end equipment designed to handle this.

In your case, this amp has a special feature where what was explained above doesn't apply. It's called R.I.P.S. (Regulated, Intelligent Power Supply) and it keeps the amp's power delivery capability constant over a wide range of vehicle voltages and load impedances:

• Main Channels
  • 4 x 100w RMS @ 4 ohms
  • 4 x 75w RMS @ 1.5 to 3 ohms
• Subwoofer Channel
  • 1 x 500w RMS @ 1.5 to 4 ohms

R.I.P.S. works by detecting the driven impedance and monitoring the car's voltage, then it adjusts the power supply output so the amp always deliver power as per its specs.

Wiring your subwoofer dual voice coil in series to get 8 ohms will put it at a value not stated in its specs, while going parallel to get 2 ohms is safely within range, although it won't provide more power

knewblewkorvette

I do not claim to know everything but I do know car stereo's. In my five vehicles I have:
Two 18"
One 13.5"
Ten 12"
For a total of thirteen subwoofers backed by 5100watts rms....boom!
That being said, you want to wire your subwoofer in PARALLEL! Yes, you will be putting 500 watts rms into a 400 watt rms speaker but you should be fine. Though, if you box was ported, I might worry a little.

GCG

As a curious note, because of the way R.I.P.S. was implemented in this particular amp, to get the full 900w RMS that it can provide, the 4 main channels have to be driving 4 Ohms speakers.

If 1.5 to 3 Ohms speakers are used, instead of providing more power like a conventional amp would do, it would go down 100w RMS (25w per channel)

grampi50

The sub channel on this amp provides 500 watts into 1.5 - 4 ohms. You can connect in parallel to both VCs for 2 ohms, or connect to one VC for a 4 ohm load, and the amp will still be pushing 500 watts to the sub. The extra 100 watts over the sub's power rating shouldn't hurt it at all, unless you run it at full power constantly...

02BlownZ06

Yep, that's a no brainer. Wire in parallel for that configuration, which is absolutely perfect with the amp stable to 1.5 ohms. Should pound quite well.

GCG

Actually, wiring just 1 VC in a DVC speaker is not recommended at all. The 3 valid wiring configurations for a DVC speaker are:

• parallel
• series
• independent

Using just 1 VC will cause a 3db loss of sensitivity, which is significant. That means that twice the power would be needed to make it play as loud as it would with both VC correctly wired.

In addition to that, it's power handling capabilities would be halved, so now it wouldn't be just 100w over its rated power: it would be 300w.

These are just the main reasons. There are more parameters affected that greatly impact the speaker's enclosure calculations and can result in very poor performance if they are not compensated.

More technical details here in case someone is interested in going deeper