Same Car Circuit But Less Watts With A New Amp

[ThatM1key]

More then a year ago I replaced my car factory amp with a Sony XM-GS4 (3 Channel Mode, 2 Front Speakers and 1 Subwoofer) using the factory wires (15 Amp via Fuse). I have 2 power mods that brings my car's running voltage to 15 volts. Despite 3 speakers and an amp sharing only 15 amps worth of juice with old wire, it did extremely well. It felt like it had more then 225 watts worth of power and frequency range was very good. My headunit offers a good 5V pre-output.

A few years ago, I gotten a NVX-NDA102 (Monoblock) for Christmas and I missed having 4 speakers in my cabin, so I ventured to have a 2nd circuit installed. The 2nd circuit runs on a different fuse using a fuse tap (15 amp also) using 12 gauge CCA. I gave the new circuit to my Sony amp since the old factory circuit did well and didn't want to risk losing power to a short 16 gauge fuse tap. So my NVX is running off the old factory wire and its just worse. Despite the NVX amp having to deal with only 1 speaker, the bass frequency range is all over. I'm not expecting the 750 watts RMS but I am expecting at least the same watts like my Sony amp did. With the Sony amp, all the bass frequencies were the same (With a small 40hz bass boost), 90s rock hit hard, 90s hip hop was balanced, 2010s pop had explosive bass, 70s rock had that smooth bump. This NVX amp was picking bass frequencies like a kid at a school cafeteria, 90s rock sometimes hit, 90s hip hop had really good or non-exist bass (Nothing in-between), and only 2010s pop had good bass. To achieve any good bass, I had to crank my car radio's sub channel to +10 max and NVX's bass boost to max, and still felt underwhelming. I had the right settings, 70hz crossover, 5V preamp setting, bridged speaker wires, did not use amp's external gain knob (Because it ran at max without it anyways). Despite both amps being Class D's, the NVX amp felt like it didn't like only having 15 amps to sip on while the Sony amp gladly didn't mind it.

I have 4 ideas.

1. Wait for the right time, cut a hole in the firewall and use proper gauge OFC wiring for the NVX-NDA102. Pray that the NVX actually performs well when its fully stuffed of power.
2. Combine both circuits (Parallel) and only use the Sony XM-GS4. Old setup but with more power. Technically a no-no in the electrical world.
3. Swap out the NVX-NDA102 for a Sony XM-GS1000 using the new setup. Requires money but a better chance of doing well on 15 amps since its a Sony and also no worries of Idea 1.
4. Install a 20 amp fuse in the new circuit and move the NVX to that and revert the Sony XM-GS4 back to the factory power wiring. Fuse tap would probably not like that.

Wanted to see what you guys thought about this weird situation.

 

[DVDdoug]

That's a bit confusing...

Do one or both of your amps have volume/gain controls. If so, turn down the gain on the main amp. I sounds like the monoblock has less gain so although it's capable of more output than your main amp, you're not getting as much out of it. The sensitivity of your subwoofer is also unknown and given the same power, it's probably not as loud as your main speakers.

You don't need "OFC" wire. Regular copper is fine and it has lower resistance than CCA (assuming the same gauge). Heavier gauge wire also has lower resistance. The voltage drop across the cable depends on wire resistance and current through it (Ohm's Law). You can measure the voltage at the amplifier with a multimeter but meters don't respond instantly so you might "catch" short duration voltage drops. (That should be measured when the amp is pumping-out power... When there is little or no output the current draw will be low and there probably won't be any voltage loss through the cable.)

If you're not blowing fuses you don't need a bigger one. 750W at 12V is 62.5 Amps (750/12) but you aren't putting-out full-power continuously and a 750W continuous test-tone would likely burn-out the woofer, even if it's rated for 750W. Speakers are rated for program peaks, not continuous tones. (But you can't really trust the ratings on speakers or amplifiers.)

 

[ThatM1key]

That's a bit confusing...

Do one or both of your amps have volume/gain controls. If so, turn down the gain on the main amp. I sounds like the monoblock has less gain so although it's capable of more output than your main amp, you're not getting as much out of it. The sensitivity of your subwoofer is also unknown and given the same power, it's probably not as loud as your main speakers.

The Sony does not have gain control but the NVX monoblock does although it runs at max without the cheap external knob plugged in. My headunit does feature gain channel for the front and rear but if I down the gain on those and increase volume, they could raise the noise floor.

You don't need "OFC" wire. Regular copper is fine and it has lower resistance than CCA (assuming the same gauge). Heavier gauge wire also has lower resistance. The voltage drop across the cable depends on wire resistance and current through it (Ohm's Law). You can measure the voltage at the amplifier with a multimeter but meters don't respond instantly so you might "catch" short duration voltage drops. (That should be measured when the amp is pumping-out power... When there is little or no output the current draw will be low and there probably won't be any voltage loss through the cable.)

At the front of the car its about 15.1 to 15.2 and at the rear (while jamming) its always a smooth 14.8 . My sensitivity is: Subwoofer 86db, Front 93db and Rear 96db.

If you're not blowing fuses you don't need a bigger one. 750W at 12V is 62.5 Amps (750/12) but you aren't putting-out full-power continuously and a 750W continuous test-tone would likely burn-out the woofer, even if it's rated for 750W.

Even though the NVX is rated 750w, I was expecting between 200 to 300 watts through my wiring setup as my Subwoofer can handle 300w rms. (Wired DVC together at 2 ohms). If I did have the best wiring and with the current sub, I can only spring 500 watts rms.

Speakers are rated for program peaks, not continuous tones. (But you can't really trust the ratings on speakers or amplifiers.)

Watt ratings (Even if its the obvious) are still more honest then headunit SNR. Regardless if its a $100 headunit or a $1000 headunit, they always have the same SNR/DR of 89-93db, so its hard to tell if it can actually pump out that clean signal as mine sounds like its about 13-bits.

 

[ThatM1key]

Bit of an update. I used my headunits gain control to fix the problem. Although it's a lot of punch for cheap money, the gain hunger is just too much. My front/rear gain is almost to the lowest, headunit subwoofer boost set to max, amps bass boost set to max and amps gain also max. I feel like if I gave this NVX amp all the gauge of wire it wants, it would still do the same gain problem.

Sure the NVX and Sony is a weird combo but I learned something. The NVX is the "I can build a car that has a 1,000 hp for way cheaper" while the Sony is "Somewhat Pricey, lower power but its a well tuned car". I can see why amirm loves Sony gear and I myself have owned various Sony products.

Edit: Headunits subwoofer gain is negative only like the front/rear gains.

 

[Doodski]

cut a hole in the firewall

This can be dangerous. Make sure you use a rubber grommet to protect the wire from the sheet metal edge. Or find a existing larger grommet with enough room for one more 12G wire and put the wire through that grommet. I have seen one time where the wire shorted to chassis at the firewall and the 14G wire insulation melted right off the red hot 14G wire and could have damaged parts of the car with the red hot bare wire. So make sure you use a fuse at the battery too. This occurred with a customer's installation and he wanted me to fix the wiring issues and so I did.