Car audio equipment power inverter

[ericJ]

A coworker is currently running a car audio setup in his garage. He uses a jet stream brand power inverter rated at a continuous 25amps. Running a pioneer in dash and an older Cerwin Vega amp to a prefab box with 2 12” Memphis subs and no name mids/highs. He bought another amp (skar 1200 watt mono) and wants to run the
subs off of it and the highs off the other.

I’ve already told him he would most definitely need a bigger power inverter. Something along the lines of a powermax 100amp. Also told him it’s easier to just grab a stereo receiver and hook up to a pair of home audio speakers.

can anyone elaborate on the success of just adding a bigger inverter? Will it work? Is it advisable?

[billfitzmaurice]

25 amps at 12v is only 300 watts. Used receivers are plentiful and cheap. That's what I'd get.

[ericJ]

Thanks Bill, that reaffirms what I was thinking. Just trying to see if there was any way to effectively utilize all the stuff he currently has.

[billfitzmaurice]

Put it in his car?

[PWR RYD]

Just for clarity sake, a power inverter almost always refers to a device that takes 12ish Volts DC (like you have available in a car/van/truck) and converts it to a rough sine wave (AC) at 120 V to power those type of household devices. What your coworker would need is a "power supply" that converts 120 Volts AC down to 12-14ish Volts DC. I've seen some folks do that with a simple car battery and a battery charger (think Shumacker 50 Amp charger). But I really wouldn't want a lead/acid car battery in my house (maybe not so bad for his garage application).

I agree that a used home receiver found at a garage sale, on craigslist, or even at a Goodwill is a way better solution. At least for the main speakers. A cheap plate amp for the subs should trump all that car audio gear and the associated equipment necessary to use it.

[Brian Steele]

As the others have said, consider a cheap receiver instead, and a separate amp for the sub (if the receiver does not have a powered subwoofer channel). I would NOT recommend one of those "plate amps" - IMO, those are a solution looking for a problem. The same money could be used for a separate amp (or another cheap receiver with AUX IN) just to power the subwoofer.

I have an old Technics SA-EX700 receiver at home that does 100Wx6 (yup, it provides 100W to the subwoofer as well). Class H+ design. The only "flaw" is that it runs all of the channels full range, and the subwoofer channel is low-passed @ 100 Hz. I'm not sure why they didn't bother to include HP filtering for the other channels...

[ericJ]

He ended up buying a Powermax power supply but upon receiving it, it was faulty. Only put out 3 amps so obviously something wrong inside. Sent it back and proceeding with his old small power supply.
I’m building him a new box for the Memphis subs 4.2 cubic foot vented modeled in winISD. Will move that to the ground (was on a high shelf near ceiling in an old wedge shaped box not for these drivers). The indash will power the 2 way speakers (now in a separate small box). If he decides to stay with it he can upgrade the power supply. If not at least the sub box could still be powered from a home or pro audio amp in the future. I’m with you all though I would have just went with the receiver and bookshelf speaker setup 🤣

[ericJ]

Edit it was only putting out 3 VOLTS. Tested voltage with two separate multimeters to be sure. I think the voltage adjustment pot may have been faulty or there was some bad component inside.

[Steve Lee]

Battery charger and some large electrolytics . . .

[ericJ]

Final update and I’ll stop, lol.

Built a proper box for the Memphis subs after modeling in winISD. Hooked everything up tonight running off of the small power supply. A pioneer in dash, skar audio 1200 running the subs, an old Cerwin Vega running the 6x9’s mounted in the ubiquitous carpeted 6x9 box and mounted on the wall at ear level.

All said and done he was happy with the results. I’m not sure how different it would have been with the larger power supply, batteries, capacitors, etc. Gets louder than I would ever listen. The subs in the correct ported box were well behaved. After all it’s a garage setting.

Any comments on what could be expected with a larger power supply providing higher amperage? Would it make an audible difference in SPL?

[ericJ]

A few pics. The black sub on top of the larger box is my very old build of Chris Roemer’s little white sub with the Dayton sd215 8”. Box for the Memphis subs is 38x15x18.25 with a slot port. Around 4.25 cubes tuned to 36hz.

[Brian Steele]

Final update and I’ll stop, lol.

Any comments on what could be expected with a larger power supply providing higher amperage? Would it make an audible difference in SPL?

I suspect that there will be a difference in PEAK SPL. As to whether or not that would be audible, that's another matter.

If you can get your hands on one of those clamp ammeters that can do a peak-hold, you could measure minimum and peak current draw with it. Then use that to determine if a larger supply is actually required.

FWIW, my car audio system is a Pioneer 80 PRS connected to an ESX DSP which drives DIY two-way speakers in the front and rear doors and two 12" subs in a sealed enclosure via a 1.2kW amp for the subs and a 600W amp for the mids. I had it clamped recently, at "idle" and at a volume level that was uncomfortably loud for me. The idle draw was 3A and the peak current draw was 67A off the car's 12V supply. Calculated peak current draw would have been closer to 150A. The measurement suggests that I can replace the system's current 200A circuit breaker with a 100A or even 75A circuit breaker without causing any issues, something that I plan to do this year.

[ericJ]

Thanks that is very good real world info!