Amp/power supply to power 2ohm car speakers

[edub]

Hello all,

Sometimes, when you're building a cabinet, you get AHEAD of yourself - as I think I did. Regarding the audio side, I thought "hey, car speakers and amps are perfect...they have great mounts, good sound..." and I headed in that direction without first engaging my brain (regarding the power supply). So, I purchased:

1. Crunch Pounder Amp (GPV700.2), 700W on 2 channels
2. Infinity 6032cf car speakers (great sound), 2 Ohm, 180W

And then I thought "geez, I need to supply 12V DC to the amp..." and suddenly realized that the amp is typically hooked to a CAR BATTERY. The 12VDC is easy enough, but 30-45 AMPS from my home 110 outlet that has a 15A breaker? Oh crap. So, I had the bright idea that I would call Crunch Pounder and ask them to help me - and they did (EXTREMELY helpful folks there). They said "no worries, we hook these up at trade shows all the time...you just need a power supply from Kinetik Audio...the KIPS12-45" (that's 12V and 45A). Ok. How much is that? $280 retail. Oh CRAP !

My next thought was that I had literally blown $60 on the car amp that I couldn't power without a $280 power supply. Ok, so I'll look for a cheap home stereo (Sherwood RX-4105, $77) and be done with it. Then, I realized that the VERY nice car speakers I purchased were 2 OHM and the Sherwood expects 8 OHM speakers attached. OH CRAP OH CRAP !!

So, here are my questions:

1. Have any of you used a Crunch Pounder car amp (GPV 700.2) or similar and found an inexpensive power supply (adapter) that gave you 13-14V and 30-45A that hooks directly to your 110 outlet? How did you solve this problem?
2. Assuming I throw out the ground pounder for now and go with a different amp, which amp do you suggest to provide decent power (watts) to the speakers and hook up to a 110 home outlet? Obviously, it would need two (stereo) RCA inputs that come from my stereo jack on my arcade computer. And, it must support 2 Ohm speakers.
3. Related to #2, if you have a home stereo (like the Sherwood that expects 8Ohm speakers, how can you rig something to hook up 2Ohm speakers to it?

I don't mind, at this point, removing the crunch pounder amp from the system. However, I really WANT to use those infinity speakers - badly. They are perfect for the arcade machine - mounting and all.

I'm sure I'm not the only one that has run into either of these problems before - and if I am, well, shame on me for getting excited and purchasing stuff without first engaging my brain !!

Thanks,
edub

[edub]

So, I just found (on Amazon) something like this:

http://www.amazon.com/gp/product/B0036VO6G4?&tag=shopwiki-us-20&linkCode=as2&camp=1789&creative=9325

120W (max) stereo amp by Pyle. These seems PERFECT, except for it is for 4Ohm speakers. If I hook my 2Ohm car speakers to it, and therefore it draws twice the current and a given power, it could burn up this amp. Basically, if I could find a 2Ohm version of this exact product, I'd have my solution - unless someone has a completely different idea...

Again, thanks for your attention....

[gryhnd]

I'm doing just that. Check out my Rat Rod thread in my .sig

I purchased the P.S. from China via eBay for about $35 or $40 delivered.

Like this one...which may be overkill wattage wise for you but they have others.

Edit: your speakers are 180W, not your amp...but I suspect you'll find you'll never use 700W.  My setup is deafening. A cap might help you out.

[edub]

gryhnd,

Thanks for the reply. So, you use the 12V/29A power supply to provide power to a car amp, like the crunch pounder or a similar car stereo amp that is typically powered by a car battery?

I saw other 12V/30A adapters (from home 120V), but the crunch pounder guys poo-poo'd them. What is the difference between the one you recommend vs. one that looks like a laptop adapter? Or, do you think "ANY" 12V/30A power supply would work with this car amp?

Can you provide the link to your Rat Rod thread? What is a .sig?

Thanks again for your help....

edub

[BobA]

Just look at the bottom of his post for a link to ratrod.

[edub]

Ok, got it. .sig, i.e. signature. I'm bright - only took me awhile to figure that out. '-)

So, it looks like I should order a 12V DC, 30A power supply that has an 120V AC input (to plug into the wall). Even though it is CAPABLE of drawing 30A, which would blow my breaker in my house, it should only use 6-8A at the power I'll be drawing (assumption, yes, but based on the fact that gryhnd didn't even flinch when wiring his up to the jukebox).

So, realistically, ANY 12V, 30A power supply would work is what you're saying. Correct?

Thanks again for the help. This means that I can continue using the amp and speakers I bought and simply add the power supply.

Cheers,
edub

[edub]

Two last questions (famous last words!). If this works the way gryhnd says, could I "split" the 12V DC off to power ONE 12V LED as well? How does that work? Also, regarding GROUND, I assume I hook ground of the supply to the ground of the amp...no need to ground anywhere else in the cabinet or any other grounding connection - because it is grounded at the 120V AC plug that is used to power the power supply. Correct?

Thanks,
edub

[gryhnd]

30A is on the 12VDC output (12V x 30A = 360 watts), not the 120VAC input

So no worries about popping any breakers.

These units are designed more robustly than any wall wart/laptop style power supply. For example: built in cooling fan. When it gets hot from working hard, the one I have kicks in a fan...ain't no such thang in a laptop PSU. I have a similar unit powering an old 240W 4ch amp that drives the transducers ("butt kickers") in my home theater. Been running close to 3 years now and under some VERY loud conditions for long periods of time (movies aside, think several hours of Superbowl at near max volume)   

I can't say though if the power supply I use is appropriate for your setup.  My Punch amp is 400W at 2ohms, but if you look here you'll see that with my setup it's probably drawing 200W continuous due to the speakers I am using (a mix of 4 and 8ohm).

If this power supply doesn't quite cut it, you could use some 4 or 8ohm speakers inexpensively instead to reduce the max watts draw.  YMMV.

And again, a capacitor (as I have) might help you out with the loud transients and keep the power supply from getting overwhelmed.

Yes, you can easily power an LED which has a negligible draw.

PS - you might try cruising Craigslist too. I sometimes run across amateur radio guys selling off their old high current 12V PSUs. But, $40 is hard to beat :-D

[gryhnd]

I assume I hook ground of the supply to the ground of the amp...no need to ground anywhere else in the cabinet or any other grounding connection - because it is grounded at the 120V AC plug that is used to power the power supply. Correct?

yes.

I dug up the the compact capacitor I am using in my build. Only $30.

Can't speak to long term reliability yet as I am not finished, but it's working fine right now and at loud volumes I had no issues when the sub kicked

http://cgi.ebay.com/5-Farad-Car-Audio-Capacitor-Car-Gas-Saver-/300371994742?pt=LH_DefaultDomain_0&hash=item45ef90e876

[matsadona]

As already stated by gryhnd, it will not be 30 amps on the main side, since it is only power that is constant when it comes to Ohms law.
30A * 12V = 360W - So when multiplying the voltage you will get the same ratio in dividing the amps - 360W / 120V = 3A    or 3A * 120V = 360W if you like.

[edub]

Well,

I REALLY appreciate the help from all of you. Quick answers to my mystery. And, why not copy success, eh? Here's what I did:

- kept the Crunch Pounder amp and Infinity speakers (thank you)
- purchased the EXACT power supply AND capacitor gryhnd suggested (they arrive in a few days)

While my main application is MAME, if I ever add jukebox capability or anything that really pushes the "sound system", well, I'm covered.

I just wanted to make sure of one last thing:

At two ohms, the max power is 350W per speaker - 700W total. The amp has the capability of drawing that much from the supply which is only rated at 350W. If I had 4 ohm speakers, it's a perfect setup. With 2 ohm'ers, will this cause a problem I need to worry about? How can I make sure I'm safe here? I don't plan to "max it out" - just medium loudness - 99% MAME games for now. But I wanted the experts to "weigh in". Thanks.

Matsadona - you are right - only 3A at the panel. Thanks for that explanation.

Cheers,
edub

[edub]

Gryhnd,

I have a few "last" questions:

1. Given my application (MAME arcade) and the audio solution you helped me put together, how should I handle the power from the wall outlet to the power strip to the 12VDC PSU, plus the computer, monitor, powered USB hubs, etc.? Should I use a smart power strip? Switch on the side of the cab? What is your recommendation and, if you can, please explain why. Thanks.
2. I'm assuming that everything is properly grounded back to the wall outlet when using our car audio equipment - no special "hookups" to keep in mind. Right?

Thanks again for all the advice - I'm new at this and typically need most things spelled out. I just want to have a good plan, understand WHY and then make it happen.

Cheers,
edub

[gryhnd]

At two ohms, the max power is 350W per speaker - 700W total. The amp has the capability of drawing that much from the supply which is only rated at 350W. If I had 4 ohm speakers, it's a perfect setup. With 2 ohm'ers, will this cause a problem I need to worry about?

It /could/ if you crank it. I suspect thought the PSU would shut down on you. However this is one area I can't give you anything other than an educated guess on.  If I was you, I'd avoid the issue and for the extra $50 (more or less) move to some 4ohm speakers.

[gryhnd]

Gryhnd,

I have a few "last" questions:

1. Given my application (MAME arcade) and the audio solution you helped me put together, how should I handle the power from the wall outlet to the power strip to the 12VDC PSU, plus the computer, monitor, powered USB hubs, etc.? Should I use a smart power strip? Switch on the side of the cab? What is your recommendation and, if you can, please explain why. Thanks.
2. I'm assuming that everything is properly grounded back to the wall outlet when using our car audio equipment - no special "hookups" to keep in mind. Right?

Thanks again for all the advice - I'm new at this and typically need most things spelled out. I just want to have a good plan, understand WHY and then make it happen.

Cheers,
edub

1) I am using a smartstrip, yes. Mine is a USB version plugged into the PC. If you read my build you'll see that the "switch" that turns on the PC is an engine start button...but that's essentially just a normal switch. So yes...a switch on the side of the cab.

2) Grounding is not an issue for the audio equipment. The PSU has no ground (they give you a two wire plug)...no special issues.

[edub]

Thanks Gryhnd. I might have to step up to 4ohm'ers. We'll see.