Powering Crazy Car Setup In Bedroom

[JohnnyJ]

Hello Everyone

I have been thinking about what I want to do in terms of audio in my bedroom, and I decided that I will try this. I know it is a bit insane but it has been done before, and this is exactly what I want to do.

Okay so I found this other posting board (forum), and a user posted the following:

_________________
I went out and grabbed 3 lead acid car batteries from a junk yard for $5 each. They all worked enough to hold a charge and start a car.
I checked the water and electrolytes in the batteries and made sure they were up to par.
Went to a truck (big rig) supply store and bought heavy guage wire and battery terminals. They are MUCH cheaper here than at an car audio store. Compare 3 or 4 dollars to 35 or 40 for wire. I also picked up a 12 volt battery charger that had settings for "trickle" 3amp 5amp and 10amp. Total spent so far was around $65.
Set all 3 batteries on a piece of wood. Avoid concrete or carpet. Concrete is bad for the battery and carpet isn't good if the battery leaks.
Wire all 3 together in parrallel. That's positive to positive to positive to amp positive and with another (different) wire hook negative to negative to negative to negative of the amp. Now hook the charger to one of the batteries.
Use a small piece of wire to connect your "remote" lead on the amp to the positive of the batteries and your amp should start right up. Leave the changer in the trickle mode at all times and you should be able to jam for hours on end without pulling the batteries too low. When you are not using the amp remove the "remote" wire and they charge back up.
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...now, I know that it seems like a big hassle etc, but I really want to do this and need some help. If I did the same this guy did, except buy brand NEW equipment, 3 car batteries (12volt +), a battery charger [just plugged in at an ordinary house wall plug outlet], and the necessary wires/leads - would it actually work?

I have a Pioneer TS-W5000SPL Subwoofer, a Pioneer PRS-D5000SPL Amplifier and a SPL Optimized Ported Enclosure Subwoofer Box. I need to purchase: home studio speakers (x2), a car head unit and the rest of the necessary equipment to make this work. Whatever other equipment I need, please let me know.

The subwoofer is EXTREMELY powerful at 5000watt/2000rms, and the amplifier can handle a maximum of 3000watt/1500rms. This is a concern to me because I don't know whether those 3 car batteries will be feeding this amplifier/subwoofer enough power (or whatever you want to call it in the world of physics, amps?) in order to reach it's full potential. I don't want to limit my setup to perform under it's full capabilities, whether it be because of the car batteries, or whichever piece of equipment - it would suck.

Full specifications on the subwoofer and amplifier can be found here: Amplifier (Pioneer PRS-D5000SPL) and here: Subwoofer (Pioneer TS-W5000SPL)

Please give your constructive thoughts and suggestions/input, that is what I am looking for.

Thank you very much in advance,
Johnny

 

[Tweeker]

Stiffening capacitor(s) might be a good idea. Seen 1 Farad per 1,000 watts amp recommended by a few places (that sell them mind you). 20V+ rating is advisable. They would supply the peaks that your batteries couldnt.

I dont see why it wouldnt work.

A constant voltage/potential welder with 14VDC setting. It would laugh in your amps general direction.


Basic Car Audio Electronics article on stiffening capacitors.

 

[JohnnyJ]

I am confused.

I need some equipment that will result in 6.5volts [maximum, and preferably] at 560amps [maximum current draw] DC input, from a standard AC house electriciy outlet. I don't have a fortune to blow in terms of cash either, the cheapest solution that produce those output results is exactly what I'm after..I just need to know what that equipment IS and how it will function!

Please help me I am getting extremely frustrated...I've been working on this for hours per day for the last week-WITH NO SOLUTION!

All help VERY much appreciated, thanks.

 

[Tweeker]

Er why do you need 560 amps of 6.5V? Not sure what an ordinary household outlet is in Australia, but thats 3,640 watts. With an 85% efficient converter, which is pretty good, that would be ~4280 watts and probably more VA. It would pull 19+ amps at 230V.

If your using batteries and capacitors you dont need to supply peak power from the outlet and that helps alot. I assume average consumption isnt 3kW+?

Also, do you mean a supply of +/- 6.5V?

 

[zagisrule!]

Why bother getting a car head unit to power your home speakers? I would assume for price reasons? Because you would get much better audio and power output from a home receiver (assuming you were not going to amplify the speakers) than you would from a car head unit. But of course, you will pay for it probably $400 or so for a CD player and receiver. If you want to really do it on a budget (and still come out better than a car head unit) I would get a cheap DVD player and a decent receiver for a total of maybe $200. You should still be able to use pre-outs on the home receiver to send signal to your sub amp.

You will also encounter another issue when you get the sub and it's enclosure inside. The boxes and the subs themselves are usually designed for a constricted volume environment in which they must produce the maximum SPL (especially on SPL equipment ). I would be willing to bet that once you are inside the house with that equipment, you will find it not even as loud as a simple small powered sub costing a couple hundred bucks. I have heard of people getting around this fact by installing the sub under a bed or in a closet to simulate the limited volume of a car's usable acoustic enviroment. But if you do that, rattles, size constraints, and other issues will present themselves.

I am confused as to why you need a 6V supply, all the consumer car audio stuff I have worked with needs 10-16V. I would guess that you just forgot the "1" before your 6 in your post, and you want 16V at a couple hundred amps. This is easily doable in terms of a linear power supply with or without regulation (if you can supply enough AC). The simplest thing to do is aquire a large tranformer with secondaries that when rectified will produce your desired voltage. But there we run into problems. Most common (read relativly inexpensive) toroids are up to 1500VA or so, equating to roughly 100A usable at 15V. Because I know for a fact that with normal music (not just bass sines) and listening levels and a sub enclosure that is anywhere close to optimum, you will not be coming close to 500A like you said. Another issue you will encounter is that of rectifying the output of the toroid at 100A+. It will be fairly simple because of the low frequencies involved, but you will likely still need to parallel diodes. The most daunting of all issues is getting that amount of power from a "standard" outlet. The Sorensen supplies we are using at work (1750W units if I remeber correctly) require a 20A outlet to be safe, and they are incredibly efficient switching units. You would be asking for a fire or popped breaker to plug the supply I describe above into a "standard" 10A outlet.

In the end, a standalone battery and a dedicated charger are the only economical solution. However, I will say, that it is a terrible idea to take 3 different old batteries and parallel them, that is a more logical approach than designing and constructing a line-based supply. I would use only one battery in your shoes though...too much possibility of mismatch over time with this sort of thing.

Looking at the specs on the amp, it has a max current draw of 70A (note here on a different note that it is not possible to obtain 1100W of continuous output at 14V with that spec) then we can assume at 2 ohm load (your sub with parallel voice coils) then say a max current of 150A. You don't need 500A or more if all you are powering is your sub amp off 12V.

Hope this helps a bit.




-Matt

 

[Tweeker]

That was max current draw at 4ohm, his speaker is 2ohm.

 

[Eva]

That Pioneer gear is almost worthless, it's not worth the effort at all, and those power numbers are just car-audio ratings (ie: outrageous, not real).

If you want something really loud in your room, just buy some second hand PA gear (hey, it's not so crazy an idea, I enjoy a DIY three way all-horn-loaded system with a 10" midrange and a bass horn bigger than a washing machine in mine).

 

[Tweeker]

I think those rating are real, but bear in mind its spl comp gear, its only meant to run 30 seconds at a time, overheating is possible beyond that and they dont care a lick about distortion. Also fs is 32hz.

 

[Eva]

It's more like 3 seconds the time required to win an SPL contest, and blowing the entire equipmpent is allowed. It's a crazy world.

Even Cerwin Wegas and things like that are far overrated in comparison with products of other markets. I have two blown Stroker 12" here for reconing and their voice coils are similar to the ones you'll find in PA drivers rated at 400Wrms, altough these were rated at 1000Wrms. However, these voice coils didn't even had enough time to heat up and burn because the drivers are so badly designed and glued that the voice coil former broke and split from the cone and the inner spider because the materials and junctions were just not capable of whitstanding the required forces. I'm still trying to figure out how to glue the replacement cone, spider and voice coil set in a more reliable way (spiders and epoxy don't cope well).

 

[JohnnyJ]

No, it's voltage input is a maximum of 6.5v (it's a class D specifically for SPL designed amplifier). Unless I'm reading or interpreting the specifications wrong, I understand that the maximum voltage input is 6.5v. Some notes about some posts:

The amplifier can pump 1500RMS continuous @ 2Ohm, with a maximum of 3000watts. The sub gives out 2000rms continuous at 2Ohm, maximum 5000watts. I'm no audio EXPERT, but putting basic physics formulas into play with those amp readings, and the way that I interpret those specs, that's 70amps per 4Ohms, 70x4 = 280, times that by 2 for a 2Ohm reading and you get 560amps @ 2Ohm, which is the same reading I got from using various current calculators from sites such as bcae1.com. Unless that reading means 70amps AT 4Ohm (and not PER 4Ohm) that would mean that it would need 140amps at 2Ohm, plus you want some leverage seeing as it's minimum 80% efficient, so add an extra 20% onto that figure and you get 168amps. However I think that I was corrent in the frist instance - that it needs about 560amps at 6.5v to power it to it's full potential. I might be wrong, but I am PRETTY sure.

zagisrule! > Remember, I need that current at 6.5v DC.. not AC... Okay so = if I bought a battery charger that charge the batteries at 6V, and I bought a Sealed Lead Acid Dry Cell Valve Regulated Cyclic battery at 12V and 28Ah, will that mean that if I connect them in series that I will be getting 6V output seeing as I'm charging the battery at 6V? Also, I could buy 3 or more of them even so that it is more stable, but I'm not sure about how I would connect/wire all those up together to give 6V output. 28Ah means that it can supply 28amps for an hour, 56amps for 30mins, 112amps for 15mins... skip through to 560amps for 3 minutes. That's right is it not? So if I got 3 of those batteries (all brand new) and wired them up in parallel, being charged at 6volts... that should work pretty well. Except, how do I get the OUTPUT from those batteries to be 6v? Will the output be 6v seeing as they are being CHARGED at that voltage, or will they still give a 12v output?

Thanks so much in advance!! I'm getting closer to a solution.

 

[Perry Babin]

I think there is some confusion about the input voltage of 6.5v. That's the preamp level signal and it's simply the maximum that the amp can handle.

You need a 12-14 volt power supply.

If the amp can produce 2000 watts, you'll need ~185 amps of current at ~13.5 volts. If you use a battery with a charger, you won't be able to keep it at 13.5 volts. At lower voltage, you'll need even more current to reach full power. Remember that standard, liquid electrolyte batteries produce flammable/explosive gasses when being charged and should not be used indoors. 'Gel-cell' batteries are safer but expensive.

You really need to find a switching power supply for this. You can likely find some that were pulled from older mainframe computers. They are 5v each and you can wire them in series. I've purchased some that are capable of producing 125 amps continuously. There are some that can produce 200 amps. Keep in mind that this is not an inexpensive option but it will be safe and will do what you want to do. Please note that this cannot be done with ATX type power supplies because their grounds are tied to the AC mains ground.

Note: The sub doesn't 'give out' 2000 watts. It can handle/dissipate 2000 watts of power.

 

[Eva]

6.5V is the maximum input signal level, not the power supply voltage

ROFL!

 

[JohnnyJ]

Er why do you need 560 amps of 6.5V? Not sure what an ordinary household outlet is in Australia, but thats 3,640 watts. With an 85% efficient converter, which is pretty good, that would be ~4280 watts and probably more VA. It would pull 19+ amps at 230V.

If your using batteries and capacitors you dont need to supply peak power from the outlet and that helps alot. I assume average consumption isnt 3kW+?

Also, do you mean a supply of +/- 6.5V?

Yes that is correct, those specifications are actually UNDER RATED from it's actual performance, it produces just over 2000RMS continuously at 2Ohm when calculated technically - in the world of physics. That equals to SOMETHING like 3800watts max (can't remember the exact figure since it was about a week ago that I last calculated it).

I THINK I just realized something that I didn't know before, that this: Input Level Control Hi-Volt (200mV ~ 6.5v) means that it can handle at maximum 6.5V LESS or 6.5V MORE than it's TARGET (or most efficient) voltage. IS THAT RIGHT? Or can it not handle more than 6.5V input? It is a "PWM Regulated MOSFET Power Supply". As far as I understand that regulates the INCOMING voltage so that it reaches the "wanted" voltage when it gets to the part of the amplifier where it starts "amplifying" or whatever. If I grasped this correctly then this means I can use a 12v power supply?

As I am typing this I am reading 2 replies to me previous post, and realized that what I was just busy typing is correct. Man I feel somewhat better now! Much better in fact.

OKAY, so I can just use 3 of those batteries then, which will provide enough juice(in watts, voltage and current) to power this amplifier to it's full potential?

 

[Perry Babin]

The RMS continuous power ratings are the only useful power ratings. Virtually anything that states power as 'maximum' power can be dismissed as garbage.

The 6.5 volts is the signal from the head unit and has nothing to do with power supply voltage. Depending on the gain setting, the amplifier can be pushed to full power with 200mv (0.2 v) or 6.5v.

The PWM regulation regulates rail voltage inside the amplifier. It allows the amplifier to have the same rail voltage regardless of the battery voltage (within reason).

 

[JohnnyJ]

Okay.. so can I use 15v input? I am asking because I am thinking of buying 3 ATX PSU's and running them at 5V each. About your comment earlier about not being able to use ATX PSU's for this use, you actually can. All you have to do is connect the green wire (power on) to any black wire (ground). You can just cut them and permanently wire them together. Once they are shorted the power supply runs at all times. Which means you can shut them ON/OFF by the wall switch. You may have known this and not suggested it because that's not it's INTENDED use, but if you didn't then there it is

ALSO: Can I use 10V input? Or does it have to be over 12V?

Thanks for your help so far mate, helping me lots.

 

[Perry Babin]

You cannot use ATX supplies in series because each ground is connected to the mains earth ground. If you connect them in series, you will be shorting the output to ground. You cannot lift the grounds for reasons of safety.

If you could find some of the switching supplies I described, you would adjust them to something near 13.8 volts. Each supply would be set to ~4.6 volts.

You may be able to run that amp at 15 volts. Some amps have high voltage shutdown and 15 volts would be near the set-point for some amps to shut down.

I doubt that the amp would run at 10 volts. Many amps require at least 10.5 volts.

 

[JohnnyJ]

Alright, well I don't know where to get NON-ATX PSUs from so I haven't got anything to work with. Where can I buy NEW and decent PSUs from that will supply me with the appropraite current/voltage/watts I need?

 

[JohnnyJ]

What are the PSUs called that you are talking about? Are they called "AT"?

 

[zagisrule!]

I suggest you might re-read my original post.

I described a DC power supply (not AC - rectification means we are changing AC to DC).

Tweaker you will also notice if you read the bottom of my first post I DID post estimated current draw for a 2-ohm load at 150A.

What is this about running 5V PSU's in series? If you are going to pay for three supplies of that current rating, might as well just buy a real 12V supply. The normal PC powersupplies are good for 10-20A at 5V, nowhere near your "560A" you claim to need. You calculations for the figure are incorrect...there is no need to multiply the number by 4 for the current with 4 ohms...70A into 4 ohms, and double that for a rough estimate at 2 ohms...150A is overkill but that is fine.

The other thing I don't think you will realize is that this power needs to come from somewhere! It is not safe to just plug a 1.5kW supply into the wall and expect everything to be fine and dandy.

Parallelling many batteries is not safe, because as time goes on, one of them will weaken and they will all fail and you will be left with nothing.

You might try reading the manual to understand current and supply requirments.



-Matt

 

[JohnnyJ]

zagisrule! > I confused the voltage input of my amplifier with another rating, that is why I thought I needed a 6.5vdc supply. I got that cleared up and I am now just looking for a normal power supply to power an amp like a car battery would, between 12-14V. That's why I 'claimed' I needed that sort of current.

I'm not an audio expert - I stress that point AGAIN. Ok, a Switch Mode 12VDC power supply that can supply me with 300amps continuous, where on earth do I find that and how much would that cost me?

Thanks again!!