audiophiles... EE's some ideas?

[magley64]

Even at that, you would have to have a HUGE battery bank to be able to play for 1+hrs.

so the 950 watt computer power supply wouldn't provide enough power to drive the amp?

I'm just confused where the batteries come into play.

I had also considered a "battery solution" using a decent car battery and a gold series alternator hooked to a 120v electric motor, large and industrious, but effective if I did my calculations correctly.

i figured a computer power supply would eliminate those components (battery, charging system, capacitor, etc)

Edited October 24, 2010 by magley64

[rawlins87]

I'm not very familiar with computer power supplies.

Is it a constant 950 Watts or variable upon consumption?

[magley64]

I'm not very familiar with computer power supplies.

Is it a constant 950 Watts or variable upon consumption?

I don't know, this is part of the reason I directed this to EEs. (figuring they had expeience with them/knowledge of them)

This was one of the pitfalls I was fearing.

[TSB67]

I'm no EE but I don't see how a computer power supply with "pin" outputs is going to push something that you hook up to your car with 4ga wire.

[magley64]

I'm no EE but I don't see how a computer power supply with "pin" outputs is going to push something that you hook up to your car with 4ga wire.

it's all about wattage.

and most of the people I've talked to agree that 4ga wire is severe overkill on a 600 watt amp.

Edited October 24, 2010 by magley64

[rawlins87]

4 gauge is good to 1000rms.

There is no such thing as over kill in wire.

I've ran a 300 Watt amp off of 1 ought.

[magley64]

4 gauge is good to 1000rms.

There is no such thing as over kill in wire.

I've ran a 300 Watt amp off of 1 ought.

That's your perogative, I've just always preferred to run much smaller cables on my installs, and have had no problems doing so.

[TSB67]

4ga wire is severe overkill on a 600 watt amp.

True, sorry, I was thinking of something bigger.

[alienpi]

Have any of you tried Nordist Blue Heaven speaker cables? I couldn't believe the difference in sound! Also has any1 tried Audioquest speaker cables, I love the interconnects? One of these days i'd like to borrow a set to see how they sound.

[jporter12]

That's your perogative, I've just always preferred to run much smaller cables on my installs, and have had no problems doing so.

In a car audio environment, the power wire should be oversized if anything, due to the fact that the wire is usually ran under carpet, seats, etc. Smaller wire WILL heat up under high current loads, thus being a safety concern. My current system is around 500 watts with 8 ga. wire. I would be more comfortable with 4 ga. but it is more of the family ride, and the system doesn't get loud very often, therefore, the actual current draw is low, 90% of the time. It's very rare that the thing get played at over 50%.

[magley64]

Smaller wire WILL heat up under high current loads, thus being a safety concern.

Smaller wire MAY heat up under high current loads, thus being a safety concern.

FIFY, I've seen several installs done with quite small (but high quality) primary wire, and have no issues whatsoever with wires heating up.

[jporter12]

Smaller wire MAY heat up under high current loads, thus being a safety concern.

FIFY, I've seen several installs done with quite small (but high quality) primary wire, and have no issues whatsoever with wires heating up.

No, you didn't fix a thing. Wire that is too small WILL heat up. Where the MAY heat up comes in is with how much too small the wire is. Try running a 500 watt amp with 18ga speaker wire for the power input. This is 12v stuff that I'm talking about. 12ga wire for the same amp will probably be ok, but still should have 8ga, at least.

Also, fine stranded wire is better, because the electons supposedly travel on the outside of the strand, and finer stands give more room for them to flow.

This is all theory, I use the recommended wire, since I'm not a EE.

[Strictly Street]

Without getting too technical here I would like to point out a couple of things.

All watts are not created equally. Most car amp mfg's lie about their ratings.

A little simple math proves this watts(P)=volts(E) x amps(I)

A 1000 watt car amp would draw 83.33333 amps at 12 volts.

How long did you say you could use that and still start the car/not have a fire?

There are peak watts, peak to peak watts, RMS watts, RMS continuous -1 channel driven -both channels driven, continuous sine, peak music power watts just to name a few.

The exact same amp might have ratings from 10 to 1400 watts by using nothing more than a calculator.

Now lets add to the mix that music is not a continuous waveform with a continuous power factor. Then we add that there are peak demands, (usually called headroom on an amp) that all go into the mix of what is a watt?

Bottom line is don't get to hung up on how many watts a thing is, it doesn't matter in any real sense of the word as it doesn't have any real definition.

Lets instead look at it backwards. How big is the garage you wish to fill with music?

Even a cheesy old home stereo Fisher 100 watt amp from the 90's will rock out your average garage and you can find them at garage sales for $20.00. Keep in mind a 100 watt amp is really two 50 watt amps, right and left. Again you are being lied too. 400 watt quad amp, um no. 4 100 watt amps or worse.

Speakers are usually about 8 ohms and also rated in watts as well. See above for what is a watt. Realize you are again being lied to. There is no way on Gods green earth those old speakers you have can really handle 1000 watts even if it says so on the back. Speakers that can handle 1000 watts are found at concerts, not your garage.

After a second look at your sharp speakers in the picture if they can handle more than 35watts I'd be surprised. To run all 4 speakers you can wire them in series which will increase the power handling and go easier on your amp. Just go from the + of the amp to the + of the first speaker and then from the - of that speaker to the plus of the next one and then the - of that to the - on the amp

Remember 8 ohms in parallel with 8 ohms is 4 ohms. By cutting the resistance by half you double the current. Which will overload most amps and let the smoke out. (Why your old amp kicked it)

8 ohms in series with 8 ohms is 16 ohms wich cuts your amps in half saving the smoke inside your amp for another day.

Now back to your original question,

Q: Can you use a PC power supply to run car stereo equipment.

A: Yes!

Why you would want to eludes me. Something about having to make a bunch of custom cables just to connect everything together comes to mind.

But an old CB radio power converter 120 to 12 to run a car stereo FM/CD/Cassette/8-Track with the line out RCA jacks hooked to an old Fisher amp running a couple of old house speakers does sound like a rocking garage.

Edited October 24, 2010 by Strictly Street

[magley64]

Ss, thank you for the tech support so far.

The size of the garage not withstanding, I want enough clean power to drive my large speakers near their limits without destroying anything. The old sharp amplifier claimed 300 watts, and was designed to drive 2 of them near their limits.

[jporter12]

Ss, thank you for the tech support so far.

The size of the garage not withstanding, I want enough clean power to drive my large speakers near their limits without destroying anything. The old sharp amplifier claimed 300 watts, and was designed to drive 2 of them near their limits.

My opinion, a couple decent quality stereo receivers, one to each pair of speakers, and all will be good. Should be pretty cheap. Best Buy has a Sony for $155 that woudl do well, although it's only 200w.

[magley64]

Why you would want to eludes me. Something about having to make a bunch of custom cables just to connect everything together comes to mind.quote]

yes, you are partially correct, this was originally an effort in macgyvering.

[jporter12]

Without getting too technical here I would like to point out a couple of things.

All watts are not created equally. Most car amp mfg's lie about their ratings.

A little simple math proves this watts(P)=volts(E) x amps(I)

A 1000 watt car amp would draw 83.33333 amps at 12 volts.

How long did you say you could use that and still start the car/not have a fire?

There are peak watts, peak to peak watts, RMS watts, RMS continuous -1 channel driven -both channels driven, continuous sine, peak music power watts just to name a few.

The exact same amp might have ratings from 10 to 1400 watts by using nothing more than a calculator.

Now lets add to the mix that music is not a continuous waveform with a continuous power factor. Then we add that there are peak demands, (usually called headroom on an amp) that all go into the mix of what is a watt?

Bottom line is don't get to hung up on how many watts a thing is, it doesn't matter in any real sense of the word as it doesn't have any real definition.

Oh, I totally agree that a watt is not the end-alll comparison factor on how loud a system will be. The big amp in the system I was talking about was tested (by the manufacturer of course) at 748 watts. That's on a bench, with a resistor, not a speaker, from what I understand. The others were around 200-ish each. Then you have to add in the efficiency of the amp. The big amp was a class d (subwoofer) which is very efficient, not worth a damn with higher frequencies. The others were class AB which are around 60% efficient, IIRC. So, at 12.6 volts, we're probably getting close to 100+ amps going in. I have heard systems that are far lower wattage that are louder.

Where the big amounts of power reall comes into play, is in control of the speaker cone of the woofers, more critical in some cabinet designs than others.

[jporter12]

Why you would want to eludes me. Something about having to make a bunch of custom cables just to connect everything together comes to mind.

yes, you are partially correct, this was originally an effort in macgyvering.

This does not surprise me at all!

[alienpi]

Bottom line is don't get to hung up on how many watts a thing is, it doesn't matter in any real sense of the word as it doesn't have any real definition.

I had a cheap 100 watt per channel receiver in college that sounded like crap once the volume got turned up with efficient speakers. This article kind of explained why.

Full-Disclosure-Power

[magley64]

After a second look at your sharp speakers in the picture if they can handle more than 35watts I'd be surprised.

you may be right, but here is a better shot of the sharp 15's, and what they have to say for themselves.

and here are the 12's

here is the amp I fried.

this stuff is all from like 86 - 87 i think, so I'm not sure how much they lied about their power back then.

Edited October 24, 2010 by magley64

[jporter12]

^^^ That backs up what I said about a couple 200 watt receivers! 100 watts per channel. Best buy also had their house brand, Insignia, for about $99 each, at about 100 watts per channel. No idea who makes them, but I'm sure it's someone that makes stuff for others. The TV I bought thereabout 5 or 6 years ago I found out is manufactured by Sansui. I had no idea they were still even around, until that!

[magley64]

I'm pretty much settled on a crown rack amp per rawlins suggestion, this will allow me to add a 31 band peavy EQ to the equation as well.

this way I can build a small rack mount in back, and be able to add stuff later as I go along.

[jporter12]

I'm pretty much settled on a crown rack amp per rawlins suggestion, this will allow me to add a 31 band peavy EQ to the equation as well.

this way I can build a small rack mount in back, and be able to add stuff later as I go along.

Great idea! Next thing we know, you'll be getting some professional speakers, a mixer, some lights, etc...

[rawlins87]

Oh, I totally agree that a watt is not the end-alll comparison factor on how loud a system will be. The big amp in the system I was talking about was tested (by the manufacturer of course) at 748 watts. That's on a bench, with a resistor, not a speaker, from what I understand. The others were around 200-ish each. Then you have to add in the efficiency of the amp. The big amp was a class d (subwoofer) which is very efficient, not worth a damn with higher frequencies. The others were class AB which are around 60% efficient, IIRC. So, at 12.6 volts, we're probably getting close to 100+ amps going in. I have heard systems that are far lower wattage that are louder.

Where the big amounts of power reall comes into play, is in control of the speaker cone of the woofers, more critical in some cabinet designs than others.

Bench testing amps with a certain load resistor is just a way of the manufacture saying in perfect conditions this is what it will make.

Testing with a reative load is better.

Because in real world use your 4ohm speaker is never. You will have impedance rise. At different frequencies there will be a different amount. You speaker could be 4ohms at 30hz but then be 16ohms at 40hz.

As far as cone control yes the enclosure will have the majority of an effect, but comparing qms and qts should give you a feel for it ahead of time.

A subwoofer with low qts will have better cone control because of the re/bl^2 (motor force).

Qms or the mechanical Q of the driver also has effect. Higher the qms the better mechanical damping. Now This is with the suspensions, surround and spiders.

Then factor mms and cms and there's a whole lot more variables.

Edited October 25, 2010 by rawlins87

[magley64]

Great idea! Next thing we know, you'll be getting some professional speakers, a mixer, some lights, etc...

I wouldn't put it past me. I like stereos and motorcycles. I'm planning on having a KICKING stereo when I get a house.

Also, don't pass judgement on the cp-7700 speakers until you hear them, this stereo cost in excess of $1000 when new, this wasn't some cheap little home system. Should definitely be up and running for Magzfest '11

I decked out my old pontiac with mobile audio. Had 2 kicker solox 18s, 2 L7 15s, 2 pioneer 10s, and 12s respectively, had 2 high power alternators to drive the 5 amps in my back seat. Was so loud that I didn't even notice that my fuel tank had fallen out until 3 miles later when the carb bowls emptied.

Edited October 25, 2010 by magley64