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Old 9th May 2006, 11:08 PM   #1
sigfrid is offline sigfrid  England
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Default question about coaxial speakers and amplifier

hello all....

i have a car sony head unit with 45*4 w speaker output that i use at home, i use with it 2 coaxial speakers with 280w max.music power each, and the power supply is a regulated 12vdc 3A adapter
the problem is when i get the volume up to some point the head unit turns off
i wanna ask how much the sound quality is affected due to the difference in wattage between speakers and hu output, and if i use an amplifier will it imporove sound quality and make me able to turn the volume up without the HU turning off, and if so how much amperege should the DC adaptor should have.


any advice please...
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Old 9th May 2006, 11:40 PM   #2
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Couple of things

first, the headunit doesn't do 45x4, it does more like 18x4
second, the speakers can't take 280w each, it's probably more like 40-50w

Going to a higher power source would improve sound quality, but only if you're pushing your current source (the headunit) close to its limits. The easiest way to test that would be to use some tones to see at what volume it clips, and if you're exceeding that volume when listening to music you should look into an amp.

Right now, you need a power supply that can actually supply the required power though, 3 amps is virtually nothing when you're trying to power an audio amplifier in the 12v world. That amp is capable of putting out almost 80 watts, it's probably around 50% efficient at the highest, which means to put out that 80 watts it would need to draw around 160 watts, and the rest of the components need to draw power too, so say 200 watts in total. So you have a device that requires upwards of 200 watts at full output, and you're feeding it 36 watts. That's what's causing the headunit to shut off, the power supply is crapping out and dropping the voltage too low. You need something that can put out at least 10-15 amps to run that headunit, even more if you plan on getting an external amp.
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Old 10th May 2006, 10:26 PM   #3
sigfrid is offline sigfrid  England
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hi

many thanks for the useful information, but if i'm going to use an amplifier what power should it be to run those speakers.
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Old 10th May 2006, 11:57 PM   #4
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You don't need much power to run some coaxs in a home, 40-50x4 should be more than enough. Get a new power supply first though, you might not need another amp at all.
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Old 11th May 2006, 12:44 PM   #5
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Sigfrid,

As sr20dem0n said, you need a more powerful power supply.
You could check the fuse rating of your head unit.
The power supply should be atleast that much.

If you add instead another amp, it should be mains powered or else you would end up using another power supply sufficient enough for this amplifier(if this one is a car amp).
This would be much more expensive than upgrading the power supply for the head unit.

Regards,
Francis
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Old 13th May 2006, 01:03 AM   #6
sigfrid is offline sigfrid  England
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hi again

the head unit fuse is rated at 10 ampere, so i will be going with may be 15 amp power source, i wanna ask will i be noticing any differnce in sound quality with that change or i am just gonna be able to raise the volume up with out the hu being shut off only
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Old 13th May 2006, 02:20 AM   #7
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3A is plenty of power...

...if you put a car battery between the charger and the amp. Nobody can listen at max volume for the time it would take to draw that battery down to ~11.5V. Cheap and easy.
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Old 14th May 2006, 04:40 AM   #8
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Quote:
...if you put a car battery between the charger and the amp. Nobody can listen at max volume for the time it would take to draw that battery down to ~11.5V. Cheap and easy.
Good suggestion, but he'd also need a battery charger for this battery.
A commercial charger(eg. I have one of 9 amps) itself may be enough(without using any battery) if he doesn't listen at high volumes.
So battery+charger would be costlier than upgraded power supply. Don't know U.S prices, but in my part of the world it is.

Sigfrid,
You won't notice any difference in sound quality, only you'll be able to play it louder.
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Old 14th May 2006, 06:11 AM   #9
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Quote:
Originally posted by chipco3434
3A is plenty of power...

...if you put a car battery between the charger and the amp. Nobody can listen at max volume for the time it would take to draw that battery down to ~11.5V. Cheap and easy.

But a 12v supply can't charge a battery, it has to be at least 13v, preferably 14v or a little higher.
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Old 16th May 2006, 09:10 PM   #10
sigfrid is offline sigfrid  England
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hi again

i asked some one that is supposed to have some experience in this stuff and he said that i can get an old car battery and connect to the head unit and the 12vdc 3A adaptor.....when i asked him how i charge it (the battery), he said the adaptor will do the job....

any body have an idea should i try it or he is just dos'nt know what he is saying.
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