Power supply for sound system

[deviator]

Hello everyone, I'm not even sure if this is where i can ask.

The problem that I'm currently facing is that i have totally no idea what kind of power supply i require to fully support 50w sound system 4.1 subwoofer is 30w and 4 x 5w. The thing is i want to pack everything up on my back, that's why i need it to be portable and rechargeable. I currently have 1 battery of notebook - HP pavillion dv5000 series, which has 90w (not sure how much amp atm).

-Would it meet my expectations? if so approximately how long would it last (20 mins or 1 day or so..)
-If not, what kind of power supply I would require (w and amp).
-Or overall, an example of what I'm looking for would be greatly appreciated also.

Thanks in advance for your support.

 

[audioguru]

Maybe your amplifier and speakers produce 50 real Watts at clipping instead of 50 Whats which is only about 5 real Watts.
Then the type of music you listen to determines the average power.
Acid rock is continuous full blast square-waves which uses a lot of power all the time.
Pop music has an average power of 1/10th the max power.
Classical music has an average power of 1/20th the max power.

You say that the battery is 90W but you do not say its capacity (how long it can produce 90W).
Rechargeable batteries are rated in mAh or Ah which tell you how long they can produce a certain amount of current.

 

[deviator]

this is the one i have:
https://www.level8technology.com/hp-hstnn-db31-battery-hp-hstnn-db31-laptop-battery-1167
(giving you a link cause i don't understand about that kind of things) :/

 

[audioguru]

The battery can supply 10.8V at 4.4A for one hour which is 48Whr, not 90Whr.
I have never seen an amplifier that has an output power as high as 30W with a supply voltage as low as 10.8V. A bridged car radio amplifier will have an output power of only 8.6W into a 4 ohm speaker at clipping when its supply voltage is only 10.8V.

You must determine the impedance of your speakers and amplifier circuits for them. The power required from the amplifier circuits will determine the voltage (from the battery) required to power them.

 

[deviator]

The battery can supply 10.8V at 4.4A for one hour which is 48Whr, not 90Whr.
I have never seen an amplifier that has an output power as high as 30W with a supply voltage as low as 10.8V. A bridged car radio amplifier will have an output power of only 8.6W into a 4 ohm speaker at clipping when its supply voltage is only 10.8V.

You must determine the impedance of your speakers and amplifier circuits for them. The power required from the amplifier circuits will determine the voltage (from the battery) required to power them.

the shitty thing is i have no idea what you're saying (probably cause i used to sleep during physics lessons..) maybe you could give me an actual example of the battery i would require and what with it? like a link of a product, would appreciate it a lot

 

[audioguru]

Most home speakers are 8 ohms and car speakers are 4 ohms.
An ordinary amplifier needs a supply voltage of 48V to provide 30W into an 8 ohm speaker or needs a supply voltage of 35V to provide 30W into a 4 ohm speaker.

Two amplifiers can be "bridged together" and drive both ends of a speaker. Most ordinary car radio amplifier ICs are bridged. For 30W into 8 ohms a bridged amplifier needs a supply voltage of 24V or for a 4 ohm speaker a supply voltage of 17.5V.

If you use two of those expensive batteries in series to make 21.6V then a bridged amplifier will produce 22.8W into 8 ohms or 42W into 4 ohms.

I am talking about real Watts. Amplifiers are rated in Whats which are outright lies. A little computer speaker is rated at 1000W which is realy only 2W.
A four-channels car radio is rated at 220W (55W per channel) but actually produces only 14W per channel.

Why do you want to carry around a surround-sound system?

35 years ago I made a sound system for the beach. I used 3" left and right satellite speakers and a 4" woofer. I made the amplifiers from ICs. The woofer had a power of 5W and each satellite speaker had a power of 3W. The power was supplied by six AA Ni-cad battery cells. It was louder and sounded much better than "ghetto blasters". I am using one amplifier and the satellite speakers today for my little TV.

 

[deviator]

Most home speakers are 8 ohms and car speakers are 4 ohms.
An ordinary amplifier needs a supply voltage of 48V to provide 30W into an 8 ohm speaker or needs a supply voltage of 35V to provide 30W into a 4 ohm speaker.

Two amplifiers can be "bridged together" and drive both ends of a speaker. Most ordinary car radio amplifier ICs are bridged. For 30W into 8 ohms a bridged amplifier needs a supply voltage of 24V or for a 4 ohm speaker a supply voltage of 17.5V.

If you use two of those expensive batteries in series to make 21.6V then a bridged amplifier will produce 22.8W into 8 ohms or 42W into 4 ohms.

I am talking about real Watts. Amplifiers are rated in Whats which are outright lies. A little computer speaker is rated at 1000W which is realy only 2W.
A four-channels car radio is rated at 220W (55W per channel) but actually produces only 14W per channel.

Why do you want to carry around a surround-sound system?

35 years ago I made a sound system for the beach. I used 3" left and right satellite speakers and a 4" woofer. I made the amplifiers from ICs. The woofer had a power of 5W and each satellite speaker had a power of 3W. The power was supplied by six AA Ni-cad battery cells. It was louder and sounded much better than "ghetto blasters". I am using one amplifier and the satellite speakers today for my little TV.

Then any ideas what i could do with those speakers of mine? i want them more or less portable to use outside.
(so my speakers actual watts are around 5 (if i understood correctly), and i need some sort of amplifiers to power them?)

 

[audioguru]

I don't know if you have good quality speakers that are properly rated in real Watts or cheap junk speakers that are rated in lies.
I don't know if the speakers are in properly designed enclosures.
I don't know if the speakers have built-in amplifiers.
I don't think you know these things either.

As a start you can post the datasheets for the speakers or the manufacturer's name and the speaker part numbers.

 

[deviator]

I don't know if you have good quality speakers that are properly rated in real Watts or cheap junk speakers that are rated in lies.
I don't know if the speakers are in properly designed enclosures.
I don't know if the speakers have built-in amplifiers.
I don't think you know these things either.

As a start you can post the datasheets for the speakers or the manufacturer's name and the speaker part numbers.

hehe, let's see...

I'll write down whatever i see cause it's very old and manufacturer is either unknown or "Edtasonic"
Ac 230v 50HZ
Driver: 5.25" Woofer 2.5" Fullrange
Input impedance: 8kΩ
Woofer frequency presponse: 30Hz~150Hz
Satellite frequency response: 150Hz~20KHz
T.H.D.AT 50Hz(1w Output): Woofer-<0.05%
T.H.D.AT 1KHz(1w output): Satelite-<0.1%
RMS. Output: Woofer-30w Satelite-5w per channel

(nothing else imporant is written on it.)

 

[unclejed613]

looks like typical computer speakers to me.... those THD figures are probably lies...... what you have here is a "system" that is probably 10 to 15 watts total, with 5 watt speakers, and the subwoofer driver might be rated at 10 watts. the power supply is most likely 12V DC, as that's common for computer speakers. you could probably get away with disconnecting the power transformer and connecting the battery in place of it. if you want to see how some of these manufacturers come up with their fictional power ratings, there's an article here: **broken link removed**

 

[audioguru]

The speakers have amplifiers and an AC power supply. We don't know the output voltage of the power supply for a battery to replace it.
The power is rated in RMS Watts which are real Watts but the distortion is shown only at an output of 1W. The distortion is supposed to be shown at the rated output power.

Maybe you can power it from a motorcycle battery and an inverter.

 

[deviator]

looks like typical computer speakers to me.... those THD figures are probably lies...... what you have here is a "system" that is probably 10 to 15 watts total, with 5 watt speakers, and the subwoofer driver might be rated at 10 watts. the power supply is most likely 12V DC, as that's common for computer speakers. you could probably get away with disconnecting the power transformer and connecting the battery in place of it. if you want to see how some of these manufacturers come up with their fictional power ratings, there's an article here: **broken link removed**

i take it, that the power transformer is somewhere inside that box near the wire and i need to get rid of it, and then somehow connect a battery holder there right? (how much and what kind of batteries would work?)

 

[audioguru]

You don't know the voltages produced by the power supply for the speaker amplifiers so you cannot select a suitable battery voltage. the power supply probably produces a few voltages since the amplifiers have different power ratings and the power supply might produce positive and negative voltages.

 

[deviator]

You don't know the voltages produced by the power supply for the speaker amplifiers so you cannot select a suitable battery voltage. the power supply probably produces a few voltages since the amplifiers have different power ratings and the power supply might produce positive and negative voltages.

well if i would open that thing up, wouldn't i find some info on the parts inside?

 

[deviator]

this is what I found... and i take it that the object on the right hand is the main problem...

and this stuff is written on it:
I/P 230V 50Hz
O/P 12Vx2 3.5A
Thermal Fuse 130 degrees (Celcius)

 

[audioguru]

Your camera is hopeless for taking clear closup pictures.

The transformer has two 12VAC outputs. Its max allowed current is 3.5A so its power rating is 24V x 3.5A= 84W.

It might make 16VDC or 32VDC or both. If it makes 16VDC then an ordinary amplifier will produce 5W into 4 ohms so maybe the 5W amplifiers use a supply of 16VDC and use 4 ohm speakers.
If the sub-woofer speaker is 3 ohms and the amplifier uses the 32V supply then its output power is 30W.

With the system blasting its full output power of 50W then the amplifiers produce 34W of heat and the transformer is not overloaded.

32V worth of batteries will cost you an arm and a leg or three legs.

 

[deviator]

Your camera is hopeless for taking clear closup pictures.

The transformer has two 12VAC outputs. Its max allowed current is 3.5A so its power rating is 24V x 3.5A= 84W.

It might make 16VDC or 32VDC or both. If it makes 16VDC then an ordinary amplifier will produce 5W into 4 ohms so maybe the 5W amplifiers use a supply of 16VDC and use 4 ohm speakers.
If the sub-woofer speaker is 3 ohms and the amplifier uses the 32V supply then its output power is 30W.

With the system blasting its full output power of 50W then the amplifiers produce 34W of heat and the transformer is not overloaded.

32V worth of batteries will cost you an arm and a leg or three legs.

how about a rechargeable accumulator or something?

P.S it's my phone camera without a blitz of 3,2 mPix

 

[audioguru]

An accumulator is a rechargeable battery in some languages.
A Ni-MH cell is 1.25V so you would need 26 of them.
A Lithium cell is 3.6V or 3.7V so you woulfd need 9 of them.

Then you need to calculate how much current the battery must supply which determines the size of the battery cells.

 

[unclejed613]

so the voltages you need to supply to the amplifier are +/-16V. it will probably still work ok on +/-12V, but with less power. with +/-16V you get about 15W into 8 ohms, with +/-12V, you will get 9W into 8 ohms. that's a difference of about 2db.

 

[audioguru]

so the voltages you need to supply to the amplifier are +/-16V. it will probably still work ok on +/-12V, but with less power. with +/-16V you get about 15W into 8 ohms, with +/-12V, you will get 9W into 8 ohms. that's a difference of about 2db.

No.
The emitter-follower output transistors or darlington transistors at the output of an audio amp have a voltage loss. With a 32V supply the output to a speaker will be about 28V p-p so the power into 8 ohms is only 12.3W.
With a 24V supply the output to a speaker will be 20V p-p so the power into 8 ohms is only 6.3W. The difference is noticeable and is about 3dB.