# Can 30 Watts (RMS) Speaker Work with 5V 2A Power Supply?

by El_Dorado   Last Updated April 15, 2019 10:25 AM

I am thinking of using a speaker with Raspberry Pi 3b+ which has a 5V output pin.

Speaker data:

• Power rating (RMS) 30 Watts

• Power rating (max) 60 Watts

• Impedance8 ohms

Will this speaker will work with 5V and 2A?

Tags :

From the way youve written your question im assuming youre trying to hook the speaker up to one of the Pis GPIO pins and the 5V 2A supply is whats powering the PI. The answer to that is no, youll fry the pi. The amount of power available out of the GPIO pins is not the same as the power supply going into the pi. The max output current of a pi 3 gpio pin is approx 16mA. As your speaker is 8 ohm it will try to draw 412mA.

You will require an amplifier to meet the power demands of a speaker. For 8 ohm at 5V then the power output will be v^2 / R = 25 / 8 = 3.125W So the speaker will work but it will be quieter

Andy West
April 15, 2019 10:04 AM

Will this speaker will work with 5V and 2A?

Yes, but the maximum average output power will be less than 30 watts; a 5 volt supply capable of delivering a maximum of 2 amps can only produce 10 watts and, given that your amplifier will have an efficiency around 60%, the maximum power delivered from the 5 volt supply will be about 6 watts.

But it's slightly worse than this if you use a conventional linear amplifier because it can only produce maybe 4 volts peak-to-peak and that, as a sinewave, has an RMS value of 1.414 volts. That RMS voltage across an 8 ohm speaker produces a power of only 0.25 watts.

If you used a bridge amplifier you could achieve maybe 8 volts p-p and that would deliver a sinewave power of 1 watt.

Andy aka
April 15, 2019 10:07 AM

1. The Raspberry Pi outputs are 5V, but nowhere near 2A. More like some tens of milliamperes.

2. 5V at 2A is only 10 watts, so it would be safe to operate that speaker from an amplifier operated from 5V.

3. 5V into 8 ohms can only push 0.6 A through the speaker, so you can only get like three watts RMS into an 8 ohm speaker from an amplifier operating on 5V.

If you want to make full use of the speaker's rated power then you will need an amplifier capable of providing that power.

The Raspberry Pi can't provide that power. A typical Raspberry Pi has a 5V powersupply rated for 2A. That's only 10 watts so it's nowhere near the rated power - and you can't even get that because the voltage is too low for the speaker impedance.

30 watts RMS is ********* loud.

Had to work on a bunch of radios once. Speakers were rated for 12W RMS, and the amplifiers could provide it.

Some jerk set the (push button controlled) volume all the way up to maximum before disconnecting the things and sending them to the company I worked for.

The only way to turn down the volume was to power up the radio and use the push buttons.

Problem was, the darned things played this 5 second long "Gong" sound at power on.

The first one I ran into like that near blew my ear drums out. It rattled the windows, and made people in other companies in the building come over and ask what happened.

I cursed over the second one.

At the third one, I cursed the technician who had removed the radios from the police cars because it was obvious he had cranked up the volume on them on purpose.

Thereafter, power up of each radio consisted of placing the speaker face down in the cushions of my chair, me sitting on it, turning on the radio, and waiting for the gong to end.

The equipment belonged to the customer. I couldn't modify the cable set to disconnect the speaker, and you had to have the whole cable set to get the radios powered up to the point you could turn down the volume.

My buns were numb from the vibrations before I got all the radios powered on and checked (and the volume turned down.)

And, that was only 12W RMS. Not 30W like you want to use.

JRE
April 15, 2019 10:17 AM

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