Cordless Speakers

[Wes]

Suppose I have a 13 kJ Li battery (like a car battery) - How long could I run a HiFi or near hiFi (restricted LF) active speaker that uses Class D amps, and WiFi to receive the music feed, plus a DAC?

Anybody know?

 

[pjug]

Aren't car batteries MJs of energy, 100s of Watt hours? e.g. 50AH*12V = 600WH

If you convert energy units of whatever battery you are thinking to WH, then you might get a rough idea of what is possibly by comparing tp the Sonos Move. That gets roughy 10 hrs continuous playing from a 36WH battery.

 

[Katji]

hmm...I could introduce you to someone who got into it extensively, over about 2 years or so. But with various chip amp boards, DAC, passive speakers. (Hi-fi speakers, definitely.) ...Or at least find his main thread. I'm not sure about the wi-fi though...i think he uses iPhone. Or otherwise laptop.
The usual re the amp power supply...5V? 9V to 12V...iirc, he eventually settled on one that was good enough on 5V - better than others.

 

[Wes]

I'm interested in how long you could run on 13 kJ (convert to W-hr if you want, it is all energy).

Let's just look at the amp - what would the current draw be - roughly?

 

[Ron Texas]

I'm interested in how long you could run on 13 kJ (convert to W-hr if you want, it is all energy).

Let's just look at the amp - what would the current draw be - roughly?

Something to convert it to 110 or 220 AC is needed which eats up a lot of power and is probably noisy.

 

[Wes]

no conversion is needed

 

[pjug]

I'm interested in how long you could run on 13 kJ (convert to W-hr if you want, it is all energy).

Let's just look at the amp - what would the current draw be - roughly?

Going back to the Sonos Move as reference, they specify idle power at about 3W. So that would be the amp with the wireless. I think they use 18V battery and most likely a bridged Class D so they can possibly get close to 40W into 4 ohms. I guess running on higher voltage would generally mean a bit more idle power but maybe not much, and of course it depends on what amplifier.

So you are looking at a handful of watts idle power using a low idle power Class D amp and wireless. Playing at low volume won't add much to that (and so they say 11 hours with a 36WH battery, which corresponds to drawing not much more than the 3W idle power). Of course playing louder consumes more power.

Where is the 13KJ number coming from? That's not a very big battery unless I am doing something wrong in my conversions.
[edit: a 9V alkaline battery stores about 19KJ, 6 AA batteries store about 89KJ https://www.baldengineer.com/9v-battery-energy-density.html]

 

[Ron Texas]

no conversion is needed

Explain please.

 

[Wes]

a DC amp or several can be used as with car amps


https://en.wikipedia.org/wiki/Automotive_battery#Amp_hours_(Ah)

50 to 100 Amp-hr at 12 V DC ---->

 

[antennaguru]

I missed why you would want to bother with all of this when all you normally need to do is run a simple pair of wires to each speaker?!?!?

Oh, and how are you getting the music signal to these "cordless" speakers, blue-tooth, microwave link?

 

[pjug]

a DC amp or several can be used as with car amps


https://en.wikipedia.org/wiki/Automotive_battery#Amp_hours_(Ah)

50 to 100 Amp-hr at 12 V DC ---->

Are you wanting to run on 12V? The Aiyima that Amir reviewed (or any amp that similarly runs on an external power supply) would be easy to run from a battery: https://www.audiosciencereview.com/...ds/aiyima-a07-tpa3255-review-amplifier.18984/
There are other TPA3255 based amps with bluetooth built-in.

It would be nice to run from something like 48V. Although higher voltage lithium batteries are not so inexpensive.

 

[escksu]

13KJ is just around 3.61WH. i am not sure if that is sufficient.

 

[Trell]

I'm interested in how long you could run on 13 kJ (convert to W-hr if you want, it is all energy).

Let's just look at the amp - what would the current draw be - roughly?

You are not particularly clear about what your concrete use-case is. Current draw depends on the amp and what speakers you want to drive it with, along with the music you are playing. Obvious generalities, but for lack of information...

13 KJ, approximately the capacity of an AA alkaline cell, which is not much, if that is all you have. Then you are really power constrained and should plan accordingly.

 

[Wes]

ok, let's go with 15 MJ

consider it a thought experiment, based on where audio is going

 

[pjug]

ok, let's go with 15 MJ

consider it a thought experiment, based on where audio is going

Convert it to WH, Joules is W*s and it will be a lot of seconds.

15MJ is a huge bank of batteries, but (15MW*s)*(1H/3600s)= 4167WH. So if your idle power is 3W and you don't play too loud you'd probably get at least 1000hrs or so of continuous playing.

I don't get the point about this is where audio is going. You mean portable bluetooth speakers?