Currently playing with the idea of building a proper hifi portable battery powered player/speaker.
It must be a high power unit with sufficient bass for outdoor use.
As a speaker/amp setup I am thinking of a 3-way system.
Transmission line double coil subwoofer for <80Hz on 2 pieces of 150Watt class-D amps.
6" mid-woofers for 80 tot 2000Hz each on a 150Watt class-D amp.
Horn loaded 25mm soft dome tweeters with high sensitivity each on a class-D amp.
Battery powered with 2 batteries of 20V/4Ah coupled in parallel on the back.
A 7.9" touchscreen for control. On the top a large volume/mute button.
Materials to be used would be wood, 3D printed parts, stainless steal, 20mm MDF
Attached a render of this idea.
Some questions:
I am in doubt on the touchscreen on the front???
Is it possible to use “Now Playing” plugin in portrait mode?
No idea how long it would run on the 2 pieces 20V/4Ah batteries.
Assuming you run the 4 x 150W class D amp modules fairly hard, they’d use up to 150W of supply power each. With your total 8Ah battery supply at 20V you’d have around 160Wh.
Run time would be around 15 mins.
If the amps ran at less power output (more likely in real life) it would run for longer.
Only the sub-woofer amps would be likely to run toward the upper end of their rated output.
Thanks @pwstereo, 15 minutes at loud playing levels would not be what I am looking for as you can imagine.
The 150Watts output is max level. The RMS power output will be less.
The sub amps indeed will be the most challenging in power usage.
I try to setup a test with the amps driven loud with music and a dummy load.
There is of course also the Rpi and touchscreen using power. Would 25W for this combo in a calculation be realistically?
Regarding the power needs, it would be nice to hook it up to a power supply/charger when it is driven loud for longer periods. With the estimates Wheaten made, it will run 3.5 to 6 hours on a pair of batteries.
Thanks @Wheaten for the image of the portrait mode of “now playing”. There is not a lot of info on the screen. A lot of empty space. Most of the time while playing, it will have the Peppymeter screensaver. Here I am free to fill te screen more efficient.
It is difficult in this build to use the screen in landscape. The way the speaker construction inside the box is setup, allows portrait usage on the front of the top the best.
I may make a concept design with the display on the top middle panel.
you might consider placing the LCD on TOP, above the Volume button.
Also keep in mind that you need a redesign of a peppy template, as they don’t rotate by 90 deg.
A Bluetooth Hi-Fi player? - You’re so excited about the excellent playback quality of the Volumio, and here it’s Bluetooth?
Don’t you know what the actual Bluetooth transmission parameters are? Not the paper-based ones. Even the worst MP3 files will sound better over any cable or Wi-Fi connection than, say, a 192kHz FLAC file over Bluetooth.
This is the best way to ruin everything, regardless of the amplifier and speaker specifications. Although the visual design of the case itself is nice.
You are absolute correct on the specs of the Bluetooth protocol. The speaker will mainly be used over the garden wifi network so the quality of the stream will not be an issue. The Bluetooth capability is just one of the options may this be needed when using the unit where there is no wifi available.
I have no illusions on the sound quality of this project. When you play music outside you need totally different specs speakers as indoor. I hope it will sound powerful and clear, but it certainly will not sound as your regular indoor Volumio system!
This week the double coil 8" woofer and the 6" low/mid speakers came in.
I tested one of the amplifiers powered by a 20V Lion 4Ah battery and connected it to the workshop Linn speakers. I did no measurements but was surprised by the sound quality and power of this little class-D amp PCB.
I probably will use a small 8 output DSP processor to make an active 3-way crossover. The last output can be used as a line output.
The weight of this thing is becoming an issue. With all electronics, speakers, batteries, connectors and the complete 20mm thick speaker housing the Excell sheet calculates up to almost 40kg! The most weight is in the 20mm MDF housing parts. Since the speaker housing is of major importance for a nice bass, I do not want to compromise on this.
A transport trolley will be a must for moving the speaker around.
