Built-in speaker is quiet and doesn´t sound good

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DJ4DI
 

Posts: 2
Joined: 19 Jan 2023, 13:58

Built-in speaker is quiet and doesn´t sound good

Post by DJ4DI »

Hi,

my new (tr)uSDX for the Lo Bands runs perfectly after assembly.
The audio playback is good with both headphones and an external speaker.

I have a question about the built-in speaker. The playback is very quiet and the "full" sound is missing.
I don't expect miracles from such a small part, but the volume and sound could be a little better.

Maybe I installed it the wrong way around because the speaker wasn't marked with plus and minus.
Then I should swap the connections. Or just use a different type.

Is it worthwhile for me to deal with this topic?

Otherwise I leave everything as it is.

73,
Klaus-Peter
DJ4DI
dl6sez
 

Posts: 399
Joined: 30 Dec 2021, 22:54

Re: Built-in speaker is quiet and doesn´t sound good

Post by dl6sez »

Hello OM Klaus-Peter,

as you recognized by yourself it is a useless question...
Use Headphones or an external active speaker.
The speaker is directly connected to the Atmega328 and is not capable of sounding like
a big HiFi speaker therefore :)
Anyway you can use it!

73 de Chris
Chris DL6SEZ, JN48XL near Ulm, Southern Germany
DJ4DI
 

Posts: 2
Joined: 19 Jan 2023, 13:58

Re: Built-in speaker is quiet and doesn´t sound good

Post by DJ4DI »

Hi Chris and Manuel,

Thank you very much, now I can correctly classify the topic.
Sorry, I couldn't find the video when googling.

Long story short:
The (tr)uSDX was not dimensioned for operation with loudspeakers.
The built-in speaker is intended more as an emergency solution.
Playback is very good with headphones, a headset or active speakers.

I will also try the operation with active speakers wirelessly with a Bluetooth dongle. This reduces the cables ;)

73,
Klaus-Peter
DJ4DI
storyofyouandme
 

Posts: 54
Joined: 03 Jan 2022, 15:30

Re: Built-in speaker is quiet and doesn´t sound good

Post by storyofyouandme »

TRUSDX uses 23MM speakers to achieve this effect is already very good. I have used 20MM speakers, and the effect is worse, but the effect of 40-50MM speakers will be much better. Even if the power amplifier circuit is used, it can only increase the volume, which will not improve the sound quality. So don't worry about the speaker. For such a small machine, the DL2 speaker design scheme is already the preferred one. I hope it can help you.
73.
Df5GF
 

Posts: 22
Joined: 31 Dec 2021, 10:01

Re: Built-in speaker is quiet and doesn´t sound good

Post by Df5GF »

When I connect a bluetooth tx (1mii Bluetooth Adapter) to the socket audio, the lambic button no longer works ….correct. Audio at headphones ist ok.
Any idea?

Franz
DF5GF
WB2CIK
 

Posts: 3
Joined: 08 Feb 2023, 04:50

Re: Built-in speaker is quiet and doesn´t sound good

Post by WB2CIK »

Cutting notches (like a castle) about 1/16th inch (1.5mm) by 1/16 inch (1.5mm) around the circuit board side of the speaker mounting ring helps the audio level and fidelity a little. Venting the back side of the speaker into the volume between the front cover and main board is a start. Perhaps some carefully placed holes can be added to both the Main and the RF boards to somewhat utilize the volume of the entire case..

Above a volume setting of 13 it still gets scratchy, both with the internal speaker or external headphones.
I had suspected 10n C37, was the culprit, being on the PB1 output pin.
But a 270 ohm resistor R23 is switched in series when in the external headphone mode.

The identical problem occurs with internal speaker or headphones, therefore mechanical feedback can be ruled out.

Now suspecting some sort of software overflow in the timing of the 78 kHz pulse width modulated audio on PB1.. The PWM could run slower, as we are only generating communications audio, say 3 kHz max..
WB2CIK
 

Posts: 3
Joined: 08 Feb 2023, 04:50

Re: Built-in speaker is quiet and doesn´t sound good

Post by WB2CIK »

I looked further into why it gets scratchy with a volume setting of 13 or greater.

The duty cycle modulation of the 78.13 kHz PWM begins to exceed 100% High and 100% Low,
breaking into the next cycle of the 78.13 kHz speaker signal..
Appears to be a math problem in the software..

As to the loudness of the speaker,:
With the present software at volume setting 12,
the maximum peak to peak audio possible is being generated,
just using the PB1 port on the microprocessor.
Fixing the math problem above will not make it louder.

It may be possible to improve loudness via changes to the printed plastic case.
Better to modify the plastic than modify the circuit boards !!!

Venting the back side of the speaker into the volume between the front panel
and the main board helped a lot with fidelity.
It is now still low but intelligible..

180 degree out of phase audio is leaking out around the display, push buttons, microphone grill, and edges of the cover, cancelling a lot of the desired audio.
A solution may be to pipe the back side of the speaker into the back cavity (where the filter toroids are) of the case.

I'm thinking 2 changes are needed:
First is a more complex speaker mount that adds a duct from the back of the speaker down around both sides of the "set" push button to the bottom side wall.
Second is a new bottom side wall with a duct that matches up with the new speaker mount and empties
into the back 1/3rd of the case...

It might be possible to also use the space between the board, but I'm thinking the 2 boards may better seal the back chamber from the front..
WB2CIK
 

Posts: 3
Joined: 08 Feb 2023, 04:50

Re: Built-in speaker is quiet and doesn´t sound good

Post by WB2CIK »

Attached is a photo of my notched speaker mounting ring, epoxied to the front cover..
speaker_mounting.jpeg
speaker_mounting.jpeg (71.95 KiB) Viewed 881 times
73 John WB2CIK
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