[SOLVED] Improving the sound quality of the sound bonnet speakers

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mad_ady
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[SOLVED] Improving the sound quality of the sound bonnet speakers

Unread post by mad_ady » Thu Sep 07, 2017 6:48 pm

Disclaimer: I pride myself with the fact that I am *not* an audiophile and can listen to music with poor encoding and bitrates without noticing it.
I got the boom bonnet to play with it and mostly to replace a usb sound card + usb powered speakers (that you can get for 5€) that take too much room. Also, I use the USB bus for a webcam and sometimes need to reset it via a watchdog and this can create clicking sounds in the speakers in the middle of the night - which I was looking to fix.

I used hotglue to attach the speakers to their PCB (as instructed in the wiki) and tied the bonnet with zip-tie to a cable next to the C2.
The problem is - when I listen to audio/music, the sound doesn't seem right. It's distorted in a way, but I'm not sure in what way exactly - I'd say it's more metallic, less warm sound.

I've attached headphones and a pair of cheap passive speakers to the 3.5" headphone output and the sound quality was great. However, when I listen through the supplied 2W speakers, the sound is off, and I'd like to understand why and what can I do about it.

Here's an audio recording of the bonnet that I did with my cell phone: https://m.mediafire.com/view/ob8bdj03yw5f16a The first 10s are audio output through the passive speakers (and the quality is fine in my opinion, although the loudness is a bit too low for the room). The following 20s are recorded from the builtin speakers (they start at maximum volume, and I decrease the volume progressively). Audiophiles - be warned - listen at your own risk! :)
Image

I did a frequency plot in audacity of both sections, and the passive speakers which for me are acceptable only output about 5KHz bandwidth, while the bonnet outputs to 15KHz (or more, but my microphone only picked up 15KHz).
Image
Image

So - what makes the speakers sound so bad? Is it:
1. The lack of a case/resonant enclosure?
2. The volume? Based on the waveform, it's a few orders of magnitude over the passive speakers, but there is no obvious clipping. Maybe clipping happens only when recording and playback manifests itself in other ways.
3. The speaker size? (the passive speakers were not much bigger in diameter, but were in a case)
4. Has my hearing gone bad and is unable to recognize quality sound? :)
5. Is speaker placement an issue? The fact that they are dangling from a wire and are not screwed into a stable surface to absorb vibration?

What suggestions can I get to improve the quality of sound from the builtin speakers? I was thinking of:
1. Use a pulseaudio equalizer? If yes, what settings would be best for music? (I haven't used an equalizer before!)
2. Disconnect the original speakers and replace them with the passive ones + their enclosure?

I noticed there are two jumpers on the bonnet to control "Digital Filter Latency and Performance". I played with the jumpers, but I didn't notice anything in the audio output. Probably the jumpers won't help.

So - any suggestions?

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Re: Improving the sound quality of the sound bonnet speakers

Unread post by phaseshifter » Thu Sep 07, 2017 10:41 pm

So - what makes the speakers sound so bad? Is it:
1. The lack of a case/resonant enclosure?

yes the lack of casing is for the most part the problem no enclosure....

and yes connecting passive speakers with enclosures would make a big difference..
Last edited by phaseshifter on Fri Sep 08, 2017 3:15 am, edited 1 time in total.
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Re: Improving the sound quality of the sound bonnet speakers

Unread post by phaseshifter » Fri Sep 08, 2017 3:08 am

i dont know if you have egg containers over there like the ones we have here but if you cut out carefully 2 cups off the box and get some silly putty /bluetak..these would make for a good rear enclosure for the speakers...

my boom bonnet comes this week so i will let you know how i go with it all..phase...
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Re: Improving the sound quality of the sound bonnet speakers

Unread post by mad_ady » Fri Sep 08, 2017 3:32 am

Do you mean egg container made from cardboard? I have those. I could attach it with hotglue. If you have time to try it out I'd love to hear some advice, thanks!

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Re: Improving the sound quality of the sound bonnet speakers

Unread post by phaseshifter » Fri Sep 08, 2017 3:47 am

yes the cardboard ones....hot glue yep that would do it...
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Re: Improving the sound quality of the sound bonnet speakers

Unread post by phaseshifter » Fri Sep 08, 2017 9:49 am

on a further note you could use a small funnel h-ware shops will have them the funnel idea has a good method of porting which may just ad some performance and exta cc`s to the option..ok you can block the end off you could try either way
anothey way look for a plastic spraypack can lid a small diameter one this would give good cc`s...
yet another method go to the chemist and get a measuring cup..a small one...this will prolly give the best cc`s wise.. options i will try all when i get my hardware...phase...
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Re: Improving the sound quality of the sound bonnet speakers

Unread post by Ameridroid » Fri Sep 08, 2017 1:40 pm

Here at ameridroid, we designed an 80s style boom box for the whole thing to fit in including amplification channels for the speakers. We'll be posting a project video on it soon, as well as the 3d print files.

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Re: Improving the sound quality of the sound bonnet speakers

Unread post by mad_ady » Fri Sep 08, 2017 2:12 pm

@ameridroid: is it using the boombox hardware as base? Also, does it have a tape loader and red/yellow leds on the sides in '80s style?
@phase: I have some measuring cups from baby formula I could use

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Re: Improving the sound quality of the sound bonnet speakers

Unread post by mad_ady » Mon Sep 11, 2017 5:16 pm

@phaseshifter: I take it you have received your boombox. Have you managed to MacGuyver anything to make it sound better? I'm slowly getting used to the bad sound and I'm not minding it as much, but for the sake of my kids, I'd like to fix things :lol:

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Re: Improving the sound quality of the sound bonnet speakers

Unread post by phaseshifter » Mon Sep 11, 2017 5:20 pm

did you read my thread about the earthing required to stop the pop`s and crackles
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Re: Improving the sound quality of the sound bonnet speakers

Unread post by phaseshifter » Mon Sep 11, 2017 5:23 pm

thinking about a cardboard box cut an rectangular hole and mount it that way maybe a tissue box..but am not up to that just yet
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Re: Improving the sound quality of the sound bonnet speakers

Unread post by mad_ady » Mon Sep 11, 2017 5:37 pm

phaseshifter wrote:did you read my thread about the earthing required to stop the pop`s and crackles
No, which thread is that. What earthing do I need to connect? The board has GND to the Odroid, isn't it enough?

Regarding a cardboard box - do you want to attach the bonnet to a box, not just the speakers?

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Re: Improving the sound quality of the sound bonnet speakers

Unread post by phaseshifter » Mon Sep 11, 2017 6:13 pm

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Re: Improving the sound quality of the sound bonnet speakers

Unread post by mad_ady » Thu Sep 21, 2017 9:19 pm

Ok, I managed to implement @phaseshifter's solution and used two XU4 cardboard boxes with rubber bands and fixed the audio issues I was seeing. I spent a while trying to figure out how to run the rubber bands through the mount holes, but luckly it was easier to run the bands vertically instead. Take care not to break the audio wire when mounting the rubber bands (had to solder it back together).
Also make sure the box is in good contact with the speaker.
Here is a visual guide: https://imgur.com/a/w5LEI
The results are amazing - even with Bohemian Rhapsody :)

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Re: [SOLVED] Improving the sound quality of the sound bonnet

Unread post by odroid » Fri Sep 22, 2017 7:33 am

Nice paper box speakers. :D

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Re: [SOLVED] Improving the sound quality of the sound bonnet

Unread post by mad_ady » Fri Sep 22, 2017 11:39 pm

Some would say it's too pricey, but quality demands sacrifices.
Oh, I forgot to mention that I removed the XU4s from the boxes prior to installation :)
@odroid: are you considering adding an enclosure/minimal cardboard schematics to improve the audio quality?
Here's an audio sample from 'after': https://www.mediafire.com/file/g2ybav4t ... ce+002.m4a

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Re: [SOLVED] Improving the sound quality of the sound bonnet

Unread post by odroid » Sat Sep 23, 2017 6:40 am

Thank you for the audio sample. It is quite louder and clearer with the paper box amplifiers.
We are not good at designing a cardboard speaker box. :(

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Re: [SOLVED] Improving the sound quality of the sound bonnet

Unread post by Technicavolous » Wed Nov 01, 2017 2:34 am

I added my boxes to this thread viewtopic.php?f=118&t=28219
What box?

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