DIY: Building a little BoomBox project
- Thread starter NickK
- Start date
Slow progress at the moment due to priorities. I'm making a circular saw table for the smaller cuts and now the garage is physically connected to the electrics rather than an extension cord, it should be a bit more organised.
However some more O-scopery.
First the noise of my simple linear regulated power supply:
Next the noise of my SMPS power supply:
And finally the noise (not muted) at the speaker:
So the more -dB the quieter the noise floor is. As you can see the SMPS switching means you get quite a bit of noise, however a Digital amp (ie Class D) also performs switching at high speed so the output of the amp has a filter on to both combine the digital signal into a analogue wave (like an integrator) but this also provides a level of "noise reduction" in that the peaks appear to disappear but the average noise is higher.
The main criticism of digital amps/SMPS is it reduces the quality of audio - specifically "sss" sounds due to the interference, I would conclude that this could be apparent in this build, although I may look at adding filtration post SMPS - the system doesn't need the full 19V as it functions happily on 13.6V so I could add some supply filtering.
However some more O-scopery.
First the noise of my simple linear regulated power supply:
Next the noise of my SMPS power supply:
And finally the noise (not muted) at the speaker:
So the more -dB the quieter the noise floor is. As you can see the SMPS switching means you get quite a bit of noise, however a Digital amp (ie Class D) also performs switching at high speed so the output of the amp has a filter on to both combine the digital signal into a analogue wave (like an integrator) but this also provides a level of "noise reduction" in that the peaks appear to disappear but the average noise is higher.
The main criticism of digital amps/SMPS is it reduces the quality of audio - specifically "sss" sounds due to the interference, I would conclude that this could be apparent in this build, although I may look at adding filtration post SMPS - the system doesn't need the full 19V as it functions happily on 13.6V so I could add some supply filtering.
So I've now spent a little time dealing with the garage:
1. electrified the garage and replaced the strip light with an LED light.
2. built a circular saw table + shuttle with clamp out of a circular saw and some old 18mm floor particle board.
3. built a router table out of a 1/4" router and 18mm floor particle board that's been routed out to give about 12mm of routing depth
Version one of the front panel I used a 74mm holesaw and attempted to hole saw the 100mm wide 3mm recess using a drill press. Nope. The detachable hole saw is way to inaccurate.
Version two sees the use of a 6mm drill hole through the wood, and in the router board to give a diameter sweep with the 6mm router bit from underneath. This means I can make circles smaller than the router bit. In this case I was guessing on the diameters a little after realising that I needed to add 1/2 the drill bit - the result is a little larger than was expected but better result:
A 45 deg router bit on the inside means the back side airflow is better.
The router bit kicked sending the piece across and plunged into the side wall. Well this was a good second version of the front piece. What is good is the process is very repeatable and accurate.
1. electrified the garage and replaced the strip light with an LED light.
2. built a circular saw table + shuttle with clamp out of a circular saw and some old 18mm floor particle board.
3. built a router table out of a 1/4" router and 18mm floor particle board that's been routed out to give about 12mm of routing depth
Version one of the front panel I used a 74mm holesaw and attempted to hole saw the 100mm wide 3mm recess using a drill press. Nope. The detachable hole saw is way to inaccurate.
Version two sees the use of a 6mm drill hole through the wood, and in the router board to give a diameter sweep with the 6mm router bit from underneath. This means I can make circles smaller than the router bit. In this case I was guessing on the diameters a little after realising that I needed to add 1/2 the drill bit - the result is a little larger than was expected but better result:
A 45 deg router bit on the inside means the back side airflow is better.
The router bit kicked sending the piece across and plunged into the side wall. Well this was a good second version of the front piece. What is good is the process is very repeatable and accurate.
Well "first voice" in that this box is held together with framing kit (ie corner and cord) that you can't see. The port piece is missing but it gives an idea of the sound:
The Mrs wants to vinyl decorate the outside anyway so the fact there some glitches etc is not a problem. I'll get a 90degree vice tomorrow then I can start glueing the things together. I need to order some wool felt too then I can finish the speakers and the little equipment section that will sit on top of it.
How do they sound?
Decent. I'll know more when the things are fully built with the port piece in place and inside sealed.
They can play quietly but with a good sound, they have some balanced bass but as you'd expect it doesn't extend down like a large pair of quarter wave floor standers would.
The Mrs wants to vinyl decorate the outside anyway so the fact there some glitches etc is not a problem. I'll get a 90degree vice tomorrow then I can start glueing the things together. I need to order some wool felt too then I can finish the speakers and the little equipment section that will sit on top of it.
How do they sound?
Decent. I'll know more when the things are fully built with the port piece in place and inside sealed.
They can play quietly but with a good sound, they have some balanced bass but as you'd expect it doesn't extend down like a large pair of quarter wave floor standers would.
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So the initial rough glueing is ready for the wool felt, once that's done I can glue up the side and sand it. There will be a cable hole up the top of the unit to connect to the amp & screen area above it. Oh yes - managed to cut my finger - but that will disappear when I give it a final sand.
The port tuning (the little bit of ply that faces back into the enclosure that the cable skirts around really helps the sounds of the speaker. Previously I was a little worried about sounding a little in a room but that has worked really well. The final wool inside will reduce transmission of waves and the final side glued on should help the the ridigity further.
I'm contemplating giving it a expoxy coat inside. It will take a week to go rock hard. However for this first attempt I thought it would be a good idea to simply keep things as simple as possible.
PVA wood glue with the ply keeps the entire thing rigid so it probably won't benefit from any internal bracing given the small cabinet size. I have some small offcuts I could make a brace from.
The port tuning (the little bit of ply that faces back into the enclosure that the cable skirts around really helps the sounds of the speaker. Previously I was a little worried about sounding a little in a room but that has worked really well. The final wool inside will reduce transmission of waves and the final side glued on should help the the ridigity further.
I'm contemplating giving it a expoxy coat inside. It will take a week to go rock hard. However for this first attempt I thought it would be a good idea to simply keep things as simple as possible.
PVA wood glue with the ply keeps the entire thing rigid so it probably won't benefit from any internal bracing given the small cabinet size. I have some small offcuts I could make a brace from.
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Took the setup and showed the mrs with the speaker drivers now screwed in (although still open on one side - the felt should arrive today!). She listed a musical that she'd not listened to for 20 years and was singing along 
so I think it got the thumbs up.
I think it surprised her that it can play airplay and be controllable from her iPad too. In a larger room, which has painted walls and hard floor, the sound was loud enough and with a decent bass. There's a touch of 'enclosed speaker sound' on the odd occasion which I'm hoping will disappear with the felt.
I'll strip them back down and give the boxes a flat sanding and fit the felt, but that has been a good test. Next steps are to embed the screen, the secondary power supply and USB hub, add the volume controls and IR sensor into a small box that will sit above the speakers.
EDIT: Once I have everything sanded and done, I'll take photos then she can do some vinyl work and see the difference. I has occurred to me that given the bathroom requirement, some varnish/epoxy sealant would actually be a good idea - it will help the rigidity but also it will protect the ply from absorbing any moisture and expanding.
so I think it got the thumbs up.I think it surprised her that it can play airplay and be controllable from her iPad too. In a larger room, which has painted walls and hard floor, the sound was loud enough and with a decent bass. There's a touch of 'enclosed speaker sound' on the odd occasion which I'm hoping will disappear with the felt.
I'll strip them back down and give the boxes a flat sanding and fit the felt, but that has been a good test. Next steps are to embed the screen, the secondary power supply and USB hub, add the volume controls and IR sensor into a small box that will sit above the speakers.
EDIT: Once I have everything sanded and done, I'll take photos then she can do some vinyl work and see the difference. I has occurred to me that given the bathroom requirement, some varnish/epoxy sealant would actually be a good idea - it will help the rigidity but also it will protect the ply from absorbing any moisture and expanding.
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Carpeted
Just listening to them - the sides are still simply held together by being next to the other speaker.
First impression is that there is less "speaker in the box sound" which is good. The bass is tighter and it seems to have cleaned up the clarity a notch or two. There's definitely a clearer kick drum.
Next steps:
1. switch the speaker cable to the QED cable I planned to use (the issue is that it's too stiff.
2. put a hole in the top for the speaker cable.
3. put a little filler in the router scar
4. take the drivers out and wood glue the side on.
5. make the top section for the components.
6. give them a proper sanding.
Just listening to them - the sides are still simply held together by being next to the other speaker.
First impression is that there is less "speaker in the box sound" which is good. The bass is tighter and it seems to have cleaned up the clarity a notch or two. There's definitely a clearer kick drum.
Next steps:
1. switch the speaker cable to the QED cable I planned to use (the issue is that it's too stiff.
2. put a hole in the top for the speaker cable.
3. put a little filler in the router scar
4. take the drivers out and wood glue the side on.
5. make the top section for the components.
6. give them a proper sanding.
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So the the boxes are now fully glued - there's some cosmetic work needed but I was impatient to listen to the difference.
In addition, the cable has now been replaced with the final cable, routed through the top where the board will sit. You can just see the SMPS power filter next to it.
Sound is decent, lacking in bass compared to the quarter wave setup I'm used to as speakers but the the sound works. Next up is to make the top box for all the components which I've started today.
In addition, the cable has now been replaced with the final cable, routed through the top where the board will sit. You can just see the SMPS power filter next to it.
Sound is decent, lacking in bass compared to the quarter wave setup I'm used to as speakers but the the sound works. Next up is to make the top box for all the components which I've started today.
So a little delay in this - back story is i’ve been moving about 8 tons of soil and breaking up concrete which has inflamed carpel tunnel and strains on my wrists. So trying to hold a sander or router is painful.
Todo:
DONE cut and route screen hole, volume, power and USB connector holes.
* glue speakers together (the box is to be one chunk)
DONE glue top pieces to make the top box
* secure the top piece - i may use wood screws so i can access the top electronics.
* soft corner route the box edges
* sand the crap out of box and top together.
* order some small/thin HDMI and usb cables (i may make the USB cables)
* secure the components in the top and fold the speaker cable - the new stuff is less flexible.
so i’m going to try to get it finished over the next two weeks.
EDIT - I think I'll also make front plate which has pins+magnets to keep in place to protect the speaker cones.
Todo:
DONE cut and route screen hole, volume, power and USB connector holes.
* glue speakers together (the box is to be one chunk)
DONE glue top pieces to make the top box
* secure the top piece - i may use wood screws so i can access the top electronics.
* soft corner route the box edges
* sand the crap out of box and top together.
* order some small/thin HDMI and usb cables (i may make the USB cables)
* secure the components in the top and fold the speaker cable - the new stuff is less flexible.
so i’m going to try to get it finished over the next two weeks.
EDIT - I think I'll also make front plate which has pins+magnets to keep in place to protect the speaker cones.
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Have to ask, why all the messing around with software?
Why not just wire up a CD transport to a hardware DAC to an amp and skip all that faffing about?
Cool project though!
My faff-free audio for the dining room is a B&W A7 with an Echo Dot, although it pains me a little to waste the audio quality of the B&W on the ropey Echo DAC....
Why not just wire up a CD transport to a hardware DAC to an amp and skip all that faffing about?
Cool project though!
My faff-free audio for the dining room is a B&W A7 with an Echo Dot, although it pains me a little to waste the audio quality of the B&W on the ropey Echo DAC....
The software option provides a few additional options:
* sound equalisation - if the build needed a little more bass or to take the shine off the treble, I can do that
* digital streamed internet radio channels including the French 80s pop etc
* audio from apple devices streamed - from tablet or iPhone.
* works off 19Vdc so it can be sat in a bathroom.