# DIY Bluetooth speaker for daughter



## NealfromNZ (Sep 3, 2013)

Haven’t done a diy audio project since the BMW M3 of a number of years ago.

This mini project is going to be daughters first stereo. She’s coming up on 9 and is into playing piano / keyboard and dancing ballet and hip hop.

I want to build a semi portable Bluetooth speaker with enough power to fill a room yet run on battery for a few hours at moderate volume.

kit
FOSI audio class D 2.1 Amp roughly 50w x 2 & 100w x 1 at 24volts DC. Mains power adapter 24volts

Soundstream st4 two way 4inch speakers 

Tang Bang W5 subwoofer 5.25 inch
Dayton passive radiators 5.24 inch x 2

Dayton battery pack / charger rated up to 24 volts 10 amps

5 x 3.7v 5 amp 26650 lithium batteries.

Pine plywood ( couldn’t get birch locally )
1200x600x17 & 1200x600x12.7

Tolex vinyl

Retro fill cloth


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## MattAFLiving (Aug 27, 2021)

This looks like a fun project. Ill be following!


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## Focused4door (Aug 15, 2015)

That looks like it will be awesome, it is disappointing how terrible most of the blue tooth speakers are.


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## NealfromNZ (Sep 3, 2013)

I think your right on many Bluetooth speakers. I remember hearing one of the larger Marshall units which was a stepped uplift from others I’d heard.

Price wise they are close to $900 dollars in NZ so I thought I’d have a go at building one using my old 4 inch rear fill speakers from an BMW e36 build. They didn’t sound to bad but had no real bass to speak of.

Hence the choice of the subwoofer. Apparently that little TB sub can get down to 34hz in a 8 inch cubed enclosure with a couple of passive radiators.


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## Old Skewl (May 30, 2011)

subscribed


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## NealfromNZ (Sep 3, 2013)

Settled for a a box roughly 17Wx13Hx9.5D will roughly give the sub and passive radiators roughly a 8x8x8 box so F3 in the mid 30hz range.

The 4 inch car speaker at this stage will go into dual sealed chamber.

The amp and battery pack will go into a vented rear chamber with amp recessed into the top of the enclosure.

Building cabinet out of 3/4 pine ply. I only have basic wood tools so marked up wood and used skill saw and guide.
























I filled the edges with PVC glue as a number of voids where exposed post cutting. Think I prefer working with MDF.

Working through rough positions of components.


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## NealfromNZ (Sep 3, 2013)

More wood work done and a bit of a mock up. Bottom chamber will house Tang Band W5 sub and 2x Dayton 5 1/4 passive radiators. Have model the space in winsd which will give a rise in the 60-90 hertz region and rolls off quickly 50hz and all over by 42hz. Roughly an area of 10 litres.
Upper chamber will be sealed and divided into 2 to give roughly 2.2 litres for each of the Soundstream 4 inch two way speakers.

Battery pack and Amp will sit within own vented chamber at rear.










Amp controls will be recessed into top cover.
Added some rivnuts to the case so amp can be bolted and adjusted within chamber.


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## NealfromNZ (Sep 3, 2013)

Next stage is working with the Dayton battery power supply. It’s quite a flexible unit and can be charged with 5-24v DC. I’ll use a combo of the 2.1 amplifiers 230v/ 24v 6 amp supply and also have a 12v dc lead so it can be charged via cig lighter in the SUV.

I’ll need to de-soldered some of the plugs and run DC power leads between PCB and AMP..
The power supply can deliver peaks of 24volt / 10 amps which above what the class D 2.1 amp needs for 50x2 and 100x1 max output.

The PSU will also feed two USB ports for charging or running USB 2 accessories.

Thinking ahead with a phone for the daughter when she’s old enough and possibly a usb guitar pickup as she’s just got an acoustic guitar and is picking it up quite quickly.


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## NealfromNZ (Sep 3, 2013)

Just realised I’d started this 6 months ago.
Had a medical event in December which meant open heart surgery and some complications after. But now able to work on stuff again in small doses.

Build up the back paneL. Added a plastic equipment box lid for access to batteries, made a vent grill out of an old speaker grill.
Added a two port usb charger to the plastic panel that also uses the lithium battery power pack.

Made up a panel for DC power input, aux and battery status led using a speaker equipment handle.


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## NealfromNZ (Sep 3, 2013)

My first attempt at wrapping. Fortunately using tolex so it’s reasonably robust material. I really take my hat off to audio pros and amateur diy that can wrap and stretch vinyl to go around corners and into cut outs.


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## Focused4door (Aug 15, 2015)

You should have made two of these, by the time you are done you will want one for yourself also


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## NealfromNZ (Sep 3, 2013)

Focused4door said:


> You should have made two of these, by the time you are done you will want one for yourself also


I reckon. A portable unit would be handy.

Although next audio project will be on a retro modded 1963 Morris mini. 😀


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## Old Skewl (May 30, 2011)

It turned out really nice. Better than I could have done. LOL!


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## Kyleag89 (8 mo ago)

That looks great! Im in the process of building a similar box for myself to use in the garage and at work. How do you like the amplifier you chose to use and do you think it would work for 2 6.5" speakers and a 6.5" subwoofer? Thanks


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## Old Skewl (May 30, 2011)

I have been looking at some of this guy's designs using Pelican cases. It would be a good winter project.


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## NealfromNZ (Sep 3, 2013)

Kyleag89 said:


> That looks great! Im in the process of building a similar box for myself to use in the garage and at work. How do you like the amplifier you chose to use and do you think it would work for 2 6.5" speakers and a 6.5" subwoofer? Thanks


The amp has quite good sound quality for the price point. Power output needs 4 ohm loads for optimal output . I did try it on a pair of 3 way 10 inch floor standers and a old Boston 10 inch sub via rca and Bluetooth and it sounded just fine.

Running with 4” and 5.25 sub and seems best for output and sound crossed over around 120- 150 hz.

Id by the fosi audio brand again for other similar projects if that helps with a recommendation. To too hard to run off lithium batteries and run for a reasonable time between charges.


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## NealfromNZ (Sep 3, 2013)

Almost a year since I started this, finally finished about 3 weeks before daughters 10th birthday. Things got a bit sketchy during year. Heart failure then an operation so glad I got to finish the project for her. 

Couple of learnings. First was don’t presume old car speakers still work and second was the box could have been a bit less complex if I’d thought about it.

So I brought another set of 4 inch two ways , but fortunately same OEM as the soundstream ones but with kevlar cones and the same tweeter.

The little Tang Band w5 produces good low bass for such a small driver and sound from the speaker system more than able to fill a room.

Finished speaker.


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## NealfromNZ (Sep 3, 2013)

Daughters birthday has rolled on. The bass performances is better than expected for a small woofer. Have to back it off a bit for the 4inch speakers to keep up. Running bass unit up to 200 hz and blending in ok. A quick test in her room sound level got to 95 db so plenty loud enough.
Batteries last well at a moderate volume. Got past the 4 hour mark with roughly 1/4 left.

I did change the power input. The 24v power supply goes direct into the amp which is switched via 24v relay when using left DC input. The middle dc input goes via Dayton / Lion supply.
Did this as the thought of having lion batteries of this size always on charge in a bedroom is a potential risk. So batteries will be charged before taking anywhere or to dance studio.


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## saltyone (Feb 2, 2019)

Amazing work Neal! I feel like less of a father after reading this thread. 😂

Your daughter should be very proud! Good luck with the health concerns. Stay strong…at 10 years old, you’re just getting into the fun part of raising a daughter. Mine just turned 22. I miss the dance competitions, ballet recitals, guitar lessons, and everything else she was involved in. Again, amazing work!


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