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Old 19th May 2015, 04:13 PM   #1
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Default Peapod - A pocket sized mini speaker

Hi all I don't post often here but lurk a lot and on other audio forums - I'd just like to share some details of a project I've been working on:

Click the image to open in full size.

Nothing concrete to show right now besides some pretty renderings, I have a rough prototype built that I'm working with now to test driver suitability - it's 2.5" with a shallow profile so the overall depth of the unit should be around 35mm total and the remaining dimensions around the same as an average to large smartphone. I have a little shower radio of around the same dimensions and can confirm it's comfortable to carry around in a jeans pocket if necessary - enough to forget it's there anyway. Jacket pockets no problem.

Total enclosure volume is only about 0.2 litres giving little below 150Hz, but the driver has an unusually high xmax for the size, going right to around 3mm (and on many tracks even at this level it still sounds great), which couples with the psychoacoustic principle of the missing fundamental to give a deceptively powerful bass response. Very hifi too - listening to a prototype now and it is fantastic.

With a TPA3132 amp and a 3 cell (true 12 volts) lipo it could theoretically be run up to 35 'real' (~0.2% THD) Watts with a maximum SPL of 101.5dB at one metre.

The plan is to eventually go fully open source with this, and to be as non commercial as possible, but as there are a lot of custom moulded parts involved and a lot of hard grind design work to do before it's ready, it'll need quite a large Kickstarter campaign if it's going to happen at all. To keep things simple it'll be distributed in kit form (just screw + glue enclosure, no soldering) at first with more or less a costs + handling price point.

I don't really want to make a business out of this, but I do want to see it happen, and want it to be amazing - I'm experimenting with ways to circumvent the corporate process altogether that would involve some form of decentralised costs + donations based payment system.

Lots still to determine and a long development path ahead. Right now it's just me doing the general design and trying to fumble my way through parts engineering (and praying it's all practically possible in terms of machine tolerances etc as far as it seems to be to me), and another forum member (who made these very tiny amps Really really small TPA3132 amp) doing board layout/programming, I've got a lot to learn before this is anywhere near real but also have full commitment to seeing this through, as it's been in mind in one way or other since around 2009 (though only really in development for a few months now)
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Old 19th May 2015, 05:00 PM   #2
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I was going to comment on speakerplans that I think it's a really bad choice of name for an otherwise cool project. Everything has to be pod these days... but a pod you pee in? No thanks. That's the unfortunately word association I and I suspect many others get.

Don't use LiPo batteries for this. Use NMC cells. They're much cheaper, holds more capacity per volume, have much better high current drain properties, and are much safer. Not as safe as or as good high current drain properties as LFP cells but close.

This looks to be a traditional "stomp box" size speaker such as those popular on the 41hz forum for use with the amp32. A stomp box is traditionally a standard industry alu or plastic enclosure in a particular size, usually 121x66x37mm. These can be found in any colour you like for very little cost.

Last edited by Saturnus; 19th May 2015 at 05:03 PM.
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Old 19th May 2015, 05:12 PM   #3
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Quote:
Originally Posted by Saturnus View Post
I was going to comment on speakerplans that I think it's a really bad choice of name for an otherwise cool project. Everything has to be pod these days... but a pod you pee in? No thanks. That's the unfortunately word association I and I suspect many others get.

Don't use LiPo batteries for this. Use NMC cells. They're much cheaper, holds more capacity per volume, have much better high current drain properties, and are much safer. Not as safe as or as good high current drain properties as LFP cells but close.

This looks to be a traditional "stomp box" size speaker such as those popular on the 41hz forum for use with the amp32. A stomp box is traditionally a standard industry alu or plastic enclosure in a particular size, usually 121x66x37mm. These can be found in any colour you like for very little cost.
Maybe Anyways, the name, lipo battery power, and enclosure style are all more or less set.

I thought the same for ages but it grows on you and the stylings make it more clear when you see the rendering in 360, it's one of a line of designs I've got in the works that share the same name and for plenty of good reasons that become more apparent when viewed and used together.
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Old 19th May 2015, 05:24 PM   #4
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Hahaha, I had that association too. Would be a great name for a toilet speaker ;p
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Old 19th May 2015, 05:31 PM   #5
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I still remember thinking the iPad sounded like a sanitary towel
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Old 19th May 2015, 05:53 PM   #6
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It is so a Peapod though even if it has to be coloured all shades of green with the word peapod engraved in little metal peas down the side to drive the point home:

Click the image to open in full size.

If the name and stylings are so objectionable then hopefully the open source nature will bring with it less objectionable alternatives (3D printed case + component kits available opens no end of possibilities)
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Old 19th May 2015, 06:24 PM   #7
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Originally Posted by Hemisphere View Post
I still remember thinking the iPad sounded like a sanitary towel
It still sounds (and to some extend looks) like that.
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Old 19th May 2015, 06:30 PM   #8
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Click the image to open in full size.

I know it sounds silly but I do really think it looks like a peapod and it was designed with pure functionality and ergonomics in mind (as large as possible curves in all places for going in a pocket)
Oh and it is waterproof so if you really wanted to you could pee on it. Add some green jack leads - daisy chained it'd be like pods on a vine - and appropriate graphic design in all packaging/website and so on I think people would get it - Unless they're urophiles or something.

Last edited by Hemisphere; 19th May 2015 at 06:36 PM.
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Old 19th May 2015, 07:29 PM   #9
gmarsh is offline gmarsh  Canada
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Just some thoughts...

- How are you doing battery charging, cell balancing/protection, etc?
- How are you providing waterproofing for the audio/charging inputs?
- Plastic mold design is very expensive, especially what you've got there - I see tons of sliders and at least one overmolding operation. Personally I'd keep this in 3D printed land instead of attempting to go for volume.
- You'll need various industry certifications if you turn this thing into a sellable finished good. Those get expensive too...
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Old 19th May 2015, 08:13 PM   #10
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Quote:
Originally Posted by gmarsh View Post
Just some thoughts...

- How are you doing battery charging, cell balancing/protection, etc?
- How are you providing waterproofing for the audio/charging inputs?
- Plastic mold design is very expensive, especially what you've got there - I see tons of sliders and at least one overmolding operation. Personally I'd keep this in 3D printed land instead of attempting to go for volume.
- You'll need various industry certifications if you turn this thing into a sellable finished good. Those get expensive too...
Hi Gmarsh,

There are far less parts to it than it seems. I will post the full design details in a few days once I've it's fully rendered internally (just a few details and braces etc to work out now), as it's just far too frustrating to try and and be 'semi-open' with this - May as well do it fully open from the start - or fully closed!

Basically there are two main 'shell' pieces, a grille that snaps on something like the back of a phone case,a rubber part that wraps all around the frame, that could probably be moulded in such a way as to fit a bunch of them in a single piece and break them apart afterwards (the breaks are then covered by another piece) - All the buttons and logo pieces are formed in one continuous piece of cast metal, which, as with the rubber, I'm guessing can be formed as many pieces in one mould, as the breaks are not visible - this then slots inside the rubber piece.

The rubber provides most of the waterproofing and the the necessary 'give' required for the buttons to move.

What part looks like an overmoulding to you?

The charging input is a barrel connector that is waterproof by default and either pressed hard into a taper or possibly glued in place (I don't see much that would call for ever replacing a barrel jack - they're sturdy enough) the audio jack connectors are pressed hard - not glued - against the inner edge with a rubber gasket over the round part and if a non-leaky connector can't be sourced (still looking!) a small blob of glue over the leaky part will fix it well enough.

I haven't gone over all the required industry certs you mentioned yet - Something to consider but I can't see it being a show stopper.

Edit: About the charging/balancing/protection, there is a circuit that accounts for this and it's considered in the design.. I'd need to check over the details as I don't have all the electronics information at the top of my head right now! It's a USB slow charger.

Last edited by Hemisphere; 19th May 2015 at 08:20 PM.
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