Mini speaker for backpacking

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clengman

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Joined 2011
#1
So, I've been poking around here for a few weeks. I started out because I had a pair of old bookshelf speakers and wanted to make a little amp to run them as better quality computer speakers in my office. I have a 3116 amp ordered and on its way. Looking forward to finishing that little project, but the more I read the more I'm interested in trying other little projects. Specifically, I'd like to build a few portable, battery-powered, speakers. One moderately-sized boombox to use on the back porch or for picnics. One mono speaker, a little smaller to keep with camping gear for car camping trips and one teeny tiny speaker to take backpacking.

I'm working through plans for the mini speaker now and I'm wondering if I'm on the right track. I'd like to use a Dayton ND65 as the driver. Using winISD, it looked like a ported box of about 45 c.i. (about 3"Hx6"Wx2.5"D) tuned to somewhere between 70-80 Hz would work okay. I'll add a separate compartment above the speaker enclosure for the amp and battery. Planning to build it with 1/4" birch plywood "hobby panels."

Amp will probably be the tiny little TPA3110 mono board that's available on ebay, and battery will be a 3000mAh Li ion cctv battery (with charger on amazon).

One question I have regards material choice for ports. Looking at the port parameters in winISD, I could use 3 x 1/4" ports each somewhere around 2.5-3" long (depending on the exact box volume I end up using). Using larger diameter port tubing I start to get into a situation where the recommended lengths are too long for the box and/or the vent mach is too high. I have a lot of 1/4" I.D. tygon tubing readily available. Would that be a suitable material to use or is it important to have straight and rigid port tubing? Should I buy maybe some 1/4" copper tubing instead? or 1/4" PEX since it's a little more rigid than tygon?

I realize that this is not going to be hifi in any way shape or form, and perhaps many of you will think that it's a waste of time and money to build something like this when there are fairly inexpensive, small, battery-powered bluetooth speakers that are commonly available. I'm thinking of it more as an exercise in design, material selection, and construction though, than as being an absolutely practical thing to do. It's a way to get my feet wet trying out all aspects of the process with out a big outlay in materials cost and I'll be able to do most of the construction easily with handtools.

So what do you think? Am I missing anything major in my design? Anything that I could improve on? Thanks!
 
#2
Sounds like you're catchin' the disease.. 😉

What ever you choose to do, don't let anyone discourage you. The fun is in the design and construction and you'll reap the harvest, even if it's good or bad..

I build all kinds of funky junk and I have a ball! Can't find a whole lot of interest sometimes but I just keep on playin'..

It seems that you have a plan. Do the book shelf speakers and see how you like it. I've done a bunch of them myself. Some turn out good, others suk! BUT, with a little tweakin', a piece of crap can be made to sound very good. That's the fun of playin' and learnin'..

I might help you with the moderately sized portable Bluetooth Boom Box, being that I've built and sold a few. I don't mess with ports much, being I like sealed enclosures better..

I'm a cheapskate myself. Always tryin' to make a purse out of a sows ear. That will never change..

Have fun!
 
#7
The word is tiny 😱

I don't think that OP errrr... Clengman - would find it interesting when using such a normal loudspeaker. I mean, the fun starts at 3 W and you don't have no more Watts. TPA3110 with 15 W seems a better suit.
Working with double channels as in stereo it would make some noise.
For mono, you ( Op, Clengman..:! ) could use a better speaker arrangement such a 6 " for bass and a tweeter, or a fullrange as you wish ( FAST arrangement ). Or make a "normal" stereo amplifier and use one channel for bass and one for mid treble ( just parallel / joint the inputs and use Caps& Coils for filtering after the amplifier )
🙂
 
#8
OffGrid - Thanks. Very Cool!

pico - For the bigger builds I'm thinking about, I definitely want more than 3w per channel, but for a speaker to take backpacking, that really might be a good option. I'm thinking a major advantage will be a 5V battery instead of 12V. However, with a small driver and low power, I'm wondering if it won't just end up sounding about like the onboard speaker on my phone. I have a pair of very small battery powered speakers that I have used in the past on backpacking trips, but I can say honestly that while the external speakers are a little louder, my phone by itself sounds better.

Also want to learn more about your suggestions for 2-way setups. I don't know what FAST is. I've seen the acronym here before, but I have yet to look it up. I really haven't read up much on 2 way at all. I've been focusing on full range drivers for simplicity's sake. I'll have to learn more before I decide on parts for the larger speakers I'd like to build.

For my backpacking speaker, I'm hoping to put together a complete, powered, mono speaker that will be smaller than an average 6" driver (battery and amp included); thus the choice of the 2.5" full range driver. I don't think I'm going two way for this particular project. Thanks for the ideas!
 
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#9
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#10
OffGridKindaGuy said:
I ordered some of these to play with. They would run for a long time on a 12 volt 6.8 aHr. LiPo battery..

Lowest Price 12V Mini Hi Fi PAM8610 Audio Stereo Amplifier Board 2X10W Dual Channel D Class Hot Sale-in Other Electronic Components from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

Rechargeable Lithium ion power supply battery backup cctv 12v 6.8A YSD 12680-in Cables and Connectors from Security & Protection on Aliexpress.com | Alibaba Group
Click to expand...

I think that's really similar to what I'm planning to use. The same batteries are available from amazon. I was planning to get the 3Ah version because it'll fit better in the box I'm planning to build. I've read that the listed capacity is... well... a lie and the actual capacity will be more like 2Ah.

The TPA3110 (based on posted specs and a little bit of guesstimating) should make around 10W clean watts (very rough guess) into an 8 ohm load at 12V in bridged mono mode. The figures (10%THD+N) from the datasheet are 10W/channel for 8ohm load at 13V and 30W/channel for 4ohm load at 16V.

So at the max nice-sounding volume I would probably run the battery out in 1-2 hours. I think that's the weak point in my design right now, though I doubt I'll be running it anywhere close to max volume on family backpacking trips.

I think I might get the amp and the speaker first, plug them into the wall, and try to test the current draw under different conditions and see if that particular "3Ah" cheapo battery is likely to provide enough capacity for a weekend backpacking trip. If not I'll look at increasing the box size to fit a bigger battery.

I'm still hoping for input about the choice of material for vents. I think I definitely want bass reflex on this because I want to use a small driver and to extend the low end as much as possible. That's also why I chose the ND65. It's tuned low (77Hz) and has a small QTS (0.41) for a driver of this size. It's got a huge xmax as well (3.5mm). I thought that made it an ideal full range for a very small vented box. I'm interested to know if the choice of vent material makes much of a difference. Is rigid better. Is thin-walled tubing better? Also wondering if the vents have to be straight... Will it work if I put a single piece of coiled tygon or PEX of the proper length and diameter for the tuning I want? A french horn is certainly not straight?
 
#11
Quote.. Clengman..
" I'm wondering if it won't just end up sounding about like the onboard speaker on my phone."

I can promise you.. NO.. With the right driver(s)

Don't underestimate these little guys. It's possible to get 90+db out of them with enough bass that can be felt in a table several feet away. Very impressive from a 5 volt bank battery that will last for a couple of days..
 
#14
Found another 5 volt gem. Stable down to 2 ohms and produce 5 watts/channel. I got some on the slow boat.. 😉

mini PAM8406 digital amplifier board module with 1000UF filter capacitor power over PAM8403 TDA2822 LM386 -in Other Consumer Electronics from Consumer Electronics on Aliexpress.com | Alibaba Group

Quote.. Me! In post #2..
"What ever you choose to do, don't let anyone discourage you. The fun is in the design and construction and you'll reap the harvest, even if it's good or bad.."

Move forward. I'll have fun with ya.. 🙂
 
#15
Have you seen any of these 5v amps that work in btl mono?

Ever tried running one with a 3.6v li-ion cell?

Something the size of one of those pam8403 boards and a 2600mAh 3.6v battery would be a significant weight and size reduction compared to a tpa31xx amp and requisite batteries.
 
#18
clengman:

I don't mean any ill will, but as someone who has spent his share of time wandering in the woods I find the idea of a backpack speaker system to be troubling. The last thing I want to hear when hiking is someone else's music, no matter how quietly it may be playing. Part of the beauty of the woods is the isolation and part of the beauty are the sounds (or the whispering silence) one cannot hear anywhere else, both of which would ruined by the gentling purring of someone else's Def Leppard or Mozart. Sometimes, the fact we can build something doesn't mean that we should build that thing.

Why not focus on something that could require earbuds or headphones?

Regards,
Scott
 
#19
Where do you go camping? I've never. I mean never. been backpacking and camped within earshot of another human. You need to find some better woods.

And troubling??? It's troubling that I might want to listen to some music with my family while we're setting camp and making dinner? I think you should find better things to worry about.
 
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