Portable battery powered full range speaker build.

[archiebald98]

Hi I'm new to this forum. I am currently studying an engineering extended diploma in the UK. Part of my course requires me to design and build a project.

I have been wanting to build my own speaker for a while and thought this was the perfect opportunity. My initial plan was a 3 way system but I am now leaning towards a single full range driver. This driver from Tangband is one of the drivers that have caught my eye. Tang Band W5-1611SAF 5" Full Range Speaker. I plan to power my system from a removable 12v lipo and also have it so that it can be powered from an external battery such as a car battery. It will also be able to be powered from the mains.

I would be very interested in hearing advice from those more experienced than myself. In particular I am struggling to find a good quality small amplifier or amplifier board that is capable of outputting enough power, at a suitable quality, for the relatively high quality driver.

I would also be very keen to hear from any of you who think they may be able to offer advice about any part of this project.

Sorry for the long (and formal) post but I didn't want to miss anything and this post may be useful to include as evidence for my final project portfolio.

Thanks in advance!!

 

[mikejennens]

Since you'll be looking to have the option of sunning it off a car battery, a Lepai amp might work well. Many run off 12 VDC.

Lepai In Stock At Parts Express With Free Shipping

The same can be said form Topping amps

Topping In Stock At Parts Express With Free Shipping

And then Dayton Audio has some nice offerings.

Dayton Audio DTA-2 Class T Digital Audio Amplifier Module

Since the speaker is rated at 90db@1W/1m, you don't need tons of power. I'm not sure what you have available in the UK (I'm assuming, judging by the flag by your name). There are A LOT of kits available, just about anywhere. I would recommend staying with a 12 VDC powered amp though.

Mike

 

[perceval]

Look for those little class D amps, the ones in the 50W range offer plenty of power for your application.

I have a set that I bring to the beach every weekend, powered by a car battery.

 

[Gnobuddy]

This driver from Tangband is one of the drivers that have caught my eye. Tang Band W5-1611SAF 5" Full Range Speaker.

Tang Band makes nice - but expensive - speakers. If things go wrong with the electronics (or the wiring of it), that expensive speaker may be fried. My personal inclination would be to use a less expensive speaker for a first project . If it works the way you want with the cheapo, you can always use the fancy speaker later. What do you think?

I plan to power my system from a removable 12v lipo and also have it so that it can be powered from an external battery such as a car battery.

There are two potential issues worth discussing here.

Issue #1: 12 volts is quite a low supply voltage for a power amp. The peak-to-peak output voltage of the Lepai (and similar design) amp will be restricted to a maximum value that's at least a couple of volts less than the power supply voltage (because of saturation voltage losses in the output transistors).

With about 10 volts peak-to-peak, absolute maximum, the amp can only deliver about 1.5 watts RMS power into an 8 ohm speaker, or about 3 watts RMS into a 4 ohm speaker. That's not very much, and may not be enough to satisfy you.

These days, there are a lot of amps that use a slightly different approach; the "amp" is actually two separate amps, driven in bridge mode (two outputs out of phase by 180 degrees). The speaker is floated between the two outputs.

This effectively doubles the voltage excursion across the speaker, quadrupling the output power. So you can now get about 6 watts RMS into an 8 ohm speaker, or 12 watts into a 4 ohm speaker.

My suggestion is to go this route. Unless you like your music very quiet, I think you're more likely to be happy with up to 12 or so watts on tap.

As a point of reference, I have the little Lepai amp, running on a 12 volt wall-wart. It works well to drive computer speakers on my desk, a couple of feet from my head (and therefore, my ears.) But when I briefly used it with a 27" computer monitor as a bedroom TV set, it would clip audibly on bass sounds even at quite moderate volume. The amp was paired with thrift-store four-ohm boom box speakers.)

Issue #2: You mentioned Lipo batteries. Please be aware that these things are electrically (and physically) quite fragile, and they have a very unpleasant tendency to burst into extremely high-temperature flames when things go wrong.

Some things that can trigger very hot flames and a spew of toxic chemicals include the following: over-charging, over-discharging followed by normal charging, charging too fast, physical impact (such as dropping the lipo), ambient temperatures that are too high (such as the inside of a car parked outdoors in bright sun), rupture of the lipo cells (contact with a sharp object), et cetera, et cetera.

Lipo packs are used in many commercial devices now - phones, tablets, and laptops among them. Large electronics manufacturers go to a great deal of trouble to keep their Lipo packs from incinerating themselves, and injuring their owners; even so, there are many notable failures, as witnessed by the many cases of lipo fires in cellphones we've seen during the last decade or so. I remember Apple iPhone fires, Sony cellphone fires, and right now, Samsung is in dire straits with their Note 7 lipo fires.

So I am very leery of the idea of using lipo batteries in a portable, home-made device. To keep the thing from catching fire, potentially injuring you/ your family/ your pets, or burning down your car/ house / garage, you'll have to have at least as much protective circuitry as the big boys do; that means electronics to prevent over-discharge if the amp is accidentally left on too long, electronics to balance the individual cell voltages in the pack, electronics to charge the pack in precisely the correct regimen (constant current at low charge states, constant voltage at high), et cetera.

You'll also have to ensure your portable speaker never sits in too hot an environment, that it's never dropped with the lipo installed, that nothing accidentally bumps or pokes the lipo, et cetera.

And if you do all of this correctly, you may still have a Lipo fire on your hands - there is no way to be 100% safe with these wonderful, but fragile, batteries.

I will add that for years I flew electric RC model aircraft, powered by lipo packs. During that time, I saw THREE of my friends have their vehicles destroyed by lipo fires that started while they were re-charging their battery packs inside their vehicles. Two of the vehicles (a Ford Explorer, and a Ford minivan) were totalled. The third (a Toyota pickup truck) was severely damaged - burned from carpet to headliner inside the passenger compartment, and stinking of mysterious chemical smells. The owner continued to drive it like this, though.

I never experienced a Lipo fire myself, but at least part of the reason for that was that I treated the things like loaded guns. I followed a large number of safety precautions, including transporting packs inside a small fire-proof home safe, with a Ziploc bag full of sand placed on top (to smother the flames in the event of ignition.) Several times I discarded packs that had begun to puff, or show other early signs of internal damage. I never, ever, charged packs inside my house, or inside my car, instead charging them in a cement breeze-block, placed on a concrete paving stone, with a Ziplock bag of sand on top, outside in my back yard.

Google "lipo fire" and look at the results yourself, before you make up your mind whether I was being crazily paranoid or not.

So my suggestion is to scrap the lipo idea, and consider a safer cell chemistry instead. LiFePO4 cells are a lot safer, and these are the type you find in most cordless tools sold as having a "lithium battery". Even so, you MUST use a proper charger specifically designed to charge LiFePO4 cells, and it must be set to provide the correct charge current and termination voltage for the pack you have. (Too much voltage and/or current during charging is a huge no-no.)

There you have it, my three initial suggestions: find a bridge-mode amp module, avoid Lipo chemistry, and consider doing at least initial testing using a less expensive speaker.

Good luck!

-Gnobuddy

 

[perceval]

For battery, I run with one of those portable jump starter, they have a 12v cigarette socket, and RCA plug for charging or power, and a USB port. Plus, handy if someone has forgotten their lights all day on the car!

For amp, I use a small TPA3116D2 50W x2 board, running on the 12V portable battery.

It's driving a pair of TABAQs outside, and even a 300W pair of Yamaha PA speakers. Loud enough for a party at the beach!

It's not as portable as an all integrated boombox, but I get a lot more sound.

 

[Gnobuddy]

For amp, I use a small TPA3116D2 50W x2 board, running on the 12V portable battery.

Looks like a good choice - it's bridge-mode, and puts out about 12 watts RMS on a 12 volt supply, just as I said in my previous post.

An portion of the TPA3116D2 datasheet is attached. You can see the distortion remains flat, and tolerably low, until about 12W or so; above that, the curve starts to climb almost vertically, as the amp starts to clip like crazy, and distortion goes through the roof.

-Gnobuddy

 

[Gnobuddy]

I forgot to add the link to the online datasheet: TPA3116D2 | Analog Input Amplifiers | Mid-Power Audio Amplifiers (5-50W) | Online datasheet

-Gnobuddy

 

[archiebald98]

Thank you very much for all of your replies. The reason I initially thought of running lipos is because I already have some and a balance charger for my old rc car. I have also considered using drill batteries. I would like to have the option of the boombox being portable rather than always having to lug around a jump starter or car battery. However when running it off the small batteries I do not mind sacrificing some power. I am planning on running it off the mains fairly frequently anyway.

As with blowing the speaker I will initially build this project with cheap test drivers which I already have, before swapping them out for the proper ones.

One idea I have come up with to address the lack of power would be to have 2 batteries powering 2 amps with 2 smaller full range drivers, all with one input and in one housing.

Does anyone think there are better options of driver available than the tang band for a project like this? The range available the uk is pathetic compared to America (parts express) but I have come across a brand called monacor that are available at a good price here.

 

[Jerms]

Monacor or Visaton or Omnes Audio. Their 3.01 or 3.AL look interesting.
Certain MCM "Audio Select" drivers available from CPC/Farnell.

A lot of stuff available internationally on eBay. Even Partexpress. At first sight their shipping is crippling but it doesn't go up appreciably when adding other items.... At least, within weight/size limits.

 

[Konzentr8]

Another very cheap option ... Parts Express and some companies selling on Amazon ( Reckhorn for one ) are selling rebadged versions of the old Sonic Impact amps which can be run 12 v or from AA batteries . They use a Tripath 2024 chip , not much power but with an efficient speaker possibly worth consideration for your project ?