Medium size bluetooth speaker box

Warning: long post from a complete noob!

My son is getting into electronics so I thought it would be a fun project for him and I to build a bluetooth speaker together. I have these speakers laying around and want to use them. (Yes, I know they are junk but I am trying to keep this cheap)

We are using a 5.56MM green ammo box i already have. The box is only large enough for 1 6" speaker and the 2 tweeters.

I'm thinking this amp board for the 6" main speaker crossed over to drive the single speaker.

2x100W TPA3116 D2 Dual Channel Digital Audio Amplifier Board 12V-24V For Arduino Sale -

And this amp board to drive the 2 tweeters.

15W TDA7297 Dual-Channel Amplifier Board For Arduino Sale -

For the bluetooth adapter I am thinking of using this.

7-12V Handsfree Bluetooth MP3 Decoder Board With Bluetooth Module+FM Sale -

It gives me a lot of options like using MP3s on a SD card or USB drive, FM radio along with bluetooth and comes with a remote.

The above components that I don't have yet plus things like USB charger, LED lights, FM antenna total about $30 and would like to keep my budget in that range not including the battery. Do you guys think this will work, or am I building a big pile of disappointment for my son and I.

If this project goes well and my son likes it Next I want to build a big one out of a large ammo can with brand name 10" sub, Mids, tweeters, real amplifiers, car stereo with bluetooth and DVD player to hook up to a projector. That one I'm prepared to drop some money on, just using this as a gauge to see his interest.
Thanks in advance for the advice.

Thanks for the reply. I do understand how the crossover works and was planning to wire them in. I should have stated that my biggest question is will those amp boards provide sufficient power for the speakers at 12 volt input from a battery. I know that part of designing a setup is using components sized for each other.
The ammo box seems just a container for all the stuff.
You'll find lots of info and how-to make similar stuff.
The fact is that quality isn't the goal, so you may put whatever you like in a box and expect it to sound. The real target should be put a little higher and it doesn't matter if you use brand names or whatever comes under your hands.
First, you should respect your nature and as ears are positioned on the head the way they are, the speakers should be set in environment in a similar way.
A singular ammo box won't do the trick. Also dual boxes made with thin metal aren't that good. The rule is to dampen materials, and metal exhibits a high speed of sound transmission.
The commercial way has already been established: a singular woofer and a pair of little fullrange speakers, maximising power request on the amplifier to the musical program.
For your project, the effort should be focused on the electronics works with electricity :eek:


2016-03-01 4:10 pm
I should have stated that my biggest question is will those amp boards provide sufficient power for the speakers at 12 volt input from a battery.
The maximum power you can get from a modern solid-state amp depends almost entirely on the battery voltage and the speaker impedance.

The audio chip used in your module operates in bridge mode. With a 12 volt supply, it may be able to manage a maximum peak (AC) voltage of 9 volts or so into the speaker. (Two or three volts will be lost, due to saturation voltages of the internal semiconductors.)

Amazingly enough, the Amazon page for your Pyle speakers doesn't mention their impedance. But 4 ohms is usual for automotive speakers, so let's assume these are 4 ohms.

RMS power is (peak voltage) squared, divided by 2 to convert to RMS, and then divided by speaker impedance.

9 squared = 81; divide by 2, 40.5; divide by 4 ohms, you get 10 watts RMS.

So the estimated power from your amp will be about 10 watts RMS. If you use both the Pyle speakers, 20 watts total, 10 watts into each channel.

Why is the amp advertised at 15W instead of 10 W? Firstly, the manufacturer tests at the maximum voltage you can get from a "12V" lead-acid battery while it is being charged (running car engine, running alternator). That's usually taken as 13.8 volts, instead of 12V. Secondly, they drive the amp well into clipping, until total distortion is an appalling 10%, and then measure power at this point.

I think your general plan is sound, and the thing will work - except for one major piece of the plan, the ammo-case. As picowall suggested, it is hard to imagine a worse loudspeaker enclosure than a thin metal cylindrical can. My suggestion is to re-think that piece of the puzzle.

There are surely other inexpensive solutions to the speaker enclosure problem: a classic cheap-n-dirty solution is to go to the local thrift store and find a small rigid plastic suitcase to use as a speaker enclosure!

Good luck with the project, and I hope it fires up your son's imagination!

One uses a 5 volt bank battery and the other uses a 12 volt LiPo. Both Bluetooth and the ammo unit has an aux. input if'n ya wanna get into it that way..

The ammo box is split in the middle and ported. The 6x9's are stuffed with fiberglass. The amp is in one of the 6x9 enclosures. (The one with the pocket) Simply connect the two boxes together with speaker wire and yer jammin'.. ;)