Back Woofer


Introduction: Back Woofer

How to create a simple amplifier from scavenged car stereo parts to put sound into a backpack

Step 1:

I didn’t want to spend a lot of money on parts, so budget wise most my parts were scavenged from a car stereo a friend was going to throw into the trash. I made this so I could have a more portable and convenient boom-box type back pack.

Like this scavenged TDA1558Q from that stereo. (On the heat sink)

I did something like this before by taking the set up out of a gaming chair with the speakers, inputs, and volume control, that was nice but it didn’t have the bass that I really wanted from a portable stereo. My improved version has the bass that I was looking for and has the volume control from the audio input device (i.e. Mp3, ipod, iphone, etc.).

Step 2:

Here are the components that I used:
• TDA1558Q (x1)
• 1k Resistor (x1)
• Red L.E.D. (x1)
• .1 uf Capacitor (x2)
• 2200 uf 50 V Capacitor (x1)
• RCA/Headphone cable (x1)
• Suitable Heat sink (Medium sized) (x1)
• Band-pass Filter
           22 ohm 5 Watt Resistor (x1)
           68 uf 35 V Capacitor (x1)
• Enclosure (x1)
• Wire
• Solder
• Proto board
• 4 ohm speakers (x2)
• 12 V Battery pack (x1)
• Suitable (durable) backpack (x1)

Tools that I used:
• Solder iron
• Drill
• Wire strippers/cutters
• Assorted drill bits
• Screwdrivers (for mounting into enclosure)

Step 3:

The TDA1558 puts out about 22 watts into 2 channels. It worked for the 6 inch woofer that I used, and it handled a mid range or tweeter as well. I incorporated a simple band-pass filter using one resistor and one capacitor for the low channel. The mid range or tweeter was un-filtered on the remaining channel.

Step 4: Schematic

This is my schematic:

Step 5:

The band pass filter was quite simple; it is used to filter out the higher frequencies to get mostly the low frequencies for the woofer. I looked up “band pass filter calculators” on the internet’s and used the closest valued components that I had. The resistor (22 ohm) and capacitor (68 uf) form a RC network that got me close to my bass goal.

This is the "Band Pass Filter" (The orange and tan components): 

Step 6:

When I finished my amplifier I hooked it up to speakers and incorporated it into a backpack for easier transportation. I first put my finished amp into an enclosure and then put 2 screws through it and into a speaker enclosure (with the speaker connected). I then put the speaker enclosure (with the amp now connected and secure) and a 12 volt battery pack, into a back pack style baseball bag that I had. I didn’t secure the speaker to the bag because I didn’t want to put holes in it and it sat in there fairly secure by itself.  I then ran the unfiltered audio outputs up to the top of the bag and into a tweeter.

Sadly the bag is now being used for another purpose currently so i do not have pictures of this instructable in its finished form.

Step 7:

Here is some pictures of the finished amplifier:

Step 8:

Pictures Cont.

Please feel free to comment with feedback, suggestions, or questions



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    5 Discussions

    How to connect bass, treble and vol knob on this project?

    Cool man. How u find it.
    can you prepare the same is but with bass, treble and vol knob connected.

    I'm glad you asked, it actually sounds really well, better than you would originally expect, i will soon find a way to add a video or a link to a video so you can hear it, thank you for bringing that to my attention