I had been looking for a Boombox, but was somewhat disappointed with the specs, expense (for a decent one), and the sound quality. So I decided to build one using a car audio head unit. The main problem using head units in the past has been the current draw, as they require a 12V lead-acid battery. However, LifePO4 batteries have now made this possible. As most vehicles today have in-built stereos, the demand for head units has diminished. Consequently, the small-ads are full of them for very little money. They are actually very good quality units that are available in a variety of formats (cassette, CD, MiniDisc, Mp3), some even have a remote control, and most will end up in a skip (which is a real waste). I managed to buy a Sony cassette unit with a 30 Hz to 18 kHz frequency response and 0.08% W&F for $15. I opened the unit up to clean the heads, and it was basically pristine (many people only used the radio). Moreover, the quality of the mechanism is very impressive. I can only assume they have to be robust to work in a vibratory environment. With regard to the batteries, there are 4 in the bottom of the speakers, giving 12 V and 14 Ah. For the speakers, I used high-quality 4” coaxial units intended for car audio (50 W), with a kevlar main cone and a ¾” soft dome tweeter in the centre. They are particularly suited to boomboxes because they have very wide dispersion. The ‘front’ outputs from the unit drive the speakers, while the ‘rear’ outputs drive headphones via a socket on the side. It should be noted that most of these units have a bridged output (no ground connection), so 4 small capacitors are needed to create a virtual ground (only for the headphones). The case is made from 10 mm ply, with the centre covered in vinyl and the speakers in real wood veneer. The little display on the back is a voltage monitor for the battery. The sound quality is excellent and it can go rather loud! The other good bit about this Boombox is that it only takes 5 min to change the head unit for a different one as it fits all single din units.
That is a nice build which you have put a lot of work into. Sometime in the past when somebody was suggesting something similar I suggested using 3 or 4 cell cordless tool batteries which would come with a charger and monitoring circuits. What circuitry did you use ?
Impressive! I love the custom builds, I used to make my own boomboxes in the 80's when I had a delivery job in a van without a good radio. Mine used a cigarette lighter plug but I always had a blast making a new unit or modifying them. Car stereos were still pretty expensive back then so I never had anything too exciting.
Thanks. The beauty of using a head unit is that all the hard work has been done, all you basically need to do is build the speaker/head unit enclosure. In fact, I am already thinking sheet aluminium and wheels!
What a great use of a car radio! I have a few of my old car radios kicking around, guess I have no excuse not to do something with them now!
If you have a spare pair of small speakers and a 12v wall adapter, you only need to make the central housing and attach the speakers
I've done that very thing in the past to test car radios are working before I've installed them! I have an old Panasonic unit that's ripe for a 'boombox' conversion, when I get my man cave up and running again, that will be one of my first projects.....
Sounds like a plan Emiel. Unfortunately, the era of music I mainly listen to sounds best on cassette, probably because it was mastered to sound good on cassette!
Good job! Love those custom radios. I will one day build my own Discolite type box, bigger and better (I hope).
