Rebuilding Classic Drive-in-theater Speakers With the Help of Fusion 360

In 1933, Richard Hollingshead, a man with a vision for a novel cinematic experience, opened the world's first drive-in movie theater in Camden, New Jersey. Seeking a solution to the discomfort of traditional theaters, he designed a space where patrons could watch films from the comfort of their cars. The concept gained rapid popularity, reflecting the growing car culture of the time.

Soon, families were piling into their jalopies, armed with popcorn and surrounded by the sweet aroma of exhaust fumes, ready for a night of film magic under the stars. And so, the drive-in theater became a cherished piece of American nostalgia, proving that sometimes the best way to watch a movie is under the open sky and a trunk full of snacks.

Drive-in theaters became an iconic American pastime, providing an alternative to conventional cinemas. Over the years, they experienced fluctuations in popularity, facing challenges such as the rise of home entertainment systems. Despite these obstacles, drive-ins have endured, preserving a piece of cinematic history and remaining a nostalgic part of American culture. Today there are ~300 drive-in theaters left in the united state. 

Obviously you will need a drive-in theater speaker. You can easily find these on eBay for various prices. The specific one I'm using is the REED Speaker built in CO.

Next you will need to replace the internal speaker. The typical size is a 4" speaker with a low profile.

Then you will need a bluetooth receiver and a small audio amp. Believe it or not, a small 5watt amp will be sufficient for the small 4" speaker.

Finally, you will need a battery to power the amp and bluetooth receiver. Depending on the battery you get, you will also need a power regulator for 5V.

Before we look inside, there sure is a threatening word of caution if you have this speaker. Guess them disappearing from the theater was a big problem.

After opening the speaker up, we find a potentiometer and the 4" speaker. Not much at all in these.

The easiest way to remove the internals is to cut out the old wire. Then the speaker and the potentiometer will be free. And the old cable can go in the trash.

The speaker is a 3ohm. Appears it was built in 1981, which is honestly younger than I thought it would be.

For the REED speakers, there is a small 1.5mm allen key that holds the knob onto the pot. After removing it, there is a 1/2" nut to remove and the pot is free.

At this point we have an empty shell. Now it is time to figure out how to place new electronics in here for bluetooth connection so that we can play a movie or a song once more from the window of our car. Even better if that car is a classic.

Using a 3D scanner, I can get a pretty accurate scan of the speaker case. Sometimes it is difficult to scan metal because the laser beams, or whatever doing the measurement, refract off of it and the scan is impossible. Just spraying some DR. Scholl's foot powder onto the metal object will stop this from happening.

What's really cool about Fusion 360 is that I don't have to start with a blank canvas. I can import my scanned model and accurately build onto it. In this case, I scanned in the top and bottom of the speaker. I can now remove the top or slice the object in half vertically to see the inside and get accurate measurements.

This makes it really easy to see how much room is available for speakers and PCB board component.

Now that I can easily see the model that I'm adding to, it is easy to build standalone components then import them into this view. For example, I took measurements of a 4" speaker online, build the model in Fusion 360. Then imported it into my 3D scan to see if it will fit.

In the first picture we see the model I built for the speaker.

The second picture is where I imported this model into the 3D scanned model.

Finally, I can add the back onto the model, do a sectional analysis of the model with the speaker and then make some measurements.

What is really important about this is that I can see inside the speaker box at multiple angles to ensure the speaker will fit. The last pictures shows that I have very little room to spare from hitting the left ceiling. But, the speaker will fit.

There is a really good article on building an amp from the LM386 driver.

https://www.circuitbasics.com/build-a-great-sounding-audio-amplifier-with-bass-boost-from-the-lm386/

I take no credit for the these attached pictures, they are Scott's.

Like Scott, I tested this on a breadboard with the M18 bluetooth receiver before I made the circuit in EasyEDA.

Now that I have the PCB, I can export it as a 3D file and import it into my model for a test fit. Yes, EasyEDA has a 3D model export option.

Now I can clearly see that this board will fit in the speaker box. And I have enough clearance from the speaker magnet. You can quickly design and test using Fusion 360 and get very accurate results. I really like seeing it visually first.

Now that the board has arrived, I can add all the components onto it.

Finally I can add this new board, speaker, battery, and battery charger back into the case.

Because the old speaker was a bit taller than mine, I have to add a bit of padding on the magnet so that it presses against the grill and doesn't move around. The old speaker was a perfect fit but unfortunately not possible to find them new.

The last steps are attaching the nut on the pot and then adding back on the knob. Now let's test.

Don't be scared to click the video, it is very short and just shows it working.

And yes I hate the voice saying it connected.

Hope you had fun!

If you would like to own one (exactly like in this instructable) you can buy them through Rodz & Bodz in Colorado!

They are $150 each.

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