Drive In Theater Speakers

[Ahuelsman1]

Looking for help on wiring up some drive in theater speakers that I recently purchased. There is a transformer in the junction box that is supposed to be wired into the speakers. Anyone know how this would be wired?

[PaulHutch]

Welcome to the forum.

It may be a:

Constant-voltage speaker system

Also check out these posts from last year.

Drive-in Movie Speaker

A unusual inquiry I am sure. I am attempting to restore an old drive-in movie speaker. The original inside parts were totally rusted and beyond identification or function. Found a 4" waterproof marine speaker (100 watt) that fits well. I am unable to find a potentiometer with a shaft length that will accommodate a knob when properly mounted inside the casing. It needs to be about 1 inch or 2 cm. I have no idea what ohm rating should be required. My intention is to tie into a vintage Sharp 10 W s…

Drive-In Movie Speaker Restoration

Got great help from Digi-Key sourcing a proper potentiometer with necessary shaft size for drive-in movie speaker I am restoring. Original internal parts were rusted almost beyond recognition. Able to find 4" waterproof speaker for boats that works well. I now have a new problem. Original speaker wire cable has four very small wires that are blue, orange, black, and green plus a ground wire. I have no clue what I am dealing with and how to wire it up. Thinking I should just opt for standard two…

[Kristof_2649]

Hello Ahuelsman1,

Welcome to the community!

If you don’t have an idea where the wires go for that transformer, test the wires resistance with a multimeter.

The two wires that measure higher resistance are your primary and go to your amplifier.

The two wires that measure lower resistance are your secondary and go to your speaker.

If you measure a dead short/very low resistance the winding is damaged.

To better visualize it there is a Drive In Theater restoration company that has a circuit diagram for the Circlite Junction Box that can be found here: Wolf Enterprises - Replacement Drive-in parts

[Ahuelsman1]

Thanks for the reply! I’m having trouble reading there diagram. I’m new to the audio side but I’m a industrial electrician so I have electrical knowledge. What powers the transformer? Did the amp power the transformer then the transformer powered the speakers? Or is the transformer for the downlight? What powered the downlight? If anyone better understand the diagram shown and could draw it out more clearly that would be really helpful. Or if anyone could draw out there own diagram showing how the speakers, transformer, downlight and amp all connect. Thanks

[Ryan_2724]

Hello Ahuelsman1

Please upload photos of the equipment you have, and we may be able to assist although it appears these are products we don’t normally carry.

[Kristof_2649]

Hi Ahuelsman1,

For the transformer the wiring is just two wires to the amplifier, two wires to the speaker, the trick is finding out which wire is which. Is there any indication if a side of the transformer was wired up to the outside amplifier?

Back in the day the amplifier would’ve been a tube amp which has high impedance, the transformer would be used to match the impedance to a lower impedance of the speaker.

If I would doing this project I would work with a cost effective amplifier that is made to drive a small speaker directly and bypass that transformer.

Adafruit makes a 10W per channel audio amplifier that runs off 5-12VDC power and is made to drive a 4Ohm load directly, a speaker, without a transformer
.
Digi-Key PN: 1528-1031-ND
https://www.digikey.com/en/products/detail/adafruit-industries-llc/1752/4990780

[Ahuelsman1]

Thanks for the reply. So they would use the transformers to bump up the wattage going to each each speaker at the speaker? So then they could run a lower wattage amplifier daisy chained to several groups of speakers? Dont plan on using it just trying to better understand what they used them for. And do you sell any low cost amplifiers that run on 120v? Here’s what I’m trying to do. Wanting a way to listen to the radio on these speakers. I have 2 of 4ohm 30watt speakers with the speakers tied into a 50ohm potentiometer. What can I use to power the speakers that i can also use to pick up FM radio stations. That I can plug into a 120v home power outlet.

[Kristof_2649]

The amplifiers we have would be DC powered, they would require an AC/DC converter/wall adapter to be powered and would also require a sound source.

For FM receivers we do not have anything that would be easy to slap into an application.

The best I can advise is checking for a cost effective bookshelf stereo, possibly second hand that has external speaker connections for your application.