Vintage booster/ equalizer

Deano

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I found a bit of Sparkomatic nostalgia for myself and I've noticed that the input from the stereo has only positive lugs, no negatives. Would I connect all left negative wires to the desired left negative output posts and all right negatives to the desired right negative posts?

The old booster I had had the same layout, but had one negative post under the two positive left and right input posts.

Can anyone help or am I barking up the wrong forum?

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Hayzoos

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Early radios had only positive outputs to the speakers. The speaker negatives were all tied to ground. You cannot just connect all the radio negatives together on radios with a positive and negative for each speaker, it will damage the radio. The changeover occurred starting in the mid to late seventies. To put a newer radio in an older car requires un-grounding the speakers negatives and providing a speaker negative wire back to the radio. There used to be adapters which used transformers that had positives and negatives for each output from the radio and only a positive for each speaker and a single ground with no power. That type of adapter is what you would need.

Another thing that matters is impedance matching. Most car speakers were either 8 ohm or 4 ohm. If your speakers were 8 ohm then your radio or amplifier should be 8 ohm as well. For low power levels it is not critical for an exact match. But an exact match allows the most power at any volume to reach the speaker. In some cases of severely mismatched impedance, blown speakers or fried amplifiers are the result even if the sound was not loud, but the volume had to be turned way up to hear well.

There is a specific type of transformer called an impedance matching transformer. Let's say your radio is 4 ohm output but your speakers or booster amp/eq is 8 ohm input. you need a 4/8 ohm matching transformer able to handle the max wattage of the radio. Then if the booster/eq has 8 ohm, but your speakers matched your radio, then you need another set of 4/8 ohm transformers to match the speakers to the booster/eq and they have to be rated for the max wattage of the booster.

If the impedance matches, then all you need are 1:1 transformers rated for the max wattage to connect the booster/eq. that's what those adapters used. In no case do you tie any outputs together, it will likely damage the radio. If the radio has LF,RF,LR,RR outputs, then only hook up the LF and RF to the booster and leave the LR and RR disconnected and taped off.

On a side note, some amps and radios cheated on the impedance and designed 6 ohms outputs "close enough" to either 4 or 8 ohm to work. They also tended to boast ratings like 1,000 watts per channel yet cost less than half of a quality radio properly rated at only 100 watts per channel.
 

Deano

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Thank you for such a detailed answer. I appreciate it.

I have a Pioneer Media Player (no cd player) and Kicker 6x9"s in the package tray. I ran new speaker wires. None of the factory wiring was used.

A friend from work told me that I should be able to run the negative wires from the stereo to the output negative posts on the booster. Well, I tried that and it sounded like SHIT.

How would I go about using this older booster with my new stuff?
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Hayzoos

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I would not combine a Sparkomatic booster/EQ with those components. If you want the nostalgia, mount the Sparkomatic, connect the power and nothing else, just there for looks and lights.

I know what it would take to connect it and how to do it. I do not know availability or cost of the components. Unless a pre-built adapter is still available (probably not), it will require quite a few connections, possibly soldering, mounting pieces in an enclosure, etc. Not worth the effort, it will probably sound worse than if you just connect that radio to those speakers.
 

80mirada

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Honestly, the old stuff is super cool looking, but even the best components from that era are pretty lacking in capabilities. There were some cool tutorials on YouTube a few years back (way more than a few) that showed how to make many of the old audio units look like they were working, but not.
 

Deano

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Well, shit. Some things (not our Mopars) are better left in the past, huh?
 

Hayzoos

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You got that right. There are things that do not get better with age, just in our memories.
 

Deano

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I've decided to go with a 500w Pioneer, 60w rms, 2 channel amp. I'd rather mount it in the trunk, not under the seat, but I don't want to have to run screws through the sheet metal. Is there some way to mount it under the package tray?

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kkritsilas

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Mount the amp to a sheet of plywood. Then mount the plywood (complete with any wiring, connectors, fuses, etc.) as a unit to the parcel shelf, or to the frame that runs behind the rear seats. Mounting it on the parcel shelf (it would be upside down, unless you get real fancy) can result in heat issues, because the heat from the amplifier will rise, and being mounted upside down, will heat the amp up even more. Again, you can get fancy with a sealed enclosure and fans, but it is often easier/simpler to mount it on the frame behind the back seat.
 
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