Magnavox D-8443. Upgrading speakers with stock amp

[Despotes]

I had an 8443 in high school (80's) and loved it 'til the tape deck crapped out then sold it. I recently saw one on E-Bay and it brought back memories. Ordered.
At minimum I want to replace the speakers including the tweeters, but still use the stock amp (No clue about wiring in new amp-lol)
I know I'll need very sensitive 4 ohm speakers for this project. At least 90 dB? The tweeter hole will need to be drilled out and I'll have to make a little bracket/housing.
What drivers and size do you recommend that will fit for the two full range mids? Should I even bother replacing the center driver if using the stock amp?
I'm also thinking of using the PartsExpress foam baffles to help improve the sound since there's no isolation between the drivers.

 

[Reli]

The easiest route would be to forget about the factory tweeters and just install 2-way coaxial car speakers. That would take care of your mids and highs. As for the center speaker, it's 8 inches right? Be a little harder to find a good replacement, unless you used one from another vintage boombox, like a Lasonic or Helix.

You could definitely improve the sound of these things, but the amp doesn't have enough juice to make "monster" bass no matter what kind of speakers you use.

 

[Despotes]

Thanks for the info Reli. Yes, 8"
I do have a Helix 4636 that still works. Both tape decks too! I'll have to tear it apart and see if one of the speakers fits the Magnavox center. I'm not looking for monster bass, just an improvement in sound quality. Still undecided between coaxials and component car speakers.

 

[baddboybill]

Just make sure the ohms on speakers match.

 

[Despotes]

I just installed a pair of Polk DB522 speakers. Fit perfect and it sounds A LOT better. Good looking too.
I can't find a replacement for the 8" woofer. The magnets would make contact with the larger pcb. About 3" or under magnet would work.

 

[Reli]

Is the woofer still connected to power?

If not, maybe change it to a passive radiator and seal off some of the vents.

 

[Despotes]

Still connected. I thought about that, but unsure if it would be an improvement.
I did seal everything off before replacing the speakers and it killed the bass.
Hard to see the speakers with the flash bringing out the blemishes in the grill.
My ON /Off button is funky. When OFF there's a random humming sound. When ON, the radio (every station) often has distortion sounding static only in the left speaker until I press the On/Off a few times then it goes away. Dirty switch?

 

[jimmyjimmy19702010]

Sealing off the cabinet will kill the bass as you'll be missing out on the low frequencies that leak out of the rear case vents. There won't be enough volume of air inside the cabinet to allow all of those speakers to produce bass. So basically you'll end up with an undersized sealed cabinet - not good.

 

[Despotes]

I decided to get a cheap 6 1/2" woofer https://www.parts-express.com/6-1-2-poly-cone-midbass-woofer-4-ohm--299-609
and an ABS plastic sheet to make an adapter. I'll give it a try and see how it does. It's cheap so no loss if it doesn't work well.
I touched up the grill. Looks a bit better.

 

[Despotes]

The power switch is now working correctly--for some reason, but the volume pot is the culprit for the occasional loss of the left channel. I have to flick up the volume real quick a few times and it comes back. Cleaned with Deoxit multiple times, but symptoms continue. Strange how the volume pot is affecting only one channel.
Do I need to replace the pot or is there something else going on?

 

[Line Out]

The pot has dual sliding assemblies, because it's a stereo potentiometer. Very normal behavior. There is probably worse oxidation on the other "channel" or even a damage on the sliding surface. Some times a pot would need to be disassembled and the oxidation removed manually. A solvent is not always enough.

The 6,5" may not be the best bet, because sensitivity is rated at 88.3 dB 2.83V/1m. For any boombox, I wouldn't look at speakers under 90dB, or maybe 91-92. Why, you may ask. Because a 3dB volume increase needs 2 times the power from an amplifier.

So if there is two speakers,
1: 88dB 2.83V/1m
2: 91dB 2.83V/1m
You would need 16 watts to break 100dB with the 88dB model and only 8 watts with the 91dB. Further, 32W @ 103dB or 16W @ 103dB.

It may be ok for easy listening but the difference will be noticeable at high levels. Doubling the loudness is roughly 10dB (how human perceives it).

Nowadays it may be a struggle to find a high sensitivity speaker to fit in a boombox, because todays power amps have plenty of muscle and the demand for "un" -enclosured speakers is very low.