Magnavox 182BA External Speakers?

[OlConsoleLvr]

I have a 1959 Magnavox Imperial with an original AMP-182BA power amplifier. The 182BA is stereo biamped, with four separate amplifier modules,two for low frequency and two for high frequency with a crossover point of approximately 1200 hz. I would like to hook up a set of external stereo speakers. However, I only see one set of connectors for external speakers labeled H, Cand L (for high, common, and low). Does the 182BA support stereo external speakers, or only a single biamped channel?

 

[grindfix]

I think I have the Magnavox external speaker. IIRC. it has 3 drivers in it. 3 wires, I think. L/C/R. It's at work, I'll dig it out tomorrow and post my findings

 

[cademan]

When a Magnavox console uses a bi amplifier, they are really not meant to add speakers because otherwise you would need four wires (bi wired) instead of two (full range).

You can do it if you know what you are doing. You would need your external speakers to be bi wired and contain separate woofers and tweeters (horns).

Full range single speakers will not work as you would be either connecting to the bass channel or the treble channel. Can't connect a single full range speaker to both.

Got any pics? You say that there is only one speaker connection, L, H, and C. This would be mono. You would need two of these connections for bi amped stereo.

 

[OlConsoleLvr]

Thank you for the information. I understand that the 182BA places the crossover before the amplifier circuits, so all speaker connections, internal and external, are biamped with separate low and high frequency speaker outputs. In my use case, this will work. My question is, why is there only one terminal strip with one set of low and high connections (low and common, high and common)? This would imply a mono or single channel external speaker. When the Imperial's speaker switch is in the "internal and external" position, are the internal speakers summed to create a left channel while the external speaker becomes the right channel (or vice versa)?

 

[frankiebull]

My Imperial from 1959 has a connection on the back of console for external speakers. Here are some pictures and schematics which may help. It also is bi amped but uses a 81-01-00 amp (similar to 182). The speaker selector switch is the only thing that I haven't sorted out yet. I am just using the internal speakers wired directly to the molex plug (upper right corner on schematics) which bypasses the selector switch.

 

[cademan]

Thank you for the information. I understand that the 182BA places the crossover before the amplifier circuits, so all speaker connections, internal and external, are biamped with separate low and high frequency speaker outputs. In my use case, this will work. My question is, why is there only one terminal strip with one set of low and high connections (low and common, high and common)? This would imply a mono or single channel external speaker. When the Imperial's speaker switch is in the "internal and external" position, are the internal speakers summed to create a left channel while the external speaker becomes the right channel (or vice versa)?

Don't know why yours is like this but for true left & right aux bi amp speaker connections, you need to have both like Frankiebulls. Without being there and studying it in person (don't have a schematic in front of me), not sure if your speaker switch puts all speakers in series or parallel. It would have to be parallel if you are on both int. and ext. speakers where the internal speakers are still working.

A lot of times, Magnavox only put a left channel ext speaker connection on their amps. My AMP175 has a left ext speaker screw connector on the amp chassis itself but no right channel ext speaker connection anywhere. My AMP175 amplifier came out of a single console with a black & white television, tuner/preamp, and turntable.

This is because the AMP175 was also used in 2 piece combo's along with single piece consoles. In the 2 piece consoles, the right channel was just a single cabinet with the radio/preamp, turntable and amp and single speaker, and the left cabinet was just a single speaker.

Magnavox had soooo many different combinations in the early 50's and 60's.

 

[gadget73]

My 197 had a somewhat odd setup for external speaker connections. One speaker was hard-wired to the amp, long set of leads came right out of the chassis. The other speaker used spade terminals to connect to C and 2 on the terminal strip on the back, but there is also a 1 terminal. You could hook up 2 external speakers but only unhook one in the console. No idea why they did it that way but it let me be real lazy about speaker terminals and simply leave the stock 3 terminal strip on the side. It goes along with my no-effort no-money theme on that amp. Other than the output transformers, which were the cheapest things I could find, every single part is either recycled or something I already had. Even the base is made from a piece broken off a pallet at work and cut to size on a trash-picked saw. The feet are just 1 inch squares of the same wood.

 

[OlConsoleLvr]

Here is a picture of my 182BA. The red circles show the main speaker outputs. The lower left is a spaded terminal strip, while the one on the right are wires coming out of the chassis. The only external speaker connection I can find is the terminal strip circled in blue. Very similar configuration to what Gadget73 described for his 197. So how would one connect external left and right stereo speakers?

 

[gadget73]

in stock form, you wouldn't. Could modifiy it but this wouldn't have been intended to connect 2 external speakers.

 

[OlConsoleLvr]

Thanks, Gadget73. So what happens when the speaker switch is in the "INT + EXT" position with a stereo source (Phono)? Are the internal speakers summed to mono left channel and the external speaker is the right channel? Or is the external speaker mono only, like when placing the external speaker in another room?

 

[gadget73]

possibly a bad assumption, but probably the internal speakers do not sum and it remains L and R, plus whichever side the external speaker is connected to. The external wouldn't be mono but there may be a stereo/mono switch that would flip all 3 speakers to mono mode.

 

[OlConsoleLvr]

Thanks, everyone. This design won't fit my use case, but that's the "beauty" of these late-50s early stereo units.

 

[grindfix]

Probably not going to help OP but I dug out the external speaker I promised to look at a couple of days ago. I didn't have time to open it but it looks like it only has 2 drivers in it and 3-wire cable. L-COM-R. It's possible there are tweeters in front of the larger drivers. I've seen that done that way in some consoles