Panasonic RE-7750 - New Speaker Help Needed

[EndoFury]

Hi everyone. Someone very close to me in his 70s is fond of quadraphonic tunes and uses an old Panasonic RE-7750 receiver with an Akai 8 track player. He uses the original speakers that came with the Panasonic and they only have one crappy speaker in them, so I want to get him a nice set of 4 better bookshelf speakers with a 6.5" speaker and tweeter in them.

The issue is that the receiver and original speakers are 16 ohm. What am I in for if I hook up a set of 8 ohm speakers to it?

 

[DuncanS]

I couldn't find any data on the Panasonic RE-7750 so halving the load impedance to 8 from 16-Ohms increases the current drawn from the Amp and as a result there is a good chance it could blow an internal output fuse, or worse the output stages. That said speakers quote an average impedance so at lower or higher frequencies the impedance changes and can go quite low. See if your friend still has the manual, quite often they will state 4-16 Ohms or 4-8 etc. 16-Ohm impedance speakers aren't that common anymore.

 

[EndoFury]

Thank you. I couldn't find much either other than a page that said each speaker gets 10w and you can hook up 4x16ohm speakers. There's not much out there about this since the receiver is almost 50 years old. I did read one article that suggested that it would only be an issue at high volume. However, if I'm not mistaken, 8ohm speakers would sound more powerful, so you might not need to turn the volume up very much. Considering that, I wonder if they would distort from having only 10w before they'd be too loud to blow the amp. Your thoughts? I don't think he has the manual, but I'll check.

Edit: Well, I found the manual online and the page about using other speakers says to use 16ohm. That pretty much rules out any modern speakers. He did say he's willing to try it. He has a spare unit if it blows and if it blows I could get him a 5.1 receiver with analog inputs and use multimode with the new speakers too.

 

[LuvMyQuad]

Couldn't you put an 8 ohm high wattage resistor in series with a typical 8 ohm speaker to yield a 16 ohm load to the amp?

 

[~dave~~wave~]

There's a listing on amazon for the receiver with lots of photos here: https://www.amazon.com/VINTAGE-PANASONIC-RE-7750A-QUAD-RECEIVER/dp/B01N7SNBC7

If the speakers aren't blown and still sound like they did 50 years ago, I would let sleeping dogs lie.
Keep the system intact.

You can't hear what his aging ears do.
Most of us old guys have lost a lot of high frequency perception.
Probably not much high frequency from the 8-track anyway, even with new speakers.

It's interesting how 50-year-old music was mixed for the midrange frequencies small crappy speakers deliver well at low volume.
I was in the grocery store yesterday, Canned Heat On The Road Again was playing on ceiling speakers, it sounded great.
Didn't need sub-bass and hi-freq overtones on the cymbals, all the necessary info was there.

If it was me, it would be a new home theater system or nothing.

 

[EndoFury]

Couldn't you put an 8 ohm high wattage resistor in series with a typical 8 ohm speaker to yield a 16 ohm load to the amp?

This is beyond my understanding. I'm not sure what in series means. Do I buy 4 gadgets that go on the speaker to convert them to 16ohm?

 

[~dave~~wave~]

Couldn't you put an 8 ohm high wattage resistor in series with a typical 8 ohm speaker to yield a 16 ohm load to the amp?

Maybe, then you'd be pissing away five watts as heat and have five watts left to power a hi-fi speaker.

 

[EndoFury]

There's a listing on amazon for the receiver with lots of photos here: https://www.amazon.com/VINTAGE-PANASONIC-RE-7750A-QUAD-RECEIVER/dp/B01N7SNBC7

If the speakers aren't blown and still sound like they did 50 years ago, I would let sleeping dogs lie.
Keep the system intact.

You can't hear what his aging ears do.
Most of us old guys have lost a lot of high frequency perception.
Probably not much high frequency from the 8-track anyway, even with new speakers.

It's interesting how 50-year-old music was mixed for the midrange frequencies small crappy speakers deliver well at low volume.
I was in the grocery store yesterday, Canned Heat On The Road Again was playing on ceiling speakers, it sounded great.
Didn't need sub-bass and hi-freq overtones on the cymbals, all the necessary info was there.

If it was me, it would be a new home theater system or nothing.

I've thought about that. He always wants me to be impressed with the system when he plays it, but it just sounds flat to me. You're saying it's the tape, not the speakers?

 

[Hamilton59]

Couldn't you put an 8 ohm high wattage resistor in series with a typical 8 ohm speaker to yield a 16 ohm load to the amp?

You could but that would cut the output to the speaker by half as well... and that's resistance, not impedance a little different. You could put two speakers in series and truly have 16 ohms per channel.

 

[Hamilton59]

If you wanted to go with adding a resistor in series which would cut the speaker output volume by half, you could use 4 of these "RadioShack 8-ohm Non-inductive Resistor 20 Watt for Audio Applications".

https://www.amazon.com/8-ohm-Non-in...+Non-Inductive+Resistor&qid=1600270179&sr=8-2
You would need one resistor per speaker and you would simply put one in line with one of the speaker wires going into each speaker. So, for example, you could connect the + terminal of the speaker to one end of this resistor, and then connect the + end of the speaker wire to the other end of this resistor. The "-" end of the speaker wire would connect to the speaker as usual. This would put the resistor in "series" with the speaker and give you an approximate 16 ohms when used with an 8 ohm speaker. Note that the resistor will get warm to hot depending on how loud you turn up the amplifier so they should not be placed where they could cause any damage if hot.

 

[Kal Rubinson]

Hi everyone. Someone very close to me in his 70s has my is fond of quadraphonic tunes and uses an old Panasonic RE-7750 receiver with an Akai 8 track player. He uses the original speakers that came with the Panasonic and they only have one crappy speaker in them, so I want to get him a nice set of 4 better bookshelf speakers with a 6.5" speaker and tweeter in them.

It really looks like changing just the speakers is not a good plan for this. Note that the speaker output jacks are RCAs which confirm that the output is puny.
I also note that it seems the motivation for change is from you, not him. Let it be (until it breaks or he complains).

 

[EndoFury]

It really looks like changing just the speakers is not a good plan for this. Note that the speaker output jacks are RCAs which confirm that the output is puny.
I also note that it seems the motivation for change is from you, not him. Let it be (until it breaks or he complains).

Yeah, I think you're right. Unfortunately, I might not be able to cancel my speaker order. I'll try.

 

[LuvMyQuad]

You could but that would cut the output to the speaker by half as well... and that's resistance, not impedance a little different. You could put two speakers in series and truly have 16 ohms per channel.

Good point. Two 8 ohm speakers in series would provide an acceptable result and somewhat speak to what Kal mentions above about the puny power rating. Half of the power would at least go toward producing sound instead of being wasted as heat in a resistor. Ideally you'd want highly efficient speakers for this too. It all sounds like a tall order if you need to stay close to the size that the original speakers, as well as the cost of 8 speakers. About $400 for 4 sets of Polk T15s.

 

[EndoFury]

I ended up successfully canceling the speaker order. Thanks for steering me straight, guys. It was actually more of my desire than his. He's happy with it so I'm going to leave it alone.

 

[Kal Rubinson]

I ended up successfully canceling the speaker order. Thanks for steering me straight, guys. It was actually more of my desire than his. He's happy with it so I'm going to leave it alone.

Been there. Done that.

 

[~dave~~wave~]

Been there. Done that.

We have a saying in our neighborhood:
"No good deed goes unpunished."

 

[Sal1950]

We have a saying in our neighborhood:
"No good deed goes unpunished."

That's a good one.
After the OP spends his money and jumps the hoops to get things going, then the friend comments, "it doesn't sound as good as my old system", then what?
Been there and done that. LOL

 

[par4ken]

Unless the amp was built with no safety factor built in you should be fine running 8 ohm speakers, just don't crank it too too loud. But it's likely best not to chance blowing up a perfectly functioning vintage system. A better plan would be to add another amp designed for 8 ohms or lower (and almost all are). Otherwise leave it alone as you have already decided.