Well, in the pictures that looks like a cone tweeter, not any piezo tweeter I've seen. I'd expect the stereo imaging would be better without it, and it may hurt the frequency response more than it helps. The crossover could be improved, but it would cost 10 times what the speakers are worth.
One way to upgrade these speakers is to donate them to a thrift store that will give you a discount coupon for future purchases. Then pick out a better pair of used speakers, but that could take time and patience and luck. Try pawn shops and used audio specialists too; they don't waste shelf space on junk.

 

Using the speakers should be fine, but you probably will have to add a crossover circuit for the two speakers in each cabinet as they likely don't have one.
Parts Express has a good selection of crossover components.
The two amps have a 3500Hz crossover, so that frequency for a two-way crossover would be appropriate.

They are described as "Bi-Wired", which means they have built-in crossovers, with the intention that the bass section and treble section are to be joined by separate cables to the output of the same amplifier.
If they had no crossovers and were intended to be driven by two separate amplifiers with crossovers implemented at the small-signal stage, they would be called "Bi-Amped"
I'd agree with @BobTPH that the built-in crossover may be 1st order, and just be a series capacitor, but if that sufficiently reduces the bass to the tweeter then it is better than higher order crossovers in terms of phase shift. There may also be an attenuator as dome-tweeters tend to be more efficient that small cone woofers.
So, I'd say you can connect them to any amplifier, but, before you do, just to be on the safe side, take out the tweeter and make sure it has a series capacitor.
They are likely to be a fairly competent design but not top-of-the-range, because, if they were, Panasonic would have badged them "Technics".

 

I made a pair of speakers and I designed and built a proper 3rd-order highpass and lowpass crossover network. The phase shift is is cancelled at the crossover frequency and is not heard.

The cheap Panasonic speakers appear to have cone shriekers, not dome tweeters.
Piezo tweeters sound awful and some cheap speakers have a photo of a tweeter instead of a real one.

 

"Consumer Electronics", especially audio, had specifications that used quite different definitions of words than anybody else. In short, LIES! rating power out at 10% DISTORTION was only acceptable to those who did not realize that they were hearing 10% distortion. AudioGuru was being rather charitable in his description. An investigation of the present amplifier may reveal what the different outputs actually are. My recollection is that not all panasonic products were intended to ever be serviced.

 

Hi,
Please stay on the TS's Topic, he is not asking about quality or power ratings.

Mod

 

So I opened it up last night for a clue. (amp not speakers) This is what I found. (Tool arriving today - thanks prime - to help with speaker photos). I did downscale these photos not to take up too much room to about 400ish kb, from 6Mb, I could have gone less?

As You can see, a pair of 4 crimps.

Going by what is plugged into what board, I can make some guesses. I imagine these boards and units were used in a wide range of 'consumer' Panasonic goods.

Now we can see the amp board more clearly. I put the sockets on just to show how it is mounted.

That green board on the right? I took that out next - the amp I believe. It had the cooling fins mounted on it. The speaker crimps were routed through the brown board at the bottom, directly to the green board. The brown board on the very far right has the power socket and a transformer. The transformer coil is hidden behind (but in no way touching) the cooling fins.

Other side of amp board.

Ok this surprised me. I know you have capacitors on an amp, but this big? It was a good 2 inches high. (Got a bit nervous about residual charge - bad experience with much smaller ones). And hang on, those diodes are huge too. And there are four of them. (Murmur in brain: _isn't that what you need to make a rectifier?_) Oh. So this amp board has some power circuitry on it?

Is it even the amp board at all? Hmmm... ...yes I think it is, because the speakers are wired to it and it has what I think are amplifying transistors - that get hot - attached to a heat sink.

Ok one more, board layout directly in the best lighting I can do:

The speakers are coming in entirely from that black socket upper left. The brown board on the left where my thumb is, that is the base board into which everything plugs.

So what have I learned from this?

• Ask wife first *before* randomly disassembling her stuff. My successful-repair track record is irrelevant, permission matters.
• It _might_ have been designed for repair, it was easy to take apart and boards seem to be 'drop in'.
• Following the tracks can just be confusing. I think these boards only had one layer so there were no hidden jumps. Even so, I did not get to fully track connections.
• "Drilling" or "sawing" of the speaker cabinets is probably a bad idea.
• Boards are not always function specific. - I can think of a few manufacturing reasons and even 'repair' reasons.

Does this answer the question: is there any element of crossover in the unit itself?
No I don't think it does. Perhaps this will be answered when I open the speaker unit.

Does this answer the question: is this bi amped?
Sort of, and I think the answer is probably yes, because of the 3 'amplifier transistors'. But it does only complicate what I know. If bi-amped then why 3 transistors, if that is what they are, and not a multiple of the channel count or the cabinet count? (But that pair of long thin transistors could have anything in it - 23 each - a few functional ones and loads of non used ones.)

This does not get me substantially closer to wiring the speakers. Perhaps this doesn't matter, lets find out later when I 'look inside' the speakers.

Given some of the above 'Human factors', throwing the speakers out whole sale due to potential cheaper purchase of new is less appealing than it was. I don't mind making some expense in the name of attending to what is important to other people. I also can see how making a 'learning journey' in this field is worth the cost.

 

Could you get the part number off IC300 and IC500?

And yes, that capacitor and those rectifiers are the size you tend to find in a power amplifier. There's not much voltage on them. If you short them out with a screwdriver there will be a bit of a splash, but nothing that will cause a shock (a surprise maybe, but not a shock)

 

This tells me a whole lot! The pictures show two stereo power amplifier modules, so either there are actually four channels, and it is "Bi-Amped" or it may be just two channels and a bridged-transformerless arrangement. The four bigger diodes are for the power supply, as is that bigger capacitor. Given that there is only one large filter it is more likely that it is a single voltage system, not positive and negative to he amplifier.
There are only two amplifier ICs, the large black ones on the heat sink. That third device is a transistor, probably a voltage regulator for the receiver or CD player logic circuits.
Those four items near the speaker terminal board with coils of wire on them, and L--- designations are choke coils, part of the audio output, intended to keep RF noise either out of the unit or to prevent it from escaping. A.G. can better explain that part. Some analysis can be done here by seeing if the black terminals on that speaker connector circuit board are all connected to each other or not.
Be very careful putting it back together, it is easy to get those white connectors one-pin-over when plugging them back on.

 

The left amplifier has small capacitors around it, and the right amplifier has electrolytics, suggesting the left may be treble and the right may be bass.
I only see one smoothing capacitor, suggesting a single ended power supply.
That would mean that there should be output capacitors, the one near R578 and the other one like it could be, but don't really look big enough, and I don't see output capacitors for the treble section.

 

This connector appears to be labled “HI_L, HI_R, LO_L, LO_R” which suggests biamplification.

I would use a signal generator and try driving the red/black and blue/white pairs on the speakers.

 

The left amplifier has small capacitors around it, and the right amplifier has electrolytics, suggesting the left may be treble and the right may be bass.
I only see one smoothing capacitor, suggesting a single ended power supply.
That would mean that there should be output capacitors, the one near R578 and the other one like it could be, but don't really look big enough, and I don't see output capacitors for the treble section.

Good point about those caps. And notice that the two sections have similar designations: 300 series and 500 series for parts. So it is a pair of stereo amplifiers, an actual bi-amped setup. And probably those chokes are one in each output, with the return common, or at least sort of common.
This tells us that probably there is no crossover inside the speakers boxes. It tells me that the ts NEEDS TO CHECK EACH speaker to see if it is still working. I have come across several 2-way split systems with the bass speaker coil open. That would alter the project quite a bit. Just use any audio output to drive one pair of wires at a time and verify that sound comes out.

 

I know what a tone generator is, but I don't have one. I have a selection of resistors and capacitors and bread board, so I started to search how to make... ...surely I can do an simple oscillator at approximate frequency?

While thinking about it I began to wonder if my little cobbled together thing in this particular rabbit hole may not have enough welly to do it. Fortuitously, Google gave me a webpage with a tone generator - I could play it out of the PC.

I can get 440Hz, 1000Hz, 3k5Hz and 7kHz from both tweeter and mid cone in both Left and Right speaker cabinets The mid/low cone will reach 100Hz, 90, 80, 70, 60, and down to 52, but barely detectable in a quiet room below 75hz. The wires and speakers are independent of each other. Black/Red is the lower end and White/Blue is the upper.

 

I know what a tone generator is, but I don't have one. I have a selection of resistors and capacitors and bread board, so I started to search how to make... ...surely I can do an simple oscillator at approximate frequency?

While thinking about it I began to wonder if my little cobbled together thing in this particular rabbit hole may not have enough welly to do it. Fortuitously, Google gave me a webpage with a tone generator - I could play it out of the PC.

I can get 440Hz, 1000Hz, 3k5Hz and 7kHz from both tweeter and mid cone in both Left and Right speaker cabinets The mid/low cone will reach 100Hz, 90, 80, 70, 60, and down to 52, but barely detectable in a quiet room below 75hz. The wires and speakers are independent of each other. Black/Red is the lower end and White/Blue is the upper.

Fits with everything else you've discovered. So now if you want to use the speakers you can either use two amps and do the filtering as input to them or more conventionally use a crossover network external to the speaker cabinet.

 

Amp chips:
The left one (IC300) is: AN17831A. You can see here and here it is a 2 channel amp.
I put this photo less compressed hard to see.


And the right one, much easier to see:

IC500 = AN17808B
And this is the only reliable (available) page I can get. This right hand one is the 5w amp - high channel.

 

Can you guess where I am going with this: wife likes her sound system, but seldom uses it. Her music is (mostly) also copied to a network share. She likes using her swipe screen to access her music, but listens to it on YouTube not the local file network share. There are projects out there that can join the dots here. They involve odroid/rpi and I2C amp boards, all of which have just left and right, usually phono out. They produce either a local webpage, or use an app (or both) and really tick the 'phone control' box.

This means if there is no cross over in the speakers I am weighing up producing one. Speaker images shortly.

 

I think what you have is a system that is bi-amped and actively equalized to extend the response of the drivers. You might not be able to use these speakers effectively with a conventional amp. This is what Bose is famous for.

I also think the amp outputs are bridged. If not, they would normally have all the ground terminals black. You could check continuity between the terminals. If there is no common connection, they are bridged.

Bob

Bob

 

What was the complaint about the present system? Or just wanting something a lot louder??

 

The answer.

I got an endoscope to look inside the speakers. It was not very expensive, and I needed it for other jobs. Looking inside the speakers are not connected to each other. The low cone is directly attached but the high cone has a black cylinder. You are so right and you knew all along. Here is the endoscope image.

This is the high cone.

The article is wrapped in electrical tape. I could not move it much with the endoscope hooks.

Then I noticed the screw, seen here in the bottom left, coming into the body of cabinet. So that was coming in from somewhere, but I had previously not seen any screw heads on the outside of the unit. Unless it was hidden somehow. Which it was:


and peeling the front off (glued) and unwrapping the electrical tape revealed:


4.7 microFarads, in series.

To summarise this far, The system has lots of equalization presets, so I think it is actively equalised. You can't turn them off, it is always on one of the presets. It is bi-amped, with a simple capacitor on the high cone.

Checking the continuity over the crimps on the back of the amp. There is no resistance between the blue port for the Left tweeter and the blue port for the Right tweeter, it is continuous. There is no resistance between the white port for the Left tweeter and the white port for the Right tweeter, it is continuous. There is about 5kohm resistance between the red port for the Left bass cone and the red port for the Right bass cone, it is continuous. There is about 5kohm resistance between the red port for the Left bass cone and the red port for the Right bass cone, it is continuous. Otherwise there is no continuity between any other pair combination. There is no common neutral connection between any channel, Left or Right, hi or low.

(Correct me) : These are very specifically for an equalised bi-amp crossover set up, and are best paired with their main unit. Using them requires accounting for each of these design characteristics with intermediate electronics (how much?). Using them without any intermediate modification would either blow something or just sound wrong such that it may not be much better than the cell phone speakers currently in play.

Thank you to everyone again for your time, and helpful comments.

 

What was the complaint about the present system? Or just wanting something a lot louder??

It is seldom used. The chief listener in that room (to whom it belongs) defaults to YouTube streaming through her phone speakers. She wants to listen to her CDs (no ads), and still likes to receive music as a gift (downloads go on the server). This amp has no simple line in, a disappointing finding, that would have made it so easy.

Lying in bed the other night I wondered if I could somehow use the AM, FM or tape, (which it has and she never uses - CD person only) as a line in. Googling this in the past has revealed tape can be quite poor for this. Perhaps now what I am weighing up is 'homebrew crossover that can account for not being equalised or bi-amped' verses something that will make an AM/FM output.

We are miles away from how to wire up a speaker. Has this now come to a conclusion? and do I need to open a new thread as "Complex crossover verses missing line-in work-around"?

Moderator?

 

The tape channel has a preamplifier connected to the tape head, and then tape equalization, and after that the signal goes to the selector switch.So at that point a line input could be substituted, presuming that the switch is an actual mechanical switch and not done in the electronics. So is there a physical selector switch??
After looking at the photos and seeing the labels on the connectors another idea comes to mind. It looks like the cable from the tape deck connects to the radio circuit board. If that is true, then at that cable a line input could be made, depending on how much of the preamplifier circuit is on the tape deck. Is it a play-only deck, or does it have recording ability as well? And can we get one of those good photos showing the text next to the connectors from the tape deck. Adding a line in connection may just have become simple. Possibly.