Original Ceramic Tweeters VS Regular Dome, Piezo or Cone Tweeters - Do I need to Replace Them ?

Many boomboxes of 80's have a pair of Ceramic Tweeters.
High impedance , narrow frequency range and very low output
make them totally useless if we're talking about HQ sound.
Try to disconnect those original ceramic tweeters and you'll find
absolutely no difference in sound quality of your machine.
So why manufacturers installed them in 80's?
It was just a marketing trick !
Manufacturers could legally claim it as a Two-Way Speakers System ,
but all those models had very sensitive low impedance
wide range drivers, and those were good enough to match
promised specs values (up to ~ 14 - 16 kHz) without any tweeters.
In fact , all those ceramic tweeters were decorative.

Original RX-CT900 Ceramic Tweeters & wires

I have replaced my original ceramic tweeters with
high output piezo tweeters on my RX-CT900
and after the replacement now it's up to 19 kHz /measured/ and
trebles sound way more detailed and it makes cents!
So if you want to discover what your boombox amp
can do for real - i recommend that to you.
Any suitable car tweeters are good as well.
And don't forget about capacitors.
The values of capacitors may vary /depends of impedance of your tweeters/
4,7 uf 100V would be fine in most cases.
You 'll need Electrolytic Non-Polarized Crossover Capacitors


Tips :
- Make sure you check&listen your tweeters
with capacitors before the final assembling of your speaker units.
In case they sound "too low" - try a higher value capacitors.
- Make sure you seal your new tweeters with
some sealant to prevent any leaks outside of speakers
cabinets and to isolate tweeters inside the cabinets
from woofers sound waves..
You may also check these posts about serious improving
of my RX-CT900 and RX-CT980 speakers :
http://stereo2go.com/forums/threads/modifying-rx-ct900-speakers-has-made-an-incredibly-deep-bass-from-40-hz.6343/
http://stereo2go.com/forums/threads/modifying-rx-ct980-has-made-a-portable-hi-fi.6332/
https://www.stereo2go.com/forums/threads/combining-your-favorite-boombox-with-any-home-stereo.8548/

Enjoy your favorite stereo and don't forget to check my
Reel Cassette Store - https://sites.google.com/view/reelcassettetapes

 

I believe one of the differences between the Sharp GF767 and GF777 was that the more expensive GF777 had real tweeters. Of course, as you point out, a real tweeter also needs a minimum of a blocking capacitor for each one (unless the box is a Panasonic Bi-amped one). More expense for the manufacturer.

 

Agree completely with it being a marketing thing - they wanted to shout about more features on the boombox or in the blurb.

What I find interesting here is the devices indicated in the below pic of a Hitachi 3D7 are referred to AFAIK as 'Piezo tweeters'.
Clearly, they are wired in devices (no crossover, however) but I personally have never heard a thing coming from them, & many other similarly equipped boomboxes.

I'm guessing either these are not 'high output' piezos or they are mis-named ceramic tweeters...

 

Those are in fact piezos, just cheap crap ones. Like the ones inside a talking greeting card.

Perhaps when the boombox was new, they worked, but now they don't anymore. Or their frequency range is too high to be heard. I personally can't hear anything above 13 or 14K, so I wouldn't know....

 

Yes, and they're good paper cone tweeters too.

 

Hello! Thanks a lot for your attention to my posts!
I think those are not a piezo type, because I don't see any capacitors there,
which means they're high impedance plus they just look like a typical ceramics.
Check their impedance and go from there.
The good thing is - you have plenty of space to install any type of tweeters in this cabinet !
Measurements are the biggest problem in most cases, but you're lucky!
I would go with automotive ones in this case..
Please feel free to contact me for any further help!

 

My guess, from their looks, is that they are very similar to the alarm sounders used in Digital watches and Musical Greetings cards. I/m sure we all know what those sound like.

 

Exactly!

 

Do you have any pics of those speakers ?
What's their impedance ?

 

Piezo tweeters are usually flat discs. However, they can be shaped like a dome instead. Also, they can be made of metal, OR ceramic.

The phrase "ceramic tweeter" is meaningless because without further information or visual inspection, you won't know if it's a piezo tweeter with no moving parts, or a regular tweeter with moving parts such as a surround, voice coil, etc. It could be either.

Even the word "dome" is meaningless because it could be either a piezo or not.

So there are:
1) Flat metal piezos (typical in cheap boomboxes and greeting cards)
2) Flat ceramic piezos
3) Domed ceramic piezos
4) Domed ceramic non-piezos, complete with a magnet, voice coil, suspension, etc.

 

I understand your note, but in the Official Panasonic RX-CT900 Service Manual
they are "2 cm Ceramic Speakers" under the " Tweeter Type" section
Please, see the attachment.
P.S. What would you call them?

 

They're piezo because they're flat with no magnet or voice coil.
As to whether they are metal or ceramic, I have no idea.

 

I think the main thing that qualifies a speaker as a tweeter is the frequency response, which in turn depends on the designers intentions. The designer of a small speaker for something like the iPad I am typing on will put considerable effort in getting a wide frequency respose and trying to provide some bass. The designer of a Tweeter only has to worry about providing good sound at the higher frequencies.

Some Panasonic Cobras have woofers that are smaller than the mid range speakers which seems strange, but their construction, especially around the edge of the cone, is very different.

 

Exactly ! Only a cone type tweeters can be considered as real tweeters on those models of 80's.