How can I know the specs of a phone speaker that looks broken?

Thread Starter

rambomhtri

Joined Nov 9, 2015
418
Hi all!

My landline phone's speaker broke the other day because "someone" threw it at the floor. The phone has 2 speakers, the ringer speaker (big black circle to the right) and the speaker you put next to your ear (right below the circle, it's one you solder there with 2 cables), which is the one broken. It was still working but the sound was distorted and rattling. The phone model is a Panasonic KX-TGA161R.

1634562420949.png

I disassembled it and saw that it was a 20 mm speaker. I also tested the DC resistance of the coil and I was reading 130 ohm steady. That's the first thing that bugged me, as I was expecting something between 8-32 ohm. May be one of the things broken is precisely the coil cable that is damaged and should read a much lower value. Basically, if you look for 20 mm (0.79 inch) speakers, 99% of them are between 8-32 ohm.

Sadly, the speaker has no way to identify it, it had printed in the back some letters but they are erased and can't tell a single character. Also, I've seen there's another parameter, watts, and the 20 mm speakers come in 0.5W, 1W, 2W... I don't know which one should I choose. The speaker looks like this:

1634564185090.png1634564310986.png

So, basically, I don't know what parameters should I choose. I don't know neither the wattage info. You need it to be 20 mm diameter, that's fine. Then the DC ohm gives you an idea of how loud it will work, but watts seems like extra info. I'm not at all a speaker savvy, but I thought in these specific scenarios, speaker diameter and DC ohm would give you all the parameters needed. No inductance, no power, no core permeability, no winding self-capacitance...
 

Papabravo

Joined Feb 24, 2006
17,235
There is no practical way to know because the parts are probably custom parts that you can't buy and the device itself is not designed to be repaired. Your best bet would be to salvage one from an identical handset.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
418
What do you mean it's not worth it?
AliExpress is full of $0.8-$5, 20 mm speakers with all kind of specs, how am I gonna toss a perfectly working phone because the speaker broke?

It is an insult to the planet and my soul. I am pretty pretty sure a 32 ohm 2W will do just fine, but since that's a guess I prefer to come here to check if someone can point out the speaker specs or any other tip.
 

JohnInTX

Joined Jun 26, 2012
4,594
What do you mean it's not worth it?
AliExpress is full of $0.8-$5, 20 mm speakers with all kind of specs, how am I gonna toss a perfectly working phone because the speaker broke?

It is an insult to the planet and my soul.
I like the way you think. Good luck with the fix.
 

Papabravo

Joined Feb 24, 2006
17,235
What do you mean it's not worth it?
AliExpress is full of $0.8-$5, 20 mm speakers with all kind of specs, how am I gonna toss a perfectly working phone because the speaker broke?

It is an insult to the planet and my soul. I am pretty pretty sure a 32 ohm 2W will do just fine, but since that's a guess I prefer to come here to check if someone can point out the speaker specs or any other tip.
I'm happy that you have the time and the patience to try. When I was working my time was also a valuable commodity. I seldom engaged in Trivial Pursuit.
 

DickCappels

Joined Aug 21, 2008
7,953
That little black thing on the right side of the photo? It looks like a "beeper" to me. Speakers are designed to transfer mechanical energy to the air over a wide range of frequencies. That thing looks like it is tuned like a thing that beeps, notice the large cavity with a small port that is absent in speakers.

I would look elsewhere for the broken speaker.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
418
That little black thing on the right side of the photo? It looks like a "beeper" to me. Speakers are designed to transfer mechanical energy to the air over a wide range of frequencies. That thing looks like it is tuned like a thing that beeps, notice the large cavity with a small port that is absent in speakers.

I would look elsewhere for the broken speaker.
Yeah, well, it is a beeper, which in my view is another type of speaker, and it is the one managing the ringing tones. Oh, also the one managing incoming voice when you enable speaker mode. The speaker that broke is the one you put on your ear and manages incoming voice.

Can someone explain to me for this specific scenario the parameters wattage of a speaker, DC resistance and inductance of the coil?
Correct me if I am wrong, but I guess this:
1. The wattage of a speaker means the maximum power (loudness) it can go before distorting or malfunction. In this case, a 0.25W speaker might distort due to the "high" power of the incoming voice signal, while a 1W speaker would handle the maximum incoming voice volume just fine, and a 5W speaker would make no difference, it would sound as high as the 1W, and simply still have a lot of room for higher volume which is useless because it's limited by the phone.
2. The DC resistance means, if it's very low, like 8 ohm, it will sound higher at a given signal than if it's 32 ohm, which will be harder to drive and will sound quieter. This looks like talking about wattage, I am guessing DC resistance and wattage are related.
3. The basic feature of a coil is its inductance "H", however this spec is not given when talking about speakers. Why?
 

DickCappels

Joined Aug 21, 2008
7,953
1. The answer to this question depends a lot on the capabilities of the amplifier driving it.

2. The same as answer 2. Speakers are very complicated devices. Efficiency varies considerably.

3. The total impedance is more important than the inductance. When the input impedance of the speaker matches the output impedance of the amplifier the maximum possible amount of power is transferred.
 

salihkanber

Joined Oct 16, 2021
7
Hi all!

My landline phone's speaker broke the other day because "someone" threw it at the floor. The phone has 2 speakers, the ringer speaker (big black circle to the right) and the speaker you put next to your ear (right below the circle, it's one you solder there with 2 cables), which is the one broken. It was still working but the sound was distorted and rattling. The phone model is a Panasonic KX-TGA161R.

View attachment 250566

I disassembled it and saw that it was a 20 mm speaker. I also tested the DC resistance of the coil and I was reading 130 ohm steady. That's the first thing that bugged me, as I was expecting something between 8-32 ohm. May be one of the things broken is precisely the coil cable that is damaged and should read a much lower value. Basically, if you look for 20 mm (0.79 inch) speakers, 99% of them are between 8-32 ohm.

Sadly, the speaker has no way to identify it, it had printed in the back some letters but they are erased and can't tell a single character. Also, I've seen there's another parameter, watts, and the 20 mm speakers come in 0.5W, 1W, 2W... I don't know which one should I choose. The speaker looks like this:

View attachment 250569View attachment 250570

So, basically, I don't know what parameters should I choose. I don't know neither the wattage info. You need it to be 20 mm diameter, that's fine. Then the DC ohm gives you an idea of how loud it will work, but watts seems like extra info. I'm not at all a speaker savvy, but I thought in these specific scenarios, speaker diameter and DC ohm would give you all the parameters needed. No inductance, no power, no core permeability, no winding self-capacitance...
The important parameter here is the resistance of the speaker, if you select smaller resistances the driver may get damaged. No problem will occur if you select larger resistances. So start trying through that road.
 

bassbindevil

Joined Jan 23, 2014
201
Cordless phones are not rare items at thrift stores, if you wanted to get a donor handset or just replace the whole system. Batteries might be an issue.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
418
0.1W into a handset speaker next to your ear is VERY loud.
A replacement should be 45 ohms to 200 ohms.
As far as I know, the power for the speaker is provided by the phone, not the speaker itself, so it doesn't matter how many W the speaker is rated, knowing it's not powered by anything else but the 2 cables, the W are already determined by the phone. That means that there's a sweet spot that I'm trying to find where the speaker works fine. If you install a higher W speaker it will not sound louder, simply sound worse or quiet, and if you put a lower W speaker it might sound as loud as the original but distorted and bad.
 

Audioguru again

Joined Oct 21, 2019
3,822
The little speaker is used an an earphone, not playing loudly so the power rating does not matter. Its impedance is important.
An 8 ohm speaker is very common but will overload the driving circuit.
 
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