DIY bluetooth speaker

[SentinelAeon]

Perfect pitch doesnt give me any super powers, its just something i was born with. It was real simple, when i was about 3 years old my mom was playing a song on a piano and at some point missed a note. And i told her, why r u playing note C instead of D. To put it simple, when someone plays a note on a piano, i know which note it is. Or if someone plays 5 notes at once, i know which notes they are. That is all. I cannot improve a song because of perfect pitch, i just know which note it is. I guess i could make it more useful if i learned what frequency certain note is. Then if i heard a noise i could say for instance, this is 300Hz. Anyway, that is all, no super powers, but when i was young, it was amazing to me how people were impressed by it and i never understood whats special about it and couldnt understand how other people cannot do it. And to come back to my speaker, that is how i know that when i close the sides, the frequencies shift. I might try to record it today. I will play a note and i hope my mic can pick it up

 

[audioguru]

There is a wide range of people with different abilities of identifying details of pitch in music:
1) Tone deaf. They hear the sounds but do not hear the music. They do not like to listen to music.
2) Me. I hate to hear bagpipes and RAP. I also hate to hear the severe distortion of acid rock.
3) Real musicians and singers that do not need to use autotune.

Have you heard people say that a certain speaker produces "one note bass"? That is severe resonance. Almost any low frequency note causes the speaker resonance at the wrong musical frequency. I think your speaker does that because the enclosure is too small when the enclosure sides are closed. Bose little home speakers do that.

 

[audioguru]

Did you see the thread that says this speaker sounds good? It has a low cost too. Check for any reviews for it:

https://www.amazon.com/OontZ-Angle-Solo-Surprisingly-Splashproof/dp/B07DPVF8DQ

 

[SentinelAeon]

Well i finished the speaker. And to my surprise, the problems disapeared. It actualy sounds pleasant and also has that bang that im looking for. Obviously bass is limited but still you can hear it (my mic wont pick it up obviously). I am really happy with how this turned out and i am surprised that there is some bass, considering this is ultra compact speaker, i could probably fit it in my pocket.

 

[SentinelAeon]

Here you can hear some bass. What is funny though that on the video if i cover the passive membrane, you can hear no difference. While in reality, you can hear less bass. So yeah, only using 1 speaker on a 2x6W amp and it really sounds loud when i crank it up.

 

[audioguru]

In the first video the speaker sounds awful. The second video is unavailable because it is private.

 

[SentinelAeon]

Ok i fixed the second video. I guess its a bad recording cause in real, it doesnt sound that bad to me :/ But yeah, im using 2x6W cheap amp, there is hiss, enclosure is to small, speaker is to big, etc. Still, its better then nothing

 

[SentinelAeon]

I did a simple comparison between two cheap amps, TDA7492P 2x25W vs ZK-502L 2x50W. First one peaks at 15W per channel and badly cuts at high volume. Second one peaks at 57W (!!) and barely cut here and there. This is amazing considering the second one is cheaper, has a lot less components, is prettier, has very useful volume button, has lots of added accesories with it, etc. I think i just got my new favourite amp. I cant find which chip it uses but it just might be the TPA3110. Amazing, amazing. Please comment )

 

[audioguru]

You are destroying the little speaker by letting its voice coil hammer against the magnet structure because it has no enclosure.
You do not say the speaker impedance or the power supply voltage.

What are you measuring? The AC electrical power? Then you are also measuring the heat power produced.
You need to measure the continuous RMS voltage of the amplifier output at low distortion. Then calculate the power into the speaker impedance at low frequencies (because the speaker inductance causes its impedance to be higher at higher frequencies).

The TDA7492P produces about 15W to 18W into 8 ohms per channel at low distortion when its power supply voltage is 20V or 21V.
The ZK-502L amplifier is sold by all the Chinese online places and its "PA502X2" IC has no normal part number and therefore has no datasheet. Its IC has only 16 pins but a TPA3110 has 28 pins.

Your TDA7492 must be the original version (no "P") because it has a heatsink on its top. the "P" version has its metal pad on its bottom. Actually, your amplifier has 3 little heatsinks and there is not one like it shown in Google images. Then it does not have a TDA7492 IC.

You cannot compare the two amplifiers because they have different gains. The second amplifier has more gain and therefore produces more distortion power.
You must measure the output voltage of each amplifier at a level slightly less than clipping because then the distortion is very low.

If the amplifiers are class-D and use the same power supply and speaker impedance then their output powers will be almost identical.

 

[SentinelAeon]

The heatsinks on first amp, i added them. It originaly came with no heatsinks anywhere. I used same 3 ohm speaker in both cases and in both cases i used 24V. I know this is bad for amp and speakers, i simply wanted to measure them. The ZK-502L will play a lot louder, draw more current and also there will be a lot less clipping. I will try to read which chip is on ZK-502L because so far i am VERY impressed. Also its kind of amazing that it came with no heatsinks, but came with added things. The one i already got cost 6.5 bucks and i just ordered another one for 4.5 bucks. This is a total steal and will be great for my DIY speakers.


**broken link removed**

 

[SentinelAeon]

Sadly i cant get any good info from the chip itself. But only by what i heard and saw today i am seriously impressed. Its a really pretty thing. I think the back plate actualy serves as a heatsink, even though it looks like its made from plastic which would mean bad heat transfer. And its amazing that it manages to pull such numbers with no heatsink. On 4 ohm speaker it maxes at 2x50W when using 24V. No way all that is going into heat because i barely noticed any heat on the chips and this thing is loud, a LOT louder then the other one. Btw, i just found a board without heatsinks and it is indeed a TDA7492P chip on it

 

[audioguru]

Look at the datasheet for the TDA7492P. It is spec'd for an 8 ohm speaker and no more than 20V for its supply so you are seriously overloading it.

 

[SentinelAeon]

The ebay said up to 25V and 4 or 8 ohms. I guess i should read the datasheet instead of trusting ebay. But still, i pulled all the juice from it i could and reached like 15W per channel, i tried 21V also and same, 15W. So u have to admit the other one is a lot stronger

 

[audioguru]

Your power supply was 24V and the speaker was 3 ohms. The amplifiers are class-D switching type and if they had no losses then the bridged output would be 48V peak-to-peak which is 17V RMS. Then the output power into 3 ohms would be (17V squared)/3 ohms= 96.3W. The power supply current would try to be over 4A.

A TPA3116D2 amplifier IC can produce 70W per channel at low distortion into 4 ohm speakers when the supply is 24V and produce more power into 3 ohm speakers.

 

[SentinelAeon]

Soooo can we agree that thats a nice little amp i got me ?

 

[audioguru]

Do you like an amplifier made by a no-name company that has no detailed spec's?

 

[SentinelAeon]

If its super loud and sounds decent ofcourse. You have to understand that i am making ultra budget systems where every euro/dollar counts. If i will ever upgrade my hi-fi it will be different, ofcourse i will want quality gear with specs. Right now i just want to make cheap bluetooth systems for people who just want it to play loud and be compact. So yes, i am very impressed with the new amplifier. I wouldnt use it in my hi-fi but i sure would and probably will use it in my bluetooth speaker But yes, i will tell you more when i test it more

 

[SentinelAeon]

I just did a simple test and my speaker doesnt seem to go much lower then 80 or 70Hz. Its amazing that to me and my friends, we percive it as good bass speaker. I dont have an explanation for this. I guess anything under 80Hz sounds good enough for an untrained ear ?

 

[Nigel Goodwin]

As AG has said, it's 'one note' bass - so sounds 'good' because that 'one note' is excessively loud.

 

[SentinelAeon]

One note ? Could you tell me more ?