DIY bluetooth speaker

SentinelAeon said:

But it makes no sense. What if i had 1S2P, that would mean 4000mAh pack ? Same as 6S2P ?

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Amp-hours are current, irrelevant of voltage.

Power capacity is given as Watt-hours; that's amp-hours * average pack voltage (typically 3.7V per cell).

That works out that any series - parallel combination with the same number of cells (with all the same capacity) gives the same watt-hour capacity.
Use the configuration that gives the optimum voltage range for the device.

And remember the cell average voltage not cell numbers in calculations; 50W draw from a 1Sxx setup is an average of roughly 50 / 3.7 = 13.5A.

Ohh i get it now .. 6S is 2000mAh because ... in series amps do not add up which i know. In reality, 6S will work 6x longer than 1S ... BECAUSE 6S has bigger voltage than 1S and that means it needs 6x less amps for same wattage. So, while both have the same mAh, the 6S has 6x bigger watt hours. Right ?

Its kind of like 2 cars, both have 60 liter gas tank. But 1 car weights 1000kg and 1 weights 2000kg. The one with 1000kg will drive much longer on that 60L tank because it is lighter (assuming same motor in both cars). But they still both have the same gas capacity. Did i get it right this time ? I think i did.

You used 6s because you want lots of power in a 4 ohm speaker. The datasheet of a TPA3116D2 amplifier IC shows that when a 6S battery is fully charged at 25.2V, the power in the 4 ohm speaker is 65W at fairly low distortion. When the battery voltage has dropped to 22.2V, the power in the speaker is 50.2W.

With a TPA3116D2 amplifier IC powered from a 3s fully charged battery, the power in the 4 ohm speaker is 16W at fairly low distortion

I know all about 1S and 6S and 6S2P. All i am saying is, more batteries means higher voltage, hense lower needed amperage to get the same wattage out. And while 1S vs 6S have the same mAh, they certanly DO NOT have the same Wh. And Wh is what i need in my case.

Where did you get TPA3116, i have never used that before. I am using 2x50W amp now that barely distorts at full 50W. But true, i am getting some other amplifiers, mostly mono ones, i will have to check which chip they use and when i decide whether to use 4S, 5S or 6S, i will check the datasheet to make sure that at 100% volume it distorts AS LITTLE as POSSIBLE. Most amps distort at 100% BUT there is a huge difference between them. The amp i have right now, when at 100% volume is totaly ok for listening. While my last amp distorted badly at max volume (actualy it was half speaker half amps fault. 1 of the speakers distorted because it couldnt handle that much low frequency (no crossover made at the time) and woofer was cutting because amp couldnt drive it at 100%, tried it with stronger amp and got no clipping.). But enough about that, i made a huge purchase and 1 of the speakers i ordered is this:


SB20PFC30-4 8"

This is for that guy i was telling you about that wants loudness over all else. Doesn't care much bout quality and bass, just wants loudness. So tech guys at that company recomended me this. It goes fairly low in 15L enclosure, i think 60 or 65Hz, which is plenty for that guy. So maybe u can comment on what u think about that speaker. If u had the same budget i do, would u pick this one or would you pick some other speaker ?

If you turn up a volume control to maximum then the output power depends on the input signal level and the gain of the amplifier. Input levels vary a lot so most amplifiers have "extra" gain so that you can turn up the output level of a faint piece of music but then with a normal louder input signal level the output will be clipping with severe distortion unless the volume control is turned down. Therefore when you say"100% volume" you should mean the highest output level without clipping.

Most cheap Chinese 2x 50W amplifiers use the excellent Texas Instruments TPA3116D2 IC and some use cheap copies that don't work well.
I remember now that you were looking at the TDA7492P Rev 6 that has its output power limited by its heating because its metal tab is on its bottom so a heatsink cannot be attached on top. It cannot drive a 4 ohm speaker. I cannot remember if the older TDA7492 Rev 5 is still available and its metal tab is on top so a heatsink can be used. It also cannot drive a 4 ohm speaker.

The new 8" speaker you found seems to be pretty good.

I am using this amp right now:


You already said u cant find the chip it uses. But im telling u, for this price, it is amazing. Remember, TDA7492 was like 7 dollars and it was only 2x25W. This is 2x50W (actualy managed to get 60W from the channel without distortion but thats another story). And while it heats a bit, i seriously doubt there is a huge amount of watts being wasted on it as heat. It comes with no heatsinks, i added heatsink to each of the chips just in case. I got this amp for like 3-4 dollars when i bought it. It has a volume knob which is why i ordered it in the first place. I am really happy with it. The only reason i am looking for replacement is that i am building woofer + tweeter build and for that i need mono, unless i want wierd sound in songs that use hard stereo (found a few, sound wierd). So what i plan to do is, use separate receiver, mix its output into mono and use 1x100W which gives 50W into 4 ohm speaker, i will use crossover etc. Obviously i will have to test and play around with it again to get the performance i get from this unbelivable nice and cheap small thing. But dont worry i will get there. I ordered so much stuff from aliexpress and im waiting like an idiot because of this corona. I have like 180 opened orders awaiting delivery.

Good to hear you like the 8" speaker, thank you. Let's hope it lives to the expectations. The problem is .... how will i test it at 100% volume from my phone ? I seriously do not think i can do that, even though my workshop is in the part of the apartment where the only neighbour is upper one and they have a cooking place there. But i think they will think i lost it if i put it on max volume. Even this 2x50W speaker i made with tcp115 ... its so loud i can never leave it on more than 5 seconds.

The cheap amplifier you bought is sold by many Chinese online places and it has no detailed spec's. Its maximum allowed supply is 24V and since the amplifier IC has no heatsink then 2 x 50W will fry it.

Challenge accepted, havent fried any of them yet And it says it has overheat protection so we will see. Though i seriously doubt they would sell it without heatsink if there was danger of frying. Remember, the first amp i bought i got tons of additional parts with it. A small screwdriver and a little plastic case. So i seriously think they would add a 2x3mm tiny heatsink if it was worth it, it costs less than a screwdriver But we will see

Btw ... ok, i calculate the enclosure ok. But i use quite thick wires to connect everything and since there is so many parts, thats lots of wires. Next time i will calculate the volume of wires also to add to enclosure. So ... i was wondering. My program only calculates the correct port length. But, is there a program that will actualy calculate bass response for a given port size ?So for instance i import a speaker, select enclosure volume and port diameter and port length. And the program will tell me the graph that this port will produce (i would like to know how much to bass it adds or removes if i change port length by 1cm for instance ...)

The older TDA7492 rev 5 amplifier IC had a metal tab on top so that a heatsink can be attached. It was rated at 100 Whats.
The newer TDA7492 rev 6 has its metal tab on the bottom and the spec's say the type of dual-layer pcb and the size of the copper under the IC determine that it has a rating of 50 Whats.

The IC detects temperature and if it gets too hot then it shuts down. You do not want your sound system to stop by itself so you use the recommended heatsink or pcb thermal protections.

I think an IC thermal shutdown is to be used only a few times when you forget to open the cupboard the amplifier is in or if you play a continuous test tone.
I think if thermal shutdown is used often then the IC will be damaged by thermal fatigue.

Programs and speaker spec's for a ported enclosure say or recommend how to do it correctly. They do not show what happens when the enclosure or port are the wrong sizes..
A few programs or the speaker spec's will show a graph of the frequency response.

Well i would still love to see a program that can show me how port length affects the bass.

Anyway i tested my newerst speaker, 2x50W, TCP115 4 ohm on left channel and tweeter on right. Wow. Wow. All i can say. This speaker really packs a punch. And i am telling you from how people responded. I did many speakers and always till now there was some complaint, either it was not loud enough or there was not enough bass. This time, people were like, wow. A few people actualy right away said that they want to buy that speaker from me, when i actualy make more of them.

I am really really glad how it came out. I am usualy my own biggest critic but this time, all i can say is wow. Ofcourse i plan to improve speakers. First, mono 50W amp to correct that stereo thing. Then, better tweeter which im getting in a few days. Add 3.5mm jack and the option to charge phone using speakers battery. But other than that ... yes, it really packs a punch. JBL extreme 2 obviously cant keep up with it (couldnt even with my old speaker) but now i actualy am looking for a person with JBL boombox, so i can test both speakers with dB meter, compare bass, etc. I cant say anything right now but i am pretty sure it is close enough as far as bass and loudness goes. And remember, JBL boombox is 300€ř in my country. My speaker is 60€. And while it is a FACT that if u put both speakers and test them in a studio, it will show that JBL boombox is superior in quality and whatnot. But, when you have a large group of people outside that want loud music for fair price .. i am fairly confident u simply cannot get a better bang for buck than my speaker right now. I mean, jesus, for 60€, i checked what u get and u get a ******* keychain speaker, pardon my language but seriously, keychain speaker ?

So yes, i am happy with the product. I need to fix that stereo-mono thing asap since its just not good. But loudness ? Bass ? People in our group have JBL extreme 2 and that nice Sony speaker (which btw is only 150€ and is really loud and has great bass). But never have i seen the response i saw today. And i simply think that it is amazing that me - a computer science engineer with no audio knowledge whatsoever, can get into it, learn, read, work, and can actualy make a pretty nice budget speaker that people like. Now just to be clear, this speaker obviously would be rated as crap by any audiophile, it is just impossible for me, a single engineer to make the same product as like 500 engineers at JBL. But, it is working and making people happy. And this was my goal all along, get something loud and bass-y to people who dont want to spend 300€.

So while i am really happy, i am ready for "counter attack". So many things to improve. But this speaker ... well it already has a new owner ... but i am close to finishing another one - a clone of it. And this will be from now on my main speaker. So the fact that i will be using it, shows that i am happy with it, otherwise i would just buy JBL boombox or something.

ps: just a funny thing ... a friend has JBL extreme 2 with bad battery. And obviously my speaker is a LOT louder and has more bass. But. My friend said, i want this speaker. And i say, sure, 60€ is friendly price. And he says, i have no money. And i am like, sure, i will make u a speaker and u give me ur faulty JBL extreme 2. And he was like, really ? You serious ? And i am like sure. Cause i can replace the battery and sell that overpriced thing for double the price. But it was just amazing to see this friend be amazed like, you would give me THAT speaker for a puny JBL extreme 2 ?! It was amazing.

And just to not look like a big ignoramus (since obviously i am still amazed at the response of people ..), i still belive JBL and SONY speakers are a marvel. To make something so small and still pack a punch and have great bass, it earns my respect. I just do not belive that price/performance they are better than me. At least thats what people say.

You selected a good little woofer to make people think it produces good bass when instead its small size cuts the bottom 1.5 octaves of our hearing.
Or maybe you selected music that has no deep bass sounds below about 60Hz.

Just now I tried singing 60Hz. Just barely. You try to see how low you and your friends can sing.

My main stereo speakers are flat down to 50Hz and I added a bass boost circuit so they can play flat down to 30Hz. Since the mids and highs are reduced but the deep bass plays at maximum power then you lose some mids and highs power.
Here is a bass boost circuit for you:

Well my speaker has F3 of 55Hz. And i just checked JBL extreme 2 and its frequency range is 55-20.000Hz. So what do you want from me ? I am trying to do the best i can with what i have and i cannot carry a 50L speaker around in my backpack. 4L is the most i can have in my backpack and still have place for 6 beers. Which is how people want to carry the speaker around. People were happy. I dont know how demanding you are but when ur outside, drinking beer and talking with friends, do you really think people will sit there thinking, hmm, i just noticed we are missing 40-50Hz bass range. Most of those people have much worse speakers at home than the speaker i carry around, they have those cheap pc speakers the size of beer can that has no bass. If people are happy, i am happy. I dont do this for money, i do it so people can be happy without having to pay 300€ for a PVC pipe. And btw, im not buying that JBL extreme 2 has 55Hz F3. A while ago i saw datasheet where it said frequency response 50-20.000Hz and -3dB of 65Hz. So there you have it. If i wanted in this enclosure i could go to 50Hz, but im fine with 55Hz and a few dB boost under 100Hz.

Somehow you simply cannot understand that not everyone thinks like you and hears like you. You are audiophile. The people who want a cheap bluetooth speaker want it to be loud and have bass or feel to have bass or 1 note or whatever the **** its called. And while your help with me building a speaker has been invaluable, and i thank you for it, i think you not satisfied with the product unless its pure perfection. Well trust me, no one who is an audiophile buys a 300$ PVC pipe either. And just btw .. my big speakers at home probably have F3 at around 40Hz. And guess what. For some reason, the bluetooth speaker sounds bassier. Am i deaf ? Well, i have absolute hearing and have been playing an instrument semi-profesional for 30 years. So maybe i am deaf but certanly my hearing is better than most of the people you see outside. And when you listen to either 90's eurodance or some rock amateurs like Slayer, well, i think the deficit of quality is not on the side of speaker - its on the side of a song. And i am pretty sure no one will play rachmaninoff on this bluetooth speaker, because that music deserves something decent.

As for bass extension, i am not really sure how that would end up being on TCP115. They are 55-5000Hz and somehow i doubt they can give anything more than they are already giving. But if you think it will work, then i will look into it.

You somehow remind me of a harsh father who is never happy with anything his son does. I never had such father so maybe this is a lesson for me, because talking to you, i really feel like no matter what i do, you will not be happy with it. Or maybe u r doing it so that i wouldnt be happy with the product and would keep improving it, making a better speaker in the end. Let me have my 5 minutes of joy. I genuinely felt good when i saw people coming from all directions, looking at the speaker like they saw an alien and complimenting its loudness and bass. With JBL extreme 2 we never were happy with its loudness, always craving for more. Well, yesterday, no one asked for more bass or loudness.

Over the last many hundreds of posts on this thread you have advanced now to make good speakers that do exactly what you want. Before your speakers designs were random but I think you were lucky with one of them.

Thank you, that is all i wanted to hear So now i have 2 new things to discuss, besides the fact that painting the speaker is 1 of the most tedious things i ever did and takes 80% of the time it takes me to make this speaker, which is just insane.

1) Right now all the speakers use TCP115 4 ohm, including the one i am making for myself. Enclosure is about 4L, the dayton costs like 14€ a piece. So just for the fun of it, i went through the database of speaker to see if maybe there is a better speaker than TCP115 4 ohm i could use for my speaker only. I set the budget at 60€ for woofer and that is a whooping 4 times as much as the TCP115 4 ohm. I even set the speaker size to 5" max, even though the TCP115 is only 4". And guess what ? I couldnt find a single speaker that could at least match TCP115 in loudness and bass. Now this makes me belive that TCP115 is insane budget speaker. Surely there could be something tiny bit better for 60€ but no, speakers are actualy worse in this small enclosure.

2) You were talking about bass boost. I am interested in this idea (if i understand it right, this way i could adjust the case resonant frequency so its F3 would be higher but that would mean big boost in frequencies under 100Hz and help with loudness). But how does that translate to the speakers ? I am pretty sure at 40W i am driving the TCP115 4 ohm as much as i can. Do you think it has anything else to give with bass boost or will it just mean insane distortion ?

A bass boost circuit allows the very low frequencies to be at full power but the mids and highs have reduced power.
A speaker that is 8" or larger produces low frequency air vibrations that you can feel.

When I worked with Pro Audio I bought an 18" sub-woofer raw speaker that was discontinued and I got it for a very low cost. It is still brand new in its box, I never tried it. I will sell it to somebody at a car audio meet where they blow each other away with very loud sounds.

Hmm but i am not sure i want to trade very low frequencies for mids and highs. I mean does that mean i will have less power at 70Hz and more at 40Hz ? Cause that i cannot trade. But if we are talking about 150Hz and up, then we can talk about it.

Could you speculate as to why TCP115 has no oposition in range up to 60Hz? I mean, they could sell it for double or triple the price and still sell them. I mean i am actualy curious now so lets say all budget limit is off, it can be a 2.000€ speaker. Does it even exist ? TCP115 is insanely good in small enclosure, every other speaker i tried barely goes under 80Hz while TCP115 goes to 55Hz and could get its F3 as low as 49hz if i wanted

My newest speaker, the one i made for me, went to a photoshoot today. Didnt have time to go through all the pics yet, but just 2 to give you an idea what it looks like. Oh and if ur wondering what that sign is, its a sign of goauld system lord Kronos (stargate sg1 series )

audioguru said:

A bass boost circuit allows the very low frequencies to be at full power but the mids and highs have reduced power.
A speaker that is 8" or larger produces low frequency air vibrations that you can feel.

When I worked with Pro Audio I bought an 18" sub-woofer raw speaker that was discontinued and I got it for a very low cost. It is still brand new in its box, I never tried it. I will sell it to somebody at a car audio meet where they blow each other away with very loud sounds.

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So, what do you think about the pictures ?

I also have a question about bass boost circuit. I found several schematics and they seem simple enough, buy the components, connect them and thats that. Though to save time, i would be happy to buy some aliexpress bass boost circuit with knob, but i only found 1 for 3$ that doesn't say anything and i mean anything, no data whatsever. But it would be great to have a knob, so i can adjust the bass to the point when i hear distortion then lower it a bit.

So my questions:

1) What do you think about the pictures

2) How will my speakers handle this bass boost. Let's say for starters we do a very mild boost (i dont even know how this goes but, 3dB seems small value enough). Will they start badly distorting ?

The 750ml bottle shows that your speaker is fairly small. I am glad that its performance is good.

A speaker produces distortion when its input power exceeds its truthful power rating, I guess its coil is hitting the magnet structure. A ported speaker enclosure causes the woofer to move more at frequencies below the port/enclosure tuned frequency requiring a sharp cutoff of those lower frequencies.

I think an amplifier and speaker should have extra power headroom so that its output power is more than you will ever need so that it never produces clipping distortion.
An amplifier produces distortion when its output is clipping which is determined by the power supply voltage and the speaker impedance.
Since you want loudness then bass boost without having clipping will reduce the loudness of higher frequencies than the boosted frequencies.

Aliexpress, ebay, Banggood, Amazon and their sellers know nothing about the cheap junk they sell.

The speaker in the image is 4L and has F3 of 55Hz (that is ofcourse if speakers data can be trusted and if winISD and Qspeaker gave me the correct data). I am very happy with the speaker and so are my friends. I just got the nice dayton tweeters so i plan to replace this cheap aliexpress tweeter with it.

Sadly this speaker still has the same stereo problem. It only happened to me in 2 songs so far that actualy use stereo. But it is a bit disturbing at the beginning of song when only the tweeter is playing and since its mostly low frequencies you basicaly hear nothing. I am still waiting for those mono amplifiers and receivers, so i can actualy mix the thing into mono. But this nice little black amplifiers with volume knob are so nice, i am actualy thinking if it would be worth to figure out where on the board the signal is going into the actual amplifier, unsolder the things there and mix it into mono and then just feed mono into each channel. Would be hard though cause this thing is very small.