Bluetooth speaker retrofit

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Hi All, I hope I'm in the right forum. I got a Cambridge Soundworks Center channel speaker for free, and I thought it would be fun to make it a built-in stand-alone bluetooth speaker. Most of the chip amps I've seen have two channels, a left and a right speaker. This center channel has two midrange, apparently wired in series, and one tweeter and they connect to a crossover (I guess?). How do I wire the speakers to the 2-channel amp with one tweeter? Do I use the crossover somehow, or eliminate it? Any other advice you can give me? Thanks all!
 

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Many cheap BT module/amp board uses JL (JieLi) chip or Beken chip.
It doesn't hurt to get one for a few bucks to test with.
But if more serious making your own BT speakers, I would suggest to use Qualcomm QCC or CSR chip to have AAC and AptX support. If can't find a mono amp board with Qualcomm chip, then separate the amp board and BT module.
 
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Thanks for the replies everyone. I'm assuming having an amp with two channels instead of just one would be stereo, which I'd like to maintain if possible to make it sound better. I assume I could potentially lose some sound if the recording I'm listening to has separate sound coming out of one channel or the other, like a lot of Beatles recordings for example. What if I eliminated the cross-over, and wired it up to a two channel amp like the attached diagram? Assuming this would be a good way to go, can someone help me with the additional components I would need for the inducters and capacitors described, and how I would wire them up? I'm having a hard time finding the specs of the speakers themselves, if that's needed.

Sorry, I'm a noob when it comes to the details of audio, but I know electronics relatively well, and I can solder, so I want to learn how this all works.
 

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Your idea is no good.

Many D-amps do not like to be connected to a capacitive load like your tweeter shows. So the tweeter channel will run hot or even fail.

Your mono/stereo theorie does not work. One speaker mono, two (or more) stereo, that is the world. Sorry.

At last, there is no way to do a decent passive x-over without a lot of practical measuring. So just choosing some part´s values will not sound any good. No way just to take some formula and you are done. Sorry again. Read about constructing passive x-overs and then you might understand.

You have one speaker with a good x-over, so fit a mono amp to it and you are done. Will be the best you can get.
 
Ok, thanks Turbowatch2! Great info. A mono amp it is. Regarding stereo vs mono, if I'm using a mono amp, is that like listening to either the right channel or left channel in a stereo setup? Thus, could I be missing audio that's for the 'other' channel? If there's a trumpet in the left channel source, and I'm using a mono amp, would I potentially not hear that trumpet? Or is Mono a combination of both channels together?

The specs for the speaker (as a whole) says it's 20 watts. So if I understand correctly, if I push more than 20 watts through it, I'll likely hear distortion, right? Should I stay 20 watts or below?
 
I've looked and looked and I can't seem to find a mono (which I think is PBTL) board that's around 30W and has bluetooth onboard. Is there a reason I can't find one, like I'm barking up the wrong tree or something?

It seems it might be possible to mod certain 2-channel boards (with Bluetooth and the right wattage) in PBTL mode. You essentially bridge the left and right channels then connect the speaker to the + of left channel and - of the right channel. DOes anyone have more info on this, or can suggest a board that can support this?
 
Or might be get an amp board and a cheap Bluetooth board like this to start with and you can always upgrade to a different Bluetooth board when you want better.

Bluetooth Audio Receiver board Bluetooth 5.0 mp3 lossless decoder board Wireless Stereo Music Module-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
(it requires 5V power. Even masked in picture, ACxxx on the chip is JL chip)

If you want a better one that cost much more
CSR8675 Bluetooth V5.0 Decoder Board PCM5102A Low Power APTX/APTXLL/APTXHD Lossless I2S-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
 
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Thanks Mcdull. If I go that route, would this work:
This bluetooth board (or something similar) with this amp board.

The first issue that jumps out at me is the output on the Bluetooth board is LRG, where as the input on the amp board just has LR. Can I/should I connect the ground from the BT somewhere? Next, is power. This particular BT board takes 5-24V and the amp 8-24V. So can I safely just split the power from the AC pwr supply to the two boards?

Also, on the amp board, what are the two connectors labeled MUTE? Is that where a volume potentiometer would go, or does this board not have a pwr/volume control?
 
I have tried one bluetooth mono amp, and I was surprised that it actually played only one channel sound, not L and R. It can be quite annoying to listen with some music :D at that point I decided never ever again use those.

I've had good results with this bt-board: CSR8645 APT-X HIFI Bluetooth 4.0 12V Receiver Board for Car Amplifier Speaker | eBay
You can simply combine the L and R channels with one (1k I think?) resistor in each channel, and then the other ends can be connected together.
That board also has DC-DC isolator, that can be useful when connecting multiple devices into same power supply.

That TPA3118 board would be my recommendation. It does not have LR input, only square and round pads. The square is the signal wire and round is ground.

Yes, you can use the same power supply for both.

That MUTE does what it says, it mutes. If you want a volume potentiometer, you connect that between your bt and amp board.
 
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So I guess the reason I can't find any bluetooth MONO amp boards is because bluetooth boards or circuits have an LRG (TRS) output, whereas the AMP only supports Mono (one channel), right?

You're proposing I connect a 1000 Ohm resistor on both L and R, and then I can combine them together like the attached pic? So I guess L/R would go to INPUT+(square) and G to INPUT- (round) on the amp board? If that's the case then I'm all set!!

One other thing: My speaker is rated at 20watts. What is the best sized power supply to get?
 
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Did I describe how to implement the resistors and combining the L&R signals correctly?

As for DC input voltage, my speaker is 8 ohms and 20watts, so if I use a pwr supply that's 12v, 2Amps, w/ 8 ohms resistance is 24 Watts....is that the right way to do that? What would happen if I pumped 24v & 2amps, thus 48Watts through the speaker? Would the sound be crazy distorted? My goal is to make it as loud as possible without any distortion.
 
Yes, that diagram is correct.

It would be better to overrate the power supply. If you have higher voltage and amps, they won't "pump" the amplifier in any way. Amplifier takes the power it needs from the ps. And there is no harm done, even you connect a 1kW amplifier to your speaker, you always attenuate your signal to your needs. Overpowered amplifier usually has less distortion, because there is headroom.

If you are on a budget, seek for old laptop ps bricks, they usually have 19 volts and 3-4 amps and are cheap.
 
As for DC input voltage, my speaker is 8 ohms and 20watts, so if I use a pwr supply that's 12v, 2Amps, w/ 8 ohms resistance is 24 Watts....is that the right way to do that? What would happen if I pumped 24v & 2amps, thus 48Watts through the speaker? Would the sound be crazy distorted? My goal is to make it as loud as possible without any distortion.

It also depends on your amp chip, it's not that you have a 48W PS then you can get 48W. e.g. the TPA31xx series in PBTL, you get 25W using 12V but can go more if using 24V

TPA3118D2 datasheet(12/34 Pages) TI1 | 15W,30W,50W Filter-Free Class-D Stereo Amplifier Family with AM Avoidance
 
For a BT speaker, you need two tweeters and one or two woofers. You can combine the bass, but not the highs unless you go mono, which others are suggesting. Note that you can buy a BT adapter and wire it to a mono amp. But as you have found, amps with BT will be 2.0 or 2.1 channels. You could replace both woofers with two full range speakers and block the tweeter hole but that sort of defeats the purpose.


Note that while a class D amp can be 90% efficient, a class AB amp will be 60% at best. The power calculation depends on whether the amp is bridged or not. A bridge amp doubles the voltage to the speaker so the supply is twice the current. The undistorted power is half the peak power and the peak power is half the voltage (bridge=1x) less about 2V saturation voltage squared divided by the load impedance.
So 24VDC and 8 Ohms means 11*11/8/2 = 7.5 Watts or 30 Watts bridged. Car stereos are usually "22 Watts" ie 13.5x13.5/4/2 assuming a 14+V battery. This is why auto speakers are always 4 Ohms or less.
 
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