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Bluetooth speaker retrofit
Bluetooth speaker retrofit
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Old 25th August 2019, 06:30 PM   #1
jlatenight is offline jlatenight
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Default Bluetooth speaker retrofit

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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Old 26th August 2019, 12:18 AM   #2
Turbowatch2 is offline Turbowatch2  Germany
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Use a mono chip amp.
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Old 26th August 2019, 03:52 AM   #3
Max Headroom is offline Max Headroom  Australia
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Ebay Mono Bluetooth Amplifier


Dan.
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Old 26th August 2019, 05:49 AM   #4
mcdull is offline mcdull  United States
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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.

Last edited by mcdull; 26th August 2019 at 05:54 AM.
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Old 26th August 2019, 02:05 PM   #5
jlatenight is offline jlatenight
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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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Old 26th August 2019, 07:52 PM   #6
Turbowatch2 is offline Turbowatch2  Germany
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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 partīs 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.
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Old 26th August 2019, 09:15 PM   #7
jlatenight is offline jlatenight
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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?
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Old 27th August 2019, 12:11 PM   #8
Max Headroom is offline Max Headroom  Australia
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The mono output amps like in the Ebay link I posted are L+R sum to mono so no information pr channel is lost.
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Old 27th August 2019, 03:11 PM   #9
jlatenight is offline jlatenight
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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?
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Old 27th August 2019, 06:10 PM   #10
mcdull is offline mcdull  United States
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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

Last edited by mcdull; 27th August 2019 at 06:28 PM.
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