Audio transmitter - two receivers suggestions

[thebadtall]

Hello, I intend to build a pair of wireless - totally cordless speakers, using class D amplifier on each speaker, battery and audio receiver

I will probably use fm receiver on the speakers and car fm transmitter to transmit the audio signal.
Maximum range will be less than 10meters without obstacles. Do you know how the stereo would sound in this configuration ? ( i will amplify left channel on the first speaker box and the right channel on the second speaker box )

Can you suggest me another way to achieve this goal, for instance without using fm transmitter / receivers?

Thank you

 

[throwaway18]

The main thing you can get wrong that will sound a bit odd is to have the left and right channel out of phase, ie one loudspeaker is pushing the air when the other is pulling the air. If the loudspeakers are widely spaced people don't notice.

If you use two different models of FM receiver there is a chance of the outputs being out of phase with everything else wired the same, just need to reverse the connections to one loudspeaker voice coil.

Beyond that the sound will depend on the frequency response of the loudspeakers, the box the loudspeakers are in, where the loudspeakers are placed and the room acoustics.

An alternative to radio is to use infra-red. There are infra-red headphones on the market.

 

[chuckey]

Are you going to encode you L&R in the conventional way? Its fairly complex. It could be easier to have two identical single channel transmitter and receiver.
If you have line-of-sight, then a light modulated system could be used.
Frank

 

[tony_lth]

usually people use BT to solve it, that should be very easy.

 

[Audioguru]

Are you going to encode you L&R in the conventional way? Its fairly complex.

Most car FM transmitters are stereo and are pretty good. They are used to transmit an MP3 or cell phone's music to a nearby car radio.

Since the speakers are wireless then each one will need a stereo receiver then one speaker plays left channel and the other speaker plays the right channel.
A third speaker could be a sub-woofer.

 

[thebadtall]

This is what Im thinking of

Any suggestions ?
Amplifier module is TA2020 , solar modules are 5v/100mA . Not intended to run from sun , but charge a bit the battery while its not running.

 

[Audioguru]

It looks like two FM stereo radios, not an FM left speaker over here and an FM right speaker over there.
The AR1310 receiver module has no spec's and appears to be extremely simple. Have you tried it?

Tripath went bankrupt a few years ago and their amplifiers are now made by a Chinese company. At 20W per channel with a 13.5V supply its output is severely distorted, its datasheet shows that 12W is good.

Why are you transmitting only 10m? If you use a microphone then acoustical feedback howling will probably occur.

 

[thebadtall]

This is what I have found for the 1310. I will test it as soon as it arrives and then will decide.

The specifications of the amplifier module - seller - mentions 14V max supply.
However, after a brief googling, the module board IC is yamaha YDA138. Not TA2020
Datasheet mentions


I am transmitting maximum 10m in order to use these speakers outdoors and have stereo sound. Source will be a typical mp3 player

- - - Updated - - -

usually people use BT to solve it, that should be very easy.

I have used BT in the past, in 2010 if I recall, and the sound was Terrible !
Can you suggest a bt module setup ??
I thought to use NRF24L01 (wich I am familiar about simple data transmitting and receiving) but I have no clue how to enc/dec the signal


Ive just checked some bluetooth audio link called "A2DP" and seems handy.
Do you know about signal quality ?
Also can I transmit to 2 receivers ? Or should I need 1 pair for a channel ?

 

[thebadtall]

Hello, I found out that I had a broken old car-fm-transmitter, bought around 2008 from DX
After some "retrofit" i made it work.

With 75 cm antenna it reaches through the other side of the house - 8m through concrete with very satisfying signal.
The stereo however dissapears at 1.5meter (s).
What would you suggest me to do to transmit stereo signal at 10 meters ?
Transmit mono signal at different frequencies ?
Thank you

 

[Audioguru]

The FM transmitter is made to transmit 1m from inside the car to the car radio's antenna nearby. It probably has an attenuator feeding its antenna that can be removed for a stronger signal.
Maybe the receiver module you bought has poor sensitivity.

The best range will be when both antennas are 75cm long and are parallel with the broad sides facing each other.

 

[thebadtall]

I havent found unfortunatelly any attenuation network, so i believe that its just a micropower transmitter.

I am interested in buying a BH1417 kit that found on ebay, but dont know if that too can transmit more that 2-3 meters stereo.




What do you think ?
Thank you

 

[Audioguru]

The Micromitter was a project in Australia's Silicon Chip magazine about 9 years ago then it was a kit. It had the BH1417 IC that is obsolete and not made anymore. Its RF output had an RF attenuator so that it was legal.

Your kit has its IC rubbed out! Maybe they sell the kit with a fake IC. Some parts on the schematic are not installed on the pcb in the photo. I do not know if it has the V3 RF amplifier transistor that will make a strong illegal output signal.
The two microphones are so close together that they will not make stereo sound.

 

[thebadtall]

Aha, thats not good news. I would input the audio signal through the 3.5mm fem.jack and maybe use the mic to say a hello

I will probably get a 15W fm transmitter assembled kit (RD15HVF1) for $45 to end with that thread
To transmit audio at 10 meters (killing a fly with bazooka)
Thank you very much !