Cheap Wireless Microphone Systems

In the past, we had little choice but to use units from Shure, Sennheiser, AKG etc. if we wanted to use a wireless microphone system. Today these companies make very advanced wireless systems, even digital and encrypted systems. The cost of these sysems can go up to 6000€ for a 2 channel system. Although you can get cheaper models from same manufacturers, usually these models have restrictions on number of channels which can be used etc. These high prices are not surprising, since these companies have to divert most of their profits towards advertising and distribution. If a product is found in every store and its name is mentioned everywhere, people tend to associate with it easier. It is normal behavior to be weary of a product which you never heard of.

But... can we meet in the middle and get reasonable amount of features for a reasonable price? I will focus on units which can be found at AliExpress site. Today, it is possible to even find cheap units with digital transmission and rudimentary encryption at AliExpress.

While no doubt that you may get the best audio quality with a 6000€ unit (3000€/channel). Do you need to pay that amount if you can get a 300€ unit (75€/channel) which does the task you require?

In the final unit I chose, I couldn't find any audio artifacts while in operation. I showed the unit to few musician friends and they seem to think that it sounds fine also. This is never the less not a very scientific method, but if you can't hear the difference I am not sure if it is worth paying so much.

Unit Selection Highlights

There are so many models and brands, they all promise to be the best. How to choose?

Frequency Range

First of all, you must filter your choices by frequency. Most units sold on AliExpress have frequency settings which are totally unacceptable. The used frequencies are not in the free range in Europe, North America or even in China. I have discussed this issue with some sellers and learned that we can blame India for this. Apparently Indians want it this way, although I found out that those frequencies are not even the allocated wireless microphone frequencies in India. Never the less, you must complain to unit producer if you find a nice unit you want is in wrong frequency. This way, eventually they may start producing units in legal frequencies.

For example, currently in Finland the following frequency ranges are available for microphones:

174–230 MHz (TV-VHF)	No licence required as from 1 January 2017
470–694 MHz (TV-UHF)	No licence required as from 1 January 2017
823-832 MHz	No licence required
863-865 MHz	No licence required
1785–1804.8 MHz (UHF)	No licence required

One important thing to mention is that it is not enough to operate a device in this range. Another restriction is that the user must NOT be able to set the device to any frequency outside these ranges. Otherwise device would require license or may be illegal to operate.

So, we already filtered out a bunch of systems.

User Manuals

I found out that user manuals give so much better feel of a system than just looking at its photos. This may not be same feeling for you. Also most sellers seem to say "it is easy to use, no need for manual". But the features and capabilities of the system give me an understanding of how much attention to detail was given and how advanced the system is. One other thing is that on AliExpress most sellers copy/paste specifications of systems. You get to the bottom of it by receiving manuals. Another thing is that the sellers tell whatever to sell you the device. Manuals usually give more truthful information about the operation of the device.

Beltpacks 3.5mm or Mini-XLR or With Volume Control

This mostly interests beltpacks. There seem to be two different types of beltpack connectors used in these systems.3.5mm screw locking or mini-xlr. While the mini-xlr may seem more advanced, all the chinese units use only pins 1 and 3 in these units. In addition, some units have the mini-xlr port connected upside down! meaning you get signal in pin 1 and ground in pin 3. If you choose an XLR beltpack system then you would need to make sure to ask the seller that the pins are not reversed. Otherwise this may effect microphone performance.

On the other hand, Chinese sellers will NOT recommend you 3.5mm units if you want to use instruments with them. The reason is not because these units do not work well with instruments, but it is simply difficult to produce cables for instruments with these units. The chinese 3.5mm screw lock solder plugs are very difficult to work with due to small soldering area on the connector.

The 3.5mm version beltpacks use mono jacks. While some headsets come with stereo plugs, only the tip and sleeve are used. One nice feature is that these 3.5mm units often come with volume control so one can reduce the volume. But then, I didn't have any occasion where very high volume was a problem, even when a guitar with pre-amp was connected. It feels like they seem to have some sort of auto gain control. So far, I did not find a good use for the volume setting.

If you stick to headset/lavalier microphones then the 3.5mm would be quite reasonable choice. But if you want to use instruments such as electric guitar, then you would need to produce your own cables. For example the sennheiser cables would NOT work because their guitar cable uses ring/sleeve for transmission.

Digital or Analog

The digital units of course would have superior resistance to interference but I tried two units and they seem to have some problems. One super cheap two-channel unit had some background noise. I can't tell if it was my unit which was faulty. Because some other buyers seem to be perfectly happy with the unit. I did not make further tests with this unit, I should have tried to figure out what was wrong with it but ran out of time.. I am putting photo of the unit I had below for two reasons. 1- To not generalize a perhaps local problem. Not all digital units may have this problem. 2- You may put comment if you have this unit .

UPDATE: I have bought another of this unit from a different seller and the new one was ever slightly different inside. I believe they had a revision update and fix the issue. One must ask seller to test the unit before shipping.

Inside looks like this

I also got a one channel digital transmission unit. As a matter of fact, the beltpacks of these units have exactly same hardware but they work in different frequencies. In this unit the problem was some sort of strange shift in the frequency at first. When I tested with a guitar, it changed the frequency a very small amount (tested with an Android app from my phone). But I found out that this is because of a squeal avoidance function (not sure how this change in frequency is going to help). Below is the photo of the unit. Otherwise it works pretty well.

Inside looks like this. Surprisingly little space is used in it!

Using Instruments

Normally the more expensive units provide a different cable connection for instruments due to difference in impedances between for example microphones and electric guitars. However, in my tests I had no problems whatsoever when using the same microphone input. There was no distortion in the audio. I tested both guitars with pre-amp and without. Your mileage may vary if you are using instruments but with units which has volume controls, you can always lower volume if you encounter distortion. The problem is that the volume of a high impedance instrument will be too high for a low impedance input. But in all cases the units seem to adapt to it perfectly.

Unit "Without" Faults (IMHO)

I myself settled on a 3.5mm beltpack unit eventually. Bought from a company called boyue international on AliExpress. They have a web page also called BolyMic. One of the reasons was this unit had an amazing manual, volume control on beltpack, radio transmission power control, automatic best frequency finding, transmitter battery status could be seen on receiver. I felt the XLR units were somewhat not ready for prime time.
 

The picture below is not to scale

In either case, the unit looks amazing in the rack. I also liked the cool magnification effect on the handheld display glass. The microphones are metal and very heavy. Range seems fine, so far I could not find a place where it won't reach far enough but then I did not test to the distance that seller claims which is 150M.

They could have gotten away with using only 2 antennas. Also, the unit is a diversity unit, but I believe it is not the so called "true diversity" which do combine signals from antennas. It gets little bit warm, but not more than my laptop so I guess that can be considered normal. One last thing is that the handheld does NOT have volume control, there is an error in the manual in that area. There is no MUTE button on transmitters, but unit mutes channels automatically if you turn off the transmitter. These are the areas where unit can be improved in my opinion.

Below are photos from the insides of the beltpack and the handheld (last picture) microphone

Also some pictures from inside the receiver

Now the manual pages for your information

Car Door Laser Logo Projectors Modding

It is possible to buy courtesy light replacements with logo projection from AliExpress for less than 10€. While some of them mention the word "laser", they are actually based on high power Cree LEDs.

If you are buying these lights, I highly recommend opening them up and have a look inside. In my case the LED module was not glued to the heatsink. I had to use adhesive heatsink paste to glue the LED onto the heatsink. The glue I used was sold as "Thermal Conductive Heatsink Plaster". You can see the plaster under the led module in the picture above.

I also found out that the LED driver is set to give out 500mA constant current and this roughly equals to 5W in this case. This is simply too much power and causes LED to get too hot and burn out. When I was working in the car, I left the door open for a long period and this caused Cree LED to burn out. The LED driver is a pretty small module and the current output can be changed by replacing a SMD resistor. I didn't have SMD resistors so I found a replacement module which gives about 300mA output. This module sold as MR16 3W LED Driver. Of course the brightness went down about 20% but the LED module is not getting too hot anymore (at least it will take much longer time for it to get to a critical temperature)

In addition, I didn't like the fact that these replacement courtesy lights only point downwards and they do not have the red light warning for incoming cars. So I have embedded two red leds in parallel to the Cree LEDs. You will need to figure out which size resistors you need or use special LEDs if you do this. I found out some strange LEDs which could be wired directly to 12V. They work reasonably well in this setup because Cree LED's input floats getween 3V - 5V.

One last thing to mention is that usually these items come with no real connectors. Only some models of them are with real connectors. While you can just slide the provided pins into the connector of the car. They will simply get out in time and it does not look safe at all. I have found out some connectors which were exactly same as on my original courtesy lights on AliExpress and crimped them.

Here is what the end result looks like, powered from portable lead acid battery.