1. Compression Driver

The most important part of a professional talkbox is the compression driver. The websites mentioned before give a few suggestions on which drivers to use, the golden standard would be the Electro Voice 1823M which is used in the Electro Harmonix Golden Throat series and was preferred by Roger Troutman. The driver was sold in the late 70s and you can sometimes still find these drivers on ebay. I decided to use the newer Monacor KU-516 driver which is also recommended in some of the tutorials online. The key specification of the driver are the frequency response, output power and impedance. For the frequency response holds, the wider the better, Moot Booxle recommends a driver that goes down to at least 250 Hz, the upper limit is fine for most drivers. Most drivers will have more than enough output power, for stage performances people usually use a mic to pick up the sound anyway. The impedance should match that of your amplifier. If your driver has a lower impedance it might actually damage the amplifier, a higher impedance will result in a reduced output power. There are several discussions online whether a talkbox can harm your teeth, cause headaches or even cardiac problems from longterm usage but, as far as I know, none of this is true. Talkbox legend Roger Troutman died at the age of 47, but he got shot by his brother which was unlikely caused by his talkboxing.

2. Amplifier

I used an amplifier that gives 18 W power at 4 Ohm with a 20 V power supply but since my driver has 16 Ohm and I am only using a 15 V PSU, the power will be reduced to <4.5 W. However, I found that that this is still more than enough and I never increased the volume to more than about half. Recommendations for a suitable potentiometer and power supply should be given in the manual of the amplifier. For the input connection it is recommended to use shielded cables.

3. Capacitor

Compression drivers can be damaged by too low frequencies, therefore, you should place a high pass filter before the driver. To construct a first-order (6dB/Oct) high-pass filter you just need to connect a capacitor in series with your compression driver. The resulting (3dB) cutoff frequency is f_c = 1 / (2pi*R*C), where R is the impedance of the driver and C the capacitance. Therefore, you should choose the capacitance according to the equation C = 1 / (2pi*R*f_c), where f_c is the lower cutoff frequency of your driver. For the Monacor-KU516 I calculated C = 1 / (2pi*16 Ohm*160 Hz) = 62 µF. Since the slope of the high-pass filter is not very steep it is recommended to choose a little bit lower capacitance than calculated so I used a 47 µF capacitor. The capacitor needs to be bipolar because it has to handle AC signals. If your an audiophile GF WORKS recommends a Mundorf MCap capacitor.

4. Tube Holder

Most compression drivers have a 1-3/8″ 18 TPI thread, living in Germany where we are using the (more reasonable) metric system, I had a hard time finding a suitable adapter for the tube. In the end, I 3D printed my own adapter for a 10 mm ID tube, you can find the STL file attached. The thread did not fit very well on my compression driver though, possibly because the driver uses a different number of TPI.

5. Tube

Commercial talkboxes have inner tube diameters between 9 -13 mm. At first, I used a PVC tube with 8 mm ID and 12 mm OD but I found that it got often blocked by my tounge. I then switched to a 10/14 mm tube but it is quite difficult to keep in your mouth. You probably have to try out different tube diameters to see what works best for you. The length of the tube should be 1 – 2 m depending on where you want to place the talkbox. Keyboarders can put the talkbox close by on the table while guitar players usually put it on the ground, hence they might want a longer tube.

6. Housing

You may find a suitable enclosure for your talkbox in an electronics store. A housing made from aluminium would provide the best shielding and reduce possible humming noise. I made my own housing from black acrylic using the laser cutter in my local makerspace. You can find the dxf file with my housing design attached.