Hardware and software for making demo videos

A new venture for me.  I need to make some videos to show how to use my professional software. This means that I need to be able to capture my computer screen and for me to do voice-overs.

You would think that Adobe Premiere Elements could do this, but no, you have to buy an expensive add-on (called, I think, ‘Captivate’) designed for people who are producing professional on-line teaching aids and courses. But it incorporates all sorts of features that I really don’t need, at least for now.

Screen capture software. I searched around for screen capture software and after quite a bit of research,  came across OBS Studio, which is a free screen capture and streaming program.  I’ve never thought that I would be into streaming, as I didn’t think it would ever be practicable for me, but perhaps that will change in the near future.

OBS Studio. I managed to download and install OBS Studio without any problems, and to record a test demonstration of my software, but I have had trouble in the past with decent audio, even with good microphones.

Microphones. In my professional work, an accurate microphone costs £1000 and that doesn’t include pre-amplifiers and other accessories, although the microphone will come with a calibration certificate and a flat frequency response of 6 to 20,000 Hz.  Of course this is completely over the top for voice work, where a range of 340 to 3400 Hz would be OK for clarity.

So I searched for ‘streaming’ microphones and of course there is a vast range.  In the old days, cheap microphones used a quartz piezo-electric crystal.  These have the advantage that they generate a high output voltage without needing a pre-amplifier, but they have an irregular frequency response.  Dynamic microphones are basically like loudspeakers in reverse – a diaphragm vibrates a coil between magnets, generating a voltage in the same way as a dynamo. They also produce a high* output voltage, but they are delicate – the voice-coil suspension can be damaged if they are dropped or knocked.  So condenser microphones have become popular.  Here the diaphragm is a thin sheet of metal or metallised plastic stretched over a frame and place very close to a metal back-plate.  An electric charge (a voltage) is put across the two and this is connected to a ‘charge’ amplifier which has a very high input impedance.  The two plates of the microphone act as a capacitor, or condenser in old terminology, and as the diaphragm vibrates, the capacitance changes accordingly, so that the voltage on the amplifier changes.  This is amplified to a value suitable for the recorder input.  At one time, the electronics were difficult and expensive. Ideally the amplifier needs to be close to the microphone, within the same housing.  I still see references to a ‘tube’ (i.e. a thermionic valve), used due to their high input impedances, but MOSFET transistors can have equally high input impedances, and I don’t see why anyone would use a ‘tube’ now.

*all things are relative – we are talking about millivolts!

To cut this long story short, I researched a suitable microphone.  I want something of adequate quality, and was totally disappointed by a lack of technical details on most of the products. Hardly any of the specs discuss the microphone technology, the frequency response or output level.  They all say silly things like ‘professional’, ‘high-definition audio’ (I still have no idea what that could mean).

USB Microphones. So I found two USB microphones that seemed possible candidates.  USB microphones are usually of the ‘MEMS’ (micro-electro-mechanical systems) type commonly used in mobile telephones.  Essentially, this is a condenser microphone fabricated on a silicon chip and directly connected to a special chip containing amplifiers and an analogue to digital converter.  These process the output into a digitised signal,   These can have excellent quality because the A/D converter can be optimised to the characteristics of the microphone cartridge and the required frequency response, and because the connecting cable carries a digital signal, it is fairly impervious to noise pickup. It doesn’t need to be impedance or voltage-matched to your sound card.  Only a few years ago, this would have made the microphone expensive, but nowadays specialised integrated circuits can be remarkably cheap.  They do require a power supply, but the USB connector can provide this.

My choice. The two I have bought – yes, I have ordered them and awaiting delivery – are KLIMTM Talk, which claims it is ideal for Skype, VOIP and other audio calls, and cost £24; and Blue Yeti, which claims it is for recording and streaming.  This is a condenser microphone with three capsules and an adjustable directivity pattern and gain control. It cost £85.  This does seem like a good specification – we will see.

My initial testing shows that both give excellent sound quality. The more expensive Blue Yeti gives a more ‘spacious’ sound but is more sensitive to ‘mouth’ sounds, whilst the KLIMTM has a more ‘dry’ (less spacious) sound and seems less affected by ‘mouth’ sounds.  It’s not possible to say at this stage which one I like best – they are both suitable for doing my voice-overs. I will make a more detailed review in my next post.


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