radio station requirements, although it is generally good enough to pro-
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Compressor tect recorders and monitors, where the effect of transients is less critiThe hardest device to understand, yet one of most useful, the PhotoOptical Compressor is what gives Joemeek products their unique 4. Accommodation character. Its job is to make quiet louder and loud sounds quieter, The dynamic range of the human ear is phenomenal, extending from or in other words to reduce dynamic range of the programme material. the threshold of hearing (eg: a pin dropping onto soft carpet) to threshIt�s a bit like manually riding volume control, except the compressor old of pain (eg: standing next to a jet aircraft) some 120dBA in all. By does it automatically, responding far quicker and more accurately than you contrast, vinyl, cassette tape and radio broadcasts all have a dynamic ever could by hand. The compressor is applied in several ways: about half that. Since advent of CD, the dynamic range 1. Make Sounds Stand Out give certain �feel� to a production. AM and FM radio however, is still Because compressors make loud sounds quieter, you can boost the volume very much compressed to fit its restricted dynamic range. of quiet without the loud bits getting even louder. That means you can raise average level of an instrument or vocal in the mix, which has 5. Modification the effect of lifting and bringing it forwards. This can actually improve A compressor can change dynamics, or �envelope� of the track and vocals for example, bringing out in front of a mix, making them sound it is here that the Joemeek Compressor excels! denser, even, and more confident! 2. Crank Up The Volume Most compressors work in essentially the same way: a volume-conRaising the average volume of whole mixes means they can be heard in trolling element or �gain cell� is inserted into the audio signal path. noisy environments, such as vehicles and factories. Boosting the average The level of the signal at any given moment is measured and that level what makes radio stations sound LOUD and the same technique is information is used to control gain cell. So if the signal gets bigger, used on TV commercials too, which is why they always seem annoyingly the volume is turned down. Various types of gain cell in common use louder than the movie you were trying to watch! include FETs, valves (tubes), light-dependent-resistors (photoelectric), 3. Protection as VCAs. Fast response times are generally used to control brief transients. In other words if an occasional peak sticks its head above a maximum permitted The threeQ Compressor is a unique recreation the sort of photolevel, the clobbers it; this is known as limiting and a compressor electric compressor used by record producer Joe Meek in the 1960�s. designed solely for this purpose is known as a Limiter. Limiters are primarily Using modern components for consistency and reliability, it used to protect recorders and monitor systems from overload, radio transnonetheless reproduces faithfully the same punchy sound that was mitters from overmodulation, etc. The Joemeek compressor is not primarily so characteristic the pop records of that time. intended for this purpose as the Attack is not really fast enough to satisfy digital potentiometers and voltage-controlled-amplifiers, better known Types of Compressor the medium is far less of an issue and compressors are used more cal. Normally you should not hear a limiter operating but if it is driven hard constantly, it can render a mix somewhat flat and lifeless.
Compression Ratio output only increases by 5dB then compression ratio is �2 to 1�. If the threshold. Turn this control anti-clockwise for a quick response. Slower input 10dB but output only goes up 1dB, then compression (clockwise) allows the fast leading edge of percussive sounds to pass any size signal above threshold but for that to be true, gain gain. This example �changing the envelope� of a sound exagcell its control circuitry must be perfectly linear over a very wide range. gerates the percussive nature of drums and other instruments. Faster likely behave in this way. less obvious. For vocals the Attack needs to be around 1msec Some compressors have a control to set the ratio anywhere between 1:1 (ie: no compression), and 20:1 (which would be regarded as a �brick wall �RELEASE� sets how long compressor goes on squashing the limiter�). In threeQ �Slope� or �Compression Ratio� is fixed at 5:1. sound for, once the signal has dropped below threshold. If it stopped hard enough for drums guitars. However that�s not all there it. the sound. So we want it to stop compressing less abruptly and that is Variable Ratio less obvious is the compression. Of course some �pumping� might In Joemeek optical compressor the compression �threshold� not actually be desirable as a special effect and that is another way in clearly defined and compression ratio varies with amount comwhich the envelope of a sound can be modified. The threeQ Release is pression applied. For signals only just exceeding threshold, the ratio is little variable from 100mS up to 3 seconds giving a wide variety of effects. more than 1:1. As compressor is driven harder, the ratio rises to 5:1, at pression ratio actually reduces again during large transients and, adjusted tent and volume. So experiment the controls with different kinds correctly, this helps retain brightness is often lost with other types material to discover the range and depth of effects that can be their modern counterparts. pressed and uncompressed sound (green LED lights when active). �COMPRESS� sets level of signal (the �Threshold�) above which before the Meequalizer. signal starts to be compressed. Turning the COMPRESS control clockwise lowers compression threshold, and drives the compressor harder.
�ATTACK� sets how quickly compressor reacts to peaks above What?? OK, it�s simpler than it sounds. If input gets 10dB louder but the uncompressed for moment, before compressor reacts control �10 to 1�. In a theoretically ideal compressor, this ratio is the same attack times (anti-clockwise) used where the compression needs In practice only compressors based on VCAs and digital potentiometers are for a natural sounding result.
instantly there would be very noticeable modulation or �pumping� of This is a good compromise between being gentle enough for vocals and what control is for. Generally, longer the Release time,
How behaves actually changes with programme conleast up to point. It is a feature of Joemeek compressor that the comachieved. The �COMP� in/out switch allows comparison between comcompressor. This is why vintage compressors often sound more lively than The Compressor is after Preamplifier the Insert Point, and Controls
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