You are here

Electronics and Cabling

Are Genelec speakers damaged when the red light flashes or is on for a long period?

The speaker’s LED becomes red if the input stage is overloaded, the amplifiers overload or the driver protection activates.

No damage occurs in this situation. The protection circuitry protects the speaker very well from accidental overloading. However, when the red light is on, the audio signal has been modified to protect the monitor. Because of this, the speaker should not be operated so that the red light is turning on.

Can I use normal balanced analogue microphone cable to interconnect my SAM Systems and their AES/EBU digital audio input?

Analogue and digital AES/EBU cables both have the same XLR connectors. However the cable constructions differ:

Cable specified for AES/EBU has the characteristic impedance of 110 ohms and wide frequency range needed for carrying the AES/EBU digital waveforms. The AES/EBU frequency range typically starts from about 0.5 MHz and extends to about 30 MHz for the standard rate AES/EBU. This is very different from the standard analogue signal frequency range. The analogue audio frequency range is typically less than 100 kHz. Different cable materials and construction are needed for the two cable types even if both, in principle, contain a twisted pair of wires.

If you use a standard microphone cable to carry AES/EBU digital signal, you may experience unexpected problems such as quality problems in the received audio, or devices not receiving the signal properly. Problems typically gets worse with longer cable runs. It is recommended to avoid using a microphone cable and instead to use a high quality cable specified for the AES/EBU digital audio signal.

How do I connect more than one monitor to a single output?

It is important that all connections are balanced. Note: do not connect the XLR chassis to XLR pin 1, as this will compromise the RF immunity of the monitor's electronics. A typical line output can drive up to 10 Genelec monitors and subwoofers. However, this must be checked case-by-case.

 

How do I control the volume of Genelec analogue speakers?

There are many ways to control the volume of Genelec speakers. Some of the ways we recommend are:

  • "Monitor" or "main L/R" output buss level control of your mixing desk
  • monitor volume controllers
  • audio work station monitor outputs
  • power amplifier output with a passive (resistive) level attenuator

How does the input sensitivity work on Genelec speakers?

Input sensitivity can be controlled with a combination of a rotary controller and level range switches on the products. The sensitivity on SAM (Smart Active Monitoring) products can be set more precisely using the GLM (Genelec Loudspeaker Manager) software and a computer.

The nominal analogue input sensitivity in Genelec studio monitors is -6 dBu which produces 100 dB SPL audio output at 1 meter in an anechoic room.

The nominal digital input sensitivity is set so that a 0 dB FS digital input produces a theoretical 130 dB SPL sound level at 1 meter in an anechoic room.

The actual maximum SPL depends on the product capabilities and may be lower than 130 dB SPL.

How long can my speakers be on without powering them off?

As long as you want to. The idle rating for all Genelec models is very low and there is no reason to turn the speakers off every time. The ISS (Intelligent Signal Sensing) is available on most Genelec products. The ISS system puts the products in a very low power consumption sleep stage, typically consuming less than 0.5 W of power.

How to best use digital audio sources and optimise dynamic range?

If digital-to-analogue conversion is a limiting factor to convey the quality of fully digital system into high quality studio monitors, Genelec products have a dynamic range capability that is larger than the dynamic range available from any DA converter today. But in any system, any digital audio signal will finally be turned into an analogue signal to be reproduced.

For an analogue signal, there is a practical minimum and a maximum value. The low limit is the noise level in the audio system; the high limit is the distortion or clipping level of the system. In some analogue systems there is no significant distortion before the clipping occurs. In others, there is a slow increase in distortion that limits the useful signal magnitude.

The digital signal is represented by numbers. Usually the signal is represented with fixed point numbers. This means that we cannot represent fractions of values. Therefore, there is a very distinct minimum value to a signal, as well as a distinct maximum value. It is not possible to have any values outside of these ranges.

Dynamic range

The dynamic range is the range of useful values of the signal representation. For an analogue signal, it is determined by the noise level and the distortion or clipping. For a digital signal it is determined by the largest and the smallest value of the signal we can represent.

Let’s take a practical example. A typical two-way active speaker by Genelec has an input referred noise level of 3 uVrms in the most sensitive 3-5 kHz region. The maximum input signal is 1 Vrms. This is determined by the clipping limit in the Genelec speaker, not by distortion limitations, as the Genelec products have been designed to provide maximum performance with digital sources. The dynamic range of this speaker becomes a comfortable 130 dB. This is enough to render the noise generated inside the loudspeakers amplifiers inaudible in all normal listening situations. The speaker can accept a signal that has a peak value of 1.4 V.

A digital studio may process audio with 24 bit resolution. As both positive and negative voltages need to be represented, only 23 bits can be used to represent the signal value. The smallest value is represented with one bit. If we use one bit we can represent two values (0 and 1). If we use two bits, we can represent four values (0, 1, 2 and 3). If we use 23 bits, we can represent 8388608 values. Therefore, we can process the signal with 138 dB digital dynamic range.

Digital-to-Analogue conversion

The problems really begin when we want to move from digits to voltages. This is done using the digital-to-analogue converter (DA converter). As the DA converter represents an interface between the digital and analogue worlds, it is plagued with both the problems of digital signal processing as well as difficulties of analogue signal processing.

The DA converter has an analogue noise level. This sets one limit to the lowest signal that can be usefully generated with a particular DA converter.

As we make the signal smaller, we use less and less bits. This is called digital attenuation (see Figure 1). When we represent a very small signal with only few bits, we can only represent few possible signal values. This is called quantization. As we quantize to a small number of bits we are making a rather gross approximation. This approximation produces distortion. And this distortion is very disturbing, if it happens to fall to such voltages where we can still hear the signal. High quality digital audio systems take special measures to reduce the audible effects of quantization.

We can never emphasize enough the central importance of the monitoring DA converters -- after all they are the main instruments you will use to decide on the quality of your audio material. As a rule, the DA converter should be of the highest quality because the problems in it will be reflected to everything.

 

Figure 1. The effect of digital attenuation.

 

Matching the dynamic ranges

To make most of our equipment, we would like to match the digital and the analogue dynamic ranges in the best possible way. We should match the maximum voltage that the DA converter can generate with the maximum voltage the active speaker can accept.

To do this we should first check what is the maximum voltage produced by the DA converter when it is driven with a full scale signal -- at this point the digital input is said to be 0 dBfs. Use a 1000 Hz digital sinus signal to make this check. Such a signal is readily available on most test signal CD records. Turn off your monitor speakers, play the test CD and measure the peak value of the voltage present at the input to the monitor speakers using a precision voltage meter or a high quality multimeter. Let’s say that this voltage on some digital mixing console happens to be +18 dBm, or 6.2 V.

We immediately see a problem. The speaker can only accept a 1.4 volt signal. The DA converter is supplying 6.2 volts. We lose 4.8 volts of the useful signal range. This will result in two things. Firstly, the noise level in the digital system appears to be higher than expected because we are mismatching the digital system dynamic range with the analogue system dynamic range at the DA converter. Secondly, the audio signal will clip at signal levels exceeding the 1.4 volt limit.

To correct the clipping the audio engineer may take down the digital output level pot (Figure 2). This is not wise. The required attenuation in our example would be 13 dB. The noise voltage at the DA converter does not change, so it appears that the noise level is left some 13 dB higher than it should be. We have lost a total of 26 dB of the useful dynamic range because the output voltage range of the DA converter does not fall on the input voltage range of the monitor loudspeaker. We are operating with only about 74 dB of effective dynamic range, and the expensive digital console operates with the quality of a 13-bit system. We have lost 11 of the 24 bit resolution. This is clearly unacceptable!

 

Figure 2. Wrong gain matching in digital domain.

 

The right match

The output voltage range of the digital mixing console should be matched with the active monitor speaker dynamic range by using analogue attenuation or gain padding between the mixing console and the active monitor (see Figure 3).

If the output voltage is too high, then we will use a voltage divider network to reduce the input voltage to the active monitor speaker. This also reduces the bottom noise voltage of the DA converter simultaneously, maintaining the maximum dynamic range.

In practice several attenuations may be needed to optimize the DA converter dynamic range for all listening situations. There may be different settings for low and high output levels. Such an analogue gain adjustments should actually reside inside a mixing console as a part of the monitoring output DA converter.

 

Figure 3. Correct gain matching with analogue attenuator.

 

If the gain needs to be increased, we have an exceptional situation. First check that you have not missed any gain adjustment, set the output gain to maximum, and re-measure. If you are still reading smaller values than needed to obtain maximum output from the monitor speakers, then we need a very high quality gain stage. The noise level in this gain stage should be lower than the noise level of the DA converter and the monitor speaker. As this is extremely unlikely, please recheck again that you have not missed some adjustment in the DA converter.
 

I have a stereo unbalanced output - 1/4" TRS Stereo Jack - on my equipment. How do I connect my monitors?

Use the wiring shown below. It is important that all of the connections are made otherwise there could be a loss of input signal level (e.g. XLR pin 3 left floating) or induced hum (e.g. chassis ground and audio ground connected together) due to ground loops.

Note: do not connect the XLR chassis to XLR pin 1, as this will compromise the RF immunity of the monitor's electronics.

 

I have balanced outputs - XLR or 1/4" TRS Stereo Jack - on my equipment. How do I connect my monitors?

Use the wiring conventions shown below. The 2-core method is preferred over the 1-core method as it gives increased noise immunity and less signal distortion. It is important that all of the connections are made otherwise there could be a loss of input signal level (e.g. XLR pin 3 left floating) or induced hum (e.g. chassis ground and audio ground connected together) due to ground loops. Note: do not connect the XLR chassis to XLR pin 1, as this will compromise the RF immunity of the monitor's electronics.

 

 

 

I have no preamp outputs on my equipment. Can I connect my monitors to the speaker outputs of my power amplifier?

Yes and No. Do not connect the monitors directly to a power amplifier output, as the monitor's input stage will be damaged. Use the simple attenuator design shown below. Be sure to make all of the connections shown to minimize noise interference. The 2-core method is preferred over the 1-core method as it gives increased noise immunity and less signal distortion. It is important that all of the connections are made otherwise there could be a loss of input signal level (e.g. XLR pin 3 left floating) or induced hum (e.g. chassis ground and audio ground connected together) due to ground loops. Note: do not connect the XLR chassis to XLR pin 1, as this will compromise the RF immunity of the monitor's electronics.

Warning!

  • Do not use this method on bridged amplifier designs as your amplifier may be damaged.
  • Speaker wires should be used between the amplifier and the attenuator.
  • Screened (shielded) wires should be used from the attenuator to the monitor input.
  • One attenuator is required per monitor channel

I have unbalanced outputs - RCA or 1/4" Mono Jack - on my equipment. How do I connect my monitors?

Use the wiring conventions shown below. The 2-core method is preferred over the 1-core method as it gives increased noise immunity and less signal distortion. It is important that all of the connections are made otherwise there could be a loss of input signal level (e.g. XLR pin 3 left floating) or induced hum (e.g. chassis ground and audio ground connected together) due to ground loops. Note: do not connect the XLR chassis to XLR pin 1, as this will compromise the RF immunity of the monitor's electronics.

 

 

 

Is it normal that my analogue monitor red LED first light up for few seconds during power on?

This behaviour at power on is normal. The monitor red LED can be triggered by the protection circuits, an amplifier clipping condition or the amplifier thermal shutdown. During start-up it is most likely to be triggered by the amplifier clipping. The clipping is detected as a difference in amplifier input and output waveforms.

What does the overload protection circuitry do, how does it work?

The overload protection drops the level in the monitor or subwoofer to prevent overloading. Protection modifies the audio signal to protect the products. Monitors and subwoofers should not be operated so that the protection is continuously active (red light showing).

What sort of cable should I use for digital connections?

AES-EBU

Characteristic impedance: 110 Ohm
Cable type: Twisted pair cable intended for AES-EBU digital audio transmission
Connectors: XLR (male) - XLR (female)
Maximum cable length: Determined by cable losses, maximum 100 meters (330 ft)

 

Which models in the Genelec range are magnetically shielded?

Most Genelec products have drivers with reduced external stray magnetic field and are magnetically shielded. The external magnetic field varies slightly between product types.