Dirac Live Technical Features. Impulse response correction. Frequency response correction. Editable target curve, unlimited breakpoints. Automatic target functionality. Shows all measurements. Chair, sofa and auditorium measurement. The DDRC-88A costs $999 which includes the Dirac Live software, measurement mic and software. DIRAC - Room Acoustics Software. Software to measure room acoustical parameters in the field or laboratory according to ISO 3382 (room acoustics), ISO 18233 (analysis methods) and IEC 60268-16 (speech intelligibility). DIRAC is a valuable acoustics measurement tool for field and laboratory acoustics engineers, researchers and educational.

• Dirac Room Acoustics Software Type 7841
• Dirac Room Acoustics Software
• Bruel & Kjaer Dirac Room Acoustic Software
• Dirac Room Acoustics Software

The Echo Speech Source Type 4720 is a small active loudspeaker box providing calibrated acoustic signals for speech intelligibility measurements using the Dirac room acoustics software. The Echo Speech Source is typically placed at a human speaker position. The received signal at the listener position is then picked up by a microphone and analyzed in Dirac to arrive at an accurate qualification of the speech intelligibility through parameters such as the Speech Transmission Index (STI). The Echo Speech Source operates from 4 AA batteries or an external mains power supply, and can be mounted on a standard tripod.

The stimulus signals emitted by the Echo are designed to work well with high levels of background noise. It is therefore no longer necessary to take shortcuts in generating signals with the correct spectrum and level.

Signals

One of the signals contained in the Echo is an actual speech fragment that can be used to set the volume of a PA system to a 'normal' level. The speech signal has a standard level of 60 dB(A), but cannot be used for speech intelligibility measurements.

The stimuli used for STI measurements are all MLS signals. Normally this would present a problem because the smallest difference in clock rate between source and receiver would make it impossible to properly extract the impulse response. Dirac however has been able to handle asychronous (open loop) MLS stimuli since version 4. The advantage of MLS over e-sweep signals is that the MLS is far less intrusive. The MLS can often be used where sweeps would be unacceptable. Also, because in sweeps all energy is always concentrated at a single frequency, it is more difficult for amplifiers and speakers to handle this type of signal.

With the standard impulse response technique it is difficult to measure a high quality impulse response and at the same time retrieve an accurate (background) noise level from the measurement. The new intermittent stimulus consists of an MLS sequence followed by an equally long period of silence. The full stimulus (MLS + silence) is measured in a single pass, and Dirac extracts the impulse response and the background noise into two separate channels of a .wav file. This stimulus makes it possible to increase the output level and perform pre-averaging to improve the INR of the impulse response in speech intelligibility measurements, while still retaining accurate noise values.

When the background noise level is relatively low and/or the reverberation time is relatively long (SNR * RT > 120 dBs), a simple continuous MLS sequence can be used. This signal is available at 60 dB(A) and at a raised level. Note that the MLS sequences are coded such that Dirac can always determine the Echo output level, and correct the STI calculations accordingly. For scenarios where background noise has a significant impact (SNR * RT < 120 dBs), an intermittent MLS signal is available both at 60 dB(A) and at a raised level.

The signals generated by the Echo can also be injected directly into a PA system using the BNC output connector. The electrical output always operates at the same level. You can also connect an external source to the Echo, but note that this signal will not be corrected for the frequency response of the Echo (Dirac nevertheless contains tools to perform this correction manually).

Calibration

Each Echo is calibrated individually in an anechoic room. This calibration procedure delivers unique stimulus signals for each Echo, resulting in an output spectrum that remains well below the 1 dB maximum deviation from the target spectrum as allowed by IEC 16268-16.
The output spectrum is substantially stable over time, but it is always possible to have your Echo tested (and recalibrated if necessary).

Features

• Fully calibrated sound levels and spectra.
• Reference level: 60 dB(A) at 1 m.
• 5 built-in stimulus signals.
• Adaptor for common tripods.
• External input and output.
• Compact and lightweight (10 x 10 x 17 cm, 1 kg).
• Baterry powered, 8 hrs continuous.
• Included external power supply.
• Optional protective carrying case.

Video

This video demonstrates the use of the Echo for speech intelligibility measurements.

Specifications

STIMULI
Frquency range: 125 - 8000 Hz octave bands
Maximum acoustical third-octave spectral error^* (100 - 10000 Hz bands): ±1 dB
Period time: 10.9 s
Stimulus types: Continuous Noise, Intermittent Noise, Test Voice

STIMULUS LEVEL^* (A-WEIGHTED)
Reference level: 60±1 dB
Raised level (the 2 noise signals only): 72±1 dB

INPUT VOLTAGE
Nominal (pink noise, 60 dB): 15 mV_rms

INPUT IMPEDANCE
1kHz: 10 kΩ

OUTPUT VOLTAGE
Nominal (noise signal): 120 mV_rms
Peak: 1.5 V

OUTPUT IMPEDANCE (1kHz)
Line output: 200 Ω

CONNECTORS
Input and output socket: BNC

BATTERIES
Type: primary or rechargeable 1.2...3 V
Size: AA (penlight)
Quantity: 4

OPERATIONAL TIME (BATTERY POWERED)
NiMH 3000 mAh:
Reference Speaker level, continuous: 24 hours
Raised Speaker level, continuous: 8 hours

WEIGHT
Including batteries: 1.0 kg

DIMENSIONS
W x H x D: 100 x 105 x 170 mm

^* Calibrated in anechoic room, using microphone Type 4189-A-021 at a distance of 1 m in front of loudspeaker.

Ordering

Worldwide sales and marketing are handled exclusively by Brüel & Kjær. To order the Echo you must contact your local Brüel & Kjær representative.
If you have technical questions regarding the Echo, you may contact us directly.

Summary

• Product Name: Dirac Live Room Correction
• Manufacturer: Dirac
• Review Date:February 13, 2018 00:00
• MSRP: $449.48 (2 channel), $751.06 (8 channel)
• First Impression: Gotta Have It!

Executive Overview

In equalization circles, Dirac Live has been making waves recently with their Dirac Live Room Correction software. It has already been integrated into high-end processors such as Datasat and Theta Digital, as well as luxury automotive sound systems from Rolls Royce, Bentley, and BMW. On a more affordable front, MiniDSP and Emotiva have incorporated Dirac Live into their upper-tier processors as well. In the crowded field of room correction equalization that includes sophisticated programs such as Audyssey, Pioneer’s MCACC, and Yamaha’s YPAO, what is all hubbub about with Dirac Live?

One of Dirac Live’s strongest attributes is that it approaches correction from not just an amplitude response domain but also the time domain. Many room correction equalizers measure the frequency response at a number of positions and then alter the output of the processor to fit a target curve as best as possible by simply boosting or cutting energy in regions in the measured response. This approach can only be consistently successful if the phase of the system’s response were either minimum (usually only at low frequencies only) or entirely linear, or to put that in simpler terms, that approach can only be successful if all of the outputted sound frequencies have the same respective time arrival as when it was produced. In a typical acoustic environment, this is not possible, and conventional loudspeaker design can add further impediments towards this end as well. The frequencies of the signal emitted by the processor do not all arrive at the listener at the same time; much of these frequencies arrive at the listener as a collection of acoustic reflections coming from all of the surfaces near the loudspeaker, and these reflections can cancel out or sum up with the direct sound from the speaker. These cancellations and summations can degrade the integrity of the signal.

By ignoring the time domain, conventional equalization routines can fail to address the causes of an erratic frequency response, and they can even make the overall sound quality worse by distorting important phase relationships between speakers. Changing the arrival of sound in a frequency band from one speaker in a stereo pair by just a few milliseconds can have substantial effects on the imaging and soundstage. A complete reparation of the signal in any normal listening situation involves attention paid to the time domain as well as the amplitude response domain. Dirac Live approaches the time domain by using filters to tame irregularities in the early-reflection time arrival in sound at the measured positions. While lateral early reflections have been shown to be beneficial, front and rear early reflections can be problematic. Dirac Live does not address late-reflections since they are too position-dependent to address well via processing. Late-reflections can add a sense of spaciousness, but those who do want to rid themselves of late-reflections are advised to use acoustic treatments for that goal. .

Dirac Live works by analyzing measurements made with a microphone at multiple positions clustered around the main listening position. It then finds and corrects issues in the time domain that were common in all measurements. Reflective acoustic energy can be significantly reduced in favor of direct sound, and this can give the end sound much greater clarity and less coloration. After the decay times have been reduced, Dirac Live then goes to work on the frequency response to shore up problems without damaging time domain corrections. The result is a flatter response across all listening positions with far quicker decay times.

It’s a complicated process with extremely heavy-duty mathematics involved, but the good news for the end user is that this software is very easy to use and has a simple interface. Simply select your system configuration and listening situation, and take some measurements. Dirac Live does the rest, intuitively guiding the user through the process. The next generation of Dirac Live is due to launch in Q1 of 2018 and supposedly makes this process even smoother.

Dirac Room Acoustics Software Type 7841

How Do you Get Dirac Live?

Dirac Live can come with some pre-existing hardware like the Datasat or Emotiva processors, or you can buy it as a software package for Windows or Mac PCs direct from Dirac’s website. The software package allows you to use your computer as the audio processor. It comes in two parts: a calibration tool and a processor controller. As the names suggest, the calibration tool takes the measurements and creates correction filters, while the processor controller applies the filters to sound output from the PC. The user can store any number of filters for any situation. The processor controller interface allows four different filter sets to be loaded at a time for instant switching between them. Dirac Live doesn’t just correct for room acoustics- You can equalize the response to your own taste and make your own target curves.

As a software package, Dirac Live is available in two versions: a two-channel version for stereo systems and a more expensive eight-channel version for surround sound systems. Those who want to see the software’s benefits before taking the plunge can try a trial version that does have a time limitation. Owners of the existing Dirac Live version will be able to receive the next generation of Dirac Live as a free upgrade. In addition to the easier-to-use interface that is more mobile-device friendly, the upcoming second generation will have support for multiple languages, and a new algorithm with improved analysis of stereo speaker pairs. Dirac Live is not the least expensive software solution at approximately $450 for the two-channel package and $750 for the eight-channel package, but it’s considered by many to be the most cutting-edge room correction program available. Considering the cost and time of the many tweaks and accessories that many audiophiles end up investing in, the potential for improvement that Dirac Live offers looks like a bargain for the price.

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