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Dirac Live Room Correction

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Gojakla
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Dirac Live Room Correction

Unread post #1 by Gojakla » Sat Aug 20, 2016 1:18 pm

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Official Site


What is Dirac Live® Room Correction?

Dirac Live® is a state-of-the-art digital room correction technology that uses sophisticated analysis of the speakers as well as the listening room to optimize the speakers’ overall audio performance and to remove sound colorations introduced by the room. The result is substantially improved musical staging, clarity, voice intelligibility, and a deeper and tighter bass.


How does Dirac Live® Room Correction work?

Using a microphone to analyze the audio system and room, the software then uses this data to build an acoustic model of the listening environment and detects the deficiencies. After careful analysis, Dirac Live® corrects for both the timing and amplitude aspects of the colorations in sound to deliver a uniquely pristine listening experience.


Who is Dirac Live® Room Correction for?

Dirac Live® technology is useful for both home audio systems and professional audio applications. For instance, BMW, Bentley, and Rolls Royce use it to enhance the audio performance in their top-level audio systems; Datasat and Theta Digital use it for their high- performance cinema and audio processors; and the Dirac Live® Room Correction Suite empowers any consumer to easily calibrate their own systems without breaking the bank.


Some Technical Information

Mixed-phase room correction technology

• Using a look-ahead buffer enables impulse response correction

• Minimum-phase and linear-phase room correction filters can’t physically optimize the acoustic impulse response in a room. At best, they can minimize problems caused by the application of a filter. Room-acoustic responses are non-minimum-phase, which is why Dirac Live uses mixed-phase correction.

• Dirac Live is unique in that it improves the impulse response throughout the listening area, not just in a particular zone.


Multiple measurements

Dirac Live uses several measurement positions (typically 9) in the listening room, making it possible to accurately locate and correct acoustic problems.


In terms of the impulse response, this means optimization of the direct wave and very early reflections. Generally, at higher frequencies there is less consistent time-domain behavior. Dirac Live room correction automatically finds consistent problems in a frequency-dependent way and corrects for them. After addressing consistent time-domain behavior, there may still be some late reverberation in the room that causes subtle coloration. Dirac Live corrects these in the frequency domain to achieve just the right resolution.


Impulse response correction

A loudspeaker’s impulse response affects clarity, detail and all spatial aspects of the sound. Dirac Live is unique in that it actually corrects the impulse response throughout the listening area, not just at a single point. By focusing on consistent problems across the measurement positions and correcting only these anomalies, Dirac Live can achieve a faster decay time. Typically, the power ratio between the direct wave and the tail (later-arriving echoes) is improved by 6 dB or more, representing a vastly improved overall sound.


Frequency response correction

Why is it that the same frequency response can sound so different from room to room? The answer lies to a large extent in the time-domain aspects of the measured frequency response, as well as critical differences in the spatial (angular) domain. By addressing time-domain problems as such, and not as minimum-phase spectral problems, frequency response correction becomes more effective. After having conducted time-domain correction, we then treat the spectral colorations in a room. By paying particular attention to the variations across different measurement positions – not just the average – we can make sure not to overcompensate.


Implementation for best accuracy

• Traditional EQ uses IIR filters for lowest processor usage

• Many room correction filters use FIR filters for ease of implementation and optimization

• IIR and FIR filters both have their pros and cons. At Dirac we use a proprietary filter structure that achieves maximum performance at much less processor usage than regular FIR filters. This filter structure also has great numerical properties, and thus doesn’t produce any digital noise.


Choosing a target response

A flat frequency response does not necessarily sound neutral due to the ratio between direct and reverberant sound and the frequency-variable propagation loss. Dirac Live can’t remove late reflections, because they change too much between different positions. Therefore, a slight roll-off is often appropriate when listening at a distance. The Dirac Live algorithm suggests a target response appropriate for your listening environment and speakers, which you can of course adjust to your taste using our simple graphical interface.




_______________________________
Dirac’s digital Room Correction software supports up to 24-bit resolution at 192 kHz sample rate.
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Re: Dirac Live Room Correction

Unread post #2 by Gojakla » Sat Aug 20, 2016 1:29 pm

Σε απλά Ελληνικά και για όποιον βαριέται να διαβάσει έστω και τα βασικά points, το Dirac είναι ενα software το οποίο υπόσχεται πως μπορεί να μας βελτιώσει τον ήχο στο σπίτι μας, μετρώντας το χώρο και εφαρμόζοντας ψηφιακή ισοστάθμιση.

Διαβάζοντας διάφορα άρθρα εδώ και κεί, πείσθηκα να το δοκιμάσω.
Γιατί όχι άλλωστε? Η τελευταία έκδοση του software για Mac (version 1.2) είναι διαθέσιμη ΔΩΡΕΑΝ για 30 ημέρες.

Το μόνο που θα χρειαστούμε είναι ένα συμβατό, καλιμπραρισμένο μικρόφωνο και ένα τρίποδο για να το στηρίξουμε σταθερά.
Λίστα συμβατών μικροφώνων μπορείτε να αναγνώσετε εδώ.

Η πιο διαδεδομένη λύση είναι το MiniDSP UMIK-1, έτοιμο & καλιμπραρισμένο απο την Cross-Spectrum, στα $100 (χωρίς μεταφορικά).
Το καλιμπράρισμα του μικροφώνου είναι απαραίτητο για την μέτρηση, οπότε αν αγοράσει κανείς μικρόφωνο ακαλιμπράριστο, δουλειά δεν γίνεται.
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Re: Dirac Live Room Correction

Unread post #3 by Gojakla » Sat Aug 20, 2016 1:38 pm

Προχωράμε σε ένα απλό walkthrough του Dirac αφού έχουμε αγοράσει το software είτε full είτε σε trial.

Το "πακέτο" που κατεβάζουμε απαρτίζεται στην ουσία απο 2 προγράμματα.

1. Dirac Live Calibration Tool

Live Calibration Tool.jpg
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Το Live Calibration Tool αφορά το software μέσω του οποίου πραγματοποιούμε την μέτρηση αλλά και εφαρμογή του equalization.


2. Dirac Audio Processor

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Το Audio Proccessor είναι ουσιαστικά ο ενδιάμεσος μεταξύ του υπολογιστή μας και του DAC μας. Αυτό είναι που εφαρμόζει τα φίλτρα μας κατά την διαδικασία αναπαραγωγής της μουσικής μας.
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Re: Dirac Live Room Correction

Unread post #4 by Gojakla » Sat Aug 20, 2016 1:59 pm

As a measure to protect the software against unauthorized use, the computer must be connected to the Internet during the measurements or during the filter optimization. If the computer is not connected during the measurements, then certain parts of the optimization will be delayed until a connection is available. To save your time, it is recommended having a connection during the whole process. Any active firewalls have to allow HTTP.

Κοινώς, χρειάζεστε σύνδεση στο internet για να μπορέσετε να κάνετε το οτιδήποτε με το Dirac.



STEP #1: Sound System

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A. Choose your system configuration in the “Choose system configuration” drop-down box (A). The system configuration describes how many speaker channels you have in your system.
If none of the pre-defined configurations fit your system, then select “Custom” to freely assign up to 8 channels.

B. Select the sound card or device that you want to use for playback in the “Test signal playback device” drop-down box (B).
Use the same device and channel assignment that will be used for listening.
For Windows users: If available, the preferred choice should be an ASIO device. If ASIO is not available, or if it sounds distorted, then try a non-ASIO device (the same hardware can show up as multiple devices, depending on what audio interfaces its driver supports).

C. If a sound card is grayed out in the drop-down box, it means it is being used by another application. In this case, please close all other audio applications and press the "Rescan" button (C). Clicking the “Rescan” button also searches for sound cards or devices that may have been added after starting the Dirac Live Calibration Tool™.

D. By clicking the sample rate tick boxes (D), you can choose which sample rates the optimized filters will support. Selecting the highest rates will make the filter optimization process take longer time.

Continue to the next tab by clicking the “Proceed” button in the lower right corner or by clicking the tab itself.
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Re: Dirac Live Room Correction

Unread post #5 by Gojakla » Sat Aug 20, 2016 2:07 pm

Step #2: Microphone Configuration

This is the second tab in the Dirac Live Calibration Tool™

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F. In the “Recording Device” drop-down box (F), select the device that your microphone is connected to.

G. In the “Recording Channel” drop-down box (G), select the input channel number that your microphone is connected to. If a device shows two (or more) numbered channels, then usually
“1” corresponds to Left and “2” to Right.

H. You may optionally load a microphone calibration file by clicking the “Load
file” button (H).

Only the most expensive measurement microphones can be expected to have transparent recording characteristics. All other microphones can benefit from a calibration file to restore
transparency. The microphone calibration file is a text file that should contain the
microphone magnitude response. The file format which is supported by Dirac Live Calibration Tool™ consists of lines of <frequency, level> pairs, where the level is given in decibels (dB).

Some calibration files instead specify the calibration adjustment for each frequency. Find out if your file has this format, and if so, then switch the signs on the level numbers to modify it to the supported format.

Continue to the next tab by clicking the “Proceed” button in the lower right corner or by clicking the tab itself.


Σημείωση του γράφοντα: Στο σημείο "Η" πρέπει να φορτώσουμε το calibration file που συνοδεύει το μικρόφωνό μας. Αναλόγως του πώς θα τοποθετήσουμε το μικρόφωνο για την μέτρηση, πρέπει να "φορτώσουμε" και το αντίστοιχο calibration file.

Αν δηλαδή το μικρόφωνό μας το τοποθετήσουμε κάθετα (90μοίρες), το calibration file πρέπει να είναι το αντίστοιχο των 90 μοιρών (αναγράφεται πάνω στο αρχείο, οπότε ουσιαστικά no worries).
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Re: Dirac Live Room Correction

Unread post #6 by Gojakla » Sat Aug 20, 2016 2:13 pm

Step #3: Output & Levels

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This is the third tab in the Dirac Live Calibration Tool™

In order to get an accurate measurement of the sound system, some initial adjustments of the playback and recording levels are required. Start by placing the microphone inside the listening area.

J. For each loudspeaker channel, select the sound card output channel that it is connected to using the corresponding “Output channel” drop-down box (J).

Use the same device and channel assignment that will be used later for listening through the Dirac Audio Processor (DAP). If the assignments don’t match with DAP, then filters may be applied to
the wrong channels or audio output may even be muted.

O. The Subwoofer checkboxes (O) are only editable with the “Custom” system configuration selected in the “Choose system configuration” drop down box (A) in the “Sound system” setup tab.

K. Start playing a test noise in the selected output channel by pressing the Test button (K).

IMPORTANT: Turn down the volume on your sound system before pressing the play button for the first time and then slowly turn up the volume.

L. Adjust the levels for the recording to be within the green area on the level meter (L).

Apply a four-step process:
I. If possible, then set the sound card output level to 0 dB (usually max). Depending on the sound card, there may be a physical volume knob or a software level slider.
If the sound card driver provides level adjustment functionality, then the “Input gain” and “Output volume” sliders (M) can be used.

II. On your amplifier, adjust the volume knob to a “normally loud” listening level. Not disturbingly loud, but not too low either.

III. If the volume of any the loudspeaker channel deviates a lot from the other channels, then use the “Channel volume” slider (N) for that channel to make it more similar to the others.

IV. Adjust the gain of the microphone input in order to arrive within the green area on the level meter.
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Re: Dirac Live Room Correction

Unread post #7 by Gojakla » Sat Aug 20, 2016 2:27 pm

Step #4: Measurements

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This is the fourth tab in the Dirac Live Calibration Tool™

It is now time to acquire the acoustical models by measuring the sound system in the listening room. The accuracy of the models is very important for designing optimal room correction filters, so follow the tips below to get the best result.

Now would also be a good time to save your project before proceeding with the measurements. You can save the project at any time by clicking the “Save…” button in the lower left corner.

• Use a microphone stand to firmly place the microphone in the indicated positions.
• Use a stand that allows you to vary the height of the microphone position within the listening volume, which is important to get an accurate acoustical model.
• Minimize external noise such as talking, opening or closing doors or windows, and playback of sounds during the measurements. This is to avoid interruption in the measurement process and corruption of acoustical model data.
• Turn off any computer programs that may make any noise, such as Skype or your email client.
• Turn off any sound card effects such as “low-cut” or compression.


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P. Select the most suitable listening environment preset by clicking on the corresponding graphic (P).
In general, it is important to collect measurements in the most likely “listener’s head” positions (sitting, standing, leaning forward, etc.).

Avoid making measurements in a too small space. Even for the “Chair” listening environment, it is important to spread out the microphone positions in a sphere of at least 1 meter of diameter. A too small space will result in over-compensation that will sound very dry and dull.

Q. Place the microphone in the indicated position (Q).
The first measurement should always be taken in the center of the listening region, in the desired “sweet spot”, as this will be used for alignment of levels and delays between loudspeakers.

Direct the microphone upward, pointing to the ceiling, to get the most omnidirectional recording of the room response, or towards the speakers depending on the particular microphone and its calibration file. Please follow the instructions from your supplier.

R. Use the view selector (R) to better localize the microphone positions.

S. Press the Start button (S) to collect a set of measurements. This will play a sweep in each loudspeaker and one final sweep in the first loudspeaker again.

If the measurement was successful, then the position indicator will move to the next spot. Repeat the procedure from step 2 above until nine (9) positions have been covered.

* If your sound card or microphone pre-amplifier has a clip indicator, then keep an eye on the microphone input. If it clips during measurement, then re-take that measurement. (Usually, the clipping will be detected by the DLCT, but depending on level settings, the clipping event may fail to be detected.)

If the measurement failed, then usually an error message will be given.


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T. You can click each measurement point (T) to view its recorded sequence in the graph (U).

X. You can also delete individual measurements by clicking the red cross (X) that appears when the measurement point is marked. Doing so will allow you to retake that individual measurement.

After nine positions have been measured, there is enough data to design a set of filters.
Using the microphone positions indicated by the Dirac Live Calibration Tool™ will generally give you consistent results. However, the microphone positions are not required to be in exactly these positions - if your listening environment looks different then you may use a different set of microphone positions.

Taking all measurements close to the sweet spot will generally not give optimum performance because the microphone positions need some spread in order to acquire enough acoustical information about the room.

Don’t forget to save the project before proceeding, just to be safe.


Continue to the next tab by clicking the “Proceed” button in the lower right corner or by clicking the tab itself.
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Re: Dirac Live Room Correction

Unread post #8 by Gojakla » Sat Aug 20, 2016 2:35 pm

Step #5: Filter Design


05_Filter-Design.jpg
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This is the fifth and last tab in the Dirac Live Calibration Tool™.

The filter design algorithm uses the measured data together with a target frequency response to calculate filters that optimize the frequency response and the impulse response of the sound system. Finding the best target frequency response may require a little experimenting from your side. After completing the measurements, the Dirac Live Calibration Tool™ will automatically generate a suggested target curve that matches the measurements. This, however, can often be tweaked for even better performance.

The filter design algorithm has a hard-coded maximum gain value that limits the boost at any frequency.


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a & b. There are two ways to modify the frequency response:
i. Dragging the target frequency curve at the anchor points (a).

ii. Dragging the frequency limits on either side of the frequency range (b).

• The resulting filter will leave the audio signal unmodified in the shaded frequency regions. This can be useful if you, for example, are perfectly happy with the high frequency performance, but want to address room resonances in the bass.

• It is possible to add (or delete) anchor points by double clicking on the target curve (or on the points).

c. The zoom level is shown at the top of the graph (c).
To zoom in, draw a box around the area that you would like to zoom into.
To zoom back to the previous level, click on the minus sign next to the zoom level (c) or double-click in the graph.

i. To view the impulse response of the system, before and after correction, click on the “IMPULSE” button (i).
In the impulse response view, this button will change its label to “SPECTRUM” and clicking on it will take you back to the frequency view.

d. It is possible to set a target curve for all channels at once, a linked group of channels, or one channel at a time. Use the channel tabs (d) on the right side of the plot area to change the grouping configuration.

i. Clicking on the chain symbol of a channel tab (e) causes the channel to detach from the linked group and showing the detached channel’s curve in the plot area. You can also drag and drop to unlink.

ii. Dragging and dropping a detached channel tab onto a linked channel tab causes the detached channel to join the group and show all the grouped channels’ curves in the plot area.

f. Press Optimize (f) to create a set of filters.

g. When the optimization has completed (this may take some time depending on the speed of your computer and how many sampling rates you selected to make filters for), press “Save Filter” (g) below the target editor to save the filter to a file that you will be able to open in the Dirac Audio Processor™.

To be able to load the filter in the Dirac Audio Processor™, make sure to save it in the default directory suggested by Dirac Live Calibration Tool™.

* To design a new filter for the same sound system, repeat the procedure from step 1 above. To design filters for a different sound system, then go back to the Sound system tab.

j & l. Saving a project once a target curve has been set will save the state of the target curve in the project. If you are testing several target curves it may be a good idea to save each target with the Save Target button (j).

This will allow you to revisit and tweak the target curves from which a specific filter has been generated by loading them with the Load Target button (l).
Loading a target will apply it to the currently visible channel (group).

g & h. Please note that there are two save buttons with different functions, one for saving the filter “Save Filter” (g) and one for saving the project “Save…” (h).
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Re: Dirac Live Room Correction

Unread post #9 by Gojakla » Sat Aug 20, 2016 2:41 pm

Και κάπου εδώ τελειώνει το Calibration Tool Walkthrough.

Ουσιαστικά τα πράγματα είναι πολύ πιο απλά από όσο δείχνουν.
Για ένα τυπικό δικάναλο σετάπ, αυτά που πρέπει να κάνουμε/προσέξουμε είναι:

• Επιλέγουμε το σετάπ μας και τις επιθυμητές δειγματοληψίες στο step #1.
• Επιλέγουμε το μικρόφωνό μας και φορτώνουμε το σωστό calibration file στο step #2.
• Προσέχουμε τις στάθμες στο step #3.
• Ακολουθούμε τις εύκολες οδηγίες τοποθέτησης του μικροφώνου στο step #4.

Αυτά είναι όλα κι' όλα τα 4 βασικά που πρέπει να προσέξουμε πριν ξεκινήσουμε την μέτρηση.
Εμένα που είμαι πολύ αρχάριος δεν μου πήρε πάνω απο 10'.


Το "παιχνίδι" αρχίζει στο step #5 όπου η όλη ιστορία είναι δοκιμές, δοκιμές, δοκιμές, δοκιμές, δοκιμές.... :mrgreen:
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Re: Dirac Live Room Correction

Unread post #10 by Gojakla » Sat Aug 20, 2016 2:49 pm

Αφού κανείς τελειώσει με τις μετρήσεις και εφαρμόσει τα φίλτρα του, πρέπει να τα σώσει. Όσα θέλει. Οι δοκιμές δεν έβλαψαν κανέναν.

Στο Audio Proccessor δεν θα επεκταθώ πολύ, όποιος θέλει να διαβάσει όλη την διαδικασία εκτενώς (και του Calibration Tool αλλά και του Audio Proccessor, κατεβάζει το manual -> εδώ)



"Ανοίγουμε" λοιπόν το software.

06_Audio-Proccessor.jpg
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1. Κάθε φορά έχουμε τη δυνατότητα ON THE FLY είτε να "κλείνουμε" εντελώς τα φίλτρα είτε να τα εναλλάσουμε μεταξύ τους.

Κάθε φορά μας επιτρέπεται να φορτώνουμε εώς και 4 φίλτρα ταυτόχρονα.
Απλώς πατάμε πάνω στο πεδίο "Click to Load" και επιλέγουμε το φίλτρο μας.
Απο το εικονίδιο του κάδου, μπορούμε να το σβήσουμε και να φορτώσουμε κάποιο καινούργιο κ.ο.κ.

2. Απο το "Output Device" επιλέγουμε το DAC μας και... καλές ακροάσεις!
Μόλις ανάψει η ένδειξη πάνω δεξιά στο "streaming", είμαστε live. [musicphones]




Καλό (και ασφαλές) παιχνίδι! [wavegreen]

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