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This guide shows you how to produce a full width front stage plus concert hall ambience as described by Ralph Glasgal in The Science of Domestic Concert Hall Design article. The use of JRiver is an alternate solution allowing more audiophiles to experiment using their existing audiophile system. Convolution, when properly implemented as described here, brings the acoustic characteristics of St. Cecilia hall to your listening room. You will hear the full 2.2 seconds reverberation of the hall. It recreates concert hall ambience using specially recorded 360 degree impulse responses (IRs) of the St. Cecilia concert hall. In this guide, I will show you how I implemented these IRs using JRiver. My solution may not be the best but it opens the door to unlimited possibilities for tweaking the sound to match your preferences and can provide a lifetime of sound to enjoy

You can read more about the importance of convolution at the ProAudiofiles site.

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Requirements:-

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1) PC with i5 and above. 8GB RAM Memory.  Please see OS requirements for JRiver. However, AmbiophonicsDSP VST plugin works with Windows OS only. For other OS, you have to use the MiniDSP with the Ambiophonics plugin.

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2) USB DACs. One is required for every IR. In my case, I have convolved IRs for left and right speakers placed at 60, 75, 90, 105, 120, 135, 150 and 165 degrees. Therefore, I am using 8 DACs for surround ambience alone.  My choice was the PCM 2704 DAC which can be bought for about $10 from Ebay. AudioQuest Dragonfly is another good choice for better sound quality.  You can use any DAC brand but it is advisable to use identical DACs for all the surround speakers. The most cost effective solution is to use cheaper ones for the convolution channels and a better DAC for the main front speakers.  I use Mytek 192 DSD DACs for the main front channel and the PCM2704 for the rest.  You can also use multichannel audio interfaces such as RME, MOTU 24AO or Focusrite to replace the DACs.

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3) One stereo amplifier  for each DAC. You can use small amplifiers as the convolved surround speakers need not be played loud. I use Line5 A960 amplifiers (50Watt @ 4 Ohm) which can be bought for about $50. You can also use multi channel amplifier.

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4) One pair of speakers for each amplifier. The quality of the surround speakers is not crucial although better ones require no additional PEQ to tame any frequency response errors that may be audible. I use small HT speakers bought used.  Extended bass response is not mandatory for hall ambience reproduction.

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5) Powered USB Hub such as TPLink UH700 or Anker 10-Port USB 3.0 Hub.  All your USB DACs must be connected to a hub to maintain easier synchronization including additional hubs.

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6) AmbiophonicsDSP from http://electro-music.com/article.php?t=37687 . If you prefer higher resolution files, you may use a MiniDSP with the Ambiophonic plugin.  These products are for use in the front and rear direct sound channels within JRiver or external to it and preferably connected after a preamplifier.

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7) SIR 2 from http://www.siraudiotools.com/sir2.php . You can also use JRiver’s built in DSP convolver but it requires modification of the original IRs and is time consuming. It is best to get a convolution engine that can process true stereo impulse response for 3D ambience.

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Step 1.

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In JRMC, create Zones for the convolution speakers. I will use a 90 degree IR as an example.

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i) Click Player > Add Zone > Name [Zone 90 degrees] Copy - None > OK

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Each IR contains hall reflections from the left and right of the stage but both are destined for the same surround speaker.  Do the same for the rest of the IRs. Each Zone must use both Lsp and Rsp files. If you intend to use all 24 IRs, then you need to create 12 Zones which will be fed to 12 right and 12 left convolved surround speakers. You will need one DAC for every zone. In my case, as I have described in (2) above, I use eight DACs for 8 zones.

 

 

 

 

 

 

 

 

 

 

 

 

 

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Chart 1

 

Step 2.

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i) Plug in your first DAC for a surround pair to the USB hub.

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ii) Click Tools > Options > Audio > Zone to configure > Choose Zone 90 degrees > Audio Device > click arrow > click More >  "N" USB DAC  [Direct Sound] . (or the appropriate driver for your DAC such as ASIO or WASAPI).

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IMPORTANT : -  JRMC will automatically assign an unique number/identity each for the identical DACs.  The number will remain the same unless you disconnect the USB DAC from the USB Hub or computer port.

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iii) Click Tools > Options > Audio > {after you have configured the DAC} > Device settings > Buffering > 0.05 seconds. This value may change and is DAC dependent for skip free play. You need to experiment to decide what's best for your system. Start with the lowest number.  I use 0.05 second with SIR 2 convolver but with JRiver’s in-built convolver I needed about  0.1 second of buffer.

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iv) Make sure you disable “Play from Memory” in JRMC as this can affect synchronization between DACs.

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Chart 2

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​Step 3

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After you have completed Step 2, you now need to use JRiver's DSP functions to include the IR files.

For Zone90degrees

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i) Click Tools > Options > Audio > DSP & Output format > tick Output format > Since the PCM2704 DAC is only capable of an up to 48 kHz sampling rate, I set all to 44,100 Hz.The convolution speakers' resolution is not critical as the sound that comes from those speakers is sound walls with extended delay and decay rates as well as losses in high frequency energy. Choose the sampling rate according to your DAC's specification.

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ii) Tick Audio Leveling. This feature is important to maintain uniform volume level of the convolution speakers. 

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iii) Click Tools > Options > Audio > DSP & Output format > Manage plug-in > add SIR 2 . 

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Step 4.

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You have to follow SIR 2 instruction to how combine both Lsp and Rsp Impulse response to create a true stereo Impulse response. This is the easiest part of this guide.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Chart 3

 

 

 

Step 5.

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After you have created all the necessary zones, you have to link all the Zones. Linking the zones will enable you to play all the speakers simultaneously.

 

i) Click Playing Now > click Main Zone {Your front main two channels zone} > right click > Link Zone > {Link all the zones}. In my system, the Main Zone with AmbiophonicsDSp is linked to the Rear Zone and all the convolution Zones. All the zones will now play simultaneously.

 

You can use the same method to play 5.1 format. To do this you have send the front left, right and centre to the main Ambiophonics front speakers. See JRiver instruction to do this. The side surround can be send via another DAC to the side speakers. Contact Ambiophonics.org for more details.

 

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Step 6

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Adjust link timing.

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All the convolved surround speakers and the rear direct sound Ambiophonics speakers will play in sync. However, since my main speakers use a Mytek DAC with ASIO drivers, I require a slight adjustment of the timing of the main speakers. Follow the instruction below for this timing adjustment. ( edit:- I am now using Mytek with direct sound).

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i) Click Link (left side of JRMC main screen below Playing Now). You will see main zones there > go to main zone > right click > Adjust Link Timing > Slide the bar.

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ii) This procedure requires patience as the changes take place only after several seconds.  Once the timing is adjusted correctly, all the other speakers will be invisible and you will not hear them separately. Their existence will only be sensed when the speakers are turned on or off even if they are playing relatively loudly. This timing adjustment is the toughest part of convolution setup. For finer adjustment, you can adjust the timing difference of all the speakers to sync with the main speakers. This method requires that only the main speakers and the respective zone be played. You can turn off the amplifiers of all the other zones or mute the sound in the JRiver’s PEQ while adjusting the timing.

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iii) The timing should be adjusted for all other speakers with reference to the main speakers. Ensure the main speakers link timing is at 0. I noticed that you get more accurate syncing when you adjust individual speakers when all the zones are active but muted.

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iv) After you have adjusted the timing for one zone, restart Jriver and check the sound again. Allow about one minute. Usually, it will take a few  seconds but in worst case scenario it should not take more than one minute after restart or reboot as finer adjustment takes time to be effected in the JRiver. Once, you are satisfied with the timing, restart JRiver and mute the zone which you already synced and unmute the next zone you intend to configure. Remember to restart JRiver each time you change the values of delay and let the music play for a minute before adjusting the timing of another zone. 

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Alternatively, you can use Rednet 2 or MOTU 24A/0 to plug and play. The timing will be auto synced due to an internal master clock.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chart 4

 

 

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Troubleshooting

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1)            Out of sync at the start of the track. – It is normal for the first track to be out of sync for the first few seconds and sometimes it can take up to 1 minute to sync.  Increase the “Play silence at start up for hardware synchronization” to 10 seconds (maximum). Untick “Play files from memory”. This setting can be found in the “Option” tab of JRiver.  You have to do this for all the DACs.

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2)            Long time for stopping – Due to the many zones that were linked, it is common to take an extra few seconds for the sound to stop from all the speakers. You can improve the response time by changing the setting in the “Option” as follows:-

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a.            Track Change – change to standard. ( I use 3 seconds).

b.            Stop, Seek & Skip -  Seek – Standard; Skip and stop – Immediate.

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3)         You may experience a syncing error while playing – The usual reason for this is a change to an album with a different format. You can create alternative sets of Zones for different format or change all your files to a single format. I have created separate folders of down sampled files to 16/44.1 for convolution purpose. In most cases, JRiver will automatically pause and synchronize. I have listened for hours with SIR2 without any synchronization issues at all.

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4)            For a smooth listening experience – Create a playlist that begins with a track of silence of about 60 seconds. Add your songs to this playlist and play from the playlist. This will ensure your music stays in sync throughout your listening session.

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5)            Out of sync for no apparent reasons –  If this happens, just reboot the computer and all will be in sync.

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6)            Ideally, use  PC with minimum processes.

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