===== XR18 vs MR18 =====

{{drawio>xrmr:main.png}}

==== Introduction ====

This document proposes a test procedure and results comparing Behringer XR18 and Midas MR18 performance.

==== Disclaimers and Claims ====

Starting with a general statement: Measurements are done as close as possible to what would be a scientific measurement process (Configuration and tests are documented, are reproducible by a third party, tests results are published, known assumptions and limitations are mentioned as far as possible).

Now the claims:

  * **Statement #1** : Measurements are done in recording studio environment. Namely, there is no control on CEM/EMI interfering with measurements apart from standard studio installation best practices in terms of proper ED grounding and shielding.  
    * As a consequence, comparing the results is more important that dealing with the RAW value. 
  * **Statement #2** : One input and one output are used on each unit, there is only one pair of interface sample tested. Having a pair allows to check for a similar performance on both interface, to rule out obvious erroneous failures on one interface. It is understood that statistically processing those measurement among several interfaces and unit S/Ns would be much better, but is out of scope of this measurement procedure.
    * As a consequence, these results are (1) immune to critical failures on one channel but are (2) prone to specimen bias.
  * **Statement #3** : XR18 has two high impedance instrument inputs which MR18 does not have. For the sake of comparing apples with apples, Input 9/10 and Output 1/2 are used as references on both units.

Measurement Gear
  * UUTs
    * MR18 S211000533C8H
    * XR18 **XXXXXXXXXXXX**
  * Tools
    * Gen2 Apollo Twin USB
    * XLR Wires / Jack Adapters
    * Room EQ Wizard Rev xxx for measurement

-------------

===== Test Procedure =====

==== T1 - Inner Noise and THD ====

Measure loopback  RTA THD (+N) @1khz + total dynamic range.

=== Setup ===

  * REW in loopback mode, 
  * Double shielded XLR as connection 
  * on both units, use In-9 and Out-1 

Loopback diragram:

{{drawio>xrmr:t11.png}}

=== *R18 Measurement ===

== -12dBfs / G=0 ==
  * Set Inputs Gain to 0dB
  * Set Output level to match a -12dBfs input level
  * Measure RTA and store

== -12dBfs / G=8dB ==
  * Set Inputs Gain to 8dB
  * Set Output level to match a -12dBfs input level
  * Measure RTA and store

== -12dBfs / G=18dB ==
  * Set Inputs Gain to 18dB
  * Set Output level to match a -12dBfs input level
  * Measure RTA and store

== -12dBfs / G=28dB ==
  * Set Inputs Gain to 28dB
  * Set Output level to match a -12dBfs input level
  * Measure RTA and store

-------------

==== T2 - External loop comparison ====

=== Setup ===

{{drawio>xrmr:t21.png}}

=== *R18 Procedure ===

== -12dBfs / G=0 ==
  * Set Inputs Gain to 0dB
  * Set Output level to match a -12dBfs input level
  * Measure Transfer function and store

== -12dBfs / G=8dB ==
  * Set Inputs Gain to 8dB
  * Set Output level to match a -12dBfs input level
  * Measure Transfer function and store

== -12dBfs / G=18dB ==
  * Set Inputs Gain to 18dB
  * Set Output level to match a -12dBfs input level
  * Measure Transfer function and store

== -12dBfs / G=28dB ==
  * Set Inputs Gain to 28dB
  * Set Output level to match a -12dBfs input level
  * Measure Transfer function and store

===== Test results =====

==== T1 - Inner noise and THD ====

=== XR18 Results ===

== -12dBfs / G=0 ==

== -12dBfs / G=8dB ==

== -12dBfs / G=18dB ==

== -12dBfs / G=28dB ==

=== MR18 Results ===

== -12dBfs / G=0 ==

== -12dBfs / G=8dB ==

== -12dBfs / G=18dB ==

== -12dBfs / G=28dB ==

==== T2 - Transfer function ====

=== XR18 Results ===

== -12dBfs / G=0 ==

== -12dBfs / G=8dB ==

== -12dBfs / G=18dB ==

== -12dBfs / G=28dB ==

=== MR18 Results ===

== -12dBfs / G=0 ==

== -12dBfs / G=8dB ==

== -12dBfs / G=18dB ==

== -12dBfs / G=28dB ==