Introduction
We all have different room layouts and different aspirations for how we would like to optimize our home theater or audio listening experience. The miniDSP Flex HT and Flex HTx both bring an unprecedented ability to create precisely executed audio configurations to create immersive audio and home theater systems.
This collection of signal flow diagrams applies to Flex HT and Flex HTx 8x8 processors. Included are examples with both 8 channel linear PCM and 2 channel inputs. Applications include home theater setups, multi-way active stereo systems and multi-subwoofer arrays.
History of Home Theater Systems
Home theaters typically have evolved from stereo systems. First was the addition of a subwoofer to stereo systems, creating the 2.1 system. Then the 2.1 system was expanded with the addition of two subwoofers. Next came a center channel to enhance the voice frequencies, creating a 3.1 or 3.2 system.
Then Dolby Digital and DTS introduced 5.1 standards. The beginning entry level home theater initially had a front, center, right and subwoofer, plus left and right surround channels. This then evolved into the 7.1 system, which is the precursor to today’s higher channel count Atmos systems.
BASIC SIGNAL FLOW COMPONENTS
Signal Flow Diagram
Before you begin the layout of your audio video system, we recommend creating an outline using a Signal flow Diagram. This makes the task of creating the various pages in the Flex HTx Device Console configuration much easier to follow. It is the standard format used throughout the following examples.
Functional Block Diagram
This example shows the Flex HTx functional block diagram This is a good reference for understanding how signals flow through the HTx.
Legend for Signal Flow Diagram
This legend represents the various signal processing functions available, including but not limited to upmixing, downmixing, equalization, gain and delay.
Straight through Configuration
This is the default configuration that appears when you turn on the miniDSP Flex HT or Flex HTx. It is a straight through path that works if you have a complete 7.1 system as your speaker configuration.
Downmixing Surround and Rear Channels to Surround Only
This is a simple example that shows downmixing of surround and rear channels into surround only channels The Flex HT and HTx also have the capability of upmixing, where you might want to synthesize a center channel or surround channels. complete 7.1 system as your speaker configuration.
Home Theater Setups Derived from 8 Channel PCM
Layout for a 5.2 Home Theater
With the Flex HT or HTx you can convert 7.1 Dolby or DTS into 5.2 without losing any program material content.
In this example we mix the left and right surround channels with the left and rear surround channels to create a composite left and right surround channel. For bass management we merge all the low frequencies from the left and right front, LFE and center channels into the bass management channel, which is then split for dual subwoofers.
This configuration provides complete control over all 5.1 channels, with full independent Dirac Live, PEQ, gain and delay adjustment capabilities.
Converting 7.1 Dolby or DTS into a 3.1 System
Here we convert 7.1 Dolby or DTS into a 3.1 system that has 2-way active crossover with left and right main speakers. This configuration allows for individual Dirac Live calibration on all channels and complete configuration of crossovers, equalization and delay for the active 2-way main speakers. You also have the option of mixing the rear and surround channel content into the mains (see next example).
Using a Flex HT to Convert from 7.1 to a 3.1 System
This example illustrates how to take 7.1 Dolby or DTS channels and convert them into 3.1 without losing any rear or surround content. We attenuate the surround and rear channels by 3 dB, and then mix them into the front left and right main channels. For the bass management channel we extract the low frequencies from the left, right and center channels and the full bandwidth of the LFE channel, then mix it into the single subwoofer out.
Home Theater Setups Derived from 2 Channel PCM
Synthesizing a 5.1 Home Theater using Upmixing
If you have 2 channel stereo PCM input, you can synthesize a 5.1 channel home theater using upmixing techniques. Here we create the center channel by positively mixing the left and right channels into the center channel. You also can add gain and bandpass filters to emphasize the voice. The left and right surround channels are created by subtracting and attenuating the left and right channels. Note in the diagram how the mixing uses inversion for subtraction.
Audio System Setups
Upmixing from 2 Channel PCM to 4 Channel
If you have 2 channel stereo PCM input you can synthesize a quadraphonic, or 4 channel, stereo using upmixing techniques. The left and right surround channels are created by subtracting and mixing the left and right channels. Note in the diagram how the mixing uses inversion for subtraction.
Layout for a 4-way Active System
If you have an active 3-way system with subwoofers or a full active 4-way system, you can create a fully configurable setup. This allows complete control over each of the 8 channels for PEQ, crossover frequencies, gain and delay. After you have completely tuned the system using the output channel controls, you can apply Dirac Live or REW AutoEQ to fully calibrate each of the individual left and right speaker systems.
Using Bass Management to create a Monaural Subwoofer Channel
In this example we create a monaural subwoofer channel using the bass management capability for setting high pass, low pass and gain settings. This configuration allows all three channels to be calibrated with Dirac Live or REW AutoEQ.frequencies, gain and delay. After you have completely tuned the system using the output channel controls, you can apply Dirac Live or REW AutoEQ to fully calibrate each of the individual left and right speaker systems.
Multi Subwoofer Configurations
Creating a Six Subwoofer Array for an AVR or AVP
Here we show how to use the analog outputs from your AVR or AVP to create large multi-subwoofer arrays. We are using independent stereo left and right subwoofer outputs, but this method also can be modified for systems with either a single mono subwoofer output or higher subwoofer output channels.
We are creating dual left and right, front and rear subwoofers along with center front and rear monaural subwoofers. There are endless reconfiguration possibilities given the different capabilities of AVR/AVPs and the number of subwoofers that you want to introduce into your home theater environment.