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Is this the way? MiniDSP Flex for preamp/DAC duties?

BearWant

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Hi all! I am new here, but been lurking awhile. Thanks in advance for any help you can provide me.

I am trying to move forward in the most cost-effective way, but am willing to spend a buck if it's warranted. Basically, I think my Emotiva DC-1 which is preforming preamp/DAC duties has developed some problems. At first I was suspecting my amplifiers, as they are older, but I believe I have traced it back to this unit. If my subsitute does not fix this, then my amplifiers are next on the chopping block.

At present, my sources are a windows PC using USB and Opt out from my TV. All my content is digital so we are talking Spotify, TIdal, Netflix, etc. either fed by said TV or PC. I have two amplifiers a commercial preamp in the Ashly ftx 2000, which powers JBL 590s. The other amplifier is a vintage Pioneer sa-9800 feeding JBL 530s for when I am sitting at my computer desk. Based on no measurements whatsoever the room does not seem completely awful, but since it's a small apartment, placement of the JBL 590s is less than ideal being only a few feet apart. Despite this, I have been wondering if I might get some nice gains from DSP. The miniDSP Flex would allow me to replace the Emotiva and implement this solution. At present, I have no subwoofer, but that it is something that I would be considering in the future.

My thought is to purchase the Balanced miniDSP flex and use it as a preamp, dac, and for it's dirac capabilities on each of these stereo setups. In the future if I would get a subwoofer, and my Pioneer is still functioning, I was thinking I could power both the sets of speakers using the Pioneer. The Pioneer has Speaker A and B switch, so this would free up channels 3 & 4 on the Flex. I could then put the added sub on Channel 3. It is my understanding since the Flex will store dirac profiles I can just have different profiles depending on whether I am using the 590 floorstanders, or am at my computer desk using the JBL 530.

What am I overlooking? I have never tried to integrate a subwoofer before, so I have no knowledge of this. I would also be trying to use the sub to do dual duty for both listening scenarios. They are close together in the same room, but maybe this is a fools errand. At present there are probably only two locations I could put the sub, so if they are not ideal I am kind of stuck. Also, from my limited understanding doing what I have described will not allow for low and high-pass crossover implementation. What is the cost of this? Is that poor implementation, as I will still be pushing the full signal to both the JBLs and the potential sub of the future? Please excuse my ignorance. Any advice would be valued. Thanks so much.
 

abdo123

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Hi all! I am new here, but been lurking awhile. Thanks in advance for any help you can provide me.

I am trying to move forward in the most cost-effective way, but am willing to spend a buck if it's warranted. Basically, I think my Emotiva DC-1 which is preforming preamp/DAC duties has developed some problems. At first I was suspecting my amplifiers, as they are older, but I believe I have traced it back to this unit. If my subsitute does not fix this, then my amplifiers are next on the chopping block.

At present, my sources are a windows PC using USB and Opt out from my TV. All my content is digital so we are talking Spotify, TIdal, Netflix, etc. either fed by said TV or PC. I have two amplifiers a commercial preamp in the Ashly ftx 2000, which powers JBL 590s. The other amplifier is a vintage Pioneer sa-9800 feeding JBL 530s for when I am sitting at my computer desk. Based on no measurements whatsoever the room does not seem completely awful, but since it's a small apartment, placement of the JBL 590s is less than ideal being only a few feet apart. Despite this, I have been wondering if I might get some nice gains from DSP. The miniDSP Flex would allow me to replace the Emotiva and implement this solution. At present, I have no subwoofer, but that it is something that I would be considering in the future.

My thought is to purchase the Balanced miniDSP flex and use it as a preamp, dac, and for it's dirac capabilities on each of these stereo setups. In the future if I would get a subwoofer, and my Pioneer is still functioning, I was thinking I could power both the sets of speakers using the Pioneer. The Pioneer has Speaker A and B switch, so this would free up channels 3 & 4 on the Flex. I could then put the added sub on Channel 3. It is my understanding since the Flex will store dirac profiles I can just have different profiles depending on whether I am using the 590 floorstanders, or am at my computer desk using the JBL 530.

What am I overlooking? I have never tried to integrate a subwoofer before, so I have no knowledge of this. I would also be trying to use the sub to do dual duty for both listening scenarios. They are close together in the same room, but maybe this is a fools errand. At present there are probably only two locations I could put the sub, so if they are not ideal I am kind of stuck. Also, from my limited understanding doing what I have described will not allow for low and high-pass crossover implementation. What is the cost of this? Is that poor implementation, as I will still be pushing the full signal to both the JBLs and the potential sub of the future? Please excuse my ignorance. Any advice would be valued. Thanks so much.
What you're over looking is something to make it less of a hastle to switch the setups.

The flex doesn't really have a 'zone 2' capabilities.
 
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BearWant

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What you're over looking is something to make it less of a hastle to switch the setups.

The flex doesn't really have a 'zone 2' capabilities.
I just realized I think I put this in the wrong forum section I wonder if I should relocate? Whoops. Regardless, thanks for your response! Any suggestions on eliminating that hastle. I know the Flex doesn't have 2 zone capabilties. I was just thinking I could use the seperate profiles I that would apply the EQ and dirac settings based on which main speakers I was using. Is this not possible?
 

abdo123

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I just realized I think I put this in the wrong forum section I wonder if I should relocate? Whoops. Regardless, thanks for your response! Any suggestions on eliminating that hastle. I know the Flex doesn't have 2 zone capabilties. I was just thinking I could use the seperate profiles I that would apply the EQ and dirac settings based on which main speakers I was using. Is this not possible?
Yes, but the wiring will not be simple (if you want to use more than 2 outputs per setup).

that's what i meant by hastle.
 

tonycollinet

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From what I can understand of what you are trying to do it should work.

To start you intend to drive one amp from outputs 1 and 2, and the other amp from outputs 3 and 4. Then when you get a Sub, power both sets of speakers from the Pioneer via the A/B speaker switching.

An alternative would be to send outputs 1 and 2 to both amps via a splitter cable. Leaving 3 and 4 free for future Sub use, and allowing you still to use the FTX2000 when using a sub.

And yes - with the 4 profiles available, you could use 1 for each of the speaker setups.


One sub for both sets of speakers may work, but as you point out, you need a sub position that works for both listening positions.


And you can do crossovers and gain and delay matching in the Flex for the mains/sub (and store two sets of that in the 2 profiles). However, you have to do that using the standard flex software, Dirac won't do it for you. Once the sub is integrated, you can use Dirac to Eq for mains and sub together as though they were a single pair of speakers.

Disclaimer - I haven't yet integrated a Sub with the flex, so am basing that last paragraph on what I have read.
 
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BearWant

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Yes, but the wiring will not be simple (if you want to use more than 2 outputs per setup).

that's what i meant by hastle.
See tonycollinet's response below. That is what I am trying to do.
 
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BearWant

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From what I can understand of what you are trying to do it should work.

To start you intend to drive one amp from outputs 1 and 2, and the other amp from outputs 3 and 4. Then when you get a Sub, power both sets of speakers from the Pioneer via the A/B speaker switching.

An alternative would be to send outputs 1 and 2 to both amps via a splitter cable. Leaving 3 and 4 free for future Sub use, and allowing you still to use the FTX2000 when using a sub.

And yes - with the 4 profiles available, you could use 1 for each of the speaker setups.


One sub for both sets of speakers may work, but as you point out, you need a sub position that works for both listening positions.


And you can do crossovers and gain and delay matching in the Flex for the mains/sub (and store two sets of that in the 2 profiles). However, you have to do that using the standard flex software, Dirac won't do it for you. Once the sub is integrated, you can use Dirac to Eq for mains and sub together as though they were a single pair of speakers.

Disclaimer - I haven't yet integrated a Sub with the flex, so am basing that last paragraph on what I have read.
Yes this is what I am thinking. I like the idea of the splitter you propose. However, the problem here is that I was thinking to get the balanced version of the Flex, as the FTX 2000 is a balanced amp. But the Pioneer is single ended. I nearly went brain dead trying to figure out if I could go TRS to RCA on and what cable that would require on the output side. Can that balanced signal easily be split keeping one balanced and the other non-balanced. Or would I just simply accept the fact that I would be running my FTX 2000 single ended. If I run the amp that way, I believe they recommend going into the TRS connection. So it would be TRS to TS cable, and I guess splitting that TS to another TS and RCA. If that makes any sense?
 

tonycollinet

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If it were me, I'd send balanced (hot/cold/ground) to the FTX2000, and just split off hot/ground from that to go into the unbalanced amp. You'd get a tiny difference in amplitude between hot and cold signals (of the order of 0.5% depending on the input impdeance of the two amps), but that would not have any detrimental effect.
 
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BearWant

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I was under the impression that there was a subwoofer in the picture.
Not yet, but that is what the upgrade path could look like, so if there are problems with that then this solution would not exactly be future proof.
 
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BearWant

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If it were me, I'd send balanced (hot/cold/ground) to the FTX2000, and just split off hot/ground from that to go into the unbalanced amp. You'd get a tiny difference in amplitude between hot and cold signals (of the order of 0.5% depending on the input impdeance of the two amps), but that would not have any detrimental effect.
I attempted to find a cable that would do that, but hadn't yet landed on one can't say it was exhaustive research. Do you know if they make something like that or is that going to be something I have to build myself?
 

tonycollinet

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I attempted to find a cable that would do that, but hadn't yet landed on one can't say it was exhaustive research. Do you know if they make something like that or is that going to be something I have to build myself?
No, you are going to have to build it or have it made if you want it as a single cable.

Or if you can find a TRS splitter cable (TRS Jack to 2xTRS Sockets) you could then use a standard TRS to whatever your balanced amp takes, and TRS to RCA from MiniDSP cables from there)

EG

 
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BearWant

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No, you are going to have to build it or have it made if you want it as a single cable.

Or if you can find a TRS splitter cable (TRS Jack to 2xTRS Sockets) you could then use a standard TRS to whatever your balanced amp takes, and TRS to RCA from MiniDSP cables from there)

EG

Yes I can a mange that! Now I have to force myself to pull the trigger. Big purchase for me. But I do not see a better way to accomplish this. Thank you for all your help.
 

Dougey_Jones

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OP, generally speaking you're correct. MiniDSP Flex @ 114-116db SINAD is an incredible value for a DAC/Preamp/DSP with Dirac. I'm planning on ditching my Schiit Modius for a Flex for this very reason. I'm going to use my Douk Audio Little Bear XLR switcher so that I can alternate between using the Flex as a preamp and using my traditional Class A preamp depending on my mood.
 
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BearWant

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OP, generally speaking you're correct. MiniDSP Flex @ 114-116db SINAD is an incredible value for a DAC/Preamp/DSP with Dirac. I'm planning on ditching my Schiit Modius for a Flex for this very reason. I'm going to use my Douk Audio Little Bear XLR switcher so that I can alternate between using the Flex as a preamp and using my traditional Class A preamp depending on my mood.
That sounds great. I am actually contemplating whether I should just be patient, and see if I can land a miniDSP SHD. If I can pick one up used that includes the mircophone and Dirac license, I might make out with a more capable unit (with 4 xlr and 4 rca outputs) for the same price after all the FLEX add-ons, cables, and shipping from Hong Kong. Looking at the past sales, I think this is possible. But shhh we don't want demand to go up.
 

phoenixdogfan

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I just realized I think I put this in the wrong forum section I wonder if I should relocate? Whoops. Regardless, thanks for your response! Any suggestions on eliminating that hastle. I know the Flex doesn't have 2 zone capabilties. I was just thinking I could use the seperate profiles I that would apply the EQ and dirac settings based on which main speakers I was using. Is this not possible?
And you could use something like Little Bear switches to go between zones. I do think it's possible, and the Flex, is about as good a preamp/dac/dsp tool as you will find.
 
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BearWant

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And you could use something like Little Bear switches to go between zones. I do think it's possible, and the Flex, is about as good a preamp/dac/dsp tool as you will find.
Excellent. I appreciate the endorsement. Its a either a used SHD or Flex for me.
 

deercreekaudio

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Hi all! I am new here, but been lurking awhile. Thanks in advance for any help you can provide me.

I am trying to move forward in the most cost-effective way, but am willing to spend a buck if it's warranted. Basically, I think my Emotiva DC-1 which is preforming preamp/DAC duties has developed some problems. At first I was suspecting my amplifiers, as they are older, but I believe I have traced it back to this unit. If my subsitute does not fix this, then my amplifiers are next on the chopping block.

At present, my sources are a windows PC using USB and Opt out from my TV. All my content is digital so we are talking Spotify, TIdal, Netflix, etc. either fed by said TV or PC. I have two amplifiers a commercial preamp in the Ashly ftx 2000, which powers JBL 590s. The other amplifier is a vintage Pioneer sa-9800 feeding JBL 530s for when I am sitting at my computer desk. Based on no measurements whatsoever the room does not seem completely awful, but since it's a small apartment, placement of the JBL 590s is less than ideal being only a few feet apart. Despite this, I have been wondering if I might get some nice gains from DSP. The miniDSP Flex would allow me to replace the Emotiva and implement this solution. At present, I have no subwoofer, but that it is something that I would be considering in the future.

My thought is to purchase the Balanced miniDSP flex and use it as a preamp, dac, and for it's dirac capabilities on each of these stereo setups. In the future if I would get a subwoofer, and my Pioneer is still functioning, I was thinking I could power both the sets of speakers using the Pioneer. The Pioneer has Speaker A and B switch, so this would free up channels 3 & 4 on the Flex. I could then put the added sub on Channel 3. It is my understanding since the Flex will store dirac profiles I can just have different profiles depending on whether I am using the 590 floorstanders, or am at my computer desk using the JBL 530.

What am I overlooking? I have never tried to integrate a subwoofer before, so I have no knowledge of this. I would also be trying to use the sub to do dual duty for both listening scenarios. They are close together in the same room, but maybe this is a fools errand. At present there are probably only two locations I could put the sub, so if they are not ideal I am kind of stuck. Also, from my limited understanding doing what I have described will not allow for low and high-pass crossover implementation. What is the cost of this? Is that poor implementation, as I will still be pushing the full signal to both the JBLs and the potential sub of the future? Please excuse my ignorance. Any advice would be valued. Thanks so much.
All of your assumptions are correct, here our our notes on the topic of integrating a 2.1 or 2.2 system with SHD or Flex

This blog describes integrating and tuning a subwoofer into your 2.1 or 2.2 system using the miniDSP 2x4 HD, DDRC-24, SHD, SHD Studio, SHD Power or Flex (referred to as miniDSP). Properly integrating a subwoofer(s) into your stereo system is one of the most powerful ways to increase clarity, imaging, dynamics and all the attributes audiophiles associate with a high fidelity full-range system.

The primary goals of subwoofer integration are



  • Optimization of level, crossover and delay settings
  • Seamless integration of the last audio spectrum octave
  • Elimination of excessive driver excursion and heat dissipation in full-range speakers
  • Clarity resolution and impact


Room EQ Wizard (REW) is used as a tool during the miniDSP plug-in setup. Once the initial setup sections are completed, your system will be optimized to perform a successful Dirac Live project.






Content Outline





  1. System Architecture
    1. Choosing Your Subwoofer Integration Strategy
    2. Hardware Configuration
      1. System Layout
      2. Nominal Subwoofer Settings
      3. Subwoofer Placement
  2. miniDSP Plug-in Setup Using REW
    1. Routing Settings
    2. Crossover Settings
    3. Verifying Polarities
    4. Relative Level Settings
    5. Delay Settings
  3. Using Dirac Live
  4. Output PEQ Overlays







System Architecture



Choosing Your Subwoofer Integration Strategy

If you are building a 2.1 system, your subwoofer will need to be driven monaurally by the miniDSP. If you are building a 2.2 system, you have the choice of a pair of monauralized subwoofers or stereo subwoofers associated with the full-range speakers.

A 2.2 monaural setup can be beneficial in cases where aesthetics dictate the location of the subwoofers, or when the full-range speakers have large subwoofers. A 2.2 stereo subwoofer system would be used when the subwoofers are located in close proximity to the full-range speakers. See the miniDSP Plug-in Setup section below for routing matrix diagrams.



Hardware Configuration

Following are typical hardware configurations tailored specifically to these miniDSP products: 2x4 HD, DDRC-24, SHD, SHD Studio, SHD Power or Flex.



System Layout

Quality cables in good condition and of proper length are essential for this project. Select the proper USB cables to allow for convenient access to the user interface PC and for the microphone to move freely around the listening measurement area. Be sure that all of the subwoofer cables are shielded, low loss, of adequate length and securely connected.

The image below depicts a typical 2.2 setup. A 2.1 system with a single subwoofer will use output 3 only.



Diagram 1.  Required connections and cables for system setup, measurement and correction
Diagram 1. Required connections and cables for system setup, measurement and correction




At this time you can check that the built-in level, equalization, inversion and crossover frequencies of your subwoofer(s) are either bypassed or set to nominal. REW signals generated in your computer will be sent digitally to the miniDSP via USB. Your subwoofer(s) should be set as below, so as to not interfere with the crossover, gain and delay parameters that will be set up in the miniDSP plug-in.



Nominal Subwoofer Settings





Diagram 2.  Baseline subwoofer settings
Diagram 2. Baseline subwoofer settings




Subwoofer Placement

Generally, subwoofers can be placed against the rear wall besides the main with the full-range speakers pulled out for imaging purposes. Before proceeding with tuning, it's a good idea to experiment with various subwoofer positions and orientations depending on aesthetic and room limitations. Use REW to see the effects of the changes in position. Regardless of where the subwoofers end up, their location can be compensated for in either a 2.1 or 2.2 system by adjusting the relative delay between the various speakers.








miniDSP Plug-in Setup



Using the miniDSP plug-in dashboard, you will configure the routing, crossover, relative level and delay settings appropriately for your system.



Routing Settings

For a 2.1 system, your subwoofer will need to be driven monaurally using output channel 3. Typically channel 1 is used for left and channel 2 is used for right full-range speakers. You also have the opportunity in the routing matrix to adjust relative channel levels, as shown in the highlighted boxes.





Diagram 3. Routing table for a 2.1 system
Diagram 3. Routing table for a 2.1 system




A 2.2 monaural setup can be beneficial in cases where aesthetics dictate non-symmetrical locations, or when the full-range speakers have large woofers. An added benefit of monaural subwoofers is the ability to cancel out room modes that otherwise might be present in the stereo setup.





Diagram 4. Routing table for a 2.2 monauralized setup
Diagram 4. Routing table for a 2.2 monauralized setup




A 2.2 setup would be used when the subwoofers are located in close proximity to the full-range speakers. This is also the preferred method with subwoofers that have higher (100 + Hz) crossover frequencies or were designed for direct placement underneath full-range speakers.





Diagram 5. Routing table for a 2.2 stereo subwoofer setup
Diagram 5. Routing table for a 2.2 stereo subwoofer setup




Crossover Setting

Determining the most effective crossover between the main speakers and subwoofer(s) is a task that goes beyond applying symmetrical textbook high and low pass filters. We have found in our testing that asymmetrical filter slopes and shapes can produce significantly enhanced results. This requires experimentation, listening and measurement.

A textbook example of a crossover is the symmetrical 80Hz Butterworth 24dB per octave pictured below. This is commonly found in audio video receivers with large main speakers.





Diagram 6.  Example of a classic Butterworth symmetrical crossover.
Diagram 6. Example of a classic Butterworth symmetrical crossover.




This next example is for a crossover between a 12” full-range speaker and a high powered 15” subwoofer. What's notable is the soft high-pass slope for the mains and sharper low-pass slope for the subwoofer. The soft high-pass helps to eliminate low bass room modes.





Diagram 7.  Example of an asymmetrical crossover designed to optimize audio performance
Diagram 7. Example of an asymmetrical crossover designed to optimize audio performance




The following graph depicts the same crossover scheme as above, and adds high and low frequency band edge cut-off filters to optimize amplifier and speaker performance. These get added after your Dirac Live project is complete.





Diagram 8.  Crossover with high and low frequency filters for optimizing amplifier and speaker performance
Diagram 8. Crossover with high and low frequency filters for optimizing amplifier and speaker performance




Verifying Polarities

You can find polarity issues by using REW and the invert feature on the plug-in output page. By inverting any of the full-range speakers or subwoofers relative to one another, you can observe dips in the crossover region or across the frequency range.

The example below shows inverting the subwoofer, which reveals a significant gain or dip around the crossover frequency. The same thing can be done with the main speakers to determine if they are subtracting or adding to one another. Generally the polarity is correct when the levels are additive. This is a good time to go back and revisit your crossover settings. You are now prepared to optimize level and delay in the next steps.





Diagram 9.  Inverted versus non-inverted subwoofer showing the effect on frequency response around the crossover region
Diagram 9. Inverted versus non-inverted subwoofer showing the effect on frequency response around the crossover region




Relative Level Settings

Next adjust the relative levels of all speakers and subwoofers using REW and a miniDSP UMIK-1 or UMIK-2. From the central listening area, adjust the relative levels to be equal. You can increase the accuracy of this measurement by moving the microphone around to several locations and averaging the results.



Diagram 10.  Subwoofer and two full-range speaker measurements after adjusting their relative level settings
Diagram 10. Subwoofer and two full-range speaker measurements after adjusting their relative level settings




Delay Settings

It is important that the time of arrival of the audio signals from the full-range speakers and subwoofer(s) are coincident. Using the REW delay measurement capability, you can determine which speaker is acoustically the closest to the central listening area. This may take a bit of trial and error, as you need to measure a positive delay from the remaining speakers. It’s typical to see a few milliseconds of delay on the subwoofer(s), due to DSP processing and since they are often placed back against the wall.

In the example below we have routed the subwoofer output to the left channel with the main full-range speaker as the reference output on the right channel.





Diagram 11.  Subwoofer delay relative to right full-range speaker
Diagram 11. Subwoofer delay relative to right full-range speaker




If your measurement settings are correct, you'll first hear a sharp chirp from the full-range speaker and then a short sweep of low frequencies from the subwoofer. REW automatically calculates the delay. In the example below the delay is 1.9 milliseconds, or a little more than two feet.





Diagram 12. REW measurement showing subwoofer delay from reference full-range speaker
Diagram 12. REW measurement showing subwoofer delay from reference full-range speaker




After you've measured all the delays and are confident that you've got valid numbers, you can enter the correcting delays in the plug-in output section. You then should verify that you have minimized the delays by making the same measurements again.





Diagram 13. Inserting time delay for coincident time of arrival
Diagram 13. Inserting time delay for coincident time of arrival




Optimizing Crossover Settings

Now is a good time to further experiment with the crossover frequencies. You can try different crossover frequency points by underlapping and overlapping crossovers and varying slopes with both symmetrical and asymmetrical combinations. You should do this while listening to the results, and verifying with REW.

With some experimentation, you will be able to get a near optimal subwoofer integration that allows you to enjoy the last octave without the sense of having a subwoofer in the room. Then when you run Dirac Live you will have optimum results.






Using Dirac Live



Before you begin your Dirac project, complete all of the basic setup steps in the above sections. Be sure to remove any parametric equalizer settings you may have added and also the band edge high and low cut filters. But, do not delete the following settings you created during basic setup:



  • Routing Matrix
  • Crossovers
  • Channel Levels
  • Delay Settings




Running Dirac Live

This is a brief overview of the Dirac Live process. Please refer to the Dirac Live User Guide for a detailed description of the procedure.

After loading the Dirac Live software in accordance with the miniDSP manual, you will perform the following steps:



  1. Verify you have all the proper USB connections in place, with adequate room to see your computer and be able to fully move the microphone around the measuring area
  2. Initiate Dirac Live from the miniDSP plug-in
  3. Confirm that you are logged into your Dirac Live account
  4. Verify that you have no error messages before you proceed to level calibration
  5. Perform level calibration combining both Dirac channels in the routing matrix
  6. Select either narrow or wide focus listening area
  7. Perform all specified measurements
  8. Proceed to calculating the Dirac correction waveform
  9. Export the Dirac project to the miniDSP configuration slot of your choice
  10. Save your Dirac project







Output PEQ Overlays



Deer Creek Audio has pre-configured overlay equalization curves that can be applied after completing a Dirac Live project. These are applied on the output page of the four corresponding configuration slots, as shown below.





Diagram 14. Normal configuration slot 1
Diagram 14. Normal configuration slot 1






Diagram 15. Tilt configuration slot 2
Diagram 15. Tilt configuration slot 2






Diagram 16. Warm configuration slot 3
Diagram 16. Warm configuration slot 3






Diagram 17. Bright configuration slot 4
Diagram 17. Bright configuration slot 4









Resources





  1. Room EQ Wizard (REW)
  2. UMIK-1 or UMIK-2 setup with REW
  3. miniDSP Dirac Live User Guide
  4. Gain Structure 101
  5. Subwoofer Integration with miniDSP and Stereo Dirac Live
  6. A Brief Overview of the miniDSP 2x4 HD
  7. miniDSP 2x4 HD User Guide
  8. miniDSP DDRC-24 User Guide
  9. miniDSP Flex User Guide
 
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BearWant

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All of your assumptions are correct, here our our notes on the topic of integrating a 2.1 or 2.2 system with SHD or Flex

This blog describes integrating and tuning a subwoofer into your 2.1 or 2.2 system using the miniDSP 2x4 HD, DDRC-24, SHD, SHD Studio, SHD Power or Flex (referred to as miniDSP). Properly integrating a subwoofer(s) into your stereo system is one of the most powerful ways to increase clarity, imaging, dynamics and all the attributes audiophiles associate with a high fidelity full-range system.

The primary goals of subwoofer integration are



  • Optimization of level, crossover and delay settings
  • Seamless integration of the last audio spectrum octave
  • Elimination of excessive driver excursion and heat dissipation in full-range speakers
  • Clarity resolution and impact


Room EQ Wizard (REW) is used as a tool during the miniDSP plug-in setup. Once the initial setup sections are completed, your system will be optimized to perform a successful Dirac Live project.






Content Outline





  1. System Architecture
    1. Choosing Your Subwoofer Integration Strategy
    2. Hardware Configuration
      1. System Layout
      2. Nominal Subwoofer Settings
      3. Subwoofer Placement
  2. miniDSP Plug-in Setup Using REW
    1. Routing Settings
    2. Crossover Settings
    3. Verifying Polarities
    4. Relative Level Settings
    5. Delay Settings
  3. Using Dirac Live
  4. Output PEQ Overlays







System Architecture



Choosing Your Subwoofer Integration Strategy

If you are building a 2.1 system, your subwoofer will need to be driven monaurally by the miniDSP. If you are building a 2.2 system, you have the choice of a pair of monauralized subwoofers or stereo subwoofers associated with the full-range speakers.

A 2.2 monaural setup can be beneficial in cases where aesthetics dictate the location of the subwoofers, or when the full-range speakers have large subwoofers. A 2.2 stereo subwoofer system would be used when the subwoofers are located in close proximity to the full-range speakers. See the miniDSP Plug-in Setup section below for routing matrix diagrams.



Hardware Configuration

Following are typical hardware configurations tailored specifically to these miniDSP products: 2x4 HD, DDRC-24, SHD, SHD Studio, SHD Power or Flex.



System Layout

Quality cables in good condition and of proper length are essential for this project. Select the proper USB cables to allow for convenient access to the user interface PC and for the microphone to move freely around the listening measurement area. Be sure that all of the subwoofer cables are shielded, low loss, of adequate length and securely connected.

The image below depicts a typical 2.2 setup. A 2.1 system with a single subwoofer will use output 3 only.



Diagram 1.  Required connections and cables for system setup, measurement and correction
Diagram 1. Required connections and cables for system setup, measurement and correction




At this time you can check that the built-in level, equalization, inversion and crossover frequencies of your subwoofer(s) are either bypassed or set to nominal. REW signals generated in your computer will be sent digitally to the miniDSP via USB. Your subwoofer(s) should be set as below, so as to not interfere with the crossover, gain and delay parameters that will be set up in the miniDSP plug-in.



Nominal Subwoofer Settings





Diagram 2.  Baseline subwoofer settings
Diagram 2. Baseline subwoofer settings




Subwoofer Placement

Generally, subwoofers can be placed against the rear wall besides the main with the full-range speakers pulled out for imaging purposes. Before proceeding with tuning, it's a good idea to experiment with various subwoofer positions and orientations depending on aesthetic and room limitations. Use REW to see the effects of the changes in position. Regardless of where the subwoofers end up, their location can be compensated for in either a 2.1 or 2.2 system by adjusting the relative delay between the various speakers.








miniDSP Plug-in Setup



Using the miniDSP plug-in dashboard, you will configure the routing, crossover, relative level and delay settings appropriately for your system.



Routing Settings

For a 2.1 system, your subwoofer will need to be driven monaurally using output channel 3. Typically channel 1 is used for left and channel 2 is used for right full-range speakers. You also have the opportunity in the routing matrix to adjust relative channel levels, as shown in the highlighted boxes.





Diagram 3. Routing table for a 2.1 system
Diagram 3. Routing table for a 2.1 system




A 2.2 monaural setup can be beneficial in cases where aesthetics dictate non-symmetrical locations, or when the full-range speakers have large woofers. An added benefit of monaural subwoofers is the ability to cancel out room modes that otherwise might be present in the stereo setup.





Diagram 4. Routing table for a 2.2 monauralized setup
Diagram 4. Routing table for a 2.2 monauralized setup




A 2.2 setup would be used when the subwoofers are located in close proximity to the full-range speakers. This is also the preferred method with subwoofers that have higher (100 + Hz) crossover frequencies or were designed for direct placement underneath full-range speakers.





Diagram 5. Routing table for a 2.2 stereo subwoofer setup
Diagram 5. Routing table for a 2.2 stereo subwoofer setup




Crossover Setting

Determining the most effective crossover between the main speakers and subwoofer(s) is a task that goes beyond applying symmetrical textbook high and low pass filters. We have found in our testing that asymmetrical filter slopes and shapes can produce significantly enhanced results. This requires experimentation, listening and measurement.

A textbook example of a crossover is the symmetrical 80Hz Butterworth 24dB per octave pictured below. This is commonly found in audio video receivers with large main speakers.





Diagram 6.  Example of a classic Butterworth symmetrical crossover.
Diagram 6. Example of a classic Butterworth symmetrical crossover.




This next example is for a crossover between a 12” full-range speaker and a high powered 15” subwoofer. What's notable is the soft high-pass slope for the mains and sharper low-pass slope for the subwoofer. The soft high-pass helps to eliminate low bass room modes.





Diagram 7.  Example of an asymmetrical crossover designed to optimize audio performance
Diagram 7. Example of an asymmetrical crossover designed to optimize audio performance




The following graph depicts the same crossover scheme as above, and adds high and low frequency band edge cut-off filters to optimize amplifier and speaker performance. These get added after your Dirac Live project is complete.





Diagram 8.  Crossover with high and low frequency filters for optimizing amplifier and speaker performance
Diagram 8. Crossover with high and low frequency filters for optimizing amplifier and speaker performance




Verifying Polarities

You can find polarity issues by using REW and the invert feature on the plug-in output page. By inverting any of the full-range speakers or subwoofers relative to one another, you can observe dips in the crossover region or across the frequency range.

The example below shows inverting the subwoofer, which reveals a significant gain or dip around the crossover frequency. The same thing can be done with the main speakers to determine if they are subtracting or adding to one another. Generally the polarity is correct when the levels are additive. This is a good time to go back and revisit your crossover settings. You are now prepared to optimize level and delay in the next steps.





Diagram 9.  Inverted versus non-inverted subwoofer showing the effect on frequency response around the crossover region
Diagram 9. Inverted versus non-inverted subwoofer showing the effect on frequency response around the crossover region




Relative Level Settings

Next adjust the relative levels of all speakers and subwoofers using REW and a miniDSP UMIK-1 or UMIK-2. From the central listening area, adjust the relative levels to be equal. You can increase the accuracy of this measurement by moving the microphone around to several locations and averaging the results.



Diagram 10.  Subwoofer and two full-range speaker measurements after adjusting their relative level settings
Diagram 10. Subwoofer and two full-range speaker measurements after adjusting their relative level settings




Delay Settings

It is important that the time of arrival of the audio signals from the full-range speakers and subwoofer(s) are coincident. Using the REW delay measurement capability, you can determine which speaker is acoustically the closest to the central listening area. This may take a bit of trial and error, as you need to measure a positive delay from the remaining speakers. It’s typical to see a few milliseconds of delay on the subwoofer(s), due to DSP processing and since they are often placed back against the wall.

In the example below we have routed the subwoofer output to the left channel with the main full-range speaker as the reference output on the right channel.





Diagram 11.  Subwoofer delay relative to right full-range speaker
Diagram 11. Subwoofer delay relative to right full-range speaker




If your measurement settings are correct, you'll first hear a sharp chirp from the full-range speaker and then a short sweep of low frequencies from the subwoofer. REW automatically calculates the delay. In the example below the delay is 1.9 milliseconds, or a little more than two feet.





Diagram 12. REW measurement showing subwoofer delay from reference full-range speaker
Diagram 12. REW measurement showing subwoofer delay from reference full-range speaker




After you've measured all the delays and are confident that you've got valid numbers, you can enter the correcting delays in the plug-in output section. You then should verify that you have minimized the delays by making the same measurements again.





Diagram 13. Inserting time delay for coincident time of arrival
Diagram 13. Inserting time delay for coincident time of arrival




Optimizing Crossover Settings

Now is a good time to further experiment with the crossover frequencies. You can try different crossover frequency points by underlapping and overlapping crossovers and varying slopes with both symmetrical and asymmetrical combinations. You should do this while listening to the results, and verifying with REW.

With some experimentation, you will be able to get a near optimal subwoofer integration that allows you to enjoy the last octave without the sense of having a subwoofer in the room. Then when you run Dirac Live you will have optimum results.






Using Dirac Live



Before you begin your Dirac project, complete all of the basic setup steps in the above sections. Be sure to remove any parametric equalizer settings you may have added and also the band edge high and low cut filters. But, do not delete the following settings you created during basic setup:



  • Routing Matrix
  • Crossovers
  • Channel Levels
  • Delay Settings




Running Dirac Live

This is a brief overview of the Dirac Live process. Please refer to the Dirac Live User Guide for a detailed description of the procedure.

After loading the Dirac Live software in accordance with the miniDSP manual, you will perform the following steps:



  1. Verify you have all the proper USB connections in place, with adequate room to see your computer and be able to fully move the microphone around the measuring area
  2. Initiate Dirac Live from the miniDSP plug-in
  3. Confirm that you are logged into your Dirac Live account
  4. Verify that you have no error messages before you proceed to level calibration
  5. Perform level calibration combining both Dirac channels in the routing matrix
  6. Select either narrow or wide focus listening area
  7. Perform all specified measurements
  8. Proceed to calculating the Dirac correction waveform
  9. Export the Dirac project to the miniDSP configuration slot of your choice
  10. Save your Dirac project







Output PEQ Overlays



Deer Creek Audio has pre-configured overlay equalization curves that can be applied after completing a Dirac Live project. These are applied on the output page of the four corresponding configuration slots, as shown below.





Diagram 14. Normal configuration slot 1
Diagram 14. Normal configuration slot 1






Diagram 15. Tilt configuration slot 2
Diagram 15. Tilt configuration slot 2






Diagram 16. Warm configuration slot 3
Diagram 16. Warm configuration slot 3






Diagram 17. Bright configuration slot 4
Diagram 17. Bright configuration slot 4









Resources





  1. Room EQ Wizard (REW)
  2. UMIK-1 or UMIK-2 setup with REW
  3. miniDSP Dirac Live User Guide
  4. Gain Structure 101
  5. Subwoofer Integration with miniDSP and Stereo Dirac Live
  6. A Brief Overview of the miniDSP 2x4 HD
  7. miniDSP 2x4 HD User Guide
  8. miniDSP DDRC-24 User Guide
  9. miniDSP Flex User Guide
Wow thank you very much for this detailed information. I am on the edge of making the leap for a minidsp SHD. I just wonder if I will really get a massive benefit with my two current systems being 2.0. Like I said my intention is to get a sub down the road, but perhaps those funds may be better allocated to a sub at this time. Then in my time recouping my costs, I can see if minidsp decide to update the SHD and what other options might come in the interrum.
 

tvih

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Wow thank you very much for this detailed information. I am on the edge of making the leap for a minidsp SHD. I just wonder if I will really get a massive benefit with my two current systems being 2.0. Like I said my intention is to get a sub down the road, but perhaps those funds may be better allocated to a sub at this time. Then in my time recouping my costs, I can see if minidsp decide to update the SHD and what other options might come in the interrum.
Thing is you won't get even close to full benefit of the sub without DSP/EQ to handle the crossover and even out the response for a clean integration. But room EQ even for the speakers is great to have. Granted, the SHD is pricey compared to the Flex.
 
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