Multi-sub and Dirac. Do you need a minidsp? (beginners REW)
Jan 1, 2015 2:37:13 GMT -5
weigle2, nickwin, and 7 more like this
Post by ansat on Jan 1, 2015 2:37:13 GMT -5
Other REW tutorials using the XMC
REW assisted subwoofer placement using the XMC USB input
how to use the USB input to measure other speakers
Interpreting your dirac results
Dirac / XMC-1 F.A.Q.
So I have posted a lot of gripe on how Dirac treats multiple subwoofers and how XMC in its current state does not provide the tools necessary to fix this. As I was setting up the behringer 1124 I decided I was tired of using it, and it was time for something new.
So I thought I would try out a minidsp this time for outboard eq, and I must say that this was one of the easiest dsp's that I have worked with. In this writeup, I am not going dig terribly deep into REW but will trust that you will ask questions if needed or look up some of the many tutorials out there for more advanced usage. I would consider this to be a biginners (never successfully used REW) measurement crash course.
So here is the process that I use to deal with multiple subwoofers. (The Minidsp 2x4 can handle 4 subs)
The first step is to determine if you need outboard PEQ or not.
You will need:
1. a measurement microphone (the emotiva emm-1 will work great)
2. REW link
3. a long usb connection to the XMC
Step 1 - install REW
Step 2 - using a y rca splitter - plug both subs into the XMC left subwoofer out.
Step 3 - Configure the XMC as the following (you will need to have speaker preset 2 clear of any PEQ or distances) In preset 2, configure your mains as small speakers and set the xover to 200hz (do not set this any lower) and configure the subs to mono.
Step 4 - Plug in the usb connection to the back of the xmc and to your computer (drivers should start installing)
Step 5 - Plug in the XMC microphone to the computer and place the microphone in the main listening position.
Step 6 - Open REW and click on preferences. Your "Output Device and Output" will be Speakers (#-usb2.0..) set the default output to SPEAKER. set the "Input Device and Input" to microphone (#-C-Media). Check the "Control output mixer/volume" and set the "output volume" to 1.0.
Step 7 - either turn off or disconnect your main speakers at the amplifier. (your subs need to remain powered on)
Step 8 - change the input on the xmc to USB stream and set the speaker set to Preset 2 and surround mode to Direct.
Ok, So what I had you do was set a crazy high crossover point for your subwoofers as the usb will only support 2 channels. By turning off the main speakers when we use rew, only the subs will play as REW is going to try and take a measurement of your left speaker and the XMC bass management will send all frequencies below 200 to the subwoofer. I did this as this is the only way that will be universal for 99% of the XMC users out there. If you have a HDMI port you can use the asio drivers and output 4 for your subwoofers on speaker set 2 and not deal with the crazy crossover workaround.
The next steps will require you to plug and unplug certain subwoofers. In this situation we are going to do this as if we have 2 subs (Sub A and Sub B).
Edit: (thanks wizardofoz ) It is also important that you find a good location to place your computer and yourself. We are measuring direct and reflective energy, and while we do not need to have accurate SPL or adequately remove background noises, a walking bass trap (such as yourself) can create or hide problems in the measurements. I usually sit right behind my main listening position on a stool or step. Avoid the corners of the room and all first reflection points.
1. Unplug the rca or power down Sub B.
2. On the xmc - set the volume to 40 (you can go higher or lower - just use caution)
3. On REW - Click Measure (if you get a calibration warning - ignore it)
4. On the popup screen set the start Freq to 20hz (or lower if your subs can handle it) the end frequency to 20000 and the length to 256k
5. Click start measuring (if you get a calibration warning - ignore it)
6. Unplug Sub A and plug back in Sub B
7. Click measure then start measuring
8. plug in Sub A
9. Click measure then start measuring
10. on the middle top of the screen click the all spl button. On the right side click controls and where it says No Smoothing, select 1/6 and click apply to selected.
Now that we have the graph, we can get a really good A+B=C (a perfect A+B will equal +6db across the board)
Here is what my front two look like after careful placement.
The two purple ones are Sub A and Sub B and the teal one is C (A+B). If C is above both A and B, you do not need outboard EQ for time alignment and you can let Dirac take care of all the EQ with your subs set to mono. If you have an phase control on the back of your subwoofers, you can adjust the phase on one of the subs to maximize the SPL by taking more measurements of both subs at the same time. Or if the C measurement is lower then either A or B in any places, you can adjust the phase control to correct this. This is also the time to use any built in DSP in the subwoofer to make fine adjustments and set the levels so that they are equal. Subwoofer placement can also get rid of any dips in the frequency.
OPTIONAL - move the microphone to other listening positions to insure that they are acceptable. (they usually wont be as good, but you don't want any crazy humps. (dips are ok for other positions))
So lets say that you have a big dip that you cannot get of and you determined that you need a miniDSP. Or you have 3 or 4 subs and the measurements are going crazy.
Make Sure you SAVE all measurements if you need a miniDSP.
You will need the following -
1. a minidsp (I used a revision a unbalanced)here
2. the minidsp 2wayadv filter here (This combo will do up to 4 subwoofers
Install the minidsp using input 1 to the xmc and output 1 and 2 for the subs and install the filter per the mfg. instructions. Plug a usb cord into the minidsp to your computer and open the 2wayADV app. Click on the green Sync icon and follow the instructions to load the filter and its settings. Once connected you can make changes in real time.
We will be focusing on the Crossover, Parametric output, and the Delay/Gain/RMS
Open REW and then open your saved measurements that you had before. Get connected just like you were before using the bass management to get your measurements.
In the MiniDSP app, click on Crossover.
Set your bandpass filters to your subwoofers limits for output 1 and output 2 (remember that the LFE channel will play stuff up to 150hz)
In the MiniDSP app, click the delay/gain/rms - Outputs 1 & 2.
On output channel 1 - set the delay to 1 ms and take a rew measurement. Set the delay to 2 ms and take a rew measurement (note that you can label your measurements) repeat this process until you have taken a measurement in 1 ms increments up to 7. Look at your graphs and determine the highest SPL combination and set your delay to that and start taking measurements in 0.1 increments to dial it in closer. (no need to set any delays for output 2.
OPTIONAL - Move the measurement microphone to another listening position and choose the best result while looking at both positions.
Once you have your delay set we can start flattening out the curve. In the all spl tab of REW, uncheck (at the bottom) every measurement but your original Single subwoofer measurements and the time aligned measurement that was the best. You should be able to see which sub is doing what to the final result. You can use the Parametric EQ output 1 and 2 to start flattening the curve (Use no more then +5 gain as Dirac will add some gain as well)(also note for Q - The higher the number the smaller the frequency range)
Once finished, Run Dirac!
Let me know if I missed something critical. I have used REW daily for a month solid and I could have missed something important.
Also, as always, questions are always welcome.
Tony
REW assisted subwoofer placement using the XMC USB input
how to use the USB input to measure other speakers
Interpreting your dirac results
Dirac / XMC-1 F.A.Q.
So I have posted a lot of gripe on how Dirac treats multiple subwoofers and how XMC in its current state does not provide the tools necessary to fix this. As I was setting up the behringer 1124 I decided I was tired of using it, and it was time for something new.
So I thought I would try out a minidsp this time for outboard eq, and I must say that this was one of the easiest dsp's that I have worked with. In this writeup, I am not going dig terribly deep into REW but will trust that you will ask questions if needed or look up some of the many tutorials out there for more advanced usage. I would consider this to be a biginners (never successfully used REW) measurement crash course.
So here is the process that I use to deal with multiple subwoofers. (The Minidsp 2x4 can handle 4 subs)
The first step is to determine if you need outboard PEQ or not.
You will need:
1. a measurement microphone (the emotiva emm-1 will work great)
2. REW link
3. a long usb connection to the XMC
Step 1 - install REW
Step 2 - using a y rca splitter - plug both subs into the XMC left subwoofer out.
Step 3 - Configure the XMC as the following (you will need to have speaker preset 2 clear of any PEQ or distances) In preset 2, configure your mains as small speakers and set the xover to 200hz (do not set this any lower) and configure the subs to mono.
Step 4 - Plug in the usb connection to the back of the xmc and to your computer (drivers should start installing)
Step 5 - Plug in the XMC microphone to the computer and place the microphone in the main listening position.
Step 6 - Open REW and click on preferences. Your "Output Device and Output" will be Speakers (#-usb2.0..) set the default output to SPEAKER. set the "Input Device and Input" to microphone (#-C-Media). Check the "Control output mixer/volume" and set the "output volume" to 1.0.
Step 7 - either turn off or disconnect your main speakers at the amplifier. (your subs need to remain powered on)
Step 8 - change the input on the xmc to USB stream and set the speaker set to Preset 2 and surround mode to Direct.
Ok, So what I had you do was set a crazy high crossover point for your subwoofers as the usb will only support 2 channels. By turning off the main speakers when we use rew, only the subs will play as REW is going to try and take a measurement of your left speaker and the XMC bass management will send all frequencies below 200 to the subwoofer. I did this as this is the only way that will be universal for 99% of the XMC users out there. If you have a HDMI port you can use the asio drivers and output 4 for your subwoofers on speaker set 2 and not deal with the crazy crossover workaround.
The next steps will require you to plug and unplug certain subwoofers. In this situation we are going to do this as if we have 2 subs (Sub A and Sub B).
Edit: (thanks wizardofoz ) It is also important that you find a good location to place your computer and yourself. We are measuring direct and reflective energy, and while we do not need to have accurate SPL or adequately remove background noises, a walking bass trap (such as yourself) can create or hide problems in the measurements. I usually sit right behind my main listening position on a stool or step. Avoid the corners of the room and all first reflection points.
1. Unplug the rca or power down Sub B.
2. On the xmc - set the volume to 40 (you can go higher or lower - just use caution)
3. On REW - Click Measure (if you get a calibration warning - ignore it)
4. On the popup screen set the start Freq to 20hz (or lower if your subs can handle it) the end frequency to 20000 and the length to 256k
5. Click start measuring (if you get a calibration warning - ignore it)
6. Unplug Sub A and plug back in Sub B
7. Click measure then start measuring
8. plug in Sub A
9. Click measure then start measuring
10. on the middle top of the screen click the all spl button. On the right side click controls and where it says No Smoothing, select 1/6 and click apply to selected.
Now that we have the graph, we can get a really good A+B=C (a perfect A+B will equal +6db across the board)
Here is what my front two look like after careful placement.
The two purple ones are Sub A and Sub B and the teal one is C (A+B). If C is above both A and B, you do not need outboard EQ for time alignment and you can let Dirac take care of all the EQ with your subs set to mono. If you have an phase control on the back of your subwoofers, you can adjust the phase on one of the subs to maximize the SPL by taking more measurements of both subs at the same time. Or if the C measurement is lower then either A or B in any places, you can adjust the phase control to correct this. This is also the time to use any built in DSP in the subwoofer to make fine adjustments and set the levels so that they are equal. Subwoofer placement can also get rid of any dips in the frequency.
OPTIONAL - move the microphone to other listening positions to insure that they are acceptable. (they usually wont be as good, but you don't want any crazy humps. (dips are ok for other positions))
So lets say that you have a big dip that you cannot get of and you determined that you need a miniDSP. Or you have 3 or 4 subs and the measurements are going crazy.
Make Sure you SAVE all measurements if you need a miniDSP.
You will need the following -
1. a minidsp (I used a revision a unbalanced)here
2. the minidsp 2wayadv filter here (This combo will do up to 4 subwoofers
Install the minidsp using input 1 to the xmc and output 1 and 2 for the subs and install the filter per the mfg. instructions. Plug a usb cord into the minidsp to your computer and open the 2wayADV app. Click on the green Sync icon and follow the instructions to load the filter and its settings. Once connected you can make changes in real time.
We will be focusing on the Crossover, Parametric output, and the Delay/Gain/RMS
Open REW and then open your saved measurements that you had before. Get connected just like you were before using the bass management to get your measurements.
In the MiniDSP app, click on Crossover.
Set your bandpass filters to your subwoofers limits for output 1 and output 2 (remember that the LFE channel will play stuff up to 150hz)
In the MiniDSP app, click the delay/gain/rms - Outputs 1 & 2.
On output channel 1 - set the delay to 1 ms and take a rew measurement. Set the delay to 2 ms and take a rew measurement (note that you can label your measurements) repeat this process until you have taken a measurement in 1 ms increments up to 7. Look at your graphs and determine the highest SPL combination and set your delay to that and start taking measurements in 0.1 increments to dial it in closer. (no need to set any delays for output 2.
OPTIONAL - Move the measurement microphone to another listening position and choose the best result while looking at both positions.
Once you have your delay set we can start flattening out the curve. In the all spl tab of REW, uncheck (at the bottom) every measurement but your original Single subwoofer measurements and the time aligned measurement that was the best. You should be able to see which sub is doing what to the final result. You can use the Parametric EQ output 1 and 2 to start flattening the curve (Use no more then +5 gain as Dirac will add some gain as well)(also note for Q - The higher the number the smaller the frequency range)
Once finished, Run Dirac!
Let me know if I missed something critical. I have used REW daily for a month solid and I could have missed something important.
Also, as always, questions are always welcome.
Tony
