Welcome, Guest
Username: Password: Remember me
A freeware application by JLO to build correction file for OpenDRC or DRC. Send your comments/questions here.

TOPIC: Align2 step-by-step guide (hopefully)

Align2 step-by-step guide (hopefully) 2 years 3 months ago #15486

  • Thioabs53785
  • Thioabs53785's Avatar
  • Offline
  • Fresh Boarder
  • Posts: 11
  • Thank you received: 1
  • Karma: 4
Getting started with Align2 this evening. Looks like great solution to DRC. After some wrestling with the setup, I managed to get the fist set of measurements made with REW processed through DRC (still have not got the PORC to work right yet).

Very excited to try this out with regular measurements through my OpenDRC-AN. I plan on posting a step-by-step guide here. Thanks to the developer for putting this software together and offering it free-of-charge.
Last Edit: 2 years 3 months ago by Thioabs53785.
The administrator has disabled public write access.

Align2 step-by-step guide (hopefully) 2 years 3 months ago #15535

  • devteam
  • devteam's Avatar
  • Offline
  • Administrator
  • Posts: 5095
  • Thank you received: 629
  • Karma: 119
Cool. Keep us updated with your progress. :-)
MiniDSP, building a DIY DSP community one board at a time.
The administrator has disabled public write access.

Align2 step-by-step guide (hopefully) 2 years 3 months ago #15548

  • Thioabs53785
  • Thioabs53785's Avatar
  • Offline
  • Fresh Boarder
  • Posts: 11
  • Thank you received: 1
  • Karma: 4
Ok, here is part I. First off, this is a learning process for me too. My hopes in writing down my thoughts as I produced this tutorial will help me learn the process by which you use Align2 better. Please leave comments or suggestions on what I have here, and I will modify as needed.

I thought I would provide a quick tutorial on how I used Room EQ Wizard (REW) and Align 2 to process my in-room measurements of my bi-amp JBL horn loudspeakers.

I chose to measure the impulse responses (IRs) using REW vs. the impulse response recording feature in Align 2.

My measurement setup consists of an Apogee Duet, which is plugged into my Mac Pro. Figure 1 shows the basic measurement setup for recording an IR.


Figure 1. Measurement setup for recording an IR.

My audio interface is an Apogee Duet. This is a Firewire 2 in/2 out device that plugs into my Mac Pro. My Microphone, a Class I Sencore unit, is plugged into Mic input 1, and is phantom powered by the Duet. The Left line output is configured with a TRS Y-adaptor. One of the outputs goes directly to my loudspeaker playback system and the other output is looped back to the Duet via the right line input. This lets met establish a reference channel in REW and lets me capture the actual delay of my loudspeaker playback system.

My loudspeaker system is a bi-amped actively crossed DIY loudspeaker comprised of pro JBL components. From the output of the Duet, the signal is routed to my preamp, which is a Decware tube unit. It is then routed to a MiniDSP 2x4. This performs the crossover duties. The crossover is set at 700 Hz.

Low frequencies are routed to a solid state Rotel RB 1050 amplifier, which powers a pair of JBL 2226J (one per side) in a vented 4 cu. Ft. enclosure tuned to 45 Hz.
High frequencies are routed to a monoblock 300B amplifiers, which power 2” 2445J compression drivers mated to 250 Hz Tractrix wave guides. The low-pass is a 4th order Linkwitz-Riley. The High-pass is a 2nd order Linkwitz-Riley. To account for the fact that the woofer is physically ahead of the compression driver, I have flipped the polarity on the low-frequency output channel of the MiniDSP.

For the sake of this tutorial, other than the crossover duties, all other processing in the MiniDSP has been bypassed (i.e. no parametric EQs on any channels).

To make the measurements required for Align2, I will position my microphone at my listening position and place my microphone at ear-level. I point the microphone up towards the ceiling.

In Figure 2, you can see the L and R channel measurements at the listening position. Most notable you can see the very active modal behavior at frequencies < 300 Hz. This is not uncommon on largely untreated rooms like mine. Bass trapping is something that will have to been done in the future to my listening space.


Figure 2. In-room measurements using REW of JBL loudspeaker system.

In addition, my room has nearly identical dimensions length x width, which further makes the modal behavior more problematic. Figure 3 shows the setup employed for the in-room measurements.


Figure 3. In-room measurement setup.

In order to prepare the IRs for use with Align2, I will need to export the .wav files from REW. I’ll do this through File > Export > Impulse Response as .wav. Figure 4 shows the export settings.


Figure 4. Export settings for impulse responses from REW.

I’ll export the left and right channels as separate audio files. Now we are ready to move into Align 2. Setting up Align 2 is a bit tricky, but the included help file is actually quite informative and I would suggest following it.

The first thing I did after exporting the IRs from REW was to process Graphs for the ‘before’ measurements. This also verified that my connection to Octave was working.


Figure 5. Create graphs menu, for ‘before’ IRs.

Figure 5 shows how I have set this up. IR 1 is my left IR, and IR 2 is my right IR. I’ve unchecked the ‘use mic correction’ because I cannot seem to get this to work yet. The .frd file I have for my microphone immediately causes octave to quit. I need to figure this out. I created a separate directory for these graphs, called ‘Bef’ (for before). I then can generate the graphs, which take about 5 minutes to run on my machine. After the graphs, you can view the graphs in the View graphs section.

Now it is time to make some filters. I am using the DRC option from the EQ menu. DRC type, I’ve chosen the erb option. I am using the bk-2 for the target. I’m not currently using the Mic response, for the response stated above. I’ve selected the L and R IRs for the main IR left and IR right. Figure 6 shows how I’ve set up the DRC settings.


Figure 6. EQ DRC settings.

After the script has run, to see the results, I can create graphs for the filters. I’ll now chose the files with .ircd at the end, for the IR simulation with micro correction and DRC linphase correction. This will show what I should expect my system to measure after I’ve implemented the DRC filter.

Figure 7 shows the before and after frequency response of my system. The after is actually simulated from within Align2. I will have to verify by measuring.


Figure 7. Before and after filter creation.

The filter has done a good job matching the measured response to the B&K curve. My horns natural roll off at about 9 kHz, and the filter is not going to be able to deal with that. I normally have a JBL 2405 super tweeter that helps with the last octave. The balance of the low frequencies seem better, but there is still some room modes to contend with. The best solution here will be to combine active DRC with passive bass trapping.

The next step will be to implement these filters in my OpenDRC-AN, and remasure using the same techniques.

BTW, I do know that I will have a lot of unnecessary ADC-DAC-ADC-DACs in my system. As most DIYers know, the design of a system like this will take many iterations. The goal is to reduce the number of unnecessary conversions to and from the digital domain.

As my main transport is Vinyl, If I want to use DRC and active crossover/eqs for my horns (as I do), I will always be forced to do at least one ADC/DAC conversion. I think both the MiniDSP and the OpenDRC-AN add more to my system than take away.

This message has attachments images.
Please log in or register to see it.

The administrator has disabled public write access.
The following user(s) said Thank You: rgau

Align2 step-by-step guide (hopefully) 2 years 2 months ago #15609

  • devteam
  • devteam's Avatar
  • Offline
  • Administrator
  • Posts: 5095
  • Thank you received: 629
  • Karma: 119
Wow.. great work at documenting all this!
You definitely should let us know when you're ready, we can put together all this under a little Tutorial for the community. There are 2 already here.

www.minidsp.com/support/community-powered-tutorials
Looking forward to hearing your further progress! :-)

DevTeam
MiniDSP, building a DIY DSP community one board at a time.
The administrator has disabled public write access.
Time to create page: 0.145 seconds