PBK: ARC For ML Subwoofers & Masterpiece Speakers

[ttocs]

This is specifically related to ML's version of Built-In ARC on certain speakers and subwoofers. It only corrects up to 300Hz for Dynamo Subwoofers, and up to 500Hz for some Masterpiece Speakers.

This first set of examples is with a Expression 13A speaker. I have 3 UMIK microphones setup for REW measurements representing 3 seats, and use the PBK supplied mic for the ARC measurements.

I first measured the 3 seat locations with ARC disabled on the 13A.

I then ran ARC and changed the following settings:
First:
System-Wide Level Target: Changed from 0 to -3. This lowers the Target down closer to the Valley Of The Nulls (wasn't that a movie?), and so the correction doesn't need to think about boosting much of anything.

Next I changed the following:
Low-Frequency Extension (Hz): Changed from 24 to 20
Low-Frequency Extension Slope: Changed from 4th to Flat
Deep Bass Boost (dB): Changed from 0 to 1
Deep Bass Boost Center Frequency (Hz): Changed from 50 to 20

This is the resulting response comparison of Before (Green) vs After (Red) as measured by REW. It mostly shows cutting, and only a small amount of boosting.

Next, I ran a 5 point set of measurements in ARC, then measured the 3 seat locations in REW. Below are the traces for Left Seat, MLP, and Right Seat with the 5 point ARC filter enabled.

And this is a comparison of the 1 point ARC run and the 5 point ARC run as measured at just the MLP.

All of us using room correction apps should already know that when measuring more points (mic locations), we are giving the app lots of valuable information about our space, and the app can then calculate how to make a correction that is an average, or compromise, for each location a measurement was performed. It's not going to be the best for one spot, it's a compromise for every spot.

I use ARC first, then Dirac. For my 13A speakers I always use both. So, I choose to get the best response at the MLP for ARC and only use one mic point. Then I use multiple mic points with Dirac. Every time so far that I've tested both ways (very time consuming), it's always been better with what I call a "1 mic ARC", and a "Multi mic Dirac". I don't profess to know why, exactly, but I think it's because I'm not squashing down the response curve with one correction, then doubling down and doing it again with the second correction. Just a guess, and I really don't care because the results have been very good.

With any type of correction app I've used, when I want to learn how it works I always begin with the mic in one single spot. With ARC this means that I just go from measurement to measurement without moving the mic. The app doesn't know. So ARC just keeps measuring the same thing 5 times. After the measurement process has ended, and I've saved the project, I can then edit to my heart's content and keep saving as a different version and uploading to the speaker. No need for any additional measurements. Edit/Save, edit/save, etc. This way I can edit with one computer running ARC, and concurrently use another computer running REW and measure each edited correction within seconds of changes. It's much easier to do than to explain how to do.

 

[ejspain]

This is specifically related to ML's version of Built-In ARC on certain speakers and subwoofers. It only corrects up to 300Hz for Dynamo Subwoofers, and up to 500Hz for some Masterpiece Speakers.

This first set of examples is with a Expression 13A speaker. I have 3 UMIK microphones setup for REW measurements representing 3 seats, and use the PBK supplied mic for the ARC measurements.

I first measured the 3 seat locations with ARC disabled on the 13A.
View attachment 24071

I then ran ARC and changed the following settings:
First:
System-Wide Level Target: Changed from 0 to -3. This lowers the Target down closer to the Valley Of The Nulls (wasn't that a movie?), and so the correction doesn't need to think about boosting much of anything.
View attachment 24076

Next I changed the following:
Low-Frequency Extension (Hz): Changed from 24 to 20
Low-Frequency Extension Slope: Changed from 4th to Flat
Deep Bass Boost (dB): Changed from 0 to 1
Deep Bass Boost Center Frequency (Hz): Changed from 50 to 20
View attachment 24072


This is the resulting response as measured by REW.
View attachment 24073


Next, I ran a 5 point set of measurements in ARC, then measured the 3 seat locations in REW. Below are the traces for Left Seat, MLP, and Right Seat with the 5 point ARC filter enabled.
View attachment 24074

And this is a comparison of the 1 point ARC run and the 5 point ARC run as measured at just the MLP.
View attachment 24075

All of us using room correction apps should already know that when measuring more points (mic locations), we are giving the app lots of valuable information about our space, and the app can then calculate how to make a correction that is an average, or compromise, for each location a measurement was performed. It's not going to be the best for one spot, it's a compromise for every spot.

I use ARC first, then Dirac. For my 13A speakers I always use both. So, I choose to get the best response at the MLP for ARC and only use one mic point. Then I use multiple mic points with Dirac. Every time so far that I've tested both ways (very time consuming), it's always been better with what I call a "1 mic ARC", and a "Multi mic Dirac". I don't profess to know why, exactly, but I think it's because I'm not squashing down the response curve with one correction, then doubling down and doing it again with the second correction. Just a guess, and I really don't care because the results have been very good.

With any type of correction app I've used, when I want to learn how it works I always begin with the mic in one single spot. With ARC this means that I just go from measurement to measurement without moving the mic. The app doesn't know. So ARC just keeps measuring the same thing 5 times. After the measurement process has ended, and I've saved the project, I can then edit to my heart's content and keep saving as a different ver1sion and uploading to the speaker. No need for any additional measurements. Edit/Save, edit/save, etc. This way I can edit with one computer running ARC, and concurrently use another computer running REW and measure each edited correction within seconds of changes. It's much easier to do than to explain how to do.

This is a PHENOMENAL write up. Great detail and fantastic measurements. Aside from watching a few videos, I know nothing about REW so I have a few questions:

1. Can I use my PBK for the REW measurement?
2. Can I use the SPL built into REW to set the levels?
3. Can I accomplish the same with ARC Genesis if I don't have DIRAC?

 

[ttocs]

This is a PHENOMENAL write up. Great detail and fantastic measurements. Aside from watching a few videos, I know nothing about REW so I have a few questions:

1. Can I use my PBK for the REW measurement?
2. Can I use the SPL built into REW to set the levels?
3. Can I accomplish the same with ARC Genesis if I don't have DIRAC?

Thanks!

1. Unfortunately, no. I'd like to do the same just to see what Anthem's mic thinks of itself with a different app.

2. Absolutely! I do this as my usual routine.

3. I don't see why not.

I'm on the emotivalounge.proboards.com forum and we have a REW thread called ZOOMING In REW and we have another Zoom this coming week if you'd like to attend. We don't know anything about the full version of ARC Genesis, but we have a few different takes on how to use REW on PC and Mac. I use Mac, and Marc uses PC. Marc is the host and he's got years of REW knowledge!

You'll need a mic that REW likes. Can't go wrong with the miniDSP UMIK-1. My favorite miniDSP dealer is Deer Creek Audio in Colorado. They always seem to have anything I want in stock so I can get it in a couple days. You can call them to order or buy from them on Amazon. The last item I bought was a couple weeks ago, a UMIK-2 mic, and it ended up being just a tad less buying directly from them vs Amazon.

 

[ttocs]

Something to keep in mind with "stacking" corrections is that it's not guaranteed to work.

When I tried using PEQ in my processor, and then applied a Dirac filter - also residing in the processor, it doesn't work at all. Lots of crazy results.

But I use ARC in my subs (the ARC correction resides in each sub), then after aligning them to each other create a EQ filter with REW and load that into the PEQ slots of the miniDSP (this REW correction resides in each miniDSP), then, use Dirac to apply more correction (this Dirac correction resides in the processor). This works most of the time.

As I've stated elsewhere, there are times when one type of correction or another in the stacked-correction isn't a good match to the "system" of corrections in the chain. It takes effort to determine which part of the chain doesn't work.

The usual for me is that it works well most of the time.

 

[ejspain]

Thanks!

1. Unfortunately, no. I'd like to do the same just to see what Anthem's mic thinks of itself with a different app.

2. Absolutely! I do this as my usual routine.

3. I don't see why not.

I'm on the emotivalounge.proboards.com forum and we have a REW thread called ZOOMING In REW and we have another Zoom this coming week if you'd like to attend. We don't know anything about the full version of ARC Genesis, but we have a few different takes on how to use REW on PC and Mac. I use Mac, and Marc uses PC. Marc is the host and he's got years of REW knowledge!

You'll need a mic that REW likes. Can't go wrong with the miniDSP UMIK-1. My favorite miniDSP dealer is Deer Creek Audio in Colorado. They always seem to have anything I want in stock so I can get it in a couple days. You can call them to order or buy from them on Amazon. The last item I bought was a couple weeks ago, a UMIK-2 mic, and it ended up being just a tad less buying directly from them vs Amazon.

Perfect. I'll definitely join. I'll also get my mic ordered this week.

 

[Fidji99]

Buy UMIK-2, you deserve it.

 

[ejspain]

Buy UMIK-2, you deserve it.

Done

 

[TiBoneFramer]

If I may, you should think twice IMO about raising those low pass settings. ARC is using them based on in room response of your speakers dying off. You are allowing it to WAY boost down low, which as I know you are conscious of that, may not be what you want.

Where do you put your mic locations? ARC recommends in an M or X configuration, 2-3 feet from the MLP, +&- 6” from ear height. Measurements 2/3 and 4/5 should be symmetrical to each other.

Please advise. Not picking on you, just trying to learn

 

[ttocs]

If I may, you should think twice IMO about raising those low pass settings. ARC is using them based on in room response of your speakers dying off. You are allowing it to WAY boost down low, which as I know you are conscious of that, may not be what you want.

My first step is to LOWER the Target down by -3dB so any possibility of boost being added in the correction process is minimized.
Instead of forcing a rolloff at the low end, I maintain a flat target.
When the Deep Bass Boost is changed from 0 to 1, this is adding back 1dB at 20Hz which was lowered by -3dB to begin with. The effect is to extend the low bass a little, and it does, but not like you would think it does, it's a relative -2dB lower overall target.

Minimum Correction was already set at 20Hz, this remained unchanged for the examples I posted yesterday. As you will see below, the max "boost" is just +1dB@20Hz in an apples to apples correction compare, or as I call it, a comparo (Mike Brewer (Wheeler Dealers)).

Where do you put your mic locations? ARC recommends in an M or X configuration, 2-3 feet from the MLP, +&- 6” from ear height. Measurements 2/3 and 4/5 should be symmetrical to each other.

For the ARC plots I show above from yesterday I used the 5 point mic locations as shown in the ARC app relative to the sofa in the graphic.

Below is a straight up comparo of ARC Correction vs ARC Correction with two different settings groups applied. Both measurements were performed today, mic remained in the same spot unmoved.
The Blue Dashed Line is with the following settings with Deep Bass "Boosted" 1dB:
Low-Frequency Extension (Hz): 20
Low-Frequency Extension Slope: Flat
Deep Bass Boost (dB): 1
Deep Bass Boost Center Frequency (Hz): 20
Minimum Correction Frequency (Hz): 20

The Purple Solid Line is with these settings and no Bass Boost:
Low-Frequency Extension (Hz): 24
Low-Frequency Extension Slope: Flat
Deep Bass Boost (dB): 0
Minimum Correction Frequency (Hz): 24

The major difference between these two sets of settings is the Minimum Correction Frequency. Instead of the automatically generated default of 20Hz as represented by the Blue Dashed Line, I changed this setting to 24Hz so ARC would not alter the natural low end of this speaker and so it could not be described as being "boosted". As can be seen the amount of "boost" @20Hz is +1dB above the natural rolloff of the speaker in the uncorrected range.

 

[TiBoneFramer]

Talk with Anthem. You are severely taxing your woofers putting them to Flat. It’s not what you are making it sound like my friend.

You only got a little but the speaker is getting a lot. Your speakers, your ears, but I’m just saying this is a bad idea.

Again, before you get mad at me. Please talk with Anthem.

My first step is to LOWER the Target down by -3dB so any possibility of boost being added in the correction process is minimized.
Instead of forcing a rolloff at the low end, I maintain a flat target.
When the Deep Bass Boost is changed from 0 to 1, this is adding back 1dB at 20Hz which was lowered by -3dB to begin with. The effect is to extend the low bass a little, and it does, but not like you would think it does, it's a relative -2dB lower overall target.

Minimum Correction was already set at 20Hz, this remained unchanged for the examples I posted yesterday. As you will see below, the max "boost" is just +1dB@20Hz in an apples to apples correction compare, or as I call it, a comparo (Mike Brewer (Wheeler Dealers)).


For the ARC plots I show above from yesterday I used the 5 point mic locations as shown in the ARC app relative to the sofa in the graphic.

Below is a straight up comparo of ARC Correction vs ARC Correction with two different settings groups applied. Both measurements were performed today, mic remained in the same spot unmoved.
The Blue Dashed Line is with the following settings with Deep Bass "Boosted" 1dB:
Low-Frequency Extension (Hz): 20
Low-Frequency Extension Slope: Flat
Deep Bass Boost (dB): 1
Deep Bass Boost Center Frequency (Hz): 20
Minimum Correction Frequency (Hz): 20

The Purple Solid Line is with these settings and no Bass Boost:
Low-Frequency Extension (Hz): 24
Low-Frequency Extension Slope: Flat
Deep Bass Boost (dB): 0
Minimum Correction Frequency (Hz): 24

The major difference between these two sets of settings is the Minimum Correction Frequency. Instead of the automatically generated default of 20Hz as represented by the Blue Dashed Line, I changed this setting to 24Hz so ARC would not alter the natural low end of this speaker and so it could not be described as being "boosted". As can be seen the amount of "boost" @20Hz is +1dB above the natural rolloff of the speaker in the uncorrected range.

View attachment 24078

I

 

[TiBoneFramer]

Sorry I just want to add: I dont mean to sound like a know it all or like I'm bashing ttocs. His experience and my experience with ARC are totally different, and I dont get success from his methods. If he does and everyone else too I'm really happy for you all. But not for me. My 15As, 34C and BF212s have responded much better the closer I adhere to ARC design specifications and have spent time on the phone with Anthem that made tremendous difference for my space.

So man I'm really happy for your results. To anyone reading this thread try ttocs suggestions but also try Anthems way too and see what sounds better. I'm not saying we dont have to adjust things a little to our room tastes and speakers. But if I had 13As (mind you, I only do big theatre) they'd be blown with ttocs method

 

[ttocs]

Talk with Anthem. You are severely taxing your woofers putting them to Flat. It’s not what you are making it sound like my friend.

You only got a little but the speaker is getting a lot. Your speakers, your ears, but I’m just saying this is a bad idea.

Again, before you get mad at me. Please talk with Anthem.

I

Please show me how you use Martin Logan PBK ARC with your Renaissance speakers.

 

[TiBoneFramer]

Please show me how you use Martin Logan PBK ARC with your Renaissance speakers.

I can only tell you where I am at currently as I am still learning and improving what sounds best in my room.

I set my mic in between my ears at the MLP pointed up. Run a sweep. Move 3' left and right but 6" up on one and 6" down on the other (relative to MLP). Thats 2/3.
Then I go forward and out, almost like an M, but still 3' or less. 6" up and 6" down from MLP. Thats 4/5.

Currently, I believe there is a fair bit of flexibility where you put the mic as correction curves usually turn out pretty similar for me even as I have been a little off the above. But thats my knowledge right now.

I do not lower system level -3 as I wonder. Does that actually work? I dont have an anthem processor, so am I setting something that makes my ENTIRE speaker 3db quiet? Cause I have never had to adjust my processor trim so I dont think that really works. If anything it just makes the bass anemic, and sure I'd rather it not boost, but it only will by 6db, vs having my speaker entirely more bass shy....I'll survive (if I ever learn it DOES work it will be done next day.)

Side note: on the BF212, I turn the volume up until the lowest peak is at 75db. THAT does work, as I turn my subs up significantly louder after ARC, but my response is flattened in a other level.

As for settings, I dont use the boost. I'd rather shelf my entire speaker a db or two than boost anything in the ML dsp. I will play with minimum and max frequency correction. Currently maxed out works best.

I USED to set all my BF subs to dead flat response and force them flat. I have gained much more performance in every way except for a few db at ultra low frequencies but using the ARC recommended high pass. In fact, its necessary for me. BEQ movies with my subs running 15-20db hot at reference means I can hit 130+db if I so chose. Having the subs roll of is super necessary for me, and I have adopted that with my 15As. Now 15s are no slouch, but I do use the ARC found slope with one exception...always 24db/octave. I have too many phase issues with steeper or flatter slopes. So if I have to bump up or down a few db and 4th order it to match the woofer roll off, that I will.

I upload the file, play with the mid bass and low bass level knob (knob I will only turn to +2 like the switch). The rest is done in my processor. Either via room correction or by my ear. I'd rather (and do!) shelve the panel and upper woofer than boost at all.

Disclosure: LOUD HT enthusiast with content down to single hz way above reference level. If I was just doing 85db music I think I'd be more inclined to boost a bit. Still, strongly advice reconsidering flattening high pass

 

[Fidji99]

This is specifically related to ML's version of Built-In ARC on certain speakers and subwoofers. It only corrects up to 300Hz for Dynamo Subwoofers, and up to 500Hz for some Masterpiece Speakers.


With any type of correction app I've used, when I want to learn how it works I always begin with the mic in one single spot. With ARC this means that I just go from measurement to measurement without moving the mic. The app doesn't know. So ARC just keeps measuring the same thing 5 times. After the measurement process has ended, and I've saved the project, I can then edit to my heart's content and keep saving as a different version and uploading to the speaker. No need for any additional measurements. Edit/Save, edit/save, etc. This way I can edit with one computer running ARC, and concurrently use another computer running REW and measure each edited correction within seconds of changes. It's much easier to do than to explain how to do.

Frequency range is good place to start when doing before/after comparison and can tell you whether you are going in the right direction.
My 2 eurocents

1) ARC is using IIR filters - I would say it is OK until approx. 150Hz, then the phase shifts introduced by IIR filters can start to become audible
2) We are quite insensitive on FR in bass region - this is what is considered to be good practice [as per good people at acousticfrontiers.com, which is my bible re room measurements] https://www.ampslab.com/RECOMMMENDED READ/LOUDSPEAKER MEASUREMENTS/acoustic_measurement_standards.pdf

Low Frequency Response** Within +/‐10dB at 1/24th octave Within +/‐5dB at 1/3rd octave

3) ARC [and most of the DRC systems] - measure each speaker separately, which is useless in the greater scheme of things - in 99% of the cases you get mono signal below 60Hz getting from your L-R speakers - so one should focus on measurements of both L&R played together
This is real life example from my room [from the bottom] -
a) 2 curves tracing each other - L&R individual after EQ, so pretty nice picture
b) violet one in the middle - L&R measured together - you can see huge null on MLP
c) red curve on top - L&R measured together with EQ'ing focused on summed response

4) I use MMM [moving mic method] to verify anything in REW re FR. Gives me much better correlation between what I hear and what I see on the graphs.

5) for <250Hz I focus on the time domain [spectrogram] as this is what in my experience separates good from great.
6) Group Delay is also extremely important and by boosting too much in low frequencies you run into the risk of getting into audible artefacts, that sound like smeared sound, although FR looks perfect.
7) I am also quite careful about boosting around the lower end of frequency spectrum - you usually add just significantly distorted signal - look at 1600X measurements. Actually I do crossover between 13A's and subs at 60Hz - gives me much much cleaner sound overall, although they are able to play below 20Hz in my room.

I don't know if you use MiniDsp for your subs [I used to have it prior Trinnov and have done my share of experiments incl. MSO etc] - best results I have ever achieved was when i have just cut first resonance frequencies by PEQ [calculated by REW] - typically around 30Hz and let automatic DRC in my AV processor do the rest. Never double boosted via EQ - nulls are there for a reason.

 

[ejspain]

I can only tell you where I am at currently as I am still learning and improving what sounds best in my room.

I set my mic in between my ears at the MLP pointed up. Run a sweep. Move 3' left and right but 6" up on one and 6" down on the other (relative to MLP). Thats 2/3.
Then I go forward and out, almost like an M, but still 3' or less. 6" up and 6" down from MLP. Thats 4/5.

Currently, I believe there is a fair bit of flexibility where you put the mic as correction curves usually turn out pretty similar for me even as I have been a little off the above. But thats my knowledge right now.

I do not lower system level -3 as I wonder. Does that actually work? I dont have an anthem processor, so am I setting something that makes my ENTIRE speaker 3db quiet? Cause I have never had to adjust my processor trim so I dont think that really works. If anything it just makes the bass anemic, and sure I'd rather it not boost, but it only will by 6db, vs having my speaker entirely more bass shy....I'll survive (if I ever learn it DOES work it will be done next day.)

Side note: on the BF212, I turn the volume up until the lowest peak is at 75db. THAT does work, as I turn my subs up significantly louder after ARC, but my response is flattened in a other level.

As for settings, I dont use the boost. I'd rather shelf my entire speaker a db or two than boost anything in the ML dsp. I will play with minimum and max frequency correction. Currently maxed out works best.

I USED to set all my BF subs to dead flat response and force them flat. I have gained much more performance in every way except for a few db at ultra low frequencies but using the ARC recommended high pass. In fact, its necessary for me. BEQ movies with my subs running 15-20db hot at reference means I can hit 130+db if I so chose. Having the subs roll of is super necessary for me, and I have adopted that with my 15As. Now 15s are no slouch, but I do use the ARC found slope with one exception...always 24db/octave. I have too many phase issues with steeper or flatter slopes. So if I have to bump up or down a few db and 4th order it to match the woofer roll off, that I will.

I upload the file, play with the mid bass and low bass level knob (knob I will only turn to +2 like the switch). The rest is done in my processor. Either via room correction or by my ear. I'd rather (and do!) shelve the panel and upper woofer than boost at all.

Disclosure: LOUD HT enthusiast with content down to single hz way above reference level. If I was just doing 85db music I think I'd be more inclined to boost a bit. Still, strongly advice reconsidering flattening high pass

This is heavy duty stuff. Great read. Boy I need help.

 

[Fidji99]

I can only tell you where I am at currently as I am still learning and improving what sounds best in my room.

I set my mic in between my ears at the MLP pointed up. Run a sweep. Move 3' left and right but 6" up on one and 6" down on the other (relative to MLP). Thats 2/3.
Then I go forward and out, almost like an M, but still 3' or less. 6" up and 6" down from MLP. Thats 4/5.

Currently, I believe there is a fair bit of flexibility where you put the mic as correction curves usually turn out pretty similar for me even as I have been a little off the above. But thats my knowledge right now.

I do not lower system level -3 as I wonder. Does that actually work? I dont have an anthem processor, so am I setting something that makes my ENTIRE speaker 3db quiet? Cause I have never had to adjust my processor trim so I dont think that really works. If anything it just makes the bass anemic, and sure I'd rather it not boost, but it only will by 6db, vs having my speaker entirely more bass shy....I'll survive (if I ever learn it DOES work it will be done next day.)

Side note: on the BF212, I turn the volume up until the lowest peak is at 75db. THAT does work, as I turn my subs up significantly louder after ARC, but my response is flattened in a other level.

As for settings, I dont use the boost. I'd rather shelf my entire speaker a db or two than boost anything in the ML dsp. I will play with minimum and max frequency correction. Currently maxed out works best.

I USED to set all my BF subs to dead flat response and force them flat. I have gained much more performance in every way except for a few db at ultra low frequencies but using the ARC recommended high pass. In fact, its necessary for me. BEQ movies with my subs running 15-20db hot at reference means I can hit 130+db if I so chose. Having the subs roll of is super necessary for me, and I have adopted that with my 15As. Now 15s are no slouch, but I do use the ARC found slope with one exception...always 24db/octave. I have too many phase issues with steeper or flatter slopes. So if I have to bump up or down a few db and 4th order it to match the woofer roll off, that I will.

I upload the file, play with the mid bass and low bass level knob (knob I will only turn to +2 like the switch). The rest is done in my processor. Either via room correction or by my ear. I'd rather (and do!) shelve the panel and upper woofer than boost at all.

Disclosure: LOUD HT enthusiast with content down to single hz way above reference level. If I was just doing 85db music I think I'd be more inclined to boost a bit. Still, strongly advice reconsidering flattening high pass

What processor do you have?

 

[Robert D]

This is heavy duty stuff. Great read. Boy I need help.

After seeing all of the great information here I realize now just how little I know about DSP. If I ever do build another home theater, I will have a local expert do all of this for me.

 

[JonFo]

What processor do you have?

Oh, you have a Trinnov, you lucky boy. It is the end game processor, and I'll be getting one as soon as possible to consolidate a bunch of external gear down into that one (expensive) box.

 

[JonFo]

3) ARC [and most of the DRC systems] - measure each speaker separately, which is useless in the greater scheme of things - in 99% of the cases you get mono signal below 60Hz getting from your L-R speakers - so one should focus on measurements of both L&R played together

That is a very good point, but not often reinforced when discussing DRC or manual EQ. Your graphs sure tell the story.

5) for <250Hz I focus on the time domain [spectrogram] as this is what in my experience separates good from great.
6) Group Delay is also extremely important and by boosting too much in low frequencies you run into the risk of getting into audible artefacts, that sound like smeared sound, although FR looks perfect.
7) I am also quite careful about boosting around the lower end of frequency spectrum - you usually add just significantly distorted signal

Again, excellent summary. I have been spending more and more time in the spectrogram, I used to study waterfall plots religiously, but the spectro makes it easier to see time-domain issues immediately.

Group delay is another underutilized tool, and I found it to be the best way to adjust time delay for the MBM deployment, looking for as flat a GD as possible resulted in perfect sync with the other subs.

Yep, boosts needed in the low-end means your placement is not good, or you don't have enough subs. Only cuts are allowed at the bottom end in my book. So I design and layout for max (balanced) low-end capacity and then re-shape the profile from there. DRC's usually only have to cut when I do that.

 

[TiBoneFramer]

What processor do you have?

Trinnov and McIntosh. The Mc sounds just a little better without the Trinnov running all the bells.