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REW-Good Looking Freq Response Graph Doesn't Tell The Whole Story - Random Thoughts/Findings & Lessions Learned


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Hello,

 

I've recently went thru a rather long and painful "Retune/Reconfigure" process of my system due to the addition of a 3rd Sub (Rythmik F18SE) to compliment the two existing Subs (Rythmik E15HP2 SE's) I was using previously and as a result I needed to basically reconfigure the entire system. During this process I came to find out that adding an additional Sub wasn't as easy or straightforward as I originally expected.

 

My thought going into this was that I would just drop the new Sub into one of the remaining available spots in my room and leave the two previous Subs where they were. In theory this sounds all well and good but in practice it didn't work out that way at all. I came to find out that doing this ended up making a dogs breakfast of my nice looking original REW Freq Response Graph. No matter where I tried to place the new Sub things just kept getting worse so I had to clean the slate and start over from scratch.

 

I'll admit up front that I am no expert in doing this stuff and its certainly not part of my day job so this info is just based on my own experiences thus far while playing with Subs in my leisure as a hobby. I'm quite sure an expert in the field could spot issues in my new configuration and graphs and fix them no sweat but I chose to do this on my own using info found around the web from the various Forums, posted Articles/Papers and pure trial and error.

 

Back when I first added Subs to my system the whole process was rather daunting and the learning curve was quite steep. Now that I have an additional year under my belt doing all this and more experience on what I'm looking at and what to look for during the process I've come to find out that even though the work I put in previously that resulted in a rather pretty REW Freq Response Graph wasn't really telling the whole story and had several issues lurking in the background that I was unaware of all along.

 

This post is intended to show some of those issues I was unaware of and to maybe help others keep an eye out for them should they decide to jump into this process with blinders on like I did a few years back. Now onto the findings....

 

All graphs showing the "Original" configuration was while using 2 X Rythmik E15HP2 SE Subs located at the back of my listening room. One Sub was in the far Left corner and the other was in the far Right corner of the room. Both Subs were firing straight ahead towards the Front Wall where my main towers are located. Below is a rough diagram of the Original Sub placement in the room along with the approx Volume of the space. This was generated with the REW Simulation feature

 

Config # 1 - Original 2 Sub Placement In Room (S1 & S2 are the Rythmik E15HP2 SE's)

51137469132_bbf5b693e8_o.png

 

Config #2 - New 3 Sub Placement In Room (S1 & S3 are the Rythmik E15HP2 SE's) (S2 is the Rythmik F18SE)

51137475147_d68d649209_o.png

 

Lets start off with a comparison Graph of the Freq Response between the two room/sub layouts shown above
 

  • 3 measurements at the Top of the graph are the "Original" 2 Subs Config #1). 1/12th Smoothing in effect
  • 3 measurements at the Bottom of the graph are the "New" 3 Sub Config #2) 1/12th Smoothing in effect

51137360697_1f5bb05596_o.png

 

As you can see, the 2 Sub layout in Config #1 measured quite nicely from a in room Freq Response standpoint. I can tell you I spent over 100hrs trying to duplicate or better that Top measurement trio while re-tuning the room with 3 Subs. In short, it never happened and I was quite disturbed, annoyed and many curse words where thrown around along the way.

 

So much to my dismay I added a 3rd quite massive Sub to the room and for some reason I couldn't understand why, no matter what I did or where I placed all of the Subs, I couldn't better or even match that "Original" in room measurement with 2 Subs. Despite this though, the new 3 Sub configuration sounded significantly better in all areas across the board and especially in the tactile feel and scale categories. It wasn't even close in how the two layouts sounded. Config #2 was a clear winner.

 

Now I will introduce some of the very recently discovered demons that were lurking under the covers of that Config #1 layout with 2 Subs that I didn't realize at the time. After banging my head against the wall for a few weeks I decided to circle back and take a very hard/close look at REW again to compare the two configurations side by side.

 

Lets start this segment off with the ugliest of my findings when comparing Config #1 vs Config #2

 

Spoiler...DISTORTION For Days!!

 

All Channels Distortion Overlay (Left/Right & All Subs)

 

  • Config #1 w / 2 Subs = Blue Line, Crosshair located at highest THD Peak 45.8% @ 17hz
  • Config #2 w / 3 Subs = Pink Line, Crosshair located @ 17hz, THD 5.5%
  • But wait...it gets MUCH Worse

51139142270_f36d01dc60_o.png

 

Right Channel Distortion Overlay (Right CH Only & All Subs)

 

  • Config #1 w / 2 Subs = Green Line, Crosshair located at highest THD Peak 417% @ 19hz  🤯
  • Config #2 w / 3 Subs = Red Line, Crosshair located @ 19hz, THD 2.74%

 

51138035481_8f48e6157b_o.png

 

So it appears that I was pushing the original Subs a bit too hard and got a bit Ham fisted with the output/loudness of the sweep settings in general. Lets take a look at a few other signs of this

 

Spectrogram Graph Comparison - All Channels (Left/Right & All Subs)
 

  • Config #1 w / 2 Subs - Looking pretty HOT in here across the board but especially below 75hz with lots of far reaching overhang trails in the bass region

51138035236_c1dc0cac4f_o.png

 

 

  • Config #2 w / 3 Subs - Waaay cooler across the board but with plenty of energy still down to 10hz and below. Long overhand trials in the bass region look much better

51139142095_abe3d19293_o.png

 

So what did I do differently between the first few Graphs shown so far from the Original vs the New Configuration.

 

1. In Config #2 w / 3 Subs I Level matched the Subs with the Main Tower speakers using Random Pink Noise in the bass region playing between 30-80hz to a Ref Output Level of about 75db SPL

2. In Config #1 w / 2 Subs I Level matched the Subs at the X-Over point only with the Main Tower speakers at the loudest level I would typically listen at (around 95db). So the whole system was level matched based solely on one point of the Freq scale. In hind sight, this was a bad idea 🤕

 

Now lets look at a few other problems I discovered with my original Config #1

 

PHASE

 

Right Channel Phase Overlay (Right CH Only & All Subs)

  • Config #1 w / 2 Subs = Green Line
  • Config #2 w / 3 Subs = Red Line

 

51139142100_1a5375045f_o.png

 

Left Channel Phase Overlay (Left CH Only & All Subs)

  • Config #1 w / 2 Subs = Orange Line
  • Config #2 w / 3 Subs = Green Line
     

51138255138_8076d0cacc_o.png

 

SPL/Phase Graphs

 

Config #1 w / 2 Subs, All Channels (Right/Left CH & All Subs)

  • Blue Graph Line = Freq Response
  • Purple'ish Graph Line = Phase ---What a mess

51138255003_b9ce91dece_o.png

 

Config #2 w / 3 Subs, All Channels (Right/Left CH & All Subs)

  • Pink Graph Line = Freq Response
  • Brown/Green'ish Graph Line = Phase ---Way Cleaner

 

51138810419_f5cd0d8c64_o.png

 

So it appears that there were some serious Phase anomalies going on with Config #1 in addition to it being way too hot in terms of Output Level.

 

What else did I find? Let's look at the Step Response next.

 

STEP RESPONSE
 

Config #1 w / 2 Subs, All Channels (Right/Left CH & All Subs)

 

Now with this one I'll admit that its not clear there was an issue until I took all the other findings into consideration and compared it to the new Confg #2. I can see that there is an initial Spike towards positive polarity which then goes immediately negative with a less than great matching of All the channels at the initial spike. The rest of the plot then starts from the bottom and works its way back up towards 0. Again, I'm not clear on what this really means but looking at the next Graph from Conig #2 tells me something probably wasn't right with this one

 

51138810379_bd27effce3_o.png

 

Config #2 w / 3 Subs, All Channels (Right/Left CH & All Subs)

 

We can see that this Plot is the opposite of the Original one in Config #1 and to me looks more correct based on other Step Plots I've seen around the web

 

51138035111_0f333fc74a_o.png

 

Overlay of STEP RESPONSE comparing Config #1 with Config #2

 

Here in this Plot it becomes clear of the differences between the two Configs #1 vs #2

 

51137360472_1de12f8823_o.png

 

Finally to bring an end to this long original post let's look at the Impulse Response comparisons

 

Right Channel Impulse Response Overlay (Right CH Only & All Subs)

  • Config #1 w / 2 Subs = Green Line - Here Config #1 appears to be showing signs of Pre-Ringing Like A Bell
  • Config #2 w / 3 Subs = Red Line - Config #2 looks pretty clean by comparison
     

51138035396_764716e815_o.png

 

All Channel Impulse Response Overlay (Right/Left CH & All Subs)

  • Config #1 w / 2 Subs = Blue Line - Here Config #1 appears to again be showing signs of Pre-Ringing Like A Bell
  • Config #2 w / 3 Subs = Pink Line - Config #2 looks again pretty clean by comparison
     

51138810569_b14fbf7a93_o.png

 

So getting back to my original point of the post that a pretty Freq Response Graph doesn't tell the whole story of whats going on. The scary part of all this is that at no time while I was listening to my system when Config #1 was in use did I get a sense of something being wrong. The system sounded great compared to how it sounded before any subs or room correction was thrown into the mix so I was living in what is known as ignorant bliss. The Freq Response Chart looked great, things sounded great and everything sounded better than it ever had before I started this journey with room correction and subs.

 

Now that I have had a chance to directly compared the two configurations/layouts with listening and somewhat scientific measurements its become clear to me that if All the measurement data is not taken into careful consideration and your initial setup process is not don't correctly you may be wasting valuable time listening to your system with some ugliness hiding under the covers.  Even though all may seem to sound just fine.

 

I'm open to any additional dialog on this subject/info posted here including dialog that may oppose what I think seems correct now about Config #2 w/ 3 Subs compared to Config #1 w / 2 Subs

 

Thanks for reading and hopefully this helps others in their own journey of pit falls to look out for

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13 hours ago, cjf said:

Hello,

 

I've recently went thru a rather long and painful "Retune/Reconfigure" process of my system due to the addition of a 3rd Sub (Rythmik F18SE) to compliment the two existing Subs (Rythmik E15HP2 SE's) I was using previously and as a result I needed to basically reconfigure the entire system. During this process I came to find out that adding an additional Sub wasn't as easy or straightforward as I originally expected.

 

My thought going into this was that I would just drop the new Sub into one of the remaining available spots in my room and leave the two previous Subs where they were. In theory this sounds all well and good but in practice it didn't work out that way at all. I came to find out that doing this ended up making a dogs breakfast of my nice looking original REW Freq Response Graph. No matter where I tried to place the new Sub things just kept getting worse so I had to clean the slate and start over from scratch.

 

I'll admit up front that I am no expert in doing this stuff and its certainly not part of my day job so this info is just based on my own experiences thus far while playing with Subs in my leisure as a hobby. I'm quite sure an expert in the field could spot issues in my new configuration and graphs and fix them no sweat but I chose to do this on my own using info found around the web from the various Forums, posted Articles/Papers and pure trial and error.

 

Back when I first added Subs to my system the whole process was rather daunting and the learning curve was quite steep. Now that I have an additional year under my belt doing all this and more experience on what I'm looking at and what to look for during the process I've come to find out that even though the work I put in previously that resulted in a rather pretty REW Freq Response Graph wasn't really telling the whole story and had several issues lurking in the background that I was unaware of all along.

 

This post is intended to show some of those issues I was unaware of and to maybe help others keep an eye out for them should they decide to jump into this process with blinders on like I did a few years back. Now onto the findings....

 

All graphs showing the "Original" configuration was while using 2 X Rythmik E15HP2 SE Subs located at the back of my listening room. One Sub was in the far Left corner and the other was in the far Right corner of the room. Both Subs were firing straight ahead towards the Front Wall where my main towers are located. Below is a rough diagram of the Original Sub placement in the room along with the approx Volume of the space. This was generated with the REW Simulation feature

 

Config # 1 - Original 2 Sub Placement In Room (S1 & S2 are the Rythmik E15HP2 SE's)

51137469132_bbf5b693e8_o.png

 

Config #2 - New 3 Sub Placement In Room (S1 & S3 are the Rythmik E15HP2 SE's) (S2 is the Rythmik F18SE)

51137475147_d68d649209_o.png

 

Lets start off with a comparison Graph of the Freq Response between the two room/sub layouts shown above
 

  • 3 measurements at the Top of the graph are the "Original" 2 Subs Config #1). 1/12th Smoothing in effect
  • 3 measurements at the Bottom of the graph are the "New" 3 Sub Config #2) 1/12th Smoothing in effect

51137360697_1f5bb05596_o.png

 

As you can see, the 2 Sub layout in Config #1 measured quite nicely from a in room Freq Response standpoint. I can tell you I spent over 100hrs trying to duplicate or better that Top measurement trio while re-tuning the room with 3 Subs. In short, it never happened and I was quite disturbed, annoyed and many curse words where thrown around along the way.

 

So much to my dismay I added a 3rd quite massive Sub to the room and for some reason I couldn't understand why, no matter what I did or where I placed all of the Subs, I couldn't better or even match that "Original" in room measurement with 2 Subs. Despite this though, the new 3 Sub configuration sounded significantly better in all areas across the board and especially in the tactile feel and scale categories. It wasn't even close in how the two layouts sounded. Config #2 was a clear winner.

 

Now I will introduce some of the very recently discovered demons that were lurking under the covers of that Config #1 layout with 2 Subs that I didn't realize at the time. After banging my head against the wall for a few weeks I decided to circle back and take a very hard/close look at REW again to compare the two configurations side by side.

 

Lets start this segment off with the ugliest of my findings when comparing Config #1 vs Config #2

 

Spoiler...DISTORTION For Days!!

 

All Channels Distortion Overlay (Left/Right & All Subs)

 

  • Config #1 w / 2 Subs = Blue Line, Crosshair located at highest THD Peak 45.8% @ 17hz
  • Config #2 w / 3 Subs = Pink Line, Crosshair located @ 17hz, THD 5.5%
  • But wait...it gets MUCH Worse

51139142270_f36d01dc60_o.png

 

Right Channel Distortion Overlay (Right CH Only & All Subs)

 

  • Config #1 w / 2 Subs = Green Line, Crosshair located at highest THD Peak 417% @ 19hz  🤯
  • Config #2 w / 3 Subs = Red Line, Crosshair located @ 19hz, THD 2.74%

 

51138035481_8f48e6157b_o.png

 

So it appears that I was pushing the original Subs a bit too hard and got a bit Ham fisted with the output/loudness of the sweep settings in general. Lets take a look at a few other signs of this

 

Spectrogram Graph Comparison - All Channels (Left/Right & All Subs)
 

  • Config #1 w / 2 Subs - Looking pretty HOT in here across the board but especially below 75hz with lots of far reaching overhang trails in the bass region

51138035236_c1dc0cac4f_o.png

 

 

  • Config #2 w / 3 Subs - Waaay cooler across the board but with plenty of energy still down to 10hz and below. Long overhand trials in the bass region look much better

51139142095_abe3d19293_o.png

 

So what did I do differently between the first few Graphs shown so far from the Original vs the New Configuration.

 

1. In Config #2 w / 3 Subs I Level matched the Subs with the Main Tower speakers using Random Pink Noise in the bass region playing between 30-80hz to a Ref Output Level of about 75db SPL

2. In Config #1 w / 2 Subs I Level matched the Subs at the X-Over point only with the Main Tower speakers at the loudest level I would typically listen at (around 95db). So the whole system was level matched based solely on one point of the Freq scale. In hind sight, this was a bad idea 🤕

 

Now lets look at a few other problems I discovered with my original Config #1

 

PHASE

 

Right Channel Phase Overlay (Right CH Only & All Subs)

  • Config #1 w / 2 Subs = Green Line
  • Config #2 w / 3 Subs = Red Line

 

51139142100_1a5375045f_o.png

 

Left Channel Phase Overlay (Left CH Only & All Subs)

  • Config #1 w / 2 Subs = Orange Line
  • Config #2 w / 3 Subs = Green Line
     

51138255138_8076d0cacc_o.png

 

SPL/Phase Graphs

 

Config #1 w / 2 Subs, All Channels (Right/Left CH & All Subs)

  • Blue Graph Line = Freq Response
  • Purple'ish Graph Line = Phase ---What a mess

51138255003_b9ce91dece_o.png

 

Config #2 w / 3 Subs, All Channels (Right/Left CH & All Subs)

  • Pink Graph Line = Freq Response
  • Brown/Green'ish Graph Line = Phase ---Way Cleaner

 

51138810419_f5cd0d8c64_o.png

 

So it appears that there were some serious Phase anomalies going on with Config #1 in addition to it being way too hot in terms of Output Level.

 

What else did I find? Let's look at the Step Response next.

 

STEP RESPONSE
 

Config #1 w / 2 Subs, All Channels (Right/Left CH & All Subs)

 

Now with this one I'll admit that its not clear there was an issue until I took all the other findings into consideration and compared it to the new Confg #2. I can see that there is an initial Spike towards positive polarity which then goes immediately negative with a less than great matching of All the channels at the initial spike. The rest of the plot then starts from the bottom and works its way back up towards 0. Again, I'm not clear on what this really means but looking at the next Graph from Conig #2 tells me something probably wasn't right with this one

 

51138810379_bd27effce3_o.png

 

Config #2 w / 3 Subs, All Channels (Right/Left CH & All Subs)

 

We can see that this Plot is the opposite of the Original one in Config #1 and to me looks more correct based on other Step Plots I've seen around the web

 

51138035111_0f333fc74a_o.png

 

Overlay of STEP RESPONSE comparing Config #1 with Config #2

 

Here in this Plot it becomes clear of the differences between the two Configs #1 vs #2

 

51137360472_1de12f8823_o.png

 

Finally to bring an end to this long original post let's look at the Impulse Response comparisons

 

Right Channel Impulse Response Overlay (Right CH Only & All Subs)

  • Config #1 w / 2 Subs = Green Line - Here Config #1 appears to be showing signs of Pre-Ringing Like A Bell
  • Config #2 w / 3 Subs = Red Line - Config #2 looks pretty clean by comparison
     

51138035396_764716e815_o.png

 

All Channel Impulse Response Overlay (Right/Left CH & All Subs)

  • Config #1 w / 2 Subs = Blue Line - Here Config #1 appears to again be showing signs of Pre-Ringing Like A Bell
  • Config #2 w / 3 Subs = Pink Line - Config #2 looks again pretty clean by comparison
     

51138810569_b14fbf7a93_o.png

 

So getting back to my original point of the post that a pretty Freq Response Graph doesn't tell the whole story of whats going on. The scary part of all this is that at no time while I was listening to my system when Config #1 was in use did I get a sense of something being wrong. The system sounded great compared to how it sounded before any subs or room correction was thrown into the mix so I was living in what is known as ignorant bliss. The Freq Response Chart looked great, things sounded great and everything sounded better than it ever had before I started this journey with room correction and subs.

 

Now that I have had a chance to directly compared the two configurations/layouts with listening and somewhat scientific measurements its become clear to me that if All the measurement data is not taken into careful consideration and your initial setup process is not don't correctly you may be wasting valuable time listening to your system with some ugliness hiding under the covers.  Even though all may seem to sound just fine.

 

I'm open to any additional dialog on this subject/info posted here including dialog that may oppose what I think seems correct now about Config #2 w/ 3 Subs compared to Config #1 w / 2 Subs

 

Thanks for reading and hopefully this helps others in their own journey of pit falls to look out for

Hi, as I was interested on your discussion, I submitted your post to Mario Bon (he is a professional Italian speaker designer and he is mostly "a man of science").  I'm giving you here his reply:

 

If, and I repeat if, a system is minimal phase or linear phase then there is a one-to-one relationship between the response in the time domain and the response in the frequency domain. This means that a flat frequency response corresponds to a flawless impulse response. In this condition, the frequency response is sufficient to characterize the system.

 

On the contrary in a mixed phase system or worse in an interference system (for example where there are several sources on different frequency bands or worse in the same frequency band but delayed between them) a flat response in steady state can correspond to a bad time response. This is the case with multi-way speaker systems (both passive and active) even worse if with many subwoofers. It follows that two measurements must be made with loudspeaker systems: the frequency response and the impulse response (either the waterfall or the wavelet or equivalent).

 

It is therefore not surprising that in the face of a flat answer the desired result is not obtained.

 

It is a mistake to expect the DRC or Dirac or whatever to work miracles. In the MiniDSP manual, for example, it is clearly written that the loudspeaker must not introduce delays between the various ways. As if to say that if the speaker does not contain defects, the system corrects those introduced by the environment. It is known that this correction implies approximations because, in theory, it would not be possible because it would have to invert a non-invertible function. To do this, the system introduces approximations. Obviously, these approximations cannot be exaggerated. Basically, the correction system must be able to understand which is the source and which are the reflections to correct.

 

The use of many subwoofers is possible but requires that the relative delay of each subwoofer must be individually adjusted (and canceled). Only in this way the DRC will be able to distinguish the source from the reflections and correct the reflections. On the 
contrary, it's a mess.

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On 4/26/2021 at 5:43 AM, cjf said:

Hello,

 

I've recently went thru a rather long and painful "Retune/Reconfigure" process of my system due to the addition of a 3rd Sub (Rythmik F18SE) to compliment the two existing Subs (Rythmik E15HP2 SE's) I was using previously and as a result I needed to basically reconfigure the entire system. During this process I came to find out that adding an additional Sub wasn't as easy or straightforward as I originally expected.

 

My thought going into this was that I would just drop the new Sub into one of the remaining available spots in my room and leave the two previous Subs where they were. In theory this sounds all well and good but in practice it didn't work out that way at all. I came to find out that doing this ended up making a dogs breakfast of my nice looking original REW Freq Response Graph. No matter where I tried to place the new Sub things just kept getting worse so I had to clean the slate and start over from scratch.

 

I'll admit up front that I am no expert in doing this stuff and its certainly not part of my day job so this info is just based on my own experiences thus far while playing with Subs in my leisure as a hobby. I'm quite sure an expert in the field could spot issues in my new configuration and graphs and fix them no sweat but I chose to do this on my own using info found around the web from the various Forums, posted Articles/Papers and pure trial and error.

 

Back when I first added Subs to my system the whole process was rather daunting and the learning curve was quite steep. Now that I have an additional year under my belt doing all this and more experience on what I'm looking at and what to look for during the process I've come to find out that even though the work I put in previously that resulted in a rather pretty REW Freq Response Graph wasn't really telling the whole story and had several issues lurking in the background that I was unaware of all along.

 

This post is intended to show some of those issues I was unaware of and to maybe help others keep an eye out for them should they decide to jump into this process with blinders on like I did a few years back. Now onto the findings....

 

All graphs showing the "Original" configuration was while using 2 X Rythmik E15HP2 SE Subs located at the back of my listening room. One Sub was in the far Left corner and the other was in the far Right corner of the room. Both Subs were firing straight ahead towards the Front Wall where my main towers are located. Below is a rough diagram of the Original Sub placement in the room along with the approx Volume of the space. This was generated with the REW Simulation feature

 

Config # 1 - Original 2 Sub Placement In Room (S1 & S2 are the Rythmik E15HP2 SE's)

51137469132_bbf5b693e8_o.png

 

Config #2 - New 3 Sub Placement In Room (S1 & S3 are the Rythmik E15HP2 SE's) (S2 is the Rythmik F18SE)

51137475147_d68d649209_o.png

 

Lets start off with a comparison Graph of the Freq Response between the two room/sub layouts shown above
 

  • 3 measurements at the Top of the graph are the "Original" 2 Subs Config #1). 1/12th Smoothing in effect
  • 3 measurements at the Bottom of the graph are the "New" 3 Sub Config #2) 1/12th Smoothing in effect

51137360697_1f5bb05596_o.png

 

As you can see, the 2 Sub layout in Config #1 measured quite nicely from a in room Freq Response standpoint. I can tell you I spent over 100hrs trying to duplicate or better that Top measurement trio while re-tuning the room with 3 Subs. In short, it never happened and I was quite disturbed, annoyed and many curse words where thrown around along the way.

 

So much to my dismay I added a 3rd quite massive Sub to the room and for some reason I couldn't understand why, no matter what I did or where I placed all of the Subs, I couldn't better or even match that "Original" in room measurement with 2 Subs. Despite this though, the new 3 Sub configuration sounded significantly better in all areas across the board and especially in the tactile feel and scale categories. It wasn't even close in how the two layouts sounded. Config #2 was a clear winner.

 

Now I will introduce some of the very recently discovered demons that were lurking under the covers of that Config #1 layout with 2 Subs that I didn't realize at the time. After banging my head against the wall for a few weeks I decided to circle back and take a very hard/close look at REW again to compare the two configurations side by side.

 

Lets start this segment off with the ugliest of my findings when comparing Config #1 vs Config #2

 

Spoiler...DISTORTION For Days!!

 

All Channels Distortion Overlay (Left/Right & All Subs)

 

  • Config #1 w / 2 Subs = Blue Line, Crosshair located at highest THD Peak 45.8% @ 17hz
  • Config #2 w / 3 Subs = Pink Line, Crosshair located @ 17hz, THD 5.5%
  • But wait...it gets MUCH Worse

51139142270_f36d01dc60_o.png

 

Right Channel Distortion Overlay (Right CH Only & All Subs)

 

  • Config #1 w / 2 Subs = Green Line, Crosshair located at highest THD Peak 417% @ 19hz  🤯
  • Config #2 w / 3 Subs = Red Line, Crosshair located @ 19hz, THD 2.74%

 

51138035481_8f48e6157b_o.png

 

So it appears that I was pushing the original Subs a bit too hard and got a bit Ham fisted with the output/loudness of the sweep settings in general. Lets take a look at a few other signs of this

 

Spectrogram Graph Comparison - All Channels (Left/Right & All Subs)
 

  • Config #1 w / 2 Subs - Looking pretty HOT in here across the board but especially below 75hz with lots of far reaching overhang trails in the bass region

51138035236_c1dc0cac4f_o.png

 

 

  • Config #2 w / 3 Subs - Waaay cooler across the board but with plenty of energy still down to 10hz and below. Long overhand trials in the bass region look much better

51139142095_abe3d19293_o.png

 

So what did I do differently between the first few Graphs shown so far from the Original vs the New Configuration.

 

1. In Config #2 w / 3 Subs I Level matched the Subs with the Main Tower speakers using Random Pink Noise in the bass region playing between 30-80hz to a Ref Output Level of about 75db SPL

2. In Config #1 w / 2 Subs I Level matched the Subs at the X-Over point only with the Main Tower speakers at the loudest level I would typically listen at (around 95db). So the whole system was level matched based solely on one point of the Freq scale. In hind sight, this was a bad idea 🤕

 

Now lets look at a few other problems I discovered with my original Config #1

 

PHASE

 

Right Channel Phase Overlay (Right CH Only & All Subs)

  • Config #1 w / 2 Subs = Green Line
  • Config #2 w / 3 Subs = Red Line

 

51139142100_1a5375045f_o.png

 

Left Channel Phase Overlay (Left CH Only & All Subs)

  • Config #1 w / 2 Subs = Orange Line
  • Config #2 w / 3 Subs = Green Line
     

51138255138_8076d0cacc_o.png

 

SPL/Phase Graphs

 

Config #1 w / 2 Subs, All Channels (Right/Left CH & All Subs)

  • Blue Graph Line = Freq Response
  • Purple'ish Graph Line = Phase ---What a mess

51138255003_b9ce91dece_o.png

 

Config #2 w / 3 Subs, All Channels (Right/Left CH & All Subs)

  • Pink Graph Line = Freq Response
  • Brown/Green'ish Graph Line = Phase ---Way Cleaner

 

51138810419_f5cd0d8c64_o.png

 

So it appears that there were some serious Phase anomalies going on with Config #1 in addition to it being way too hot in terms of Output Level.

 

What else did I find? Let's look at the Step Response next.

 

STEP RESPONSE
 

Config #1 w / 2 Subs, All Channels (Right/Left CH & All Subs)

 

Now with this one I'll admit that its not clear there was an issue until I took all the other findings into consideration and compared it to the new Confg #2. I can see that there is an initial Spike towards positive polarity which then goes immediately negative with a less than great matching of All the channels at the initial spike. The rest of the plot then starts from the bottom and works its way back up towards 0. Again, I'm not clear on what this really means but looking at the next Graph from Conig #2 tells me something probably wasn't right with this one

 

51138810379_bd27effce3_o.png

 

Config #2 w / 3 Subs, All Channels (Right/Left CH & All Subs)

 

We can see that this Plot is the opposite of the Original one in Config #1 and to me looks more correct based on other Step Plots I've seen around the web

 

51138035111_0f333fc74a_o.png

 

Overlay of STEP RESPONSE comparing Config #1 with Config #2

 

Here in this Plot it becomes clear of the differences between the two Configs #1 vs #2

 

51137360472_1de12f8823_o.png

 

Finally to bring an end to this long original post let's look at the Impulse Response comparisons

 

Right Channel Impulse Response Overlay (Right CH Only & All Subs)

  • Config #1 w / 2 Subs = Green Line - Here Config #1 appears to be showing signs of Pre-Ringing Like A Bell
  • Config #2 w / 3 Subs = Red Line - Config #2 looks pretty clean by comparison
     

51138035396_764716e815_o.png

 

All Channel Impulse Response Overlay (Right/Left CH & All Subs)

  • Config #1 w / 2 Subs = Blue Line - Here Config #1 appears to again be showing signs of Pre-Ringing Like A Bell
  • Config #2 w / 3 Subs = Pink Line - Config #2 looks again pretty clean by comparison
     

51138810569_b14fbf7a93_o.png

 

So getting back to my original point of the post that a pretty Freq Response Graph doesn't tell the whole story of whats going on. The scary part of all this is that at no time while I was listening to my system when Config #1 was in use did I get a sense of something being wrong. The system sounded great compared to how it sounded before any subs or room correction was thrown into the mix so I was living in what is known as ignorant bliss. The Freq Response Chart looked great, things sounded great and everything sounded better than it ever had before I started this journey with room correction and subs.

 

Now that I have had a chance to directly compared the two configurations/layouts with listening and somewhat scientific measurements its become clear to me that if All the measurement data is not taken into careful consideration and your initial setup process is not don't correctly you may be wasting valuable time listening to your system with some ugliness hiding under the covers.  Even though all may seem to sound just fine.

 

I'm open to any additional dialog on this subject/info posted here including dialog that may oppose what I think seems correct now about Config #2 w/ 3 Subs compared to Config #1 w / 2 Subs

 

Thanks for reading and hopefully this helps others in their own journey of pit falls to look out for

Another contribution from DRC expert Tom Capraro to your question from the same forum:

 

Looking at the graph of the frequency response, I don't understand why the author of the thread is so happy about those frequency responses.
There is a scale represented in 10dB steps, moderately "compressed", and the trend of that curve would produce - basically - an unbalanced sound: muffled in the top three lines and "without bass" in the bottom three lines.
Apart from the fact that a system in the environment is not minimum phase (but excess phase), they seem to me to be approximate frequency responses and with a lot to improve.
Even if a frequency response had a psychoacoustic trend, it would appear, if represented in 10dB steps, to be almost a ruler.
The performance of a psychoacoustic curve is already at the limit, that is to say it is a curve that points towards high SPL listening.

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Thanks for your reply.

 

I'm not sure I quite understand what those two folks are saying but I do agree that the plots posted are certainly not perfect. I'm not sure I would agree that they are bad either though which it sounds like they may be suggesting.

 

I did fail to mention that the subs and system was configured using Audiolense which takes many variables into consideration when the filters are created. I agree again that it won't work miracles though if physical placement is wrong or components are malfunctioning or not working as designed.

 

Are they saying my system is broke? 🤣

 

If so, I guess I have other problems to deal with but I suspect that is not the case. I would more than welcome any hints or tips they can provide showing me where I have gone so wrong. Maybe they can forward over their own room plots/graphs so I know what a good one should look like?

 

Thanks again for your input.

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51 minutes ago, cjf said:

Are they saying my system is broke?

No, they are not saying that.

They mostly say that your measurements are incomplete with space for improvement. For example, the scale of your frequency response graph has too wider steps to show "problems" properly.

Did you apply delay for each subwoofer?

Anyhow, I asked them directly on the Italian thread what measurements and in general what you should do differently to improve/adjust your system. 

 

If you don't understand some passage, let me know, perhaps it's my fault as something might have been lost in translation :)  

 

PS: of course, you can Google translate and contribute directly to "your" Italian discussion.

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Below is a graph showing the Group Delay of the system in its current state (ie..3 Subs Config#2).

 

All Channels appear to line up pretty nicely for the most part. The delays of all channels to the Main Listening position are taken into consideration when the correction filters are created.

 

51138836595_db2f9e8294_b.jpg

 

Below measurement sweep settings from Audiolense shows the actual Delay between each speakers arrival time to the Mic at the MLP. My understanding is that all channels are Delayed to account for the longest Delayed speaker to the MLP found when the measurement sweep is taken and the correction filters is generated.

 

You can see in this case one of the Subs sweep is taking 9.4x /ms to arrive to the MIC

 

51137728276_0024201b8a_z.jpg

 

 

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2 hours ago, cjf said:

In terms of the zoom level of the first Freq Resp chart I'm not sure if adding additional hash marks is possible or not but I can say the largest dip/spike at the worst point is about 10db.

Relative to the frequency response, Tom Capraro replies that it is not a question of dip/spike, but of trend.
Between the first segment (up to about 200Hz) and the harmonic area (from 1500Hz upwards) there is a drastic and sudden drop with a difference in attenuation between 10dB and 15dB.
Such a curvature kills the harmonic rendering of the sound.

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9 hours ago, cjf said:

Below is a graph showing the Group Delay of the system in its current state (ie..3 Subs Config#2).

 

All Channels appear to line up pretty nicely for the most part. The delays of all channels to the Main Listening position are taken into consideration when the correction filters are created.

 

51138836595_db2f9e8294_b.jpg

Here it seems that at around 70 Hz group delay is over 100 ms.
In 100 ms sound travels 34.4 meter whilst at 70 Hz a wavelength is about 5 meter (4.9143 m).

Food for thought...

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Hello,

 

I'm getting the sense that there is a misunderstanding occurring. The original intent of my post was to show that if one only considers the Feq Resp curve in a room measurement and not all the other measurements they may be overlooking other issues that could still be there even though the Freq Resp curve looks OK, good or even great.

 

I do not think that anything sounds wrong or strange with the system as it sits today which is represented as Config #2 in all the graphs previously posted.

 

If one looks at basically any in room speaker measurement found on "pick your favorite audio rag" you see all sorts of uneven spikes/dips and drastic drop offs at various points in the curve. Even with the uber priced super speaker going for hundreds of thousands of dollars. In most cases you see a large bump at 20hz or higher that drops off above and below that +10 to +20db mountain which in my opinion may be fine for those who never actually crank up their system to elevated levels. I suspect the speaker manufacturers do this on purpose so that when listening at low levels it gives a greater sense of bass output. But for those who do crank up the volume of their system the same Freq Resp graph sounds like a 1980's boom box.

 

Its been my understanding that the ultimate goal of any speaker manufacturer would be to have their speaker's Freq Resp look like a perfectly straight line. This goal has not been achieved in any measurement I've ever seen. Such a speaker would be able to reproduce the source material perfectly without adding its own flavor to the original sound. Then you add such a speaker to a real room. At that point all bets are off on what the Freq Resp graph will look like.

 

The fact that my measurements show a roughly 10-12db roll off at each extreme doesn't seem all that bad and in fact matches pretty closely with just my tower speakers alone and no room correction or subs. The biggest difference between Config #2 and a measurement of just the Main towers alone in this same room is that the current measurement has usable bass extension and output down into the single digits.

 

The room this system is located in is quite large (at least 4500cu/ft) for just the listening area alone and very open to other areas of the house as well. In order to fill this space with sound to make the Freq Resp chart have the very typical 10-20+ dB mountain seen in many in room measurements previously mentioned it would take far more cubic inches of Sub and power to go with it. In any case, a Freq Resp chart that looks like that is not what I prefer to hear. I'm not interested in artificial bloom or bass texture that one note sounding due to excessive overhang as a result of again that typical chart seen in the audio rags.

 

With all that said though, I do have the ability to alter the shape of the Freq Resp curve until I'm blue in the face using Audiolense. But this circles back to one of the issues previously shown in my original Config #1 layout with the better looking Freq Resp chart. The end result of trying to reproduce that better looking Freq Resp chart being way higher levels of distortion requiring me to push the Subs outside of their limitations in terms of being able to maintain good SQ at louder listening levels.

 

I can say for sure there is no lack of bass or detail in the current configuration. I don't think it even makes sense to suggest a -10db roll off from the highest peak at around 100hz or so down to 14hz and below while still outputting over 80db+ down there would have a lack of bass output. Even most of those uber mega buck speakers can be down 10-30db or more after 20hz if your lucky.

 

I guess it all comes down to personal preference. I like my sound to be as unflavored as possible and as loud as possible whenever possible.

 

 

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44 minutes ago, cjf said:

Hello,

 

I'm getting the sense that there is a misunderstanding occurring. The original intent of my post was to show that if one only considers the Feq Resp curve in a room measurement and not all the other measurements they may be overlooking other issues that could still be there even though the Freq Resp curve looks OK, good or even great.

 

I do not think that anything sounds wrong or strange with the system as it sits today which is represented as Config #2 in all the graphs previously posted.

 

If one looks at basically any in room speaker measurement found on "pick your favorite audio rag" you see all sorts of uneven spikes/dips and drastic drop offs at various points in the curve. Even with the uber priced super speaker going for hundreds of thousands of dollars. In most cases you see a large bump at 20hz or higher that drops off above and below that +10 to +20db mountain which in my opinion may be fine for those who never actually crank up their system to elevated levels. I suspect the speaker manufacturers do this on purpose so that when listening at low levels it gives a greater sense of bass output. But for those who do crank up the volume of their system the same Freq Resp graph sounds like a 1980's boom box.

 

Its been my understanding that the ultimate goal of any speaker manufacturer would be to have their speaker's Freq Resp look like a perfectly straight line. This goal has not been achieved in any measurement I've ever seen. Such a speaker would be able to reproduce the source material perfectly without adding its own flavor to the original sound. Then you add such a speaker to a real room. At that point all bets are off on what the Freq Resp graph will look like.

 

The fact that my measurements show a roughly 10-12db roll off at each extreme doesn't seem all that bad and in fact matches pretty closely with just my tower speakers alone and no room correction or subs. The biggest difference between Config #2 and a measurement of just the Main towers alone in this same room is that the current measurement has usable bass extension and output down into the single digits.

 

The room this system is located in is quite large (at least 4500cu/ft) for just the listening area alone and very open to other areas of the house as well. In order to fill this space with sound to make the Freq Resp chart have the very typical 10-20+ dB mountain seen in many in room measurements previously mentioned it would take far more cubic inches of Sub and power to go with it. In any case, a Freq Resp chart that looks like that is not what I prefer to hear. I'm not interested in artificial bloom or bass texture that one note sounding due to excessive overhang as a result of again that typical chart seen in the audio rags.

 

With all that said though, I do have the ability to alter the shape of the Freq Resp curve until I'm blue in the face using Audiolense. But this circles back to one of the issues previously shown in my original Config #1 layout with the better looking Freq Resp chart. The end result of trying to reproduce that better looking Freq Resp chart being way higher levels of distortion requiring me to push the Subs outside of their limitations in terms of being able to maintain good SQ at louder listening levels.

 

I can say for sure there is no lack of bass or detail in the current configuration. I don't think it even makes sense to suggest a -10db roll off from the highest peak at around 100hz or so down to 14hz and below while still outputting over 80db+ down there would have a lack of bass output. Even most of those uber mega buck speakers can be down 10-30db or more after 20hz if your lucky.

 

I guess it all comes down to personal preference. I like my sound to be as unflavored as possible and as loud as possible whenever possible.

 

 

OK, fine. I'll stop here.

So you were very happy with your #1, but when #2 arrived you realized that you were "living in an ignorant bliss".

It seems to me that now you are happy "living an ignorant bliss #2". As you are happy, however, it's fine by me and I will not waste my time any further. 

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On 4/26/2021 at 5:36 AM, bibo01 said:

If, and I repeat if, a system is minimal phase or linear phase then there is a one-to-one relationship between the response in the time domain and the response in the frequency domain.

 

bibo, I am not sure exactly what is meant by a "one-to-one relationship."

 

If the system is linear phase (not very common, since there is an unavoidable frequency response bump if a crossover is designed to be linear phase - this is the case with my speakers), then the relationship between frequency and timing/phase is indeed linear, so that could be what is meant by a "one-to-one relationship."  However, with minimum phase, the relationship between frequency and timing/phase is *not* linear, and so I am puzzled as to what "one-to-one relationship" means in this case.

 

If it is possible, would you be able to ask your friend, who surely knows more than I do about this?

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

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2 hours ago, Jud said:

bibo, I am not sure exactly what is meant by a "one-to-one relationship."

The Italian original version was "relazione biunivoca".

In mathematics: one-to-one correspondence, the correspondence between two sets of objects, when one and only one quantity of the second set corresponds to each size of the first set and vice versa.

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REW graphs & axis:  

 

In REW, if you hover the mouse near the upper left corner of a graph, + and – buttons appear allowing you to expand/compress the scale.  Above the upper right corner of the graph are 4 icons, one labelled Limits.  Click that and then type your desired numerical upper and lower limits for the X and Y axes.

 

Your graphs would be much more helpful if you expand the vertical axis to show the full range.  In the horizontal axis, if you're focussing on the bass response, you should set the upper limit of the graph to the upper bass frequency of interest.

Mac Mini (2012 i7) > HQPlayer > RME ADI-2 v2 > Benchmark AHB-2 > Thiel 3.7

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7 hours ago, Jud said:

If the system is linear phase (not very common, since there is an unavoidable frequency response bump if a crossover is designed to be linear phase - this is the case with my speakers), then the relationship between frequency and timing/phase is indeed linear, so that could be what is meant by a "one-to-one relationship."  However, with minimum phase, the relationship between frequency and timing/phase is *not* linear, and so I am puzzled as to what "one-to-one relationship" means in this case.

 

If it is possible, would you be able to ask your friend, who surely knows more than I do about this?

Mario Bon replies:

 

There is always a lot of confusion between the meaning of minimum phase and linear phase.
In minimum phase systems there is the possibility to determine the transfer function knowing only its amplitude (modulus of the frequency response) or only its phase. So not only is there a 1-to-1 relationship between time response and frequency response but also between amplitude response and phase response.
In linear phase systems it is not possible to derive the frequency response from the phase response because this contains only one piece of information (the constant group delay). So you need to know the frequency response. There remains the 1-to-1 correspondence between response in time and response in frequency.

 

Networks or those stuff made with resistors, capacitors, inductors and transformers that do not use all-pass networks and where the path between input and output is unique are minimum phase. It follows that speaker systems, if they have no defects, are minimum phase systems.

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18 hours ago, bibo01 said:

OK, fine. I'll stop here.

So you were very happy with your #1, but when #2 arrived you realized that you were "living in an ignorant bliss".

It seems to me that now you are happy "living an ignorant bliss #2". As you are happy, however, it's fine by me and I will not waste my time any further. 

Perhaps my explanation wasn't as clear as it could have been but my point was that the system sounded find with Config #1 and the Freq Resp looked good as well (IMO)....but despite those two things I failed to know or realize at the time the other issues shown were also present (ie..Pre-Ringing, High Distortion in the Bass Region..etc..etc)

 

The current configuration doesn't show the same signs of high distortion, pre-ringing..etc.etc but its' Freq Resp plot is not as nice (IMO) but sounds even better.

 

These are the points I was making. Could I crank up the vol knob of the Subs and make a nice big hump from 15-30hz to make the current Config #2 look like Config #1....yes indeed I can but knowing what I know now about the end result of doing that I will no longer be attempting to duplicate Config #1's Freq Resp graph unless I decide to purchase more Subs in order to achieve the same type of chart but without all the added distortion that went along with it.

 

All the x-overs I am using in Audiolense are of the Linear Phase type. Honestly I've not tried to create any Minimum Phase x-overs as of yet but certainly could if I wanted to.

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15 hours ago, Bob Stern said:

REW graphs & axis:  

 

In REW, if you hover the mouse near the upper left corner of a graph, + and – buttons appear allowing you to expand/compress the scale.  Above the upper right corner of the graph are 4 icons, one labelled Limits.  Click that and then type your desired numerical upper and lower limits for the X and Y axes.

 

Your graphs would be much more helpful if you expand the vertical axis to show the full range.  In the horizontal axis, if you're focussing on the bass response, you should set the upper limit of the graph to the upper bass frequency of interest.

Hello,

 

I can post any additional info/graphs folks may want to look at in whatever view/format. In the case of the question above which graph would you be referring to when you mention about expanding its Vertical axis?

 

Posting these types of graphs in the format that all can agree on can be a challenge. Some folks want it zoomed out while others want it zoomed in.

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2 hours ago, cjf said:

In the case of the question above which graph would you be referring to when you mention about expanding its Vertical axis?

 

I'm not making a request; I'm merely offering a suggestion on how to make the REW graphs more useful to you.  A graph in which there's lots of white space above and below the curves would be more useful if you zoom in so that the curve occupies most of the displayed Y-axis.  Likewise, if you're examining the bass, you can see more detail by reducing the upper frequency limit on the X-axis.

 

Also, when running the algorithm to determine bass EQ, the REW developer recommends setting smoothing to Variable instead of 1/12 octave.  "Variable" applies almost no smoothing in the bass and increasing smoothing in the treble.  See the help topic "EQ Window":

http://www.roomeqwizard.com/help/help_en-GB/html/eqwindow.html

Mac Mini (2012 i7) > HQPlayer > RME ADI-2 v2 > Benchmark AHB-2 > Thiel 3.7

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1 hour ago, Bob Stern said:

 

I'm not making a request; I'm merely offering a suggestion on how to make the REW graphs more useful to you.  A graph in which there's lots of white space above and below the curves would be more useful if you zoom in so that the curve occupies most of the displayed Y-axis.  Likewise, if you're examining the bass, you can see more detail by reducing the upper frequency limit on the X-axis.

 

Also, when running the algorithm to determine bass EQ, the REW developer recommends setting smoothing to Variable instead of 1/12 octave.  "Variable" applies almost no smoothing in the bass and increasing smoothing in the treble.  See the help topic "EQ Window":

http://www.roomeqwizard.com/help/help_en-GB/html/eqwindow.html

Thanks and I appreciate the tip.

 

As another side note, One thing that I learned the hard way during this process was that for whatever reason or another I could not rely on the combined results seen in REW of more than one sub being measured at the same time and have those results appear the same way within Audiolense once the correction filters were generated.

 

Part of my process while determining where to place the various Subs in the room was to use REW first to get an idea if a movement here or there of a particular Sub/Subs would result in the reduction of a dip or spike across the measured Freq range I would use for the Subs (10-500hz). Once I achieved a decent measurement of each Sub on its own I would then start to do sweeps with combination of Subs together. I spent a few weeks doing this and thought I found the best spots once the combined measurements where taken into consideration only to find out those combined results never seemed to result in the same outcome after corrections were done in Audiolense. On a whim one day after continued failure I decided to just worry about achieving the best measurement for each Sub individually in REW. As soon as I did that everything started to fall into place and make sense and the correction filter Simulations within AL started to look like what I saw while using REW (for the most part). As a side note, I wish REW would allow sweeps of more than two channels at a time but unfortunately it does not.

 

I guess my point being that I'm not sure if using some of the Simulation features in REW would actually translate into the same result after corrections are generated/applied with AL. It appears the combined Sub results do not but maybe its just me and something I was doing incorrectly.  I can say that the Room Sim feature in REW doesn't translate at all in my room with the actual measurements. I assume this is mostly due to the irregular shapes of the walls, the very open layout to other rooms and the 12ft vaulted ceiling that runs down the center of the room none of which are variables that can be plugged into the Room Sim feature of REW.

 

Unfortunately my main Right channel sits directly under this peak in the ceiling and it results in a very nasty room mode to fight with. With no correction in the picture that channel is 8db louder than the LCH is at various lower Freq. There is also a nasty Null in the Center of the room a few feet in front of the MLP. Standing in that spot and almost all bass literary disappears. Its my understanding that subs on each side of a Null are out of Phase with each other so you have to get creative with "Aiming" the Sub in different directions I order to end up with all speakers being in phase with each other once all corrections are done.

 

 

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Re. your subs, I would encourage you to look at the work of Geddes and Welti re. the multiple sub approach.  I now have four and saw stepwise improvement while adding (3 was great, the 4th didn't add a huge amount).  Many of the longstanding audiophile beliefs are turned on their heads by this research/approach.  Acoustics and measurements below the room's Schroeder frequency are very different from those above.  Some of the reasons I haven't delved deeply into DRC is that I would like to do as much acoustically first and that it isn't clear to me how to incorporate measurements --> filters with all the subs playing.  It doesn't matter what each one is doing individually, but what they are all doing together.

 

https://www.harman.com/documents/multsubs_0.pdf

 

https://mehlau.net/audio/multisub_geddes/

 

https://www.diyaudio.com/forums/subwoofers/134568-multiple-subs-geddes-approach.html

 

Bill

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5 channels (L+R + 3 subs) and audiolense are really complex.

My gut feeling about the REW frequency responses of Config 1 (2 subs) vs Config 2 (3 subs), assuming Audiolense was run and setup correctly is that Audiolense uses psychoacoustic correction so the frequency response filtering would be different than REW's measurements. That's probably why the frequency response of the bass sounds the same in Config 1 vs 2 but the REW measurements look different.

 

As for whether there is further room for optimization from Config 2, there probably is. I'm still unclear whether the speakers are running full range or not. It seems the subs are running 10-200Hz. I mean, with good speakers, you always wonder if you can run the speakers 50-20kHz and just run the subwoofers 10-50Hz or set the crossover frequency elsewhere, e.g. 40Hz, 80Hz, 100Hz, etc. Obviously, if you're running the speakers full range, it is possible that with Config 1 your speakers + subwoofers are enhancing each other in the bass region but in Config 2 your speakers and subwoofers are cancelling each other out, leading to a lower bass frequency response measured in REW.

 

The other issue is the amount of pre-ringing from the speakers. The True Domain Subwindow Cycles before and after peak is set at 5 for 10Hz and 3 for 96kHz. This is extremely system dependent and sometimes you can push the cycles to 6 for 10Hz but to prevent excessive preringing, you need to set the cycles to 1 for 96kHz. If it sounds pretty awesome right now, I would suggest trying 5 for 10Hz and 2.5 for 96kHz and see if you like it better. And then try 5 and 2. I personally use Acourate instead of Audiolense and I have my own "optimization" preferences where I tweak these numbers to 0.1 accuracy for months. I have a very asymmetric setup so I think my system is like 4 & 2 on the left and 6.2 and 2.7 on the right or something like that. But bottomline is that I think 3 for 96kHz maybe too high for your system.

 

Ultimately, I think what most people are saying is that:

1) You can't completely correct for room issues and speaker/subwoofer issues. I think that's true but all DSPs (or stereo systems) are about compromises and tradeoffs (sadly, just like life)

2) There are these ideal frequency responses we should target except from my experience, different people have different preferences for frequency responses. So if you're happy with what you're hearing, you're probably good.

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9 hours ago, ecwl said:

5 channels (L+R + 3 subs) and audiolense are really complex.

My gut feeling about the REW frequency responses of Config 1 (2 subs) vs Config 2 (3 subs), assuming Audiolense was run and setup correctly is that Audiolense uses psychoacoustic correction so the frequency response filtering would be different than REW's measurements. That's probably why the frequency response of the bass sounds the same in Config 1 vs 2 but the REW measurements look different.

 

As for whether there is further room for optimization from Config 2, there probably is. I'm still unclear whether the speakers are running full range or not. It seems the subs are running 10-200Hz. I mean, with good speakers, you always wonder if you can run the speakers 50-20kHz and just run the subwoofers 10-50Hz or set the crossover frequency elsewhere, e.g. 40Hz, 80Hz, 100Hz, etc. Obviously, if you're running the speakers full range, it is possible that with Config 1 your speakers + subwoofers are enhancing each other in the bass region but in Config 2 your speakers and subwoofers are cancelling each other out, leading to a lower bass frequency response measured in REW.

 

The other issue is the amount of pre-ringing from the speakers. The True Domain Subwindow Cycles before and after peak is set at 5 for 10Hz and 3 for 96kHz. This is extremely system dependent and sometimes you can push the cycles to 6 for 10Hz but to prevent excessive preringing, you need to set the cycles to 1 for 96kHz. If it sounds pretty awesome right now, I would suggest trying 5 for 10Hz and 2.5 for 96kHz and see if you like it better. And then try 5 and 2. I personally use Acourate instead of Audiolense and I have my own "optimization" preferences where I tweak these numbers to 0.1 accuracy for months. I have a very asymmetric setup so I think my system is like 4 & 2 on the left and 6.2 and 2.7 on the right or something like that. But bottomline is that I think 3 for 96kHz maybe too high for your system.

 

Ultimately, I think what most people are saying is that:

1) You can't completely correct for room issues and speaker/subwoofer issues. I think that's true but all DSPs (or stereo systems) are about compromises and tradeoffs (sadly, just like life)

2) There are these ideal frequency responses we should target except from my experience, different people have different preferences for frequency responses. So if you're happy with what you're hearing, you're probably good.

Hello,

 

In both Config states I am using a cross over for the Main towers. In Config #1 the x-over was set to 62hz I believe and in the current Config #3 I am using an x-over of 60hz. In the past I tried running the Main Towers full range and just using an x-over on the Subs but the results were not very good. I might give it try again now that my system is a bit different than it was at the time when running the Main Towers full range to see what the results are just for the heck of it.

 

I have all the controls on the Subs defeated and am using their LFE Inputs which is supposed to kill pretty much everything except the Vol control level on them. In the Audiolense Speaker Setup window I have the LFE cutoff set to 250hz and am Routing all Bass to all Subs.

 

For the settings being used in the Correction Procedure Designer for my current setup (ie..Config #2) I dont think I've tried to set the 96K Window to "1" yet. I did on the other hand play quite a bit with the 10hz Window but,at least according to the Simulation results, when I did that the graph started to look like a mess and at least one of the Subs would go out of Phase with all the others while viewing the Step Response Simulation results.  I'll give a few more combinations a shot though including some of your suggestions to see how it goes.

 

The TTD per Driver setting in CPD would also make a mess of things in terms of the Simulations in AL. I hear this setting though can go either way and is very system dependent. The Simulations are showing it to not be a good choice for me for whatever reason.

 

There have been several times though that the AL Simulations would look like a mess but the REW results would look better by a decent margin. Perhaps I'm putting too much weight into the AL Simulation and need to try a few more CPD combinations that look not great anyway just to see what the outcome is.

 

Thanks for your thoughts on this post

 

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