dallasjustice
Major Contributor
I first became seriously interested in purchasing the JBL M2 when I was with @amirm at CEDIA 2015. I heard the Harman demo room and was shocked at the sound quality I heard. The Harman demo at CEDIA is like waiting in line for the Pirates of the Caribbean ride at Disney World with my kids. Its something you have to do if you are there.
I've always been a bit of a subwoofer fanatic. My room is approximately 14'6" wide, 24' long and 9'3" tall. It is an almost perfect rectangle except the small entry way at the rear. When I built the room on to my home about 6 years ago, I had no idea what I was undertaking. The last 6 years has been a learning adventure. I started off trying to throw money at my system. I started buying expensive speakers, amps, DACs and even cables. At this stage of my journey, I was convinced not by measurement and science but by the dollar. This is how it goes: dealer sells you an expensive pair of speakers. You like them, but then you are convinced that if you spent X dollars on speakers, you also MUST spend X dollars on power cables and speaker cables and DACs and Amps and on and on.
Fortunately, I could still hear that the bass quality wasn't very good in my room. So I started searching for new information. I had previously learned about Bernt Rønningsbakk about 10 years ago online reading AVSforum. He had a new product called Audiolense. So I bought a measurement microphone, Lynx card and used the software with Bernt's help. I really didn't understand how it worked or what I was doing. I quickly gave up on it. Bernt was a gentleman and permitted me to sell my license to someone else who could better use it. At that time, I learned that crossovers could be digital instead of analog. I asked Bernt about it at the time but never really pursued it because I thought it was too complicated. I later met Nyal Mellor who began the deprogramming process on me. I thank him for that. Nyal re-introduced me to digital room correction (a misnomer I will refer to it herein as "DSP"). I bought a DEQX and used a subwoofer pair with a digital crossover. I really like the improvement in bass quality. I had previously spent a lot of time money on room treatments and system setup to optimize bass in my room. Even with the best technology is bass mode control (RPG modex plates), I could only get a little better results.
Later on, I met Dr. Uli Brueggeman who is the designer of software called Acourate. Uli is a meticulous German engineer and audiophile who possesses didactic skills and patience unmatched in my experience. Uli helped me setup active crossovers using both 2 subs and then 4 subs. At that time, I learned more about subwoofer integration after reading an AES paper from Todd Welti. I was also introduced to more subwoofer research in an AES study conducted by Fazenda. Although Welti and Fazenda approached the problem of room mode control in different ways, they both seemed to agree on mono subwoofer integration. IOW, each subwoofer gets a summed R/L signal. That approach worked well for me. I did notice tho, that I could never get "perfect" time domain integration with mono subs. However, mono subs always gave me better frequency response than 2 stereo subs. So there was a trade-off.
After exploring all sorts of mono sub arrays. I found the 2 mono "source-sink" array studied by Fazenda to be superior to even the 4 mono midwall sub array that Welti advocated for rectangular rooms. This "source sink" had the advantage of being able to eliminate otherwise untreatable length modes (1,0,0 and 2,0,0). The disadvantage to this array is that it can never be truly time aligned. (the rear sub must be in opposite electrical polarity and delayed to reach LP a little bit after the front sub).
I recently found a pair of JBL M2 from the family of a deceased East Texas dealer. I got a great price and I thought I'd try my hand at setting the M2 up using digital crossovers generated by Audiolense. @amirm and I previously discussed the Harman system for subwoofer integration with the M2. Although the Harman method is very advanced, I never thought I would be happy with it due to the controlled roll-out of this method. Basically, its dealer-only setup. I also reject any closed box DSP application. Harman only offers off-the shelf DSP inside either their SDEC or their Crown Amps. I know that any digital crossover or EQ in a box solution will be a digital compromise. (limited number of taps, no linear phase crossovers) I also learned that Harman's out of the box DSP sadly does NOT time align the D2 tweeter with the midwoofer. For me, that's too many compromises. I know I can implement a better linear phase crossover and perfectly time align the drivers using Audiolense. (the same could be done in Acourate but I chose to use Audiolense)
A note about time domain. I've read Sound Reproduction. I'm aware of the paucity of science that show any advantage to time aligned drivers compared to typical minimum phase implementation. I accept the lack of research in this area. BUT, I can speak from my own experience. I've time aligned many different speakers in my room and have always heard a big improvement in 3D image and image accuracy. I think some audiophiles have morphed Toole comments about the lack of research in this area into proof that driver time alignment cannot be perceived. That's simply not the case. There's just not enough research in this area and more needs to be done, IMO.
I'm not going into detail about the M2 vs. the 4367. I've owned both in the same room. Anyone could look at the Harman spin data and reach the conclusion that the M2 measures a little better on and off axis. This is why I chose the M2 for this project. The M2 may be the finest measuring loudspeaker available at this time. So I wanted to hear it setup in a way I thought I could achieve ultimate playback in my room. Yes, I did that.
I want to thank @mitchco for all of his help. For those of you who don't know Mitch, you should know him. Mitch is the leading DSP evangelist. He's written numerous articles and has now written a book on how to implement DSP. His book is called Accurate Sound Reproduction. Mitch's guidance and insights were critical to me getting the M2 setup. Thank you Mitch!
I'm going to post the most important REW measurements of the M2 setup in this post. I will follow with additional info and pics regarding the new 4 stereo sub array I'm using with the M2.
I've always been a bit of a subwoofer fanatic. My room is approximately 14'6" wide, 24' long and 9'3" tall. It is an almost perfect rectangle except the small entry way at the rear. When I built the room on to my home about 6 years ago, I had no idea what I was undertaking. The last 6 years has been a learning adventure. I started off trying to throw money at my system. I started buying expensive speakers, amps, DACs and even cables. At this stage of my journey, I was convinced not by measurement and science but by the dollar. This is how it goes: dealer sells you an expensive pair of speakers. You like them, but then you are convinced that if you spent X dollars on speakers, you also MUST spend X dollars on power cables and speaker cables and DACs and Amps and on and on.
Fortunately, I could still hear that the bass quality wasn't very good in my room. So I started searching for new information. I had previously learned about Bernt Rønningsbakk about 10 years ago online reading AVSforum. He had a new product called Audiolense. So I bought a measurement microphone, Lynx card and used the software with Bernt's help. I really didn't understand how it worked or what I was doing. I quickly gave up on it. Bernt was a gentleman and permitted me to sell my license to someone else who could better use it. At that time, I learned that crossovers could be digital instead of analog. I asked Bernt about it at the time but never really pursued it because I thought it was too complicated. I later met Nyal Mellor who began the deprogramming process on me. I thank him for that. Nyal re-introduced me to digital room correction (a misnomer I will refer to it herein as "DSP"). I bought a DEQX and used a subwoofer pair with a digital crossover. I really like the improvement in bass quality. I had previously spent a lot of time money on room treatments and system setup to optimize bass in my room. Even with the best technology is bass mode control (RPG modex plates), I could only get a little better results.
Later on, I met Dr. Uli Brueggeman who is the designer of software called Acourate. Uli is a meticulous German engineer and audiophile who possesses didactic skills and patience unmatched in my experience. Uli helped me setup active crossovers using both 2 subs and then 4 subs. At that time, I learned more about subwoofer integration after reading an AES paper from Todd Welti. I was also introduced to more subwoofer research in an AES study conducted by Fazenda. Although Welti and Fazenda approached the problem of room mode control in different ways, they both seemed to agree on mono subwoofer integration. IOW, each subwoofer gets a summed R/L signal. That approach worked well for me. I did notice tho, that I could never get "perfect" time domain integration with mono subs. However, mono subs always gave me better frequency response than 2 stereo subs. So there was a trade-off.
After exploring all sorts of mono sub arrays. I found the 2 mono "source-sink" array studied by Fazenda to be superior to even the 4 mono midwall sub array that Welti advocated for rectangular rooms. This "source sink" had the advantage of being able to eliminate otherwise untreatable length modes (1,0,0 and 2,0,0). The disadvantage to this array is that it can never be truly time aligned. (the rear sub must be in opposite electrical polarity and delayed to reach LP a little bit after the front sub).
I recently found a pair of JBL M2 from the family of a deceased East Texas dealer. I got a great price and I thought I'd try my hand at setting the M2 up using digital crossovers generated by Audiolense. @amirm and I previously discussed the Harman system for subwoofer integration with the M2. Although the Harman method is very advanced, I never thought I would be happy with it due to the controlled roll-out of this method. Basically, its dealer-only setup. I also reject any closed box DSP application. Harman only offers off-the shelf DSP inside either their SDEC or their Crown Amps. I know that any digital crossover or EQ in a box solution will be a digital compromise. (limited number of taps, no linear phase crossovers) I also learned that Harman's out of the box DSP sadly does NOT time align the D2 tweeter with the midwoofer. For me, that's too many compromises. I know I can implement a better linear phase crossover and perfectly time align the drivers using Audiolense. (the same could be done in Acourate but I chose to use Audiolense)
A note about time domain. I've read Sound Reproduction. I'm aware of the paucity of science that show any advantage to time aligned drivers compared to typical minimum phase implementation. I accept the lack of research in this area. BUT, I can speak from my own experience. I've time aligned many different speakers in my room and have always heard a big improvement in 3D image and image accuracy. I think some audiophiles have morphed Toole comments about the lack of research in this area into proof that driver time alignment cannot be perceived. That's simply not the case. There's just not enough research in this area and more needs to be done, IMO.
I'm not going into detail about the M2 vs. the 4367. I've owned both in the same room. Anyone could look at the Harman spin data and reach the conclusion that the M2 measures a little better on and off axis. This is why I chose the M2 for this project. The M2 may be the finest measuring loudspeaker available at this time. So I wanted to hear it setup in a way I thought I could achieve ultimate playback in my room. Yes, I did that.
I want to thank @mitchco for all of his help. For those of you who don't know Mitch, you should know him. Mitch is the leading DSP evangelist. He's written numerous articles and has now written a book on how to implement DSP. His book is called Accurate Sound Reproduction. Mitch's guidance and insights were critical to me getting the M2 setup. Thank you Mitch!
I'm going to post the most important REW measurements of the M2 setup in this post. I will follow with additional info and pics regarding the new 4 stereo sub array I'm using with the M2.
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