JBL M2 Audiolense Digital Crossovers w/Subs

[Brad]

How did you come up with the center position for the red?

I used the acourate microphone alignment tool - it does a cross correlation of pulses played through the tweeter. This should be accurate to within a sample (or 7mm)

Thanks Ray for the video, it shows qualitatively similar behaviour to the green trace.
For the red trace, it's possible acourate has built in a delay between the L and R tweeters (assuming correct mic position). I will have to check the filter files.

 

[RayDunzl]

I used the acourate microphone alignment tool

I looked at their freebies, didn't see it... My AcourateDRC is a real lite version, no tools.

Anyway I use REW a lot, so went that direction. Same principles, I suppose.

 

[dallasjustice]

@Brad I would post your question about your R/L contemporaneous sweep on the Acourate forum. Uli should answer that. He’s super helpful.

 

[RayDunzl]

@dallasjustice

Since there is no calibration file loaded into REW

Are the SPL readings as displayed by REW "correct" in the posted .mdat files?

 

[dallasjustice]

@dallasjustice

Since there is no calibration file loaded into REW

View attachment 10788

Are the SPL readings as displayed by REW "correct" in the posted .mdat files?

I do have an Earthwork cal file installed in REW. I’m not sure what you posted there.

Oh wait you are talking about SPL.

It should be pretty close to 83db.

 

[dallasjustice]

Canare 4S11 bare wire w/ tinned ends. I’m officially not kewl:

 

[RayDunzl]

My mistake...

Your .mdat has no microphone calibration (like I have, and looked for), but instead a Soundcard Calibration (which I don't need and didn't look for).

Never mind...

 

[RayDunzl]

You smoked me on the equivalent SPL distortion.

Yeah yeah, I know.

See, my mules don't like people laughing. They get the crazy idea you're laughing at them. Now, if you'll apologize, like I know you're going to, I might convince them that you really didn't mean it.

---

Here are the rules:

The first rule of Fight... no, that's another movie.

You have to spot me a little... I get to use two mains (no subs), and the loudest old trace I could find (to match your levels), about 6dB louder at 1kHz, so my Left and Right should been at about the same level as you, just to be fair. Stereo speaker traces run 6dB SPL above single speaker traces, for the same signal level.

Example. Left, Right, and Both (it's not the measurement used below, not loud enough).



You get to use your subs.

My trace is flatish, yours sloped a bit.

All 1/12th smoothing. I'm measuring dead center at 10 feet.

Contestants:

JBL M2 with sub array and active crossovers

MartinLogan reQuest, 12" sealed woofer, 15 x 48" electrostatic panel, 180Hz passive cross, 1998 model, run full range with AcourateDRC in the path.

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I'm royal pupleish, you're L/R blue/green.

Here's my two speaker 48 Hz hole, which is much reduced on individual L/R/traces. You don't have the phase anomaly I have. My room is open on the left rear corner, I think yours is closed.

Phase - You win on the bottom end, then...

Hey! Wait a minute! Where'd you go?

Good job on both here... 48Hz phase problem intrudes on mine. If I sloped the high frequency, mine might twist up on the right end too.

Nothing to see here, move along.

Step back...

Stretched this display all the way out to the left, wondering what you have out there. Left of zero is some sort of distortion image (per REW). I have it closer to zero time.

I have greater direct to reflected/reverberated ratio, maybe, on the good part to the right of zero.

Hmm... Looks like phase comes into play again on Group Delay.

And there's my 48Hz hole simply ruining my bass trace.

My 220Hz hump is likely related to the dipole bounce off the wall behind the speakers.

Game, set, match.

Did you keep score?

Who won?

Sorry I trashed your thread. You can trash one of mine sometime.

 

[dallasjustice]

ESL speakers are hard to beat in the time domain. That’s for sure. I’m surprised the JBL has lower distortion in the midrange.

The thing I love about ESL speakers is that low distortion immediacy they have. They can be very realistic sounding. With the M2 I hear a lot of the same thing I’ve heard before from Quads. In my book, that’s a good thing. I know the ESLs aren’t in favor among the scientists. But it’s throwing the baby out with the bath water to dismiss them.

3 things:
Our speakers aren’t in the same room. They aren’t likely being played at the same level and your target curve is more friendly to get better time domain measurements. Do you prefer to listen with a totally flat target?

 

[RayDunzl]

ESL speakers are hard to beat in the time domain. That’s for sure. I’m surprised the JBL has lower distortion in the midrange.

Time domain - interesting. The flat phase I report has been called "impossible" in some places. Your's will be flat nearfield (I anticipate) but it gets lost (reflections?) before it reaches the listener.

Distortion was where I felt smoked (when I made new single speaker measurements below)

3 things:
Our speakers aren’t in the same room. They aren’t likely being played at the same level and your target curve is more friendly to get better time domain measurements. Do you prefer to listen with a totally flat target?

Oh yes, different rooms.

And very different speakers. Although, I sometimes imagine the panel as the mouth of a pair of large directional horns... Consider a 15 x 48 narrow dispersion horn mouth with a piece of saran-wrap over the end.

As for "totally flat" trace - I don't have much reflection here, so it's essentially all direct... I can't hear up high, but get no complaints from those that do, so...

I figure it's a nice undistorted high, with exemplary phase all the way to the listener, so that may be a factor. Music always rolls off pretty sharply (except when it doesn't) above 1 or 2kHz, so i just don't see a problem being a couple of dB hot when the signal is already 20~40dB down itself at those frequencies

And, the old Fletcher-Muson curves are pretty flat at 80-100dB below 1000Hz, so I don't add a bass boost. They show "less sensitive" in high frequencies (again not worried about flatish high end).

I figure that's my critical loudish listening level (80 average - 105dB peaks). And after fooling around with "less is more" on the bass side, I prefer less (or at least well-balanced).

The newer ISO curves have more power in the far lows for "equal loudness", I played with matching, found it boomy/tubby when it wasn't inaudible. Maybe the ISO guys are bass-heads, and Fltcher and Munson et. al. hadn't been biased by modern boom-boom...

---

Smoked!

I did single speaker at (almost) the same levels as yours three days ago, I had to look since yours looked so good. But those traces (a couple of days ago) didn't look so pretty to me. It's been a while since I did a tune-up, some extra junk (tax time) is laying around the room, so I went back in time and found a high SPL measurement that looked right, and matched your levels.

Here are the three days ago with an filter generated some months ago and closely matching levels for my L and R.

You're red, I'm blue (this time with flanking cheesesubs):

Here's where I felt somewhat unexpectedly smoked.

My favorite "you can't hear that" measurement - narrowband hash (I think you can, spacially):

You (and I, when my JBLs are playing) show many more reflections from the room in the 7 to 20ms area of the extended impulse response.

Basically I have 7 (dipole) and 27ms (speaker to wall above my head to wall behind speakers back to mic) reflections.

The JBL spray the walls and ceiling. The panels have little going off to the sides or ceiling.

Ok, that's enough.

 

[dallasjustice]

Maybe ESLs in larger rooms need a flatter curve because there are fewer off axis reflections. Do you have a different curve with the JBLs?

Do you notice a difference in 3D image between the JBL and the ESLs?

I think the m2 sprays more sound laterally and vertically than even the 4367. I even repositioned my speakers and LP because the M2 was so different. I’ve always felt like I needed to have my speakers at least 9’-9’6” apart to get a big enough soundstage. With the M2 they are setup only 8’ apart. The LP is 9’ back (so not a perfect equilateral) and pointed straight at LP. The M2 are great at envelopement. They play way outside the boundary of the speakers. I was listening to cool EDM the other night and could hear sound coming almost all the way back to my ear position. They also resolve very fine detail and are very articulate; vocals are much more clear.

I did make some changes to my room tho. I removed my couch and moved a couple of RPG BAD panels around to absorb some mid bass Allison effect. I took out three nice big dips. I doubt your room has that many nasty reflections in the 100-300hz. But I found the REW signal generator to be super helpful at quickly discovering the boundary causing the null. I just play the null frequency from the appropriate speaker and pull up the REW mic input meter. I start walking about the room with my RPG BAD panel until I find the boundary that increases the amplitude by about 10db. I did the same thing with my rug/felt pads. I’m a slow learner. But at least I can learn.

 

[RayDunzl]

Maybe ESLs in larger rooms need a flatter curve because there are fewer off axis reflections. Do you have a different curve with the JBLs?

I'm rather insensitive to HF so can go with a slope there or not. Recorded music slopes drastically (watch an RTA) so I fail to see the important point of adding more slope. Very rarely (and it is the recording) and I bothered by an excess of HF.

Do you notice a difference in 3D image between the JBL and the ESLs?

I'm Listening at 10 feet, the JBL is set outboard of the ML, and too close to the wall. They might do much better nearfield (as intended) and away from lateral reflections.

I should do it all again, and give the JBL some better advantage, but for now, just comparing how they are.

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Imaging is the major difference to me. Secondarily, SPL, as the little JBLs get harmonically distorted much sooner than the ML/Krell at higher levels.

---

From memory and prior casual "testing" and buddy listening

--- When critically listening to music, sweet spot, eyes closed...

Switching back and forth, the initial impression is, the JBL is much "wider" (but like a stretched out image like when you watch an old 4:3 movie in 16:9) , the ML "narrower". After a while your ear finds all the width that is actually there, and it doesn't sound "narrow" at all.

JBL phantom center less precise

JBL "fuzzier", ML "focused"

JBL "less clarity", ML "very clean tonally"

--- With Correlated (mono) Pink Noise

JBL - spread out sound, ML - more hard centered.

--- With Correlated Pink Noise - and putting the speaker signal in and out of phase

JBL - minimal change (phase issues that blur the difference). One evening two of us were unable to reliably say they were "in" or "out" listening to music signal. With ML, no problem at all.

ML - Obvious center (when in phase) and all over the room sound (when out of phase) as expected.

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With AcourateDRC and listening casually (particularly when not in the sweet spot) I find them interchangeable and can easily forget which is playing - have to look at the lights (which can gt out of sync with which is playing - two zones) and still have to walk over to see.

The M2 are great at envelopement. They play way outside the boundary of the speakers.

Yes, the ML will put sound at my hard left and right (180 degree soundfield) when its in the recording. Listened to some Q-sound a couple of days ago, that had it. Some of the Olympic Coverage on NBC had it, among their various mic setups.

Normally, there's just no sense of speakers or walls, just a big focused soundfield (critically listening, of course).

I just find the ML to give a more natural presentation here.

Same preamp, JBL is internally biamped active, ML with Krell and supplanted with cheap subs I don't really need. Might get some good subs, someday.

 

[dallasjustice]

Might get some good subs, someday.

I’d say rythmik are a good choice. I think they are great performers (low distortion/high output), easy to buy and cheap compared to many others.

 

[RayDunzl]

My buddy has a pair of the paper cone 12". F12G

"The GR drivers use a lower mass paper cone, which has a slightly better transient response.
The result is slightly better dynamics. At higher output, due to less cone stiffness, the sound
may become softer due to the pressure placed on the cone.

The GR drivers also have a more extended response, allowing a higher crossover point if desired.

The performance can be described as "different" rather than superior or inferior."

 

[DonH56]

I have four F12's, the Al cone models. Should be lower breakup at higher levels and thus slightly less distortion. Between the servo and the low frequency bandwidth not sure I fully buy into the transient response but paper may exhibit less ringing. I talked with Brian (Ding, Rythmik) quite a bit when deciding what to get, though we diverged somewhat onto other topics since we have similar day jobs.

 

[dallasjustice]

The F8 uses paper cone drivers. I can’t say they sound different. I would say there’s a big adavantage to running subs at much higher frequencies than what is usually done. So in a way it is different. But I think it’s because of the high crossover at 175hz.

 

[andrew]

@dallasjustice So, basically, you’ve turned the system into a 4-way with the mid-bass and subs located to avoid cancellations from the walls. Great idea and thread. Why locate the subs on the rear wall? Would these work as well on the front wall? And, in this configuration, are all the drivers time aligned at the listening position?

 

[dallasjustice]

@dallasjustice So, basically, you’ve turned the system into a 4-way with the mid-bass and subs located to avoid cancellations from the walls. Great idea and thread. Why locate the subs on the rear wall? Would these work as well on the front wall? And, in this configuration, are all the drivers time aligned at the listening position?

That is exactly correct. The listening position is much closer to the rearwall. The rearwall causes a boundary interference at around 35hz. OTOH, the front wall causes no boundary interference because the room is very long (24’). So the boundaries that cause the biggest problems are the ones nearest to the listening position.

The best way to think about boundary interference is to start from the listening position. There’s a formula which can help identify the distance from LP based on the frequency of the null.

One of the common misconceptions that audiophiles have about bass anomalies is that some folks think all bass problems are room modes. This isn’t correct. If you think in terms of listening position, there’s actually two bass problems:
1. Room Modes (minimum phase).
2. Boundary Interference or Allison Effect (nonminimum phase).

They need to be viewed as two distinct problems because the solutions for each problem are very different and mostly don’t overlap one another.

 

[hvbias]

Just came across this thread from a link in the DAC3 measurements thread. This is seriously some tremendous reading.

Any links to read up more about the Allison effect? Google turns up surprisingly little except this page: http://david-janszen.squarespace.com/blog/speaker-setup-minimizing-the-allison-effect2015321

 

[DonH56]

Try Speaker Boundary Interference Effect, SBIR: https://www.google.com/search?q=aco...rome..69i57.3062j0j4&sourceid=chrome&ie=UTF-8