The All Analog, All Lamm, PBN M2!5 System of JeffreyT

Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
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Beverly Hills, CA
#1
I have visited JeffreyT, a member of the Long Beach, CA division (of which I consider myself an honorary member) of WBF, several times over the last couple of years. Jeff, like me and PeterA, is 100% analog, 0% digital. Like me (someday, anyway) Jeff plays only vinyl and tape.

Jeff’s primary musical interest is jazz, but he also likes some classical and some classic rock and pop. He has a large collection of jazz recordings, and is very knowledgeable about the genre.

About a year ago Jeff acquired from Peter Noerbaek, founder of PBN Audio, a pair of M2!5 loudspeakers. According to the PBN website:

“Two JBL drivers are the heart of the system: First, twin JBL 2235H 15” woofer classics, with a low-loss magnetic structure and Symmetrical Field Geometry, which reduces harmonic distortions to near zero. The second is the inimitable JBL D2430H mid-range/tweeter compression driver, with dual-diaphragms. The drivers are aligned “in time” via their amazing 900 Hz charge-coupled crossovers.”

The standard version of the speaker has the compression drivers and waveguide atop two 15 inch woofers. Jeff requested a woofer - wideband driver - woofer (M-T-M type) configuration, so the compression drivers are in the middle of the woofers. I think this is a brilliant request, and it is how I would’ve ordered the speakers myself.


46C79B93-A779-4C26-BCF7-957D6C137A4D.jpeg

Jeff’s turntable is the Acoustic Signature Ascona sitting on top of its matching stand. I have always liked both the design and the look of a turntable the feet of which sit on top of legs which visually and physically extend the turntable all the way to the floor on its own integrated stand. As turntables go I think the Ascona with its integrated stand is a beautiful and sleek, yet extremely serious and industrial-looking, design. The machining quality of the plinth is fantastic.

Jeff has a wide variety of contemporary and vintage cartridges and headshells, and he enjoys cycling through them on his SME 3012R. Presently Jeff’s favorite cartridge is an Ortofon SPU.

Jeff has a full suite of Lamm electronics: the LP2.1 Deluxe phono stage; the LL2.1 Deluxe line stage; and the ML1.1 80 watt per channel mono amplifiers. A skeptic of very expensive cables, Jeff has settled on Belden 8402 interconnects with Switchcraft RCA connectors, made by Jeff Day, after comparing them to Kimber Cables. Power cables are Ching Chengs.

Taking it all together, on paper, this system checks a lot of my personal design preference boxes:

1) all analog,

2) all tube,

3) fairly tall speakers for height and scale,

4) M-T-M driver configuration,

5) simple, two-way speaker,

6) wide-band (900 Hz and up) driver,

7) big woofers to move air,

8) woofers playing high up in frequency, and

9) overkill amplifier power given the sensitivity of the speakers.

While I heard the system three times before several months ago, shortly after Jeff installed the new PBN speakers, it wasn’t until I listened with PeterA and Jeff for about five hours recently that I realized how great this system is. Jeff reports, and I agree, that the speakers have taken a long time to break in.

Dynamics, detail, realistic leading edge transient (PeterA is an expert on this sonic attribute, and I take his analysis on the matter), naturalness and openness are some of the gifts of this system. It is utterly unfatiguing (as are, to these ears, all Lamm-based systems).

The system has a very open, live, dynamic, high jump factor sound. Overkill amplifier power on sensitive speakers is what it takes to achieve this.

I continue to believe that musical preference significantly drives loudspeaker selection. It is no coincidence that the speakers do a remarkable job of reproducing realistically and believably the sounds of both brass instruments and string instruments. With the big woofers playing up to 900 Hz there is plenty of realistic oomph and weight to piano and double bass and drums.

On vocals I do not hear quite the resolution, transparency and in-the-room liveness I hear from electrostatic and ribbon drivers. But I think these PBN speakers reproduce vocals more transparently and realistically than any other compression driver system I have heard, except for audioquattr’s Cessaro Zetas. And to get the transparency and resolution I like on vocals from electrostatic and ribbon speakers, I have to sacrifice some of the weight and body of instruments, and some of the dynamics, I hear from Jeff’s system.

I think Jeff really has achieved something with this system! When he relocates the system to the dedicated outbuilding he is constructing to house the system the sound will take a big leap higher still in sound-staging, overall scale and realism.

Thank you, Jeff, for a wonderful afternoon!
 
Last edited:
May 30, 2010
15,495
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113
Portugal
#2
(...)
About a year ago Jeff acquired from Peter Noerbaek, founder of PBN Audio, a pair of M2!5 loudspeakers. According to the PBN website:

“Two JBL drivers are the heart of the system: First, twin JBL 2235H 15” woofer classics, with a low-loss magnetic structure and Symmetrical Field Geometry, which reduces harmonic distortions to near zero. The second is the inimitable JBL D2430H mid-range/tweeter compression driver, with dual-diaphragms. The drivers are aligned “in time” via their amazing 900 Hz charge-coupled crossovers.”
(...)
It looks like a M2 JBL speaker - can I ask what is meant by "charge coupled crossovers"? And IMHO the Lamm M1.1 is not overkill for a speaker having two JBL 2235H - these speaker units need power. I was told that the Lamm ML3 would be inadequate for them. As far as I could see modern JBL units are not as efficient as some vintage ones.
 
Likes: bonzo75

Folsom

VIP/Donor
Oct 26, 2015
3,793
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Eastern WA
#3
They use a DC bias on the crossover caps for the compression tweeter. It goes cap - DC+ - cap. So the caps have to be double the size for same capacitance.

JBL has been doing it forever. It makes things sound smoother sometimes, by increasing a tiny bit of distortion and maybe reducing some microphonics.
 
Likes: jeffrey_t
Jan 29, 2012
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#5
Ron,
Thank you for the awesome visit and the great write up. These speakers did indeed take about 1 year to break in, but the wait has been worth it. I was very happy with the way the system performed on Peter A's Shefffield drum record, the dynamics produced by the JBL 15's was a lot of fun to listen to. Here's a pic of the system you listened to:

Jeff System 4-10-19.jpg
 

spiritofmusic

Well-Known Member
Jun 13, 2013
9,046
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113
E. England
#7
Great report Ron.
Jeffrey, we've chatted before about yr spkrs. Just a few Qs.

I believe yr spkrs are a custom order ie MTM. Can other customers order exactly what you have? Or is yrs a one-off?

Anything else individual to yr spkrs? One-off crossover, drivers etc?

Is yr sound a "classic" one ie that warm euphonic Altec/old JBL type sound? Or pretty modern ie more transparent and neutral, yet still naturally warm?

Is yr sound voiced twds jazz since that's yr primary love? Or is it pretty even-handed and genre-agnostic?
 
May 30, 2010
15,495
708
113
Portugal
#8
Ron,
Thank you for the awesome visit and the great write up. These speakers did indeed take about 1 year to break in, but the wait has been worth it. I was very happy with the way the system performed on Peter A's Shefffield drum record, the dynamics produced by the JBL 15's was a lot of fun to listen to. Here's a pic of the system you listened to:

View attachment 50315
Great looking system. Can you confirm if the crossovers have batteries? Do you have any impedance measurement of these speakers? Are you using them with the 4 or 8 ohm tap?
 
Jan 29, 2012
1,310
402
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#9
Great report Ron.
Jeffrey, we've chatted before about yr spkrs. Just a few Qs.

I believe yr spkrs are a custom order ie MTM. Can other customers order exactly what you have? Or is yrs a one-off?

Anything else individual to yr spkrs? One-off crossover, drivers etc?

Is yr sound a "classic" one ie that warm euphonic Altec/old JBL type sound? Or pretty modern ie more transparent and neutral, yet still naturally warm?

Is yr sound voiced twds jazz since that's yr primary love? Or is it pretty even-handed and genre-agnostic?
Hi Spirit,
Answers to your questions:

  1. PBN is currently making this MTM version as a standard offering, its called the 2!5s(Symmetrical.) Mine was the first but PBN loved the sound so he started offering it as $5K upgrade vs the standard version.
  2. The speaker has a different shape than the standard version (trapezoid) and the crossover was slightly tweaked. All of this is standard for the 2!5s
  3. The sound is not "classic" or "vintage." It sounds very natural with excellent transparency. As Rob put it, the system has gone from a 'very good sounding stereo to the natural sound we all strive for.' PBN uses JBL's latest technology (compression driver and wave guide), a modern crossover but rebuild vintage drivers as he believe they sound best.
  4. The system presents all types of music equally well IMO. When Peter A visited, we listened to mostly classical. When most of my friends visit, we listen to classic rock. I'm a big progressive rock guy, I love listening to prog rock on this system much more than my past Avantgardes.
 

Folsom

VIP/Donor
Oct 26, 2015
3,793
333
83
Eastern WA
#10
Great looking system. Can you confirm if the crossovers have batteries? Do you have any impedance measurement of these speakers? Are you using them with the 4 or 8 ohm tap?
You don't have to use batteries, you can use any DC source. But there's a trick people don't know about that helps a lot with the DC biasing. I'm guessing a small mod would go a long ways for that (as I've played with it). There isn't any other way to apply a bias to the caps because AC goes through them.
 
Jan 29, 2012
1,310
402
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#11
Great looking system. Can you confirm if the crossovers have batteries? Do you have any impedance measurement of these speakers? Are you using them with the 4 or 8 ohm tap?
Thanks Micro.

The crossovers do have batteries. The impedance is 4 ohms, but I actually use the 2 ohm tap on the Lamm, I think it sounds better. Here's info on the smaller version of the speaker on the PBN website.

https://pbnaudio.com/m25-loudspeaker/
 

the sound of Tao

Well-Known Member
Jul 18, 2014
1,336
792
113
#12
Ron,
Thank you for the awesome visit and the great write up. These speakers did indeed take about 1 year to break in, but the wait has been worth it. I was very happy with the way the system performed on Peter A's Shefffield drum record, the dynamics produced by the JBL 15's was a lot of fun to listen to. Here's a pic of the system you listened to:

View attachment 50315
Very cool. I saw the video that Steve Gutenberg did on them as well. I do love the look of these and a great looking setup Jeffrey.

Do you think it is the caps that take so long to form up that creates a year long burn in time... and also what are the benefits of the charge coupled crossover. Looks like very nice work on the crossover mods as well.
 
Jan 29, 2012
1,310
402
83
#13
Very cool. I saw the video that Steve Gutenberg did on them as well. I do love the look of these and a great looking setup Jeffrey.

Do you think it is the caps that take so long to form up that creates a year long burn in time... and also what are the benefits of the charge coupled crossover. Looks like very nice work on the crossover mods as well.
Honestly I don't understand the super long burn in. I do know that compression drivers take longer to break in as they move very little.The reconditioned 15"s also move very little and are quite stiff.

According to PBN's website the charged crossover helps with the time aligning of the speakers.
 
May 30, 2010
15,495
708
113
Portugal
#14
Thanks Micro.

The crossovers do have batteries. The impedance is 4 ohms, but I actually use the 2 ohm tap on the Lamm, I think it sounds better. Here's info on the smaller version of the speaker on the PBN website.

https://pbnaudio.com/m25-loudspeaker/
Thanks - the link technical information is very complete. Although the speaker is 4 ohm's (minimum 3.5) the impedance phase is very low, a good thing for transformer coupled amplifiers, making it a very reasonable and acceptable load. It is interesting that 30 db per octave acoustical crossover slopes are used.
 

Folsom

VIP/Donor
Oct 26, 2015
3,793
333
83
Eastern WA
#15
Capacitors can take a lot of burn in, too. The biased capacitors sound like what people think time alignment is, but it certainly isn’t actual time alignment.

I agree with Micro, they are interesting speakers!
 
Jan 29, 2012
1,310
402
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#16
Thanks - the link technical information is very complete. Although the speaker is 4 ohm's (minimum 3.5) the impedance phase is very low, a good thing for transformer coupled amplifiers, making it a very reasonable and acceptable load. It is interesting that 30 db per octave acoustical crossover slopes are used.
The compression driver used is from the JBL M2 studio monitor that is meant to be DSP controlled. I know that it took a complicated crossover to get 22KH - 900HZ out of this driver, but it does make the speaker very coherent.
 

spiritofmusic

Well-Known Member
Jun 13, 2013
9,046
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113
E. England
#17
Jeffrey, I recently heard a horns/woofer spkr which crossed also at 950Hz. However, coherent is not the word I'd have used. Additionally, the bass didn't extend much below 35-40Hz, so the whole experience was frustrating to say the least.

Just some thoughts from you, thanks.

12 months of break-in. Is this the spkrs sounding poor for 11 months 3 weeks and 6.99 days, and suddenly the ugly duckling turns into a swan? Or is the spkr pretty good on Day One and gradually ends up as stellar?
And the 4 Ohms rating, would my 70-80W SETs do ok powering these in an extra large room eg 800 sq ft?
 

Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
6,662
1,057
113
Beverly Hills, CA
#18
Marc, if you get more into jazz I think these speakers would be great for you.
 
Jan 29, 2012
1,310
402
83
#19
Jeffrey, I recently heard a horns/woofer spkr which crossed also at 950Hz. However, coherent is not the word I'd have used. Additionally, the bass didn't extend much below 35-40Hz, so the whole experience was frustrating to say the least.

Just some thoughts from you, thanks.

12 months of break-in. Is this the spkrs sounding poor for 11 months 3 weeks and 6.99 days, and suddenly the ugly duckling turns into a swan? Or is the spkr pretty good on Day One and gradually ends up as stellar?
And the 4 Ohms rating, would my 70-80W SETs do ok powering these in an extra large room eg 800 sq ft?
The speakers sounded awesome right out of the box, the best speaker I've ever had. I've owned a lot of speakers including (Avantgarde Uno, Quintessence Stealth, JM Labs, Maggie 3.6, etc). Ron has listened to my system 3 or 4 times and always liked the sound and thought it was a good stereo. Over the last 2 months, and its been 2 months since Ron's heard the system, the speakers have really turned the corner. I would say that its at about 8 months or about 600 hours. They were always good, great dynamics and coherence, but now something is "special."

You 80W SET's would be more that ample. I have 80 watt Lamms and I have them at 25% volume for 90% of my listening. You really can't listen beyond 45% volume. Zero distortion but it's simply too loud.
 

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