D50SMS8 3way monitor with LE15A 375 075 original product?

[old-fashioned]

Hi,

I´ve just picked up a pair of vintage JBL 3way monitors today and come back to the forum after a very long pause. I hope you all are doing fine!
I´m a JBL fan since age of 10 or 11. At my beginnings Project K2 was advertised in several German HiFi magazines and it became my dream loudspeaker.
A friend of mine had it on sale, but I didn´t want to afford it and instead bought an used Gen 5 Bullitt Mustang...
Due to location and family issues I can´t work for Harman Pro. I´m also happy at my current studio monitor brand employer,
So I´m collecting and freaking around with all kinds of JBL stuff, at least.

I´m wondering if I bought a pair of D50SMS8 or DIY modified 4320 today.
It´s equipped with reconed LE15A, 375 and 075. The cabinet looks like 4502 with the energizer cutout at the back of the cabinet,
Do you know how old they are and if they are any good?
Is the 2405 the better super tweeter for it?


Cheers,

Andreas

[Robh3606]

Yes if you look back through the catalogs the TOTL cabinets typically had a choice of either an S7 or S8 load. Looking at the 1962 catalog here is an example with the S7 load with options for the S8. Take a look at the Soveriegn in the 1967 catalog where it details components for the S7 and S8

No idea how old they are but I would guess 60's early maybe into the early 70's not know how long that cabinet and load were offered as a system.

http://www.lansingheritage.org/image.../page24-25.jpg


http://www.lansingheritage.org/image...ome/page09.jpg

Rob

[old-fashioned]

Hi Rob,

thank you.
Is the D50SM the first JBL studio monitor?
It seems that the 4320 came later.

Cheers,

Andreas

[old-fashioned]

� Harman International, Courtesy Mark Gander and John Eargle

"JBL would get its foot in the door of the broadcast and studio segment of the professional market in the 1960's as well. As in the cinema market, they would be up against their greatest rival, Altec Lansing. Altec had a lock on the studio monitor business with their 604 Duplex and A7. Were it not for a misstep of Altec in 1962, JBL may never have gotten the opportunity to enter and eventually dominate this market. That misstep was Altec's introduction of the 605A Duplex. The 605 was introduced as the next generation Duplex and replaced the previous 604D. However, it's primary development objective was cost reduction as opposed to improved sonic performance. The magnetic motors of this driver were significantly reduced in size compared to the preceding 604D. It resulted in a 3db drop in sensitivity in addition to subtle changes in sonic character. Industry response was entirely negative. Sales of the 605A dropped significantly in comparison to the 604D. It resulted in such a backlash, that for the first time, major record companies began considering alternatives.

At the time, JBL had developed the D50SMS7 as their first dedicated studio monitor. It consisted of the S7 home component kit installed in an industrial cabinet. JBL was having a very difficult time breaking into the market with this system until the Altec 605A introduction. All at once, they found a receptive industry. In particular, Capitol Records had a relationship with JBL through Bill Thomas. Capitol had a facility in the vicinity of JBL's Casitas headquarters and Bill had become acquainted with their management. Bill convinced Capitol to try the D50 monitor once the 605A backlash had become evident. Capitol was very pleased with this system. They were impressed enough that they eventually standardized all of their studios on JBL monitors.

Eventually, Altec had to admit their error and reintroduce the 604 as the 604E Super Duplex. However, by then, the genie was out of the bottle. The close of the decade saw the development of two significant JBL monitors that expanded their customer base beyond Capitol Records. The first was the 4320, which was a refinement of the D50. It used a higher cross-over frequency for increased power handling and better integration between the horn and 15" bass driver. The result was a studio monitor that had flat axial response and flat power response - something that the 604/5 could not match. It resulted in widespread industry acceptance.

The second significant JBL monitor from the late 60's would become an industry legend. That was the 4310 bookshelf monitor"


It seems to be their first 3way studio/broadcast monitor.

[Mr. Widget]

Eventually, Altec had to admit their error and reintroduce the 604 as the 604E Super Duplex. However, by then, the genie was out of the bottle. The close of the decade saw the development of two significant JBL monitors that expanded their customer base beyond Capitol Records. The first was the 4320, which was a refinement of the D50. It used a higher cross-over frequency for increased power handling and better integration between the horn and 15" bass driver. The result was a studio monitor that had flat axial response and flat power response - something that the 604/5 could not match. It resulted in widespread industry acceptance.

If you swap out the 075 for the 077 or 2405, improve the crossover to either a modified 3133 or Nelson Pass version, or go active you will have a much better speaker. Since you have the LE15A, you can't clone the L300/4333A but I suggest you head in the direction of the L300/4333A with what you have.

The original crossovers are terrible and the crossover frequency is too low. This is true of most vintage JBLs. Over time JBL refined their network designs and learned how to better integrate their large 15" woofers to their truly excellent compression drivers and horns. Even though the 375 can operate down to 500Hz, the horn required to do this well would be massive so give 800Hz a try.

You can keep the vintage look and significantly improve the sound by making a series of small tweaks. The 075s will work, but they don't have the UHF extension and are quite beamy.


Widget

[jbl4ever]

If you are staying passive the crossovers for that driver configuration at 800 hz would be early version 3110 pro or LX13 consumer

[old-fashioned]

Hi,

thanks for the comprehensive feedback.
They are heritage collectables and potentially the first official passive JBL 3way studio monitors ever. I'll restore and keep them. They are from a famous Berlin based recording studio.

Changing the supertweeter and x-over temporarily is no problem.
Frankly speaking, the Nelson pass XO still has got too much SPL curve ripple for my taste. It's inherent for the early horn designs in my opinion. I will check the alternative XO schematics. They seem to be quite straight forward.
For serious listening I'll use my modified 4430 clones and other speakers with JBL components like the more modern 2452H-SL with PTH1010HF or the 2451-SL with small Stereolab of Jabo Horns. I am currently checking the performance of the Radian aluminum diaphragms. (I'm not completely convinced with the Be diaphragms, cause I saw several measurements with higher THD at the lower cust-off compared to original JBL ribbed TI diaphragms. It should be the surround.)
Everything step by step...

Cheers,

Andreas

[Mr. Widget]

They are heritage collectables and potentially the first official passive JBL 3way studio monitors ever. I'll restore and keep them. They are from a famous Berlin based recording studio.

I can appreciate that. I love lots of vintage gear that may not be up to my standards today or satisfy my taste these days, but it is fun to take a trip into the past from time to time.


Widget

[old-fashioned]

I had to sell my chromebumper C3 convertible a few years ago.
I still miss the gasoline fumes, sound, vibration and vibe.
It's about charm and the respect what the engineers could do at their decade.
I hope the sound of the monitors is not too unbalanced... ;-)

[Ian Mackenzie]

Hi,

thanks for the comprehensive feedback.
They are heritage collectables and potentially the first official passive JBL 3way studio monitors ever. I'll restore and keep them. They are from a famous Berlin based recording studio.

Changing the supertweeter and x-over temporarily is no problem.
Frankly speaking, the Nelson pass XO still has got too much SPL curve ripple for my taste. It's inherent for the early horn designs in my opinion. I will check the alternative XO schematics. They seem to be quite straight forward.
For serious listening I'll use my modified 4430 clones and other speakers with JBL components like the more modern 2452H-SL with PTH1010HF or the 2451-SL with small Stereolab of Jabo Horns. I am currently checking the performance of the Radian aluminum diaphragms. (I'm not completely convinced with the Be diaphragms, cause I saw several measurements with higher THD at the lower cust-off compared to original JBL ribbed TI diaphragms. It should be the surround.)
Everything step by step...

Cheers,

Andreas

Hi Andreas,

Seems you have an eye for technical details which can be helpful.

It’s really how the sum of the parts combine together in your particular room. Tests on Voice Coil are useful and there are comparisons of aluminium and Be in that journal.

Typically Be drivers come into their own above the AL mass break up point.

Sometimes the dynamic behaviour of the loudspeaker is what draws the distinction from bench tests to real auditions. The technically perfect loudspeaker can still sound like a tiny bookshelf loudspeaker because to obtain that un smoothed “smooth response” required far less sensitive direct radiator drivers like Peerless and Scan. Typically most published test measurements are magazine curves because they are smoothed.

I can smooth the 4333A response and you would not be a sceptic! Nor would you be the wiser.

If you go to the well regarded Troels diy project loudspeaker website he has 1/2 octave smoothed measurements of some medium sensitivity large systems.

http://www.troelsgravesen.dk/The-Loudspeaker.htm

http://www.troelsgravesen.dk/The-Loudspeaker-III.htm

Troels recently declared his version of the jbl 4343 the best loudspeaker he has designed to date!
It’s a four way system based on the concepts of the 40+ year old JBL system.

Why is this so? Read his design article. His chosen drivers were not exotic by my
any means.

If you have a look at Joseph Crowes horn diy website he posts real measurements of his NextGen TAD style radial horns using a variety of compression drivers. I personally think a 90x40 or 90 x 60 horn is the preferred diy horn because your not inviting a multitude of reflections off your floor and ceiling.

With horns the devil is always in the details.

[BMWCCA]

I had to sell my chromebumper C3 convertible a few years ago.
I still miss the gasoline fumes, sound, vibration and vibe.
It's about charm and the respect what the engineers could do at their decade.
I hope the sound of the monitors is not too unbalanced... ;-)

Never sell anything!

[old-fashioned]

Hi,

I have invested into a modern Gen 6 Mustang...
No carb hassle anymore. I save the classic topic for later.

Regarding both mentioned websites, l watch them from time to time. I got a few of their preferred drivers in my collection or already tried them. 18sound spec sheets and especially their SPL curve graphs are a little bit dangerous.
Based on my personal experience less ways are better for dispersion control and flat acoustical power curve. So maximum a 3 way with low midrange x-over.
Anyway, dynamics and transients are vital for high fidelity music reproduction. You don't want to go back anymore.

Is there any JBL white paper / study about authentic dynamics reproduction, how to improve it and why it is beneficial for the listener's perception?


Cheers,

Andreas