Oh no. I did it. JBL 4520 related

[reVintage]

This is Imperial/K130 in 1,0*Pi.
At the bottom 1*2240/Imperial 1,0*Pi.

[Eaulive]

Back in the days,the 4520s were powered by 150wpc Crown D300

You mean like this


This was my first system back in 1987, see the resemblance?
Those were not real 4520s, there were 24" deep and the horn was a lot shorter, loaded with cheap addison 15"
The midbass was an early attempt to a horn and the HF section was a lot of cheap tweeters stuck together.
I had a home made fixed electronic crossover, if I remember well it was 150 and 1500 Hz, the Crown DC 300 for the 4520s, a Sansui 100W for the mid and a homemade 40W amp for the highs.
I thought it sounded good at the time, that's why 20 years later I'm at it again

[Lee in Montreal]

Hi Olive

Start finding sources for some 2SC2608 and 2SA1117 output transistors for my new PC2002 as I suspect some of those are in bad shape or burned. Volume is much lower than my other PC2002, and both chanels aren't equal.

[Eaulive]

Roger that

[Lee in Montreal]

Not 100% sure, but I may have found the reason for the low output. I tried using the jacks and the sound was of the proper level. I then inquired on another forum and was told to check the pin selection switch when using the XLRs, as selecting the wrong set-up will only get you the signal from the crosstalk...

[djmike]

Hi Lee -

Have you built this yet?

Mike

Found some interesting reading.

http://www.ibiza-voice.com/media/new...van/sound.html

"The first part of the new system consisted of 4 "Waldorf" bass speakers. First used in a rental at the Waldorf Astoria, it is similar to the JBL double 15" scoop enclosure but is based on the old Jensen Imperial design. The enclosure was made larger to accommodate a larger rear loaded horn, which was designed with a hyperbolic rather than an exponential flare. The high end consisted of the largest JBL horn lens for smooth wide dispersion and the system is electronically crossed over at 80hrz These replaced the corner home-type speakers."

Leading me to that http://www.decware.com/imperial.htm
"High Fidelity Playback - As shown above with special considerations or with a single 15 inch coax, using the 2nd woofer for 50 Hz and below."

Basically, despite the ressemblance with a 4520, the Waldorf, as designed by Richard Long, is an "adapted" Jensen Imperial. I still wonder how they made the cabinet go down in frequency if the tunnel is that short. BTW GSA's cabinets seem to be the same as RLA's as he was transfered the technology after Ricjard Long passed away. From the pictures I posted a bit earlier, the front view shows a deep recess behind the drivers, and the upper "ducts" as on the Jensen Imperial.


Attachment 50842

[Lee in Montreal]

I am still holding on it. The drafts are done for twin 18" drivers. Progresion curve is nice but I am a bit puzzled by how short the horn is as it is tuned to 40Hz with a mouth that is able to handle much lower. I still have to make a sonic modeling thru winsrep.

Interestingly, it seems there are/were two variations of the Waldorf.

RLA from the Empire roller rink



RLA from Club Zanzibar





If you wish to contribute to this project, then simply help with whatever insight you may have. BTW Drivers would be 2240h (fs30) for effortless oomph under 50Hz.

[djmike]

Looks like they were selling the prototypes and making improvements as they went. There is a guy on this forum that built the Studio 54 models. I asked him for the plans.


Here is the catalog info:



The Waldorf
tri-amplified speaker system featuring a front radiating, rear horn-loaded bass unit with two 15" bass drivers and two 15" mass-loaded passive radiators. The mid-range consists of a JBL horn lens coupled to a 2" compression driver while a gauss tweeter handles the high-end.
The Waldorf is also designed for use with the RLA X-6000 electronic crossover so that linear phasing can be obtained through the use of the special time-delay circuit. The Waldorf is also available in a bi-amp version and can be purchased with various compression driver/bass driver combinations. Designed for vertical or horizontal applications.
DIMENSIONS: 61.5"H x 36"W x 30"D (74" high with horn).
WEIGHT: 385 lbs.

Funny thing about sound installers is that, many times no one has trained ears like they do. They have to make changes to fit a particular venue. I read an article about Zanzibar some time ago that it has some particular challenge due to the size (seems like a low ceiling in one part) and that Richard had to make do. Sounds like they had a few options for the 15". I can't tell from the size of the GSA cabinets if they are 15 or 18, have you asked him?

Mike

I am still holding on it. The drafts are done for twin 18" drivers. Progresion curve is nice but I am a bit puzzled by how short the horn is as it is tuned to 40Hz with a mouth that is able to handle much lower. I still have to make a sonic modeling thru winsrep.

Interestingly, it seems there are/were two variations of the Waldorf.

RLA from the Empire roller rink



RLA from Club Zanzibar





If you wish to contribute to this project, then simply help with whatever insight you may have. BTW Drivers would be 2240h (fs30) for effortless oomph under 50Hz.

[Ruediger]

... featuring a front radiating, rear horn-loaded bass unit with two 15" bass drivers and two 15" mass-loaded passive radiators ...

two 15" mass-loaded passive radiators ?

I do not see where the two passive 15 " drivers could go in this cabinet, and I can not imagine a construction with these components.

And a response flat down to 50 Hz can be achieved with much less effort.

I have heard an RLA system myself, in the Dorian Gray at FFM airport, but something does not fit.

About the time when RLA was in business, a quack here in Germany built similar systems: Hans Deutsch with his infamous "Horn-Resonator".

Ruediger

[Lee in Montreal]

I don't see either what passive rads can do in a compression chamber that needs to be stiff to... compress.

Interestingly, I always wondered why nobody has ever tried placing the woofers not on the top front panel, but on the 45° mid panel as it would greatly help enlarge the horn length by a good 2" feet. As long as the cabinet is used below 80Hz, radiaton of medium frequencies wouldn't be a problem.

[djmike]

You guys have photos of some of the more famous Waldorfs and they are both different. RLA only built five of the 6000 crossovers from the catalog. I doubt that very many Waldorfs were ever built. I think they were designed for the TAD or Gauss 15" woofers and made to go low by being tall and sensitive by being hyperbolic.

Mike

I don't see either what passive rads can do in a compression chamber that needs to be stiff to... compress.

Interestingly, I always wondered why nobody has ever tried placing the woofers not on the top front panel, but on the 45° mid panel as it would greatly help enlarge the horn length by a good 2" feet. As long as the cabinet is used below 80Hz, radiaton of medium frequencies wouldn't be a problem.

[djmike]

Three hundred and 85 pounds!

You guys have photos of some of the more famous Waldorfs and they are both different. RLA only built five of the 6000 crossovers from the catalog. I doubt that very many Waldorfs were ever built. I think they were designed for the TAD or Gauss 15" woofers and made to go low by being tall and sensitive by being hyperbolic.

Mike

[Lee in Montreal]

Here's where I am now. I will probably alter the first 90° bend on the upper right to make it smoother and remove any possibility of reflection. As you can see, the cabinet has 60" internal height and it is difficult to make the horn longer while keeping the simplicity of the path. On the original volume, only the 192L chamber is used, but it can be enlarged to 270L by using both volumes and probably allowing to go deeper.

[louped garouv]

two 15" mass-loaded passive radiators ?

I do not see where the two passive 15 " drivers could go in this cabinet, and I can not imagine a construction with these components.

And a response flat down to 50 Hz can be achieved with much less effort.

I have heard an RLA system myself, in the Dorian Gray at FFM airport, but something does not fit.

About the time when RLA was in business, a quack here in Germany built similar systems: Hans Deutsch with his infamous "Horn-Resonator".

Ruediger

I don't think that the passive radiator version was ever actually offered commercially...
It was in development, but not ever refined enough to be offered to clients...

I believe that I read that on the wave music tech talk forum a few years back...
probably from Scotty, Shorty, or Ed in their more historical framework posting sessions....

Gary Stewart likely may have some knowledge of this prototype design also....

[djmike]

Looks great!

Here's where I am now. I will probably alter the first 90° bend on the upper right to make it smoother and remove any possibility of reflection. As you can see, the cabinet has 60" internal height and it is difficult to make the horn longer while keeping the simplicity of the path. On the original volume, only the 192L chamber is used, but it can be enlarged to 270L by using both volumes and probably allowing to go deeper.