Notes from the past... 600 Acoustic Watts!
Gentlemen:
This could be a photo of one of a number of installations dating from the heyday of California Aerospace in the sixties and seventies. Fancher Murray may be able to shed some light on this, inasmuch as he described something similar to me that had been built in El Segundo, CA, for Wyle Laboratories when he was working there.
It looks like about 80 375s and 40 LFs. Assuming an input signal of, way, 25 average watts per HF driver with an average efficiency of 30 percent, we would have 25 x 0.30 x 80, or about 600 acoustic watts. The actual level would depend on the size and treatment of the receiving space. (Do you all recall that the acoustical impedance of a highly reverberant space is quite different from that of a free field?)
John Eargle
On Aug 9, 2005, at 3:23 PM, Don McRitchie wrote:
I can add that I know there was such a testing setup at the White Sands Missile Range in New Mexico that was recently decommissioned. Around four years ago, the drivers from that setup began showing up on Ebay. The HF drivers were labeled 375H and “Manufactured by JBL for Transducers Inc.” The LF drivers were labeled 150H with the same Transducers Inc. brand. Transducers Inc. was a private company that was wholly owned by Bill Thomas (the then owner of JBL) as separate company that built sonic and vibration simulation equipment for the military. Someone from JBL of that era (it may have been Harvey Gerst) recently told me that the 150H was nothing more than a 130A chassis with an LE15A cone kit (for the reason’s Mark cited). The drivers were all painted the same blue colour as the original LE series drivers which would date them from the early 60’s. It was comical to see them advertised on Ebay as rare hi-fi drivers. Some auctions even alluded to the 150H as being the driver from the Hartsfield, confusing it with the 150-4C. I’m not sure if there were any physical differences in the 375H compared to the standard 375. The diaphragm was still aluminum and not the later high power phrenolic version. However, I can’t imagine an LE15A cone kit in a 130A chassis having a “hi-fi” response. BTW Mark, if you ever come across photos like this in the archive again, let me know. I don’t remember seeing anything like this when we rummaged through it.
Don
From: Gander, Mark
Sent: Tuesday, August 09, 2005 3:06 PM
Subject: RE: Any idea what this is?
This was an acoustic and vibration testing set-up at one of the aerospace testing companies in the 1960s. I remember this and other similar photos from the JBL archives. JBL 375 compression drivers on the rectangular mouth horn that was used with the HL89 serpentine lens, and probably 130A woofers, judging by the pot and frame (same as a D130, but the light cone and coil of a D130 couldn’t take this level of abuse), though the driver may have been a special hybrid – notice the white Lansaloy(Rubatex) surrounds. All to generate 150+ dB sound fields to simulate rocket launch levels of sound and vibration.
... Mark Gander as you may know is the VP of Marketing at JBL.
Eventhough Klipsch is not having a Pilgrimage this year it won't stop the Pilgrims from having fun!
I helped Michael Colter this weekend put together his Klipsch PA for the "Battle of the Bands". You can see some of the other photo's at this link:
http://forums.klipsch.com/forums/p/116595/1210452.aspx#1210452
Here is the critical info:
Who? YOU, and anyone else with a passion for things Klipsch audio wise. So drive, fly, whatever, just get to Indy.
What? A get together we will call for now "IndyFest 2009" celebration!
Where? Indianapolis, Indiana................... (Broadripple Park on Saturday)
When? June 12-14 2009
Why? (Michael aka Colterphoto1 and Roger aka IndyKlipschFan) think a annual get together is a great idea. Especially in bad times. It allows us to share ideas, set ups, and learn from each other. We will demo "All things Heritage" from the smallest to the biggest, and a LOT of the Pro Gear including a full MCM system and the mighty Jubilees too. All in one weekend.. You can get your ears full of that classic Klipsch sound, learn about drivers and x overs and how to keep your Klipsch speakers running for life!