JBL L-212 reviewed by High Fidelity Magazine June 1978

[oldsoundz]

[pos]

Interesting, thanks!
That review and the 200Hz "mound" was mentioned by David Smith here:
http://www.audioheritage.org/html/pe...ives/smith.htm

the 212 had a removable base that, once removed, allowed the system to be buried flush in the pit. The crossover was designed to give a highly flat system under those conditions. Unfortunately once removed from the pit the 2pi to 4pi effect was enough to mess up the response to an appreciable degree. Not that it was horrible sounding, just that it wasn't the balance you would have given it if you thought about it. I remember that the system was reviewed by High Fidelity. They used CBS labs for measurements and did a Floyd Toole type axial response/front hemisphere/total sphere set of measurements. Sure enough the response showed a pretty good mound around 200Hz (the secondary effect) that the reviewers commented on. I don't remember if a running change was made to fix it, but at least a lesson was learned that 2pi flat was not the answer and no later systems fell into that trap. This was one of the main incentives for developing the ground plane measuring technique.

By the way I had one of the 212 systems and liked it a lot. It used great drivers including the very expensive 112A mid bass unit. This was the only 8" JBL driver to use a 3" coil. Terry showed me a 3 element passive notch circuit that was developed to fix the response and so it sounded quite good. When I moved to KEF in the UK, this is the system I took with me (I sold my KLH 9's to Randy Patton).

[oldsoundz]

Interesting, thanks!
That review and the 200Hz "mound" was mentioned by David Smith here:
http://www.audioheritage.org/html/pe...ives/smith.htm

It was my pleasure. These things are for sharing. Jeez I feel like I have finally contributed.

[jblsound]

A very good system made better with mirror imaged boxes, Ti tweeter, the 2105 pro midrange, Charged-Coupled XO.
I listen to those everyday.