[cjfrbw]

I bought a pair of Lambda original low bias with a SRD 7 sd energizer. They look almost new, excellent condition and appearance, and work very well with a couple of tubed and SS amps through the energizer. I can't fault the sound, it seems very balanced and not the least bit thin, with full bass and an articulate mid range. My question, the drivers appear to be gold in color under the metal grid. I thought that those were the later pro bias drivers, not the original Lambda low bias drivers. Is it possible the drivers were changed? Also, since it sounds very nice, if it turned out to have pro bias drivers that were placed in the housing, would they operate at all with a normal bias energizer such as the SRD 7 sd, which is normal bias? The cord has six pins, in accordance with the normal bias headphone. If they are pro bias, does it damage them to run them with normal bias as long as they work?

 

[cjfrbw]

bump

 

[cjfrbw]

Wow, this is a fast scrolling site.  No answers, bump.

 

[TIMITS]

Hi cjfrbw,
 
You might have more luck posting this in this in the High End Audio forum where most of the Stax folks hang out: http://www.head-fi.org/forum/thread/223263/the-stax-thread-new

 

[deadlylover]

If the drivers are in fact pro drivers, they will still operate fine on normal bias, any damage is unlikely.
The sound may be a little 'soft' though, but that's about it.

 

[spritzer]

I very much doubt that somebody installed Pro drivers and didn't swap out the cable.  That's not something Stax would ever do but plenty of 3rd party mods out there.  Running a Pro transducer off the normal bias output will not do any damage, it just lowers the voltage potential of the drivers which means the stators don't "grip" the diaphragm as well and the sound is soft. 

 

[cjfrbw]

Thank you, all.  I finally managed to do some research in the morass of threads and pro drivers will "work" with normal bias but not vice versa. The lower bias will not be optimal with a pro driver, a "normal" driver will be burned out by pro bias.
 
  I guess my only other question is if the gold looking stators are actually low bias lambda or newer "Frankenphone" pro bias. Pictures on Wiki show the original lambda stators as being whitish, not copper gold.
 
Maybe I just don't care, the phones don't sound soft with my amps, as a matter of fact the bass is rich, tight and strong and the tonal and detail definition is exemplary. The preamp knob can't go past 9AM with a 50 watt amp.
 
I guess if I like it and it suits my tastes, it is OK the way it is.  I will just try to find out later if the stators have been changed.

 

[spritzer]

All Lambdas until 1994 used the same brass stators so they could be any of the first 3 generation drives.  
 

 

[cjfrbw]

Thanks,
I think it must be the correct low bias driver because it sounds so good.  I would imagine the pro bias would sound problematic somehow..

 

[spritzer]

Pro bias drivers off a normal bias supply work just fine.  The other way around is not that great...