OTL Asylum

If the load impedance is indeed around 965K, a 0.005uF cap...

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jeffreybehr

A

In Reply to: RE: When you are talking about such small parts posted by Ralph on March 18, 2016 at 09:20:13

...will create a HP-filter of 33Hz. That cap would be a pair of 0.01s in series. The drivers are beginning to roll off acoustically around 200Hz, so 33Hz is about 2-1/2 octaves below their audible-output range.
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Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."

Follow Ups:

RE: If the load impedance is indeed around 965K, a 0.005uF cap... - Lew 19:08:40 03/18/16 (5)
You might try a Russian SSG. I think you can buy them in that value. That is the most transparent capacitor I have heard, with the possible exception of the 100X more expensive Vcap CuTf.
- The more I (over)think* this, the more I'm tending toward... - jeffreybehr 21:08:47 03/18/16 (4)
  ...a 0.01uF SoniCap Platinum. FP will be about 16Hz, which is plenty low enough to avoid phase errors in the audible band--of these MR drivers, that is--and high enough to block or greatly reduce DC or large noise pulses which might destroy those irreplaceable drivers.
  * I tend to do this a lot, but my system has never sounded better, so some good must come of it. ... :-)
  
  ----------
  Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
  William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
  
  Edits: 03/25/16
  - If you are dealing with fragile drivers - Ralph 10:26:47 03/21/16 (3)
    I would consider several points:
    
    The amps can make a lot more power than the drivers can handle! Its only prudent to install a tweeter protection fuse of some kind! One mistake could cost you a fuse or a driver: your choice.
    
    You might also consider putting a coupling cap at the output of the amp. It does not have to be very big and could save you some headaches- after all- the output section of the amp is direct-coupled.
    - RE: If you are dealing with fragile drivers - jeffreybehr 15:16:12 03/21/16 (2)
      Well, they're not fragile; being B-G mag-planar drivers, they simply can't be replaced, new at least, as B-G's new foreign owners decided to stop making them.
      Of course the tweeter has its high-pass filter in the x-over, but the MR doesn't. I remember asking GR Research's Danny Ritchey, the designer of the speakers, what filter point I should use on a high-pass filter with the 8- and 50-Watt amps I had at the time. We went back and forth, with him answering every number I offered to him (as in 200Hz? 100Hz? 50Hz? 25Hz? None at all?) with an 'OK'. He then said something like my low-power amps were not able to overdrive the panels, so it didn't much matter.
      So with each 10" MR driver rated at least 75 Watts power handling by the most-conservative method...
      http://gr-research.com/pdf/Neo10.pdf
      ...the four of them will handle at least 300 Watts, so I'll NOT be adding a new series cap between the amp and the x-over.
      TYVM for your help.
      ----------
      Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
      William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
      
      Edits: 03/21/16 03/21/16 03/22/16
      - I agree- sounds like you are in good shape nt - Ralph 08:34:26 03/22/16 (1)
        
        In Reply to: RE: If you are dealing with fragile drivers posted by jeffreybehr on March 21, 2016 at 15:16:12
        
        -
        
        I've subsequently decided, after a discussion that you and I had here... - jeffreybehr 23:42:04 03/25/16 (0)
        
        In Reply to: RE: I agree- sounds like you are in good shape nt posted by Ralph on March 22, 2016 at 08:34:26
        
        ...a few years ago to change the 1M-Ohm load resistors to 390Ks and use a 0.01uF SoniCap Platinum, for a high-pass-filter point of 41Hz.
        
        Finished!
        ----------
        Tin-eared audiofool, large-scale-Classical music lover, and damned-amateur fotografer.
        William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."

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