Planar Speaker Asylum

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Planar Speaker Asylum

RE: Replace 3.7i's with 20.7's?

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In Reply to: RE: Replace 3.7i's with 20.7's? posted by Roger Gustavsson on September 26, 2016 at 11:08:05

Hi Roger
Roger is correct. All the .7 maggies have series xovers and can't be BiAmped. That is why I don't replace my 3.6's with 3.7's
Alan

Follow Ups:

RE: Replace 3.7i's with 20.7's? - Davey 13:13:06 09/26/16 (9)
They can easily be bi-amped. It matters not whether the crossover is parallel or series since you'll be bypassing it.

Dave.
- RE: Replace 3.7i's with 20.7's? - ahendler 17:26:47 09/26/16 (1)
  Maybe easy for you but you need to open the back up and rework a new xovr that will give you sound better than the original xovr with one good amp
  Alan
  - RE: Replace 3.7i's with 20.7's? - Davey 18:33:53 09/26/16 (0)
    You said "it can't be bi-amped." That's simply incorrect.
    Any speaker with multi drivers can be multi amped.
    
    Of course you need to open the back up....but only to disable the existing crossover. The rest of the work is done between your preamp and power amplifiers.
    
    Cheers,
    
    Dave.
- RE: Replace 3.7i's with 20.7's? - Satie 13:24:50 09/26/16 (6)
  is there a simple analog circuit to replicate the OEM XO for biamping? Or is it going to have to depart in slope and/or phase unless you use a DSP XO?
  - RE: Replace 3.7i's with 20.7's? - neolith 06:11:34 09/27/16 (4)
    I have tried to create a parallel crossover for the 3.7(i) that simulates the OEM and then convert that to an ALLXO. I came very close but there is a "bump" around the crossover point that arises because the mid-driver is 8 ohms while the bass and treble drivers are ~4 ohms. I suppose this could be flattened with an equalizer or a low Q notch filter but I gave up on the idea for reasons not really related to audio.
    Solid - OEM series XO, Dotted - Equivalent parallel XO
    
    I married the perfect woman. The downside is everything that goes wrong is my fault.
    - RE: Replace 3.7i's with 20.7's? - Satie 07:47:17 09/27/16 (3)
      IIRC you had the sim/calc on your speaker spreadsheet. So you don't have a level adjustment to compensate for different resistance and sensitivity as you would in a line level XO. Would that change your result any?
      I was thinking that you would want to biamp rather than triamp in this case, since it is a low order XO so is rather high hanging fruit to get with replacing the mid/tweeter crossover, not much bang for the buck.
      Can the translation of the XO to parallel be done with a 1st order spaced to get a similar summation to the original rather than the exact same plots? Or do you suspect the midrange energy is going to come out weak that way?
      - RE: Replace 3.7i's with 20.7's? - neolith 08:12:29 09/27/16 (2)
        
        In Reply to: RE: Replace 3.7i's with 20.7's? posted by Satie on September 27, 2016 at 07:47:17
        
        Biamp v triamp: I was planning only to biamp but did the model for triamp just for completeness -- the mid LP and treble HP filters could be ignored for biamping and the speaker level crossover for the high end left intact. Interestingly the translation from the parallel speaker level crossover to the ALLXO requires 2nd order filters not 1st order. There seems to be a problem with my installed version of Librecalc so at this time I cannot pull up the spreadsheet and Bode diagrams. IIRC I could flatten the hump but then there was too much deviation from the OEM which is not what I wanted. I am of the opinion that the active XO should closely emulate the OEM so the voicing is unchanged from the manufacturers goal.
        
        I married the perfect woman. The downside is everything that goes wrong is my fault.
        
        RE: Replace 3.7i's with 20.7's? - Satie 08:56:38 09/27/16 (1)
        
        In Reply to: RE: Replace 3.7i's with 20.7's? posted by neolith on September 27, 2016 at 08:12:29
        
        I am guessing that the parallel setup you were trying is with inverse polarities, while the OEM is (guessing again, did not go and check) with the same polarity. I am guessing that is why the summations are different - i don't find the 90 deg difference in driver phase at the XO to be that bothersome. In my biamping setup with the high freq tweeter high pass it comes off much better than having the classic 1st order XO with inverted phase. Most notably in not having a narrow sweet spot.
        
        RE: Replace 3.7i's with 20.7's? - tedtag 18:24:36 09/27/16 (0)
        
        In Reply to: RE: Replace 3.7i's with 20.7's? posted by Satie on September 27, 2016 at 08:56:38
        
        Thanks so much for everyone's feedback. I very much appreciate the depth of knowledge and experience among this group of inmates! After digesting some of this (I have a very limited understanding of electrical engineering), I'm tempted to try pair of the 20.7's with just the JL7's. These amps are beasts and seem to far outperform their specs. It might just work great without having to biamp, which sort of scares me because I've got no idea at all about how to build or set up an external crossover.
        
        I'm thinking of calling the local Maggie dealer who sold me the 3.7i's and see if they might have a demo pair of 20.7's I could borrow for a couple of days. Trying them may be the only way to know for sure. I might be able to spread the 20.7's another 12" or 18" but if I just couldn't get the speaker locations dialed in or if the 20.7's overpowered the room, I could put back the 3.7i's and rest in peace knowing that they were a better fit for that room. But the odds of finding a demo pair seems pretty slim. I'll let you know what happens. Thanks again!
  - RE: Replace 3.7i's with 20.7's? - Davey 18:40:03 09/26/16 (0)
    I've answered that same question (in various forms) for over fifteen years on this forum. If you haven't grasped the concept and application by now, you never will.
    
    Dave.

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