Planar Speaker Asylum

Welcome! Need support, you got it. Or share your ideas and experiences.

Planar Speaker Asylum

Impedance Curve For 3.7i?

142.136.193.97

Does anybody have the new curves for the 3.7i? My tube amps didn't like the high impedance spike on the MMGs. The curve on older 3.7s looked a lot better than the MMGs, so it looked like I would be good but I don't have any info on the new crossover.
I had talked to Wendel about my issue but he blew me off and said the frequency response was flat on the MMGs. Well it was with my SS amps, but not even close with my tube amps. I'm going to order a new pair of 3.7s but I sure would like to look at the curve.

Follow Ups:

RE: Impedance Curve For 3.7i? - neolith 15:47:43 08/05/14 (13)
I suspect the impedance curve is flat since the x.7 models reportedly have a series crossover. With series crossovers, the impedance of the drivers are interrelated so rises in the one driver are countered by a drop in the other.
Note: The constancy of the impedance is true only for 1st order series crossovers, but that is what the x.7's are using.
�

�
- RE: Impedance Curve For 3.7i? - Roger Gustavsson 23:25:58 08/05/14 (4)
  A series crossover does not automaticly generate a flat impedance curve.
  http://sound.westhost.com/parallel-series.htm
  
  The 1.7 is said to have a series crossover and its impedance curve is dropping below 2 ohm at higher frequencies.
  http://tinyurl.com/phlgp9p
  - RE: Impedance Curve For 3.7i? - Utley1 17:50:45 08/09/14 (2)
    Roger: I wonder about that. I have the 1.7's .I am using Emotiva mono blocks XPA1: Although have potentially 1000 watts they are not noted for functioning at an impedance in the 2 ohm range; they will not work well with some dynamic speakers with varying loads or even Martin Logan's , the technician told me....I play a lot of organ music and choral music..no problems at all with substantial volume...If there is any distortion it is in the upper middle, not in the tweeter. And also the amps can get hot-so you may be right. But some one will have to open the speaker to if the crossovers are in series.
    - RE: Impedance Curve For 3.7i? - Roger Gustavsson 04:07:16 08/11/14 (1)
      Well, 2 ohm at high frequencies do not use to be a problem. The level at these frequencies use to be rather low. If not, you will not like to stay in the room...
      
      What happens when you insert attenuating resistors in a series crossover?
      http://sound.westhost.com/par-ser-f11.png
      Will a attenuating in the tweeter section not upset the rest of the speaker?
      - RE: Impedance Curve For 3.7i? - Utley1 04:47:06 08/11/14 (0)
        
        In Reply to: RE: Impedance Curve For 3.7i? posted by Roger Gustavsson on August 11, 2014 at 04:07:16
        
        I do use an attenuator? Am trying to follow you? But thanks.
  - RE: Impedance Curve For 3.7i? - Davey 08:20:05 08/06/14 (0)
    I believe the reason for that is because the 1.7 "tweeter" doesn't have any low-pass filter employed. The "super-tweeter" transducer is essentially in parallel with the tweeter at high frequencies and thus reduces the impedance.
    
    Since the 3.7i uses the true ribbon tweeter and a "conventional" midrange we could probably assume there is a low-pass filter employed on the midrange and the impedance level at high frequencies does not drop below 3 ohms.
    
    Dave.
- RE: Impedance Curve For 3.7i? - Davey 18:43:12 08/05/14 (6)
  It still depends upon the alignment though....even if first-order. Unless it's "textbook" there will still be peaks/dips in the impedance curve.
  However, if a flat impedance curve is mandatory without altering the crossover alignment, a conjugate network can be added across the input terminals to make it purely resistive.
  Edit: FYI....In fact, I look back in my notebook and it's a 10 ohm, 47uF, and 0.6mH....all in series, placed across the input terminals. That will level the MMG impedance to flat across the entire audio band.
  Cheers,
  Dave.
  
  Edits: 08/05/14
  - RE: Impedance Curve For 3.7i? - neolith 20:10:18 08/06/14 (5)
    Thanks for pointing out that the impedance curve is flat only for kosher (symmetric) first order alignments. But this is true for parallel xo's as well - got to love those 1st order filters. In any case the deviation of the impedance from flat is small and tends to drop rather than spike like the MMG, so I think the OP is safe with the 3.7i's.
    �
    
    �
    - RE: Impedance Curve For 3.7i? - Davey 04:04:56 08/07/14 (4)
      Yes, the impedance swinging for parallel crossover can be flat too.
      
      The test referenced was for a 1.7 speaker. I'm not aware of an impedance sweep test for a 3.7i..or even a 3.7. Have you seen one?
      
      Dave.
      - RE: Impedance Curve For 3.7i? - Roger Gustavsson 04:39:21 08/07/14 (3)
        
        In Reply to: RE: Impedance Curve For 3.7i? posted by Davey on August 07, 2014 at 04:04:56
        
        We have not seen the schematic of the crossover of the 3.7 either. How does it work with the damping resistors?
        
        RE: Impedance Curve For 3.7i? - Davey 14:03:45 08/07/14 (2)
        
        In Reply to: RE: Impedance Curve For 3.7i? posted by Roger Gustavsson on August 07, 2014 at 04:39:21
        
        Damping resistors? Do you mean an LCR conjugate network?
        
        Dave.
        
        RE: Impedance Curve For 3.7i? - Roger Gustavsson 23:29:06 08/07/14 (1)
        
        In Reply to: RE: Impedance Curve For 3.7i? posted by Davey on August 07, 2014 at 14:03:45
        
        I mean the level setting resistors for mid and tweeter at the back, http://media.tas.zeitpress.com/articles/images/P4012866.JPG
        
        RE: Impedance Curve For 3.7i? - Davey 10:15:28 08/08/14 (0)
        
        In Reply to: RE: Impedance Curve For 3.7i? posted by Roger Gustavsson on August 07, 2014 at 23:29:06
        
        Ah. Those are in series with the transducer(s) and would only serve to raise the system impedance....and attenuate.
        
        "Damping" resistors would be in parallel, not series and would reduce the impedance load. You don't normally see resistors in parallel (by themselves) in passive networks.
        
        Dave.
- RE: Impedance Curve For 3.7i? - russ69 16:53:22 08/05/14 (0)
  Thanks neolith, that was very helpful.
RE: Impedance Curve For 3.7i? - Roger Gustavsson 11:53:32 08/05/14 (5)
What high impedance spike?
- RE: Impedance Curve For 3.7i? - russ69 12:24:07 08/05/14 (4)
  Your chart is not labeled but that looks like the MMG curve? The 1K Hz@23 Ohm rise did not make my Cary Six-pacs happy. It was discovered during listening tests and in searching for the cause, the impedance curve looked like it might be the problem. Swapping out the tube amp with a solid state device completely cured the issue.
  No measurements were taken to confirm my listening experience but it didn't really mater, the issue (problem with one frequency) was identified and resolved. The 3.7 curves look favorable but I have not seen data for the new series crossover and I wanted to try the Six-pacs again.
  Worse case, I'll dump the Carys and put my 400WPC Mac with output transformers on the job. Did you have something to add?
  
  Edits: 08/05/14
  - RE: Impedance Curve For 3.7i? - Davey 13:51:44 08/05/14 (2)
    I don't know what you mean by your amps "not being happy." If you're expecting no skewing of the response in relation to the impedance curve then you've selected the wrong amps. :) That kind of response irregularity is unavoidable/inherent when using amplifiers with high output impedance.
    
    Most likely the 3.7i's will not have a flat impedance curve either. The only way to know is to test/plot it. It's a fairly simple procedure if you have the proper test equipment.
    
    Cheers,
    
    Dave.
    - RE: Impedance Curve For 3.7i? - russ69 14:45:02 08/05/14 (1)
      "I don't know what you mean by your amps "not being happy."
      
      Here's the thread: http://db.audioasylum.com/mhtml/m.html?forum=mug&n=170969&highlight=mmg+russ69&r=&search_url=%2Fcgi%2Fsearch.mpl%3Fforum%3DALL%26searchtext%3Djbls%2Findex.php%2Fadmin%2Fcategories.php%2Flogin.php
      - RE: Impedance Curve For 3.7i? - Davey 18:51:13 08/05/14 (0)
        
        In Reply to: RE: Impedance Curve For 3.7i? posted by russ69 on August 05, 2014 at 14:45:02
        
        Ah yes, I think I remember that thread now. :)
        
        My comment/suggestion to Neo also works for the stock MMG crossover too. The impedance peak can easily be leveled with a conjugate network if this is an issue with a particular power amp.
        
        Dave.
  - RE: Impedance Curve For 3.7i? - Roger Gustavsson 13:45:30 08/05/14 (0)
    Tube amps use to like high impedancies. 23 ohm is not very high, most conventional speakerscuse to have peaks higher than that. Some electrostatic can have very strange impedance curves. Still not very difficult for the right power amp.

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable