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Re: Sledgehammer

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marin

(A)

In Reply to: Re: Sledgehammer posted by Davey on August 25, 2004 at 14:19:48:

davey,
if you read my post carefully, you'd realize that i'm not making up numbers here!
i said that a tympani4a iron core coil has 1ohm, and the coil i ended up using has 0.1ohm.
and if you can't hear this kind of change in a crossover then a bose wave radio will suffice... ;)
best regards,
marin

Follow Ups:

Re: Sledgehammer - Davey 06:22:08 08/26/04 (7)
I did read your post carefully.
I know you didn't make up the number for an iron core coil, but a 2.5mh coil with 0.1 DCR would have to be about 8awg and probably cost well over $100.00 each...and be physically huge. I would think that price/size would be completely unrealistic for a listener who has MMG's. Just my two cents.
And the Bose Wave radio insult wasn't necessary.
Cheers,
Davey.
- Re: Sledgehammer - marin 07:42:16 08/26/04 (6)
  davey,
  i'm sorry to have insulted you with the bose. actually, trying to prevent that from happening i had inserted the smiley...
  i wound and epoxied the coil by myself for about 10$, and it was for a tympani4a, where size is relative. it is about 6" in diameter and 4" high; can't recall it's weight.
  regards, marin
  - Re: Sledgehammer - Davey 14:47:53 08/26/04 (5)
    A man who winds his own coils....excellent! That's the DIY spirit I like.
    I ran my own simulation with a 1.0 ohm DCR coil vice a 0.1 ohm DCR 2.2mH coil in a first-order crossover identical to the MMG. I'm not sure why you selected a second-order filter with a largish value capacitor for your simulation since I thought we were talking about a stock MMG crossover here......
    Anyway, the results are as expected. An approximate 2db passband increase, but very minimal effect on the crossover frequency and the associated electrical summation with the high-pass network.
    I'm not sure what "bump" you're referring to in your previous post, but I'd be interested in seeing your simulation. I'll post mine on my website as soon as I get home from work.
    Cheers,
    Davey.
    - Re: Sledgehammer - marin 23:28:09 08/26/04 (2)
      forgot to ask for your web address...
      regards, marin
      - Re: Sledgehammer - Davey 06:58:52 08/27/04 (1)
        
        In Reply to: Re: Sledgehammer posted by marin on August 26, 2004 at 23:28:09:
        
        Here's what I got when I simulated the electrical response of the MMG crossover:
        http://home.comcast.net/~dreite/Temp/DCRcomparison.JPG
        If you actually made a transfer function measurement with a spectrum analyzer right at the transducer terminals that is what you'd see.
        The two overall curves are simply a vector sum of the high/low-pass filters. I inverted the high-pass curve 180 degrees since this is how the MMG's are wired.
        The low-pass only curves show the effect of the DCR change. What happens is that as you move up in frequency the inductive reactance of the coil starts to dominate any DCR differences so the curves "come together." By the time the crossover area is reached they're essentially the same. This is why there's minimal effect on the system crossover frequency and the most audible change is primarily a result of the increased passband level of the low-pass filter.
        Hope that explains everything.
        Cheers,
        Davey.
        
        MMG electrical response (Open in New Window)
        
        Re: Sledgehammer - Davey 07:08:04 08/27/04 (0)
        
        In Reply to: Re: Sledgehammer posted by Davey on August 27, 2004 at 06:58:52:
        
        Forgot to add that the plot shows only the electrical crossover point which is near 1khz. This should be a very familiar "look" to Magnepan folks who frequent this forum. The large depression in the electrical response is typical of many of the Maggie models....and a very clever "fix" was suggested by Ed G. relating to the 1.6's.
        The actual acoustic crossover point, and the system response through that area, will be somewhat different once the driver responses are factored in.
        Davey.
    - Re: Sledgehammer - marin 23:26:00 08/26/04 (1)
      davey,
      i've been referring to a tympani4a all along, since that was the model i modified, and have measurements for. one of the trials included the second order low pass filter i was referring to...
      i'll try to screenshot the simulation and upload it to my website anytime soon.
      regards, marin
      - Sledgehammer - pt. deux - jharris 11:11:30 08/27/04 (0)
        
        In Reply to: Re: Sledgehammer posted by marin on August 26, 2004 at 23:26:00:
        
        So let me see if I can sum up this thread. If I move to the Sledgehammer coil, what I'll end up with is a litle more of the frequency range being moved into the tweeter. Now, is that because of the gauge being 15 instead of 14 or because the 2.0mh factor is < than stock 2.2 or the 2.25mh is > than stock 2.2???

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