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Sledgehammer

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I wanted to use the Sledgehammer steel laminate inductor in my MMGs, but the nearest size is 15g/2.0 mh or 15g/2.25 instead of 14g/2.2 mh. Is either of these acceptable? If not what would be a suitable upgrade choice?
Thanks

Follow Ups:

Re: Sledgehammer - bigsid 13:07:06 08/24/04 (14)
I used the 14ga alpha-core copper foil inductor and am very pleased.It has the same value(2.2) but much lower resistance. Its available direct from Alph-Core.
- Re: Sledgehammer - marin 23:25:56 08/24/04 (13)
  "...has the same value but much lower resistance..."
  which translates into a shifted x-over behaviour in comparison to the original...
  just my 2cts.
  regards, marin
  - Re: Sledgehammer - Davey 06:37:41 08/25/04 (12)
    Not enough to worry about. A more likely audible change would be an increase in level relative to the tweeter.
    Davey.
    - Re: Sledgehammer - marin 12:38:49 08/25/04 (10)
      just did a quick simulation on a 12db low pass filter containing a 2.5mh coil with a series resistance of 0.1ohm and a parallel capacitor of 56uf for a 5 ohm magnetostatic panel.
      yes, if only the inductor's serial resistance changes, then only the output level in the band pass changes...but that affects the crossover point and the summation curve.
      in my example i changed the serial resistance to 1 ohm (measure a genuine iron core coil of a t4a e.g.) which tranlated into the crossover point sliding up from 300 to 350 hz, 2db more bass in the band pass and a 2.5db bump at 330hz.
      not enough to worry about???
      i don't think so...
      regards, marin
      - Re: Sledgehammer - Davey 14:19:48 08/25/04 (9)
        
        In Reply to: Re: Sledgehammer posted by marin on August 25, 2004 at 12:38:49:
        
        Oh, for crying out loud. Your example changed the DCR by a factor of 10! That's a much more extreme DCR change than would normally be the case when a person upgrades a crossover by exchanging inductors.
        A 2.5mH steel laminate core will probably have a DCR around 1 ohm, but a typical air-core coil of 14awg will be about 0.4 ohms, not 0.1 ohms.
        A difference...yes, but not really enough to worry about.
        Cheers,
        Davey.
        
        Re: Sledgehammer - marin 01:07:57 08/26/04 (8)
        
        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
        
        Re: Sledgehammer - Davey 06:22:08 08/26/04 (7)
        
        In Reply to: Re: Sledgehammer posted by marin on August 26, 2004 at 01:07:57:
        
        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)
        
        In Reply to: Re: Sledgehammer posted by Davey on August 26, 2004 at 06:22:08:
        
        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)
        
        In Reply to: Re: Sledgehammer posted by marin on August 26, 2004 at 07:42:16:
        
        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)
        
        In Reply to: Re: Sledgehammer posted by Davey on August 26, 2004 at 14:47:53:
        
        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)
        
        In Reply to: Re: Sledgehammer posted by Davey on August 26, 2004 at 14:47:53:
        
        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???
    - Sledgehammer changes - Thanks all (nt) - jharris 08:43:29 08/25/04 (0)
      Thanks

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