MMG efficiency

Discussion in 'Archived Threads 2001-2004' started by Brandon B, Feb 27, 2002.

  1. Brandon B

    Brandon B Second Unit

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    I am building some speakers that are rated at 8 ohm 90 db 1W/1m which can handle 100W, and wondered how they will compare to a pair of Maggie MMG's I am presently using.

    The MMG's I believe claim to be 87 db 1W/1m when used with an amp rated at 150W into 8 ohms. IIRC, someone stated this translated into about 83dB, and able to handle 300W, since they are actually 4 ohm speakers.

    Basically I am trying to figure out if the DIY's will go slightly louder, or the MMG's.

    ??

    BB
     
  2. ThomasW

    ThomasW Cinematographer

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    Brandon

    The little Maggies aren't very efficient. I'd tend to believe the 83db. I replaced my DIY MTM rear speakers driven by Adcom 545, with a pair of MMG's. The Adcom didn't have enough power to get the MMG's up to speed with my ESL array, so I had to put in a Aragon 8008. That did the job.
     
  3. Colin Dunn

    Colin Dunn Supporting Actor

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    MMGs are not very efficient. The 86dB/2.83V/1m is actually 86dB/2W/1m into 4 ohms. That's 83dB/1W/1m into 4 ohms. Many good power amps will provide 1.5X-2X the 8-ohm RMS wattage into 4 ohms.
    The MMGs are also 'line sources' instead of point sources, so the volume level drops off at 3dB per doubling of distance, not 6dB as is the case with most dynamic speakers.
    Bottom line: You can still get satisfying volume from the MMGs if you have a good, powerful amplifier. I'd recommend a power amp rated for at least 100W into 8 ohms (150-200 is better).
    Sensitivity, by itself, does not define maximum volume capability. How the speaker interacts with the amp and room, as well as the volume levels where its drivers begin to distort, is what defines how loud you can play your speakers.
    The real limit on volume with MMGs and 1.6s is their ability to handle loud, bassy scenes. Scenes like the pod race from "Star Wars: TPM" or the ship sinking in "Titanic" have lots of bass. Unless you are using a subwoofer with crossover to filter out the bass, you will hit the panels' excursion limit, and hear an ugly 'cracking' sound as they 'bottom out.' The speakers could go even louder for midrange/treble material, but their bass capability was exceeded when I tried to watch those scenes at movie-theater volume levels. Switching to 'small' in my pre-pro filtered out the bass and routed it to the sub, which was built for those loud rumbly sounds. No more distortion, but now the Maggies are only handling 80Hz and up. I think an Outlaw ICBM is in my future... [​IMG]
    With a Sunfire Cinema Grand (5 x 200W into 8 ohms, 5 x 400W into 4) I can achieve near reference levels with 5 channels of Maggies (all of which have similarly low efficiency ratings).
     
  4. Andrew Pratt

    Andrew Pratt Producer

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    Colin what are your mains? I can still bottom out my 1.4's at 80 hz if I really push it but its getting pretty damn loud by that time and they've never bottomed out in movies at 80. I'm now running them at 60 hz and they seem to do fine at that setting...
     
  5. Colin Dunn

    Colin Dunn Supporting Actor

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    Andrew -

    I am running MG3.3s for mains, and MG1.6s for rears. I used to use MMGs for rears, but upgraded when I got the MG3.3s.

    The MG3.3s have never bottomed out. The 1.6s bottom out with challenging bassy material when fed a full-range signal, but I haven't bottomed them out when set as 'small,' even when I crank the volume on an action movie.

    The times I've bottomed out the 1.6s, I was probably encountering bass peaks of over 95dB. The MMGs were easier to bottom out, probably around 85dB peaks.
     
  6. Brandon B

    Brandon B Second Unit

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    Thanks guys.

    Actually, it's not a "which should I use" question, I am definitely going with the DIY's, which will each have their own woofer actively XO'ed at 250. I was just wondering if I would pick up a little loudness headroom when I change, or lose a little.

    I am running the MMG's right now with an Odyssey Stratos, and the woofers (in temporary boxes) with a crown macrotech 2402. The MMG's get plenty loud right now, and the Stratos is only 190W at 4 ohms.

    I will also have a large sub for HT stuff, so the woofers will only be working hard on music.

    BB
     

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