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Thread: Project M2 DIY Thread

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    Senior Member srm51555's Avatar
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    Project M2 DIY Thread

    Since the JBL Master Reference Monitor thread is so massive I'm staring a thread that I and others can document our M2 DIY process if the. Here are some links that I was able to reference. Thank you for all of your contributions that made my and others project happen.

    Schematic of the M2 - Note: C2 in the schematic shows a value of 33.3uf, this is a typo. the correct value is 3.3uf

    DSP File

    Inside the M2

    Outside the M2

    M2 Dimensions

    Horn Mounting

    Horn Mounting pt2

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    Senior Member srm51555's Avatar
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    Here is the photo progression of my project. Cabinets were glued with Titebond 2 and Spax MFD specific screws.

    I originally started out with using 1"x2" strips of particle board for bracing. After some recommendation I moved over to using Baltic Birch to achieve a better brace matrix. The particle boards were glued and screwed so they stayed in. With the extra volume they took up I was unable to brace exactly like the M2 in the top and bottom sections.
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    Next came the primer to seal the inside. It's a 2 part epoxy primer and I sprayed 2-3 coats of it on. I taped certain sections of the cabinet and bracing I could properly glue and screw baffle on.

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    Next came the dampening material. I was unable to locate the Owens Corning stuff POS recommended locally. I then was recommended two other options. Wrap on 16550 Bulk Roll Fiberglass or get the regular pink stuff from Home Depot and make it 1". My original plan was to use the Wrap on stuff but I realized I already had a roll of the pink stuff and figured I'd better use it since I've been storing it for this occasion.

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    I left the horn cutout process till after the baffle was installed because I wanted to be sure the horn was in the correct place.

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    Senior Member srm51555's Avatar
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    Current state, I still need to drill holes for the woofer and horn. Also I was original going to paint to standard black. Since then I've run the thought of painting it some other color, any thoughts. These will be in a dedicated room so WAF is not a problem.

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    I think you'll want that fiberglass to be lining all the interior surfaces except the back of the baffle - especially behind the woofer.

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    Senior Member srm51555's Avatar
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    That is the plan. I left it out because I was going to send it to paint. Since then it's gotten to dang cold to properly prep so I will most likely put it in so I can finally hear them and be left with an unfinished cabinet for the winter.

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    Senior Member pos's Avatar
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    Quote Originally Posted by srm51555 View Post
    As you know the schematic in this doc has a typo: C2 should read 3.3uF instead of 33.3uF.
    If you could edit your first post to make this clear that would probably be helpful.

    Here is the correct schematic, in appendix 3: https://docs.google.com/document/d/1...h.267sxg2itu1h

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    Senior Member srm51555's Avatar
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    Quote Originally Posted by pos View Post
    As you know the schematic in this doc has a typo: C2 should read 3.3uF instead of 33.3uF.
    If you could edit your first post to make this clear that would probably be helpful.

    Here is the correct schematic, in appendix 3: https://docs.google.com/document/d/1...h.267sxg2itu1h
    Very good, post is updated. I was waiting for confirmation before I call Parts Express and try to return these out of the 45 day policy.

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    Quote Originally Posted by srm51555 View Post
    Current state, I still need to drill holes for the woofer and horn. Also I was original going to paint to standard black. Since then I've run the thought of painting it some other color, any thoughts. These will be in a dedicated room so WAF is not a problem.

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    If you plan to use 'standard' fibreglass you may want to generously spray it with hairspray to fix those pesky fibres.

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    Senior Member srm51555's Avatar
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    Thanks for the tip. Who knows, I may rip this stuff out and replace it with the wrap-on stuff, it's all pending on how sealed I can get the cabinet when painting it.

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    Senior Member Lee in Montreal's Avatar
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    I suggest you router all corners with a straight bit, to make them flush. It will take 5 minutes per cabinet and they will look even better. ;-)

  11. #11
    Senior Member srm51555's Avatar
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    My straight bit got plenty of use with this project. I usually set the internal cabinet depth with the bracing and shave the excess off like you recommended. It really does turn a ok cabinet into a great one. I also used it on the bracing and horn hole. After making a jig of the part I needed to make a few of all I did was rough cut with a jig saw then cleaned up with it.

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    Member Alobar's Avatar
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    Nice work! Should be a good thread... ! I really enjoy watching the progress on these DIY cab build projects. Makes me want to try building a speaker pair myself someday. It also shows how much goes into these projects than simply building a box or something like a kitchen cabinet. Looking forward to seeing the final result!
    L200's biamped with 2216Nd1 LF, and 077's added

  13. #13
    Senior Member srm51555's Avatar
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    Quote Originally Posted by Alobar View Post
    Nice work! Should be a good thread... ! I really enjoy watching the progress on these DIY cab build projects.
    Thanks. I think we all like watching the progress of members speaker or systems, at least I do. Photo's are so much easier with camera phones.

  14. #14
    Member Fitero's Avatar
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    I've been following the thread with great interest, as I too would like to start building myself a pair of M2 clones.
    Other than the dour black exterior, I want to copy the original as closely as possible

    I did some calculations of the cabinet dimensions and came up with the following;

    Volume = 147.42 Litres
    Bracing Volume = +/- 7.5 Litre
    Overall Volume = 140 Litres

    I am most puzzled by the port dimensions. The parameters provided by 4313b (JBL M2 System Simulation) and Valentin are what I have been comparing.

    Judging from the pictures, the ports flare to +/- 4" from a minimum inner diameter of approximately 44.5mm to 46.5mm. (+/- 1.75")

    I don't know squat about such things, and am unaware if JBL contemplates the Bernoulli Principle while calculating Ports. It sure appears this way to me.

    Am I missing something here?

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    Marketing Propaganda fwiw:

    M2 ENCLOSURE
    Small Footprint, Extended Bass Performance, Patented Low Frequency Port Design

    Extended low frequency performance and high SPL can be the formula for unwanted resonance. The M2 enclosure is constructed of rigid 1" MDF and with the aid of JBL’s interferometer, extensively braced for rock-solid stability at the system’s full rated power. The enclosure incorporates a JBL patented Slipstream port design with internal flares that ensure low frequency efficiency while eliminating noise caused by port turbulence. Architecturally elegant, the M2 enclosure occupies a relatively small footprint, and can be transported to various working environments.

    http://www.jblpro.com/www/jbl-story/...t#.Vmixz7-TVx4

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