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Thread: Another DIY M2 thread

  1. #1
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    Another DIY M2 thread

    Tons of background and technical data for the M2 is available in the threads below. No need to review here.

    http://www.audioheritage.org/vbullet...erence-Monitor

    http://www.audioheritage.org/vbullet...-M2-DIY-Thread

    I discovered the M2 components were available through Speaker Exchange over the Labor Day weekend and ordered up most of the parts. My original thought was to try a curved cabinet or something like the S4700 to avoid the blacked-out utilitarian M2 monitor look. The 4367 was released before I had a final plan....so it was a pretty easy call to borrow from the 4367 looks for my M2 box. A walnut veneer and black baffle was chosen based on member BMWCCA's beautiful monster monitors.

    I decided to go plywood rather than MDF and my first step was build a frame to attach the panels to. Doing the bracing first is bassackwards but that is how I did it. I had lots of 3/4" and 1/2" plywood scrap in the shop so I used it. Lots of glue, dozens of 15 gauge finishing nails, and a few pocket screws and I had frame to work with.

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    3/4" pine plywood was used for the inner baffle and the outer is 1/2" plywood. I used the 3" precision ports (Parts Express # 268-350) and mounted them backwards to minimize the visible flange. Outer diameter is 5.25" so I used a 4.25" hole and a 1/2' roundover bit to flush-mount the ports. Name:  IMG_20151203_184127200-a.jpg
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    A few steps later and we are here....Name:  IMG_20151222_220225946-a.jpg
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  2. #2
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    Mounted waveguide and used 1" fender washers to to cover the 1/2" holes the screws pass through. I used a double layer of 1/8" x 1/2" gasket tape (Parts Express # 260-542) around the perimeter of waveguide to eliminate concerns about sealing the screw holes. The gasket tape is much nicer to use than any of weatherstripping I have tried from the big box stores - it actually sticks where you want it to go. Lots of caulk and construction adhesive used to seal cabinet.

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    With drivers and JBL Pro badge installed....used rosewood veneer rather than walnut to get a bit more exotic look. Duratex was used for a slightly textured finish as it helps hide the flaws caused by being a hack woodworker.

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    Being bi-amped, I opted for Carol SJOOW 4-conductor 14 gauge power cable (audiophile zip cord?) with Neutrik Speakon (NL4MPR) round chassis mount connector recessed in the cabinet with 4-pole speakon connectors (NL4FX) on the cable with a pair of them on the amplifier end (wired as 2-pole of course). Obviously going for pro audio look and idiot proof connections rather than gold-plated binding posts and fancy cables. The Magic Pebbles are installed inside the cabinets adjacent to the drivers to maximize effectiveness I considered adding speaker spikes but decided to go unconventional and installed Magic Sliders so I can actually move these beastly speakers without a fight. I installed an access panel to get to the D2 compression driver and crossover. Cap screws with wood threads make for an easy solution if there is any need for access.

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    Speaking of amps, I picked up a Yamaha P2500S for the horns and a P5000S for the woofs. Supposedly the fans come on if they get hot...haven't heard them yet. Probably way more power than I will ever use at home but they should be bullet-proof. You can't see it in the photo but the rear of the equipment cabinet has cut-out so that the amps pull air in the front and out the back to the outside world.

    Crossover duty is being handled by a pair of MiniDSP OpenDRC-AN units (https://minidsp.com/products/opendrc-series/opendrc-an) with one on each speaker....excellent documentation of the work by POS (Thomas) here https://minidsp.com/forum/opendrc-pr...th-the-opendrc Total cost for amps and DSP was under $2k which seems like a bargain compared to the iTech solution. If you already have amps, the OpenDRC units will cost you about $720 counting the duty and tax invoice that FedEx sent me. Lots of untapped PEQ (IIR) filters available for tuning the system to better match the room...

    Implementation was very simple except for some issues I had with getting the input/output levels correct and running down ground hum issues introduced by adding the amps and using my Yamaha RX-A2010 AVR as the source. Getting the wife out of the house for an evening was the key. Hard to hide in this house when running frequency sweeps and some music test tracks at reference level. The DIY M2 now sound like they are supposed to (phenomenal) and they are integrated with the rest of the speakers in the home theater system. Haven't had the chance to play a good blow 'em up movie to check the bottom of the bottom end but I suspect that paired with the B460 will get the job done.
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  4. #4
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    reserved # 3

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    Senior Member srm51555's Avatar
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    Looking real good, can't wait to see the final product.

    I like the way you inverted the ports.

  6. #6
    Senior Member pos's Avatar
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    One word: Wow wow wow! (three actually)
    I like the way the sides of the horn meet the outer panel of the enclosure: looks like it is perfectly flush.

  7. #7
    Member sebackman's Avatar
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    Nice !!

    Good idea with the ports. I have much smaller cabinet so I'm still struggling with where to mount the port and how to get room for flairs. Maybe you idea can save the day. :-)

    I will try to seal the WG on the edges like you, but it may prove to be difficult due to them not being completely parallell.

    Very nice in Rosewood!

    Kind regards
    //RoB
    The solution to the problem changes the problem.
    -And always remember that all of your equipment was made by the lowest bidder

  8. #8
    Senior Member pos's Avatar
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    I did the same thing for the ports, only ordering inner flares. The version we get in europe is similar to the precision ports from parts express, but it does not sell as a full kit: you have to buy each part separately so it is less expensive to only buy inner flares rather than to put the more expensive outside flare in the inside (if that makes any sense).
    I must say I was a little bit disappointed by the quality tho: most of the flares have markings on them, and even after selecting only half of them as outside part I still have to do with visible markings on some of them...
    Maybe the outside flare have a better finish
    Anyway, I prefer a few marks than a bunch of srcew holes.

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    Appreciate all the responses. The waveguide is a tight fit (but not sealed) between the cabinet sides but there is a small gap at the surface since the sides of the waveguide are slightly tapered. I literally had to beat beat it into place after trying to sand off part of the front-back taper since the top of the waveguide would not drop into place as planned. The bottom half fit nicely. I assumed this was because the box was off but it could have been due to the waveguide being wider at the top than bottom. I never thought to check. Going with black paint on the inside edge around the waveguide helps hide the minor (and less than uniform) gap that is there. It just disappears under normal lighting and viewing distances. Using the gasket tape on the back of the waveguide allowed a bit of depth adjustment to get the edges more or less flush with the cabinet sides.

    My original plan was to have the top edge of the waveguide flush with the top of the cabinet like factory M2. Half-way through construction I chickened out and added a layer of plywood on top to get a consistent 3/4" edge all the way around.

    Next up will be trying to build an acceptable grill and ordering some smoked glass for the tops. They weren't in the living room for 48 hours before knick-knacks and a candle holder appeared on top of them. A metal candle holder with bare metal feet

    The wife is breaking them in as we speak....Judge Judy and Law & Order never sounded clearer.

  10. #10
    Senior Member Ed Zeppeli's Avatar
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    Those look great!
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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    sooooooooo jealous! Stunning.

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    Stunning execution!

    I like the "body on frame" construction method. Did you add any damping between frame and outer panels, a la Mark Dodd (Tannoy DMT/KEF LS50/new KEF Reference)?

  13. #13
    Member Fitero's Avatar
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    Thank you for sharing. Very nice!

    I am waiting for my parts to start building my own, and I was getting nervous about making the cabinets exactly like the original M2s. Your method of construction seems better suited to my limited skills.

  14. #14
    Senior Member srm51555's Avatar
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    Quote Originally Posted by pos View Post
    Anyway, I prefer a few marks than a bunch of srcew holes.
    Very true, I plan on inverting them as he has shown this summer when I send the cabinets off to paint. Right now mine look like they came as a kit from parts express.

  15. #15
    Senior Member Ed Zeppeli's Avatar
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    You really can't go wrong with those pro Neutrik Speakon connectors. Just look at the contact area on them!

    Good job.


    Warren
    DIY Array, 2242 sub, 4408, 4208, Control 8SR, E120 Guitar cab, Control 1, LSR305.

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