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Thread: Quick & Dirty Modular Mains

  1. #1
    lfh
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    Quick & Dirty Modular Mains

    I've decided to build a pair of old school mains for an upcoming demo in the company's new listening room (more on the latter in a dedicated thread later on). The system must be up and running by the 8:th of May, so this project must indeed be quick (as in "10 days to go"), and dirty (as in "cheap prefab boxes"). In order to save time, I'll run the system 3- or 4-way active, and (if time permits...) tidy up the FR with an inverse filter. I do have all the components, amps and crossovers, as well as boxes with uncut baffles, so now it's "just" to build the speakers and dial them in. (The room also needs lots of attention to be operational -- the final acoustics preparation is still on the drawing table...)

    As evident from the drawing below, the system is well suited for experimentation. Apart from the various modes listed in the drawing, the bass bins will be used as distributed subs in a 5.1 setup for experiments with room mode suppression. Finally the monitors might end up flush mounted in "real" cabinets -- if I can convince the Genelec and Geithain camps, that is

    Any and all comments and suggestions would be highly appreciated!
    Fredrik
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  2. #2
    Administrator Robh3606's Avatar
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    If it were me and you were hell bent on using 2 15's I would use 2234's and set up the lowend like a 4435. You would be running a 4 1/2 way. If not I would just use a single 2235 or a 2245 cabinet size permiting.

    Rob

  3. #3
    lfh
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    Quote Originally Posted by Robh3606 View Post
    If it were me and you were hell bent on using 2 15's I would use 2234's and set up the lowend like a 4435.
    Me too -- if I had the drivers. 4 x 2231H is all I have.

    Fredrik

  4. #4
    lfh
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    X.5 way for "baffle step" compensation

    It just occurred to me that the second bass can likely be brought in, such that the "baffle step" is compensated for. Thanks for bringing up the 4435:s.

    Furthermore, I have on the roadmap to explore using different tunings of the top and bottom cabinets. Add to this the possibilities for directivity control, and maybe even avoidance of energizing vertical (odd-order) axial modes...

    Conclusion: Dual 15":s are way cooler than a single 18"

  5. #5
    Administrator Robh3606's Avatar
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    Well what ever you do please drop a couple of pictures up here on the site. Looks like it will be a fun project. Good luck with it.

    Rob

  6. #6
    Administrator Mr. Widget's Avatar
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    Go with whatever you can implement the quickest for your initial audition. When you have the time you should experiment with using the woofers in "helper" mode as well as your pseudo MTM mode.

    Schedule your set up so that you have a couple of days to tune the system. To really get the best from a new four-way in a new room, I would expect you will need a week or two of micro dialing-in to really be "there". I would guess you could have something to be proud of with only a couple of days of set up.

    Looks like a really nice project. Do keep us posted.


    Widget

  7. #7
    lfh
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    More thinking needed...

    Rob, Widget,

    thanks for your advice and encouragement!

    As to strategy, I'll work on the room first: We'll do a 5.1 demo (using Genelec 1030A:s), and my stereo demo is optional. I think allocating two days for tuning is a wise idea. Furthermore, I need more time to think over the speaker design before cutting holes I might regret, so I schedule the construction phase for the coming weekend. (BTW, I'll build a dolly and incorporate space for rubber isolators and height adjusters, so the speakers will not rest on rigid stands according to the drawing I posted.)

    As to tuning, I'll try to work out as much as possible in the computer first. The baffle layout, "dog house" tuning, crossover design etc certainly needs more work. Even though I plan on using parametric EQ, I want the system to be as well-behaved as possible (as time permits) when running without. The same holds true for the room -- the design will be tested and adjusted virtually first.

    I'll post some pics ASAP.

    Fredrik

  8. #8
    lfh
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    Picture

    I've posted this picture before but here goes anyway. Given the history of this piece of wall (it comes from now defunkt Polar Studios, once ABBA's private studio), I'll just cut down the existing baffle. This is also in line with the Q&D theme

    If someone complains about the looks, the baffle can always be hidden behind a speaker grille (with a hole for the horn, of course).

    PS
    Hey, Zilch, I hope I'm not infringing a trademark here
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  9. #9
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by lfh View Post
    Hey, Zilch, I hope I'm not infringing a trademark here
    Nope. Nothing proprietary about a mindset....

  10. #10
    lfh
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    Going 4.0...?

    One more thing:

    I'm playing with the idea of setting up a 4.0 rig. The lower two horns could be run together with the extra LF cabinets as Ls and Rs speakers. After all I do have 4 x 2441:s and a pair of "cat eyes" laying around... All I need to pull this off is an extra crossover and some amps. I bet I could borrow that stuff...

  11. #11
    lfh
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    Yep! 4.0 with faux HR-1VF:s it is!

    OK, so I've made up my mind: I'll shoot for a 4.0 setup! This route has the additional advantage of making experiments with 4 subs relatively easy since Ls and Rs are almost in the right positions already.

    Furthermore, I've decided to take the modularization to the limit and break out the tweeters to separate MDF-frames. Hereby "true" MTM:s are possible, and I can experiment with alternative tweeter positions by putting one frame above the mid-horn and another below and switch on the fly.

    I think I'll skip the baffle offset and deal with the edge diffraction hump using other means. Looks is important too! With a symmetric layout and fabric grilles, non-expert visitors will of course think that we've got four Westlake HR-1VF:s (or maybe not... )

    This will be fun! There's a second-hand record store close to the office that has an impressive assortment of old quad LP:s... The only thing missing to make the nostalgia trip complete is to cover the walls with fake wooden and stone panels (see this old Tom Hidley room).

  12. #12
    lfh
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    Current pics

    I´m two 2122H:s short of building four four-ways. Someone told me I have too many speakers, but obviously my driver collection is too small...
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  13. #13
    lfh
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    Q&D MF cabinet

    Instead of cutting lots of holes in the box to make the 2441 and 2405 fit (as I originally planned), I´ll just mount the MF assembly in this cabinet.

    Note the cheesy (fake) walnut veneer. It really would match fake wood panels
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  14. #14
    lfh
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    Status report

    Today I prepared the baffles. Bracing remains to be done (I've only got time for a bare minimum until the demo on Tuesday...).

    Of course I couldn't resist playing a bit with the boxes First an MTM:
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  15. #15
    lfh
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    MTM cont'd
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