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What box to build? 2 Mach5 IXL-18 with a Behringer NX6000D

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  • What box to build? 2 Mach5 IXL-18 with a Behringer NX6000D

    Hello,

    I got a good deal on 2 Mach5 IXL-18 with a Behringer NX6000D amp and I am keen to build my first DIY sub box (I have moderate wood working ability, and live in Canada, so buying flat packs will not be a great option).

    But I am wondering what I should build.

    For background info:
    Use will be 75% music, 25% HT
    Room is ~ 16ft x 10ft
    The way the room is laid out, one sub will most likely go right behind the main listening position and one directly in front / center.

    Priorities for me would be (in order):
    #1 Accuracy and musicality, so I was looking into a sealed box. But then I was playing with WinISD and noted that I may not be able to get as deep as I would like without extreme DSP (which I am ok with) but also extreme cone excursion (which I don't want to blow these subs).

    #2 Low extension, the lower the better (although this is my first proper sub, so we shall see how addicting that low end really is), so then I was maybe thinking about a large EBS build. Would a full or mini marty be a good fit?

    Thankfully space will not be an issue, so really any box size I would make work.
    Also, I typically listen below reference, so will not need them to hit crazy high levels.
    I just want it clean and then deep.

    Super keen for any recommendations.
    Also, since this is my first build, if there are any recommended sites for designs (mostly if ported is the way to go) that would be great!

    Sub specs if that helps:
    Mach5 IXL-18
    T/S Parameters
    Fs = 17.7 Hz
    Re = 3.4 Ohms
    Qes = 0.39
    Qms = 5.59
    Qts = 0.37
    Mms = 434.3 grams
    Rms = 8.69 kg/s
    Cms = 0.184 mm/N
    VAS = 274.1 litres
    Sd = 1029.2 cm2
    Xmax = 22 mm
    Cone Diameter = 36.2 cm
    Le = 6.09 mH
    Bl = 20.51 Tm
    Power Handling: 800 Watts SPL (2.83v/1m): 89.2 db
    Ported: 200 litres (7 cu.ft.) 19hz tuning
    EBS: 365 litres (12.88 cu.ft.) 15hz tuning

    Thanks!

  • #2
    Most music only goes down to 40Hz or so. LFEs maybe 30 (or slightly less).
    A 4cf closed box w/be OK for music.
    Not much advantage to your EBS tuning (over the 7cf box). MANY "sub" amps rolloff the bottom end below 20Hz anyhow. What does your amp do?
    You can still reach high 20s in a 5cf box w/a 6"id x 24" long port tube.

    Comment


    • #3
      I kinda like sealed better for music, too. One trick is to design a ported box, but have a plug for the port when you don't need the ultra low frequencies for HT.

      Other tricks I've seen but not tried, are: stuffing the port with for example a chunk of waste cotton insulation (Ultra Touch for example). Putting a bundle of common soda straws in the port, sized to fit snugly. Both make for a very lossy port.
      Francis

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      • #4
        Thanks for the thoughts and advice!

        Yeah looking into it more, I am wondering if I should:

        A) Make a Martycube as it is 4.75 c.f., tuning = 20hz and then I could block the ports to effectively get a sealed 4.75cf sub (Which is super close to the recommended sealed size of 5cf by the manufacturer) - which gives a Qtc of 0.65

        B) Make The V.B.S.S. as it would fit nicely in my room, be 6.25cf and tuned to 20hz. This has better low end extension as per WinISD yet I just don't know if it would be a good idea to use this design if I am going from ported to plugging the ports as that would give a Qtc of 0.6
        Is that enough of a difference of the Qtc (0.65 vs 0.6) that I should avoid this design compared to the Marty cube if I am thinking of occasionally plugging the ports?

        Thoughts?

        Comment


        • #5
          Originally posted by johnp98 View Post
          Thanks for the thoughts and advice!

          Yeah looking into it more, I am wondering if I should:

          A) Make a Martycube as it is 4.75 c.f., tuning = 20hz and then I could block the ports to effectively get a sealed 4.75cf sub (Which is super close to the recommended sealed size of 5cf by the manufacturer) - which gives a Qtc of 0.65

          B) Make The V.B.S.S. as it would fit nicely in my room, be 6.25cf and tuned to 20hz. This has better low end extension as per WinISD yet I just don't know if it would be a good idea to use this design if I am going from ported to plugging the ports as that would give a Qtc of 0.6
          Is that enough of a difference of the Qtc (0.65 vs 0.6) that I should avoid this design compared to the Marty cube if I am thinking of occasionally plugging the ports?

          Thoughts?
          Either way sounds OK to me. I like the sound of lower Q sealed. The rolloff is more gentle, and the F3 may be very slightly higher, but most likely the room gain will help lift the low end response.
          Francis

          Comment


          • #6
            WinISD will do it, of course, but for looking at the pros and cons of something simple like sealed box Q, I often use AJSealed: https://www.ajdesigner.com/speaker/ajsealed.php

            No malware or viruses, I've used it for years. It's not comprehensive, but you can quickly get an idea what happens with different Qs.
            Francis

            Comment


            • #7
              I'd suggest a large ported design of your own. Tune it really low, and cross it 4th order around 70hz. That's my recipe for good sound on movies, and music. If your amp rolls off at 20hz, well, that's a shame. I bought one that does, but would prefer that the manufactures squeeze another 5hz out of it them, or make it so that it can be bypassed. I understand they are trying to protect the drivers from excursion below tuning, but that's not needed when you tune to 16hz for example.

              Comment


              • #8
                Ok, I was almost starting to suffer analysis paralysis, so my wife ended up making the decision that the VBSS would be better as it would have more placement options in our room and I could also get the to fit on one sheet of MDF each.

                Anyways, we are using a port tune to 20hz yet can port plug to 15hz and to a sealed configuration.

                Man I am excited to get these things up and running!

                Any suggestions for wiring guides for the NX6000D and subs?
                Thanks again for all the input!

                Comment


                • #9
                  A few minutes of analysis paralysis isn't a bad thing on a big expensive project, but it sounds like you've decided. I'm thinking you'll be happy with the result.
                  Francis

                  Comment


                  • #10
                    Originally posted by johnp98 View Post
                    Ok, I was almost starting to suffer analysis paralysis, so my wife ended up making the decision that the VBSS would be better as it would have more placement options in our room and I could also get the to fit on one sheet of MDF each.

                    Anyways, we are using a port tune to 20hz yet can port plug to 15hz and to a sealed configuration.

                    Man I am excited to get these things up and running!

                    Any suggestions for wiring guides for the NX6000D and subs?
                    Thanks again for all the input!
                    I looked at the specs on your amp. That's a lot of amplifier, and you have dsp. So...... You can add a little boost at 15hz maybe, and tune very low to control the excursion. (Maybe 13hz tune.) You really should run some sims to verify your options. My suspicion is that one of these subs could be sufficient. I have a single 15" in a 7 cu-ft ported box, and with about 100w, it's all I need even for HT. That said, if the amp has a limiter, I'd dial it in initially to hold [power down to about 180w. Change it later as needed. (If needed.) You may run across some shows, or music with more deep bass than you expect. I've clicked on a You-tube that was unusually loud. I've pressed the up volume by mistake, and made the system way too loud before realizing what was happening. (I watch a projector in the dark.) Some movies will vibrate your whole room. Stuff may come off the walls, or shelves.

                    Comment


                    • #11
                      I agree one sub could probably put out enough raw power, but two will help control room modes better if they're strategically placed.
                      Francis

                      Comment


                      • #12
                        Just finished building these! Man what a difference from two general 6-8" store bought subs!

                        Super happy with the results!
                        Thanks for all the advice!

                        Just wondering for using DSP, it seems like most people look at the combined frequency response of both the subs and then apply one filter to both subs. But would that not effectively double whatever alterations the EQ is calling for (as it will be applied to both subs)? Would it not make more sense to apply individual filters to individual subs to get each sub as flat as possible (with the goal of both then combined being flat)?



                        Comment


                        • #13
                          I've not used two subs, but "theoretically", I'd probably notch any severe peaks in just the sub that causes them.

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