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Thinking too hard about B652 mods

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  • Thinking too hard about B652 mods

    I blame this on the recent thread mentioning adding a Dayton premade crossover into the B652-air. It made me curious if any of the premade crossovers could end up being pretty ideal, if not with the original drivers than maybe with some upgraded ones.

    Probably one of the most obvious major upgrades for the B652-air would be swapping the default woofer for something like the RS125-8 that can reach up to crossover with that tiny AMT with a friendly handshake instead of a stumbling mess of skinned knees and elbows. I was thinking the RS125 and a ZenaWarriorPrincess frisbee weapon/adapter ring could work pretty nicely along with a premade crossover. But the very high crossover point needed for that AMT still kind of bothers me along with its somewhat ugly peak->valley->peak swinging FrequencyResponse. This looks like a common thing for most of the smaller/cheaper AMTs though I'm guessing they probably sound nicer than their squiggly lines look.
    I was also mistakenly looking at the smaller B452 when considering the box-size and woofers...whoops.

    I guess there's no need for a high-crossing woofer if I'm nitpicking my way into a different tweeter that crosses lower and has a somewhat smoother FR. The ND16FA-4 tweeter looks pretty smooth and can cross quite a bit lower while keeping costs low. In that case the cheaper DS115-8 woofer does a really good job still keeping a nice bottom inside the tiny box. This is assuming a 1-3.8" X 8" port is also used to unseal the box.

    With the DS115-8 and ND16FA-4, it looks like there are some viable premade lowpass+highpass options from PE:
    https://www.parts-express.com/800-hz...sover--266-450
    https://www.parts-express.com/dayton...tave--260-1894
    ....plus a 16ohm resistor between the highpass and tweeter to take it down to about 79-80db@1watt. It looks like the resistor will peak at 15watts, so I'm not sure if 10watts would be enough.
    Tweeter wired out of phase. All the XO's have wire clip tabs just like the drivers, so these could potentially be done without soldering.

    That lowpass is a Butterworth instead of Linkwitz, a kind of lucky find for the woofer.

    Keeping to the same size (small) ~3.0litre box limits the woofer to around 65hz with the port, but that's a nice place for crossing to a subwoofer while keeping some ability to play without one (more bass than the b652's at least).
    Duh, still didn't realize the B652 is a nearly 6L box and I was looking at the roughly half-volume B452 dimensions.


    What about the TCP115-4 woofer instead?
    That could be a good option if you like all this but want it at 4ohms and want to reach a little deeper from the small box. The TCP woofer prefers a different, Linkwitz lowpass that costs more and basically makes the woofer's cheaper price moot, and the TCP itself is less sensitive enough that being a 4ohm speaker doesn't make it significantly louder than the 8ohm DS115. But the TCP does reach lower, so it should be a good option if 4ohms isn't a problem.
    This is a good lowpass for the TCP115-8:
    https://www.parts-express.com/dayton...tave--260-1788


    Sorry if this has already been done to death (or if it already exists as a PE project that I missed). The B652 put me in a mood to try something small and I wanted to see if it could work with the PE premade crossover boards. It was still a fun bit of mind wandering for me even if it ends up being redundant or flawed. I'm pretty sure the Cnote/pair kit is all-around better as well as cheaper though larger, and the mk402x probably makes all of this pretty pointless unless its XO is higher or somehow less-ideal.
    Feel free to point out any ideas or improvements or if you notice additional places something like this falls on its face. I don't mind, and maybe I'll learn something. :D
    Last edited by LOUT; 05-22-2020, 02:49 PM. Reason: realized I kept referencing the wrong tweeter. fixed.
    My first 2way build

  • #2
    Why on Earth use a pre-made crossover? The chances of it working well are very slim.
    Francis

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    • #3
      Originally posted by fpitas View Post
      Why on Earth use a pre-made crossover? The chances of it working well are very slim.
      I went through and SIMed the different premade options to find ones that seemed to fit these drivers. These particular premades with these drivers should give full BSC and cross around 2khz leaving a small dip while resisting combing/overlap and avoiding showing or pushing the tweeter at/under FS.
      My first 2way build

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      • #4
        Just make a new cab and you've got it.

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        • #5
          I should've listed the premade crossover parts for anyone who wants to doublecheck or sim.....or test if they have enough parts laying around within grabbing distance.
          The highpass looks like a 2.8uF cap, 0.73mH coil and a 16ohm resistor between the XO and tweeter.
          The DS115 lowpass is a 2.3mH coil and 17uF cap.
          The TCP115-4 lowpass should be a 1.6mH coil and 25uF cap.


          Originally posted by djg View Post
          Just make a new cab and you've got it.
          I thought PE used to have more flatpacks than they seem to have currently. I feel like there used to be a plain-box MK or B652 (or the smaller one), but I don't see much of anything that doesn't already include the drivers besides a larger 6.5litre knockdown.
          Maybe something for someone who likes woodwork but dislikes soldering or XO laying-out, who wants a smaller-than-most bookshelf? Kind of the only reasoning I can think for this. :/
          My first 2way build

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          • #6
            I am a huge advocate of DIY for the sake of DIY and love when people re-purpose commercial cabinets to a higher calling - but these B652 cabinets are not very well built, in fact the speaker by and large is pretty poor. I am not sure it is worth the work to fit different drivers on the baffle. There are a very few modern 6.5" woofers that will drop in and offer reasonably smooth response as high as you may want to go, but the cabinet still remains inadequate.

            Some of my friends and family have asked me about these sub-$100 bookshelf speakers popping up everywhere and I always recommend they look at used stuff from the 2000's instead - there are a lot of solid used commercial speakers in that price range that offer better construction, better drivers, better crossover design for just a few dollars more than the B652.

            On the other hand, if all a person has is the money for the B652 and absolutely nothing more - then that is exactly what they should buy. That is exactly what these are intended for. The cheapest possible way to get a pair of speakers. We cannot DIY anything worthwhile that cheap, and even inexpensive but otherwise decent performing used speakers cannot generally be found that cheap so the B652 (and Micca and whoever else) establish themselves at the bottom tier knowing we cannot build or buy anything cheaper without ending up with the same performance - and who wants to do that? Even my dirt cheap designs of the past used correct cabinet construction and design and utilized competently designed crossovers. That all adds up - even using PE buyout drivers (when they still sold awesome buyouts at awesome prices) the cost exceeds the B652 (but so does performance - by a mile).

            End of soap box - have fun and report back on your mods. It is likely a lot of DIY'ers got their start by wondering how to improve their inexpensive commercial systems.

            Shameless plug: the Cabrini Redux can be built for very little money - in fact if you just buy a couple Handi-panels of 3/4" MDF, a bag of polyfill, and a terminal cup you can build the pair for ~$75-80. They are way more than 2x as good as the B652, easy to build etc.

            http://techtalk.parts-express.com/fo...-cabrini-redux
            Don't listen to me - I have not sold any $150,000 speakers.

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            • #7
              Well said Johnny. I still need to do more work on my B652-Air retrofit but this is a product of wanting to hear the AMT's, already having unused drivers laying around, and wanting to learn how to use my measuring equipment. The cost of the 2 DS135s and whatever crossover as an upgrade adds up just like you mentioned. I'm always looking for an easy cabinet solution for a speaker build.
              My Builds - Vigor (Nola Brio Knockoff) - Overnight Sensations w/ Voxel - Speedsters in surplus boxes - Zaph B3N's in bamboo - Classix II in BR-1 cabinets - Dual TPA3116 D2 amp in an old music box - Mariposas

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              • #8
                By the time I started thinking about using a different tweeter the whole idea shifted toward being a more off-the-shelf than usual small scratch build instead of a mod. I mentioned it might make more sense for a DIYer who loves woodworking but dislikes the electronic/soldering aspects (likely the exact opposite of silverD's retrofit) but I probably should've made that much clearer.
                Mods of the 652 were what started this, but it wandered pretty far by the end.

                For someone more focused on modding something small and cheap, the MK402 is probably a better platform because it starts with nice drivers and a prettier box....though it's also nearly twice the price of the standard B652 and the TD20 (while good) isn't as interesting or exotic as the AMT in the B52-AIR.

                Ha, I just realized the B652 uses a nearly 6L box. I typed "B652" into PE's search but it also shows the smaller ~3L B452 and that's the one I clicked and took the dimensions from. At least now the difficulty I had squeezing any low end from woofers over 4inches makes sense.
                It's still cheaper to grab some MDF or plywood and build a pair of boxes though.
                My first 2way build

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