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Recommendations for Speakers/Crossover for beefed-up custom Blast Box build

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  • Recommendations for Speakers/Crossover for beefed-up custom Blast Box build

    I recently built the Blast Box for a friend, and now I want to create my own custom boombox that uses larger midwoofers and a larger sub. However, I'm a noob at building, and I don't know how to choose speakers or design a crossover. I plan to build a custom enclosure, so I don't need to use the same dimensions as the blast box. I also plan to keep the midwoofers in a sealed enclosure just like the original blast box. For the midwoofer, I'm looking for something around 4.5 to 5 inches. For the sub, something around 8 inches. I don't want to drastically increase the size of the boombox by adding a much larger sub. In terms of powering my custom boombox, I'd like to keep the same amp as the original blast box if possible to keep things simple, and I'll use the upgraded battery pack option.

    I understand that I can't just pick a highly rated midwoofer and a highly rated tweeter and expect them to blend perfectly, so I'd like to ask you all for help. One thing that I loved about the original Blast Box was the excellent off-axis performance. There wasn't too much difference between standing right in front of the speaker, and standing way off to the side. I believe this is due to the tweeter the OG Blast Box uses - I haven't seen another tweeter that comes close to the off-axis consistency of this tweeter.

    Click image for larger version  Name:	Tweeter freq.PNG Views:	0 Size:	197.5 KB ID:	1483592

    I would like to use that same tweeter if possible so I can retain the great off-axis performance. For the mid woofer, I was thinking something like this - And for the subwoofer, perhaps the following paired with a 10" radiator -

    My midwoofer and sub suggestions are based solely on reviews, and not on how well they would blend with each other. Do the speakers/tweeters/sub that I listed seem like a good combination? If so, any suggestions for the crossover? I'm also open to other speaker suggestions if they would work well using the same amp.

    Edit: link to the amplifier -

  • #2
    That single woofer with the 100watt amp (probably less, depending on the power you can supply it) will reach ~106db or less...closer to 100db after baffle-step, so I think the mids only need to reach 97-100db peaks to keep up.
    I think your choice for subwoofer is a solid budget option and I think those tweeters are well-liked, but I think smaller midwoofers will still keep up just fine and pair a little nicer with those tweeters if they really need to crossover around 3Khz. I think a 3" - 3.5" midwoofer with high enough efficiency and wattage-handling should be plenty. Something like the PC83 or DMA80/DMA90 might be worth a look..though I'm not sure if they fit the appearance you're after (the DMA have a square frame and the PC have a somewhat squared and narrow and awkward frame).
    The smaller midwoofer helps avoid some directionality/"beaming" which lets it cross to the tweeter at slightly higher frequencies compared to a larger midwoofer.
    I don't think the CF120 is an awful choice, just that there might be slightly better options.
    My first 2way build


    • Momma's Big Boy
      Momma's Big Boy commented
      Editing a comment
      Thanks so much for the advice. I should elaborate more on why I want a larger midwoofer. I am planning to use the boombox for street performing. I will play a backing track on the left audio channel, and I will play my guitar through the right audio channel (I have a guitar processor that will give the guitar it's tone - I don't need the boombox to act like a traditional guitar amplifier). Because the left and right audio channels will be distinct, I thought it would be better for each midwoofer/tweeter pair to have a larger range - hence the bigger midwoofer to hit lower notes. Do you think my logic is solid, or should I still consider a 3" to 3.5" midwoofer? I'm open to swapping out the tweeter to blend better with the midwoofer if the off-axis response is good.

  • #3
    I'm not sure, but that sounds like good reasoning to me...assuming the backing tracks are mono (or at least not bad-sounding when played only left/right or summed). I'm also guessing it'll end up placed on the ground where there could be some natural bass-boosting similar to placing a speaker right against a wall.?

    Do you have any ideas how much louder than the original version you'll need this to be?

    Do you already have any parts that you're planning to use, or is this starting from scratch?

    Is the built-in tweeter grill important or are other tweeters an option?
    My first 2way build


    • Momma's Big Boy
      Momma's Big Boy commented
      Editing a comment
      The backing tracks are indeed mono. And yes, it will be placed on the ground, though I won't be right against a wall.

      I don't need the amp to be louder than the original version - I just wanted a more full sound with better low end. That's why I was thinking of larger speakers. And I want the left/right channels themselves to have a larger frequency range so there's more distinction between the backing track on one channel and my guitar on the other channel (rather than the low end from both channels only playing through the sub)

      I'm starting from scratch. I'm planning on using the amp from the original blast box, but everything else is up in the air.

      The tweeter grill isn't important to me. I can make a DIY grill. I was mainly leaning towards the ND25TA-4 1" Titanium Dome Neodymium Tweeter because of the great off-axis response. I'd be open to other tweeters if they have a good off-axis response as well. Since I'm playing downtown with listeners in every direction, a slightly better off-axis response is more important to me than a slightly better on-axis response.
      Last edited by Momma's Big Boy; 03-03-2022, 01:06 PM.

  • #4
    I was mostly leaning toward the DC28FT-8 or ND25FW-4 IF you needed it to reach ~106db instead of the original tweeter's ~101db...along with a more efficient and higher power-handling midwoofer like the DC130b-4. The grilled default tweeter has a tighter bunching-together of high-frequencies compared to almost anything else (including these two above mentions) but I'm not sure how noticeable the difference will be compared to the C2C distance and XO-frequency effects on high-mids/low-treble sounds at different extreme angles.
    That said, I don't think the original BlastBox you've heard has a particularly noteworthy C2C distance or low-frequency XO point, so I'm guessing the "it sounds suprisingly good at different angles" aspect is more compared to speakers that might have noticeably bad off-axis perfomance.? And with this version being your OWN design/build, you can keep tweeter+mid Center2Center-distance as close as possible instead of focusing on appearances or ease-of-CNC/milling.

    The midwoofer you're looking at leans more toward a 2-3liter ported design instead of a 1-2liter sealed design for its bass response...but you might be fine as-is simply with its higher overall response (mostly louder low-mids) along with your larger subwoofer and better batter/power-delivery letting the amplifier actually stretch its legs a little.
    It kind of depends on whether you're mostly looking for louder deep bass or louder low-mids which might be hard to pinpoint. I think an appropriately higher-voltage battery-pack should allow the amp to push the bass better and the 8" subwoofer should help the bass a lot, while the 4.5" midwoofer will let the overall volume increase a little, particularly the low-mids.

    The midwoofer and tweeters I mentioned near the top of this post could let the mids+highs reach louder by a noticeable amount, and I think the off-axis response could still be kept nice, BUT I don't know if the louder mids/highs would be overkill.
    I guess on the positive side, they're still about the same cost or less (the DC28FT-8 are currently on-sale for around $15) and they're really easy to work with, so it might mostly be a no-lose situation either way.
    Something like the DS135-8 or DC130b-4 midwoofer could reach deeper and louder in a small (1.5-2liter) sealed space, but they also want to cross a little lower (around 2-2.5khz I think) so the DC28FT tweeter's low FS and high XMAX might help for that.

    A different amplifier and a regular 2way stereo system might allow slightly more output at the expence of bass-depth, but I think your 2.1 setup might help keep the mids a little clearer and there's already plenty of potential for getting it louder if you want...and it sounds like you don't particularly want/need it overall louder anyway.

    Sorry for tangenting so hard at this. I'm trying to think of it from some slightly different angles, but I think you've already come from a pretty good starting point as-is..and you have a good idea of what you want.
    My first 2way build


    • Momma's Big Boy
      Momma's Big Boy commented
      Editing a comment
      Thanks so much for your detailed responses. I'm learning a ton right now and you're giving me a lot of good things to think about. Can you elaborate a bit more on the following?

      "The grilled default tweeter has a tighter bunching-together of high-frequencies compared to almost anything else (including these two above mentions) but I'm not sure how noticeable the difference will be compared to the C2C distance and XO-frequency effects on high-mids/low-treble sounds at different extreme angles."

      I don't know anything about how the C2C distance and XO-frequency affect sounds at different angles.

      The only decent speakers I've listened to are the C-Note speakers. That's what I'm using as a comparison for off-axis response. IMO, I was disappointed at the off-axis response of the C-Notes right away when I first listened to them (though the on-axis performance is great). And then when I listened to the Blast Box, I was immediately shocked at the off-axis response. It was night and day to me how much better it was than the C-Note in this regard.

      In terms of loudness, I don't need my boombox to be overall louder than the OG Blast Box. If I was using the OG BlastBox for playing, I probably wouldn't even turn it up past 60% volume. I don't want to be obnoxious with my volume. I've heard a lot of street performers who kill the mood by overpowering the area with sound. But I do want the better mid to low end response that I would get with larger midrange drivers.

  • #5
    Usually you'll want the woofer and tweeter to overlap in a nice way around the crossover so the resulting frequency-response is pretty flat.
    Click image for larger version  Name:	One.jpg Views:	0 Size:	38.3 KB ID:	1483657
    You'll see how both the tweeter(green) and woofer(red) are quieter around the crossover point, but they add together as long as their phasing is lined up pretty well (both are moving in/out at the same time as eachother instead of one moving out while the other is moving in).

    IF the phasing isn't lined up well, so one of the speakers is moving out while the other is moving in around the crossover frequencies, then you can end up with them cancelling frequencies out instead of adding them it can look more like this:
    Click image for larger version  Name:	two.jpg Views:	0 Size:	39.0 KB ID:	1483658
    Where the overall response can actually end up QUIETER than either speaker at the crossover point, because they're cancelling eachother out.
    There are a few ways this can happen:
    -You accidentally wired one of the speaker's +/- terminals you can simply switch them back around the other way.
    -The crossover design affects the phase and the XO design might line up poorly where it could need some tweaking (I'm still kind of new to this and don't have a good grasp of this aspect).
    -The physical distance forward/backward of the speakers isn't "time aligned" well.

    That last one is the important part here. Imagine the speaker-box is in two halves, so you can move the tweeter to a different place from the woofer. As long as you keep them the same distance from the listener AND the listener is far enough away from both for them to add together (instead of noticeably sounding like they're coming from different locations) then you can safely move them all around left/right/up/down, hypothetically...and phase-alignment should stay about the same.
    BUT if you move one of the speakers farther or closer to you, that'll affect the phase-alignment between them.
    Normally that's not a huge issue, because they're in the same box and you won't be moving the tweeter closer or farther away from you compared to the woofer...they're stuck at about the same distance inside the same box.
    BUT if you have them aiming at you while you're sitting and then you stand up, now the speaker at the top of the box is technically a little closer compared to the speaker at the bottom of the box.
    That difference is usually small, only a few inches, unless the speakers' Center2Center distance has them kind of far apart from eachother...then you'll suddenly have the top speaker several inches closer compared to the bottom speaker!

    This is why most speakers typically have the tweeter above/below the woofer instead of toward the side. It's pretty common for people to move side to side while walking around or sitting somewhere different, but people will typically only move up/down by a couple feet (sitting VS standing) so the difference there is usually much smaller.

    This distance/phasing effect becomes more noticeable at higher frequencies and gets more forgiving at lower frequencies, which is lucky because the speakers you'll typically have playing lower notes are usually too big to allow super close Center-to-center distances (unless you're using coaxial drivers where the smaller speaker is inside or in front of the larger woofer).

    This is usually only a slight issue, and only around the crossover point, and only when listeners are moving vertically compared to the speaker-box..So don't sweat it too much.
    It'll usually just result in a slight dip in the high-mids/low-treble response when you're listening from an unusual location.

    I think the Cnote's already have an impressively close C2C distance given the size of the woofer and tweeter frames, so I'm assuming the off-axis performance is focused by the tweeter's horn. I'm guessing its response is good out to ~40degrees or a little further (because the measurement graph shows it pretty nice) but maybe the high-frequency response really drops fast as you move a little farther off-center/off-axis?
    My first 2way build


    • #6
      The out-of-phase effect of distance changing between the tweeter and woofer as listeners move vertically is usually pretty small already.
      A closer center-to-center distance between the speakers being crossed to eachother can make this even less of an issue.
      A lower crossover point (within reason...crossing too low can cause tweeters and midwoofers to have more distortion from playing deeper than they want) can also make this even less of an issue.

      This is why you'll usually see woofer+mid+tweeter squeezed pretty close to eachother, and usually above/below eachother. It's an easy way to make a speaker a little more consistent-sounding and it'll also help it keep better vertical room-response which can be important if you're chasing perfection.
      This is also why you might see some speaker geeks cringe a little when seeing or talking about many cheaper 5.1 surround-sound systems where the center speaker has the tweeter to the side of the mids and the mids needlessly far apart from eachother. Same with some very old designs (or some newer designs that choose form over function) where the drivers will be placed on the front wherever they look nicest instead of where they'll likely pair best with eachother for the best sound.
      The differences aren't necessarily huge, but it's an easy way to get a slight improvement for free VIA good design.
      There might sometimes be niche situations where this isn't the best practice, so if an expert explains a different situation they aren't being crazy..and I still have a lot to learn.
      My first 2way build