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3rutu5 Baby Boombox

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  • 3rutu5
    started a topic 3rutu5 Baby Boombox

    3rutu5 Baby Boombox

    Progress pictures of todays little experiment. First of all, this is a smaller version of the big Boombox, running 2* ND65-4 drivers and will be powered by a DTA-2 amp board. The enclosures have an internal volume of 0.065 cu.ft each. As my forsner bits are either too big or too small I've decided to use a vitamin container as a sleeve for the PVC port to sit in. I'm restriction in depth and will only be putting a 5inch length in each side. Should be tuned for 60hz but need to check what the newer larger volume gives me in WiniSD.

    Should have this finished in a.week, but thinking about a different paint scheme and might try my hand at a bit of stencil grafitti and go navy blues and whites ..

    I mounted the Peerless PR on the first run I did this morning and was a bit disappointed as Chris suggested these micro speakers might struggle to move such a chunky radiator. I used a cheap 2.1 eBay amp which I was equally disppointed.with when I bought it just to hear that it worked. So moving forward quickly cut another piece and did what you see now. I love the flush cut router bit with a bearing and some.double.sided tape, makes it a matching cut Everytime.

    The larger one is in the photo similar to the viral "banana for scale" times of.a.few years ago.
    ​​​​​​
    Attached Files

  • 3rutu5
    replied
    Originally posted by Chris Roemer View Post
    While I'm NOT eXactly sure what you've ended up with, what it LOOKs like to me is that while your ND65(s?) is(are) rolling off below around 120Hz, your TEBM is basically running full range.
    You've got a 4ohm driver in parallel w/an 8ohm driver (over most of the FR range) which is dropping your load to about 2 ohms ! ! (MOST amps would not take kindly to that.)
    You can SEE this on your Z-plot.

    To cure that, I'd swap your 2 coils around, putting the 2.5mH in series w/the TEBM and DROP the 4ohm resistor (that was in parallel w/the coil).
    THAT will roll off the TEBM around 1000Hz.
    THEN (for the ND65) I'd change the 250uF cap to a much smaller 20uF and add a 12ohm resistor out in front of it. (NOW you'll have the shunt coil be the 0.50 that you got off your "woofer".)
    I got quite adventurous with this an attempted it on my own and c#cked it up.

    I'm going to revisit this soon, just have a bit of family stuff going on at the moment.

    What's the view on using a LT circuit ilter to provide the boost at the lower end and run a smaller box? Appears to model nice in WiniSD

    Leave a comment:


  • Chris Roemer
    replied
    While I'm NOT eXactly sure what you've ended up with, what it LOOKs like to me is that while your ND65(s?) is(are) rolling off below around 120Hz, your TEBM is basically running full range.
    You've got a 4ohm driver in parallel w/an 8ohm driver (over most of the FR range) which is dropping your load to about 2 ohms ! ! (MOST amps would not take kindly to that.)
    You can SEE this on your Z-plot.

    To cure that, I'd swap your 2 coils around, putting the 2.5mH in series w/the TEBM and DROP the 4ohm resistor (that was in parallel w/the coil).
    THAT will roll off the TEBM around 1000Hz.
    THEN (for the ND65) I'd change the 250uF cap to a much smaller 20uF and add a 12ohm resistor out in front of it. (NOW you'll have the shunt coil be the 0.50 that you got off your "woofer".)

    Leave a comment:


  • 3rutu5
    replied
    This project was the first time I have ever used xsim, so just fiddled around with some parts I had ordered from previous salvage attempts trying to understand what things do what. Tom gave me a.good start for a high pass filter, which I added to after I changed direction for.the 3rd time.

    For.the high pass I used a 250uf Electrolytic cap (actually a 100 and 150uf) and shunted a IC182-5 2.5mH 18 AWG inductor, because I upped the cap to 250, it looked to line up with the TEBM around that 150hz mark. On the TEBM curve I used a LW18-50 0.50mH 18 AWG inductor and 4ohm resistor which lifted to upper end up closer to the ND65'S. I don't know if this was even right but the graphs looked ok, quite aware that this may been deemed weird or unconventional as it is a stereo amp with 1 channel on playing below 150hz.

    For a test we connected this build to my pc, used foobar with the home theater EQ setting (which is quite thump and recommend googling it if you use this prohram) and tried different music trying to.see what it could handle, then for giggles we tried the previous boombox build and the desktop speakers as they are fairly similar with their drivers and BSC etc. Results were interesting to the naked ear, with all 3 sounding different, the baby boomer in the middle for bass, nice and punchy and had some good deep notes, with the high a bit louder/bright, which was acceptable, the desktops handled bass extremely well , but in comparison the upper end wasn't as defined but still very playable. The origami boomer struggled a bit with the added EQ setting, which I'm wondering if that is linked to the 2*30 watt amp, not sure the TEBM65's like more than 15w's, which was what put me off the PE 2.1 HiFi amp as I put that driver on the 30w sub channel and it too started to distort a bit when cranked.

    What would I do differently if I had a time.machine.you may ask? Probably use the same ND65'S, but cross them with a pair of those DA TCP115's, I may have been able to.use a similar enclosure sizing and mount them on the rear

    Big thanks to Tomzarbo and Chris Roesner as usual, these poor chaps were generally my sounding board and having me constantly begging for advice., Neither were probably aware that I would go in a completely different direction, so don't blame them if there is thoughts that this is a stupid build, this was a creature of my own doing. I just think the guys on this forum need a shout out for being extremely approachable.
    Attached Files

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  • 3rutu5
    replied
    Ok, rushed in and finished it today, which is evident on the top panel, might try and fix it up later, but let's be honest I'm a bit over this project as it was the second attempt 😅..

    What I tried was the following

    ATTEMPT ONE

    DA DTA2 amp, 2*ND65-4's and a total volume of 0.14cu.ft (2 individual boxes)...result was distortion town, population me...

    ATTEMPT TWO

    ​​​​​PE 2.1 HiFi amp, 2*ND65-4's, 1*TEBM65C20F and approximately 0.18-0.2,cuft
    ...result was distortion of the TEBM65 and some weird pot noise on the amp.

    ATTEMPT THREE
    DTA-2 amp, 2*ND65-4's, 1*TEBM65C20F, difference was I put a high pass filter on one of the ND65'S and had a go at a crossover at 150hz with the TEBM65 and ND65. With all the components, capacitors, inductors and resistors it actually sounds pretty good. I'm sure it isn't conventional but to me sounds good, has the bass the other two lacked and is in a smallish enclosure, just wish I didn't rush the paint job

    Attached Files

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  • 3rutu5
    replied
    Had a change of direction, added a third driver, attempted a high pads and crossover and so far fairly happy with the sound (albeit having an open back and big hole in the top when tested)

    I felt that being 89% blue was a bit dull and I saw a old mustang with the twin pins, which made me think why not, not twins, but my take on it. Should have this finished by the weekend as it is all soldered up and all I'm really doing is painting.

    Leave a comment:


  • 3rutu5
    replied
    Hooked up the amp and had a listen before I swap out the other amp board I had, can say I was a little underwhelmed, the little speakers started to distort a little and no real bass, ran a test with the same volume on my TEBM build and the difference was like I was originally listing to a set of headphones standing a meter away. Might try a different amp and change the port length.

    Not sure if this is something to do with a 4,ohm driver, the BSC or something else....

    Leave a comment:


  • 3rutu5
    replied
    Had a go at making a cutting out a image template and using spray paint. Wired everything up and I think I busted the potentiometer and as soon as you touch it, either a speaker drops out or one distorts.....so guess I'm going to look into fixing or just replace the entire one with a KAB 215
    Attached Files

    Leave a comment:

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