Announcement

Collapse
No announcement yet.

SB Acoustics monitors build

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • DeZZar
    replied
    Baffles glued on a couple coats of danish oil added for a little protection.
    Click image for larger version  Name:	IMG20210922154820.jpg Views:	0 Size:	669.3 KB ID:	1476523 Click image for larger version  Name:	IMG20210922153439.jpg Views:	0 Size:	408.3 KB ID:	1476521

    Ran the woofers in for a couple of hours and measured after cool down. For anyone curious, this is how my copies of the SB17NRX2C35-4 measure after a couple of hours break in:
    Param Spec Sheet 2Hr Break In % Variance
    Qes 0.41 0.501 +22%
    Qms 4.49 4.551 +1%
    Qts 0.37 0.451 +22%
    Fs 36 39.67 +10%
    Vas 27.6 25.21 -9%
    Mms 13.9 13.9 0%
    Cms 1.4 1.154 -18%
    Rms 0.7 0.76389 +9%
    Re 3.1 3.124 +1%
    BL 4.9 4.65 -5%
    F3 (Hz) 43.6 45.5 +4%

    This is actually very good as I know from previous tests that Qes, Qms and Fs will all continue to drop out to around 24 hours break in. Vas will remain about the same.

    This means the box tuning can remain the same as designed. It will yield a slightly higher f3 for now but this will settle closer to the intended f3 as the drivers continue to break in with use.

    So onto port tuning. Initial test showed tuning was around 34hz. Target is 41, and I did leave the port a little long to start with. However, I also suspect the compound elbow in the port (on top of the fact its never usually what the software says) will play a part in the final length. I took a hacksaw to the port and chopped some off and it looks like we need to loose around 60mm to hit 41hz. Just printing a new elbow now to suit the new dimensions.
    Click image for larger version  Name:	Port Tuning.PNG Views:	0 Size:	41.8 KB ID:	1476525

    Here's a couple of shots with the drivers bolted in during port testing.
    Click image for larger version  Name:	IMG20210923160423.jpg Views:	0 Size:	444.7 KB ID:	1476522 Click image for larger version  Name:	IMG20210923160515.jpg Views:	0 Size:	528.2 KB ID:	1476524

    Leave a comment:


  • DeZZar
    replied
    Originally posted by danmarx View Post
    As far as my router job, some tape over the baffle definitely would have prevented the rings.
    It depends on the surface finish - I've had the tape start to roll up under the jig as its turning causing other issues and even with a smooth base I've had chips get caught and scratch the surface anyway - I try and make sure all the routing is out of the way as early as possible in the process well before any finishing. But - re-routing existing speakers will always be a bit of a challenge. A CNC would solve that! :P

    Leave a comment:


  • danmarx
    replied
    The 3D printed sanding wheel was a great idea! I wouldn't have thought of that. Nice job, the fit looks perfect. As far as my router job, some tape over the baffle definitely would have prevented the rings. Also, making sure the screws on my Jasper jig were sub-flush would have helped as well. I refinished the whole speaker in the end any way. This build is looking great though. Can't wait to see some measurements.

    Leave a comment:


  • mattk
    replied
    Originally posted by Castlesteve1 View Post
    This is a great thread. Using the printer to make a sanding wheel was genius. Really nice work.
    I've done something similar in the past with a piece of plywood I cut to the right diameter.

    Leave a comment:


  • scottvalentin
    replied
    Wow excellent work and that veneer is VERY nice looking. Thanks for sharing the process, nice job on the sanding wheel.

    Leave a comment:


  • Castlesteve1
    replied
    This is a great thread. Using the printer to make a sanding wheel was genius. Really nice work.

    Leave a comment:


  • DeZZar
    replied
    Driver cutouts completed as well...
    Click image for larger version

Name:	IMG20210920192925.jpg
Views:	603
Size:	732.2 KB
ID:	1476323

    And a quick test fit...
    Click image for larger version

Name:	IMG20210920193226.jpg
Views:	597
Size:	668.0 KB
ID:	1476325

    Here's the tweeter face in position. Just holding it with my fingers but when you line it up correctly it sits perfectly on the woofer without any gaps! Happy with that :D

    Just need to repair that tiny little point of wood between the drivers that chipped off during routing despite being taped etc :'( (booo!)
    Click image for larger version

Name:	IMG20210920193256.jpg
Views:	592
Size:	583.9 KB
ID:	1476324

    So now these baffles will get glues down in place onto the boxes. They are slightly oversize to allow for trimming - and once trimmed I'll give them a round over before final sanding. Then I can clean the workshop up and move onto fine tuning the port and taking measurements!!

    Leave a comment:


  • DeZZar
    replied
    Thanks for all the suggestions. I ended up trying the print and sand method and I think it turned out ok.

    I printed a little plastic wheel the same size as the woofer and stuck sandpaper to it.
    Click image for larger version

Name:	IMG20210920175329.jpg
Views:	610
Size:	573.1 KB
ID:	1476318

    Then carefully positioned and scribed a line on the face of the tweeter. Put the sanding wheel in the drill press and slowly sanded up to the scribe line. It did a really good job - I didnt need to cut any material away beforehand.
    Click image for larger version

Name:	IMG20210920193128.jpg
Views:	599
Size:	794.9 KB
ID:	1476319

    Boxes are now all lined with a layer of felt and acoustic foam.
    Click image for larger version

Name:	IMG20210920192854.jpg
Views:	594
Size:	445.4 KB
ID:	1476320 Click image for larger version

Name:	IMG20210920192916.jpg
Views:	593
Size:	384.9 KB
ID:	1476321

    Leave a comment:


  • Wolf
    replied
    If you don't want to fight circular scratches, apply a layer of painter's tape over the baffle, or even contact paper to keep this at bay.
    Wolf

    Leave a comment:


  • danmarx
    replied
    I have never trimmed a tweeter faceplate but I have considered doing it often times but always chickened out in the end. If I were to do it however, I would probably opt for Wolf's method, where you basically install the tweeter and re-router the woofer. You could probably actually do this on a sacrificial baffle and just make sure to keep the center-to-center distances the same. Or if you did this in the actual enclosure, you'll have to create a central point for your router jig. Basically what Wolf was saying. I have done this, not to overlap a tweeter, but to flush mount a new pair of drives in an existing enclosure. I attached small blocks to a piece of MDF and glue it to the backside of the baffle, thus providing the crucial pivot point. From there routing is normal. Remove the blocks when complete. See pics below. This is just an example, not saying it's the best way to do it though!

    Click image for larger version

Name:	newspeakers (20).jpg
Views:	676
Size:	241.7 KB
ID:	1476275 Click image for larger version

Name:	newspeakers (21).jpg
Views:	673
Size:	236.9 KB
ID:	1476276

    Leave a comment:


  • Wolf
    replied

    People have taped over the tweeter, or removed the faceplate, and just recut the woofer recess dimensions. Since you don't have a central pivot, you could install one in the driver mount holes from the rear, and locate center, and recut.

    If you happen to have a spare tweeter face, or can print one, you can use that as a sacrificial template, and just pattern to the tweeter face.

    Later,
    Wolf

    Leave a comment:


  • Wolf
    commented on 's reply
    Just don't mention the WAR!

  • DeZZar
    commented on 's reply
    Yeah destined for a desk/shelf otherwise I might have ported out the back instead!

  • DeZZar
    replied
    I didn't quite get to spend the time on these today as I would have liked but regardless some progress on the baffles.

    I'm finding the solid oak a little challenging to work with - routing it is fear inducing as it splinters very easily and has a really interesting mix of hard/soft(er) wood through the growth rings - I think a two flute straight cut bit isn't the best and causes a lot of chatter. I'll have to hunt down some spiral or compression straight cut bits I think. Anyway after taking it real slow making multiple passes with shallower cuts the cutouts for the drivers are taking shape.

    Happy with that fit :D
    Click image for larger version  Name:	IMG20210919201723.jpg Views:	7 Size:	449.1 KB ID:	1476260

    I don't know why I keep punishing myself with these extra little challenges but in a moment of creative flow I decided to overlap the drivers just a little which requires the face plate of the tweeter to be trimmed.
    Click image for larger version  Name:	IMG20210919201617.jpg Views:	8 Size:	751.7 KB ID:	1476261

    I'm curious if anyone else has done this before and how you did it?

    Personally after thinking about it for a while I've opted for printing a custom sanding wheel. That is, a plastic wheel the same diameter as the woofer that I can stick a strip of sand paper to. I'll Dremel rough cut first and then attach the sanding wheel to either a hand drill or the drill press to sand the final dimensions.

    Here's the target look anyway. Just need to finish the cutout for the port flare tomorrow.
    Click image for larger version  Name:	IMG20210919201550.jpg Views:	8 Size:	730.1 KB ID:	1476262
    Last edited by DeZZar; 09-19-2021, 08:29 AM.

    Leave a comment:


  • DeZZar
    replied
    Originally posted by uncola View Post
    Wow great build process pics, DeZZar. are you going to design your own crossover too?
    Thank you!

    Yeah I'll be designing the crossover for these from scratch - I'll post progress on that as well as soon as I get some measurements for the drivers in the boxes!

    Leave a comment:

Working...
X