LK Audio Mini Monitor Speakers (bookshelf)

by Legezimus

15K12410

Intro: LK Audio Mini Monitor Speakers (bookshelf)

So I had this like "adhoc"-idea on my vacation and decided to make these small computer speakers. I was tired of my old Creative computer speakers so I thought why not try to make something better. I had some components laying around for my future projects but I decided to use them on these small speakers. First I quickly drew a model with SketchUp to have some idea of the design and then I headed to the workshop.

Components:

  • 18x plywood pieces 25mmx150mmx150mm
  • 2x Dayton Audio PS95-8 Point Source Full Range speaker (3,5")
  • 2x Peerless passive radiator 830878 (3,5")
  • 1x Sure Electronics JAB2 2x50W digital amplifier with bluetooth 4.0 (and option to use batteries as well)
  • 2mm thick aluminium
  • cable terminals
  • on/off switch
  • 21V DC power source
  • miscellaneous amount of screws, cables and stuff

STEP 1: Design

As I did this project so quickly, I don't have specific plans yet. I'll add those here later. I did took one picture while designing the box with SketchUp, but the measurements are indicative.

STEP 2: Making a Router Jig and the Pieces

To have a nice look for the box I didn't use the ordinary method by just making the walls for each side. I wanted to have the layers of the plywood to be shown to make the box look nice, so I used a upper router to open up all the pieces (except the bottom and top layer).

You will need:

  • mdf/plywood etc.(for the jig)
  • band saw or jigsaw (making the jig)
  • upper router (for making the openings and recesses to the plywood pieces)
  • 18x plywood 25mmx150mmx150mm (9 for each speaker)

STEP 3: Cutting the Pieces and Gluing

I used a band saw to cut the pieces to the right size. Before cutting I marked all the pieces where to cut and also in which order they should be placed when glueing. At this stage I noticed that the wall thickness was way too small to mount the speakers, so I had to add small pieces of plywood inside. I recommend much thicker walls than I used (the thicker the better). After this I glued the pieces together, except the upper and bottom parts!

You will need:

  • band saw
  • wood glue

STEP 4: Cutting the Hole and Recess for the Aluminium Plate

I wanted to have an opening to the bottom of the speaker to have easy access for the electronics. I used a adjustable router jig for the recess and a jigsaw for the opening.

You will need:

  • adjustable jig (or make your own)
  • upper router (recess)
  • jigsaw (opening)

STEP 5: Sanding

After I had glued all the parts together (top and bottom pieces as well) it was time for sanding. As I didn't have like "specific" plans for the measurements, I just sanded the boxes to be as identical as possible. I measured the sides while sanding.

STEP 6: Cutting the Holes and Recesses for the Speakers and for the Small Aluminium Plate

Speaker holes

First I sawed open the speaker holes using a jigsaw. For the front speaker recesses I used two sided tape for securing the router jig (unfortunately no pic from the jig, but it was also made out of mdf ~16mm thick). I only made the recesses for the front speakers as the backside passive radiators did not need any. As you can see in the pictures the wall thickness was too small for the recess, but fortunately I managed to add the plywood plate inside and some filler to make it strong enough...

Aluminium terminal

I used Dremel to make the small hole and recess for the aluminium terminal. I also made the holes to the aluminium for the on/off switch, power input, volume control and aux input.

You will need:

  • jigsaw
  • upper router
  • dremel with router add on

STEP 7: Electronics and Testing

Last installations

The Sure Electronics amplifier is very easy to install. Basically you don't have to solder anything. I can add more pictures for the electronics later if necessary. Link for the amp: http://sure-electronics.net/JAB.pdf

At this stage I also installed the speaker cable terminals. The terminals are used for connecting the left speaker (or any other).

Testing

The sound is very clear without any adjustments, but in my opinion a bit too clear. So I used my computers EQ to tone down the treble a bit and added some bass. After these small adjustments, the sound is in my opinion very good! In a whole another level compared to the Creative speakers. I Highly recommend these components!

STEP 8: Finishing the Box

I'm still thinking how to finish the boxes. I also have to sand them smooth. I was thinking of using very light white stain and then satin varnish on top. I don't want to hide those layers too much. I will also probably 3d print a logo of my own to the speakers.

BTW one funny thing is that you can put the speakers on their sides as well and at least on my table they are directed quite good then to the listener. However this effects a bit negatively to the sound as they are quite close to the table then...

9 Comments

randing 1 year ago

Beautiful design and turnout.

annrrr 7 years ago

Really beautiful enclosure!

HighOrder 7 years ago

Very nice looking speakers. Can you tell me, there is a fair amount of mathematics associated with ensuring a speaker enclosure has the proper volume of space to support the speaker cone, power handling, etc. Did you use an online calcluator or other tool to determine the size of these enclosures? I wonder if some filler material (batting) might help with the "clarity" issue you noted (too much top end?). Really neat look though.

Legezimus 7 years ago

Thank you very much for
commenting! I did do some research and calculations beforehand. Basically my
aim was to use the recommended ported box size from parts-express.com (~3 litres)
but because I didn’t have quite the material to do that, the volume is a bit
smaller (~2,8 litres). As I also had the passive radiators, I decided to use
them to maximise the inner volume (porting takes a fair amount of space inside
the box if you tune it low). I also used some speaker box calculator tools to
ensure that no unwanted spikes to bass should occur (winisd and jeff bagby). Regarding
the filler material I do have the boxes filled about half. Other than that,
this was also like a trial for these speakers and for myself as I had not used
them before. :)

The box volume only
effects to the low end (bass) and shouldn’t have any effect to the higher end. Clarity
is just one property of the speaker itself. These speakers also work best right
next to the wall, at least in my opinion. I have also tried these with a subwoofer,
and can recommend using one if available!

seamster 7 years ago

These are some beautiful speakers. I love the clean look, and the ply layering is great. Nice work!

Legezimus 7 years ago

Thanks! Let's hope that the final finishing makes them look even better!

seamster 7 years ago

If they were mine, I'd go with no stain and a few coats of semi-gloss lacquer. But that's just me! ;)

Legezimus 7 years ago

Yeah, I have try different finishes to scrap pieces and decide then what to do... :)