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Linkwitz Lab LXmini Speaker Build From Kit


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I am working on a build from kit of the very tiny, very amazing LXmini speaker from Madisound, designed by Siegfried Linkwitz of Linkwitz Lab (the woofer unit behind it in the picture is not part of that kit or this build). The LXmini were featured at each of the last three big audio shows I attended, and they are truly in a class by themselves when it comes to sonic bang for the buck.

I approached Madisound, the speaker kit and DIY audio supplier which has worked with Linkwitz to make a number of his designs available to the world, along with miniDSP and Siegfried Linkwitz, to see if they would be willing to sponsor a build, review, and evaluation sequence for the LXmini. They were all willing, and so the project is underway.

Siegfried Linkwitz has been designing speakers for many years. Now retired, he was an engineer for Hewlett Packard, and is the Linkwitz behind the Linkwitz-Riley crossover configuration popular with audiophiles.

The LXmini is about as innovative a speaker design as you will run across. The two-way design involves an upward-firing woofer mounted in the top of a length of common PVC plumbing pipe, and just above it is a full-range driver covering mid- and high-frequencies in a dipole configuration.

The combination of the arrangement of the drivers and the miniDSP 2x4 unit's response give a crossover at 700 Hz. The drivers are first-rate, carefully chosen drivers produced by SEAS.

The first time that I sat down to hear a pair of LXmini at RMAF a year ago, the show where “expensive,” “exotic,” “outrageous,” and “amazing” are descriptors that come to mind for much of what you see and hear, my thought was, “This will be interesting.” I was pretty much blown away by the reference-quality sound. The focus is on quality - the LXmini will not play super loud, but what they do, they do very, very well. I have been thinking about the possibility of building a pair ever since then.

Kit suppliers are, generally speaking, not big fans of reviews. They just do not know what to expect when they send out a kit for some unknown person to put together, what kind of problems they might run cross, mishaps that might get blamed on the design... too many unpredictables. I gave Adam at Madisound my assurances that he would be in the loop for the resolution of any and all issues and that I was experienced at building electronics and would have no problems getting the best sound from the speakers.


Generous Sponsors Of This Build/Review Project

Madisound - The complete kit, including wood parts but not the plumbing supplies, is available from Madisound. Madisound can supply the miniDSP 2x4 unit, in which case it comes pre-programmed. An optional wood parts kit is available.

Linkwitz Lab - The build instructions must be purchased separately from Siegfried Linkwitz of Linkwitz Lab. They include detailed instructions for fabricating the wood parts if you have woodworking skills and tools and choose to make them yourself.

miniDSP - The kit can be implemented with either the 2x4 or the 4x10 HD - with digital input and the option of 96 kHz sample rate - unit from miniDSP.


Go to the LXmini Performance Review


LXmini Build Video Series

LXmini Build Video, Part 1 of 4
LXmini Build Video, Part 2 of 4
LXmini Build Video, Part 3 of 4
LXmini Build Video, Part 4 of 4

Bill Of Materials

Goto the Final Bill Of Materials in Post #24.


Subwoofers Added

I added two JBL ES150P Subwoofers to my LXmini setup.

Goto the JBL ES150P Powered Subwoofer Review.
 

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Getting started...


The Madisound box, the miniDSP box, and the instructions PDF file, on a USB flash drive, emailed to me from Linkwitz Lab.



Here are the two 4-inch ID "Schedule 40" pieces of PVC pipe from the hardware store, each cut to 31" length. There was a more porous type of pipe construction also available, lighter weight, which could not handle water pressure. Tapping on it sounded more resonant, so I went with the more solid, heavier pipe, which only cost slightly more. The gentleman only charged me for 6 ft of pipe (I got 2" free!). I forgot that I needed the two lengths of 3-inch ID pipe for the smaller drivers, so went back to get two 5-inch lengths of that later. Both are "Schedule 40" - anyone know what that means?



This picture shows what all was in the Madisound box. Do not dispose of the Acousti-Stuff damping material in the bottom of the box. It might look like padding for shipping, or quilt batting, but it serves a much more important purpose.



The miniDSP 2x4 unit came separately from miniDSP for this build. If supplied by Madisound, it comes pre-programmed.



The Clay Couplers, these came from Amazon.



The pre-cut base plate from Madisound. If you are not an expert wood worker with all the tools, I suggest ordering the wood parts kit.



The wood piece that unites top and base of the unit. Again, very glad I asked for the wood parts kit. Top-quality CNC work throughout.



A bag of wood spacers & misc.



Two bags of screws.



Terminals and connection parts.



Rubber feet were also included for the bottom of the base plates, but I have a different solution, because my basement floors are not quite level.
 

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Schedule 40, it has to do with the thickness of the pipe's wall. Thicker is better, I did build a frame out of thinner stuff for my boats duck blind. Worked fine for that, but I would never trust it for actual plumbing.

Schedule 80 is thicker than 40.
 

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The PVC pipes are lightly sanded for and smooth paint adherence, then primed just to cover the black print, then the primed areas are re-sanded.




Paint: Got ahead of myself a little on the paint job (should be drilling holes next). The paint job plan is for, depending on the part:
  • white pipe or wood: white base / primed + black speckled + red speckled + navy blue speckled
  • black rubber: black base + white primer speckled + red speckled + navy blue speckled
  • metal parts: unfinished
  • black base cap: unfinished
  • white caulk bead around top of black base cap: unfinished




Hole marking and drilling took about 20 minutes. The PDF instruction file contains drawings with 1/8-inch grid so it is easy to figure out precise hole spacing.




With the help of guide bolts and "borrowed" pre-cut pads to soon be glued onto the smaller driver magnet assembly, the two spacer blocks and the driver mounting plate (C1 + C2, a single piece of wood in the Madisound kit) are glued together, then can be primed and painted.




Banana terminals are assembled onto the 4-inch pipe cap which will mount onto the base of the unit. A small screwdriver (you can see the red tip of its handle) is handy to help align each terminal as it is tightened down. Spade terminals are then tightened down with a second nut. I will solder directly to these terminals on the inside. I do not want to chance a connection pulling loose down inside the bottom of the unit. The base will be elevated enough with my leveling strategy to allow for locking banana connections on the bottom of each LXmini.




Pre-assembly check of clay coupler, driver mounting plate, spacers, and driver.




The three little spacer blocks will hold the small driver while it is clamped into place. It is mounted by having four machine screws clamp against the magnet assembly, or actually against the four supplied thin wood pads that will be glued to the magnet assembly of that driver.
 

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Hey Wayne, nice build thread. I know these must sound sweet for you to garner the interest to build a pair. Looks like you are doing a fine job. As far as extra mass for the base plate...it looks like a wooden plate. Is it on the flimsey side? Is it a sealed design? If so I could see some advantage to beefing it up. The cylinder design is inherantly the strongest, so maybe they are seeing a resonant decrease from the beefed up plate. Maybe?

Can you add the 3 links we would use to order all the parts?
 

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Got a bunch of painting done today, but not quite finished.

Had a minor setback due to the
METRIC hardware system!!:crying::help::hsd::scratch::thud::explode::eek:opssign:

Thought I had a pretty good grasp on such matters...:arrow::arrow::rolleyesno: As it turns out, not so much.

All straightened out now, however, thanks to the kind, patient personnel at Q P Ace Hardware at 3800 Old Cheney Rd, Suite B, Lincoln NE. They are THE BEST!:T

Tomorrow, quickly finish painting and complete assembly. I will try to have all the wiring done tonight so it goes together fast.

I have been editing the Build Video as I add pieces to it, so once the LXmini are up and running, the video will follow shortly.
 

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Continuing with the finishing steps, here is what the black speckled application looks like. The white speckled primer over the black clay coupler turned out particularly well. I think it was partly because the white primer has much better coverage than the other paint colors, so it turned out really white.

I am approaching the finishing steps as I imagine Miles Davis would have:
  • Don't overthink it.
  • There are no mistakes, only new directions in the theme.



And after adding the red.



And after adding the final navy blue.



The application of the navy blue came after a short nap turned into a long nap and I awoke to find it raining and dark outside. I applied the navy blue under those conditions, under artificial light and a light rain sprinkle. Channeling the spirit of Miles Davis on Apollo 13, I imagine he would have said something like, “Houston we have a minor variation on our flight theme, but we're just going to roll with it and see where it takes us.”

The final result will be a great sounding speaker - nothing at all haphazard about the sound - with a story of its own and a few rain-speckled marks in the finish for effect. When I discovered that the final finishing step was turning the bricks of our rear patio area just outside the back door dark blue, I suddenly realized I was done. Even Miles Davis knew when to call it a day.
 

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I was just reading a thread on the LXmini support forum. A couple of users are suggesting tightened bass performance by using heavier base material or adding increased weight to the base. I have a hunch that could be a good thing to try. Any thoughts?
Too late? Don't want to create a HazMat Zone, but what if there were some way to attach lead weights (like fishing sinkers) so they wouldn't rattle/vibrate?
 

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I remember reading about some acoutic mats for lining speakers. Do you think these might have the same effect lining the bottom of the tube? Might be an interesting comparison.
 

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Once I get them fired up, I am going to try with/without a couple of hand weights, just to hear if there is a difference, then take it from there. One guy had his LXmini base made out of marble.
Hand weights are a much better idea than mine. Sometimes I scare myself. :yikes:
Forgot to mention how much I like the rain-speckled finish. Nicely done!
Marble? That's nice, too. I imagine the intent (aesthetics and functionality) could be carried forward to real wood. And everyone knows there's only one variety that works best - the kind that comes from trees :rofl2:
 

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WHAT THE LXmini WILL SOON LOOK LIKE: (no time travel was used in the completion of this post)




Here is what the finish looked like after application of the final navy blue specked coat in light rain in the dark. It actually was not bad, considering. Other than a couple of raindrop splash marks, which added character, it was OK!




But in daylight I was not happy with the amount of navy blue applied, so I went and bought another can and darkened it a bit, just misting it on slowly from a distance... a VERY wasteful process, but it gave an excellent and satisfying result. This is the final result in full sunlight. Indoors, with less light, I like the way the red just barely glows through the navy.




Next the nuts for the screws to hold onto the magnet of the small driver were set in place using hot glue.




When the only color of hookup wire you have is green, guess what color you use? Green! I had decided to solder to the speaker terminals. The holes in the terminals were not very large, looks like they will take a 18 gauge (maybe 16 gauge) wire max. This is a stiff stranded wire that holds its shape nicely when squeezed into place on the terminal.




You can see the first of the wood spacers hot glued to the magnet of the small driver. When applied to the wood piece, the glue stayed soft. When pressed into place on the magnet, the glue cooled in just a second. If the placement was not quite perfect, it just twisted off, then the glue pealed off of the wood, and it was ready to try again.




The 14 gauge (I admit it was overkill, it was what I had available) wires were also to be soldered to the terminals at the bottom of the big tube. It is hard to get the tube back out of the end cap, and would be a lot harder with the layers of paint on the outside of the big tube, so I assumed the pressing of the tube into the end cap would be a one-way trip. The terminals accepted 14 gauge wire easily.




Soldering done on the small driver.




The small tube ready for the driver to be mounted.




Terminals soldered on the end cap that will be at the bottom of the 4" tube.




The supplied spacers (3) were an aid in getting the smaller driver properly placed in its tube. I had to watch alignment as the screws are tightened. With the tube standing on end, I pressed down on the rim of the driver to keep it firmly in place as the screws were gradually tightened in succession. When done, there was only about 1 turn's worth of clearance between the screw head and the body of the 3-inch diameter tube.




This glue bead would hold the clay coupler in the machined-out inset on the bottom of the large driver mounting plate. I had chosen white silicon for an accent elsewhere, clear silicon would have been MUCH better here.




The clay coupler glued in place.




The glue bead on the back of the LF driver rim, ready to mount on the mounting plate.




Some cleanup would be required!




Here was where I was about to discover how tacky the paint remained on the clay coupler! The cloth I was using to "protect" the finish was quite stuck. Luckily it could be pulled off without permanent damage to the finish.




Glue on the second LF driver, applied much more carefully. The mounting hole plugs were inserted first, then glue was applied to the INSIDE HALF of the rear of the driver rim.




The result needed almost NO cleanup.




The bottom of the base was painted royal blue. I had a can on hand and needed a way to get the edge of the MDF covered completely. Spraying down at the edge with the piece upside down on a plastic bucket accomplished this. Then the rest of the bottom was done with royal blue.




The top of the base after final navy blue "misting" application.




Rear view of the HF driver tube. Nuts for the two mounting bolts are held in place by hot glue.





The 4-inch end cap was then screwed to the base with sheet metal screws.




The 4-inch tube was pressed into the end cap.




The HF driver wire hole and wire. I found some black windshield silicon sealer that worked well to seal that hole and not show.




With the 4-inch tube inserted into the cap at the base of the unit, it was TIGHT. It will probably never come out. I am glad that I soldered to those terminals down there.




The Acoustistuff stuffing was divided into two equal amounts that would just fill the HF drive tubes to about 1 inch from the back. The rest was equally divided between the two LF driver tubes.




Each of the batches of Acoustistuff for the LF tubes was put into a mesh laundry bag so it could be easily inserted, adjusted, and removed.




All rolled up and ready to insert.




Inserting the Acoustistuff roll into the 4-inch tube.




The Acoustistuff roll has been pushed down into the 4-inch tube and adjusted by pushing and pulling for good vertical distribution.




The battery test tells you the polarity of the driver contacts and wires. Safe on these drivers because they are both full-range drivers.




LF driver assemblies ready for mounting on top of the 4-inch tubes.




HF driver unit all ready to mount, with the three spacer screws inserted to hold the 3-inch tube horizontal and 1/4 inch above the mounting surface. Make sure the two front screws are screwed in equally so the front of the unit does not look "twisted" left or right on the tube's axis when mounted.




LF driver assembly ready for mounting. I would only leave it upside down with weight on the driver roll for a few minutes at a time. The wires are generously long so the assembly can be set a couple of feet away from the 4-inch tube while hooking it up.




Mounting the LF driver assembly on top of the 4-inch tube was tricky. What finally worked best for me was tightening the clamp just enough that movement was difficult. Then with enough force the clay coupler could be moved to the right position and would stay there until the clamp could be fully tightened. I left off the upper hose clamp, which served no functional purpose.




The LF driver assembly mounted on top of the 4-inch tube.




The HF driver tube mounted on top of the LF driver assembly with 1/4-inch space between. The two bolts mated with the nuts that were held in place inside the tube by hot glue. Actually one of those nuts broke loose from the hot glue, but I held it in place while the bolt was screwed in a turn, then the hot glue setting held the nut from turning while the screw was tightened.




My decorative bead around the base of the LXmini. The reason I bought white silicon sealer. Right choice? I am happy.




Optional Dayton Audio spikes - these are the model DSS2-BK with black finish - can be joined to the M6 hardware with an M6 coupling nut.
 

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Here is what they look like.





I decided to leave the HF driver cable long and hanging in the back... call it a fashion statement.



Crossover Setup:
Knowing that the LXmini are volume limited by the LF driver, I had decided during the build to configure the crossover using a miniDSP 4x10 HD that has floated around HTS reviewers for awhile and was sitting ready for use. I got ahold of the 2x8 plugin with 96 kHz processing speed and manually copied the filter valued from the 2x4 preset into a 4-way crossover, creating four configurations:
  1. LXmini only, in its native configuration, crossed over at 700 Hz with LR 12 dB/oct.
  2. LXmini same as #1, plus crossed over at 200 Hz with LR 48 dB/oct, LF content run through neighboring full-range speakers.
  3. LXmini same as #2, plus crossed over at 60 Hz with LR 24 dB/oct to sub.
  4. LXmini same as #1, plus crossed over at 60 Hz with LR 24 dB/oct to sub.
Running pink noise test tracks, the frequency response was adjusted very quickly using the REW RTA function and only changing crossover section output levels. By "very quickly," I mean with laptop on my lap at the LP and the UMIK-1 mic hand held at arm's length to get a decent reading. The result is very flat clear out to about 15 kHz.

Initial Setup is fairly wide in my room with LP directly on the tweeter axis.

Impressions:
Just like I remembered. The imaging is so effortless and natural. The spacing is just a bit wide in my room, and the soundstage might be stretched a bit thin, but still fills the room. Think of the mid-tweeter as a "semi-dipole" with the Acousti-Stuf filling its tube. This brings the soundstage somewhat forward in the room and involves the room acoustics a bit less, but not as much to the degree that a horn design will usually do.

Note: Dennis Young - Tesserect - came over for a listen. I will let him post his own impressions, but it is worth noting that the setup was giving me a crystal clear center image and Dennis was getting a wider center image. We switched in and out of the LP several times trying to figure this out and never fully resolved it. I am taller and my head ends up a little higher, plus I tend to lean forward to get my head a few inches away from the chair back, these might have been factors. I expect the LXmini to be very forgiving of setup variations, but we will need to look into this farther for the main review coming up.

I LOVE the mid/tweeter, it is very dynamic and clean and just sparkles on so many tracks.

While configurations 1 and 4 give super-clear and focused image clarity clear down through the lower midrange and upper bass, config 3 could really CRANK out the volume by taking the LF load off of the woofer, with only a minor sacrifice in image clarity in the upper-bass range.

The extended HF response, with its smoothness and clarity, make the LXmini a serious contender as a mini reference speaker, just as Siegfried Linkwitz refers to it.

Much more to come. Stay tuned.
 
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