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+title: I built speaker cabinets
+date: 2021-02-23 23:30
+tags: diy, audio
+---
+
+Yesterday I finished my build of the [Flat 5 speaker
+cabinets](https://www.oaudio.de/en/loudspeaker-diy/breitbandlautsprecher/flat-5.html),
+a transmission line speaker designed by Blue Planet Acoustic with a
+single Tang Band W5-2106 broad-band driver.
+
+## The BPA package
+
+After I had ordered one Flat 5 kit from Blue Planet Acoustic I waited.
+And waited.  And waited.  But nothing happened.  Aside from the
+initial order confirmation I had not received any other email.  I
+wrote them an email, to which I received no reply after several days.
+Worried that my order was forgotten (and the advance payment lost) I
+decided to call them.  When I finally got through I was surprised to
+be talking to a friendly person who informed me that my order was not
+processed because I had only ordered *one* kit, but to build a set of
+two speakers I would need *two* kits.
+
+Since the description on the order page isn't at all specific about
+the contents of the package, I assumed that I would get two matching
+drivers (approximately EUR 65 each), a bit of cheap damping material,
+and simple speaker terminals.  Turns out I was wrong and this variant
+of the Flat 5 design comes with a filter circuit, which inflates costs
+quite a bit due to the use of "audiophile" grade electric components.
+In my opinion, "audiophile" is a meaningless attribute.  I'm sure one
+can get an accurate inductor, capacitor, and a low-noise power
+resistor for less than what they charged me.
+
+I didn't want to cancel my order and the costs for an extra kit was
+within my budget, so I decided to order a second one.  I noted in my
+second order that this is meant to be an amendment to my previous
+order, and that I'd like them to drop the extra delivery fees.  They
+ignored my message and sent me the components.  I paid delivery twice.
+I probably won't be ordering from Blue Planet Acoustic again.
+
+The package came with the components and two A4 sheets of
+"instructions".  One sheet was the schematic of the filter circuit;
+the other sheet was a front and side drawing of the speaker cabinets.
+The drawing does not include any recommendations for placing the
+filter components, nor does it suggest the order of assembly.
+
+## Cabinet assembly
+
+This was my very first build of a speaker cabinet.  I wanted to reduce
+the likelihood of failure due to my lack of experience, so I decided
+to order pre-cut MDF boards from
+[speakercase.de](https://speakercase.de).  I don't own a router nor do
+I have any power tools other than a powered drill and a jigsaw, so
+cutting MDF boards and recessing the rim of the drivers would have
+been very messy and very frustrating.
+
+When the MDF boards finally arrived after about three weeks (they are
+made to order) I was pleasantly surprised to see how easy it was to
+put them together with [Lamello wooden
+biscuits](https://www.lamello.com/product/lamello-system-verbinder/original-holzlamelle/).
+It looked all so very easy, so I didn't pay enough attention when
+gluing things up, only to find out much later when attempting to put
+on the front that the order of assembly matters a lot.  There was no
+way to put on the front *after* the transmission line barriers had
+been glued to the back and the bottom and right side board had been
+fixed.  The presence of the barriers and the fact that the front and
+back board both have matching dados to hold the barriers meant that
+the front could only be lowered straight onto the barriers.  So I had
+to saw off the Lamellos that I had already glued into the side and
+bottom boards...
+
+Another surprise was how very *tight* the fit of the internal barrier
+boards and their slots in the front and back were.  Even though I used
+a precise square to make sure that the boards were glued perpendicular
+to the back I still had to remove quite a bit of material to ensure a
+flush fit of the front.  The result is far from perfect, but I'm sure
+that it won't be noticeable once I sand down the cabinets to apply a
+black wax finish.
+
+![Waiting for the glue to dry after sealing the second speaker cabinet](/images/posts/2021/flat5-almost-done.jpg)
+
+It was especially annoying to me that the assembly order suggested in
+the 2013/5 (August/September) issue of the *Klang & Ton* magazine does
+not apply to a build with Lamellos.  It's obvious in hindsight, but I
+still feel like there must be a better way to put the MDF boards
+together without leaving off four Lamellos for the front.
+
+## Wiring
+
+The kit from Blue Planet Acoustic included two sets of components for
+an RCL filter to attenuate an annoying frequency bump in the response
+of the broad-band driver.  The inductor was surprisingly large and
+heavy, so it took me a while to decide on a mounting place inside the
+cabinet; I eventually decided to glue the three dead-bug-soldered
+components to one of the transmission line barriers.
+
+![View on partially completed internal wiring](/images/posts/2021/flat5-wiring.jpg)
+
+The only difficulty was to solder the speaker wires to the banana
+panel jackets, which are excellent heat sinks.  It took a long time to
+heat them up enough for an acceptable solder joint.
+
+## Do they sound good?
+
+Yes.
+
+I connected the two speaker cabinets to a Yamaha A-S701 amplifier,
+though any decent amplifier would work just as well.  Jazz recordings
+such as the delightful *Mikarimba!* now have a surprising amount of
+clarity; the bass is tight and clear, there is no "boom", brush
+strokes evoke a visual response, cymbal strikes have crisp attack and
+are never harsh; double bass has just the right amount of snarl and
+body.  Other jazz records, no matter the era, simply sound great
+through these speakers.
+
+Chapman Stick recordings such as *Dream Recall* by Andy Salvanos sound
+delicate and fresh.  Listening to the influential *Friday Night in San
+Francisco* is an experience from which I could only escape with
+enormous effort.
+
+These speakers sound *great* at higher volumes.  They don't sound
+noisy.  I don't have the urge to lower the volume and I have yet to
+experience ear fatigue from listening to music with this setup.
+
+The first disappointment, however, came with the Dream Theater + Bruce
+Dickinson cover of *Perfect Strangers*.  It could be the fault of my
+copy, but I had to turn it off just a minute into the song.  The mix
+just felt too compressed, but I also think that the upper mids of the
+heavily distorted guitars and the compression in the higher
+frequencies (especially on cymbal hits) just became much more
+noticeable with these speakers.  I didn't mind the problems of this
+copy as much with my old Teufel soundbar (which was *okay* for the
+most part, but made everything sound kinda washed out and blurry,
+especially recordings of jazz ensembles).  I'll try to get a better
+copy and try again.
+
+Piano recordings (e.g. Chopin or Bach) sound good, but honestly I
+never find them *truly* exciting.  I can now hear the sound of the
+pedals and keys bottoming out, which definitely adds to the
+experience.  I wouldn't say that it sounds as if a piano was right in
+front of me, but perhaps this is because I don't really have memories
+to compare with.
+
+## Conclusion
+
+Despite the initial disappointment in ordering parts, this was a lot
+of fun.  It didn't take me too long to put everything together, and
+the result is a *vastly* improved aural experience for music that
+benefits from finer resolution.  I'm happy I built these speakers.