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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.
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.
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.
|
