Updated 2009-09-14: Added some more information and cleaned things up a bit.
Continuous max SPL:
Est. build cost:
|Three-way, modular, partly active, high output design|
Huge floor stander
25 Hz-20 KHz (in-room)
95 dB / 2.83 V / 1 meter
120+ dB (pair, 1 meter, from 30 Hz)
800€ excl. amplification.
people find out that I build loudspeakers I often get asked if I can
build them some. I usually say no, because most people don't realize
how much work there is and how many things can go wrong in the process,
but this time I said yes because I'd get to do something I hadn't done
So this guy likes his music right. We're talking
mostly modern, main-stream music. But he likes it really loud. I mean
really, really loud. This meant they'd have to be big. I couldn't resist the challenge.
So Tempest was born.
started out looking for suitable woofers, taking extra notice of
efficiency, low Vas, low Qts and decent Xmax. I wanted a small box with
a high tuning frequency without boominess, but I didn't want to use
professional drivers. I eventually found the perfect driver in the
cheap German brand, Mivoc.
Burn-in before measurements.
is a twelve inch woofer with a painted paper cone built on an extremely
solid cast frame and with a strong motor. The excursion was plenty for
the job, as there would be a total of four of them, and they could be
fitted in small enclosures with their high Fs and low Vas. They are
more woofers than sub woofers, but that was exactly what I needed, sacrificing the very lowest bass for raw efficiency.
The sexy rear of the Mivoc AWM124. Unfortunately, the front isn't as hot.
next thing on the list was the tweeter. As I wanted these speakers to
produce well over 115 dB continuously, a standard 1" dome wouldn't
work. I knew from before that Monacor made a 30 mm dome tweeter that
could also be had with a large waveguide, so I started simulating
around this tweeter and pretty soon I settled with it because apart
from using large ribbons or compression drivers, it was the only
alternative. Not only does the tweeter have a lot of gain in the lower
treble from the waveguide (meaning less distortion), it also has a
significantly larger surface area compared to a standard dome.
The Monacor DT-300 with its waveguide. Screws not included.
took a while before I choose the mid woofers and I can't say there was
a lot of research behind the choice. They looked cool, seemed
well-built, could play the frequencies I wanted and they were
not expensive. That's loudspeaker design on a high level right
The Monacor SPH-170C with the carbon-fiber cones and the... well, that's it I guess.
decided pretty early on that the speakers would be modular and consist
of a middle part with the mid ranges and the tweeter, placed between
two equally sized woofer modules. I did this because building a big ass
speaker as one piece is so much of a hassle it's not even funny. Not
only transporting the huge MDF sheets to build the enclosure,
transporting the actual final speaker box up and down stairs several
times as you sand them, paint them, measure them and what not... It's just a pain in the ass.
So, externally, per speaker, three identical
sized boxes, two of them with a woofer each, one of them with two mids
and the tweeter.
After deciding on the woofers I
settled with the dimensions of 400x400x600 mm (width, depth, height)
meaning the whole tower, excluding any feet, would be 1.8 meters high.
The woofers would each get about 55 liters.
The woofer enclosures before gluing the bracing in place.
didn't go all the way with material thickness this time. The boxes were
built with only one layer of 19 mm MDF, but fairly effectively braced.
I tried to save some money here and the end result doesn't suffer from
The mid/tweeter modules with a pile of bracing.
the woofers, I planned a tuning frequency of a bit above 34 Hz, but it
ended up at 29 Hz because I didn't double check the ports I ordered.
But 29 works without any issues. You can tune at 33-34 and get a wee
bit of extra gain at 30 Hz, but anywhere around 30 is fine. If you use
a 90 mm inner-diameter port of 25 cm length, you will get the correct
tuning. Mine were a bit conical so the inner diameter was more around
80 mm, thus the lower tuning. But no harm done.
The mid woofers has
about 15 liters and in this application it doesn't really matter as
they are crossed above any potential enclosure gain. Just stuff their
enclosures with some heavy insulation to absorb the back wave as
much as possible. The chamber behind the tweeter can house the passive
crossover, or a kitten.
all the walls of the woofer boxes with about one inch thick acoustical
foam dampening material. I used some heavy stuff I got from work but
anything decent from ie. Parts express will do, as long as it is fairly
dense and heavy.
If you glue it against the walls (use lots of glue) the added mass will help reduce vibrations in the cabinet.
Also, one more thing regarding the
woofer enclosure. The frame of the woofer and the positioning of the
screw holes make it hard to use T-nuts on the rear of the baffle. I
skipped this and instead glued/screwed blocks of plywood to the rear of
the baffle to allow the usage of long wood screws to hold the driver.
Here's a pic that explains it better. (It worked out great.)
Glue plus two small countersunk screws from the front holds each plywood block.
only way to squeeze all the power out of these speakers is to cross
them by active means between the woofers and the mids. I did build an entirely
passive filter but it soaked up a lot of power and that is kind of
counter productive when you want to play loud. So I will not present it here.
So, first of
all you need an active 4th order LR HP/LP at 100-150 Hz. I recommend
the affordable Behringer CX2310 unless you have something better
already. The built in bass management in a surround receiver would
work, as well, but it might be hard to predict the end result as
manufacturers use different slopes and orders.
Giving the woofer modules a first test run... Mind blowing!
you need the amplifier for the woofers. If you don't have one already,
I recommend - on a budget - the Behringer Europower EP1500 (or EP2000)
which will provide each woofer driver with a comfortable 350 watts or
so. Ludicrous bass? No problem.
I assume here that your main amplifier will drive the mid/tweeters. But for that you need a passive crossover:
two mids are simply paralleled and all drivers are hooked up in phase.
To be on the safe side, use fairly high-power rated resistors. They
will be getting hot! All inductors are air-cored, and try to stay as
close to the ri-values as possible but a bit less or more is not
This simulation assumes an
bass/mid XO at 120 Hz but anywhere between 100-150 is fine, depending
on what sounds best in your setup and in your room. The wide baffles
support the mids down to around 150 Hz, meaning it is a good place to
crossover. The construction with the woofers near the floor AND
ceiling gives you quite a bit of gain, and placed near a corner, the
woofers will produce well over 100 dB from 2.83 V. Adjust levels
appropriately via your spanking CX2310.
frequency response is able to compete with any pure hi-fi speaker out
there, but will still beat all but few in raw SPL. This is at 2.83
volts and 1 meter. All drivers measured in-box, filter simulated with LSPCad. No room or boundary-gain! Advanced measurements confirmed it: kitchen chairs sound way better than any expensive stands.
Additional notesThe way I
set them up was with a main amp (a Harman/Hardon 3490 stereo receiver)
with pre-out and main-in. So I hooked up the pre-out to the CX2310, the
low-pass on to the Behringer Europower 1500, and the high-pass back to
the main-in. If you have a dedicated pre-amp you could get an additional
Europower 2500 and use that for the bass, and the 1500 for the
They are very affordable amplifiers and great value.
amps also come with a variable subsonic filter. You can choose too have
it off, at 30 Hz or at 50 Hz. If you intend to play really loud for
long periods I recommend to have it at 30 Hz. You'll not loose much at
all but the woofers will thank you for it. Below the tuning point they
have no air spring to help them from over excursion, so they can be
damaged from subsonic frequencies at high levels.
also need something to put between the boxes and against the floor. I
recommend soft feet, some sort of rubber pads or something more
specialized for audio. No spikes as they will make sure every beat will
reach straight into the floor with authority, and trust me, you don't
bass output, much more than I'd ever need and clean, strong and
effortless mids and highs. If you have ever been to a nightclub you
might have thought "Damn it's loud but the quality is horrible!". Well,
with these speakers you have the "loud" part but not the "horrible"
part. And I know I haven't been to any nightclub that could play 30 Hz
at 120 dB.
They won't win any design awards, but who cares?!
are not the kind of speakers I would use in my home, but if you have a
larger house, and have a room to spare, and no neighbors that hate
you, these are for you. Since they are modular, you could easily use
them for a serious home-theater system as well. Add more woofer modules if you
need them. Use the mid/tweeter module as center and surrounds. THX
reference levels? Not a problem. I assure you. Use the mid/tweeter
module in-wall? No problem either, don't even have to modify the
can honestly say that I had really fun trying these things out and the
raw force they can put out is just hard to imagine. At peak SPLs, I
actually almost fell over a few times when the bass notes hit. Without
exaggerating, you will loose your balance.
free to contact me if you are interested in building a HT setup based
around this project, or if you have any other questions!
"E-type has never sounded better..."