Jenzen
SEAS-ER
Copyright 2024 © Troels Gravesen
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DRIVERS CROSSOVER CABINET WORKSHOP PICS MEASUREMENTS SPEAKER-KIT CROSSOVER LAYOUT
5th Oct 2020: As
nobody builds the version with the CA18RNX middriver, this version has
been discontinued, so now only the ER18RNX.
The first speaker in the Jenzen series comes
with modest priced drivers, yet delivers a significant soundstage. Size
matters and using drivers with a decent membrane area means they don't
have to move much. In particular for the midrange this is important and
releasing it of the tedious task of pumping bass, things start
developing. Drivers we may have found having a harsh upper mid in the
common two-way set-up may all of a sudden deliver crystal clear sound in
all of the midrange.
The Jenzen series of speakers are meant to offer high-end sound for
low-end price, even for the constructions to come with expensive
drivers. As discussed in Speakers' Corner; what diy people can do
speaker manufacturers cannot, is this: Spoil our drivers with the best
of cabinet work. MDF is cheap and it's no problem making 30-50 mm panels
and adding solid bracing to produce low-resonance enclosure that is
often a significant part of high-priced speakers. I recall Eggleston
speakers, and the knuckle tap test suggests a solid log of wood. No
problem. Laminate 2 x 22 MDF; add bracing and we have the same thing.
And it pays off. Cabinet resonances add more to the sound than we may
think.
We may think commercial speakers are overprized - and some are - but
making a living from manufacturing speakers is not an easy task despite
having drivers and crossover components at less than half price compared
to what we pay retail. As diy'ers we only have ourselves on the payroll,
no packing and shipping, no dealers' profit, no advertising, etc. If
production price is 10-20% of retail price we may have a viable
business, hence the price of a single cap or added bracing may prove
pivotal for competitiveness.
The drivers for SEAS ER come for less than 700 USD ( @ Madisound; we in
Europe have to face some ~20% value added tax) and if you have the time
and skills to make cabinets, you're in for a treat for a fraction of
what a similar commercial speaker will cost. Without blushing I dare say
the finished speakers will compare to commercial speakers in the 10-20
kUSD range. But you have to be prepared for quite some woodwork. These
four cabs won't emerge from a couple of weekends' late night hours.
With the ER18RNX, SEAS is back into hard
pressed paper cones, not seen since the Excel W21EX001. This ER18RNX
cone is or has been added some reed pulp, usually used for water reed
roofs.
The sound from this hard pressed reed/paper pulp cone midrange driver is
good, really good. It has the clarity of magnesium, only comes with
better sensitivity and frequency response, which makes crossover work
easy. This driver appears to be a serious contender to the Peerless
Nomex (830875) drivers when it comes to uncolored midrange presentation.
Generally, if you think a 50-80 USD driver cannot deliver detail, try
one of these two drivers.
Bass driver CA26RFX features a standard coated paper cone, rubber
surround, huge magnet and healthy 90 dB sensitivity. As always from
SEAS: Well built.
For tweeter I could have chosen one from the
PRESTIGE range, but finally decided on the EXCEL
T25C003/T25CF001. This tweeter comes with excellent build quality and it
doesn't add much in overall building cost. Due to low slope crossovers
it may prove beneficial to use the T25CF001 having ferrofluid in
magnetic gap.
The crossover features the simplest possible LR2 filter and for proper
integration of amplitude and phase the middriver is 19 mm in front of
the tweeter. The significance of this is noticeable, in particular on
vocal performances and e.g. acoustic instruments like flute, oboe and
piano. Furthermore the edgy snappiness of high-frequency transients is
reduced for a more ear-friendly presentation with enhanced sense of
depth and spaciousness.
Quality of crossover components is a vital part of any multi-speaker
design. Unfortunately super caps are expensive and we need a lot of
microfarad for the midrange to make the high-pass section. The 3 x 33 uF
STANDARD Z-CAPs chosen here for the midrange deliver most of it, but
Superior Z are better although comes at a price. I had really good
results from STANDARD Z-caps for mid and a Silver Z-cap for the tweeter.
It's my experience that a parallel of many smaller caps of same value
makes better sound compared to a single 100 uF cap, but the choice is
yours. By-passing a large lesser quality cap with a small one of better
quality is not my cup of tea. It makes a blend of two transfer
characteristics and not always for the better, but opinions on this vary
considerably.
The present construction is designed to deliver with later up-grades.
The mid's reed paper cone can deliver the goods should you at a later
stage decide to up-grade e.g. midrange series capacitors. You can also
use the W18NX001 driver for mid without changing the crossover.
You may choose to immediately replace the
tweeter 4.7 uF STANDARD Z-CAP capacitor with Superior Z-cap or Silver
Z-cap, the latter I found had a really good synergy with the STANDARD
Z-caps. I can't help pointing to a 3-Way Classic builder
here,
who chose modest priced drivers and the best of crossover components.
Well done to my thinking. Too often we see people buying expensive
drivers and modest crossover components. The caps are of more importance
than the coils and a 10 mH air-cored coil for the bass is a waste of
money - if you can find one with suitable low resistance. If you want to
up-grade here, use e.g. Jantzen C-Coils.
Basics:
3-driver speaker.
Dimensions: 32 x 48 x 118 cm, WxDxH.
System sensitivity: 89 dB/2.8V/1 meter.
Impedance: 4-8 Ohms.
Power requirement: 50+ watts/channel.
Useful links (Please
follow all links before e-mailing!):
http://www.troelsgravesen.dk/tips.htm
http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/LCR-RC.htm
http://www.troelsgravesen.dk/Inverted-Polarity.htm
http://www.troelsgravesen.dk/choices.htm
http://www.troelsgravesen.dk/Placement-of-ports.htm
Download specs here:
Download driver specs for CA26RFX ER18RNX T25C003 / T25CF001
The sound:
Yes, I'm going to write a little about the
sound, something I really hate, because what I hear is not what you will
hear. Nevertheless: This speaker delivers tonnes of detail. I can't help
putting this first, because the mid-tweeter integration works so good
that it will provide a rare insight to your recordings and it also tells
good from bad, albeit not in any aggressive way.
Due to the stepped baffle and simple
low-order crossover it handles vocals really well and
Siri's Killer Note
is no problem. Female opera singers? No problem. As my JungSon was
occupied elsewhere I connected the speakers (in my workshop) to my 8 wpc
300B amp and I was surprised to hear loud it could actually play. Louder
than my wife usually plays, but this flea-powered amp is not what I'll
recommend despite the magnificent midrange. Feed it 30-50 watts PP if it
has to be valves, or 50-100 watts solid state; really good solid state
that is. My
JungSon
does well here, but....
It's a never ending
topic how much power is needed for a given speaker. The short answer is
that it depends on how loud you play. The CD above is Ulf Wakenius:
"Forever you". This is an analog recording (2007) and you can even hear
a faint tape hizz from the recording. Very little compression is used -
if any. Apart from liking the music, I use this CD to test my speakers
for loose wires or whatever. It comes with tremendous dynamics and will
make anything capable of rattling - rattle. It also makes a litmus test
on your amp's capability of handling severe transients and playing this
CD really loud it could make even the Jungson start clipping! And this
not at a level where the drivers would suffer serious risk of damage.
Two things: This speaker can handle a lot of power and if you're a head
banger, prepare for some 100 watts minimum solid state amp.
Bass is tight and surprisingly dynamic and
kick drum comes through really well, much better than anticipated I have
to say, and speaking of drums, the whole drum kit comes through with all
the speed and agility I could ask for.
The Jenzen speakers are fairly big, not only
physically, but also in the overall soundstage it provides. When dealing
with large speakers, take care of your hearing, because it can play loud
with low distortion and we tend to crank up volume when possible.
Evaluation was done with STANDARD-Z-caps to
the midrange and a Silver-Z to the tweeter. With STANDARD-Z to the
tweeter some details are gone and upper mid and treble appears a bit
more compressed, all in accordance with standard polyprop performance.
Good caps make listening easier and we can better sort out details, room
reverberation seems more clear and e.g. applause from an audience all of
a sudden sounds like clapping rather than just noise. Hand clapping is a
terribly good test on capacitor's ability to transmit complex
information without smearing detail.
FAQs having
the answer NO:
Can I make the cabs with a plane front panel?
Can I use a cheaper tweeter, like 27TFFC or 27TDC? Can I use any other
than the specified drivers? Can I change the cab dimensions without
impairing performance? Do you have more detailed drawings? Do you have a
suggestion for an active version? Can I tilt the cabs? Do you know when
the NEXT and further versions will be ready? Do you know how the vented
version sounds compared to TL? Will Jenzen ER replace your DTQWTs? Will
there be any clean 1st order filter Jenzens*? Will there be a version
with magnesium drivers?
*1st order filters may be nice but don't handle power very well. To my
mind we need a 4-way speakers to realise true 1st order filters and we
need driver being linear some two octaves below and above point of
crossover. True 1st order filters a prone to become extremely complex as
we need to linearise drivers' response and this speaker was made to be
simple with as few crossover components as possible without sacrificing
performance. 1st order filters are not just a coil and a cap! I've tried
modelling a 1st order filter and the mid has to be some 5-6 dB below
system sensitivity (8 ohms series resistor!) and the bass and tweeter
cross only 12 dB down at 1 kHz! We need a middriver with really low
efficiency to make this work - technically. Or we should use a dedicated
subwoofer and let the middriver go below 80-100 Hz. No wonder
Vandersteen speakers are seriously inefficient (~85 dB).
FAQs having the answer YES:
Can I use 22 or 25 mm MDF? (Keep outer
dimensions, front panel layout and 19 mm for the mid's outer panel). Can
I use the W18NX001 nextel driver for mid without changing the crossover?
Can I use a single rectangular vent for the midrange transmission line,
like 20 x 150 mm in replacement of the 4 x 30 mm holes?
Just in case you may be wondering what
R2042 and C2041 do across middriver's series coil.
This RC circuit is of vital importance for
making a smooth rool-off. So don't leave it out.
Cabinets can be made as transmission line or bass-reflex.
Obviously you can use
22 mm MDF in replacement of the Baltic birch used here and if you think
all this transmission line stuff is just a bit too weird - and it does
admittedly add to the overall volume - you can make a vented version
instead.
If you remove the bass cab transmission line
panels you have a net volume of 78 litres. This makes a nice F3 of 35
Hz. Port tuning = 32 Hz. Port = 100 mm (ID) x 155 mm length.
If you cut depth to 360 mm (depth without
front panel) you get 65 litres and F3 = 38 Hz. Maintain port tuning of
32 Hz and port is now 100 x 197 mm.
With this new cabinet depth for midrange -
and by removing internal panels - we have around 25 litres minus volume
of tweeter cab and bracings. This fits the ER18 well and I suggest
adding a port to the rear of 50 mm (ID) x 75 mm. Stuff the port lightly
with damping material to make an aperiodic tuning. The port leaves you
the options of vented, aperiodic and closed box (the latter by stuffing
the port hard).
Jantzen Audio ports: For bass cab: 2 pcs 100
mm (ID) x 200 mm, item #900029. For mid cab: 2 pcs 50 mm (ID) x 145 mm,
item #900023. Cut to required length for mid and for bass if you choose
the large vented option.
If you do so, add two braces to the bass
cabinet and one brace to the mid cab. Please check other files for how
this can be made, e.g
QUATTRO
cabs.
Regardless of your choice, maintain front
panel dimensions, driver layout and front panel chamfering. This is of
vital importance of how the crossover performs. The middriver front
panel provides an unusual flat response from the 4 drivers tested so
far. View at bottom of page how CA18RLY, CA18RNX, ER18RNX and W18NX001
perform. There will not be a version with the CA18RLY.
For the vented version damp bass cabinet with
8 mm felt internal panels plus 30 mm acoustilux on top and 2 layers on
bottom and right behind bass driver.
For mid use 8 mm
grey felt on all panels and 30 mm acoustilux in lower cavity (25 x 50 cm
folded) and behind midbass driver, same dimensions. Check damping
materials
here.
A few comments on
MEASUREMENTS before you start interpreting the readings below.
First of all, if we think measurements will
tell us how a speaker sounds, we're wrong. The perception of sound is
way too subjective to be reflected in any measurements we can perform. A
loudspeaker system is meant to give us a satisfying idea of an acoustic
event and for some people a pair of 5 USD ear-plugs are enough, others
spend 200 kUSD on a truly full-range pair of speakers - and the latter
may not be happier than the former.
Measurements may give us an idea of tonal balance of a system, i.e. too
much or too little energy in certain areas, although dispersion
characteristics play a vital role here. A two-way 7+1 and a three-way
7+4+1 may display similar horizontal dispersion, yet sound very
different. Measurements may tell us about bass extension if far-field
measurements are merged with near-field measurements. In addition to
this, ports may contribute to bass extension. Most of we diy'ers do not
have access to an anechoic room for full-range measurements from
20-20000 Hz.
What cannot be seen is what kind of bass performance we get in a given
room. Bass performance is highly dependent on in-room placement of your
speaker and the same speaker can be boomy in one place and lean in
another. Actual SPL level at 1 meter distance and 2.8V input is useful
for en estimate of system sensitivity and combined with the impedance
profile may give an idea of how powerful an amplifier is needed to drive
the speaker to adequate levels.
What measurements do not tell is the very sound of the speaker unless
displaying serious linear distortion. The level of transparency, the
ability to resolve micro-details, the "speed" of the bass, etc., cannot
be derived from these data. Distortion measurements rarely tell much
unless seriously bad, and most modern drivers display low distortion
within their specified operating range.
Many people put way too much into these graphs and my comments here are
only meant as warning against over-interpretation. There are more to
good sound than what can be extracted from a few graphs. Every graph
needs interpretation in terms of what it means sonically and how it
impacts our choice of mating drivers, cabinet and crossover design.
What measurements certainly do not tell is the sonic signature of the
speaker, because speaker cones made from polypropylene, aluminum,
Kevlar, paper, glass fiber, carbon fiber, magnesium, ceramics or even
diamonds all have their way of adding spices to the stew. Nor do
measurements tell what impact the quality of the crossover components
add to the sound, from state of the art components to the cheapest of
coils and caps, they all measure the same if values are correct, yet
sound very different.
Left: SPL @ 0.5 meter between M and T,
normalised for 2.8V, 1 meter. Overall system sensitivity = 88-89
dB/2.8V.
Right: Response merged @ 250 Hz with bass
nearfield response. Port response not included.
Left: Tweeter attenuation from R1011 being
1R5, 2R2, 2R8 and 3R3 respectively. 1R5 is too little to my ears.
Right: Step response displaying positive
polarity of tweeter & bass and negative polarity of middriver.
Left: Left and right speaker. Right: Final system impedance. Minimum around 6 ohms.
Left: Just to show two points of crossover
between bass and mid. I wanted the midrange to go as low as possible,
because the ER18RNX can go low here and ended
up with just below 200 Hz (red/blue). Nearfield response of drivers
shown.
Right: Point of crossover between mid and
tweeter is around 2.7 kHz. Pay notice to smooth roll-off from both
tweeter and mid.
Disregard shown bass level at 60-300 Hz. This
very much depends on where we merge nearfield and farfield readings.
Usually
we do this at 250-300 Hz where the farfield
reading is highly unreliable.
To configure a DIY kit and get a
written offer including shipping cost, please use the DIY kit
configurator in the Jantzen Audio website:
https://jantzen-audio.com/diy-kits/
All technical questions to troels.gravesen@hotmail.com
CROSSOVER-LAYOUT
BACK TO INDEX
Check this out before start making crossovers:
http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS
Also please read this:
http://www.troelsgravesen.dk/LCR-RC.htm
Click image to view large.
As the crossover is
going to be placed at the bottom of the bass cab, we have lots of space
and you may increase board size to later accommodate Superior Z-caps,
wax coils or whatever.
If you choose e.g. Superior Z-caps for mid
you have to increase height of the speaker base by e.g 15 mm. These caps
come with quite a diameter. Use an e.g. 8-10 mm slant of plywood for the
crossover. Also consider height of base if wax-coils are used.
You can obviously separate the bass and
mid/tweeter sections and run bi-wiring/bi-amping as I have done.
Kit crossover parts, here with added
Silver Z-caps and silver plated copper/teflon cables.
Click image to view large.
Click images to view large.
As can be seen from photos, bass and
mid/tweeter sections are separated for the sake of bi-wiring.
I also used 2 x 5R6 in parallel in
replacement of R2021 (2R7) as I intend to play loud from time to time.
These resistors take some heat.
Terminals blocks mounted with connections
from bass cab to mid-tweeter cab.
For once: Lots of space for crossover. The
crossover board is 23 x 27 cm leaving space for super caps as can be
seen below.
These cabs are going to see multiple speaker
drivers and flexibility is important.
Left: Trying out space for super caps. These
4 x 22 uF are huge!
Right: Fully mounted crossover. I made a loop
from mid/tweeter wires to allow future experiments.
The Jenzen MT baffle
Back to top
Below the response of 6" drivers I have at
hand over the last year. I'm pleased with the performance of the Jenzen
baffle as all of these response profiles allow simple crossovers to be
made. In particular the W18NX001 is smooth as ever and even the
ScanSpeak 18WU performs very well.
Reason for showing these files is to
demonstrate it pays off spending time on proper front panels in order to
provide the best possible acoustic support for the driver. As can be
seen, this makes crossover construction easy - and cheaper! You may have
specific ideas on how your speakers are going to look and I have a lot
of suggestions on fancy cabinet designs and if I think it will work OK.
I can't tell. Only measurements can tell although experience tells me
some of these people building their dream speaker will have a hell of a
time making the crossover, simply because design came first and
acoustics second.
Left: CA18RLY. Right: CA18RNX.
Left: ER18RNX. Also semi-hardcones have some break-up nodes at 5-7 kHz. Right: W18NX001, it doesn't get much better than this!
Left: Accuton C173-6-191E. Right: Same on mkII baffle; smooth as can be.
This Accuton driver doesn't do much above 4.5
kHz where the others make 6-7 kHz. The question is if this driver has a
bump at 4.2 kHz or a dip at 3.5 kHz. Hmm... hard to tell. Whatever, this
driver does well on the Jenzen baffle too. Listening to the MLS signal
is always a good indicator of serious cone break-ups. This Accuton has a
smooth response and sounds pleasing to the ear - even without any
crossover attached. I recall the MLS signal from pure alu and magnesium
drivers - ear-shredding! Modelling the Accuton looks promising with
basically second order filters for all slopes. Due to the C173's steep
upper roll-off we are facing an asymmetrical crossover with 2nd order to
the tweeter and 4th order for the mid (acoustically).
Left: Accuton CSD plot. Right: And here's
finally the ScanSpeak 18WU/8747-T00 on the Jenzen baffle. This does look
much better than the infinite baffle response at
ScanSpeak facility. Again, it pays off spending time on baffle
geometry.