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DRIVERS
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CABINET
WORKSHOP PICS
MEASUREMENTS
SPEAKER-KIT
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"Hello, I want to start building a loudspeaker. Can you point to a small
floor-stander with deep dynamic bass, smooth midrange and silky treble.
My budget is around 1000 EUR". I have these mails regularly.
Well, don't we all want this? You have
to realise you just do not get all this for a minimum budget. There is
no such thing. You want it small and good - but you have to
pay quite a bit more. Quite a lot more, but if you really want all this, then
this speaker may be the answer. I shall not make any claims of high-WAF,
although I think the cabinets are quite nice. One person's blessing is
another's anathema. It can obviously be made in high-gloss piano lacquer
or gorgeous veneers, etc. Choice is yours.
The construction of the
Purifi-6R certainly called for some more from this company and with
the arrival of the PTT6.5W08-NFA-01 drivers and not least the
PTT6.5M08-NFA-01 midrange driver, the tools for making a significant
larger speaker was at hand.
The PTT6.5W08-NFA-01 "only" has some Xmax of +/-5.9 mm compared to the +/-
10 mm of the X model. Having a twin-bass setup, this is more than
enough. In addition to this a little higher impedance
making it ideal for a double-driver set-up for bass. The W also features
a little higher sensitivity compared to the X model. With a combined
cone area of 266 cm^2 we have something similar to a 9" bass driver and
we can tune the overall system sensitivity to around 90 dB. I like that!
The M model, the midrange driver, is not just a "W" with a shorter voice
coil, as is sometimes seen, when manufacturers have to make a midrange
unit - and save some money. The M has a different basket requiring a
larger mounting hole. I has different rubber surround and it has lost some
weight, 8 grams, (Mms reduction) and possibly
other things I don't know of. Point is, this driver is designed to be a midrange driver.
I started by setting up the bass drivers in some 34 litre test cabinets
and the midrange driver in 16 liter test cabinets (what I had at hand) and tilted the top for
proper time-alignment of the midrange and tweeter. I know some people
don't like stepped baffles - and well, some people don't like sloped
baffles either. Well, we have to arrange for some kind of
time-alignment to allow shallow - and better sounding - crossovers.
For tweeter there was no doubt in my mind that I would use the SBAcoustics TW29BN-B-08 tweeter. This is a phenomenal tweeter and I urge
you to erase any preconception of "metal domes" and what bad metal domes
may sound like. One guy asked if a Be dome would give him more "sparkle"
in the treble range. What he was asking for was probably more
distortion or just simply more level. You don't get that from the SBA Be domes.
Next I constructed my favourite crossover from a range of simulations,
and sat down for a listen. Actually I had bring quite a few more LPs to
my workshop, because this mockup just invited for more and more. You
really can't explain what is happening when all of a sudden you hear
more details in the midrange. When resolution goes up and when
distortion goes down, you kind of expect a wow-effect. Not so, because
what you all of a sudden realise is that you have started to become more
relaxed. Listening has become easier, and you don't know it until you
hear what lack of colouration means. I used a small value Amber-Z
copper foil capacitor for the Be dome and an overall very shallow roll-off and it
made a smooth and seamless integration with the midrange at a fairly
high point of crossover. For sure I wasn't going to change this in the
final crossover. In addition to this it measures very well.
I had some ideas for the cabinet design and hearing my mockup, I
realised I had to go all in when it came to making a heavy, rock-solid,
non-resonant cabinet to allow as little cabinet colouration as possible.
These drivers deserves it. 20 mm Baltic birch will be laminated with 10
mm high-density fiber board, HDF, glued together with elastic vinyl glue.
Due to the twin bass drivers, the 2nd order crossover between bass
and mid and the LCR circuit flattening the upper impedance peak, we can
keep a modest 4 Ohms impedance in the bass region. No big deal for most
amps. When
bi-amping,
the amp running the mid-tweeter will see an impedance of minimum 9 Ohms!
Total yummy for a tube amp. This is what I'm doing.
There will be two basic versions, one fully passive and one having a
Hypex FA251 running the bass drivers. The Hypex version obviously has
all the advantages of room adaption due to the DSP and the one I'll be
making. Should the Hypex programming be an obstacle to you, and you live
in an EU country, ship them to me and I'll do the programming and tests
- and I'll charge you 100 EUR + shipping forth and back. But only EU
citizens!
I used my
Hypex UcD amp for bi-amping and it all worked very well. And BTW,
looking at the
people behind the Purifi drivers, I should think they approve of the
Hypex solution, although Hypex and Purifi are two things. My guess is
that Purifi some day may come up with a plateamp.
Latest vinyl additions. Picking up Christmas presents at the local vinyl
pusher, I came across the Wolfgang Haffner LP and took my chances. I
wasn't disappointed and with Lars Danielsen and Ulf Wakenius on the
team, I shouldn't be. Very good recording made in Gothenburg, Sweden,
and cut in Berlin at Emil Berliner Studio. Visit their website - quite
an interesting place with everything from advanced digital to 2" analog tape. I
don't think the Purifis left anything on that recording I should have
heard and with a wide range of acoustic instruments, a good recording
testing your midrange and tweeter tunings.
Recently I went to hear Vestbo Trio at the local music hall and picked
up a couple of LPs. I don't recall when I last time bought a 10" LP, but
the FLOWMOTION is such a thing. Recorded in a rather small room with a
small audience and my goodness, the dryness of sound and dynamics! A
phenomenal recording - and some really good music too! I cherish this
local Aarhus band.
I can't say the Purifi drivers sound like anything else I have used
before. It was tempting to say the noise floor had lowered, but that's
nonsense. Noise comes from the amps in front of any speaker, but it is
clear the lack of smear pays off and leaves as clean a sound as the
front-end and source material allows. And by clean I don't mean sterile
- whatever that means. We add all sorts of superlatives to sound because
describing sound is futile. If the music is "sterile", then the Purifis
will tell you. If it is lush, it will tell you. If it is dynamic, it
will certainly tell you. You can put anything in front of them - and
they'll tell you what you have done. Even
mp3 (Dec 8th) files sound better on these speakers!
Image to the right is not an LP cover - rather my cappuccino for the
listening session - and I had a lot of these.
Basics:
3-driver speaker.
Dimensions: 25 x 38 x 100 cm, WxDxH. Height 105-107 cm with feet.
System sensitivity: 90 dB/2.8V/1 meter.
Impedance: 4-8 Ohms.
Power requirement: 50+ watts/channel.
Power handling: A lot!
Please
also read:
http://www.troelsgravesen.dk/power-handling.htm,
and remember any burned driver is a misused driver.
Useful links (Please read before writing!):
http://www.troelsgravesen.dk/tips.htm
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/LCR-RC.htm
http://www.troelsgravesen.dk/Inverted-Polarity.htm
FAQ (Please read before writing!):
You cannot change cabinet front panel dimensions and drivers' placement
without needing a new crossover - and I cannot help.
You cannot use any other drivers with the crossover specified.
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/choices.htm
DRIVERS
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Download specs here:
TW29BN-B-8
PTT6.5W08-NFA-01
PTT6.5M08-NFA-01
Please do not ask for alternative tweeters! There will only be this one.
Nor 4 Ohms versions.
And you cannot use the PTT6.5X-04 or
PTT6.5X-08 for this construction.
CROSSOVER
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CABINET
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Click image to view full scale.
Chamfering of the bass section is optional.
Chamfering of the mid-tweeter section, look
here. Can be done by hand.
And again, please go through all of the
tips page. Saves me a lot of mails.
Some angle details here. Sorry about the decimals, but if I leave them
out, some number-nitpickers will tell me immediately.
Mind you, cabinet dimensions can vary, let's say +/- 2 mm and it won't
matter.
Click image to view large.
Cabinet for the passive version.
No, the couple of extra litres derived from the Hypex box, does not
change anything.
Cut the supplied straight tube for port to 200 mm length. Comes in 235
mm length.
Workshop pics
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Workshop total mockup to hear if all of this had a chance. It certainly did!
I thought I'd over the years heard most - from el cheapos to diamond
drivers. It turned out I hadn't.
The bass from these two 6" drivers is phenomenal, deep and dynamic.
The midrange: I probably haven't heard better. Utterly transparent,
dynamic, yet non-aggressive.
The Be dome - well, I knew that one - but silky smooth. OK, I used an
Amber-Z in my mockup!
I wanted to be well prepared for this. Better measure twice - and cut
once!
Starting out with the mid-tweeter cabinet tilt of 6 deg.
If you use 20 mm BB, cut a groove down to the last two layers of veneer,
and they will bend beatifully.
Setting up a test framework to see if the 42o cuts would join
nicely. They did.
Upper joints and the groove for bending the sides.
This is how you cut the sides.
Cutting the side panels and gluing the bottom panel and panel between
bass and mid-tweeter.
Making the braces with cut-out for Hypex enclosure.
Left: My guide for flush mounting the Hypex module. Optional. Right:
Gluing the Hypex housing.
Left: Brace for midrange cabinet.
Right: To figure out the upper front panel design I made a mockup from
residues. I think this is what I want.
Testing driver routings for the first time.
Make sure to chamfer driver holes to prevent any acoustic resistance!
Please read here:
http://www.troelsgravesen.dk/chamfer.htm
All felt in place. I left the rear panel behind the midrange driver free
for the crossover.
Before final lacquer and feet, I wanted to do some more crossover
fine-tuning.
Here with the fully passive set-up and the Hypex UcD running the bass
drivers.
There were quite some changes from the first crossover for my mockup to
the final cabinets.
Midrange depth and transparency was improved from the narrow chamfered
midrange cabinets.
Left: Preparing for the base frame. Quite wide to give the speaker a
solid foundation. Adjustable feet
here.
Right: First lacquer coat.
Mounting the base panel onto the cabinets made me realise they really
didn't look good. Looks like clown feet.
So, I cut up the base structure and made them fit cabinet dimensions:
Looks better, right? These cabs are heavy and don't need a wide base
support.
I placed the mid and tweeter crossover in the upper compartment.
Fill mid-tweeter compartment with 200 grams of wool.
Hypex modules in place and connected to binding posts.
Hypex FUSION FA251
Setting up the FA251, please follow instruction here:
http://www.troelsgravesen.dk/FUSION_FA251.htm
Download program here (zip file):
Purifi-6661.zip
Insert file folder in FilterData folder in My Documents as created when
installing HFD software.
Above the three preset profiles. I'm using preset 2 in my room with a
little boost at 40 Hz.
Presets must be tried to find out what suits your room, speaker
placement - and taste.
MEASUREMENTS
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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.
What interested me the most was the frequency response of the new
midrange drivers. Here on a 80 x 120 cm baffle.
Sensitivity very much around 90 dB/1m/2.8V.
Above the four PTT6.5W-08-01A drivers on a 80 x 120 cm baffle. Smooth
response up to 4 kHz.
With two bass drivers in parallel we will reach some 93 dB sensitivity.
From this we have to deduct bafflestep loss and add assumed room-gain.
The latter is always a guess, but we may well end up with system
sensitivity around 90 dB.
Above one of the PTT6.5W-08-01A drivers on a 80 cm (red) and 25 cm (green)
baffle width.
Impedance in free air of all six units. Green and red are the midrange
drivers.
Above comparing the PTT6.5W and PTT6.5M driver from a 25 cm baffle
width. Red = midrange driver.
Here we see the result of some 8 grams reduced Mms compared to
the W driver. Extended frequency response up to 8 kHz.
Final system impedance for fully passive version.
Here the result of the passive filter for the two bass drivers, w/wo
low-pass filter.
SPEAKER-KIT
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All kit and component prices may be subject to
change and are always to be confirmed by Jantzen Audio Denmark.
Kits can be bought with/without drivers and Hypex module.
There will 6 options, passive and Hypex versions -
with either Alumen-Z or Amber-Z for tweeter, C1.
Download Complete Kit Sale Presentations:
All technical questions to
troels.gravesen@hotmail.com
All questions regarding purchase of
kits, please mail Jantzen Audio at
contact@jantzen-audio.com
CROSSOVER-LAYOUT
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Please read these files:
http://www.troelsgravesen.dk/tips.htm#Glue
http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS
http://www.troelsgravesen.dk/LCR-RC.htm
Tweeter layout
Disregard the loop on C1 capacitor lead. During development I like to keep
long leads on these seriously expensive caps. You never know.
Midrange layout.
Click images to view large.
L2 can be upright or horizontal, no big deal.
Bass layout for fully passive version. C-Coil for L4 giving extremely
low DCR.
My prototype bass crossovers. Just follow the drawing.
The passive bass crossover does not provide the same room adaption
options as the Hypex version, but there are some possibilities in tuning
of the LCR circuit. R8 determines the impact and default is 5 Ohms (2 x
10 Ohms in parallel). If speakers are placed in corners, I suggest
starting here with R8 = 5 Ohms.
R8 = 15 ohms adds some weight to the lower bass if placed further away
from corners. Out on the floor with very little room-gain, you may
disconnect R8 and hear what happens. The difference is some 2 dB in
level, but the price to pay for not using the LCR circuit is lower
impedance, 2.7 Ohms, so make sure your amp can handle this. Minimum
impedance with the LCR circuit in place is 3.5 Ohms, basically a 4 Ohms
speaker.
Speaker wiring
Wiring Hypex version
Wiring fully passive version.
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