It's been a while since I updated this page
and I'd forgotten to add The Loudspeaker, the best speaker I have
ever made. Just because it's around 95 dB sensitivity doesn't mean
it can be run from flea powered SET tube amps, however, using the
Hypex to run the 18" bass, you may bet away with some good 20 watt
tube amps for the MTT section.
From the article:
In terms of dynamics and transparency it
beats anything I've made before. This even from speakers twice the
building price. Price to pay is size - and weight, not to forget! I
had to call in a couple of bodies to help getting the speakers to
our living room. Size matters and none of these drivers have to
work hard to do the SPL. The 18" bass drivers hardly moves
delivering thunderous bass. The midrange is as dynamic and
transparent as can be and the compression driver delivers a
resolution and lack of distortion that leaves even the best of domes
behind. Say no more! Some of the design features here build on
client work and one of them had a visitor claiming the sound being
too dynamic! How can a speaker be too dynamic? One thing we've been
very good at over the last 50 years - since the days of JBL/Altec/Klipsch
and others - is killing the dynamics of reproduced music, and I
guess many people have gotten accustomed to dull and lifeless
reproduction or maybe never realise that most of live concert
dynamics can be had at home. I fully acknowledge that most people
may not want home reproduction as dynamic as live concerts.
The horn and the tweeter only takes a few uF of good caps. The
midrange takes a lot of good uF, but there is no way around
it if we want to hear it all. From the midrange and up you should
feed it from the best of amplification you can afford. This speaker
will seriously display any deficiency in amplification and source
material. Bad CDs and vinyls will sound just what they are! The
good news is that you don't need a huge amplifier to run the MTT
section. My
32 wpc tube amp is more than enough and the bottom driven by the
Hypex module with its 500 watts is well taken care of. In my test
set-up I ran the bass section from my
Hypex UcD amp - with the passive crossover. I can't say one way
is better than the other. Don't even think the simple passive
crossover for the bass driver kills dynamics. It doesn't! Getting
the speakers into our living room and start digging into my record
collection was a quantum leap of revelation. Recordings that had
previously been "problematic" and subject for unpleasant comments to
the producer, all of a sudden came to life and embarrassingly told
the story of how weak a link speakers can be, how much membrane area
is really needed to deliver the true dynamic of most recorded music
and how much is lost in poor energy transfer. The key elements in
all this is the 10" midrange driver and magnificent 18 Sound
compression driver and horn with its exceptional dispersion. You can
have a four-seat sofa in front of these speakers and all enjoy the
presence and phenomenal transparency in midrange and treble. Good
bass can be made in many ways as well as the airiness delivered by
the super-tweeter in the upper octave. Not so critical. Getting the
200-10000 Hz range right is what counts. After a long afternoon
session with a visitor we both noticed no listening fatigue after
several hours of quite loud playback levels. A good sign of very low
distortion. Distortion can measured as content of 2nd, 3rd, etc.
harmonics, but I think there's more to distortion than that. How
drivers with limited dynamic headroom smears detail and colours
sound may on a more subconsciously level be the reason for listening
fatigue as we have to spend energy listening for qualities that
should be there, but just isn't. Here we don't have to
engage in listening, we can just listen, drink our coffee, eat
our cake and enjoy whatever our cartridge is able to pick up from
the grooves - and by the way, when CDs are really good, they sound
good here too.
Pleased to present my first construction dedicated for corner/near-wall
placement. Based on the fact that most people have to place speakers
near walls or close to corners due to simple lack of space or spouse
having specific ideas on living room decor. And also based on the fact
that most people enjoy music while doing other things, they hear
music while others (few) listen to music (audiophiles). Now,
I'm also sure the latter group do not necessarily enjoy
music more than the former group. Quality is highly subjective.
Setting up these speakers in various rooms in our house was a rewarding
exercise in how the rooms played their different roles in shaping the
overall sound. Moving the speakers a little back and forward with regard
to front wall and side walls impacts the sound and experimentation is
imperative in getting the sound you like the best.
Making the cabinets was fun. They are so easy to make, just like the
very first speakers I made in the Seventies. What I couldn't do back
then was making a very simple series crossover, delivering a flat
response with point of crossover exactly where I wanted it. Only really
good drivers and proper measuring gear and simulation software can
create such results from so little. Only 4 (four) components in the
crossover. High impedance (min 7 Ohms) makes this speaker very
suitable for tube lovers.
OBL-15 Open
Baffle Loudspeaker
Click image to go to website
Well, the OBL-11 was sold a few years ago (space issue) and I'd
forgotten what a 15" on an open baffle does. I knew it was good, but
that good? Frankly, it beats any other construction on these pages
regardless of price. None of my other speakers even comes close to this.
Listening to Niels Henning Ørsted Pedersen on This Is All I Ask, track
four, "Just In Time", and you'll know what I mean. The articulation
in lower registers is phenomenal and overall dynamics scary. This is
close to what an upright bass should sound like. Even the best
10-inch bass in a bass reflex box will never be able to deliver such
detail and transient response. Never! Price to pay is size..
TQWT and DTQWT mkIII
Click image to go to websiteThere are two
main features of the new TQWT-mkIII and DTQWT-mkIII constructions: New
JA8008 HMQ
driver and stepped baffle allowing a true LR2 filter to be implemented.
The JA8008-HMQ driver features a high mechanical Q (low damping) and a
better match to the magnificent Eminence bass driver(s), thus enhanced
transient response and low-level detail. The stepped baffle allows true
LR2
filter, which has become my favorite from the constructions made over
the last few years. To properly implement LR2 filters we need to
acoustically align the drivers, thus the stepped baffles.
OBL-11 Open
Baffle Loudspeaker
Discontinued
Click
heading or image to go to website.
This
is my homage to Mr. Gilbert Briggs,
founder of Wharfedale loudspeakers and writer of
numerous books on hifi. My first book on
loudspeaker building was Briggs'
"Loudspeakers", edition 5, 1958,
reprint 1970, and I still have it on the shelf.
Much of what Briggs wrote back in the Fifties and
Sixties is still valid today, thus highly
recommended.
In particular one construction caught my
attention, the SFB, Sand Filled Baffle, and maybe
it was due to the simplicity of cabinet
construction for a young man with limited funds,
or maybe I just liked the physical appearance of
the baffle. The latter prevails to this very day.
DTQWT mkII
3-way
tapered quarter-wave tube design
Replaced by DTQWT mkIII
Click image or heading to read the full story.
To my ears, this
is the best speaker I've ever made - and
the biggest! 150 liter brutto volume is what you
have to be prepared for should you decide to
follow. From the front it seems fairly modest, 28
cm wide and 105 cm high, but depth is 50 cm and
it will require some 20-25 cm minimum to the rear
wall to breathe. Overall sensitivity is 95 dB/2.8
volts and having a minimum impedance of 6 ohms,
it can be driven by low-wattage SET amps. I do
not recommend 2 watts SET; these amps need 98-100
dB minimum no matter what manufacturers may
claim. I have no trouble driving the DTQWTs from
my 8 wpc 300B SET amp. Deep powerful bass - and
that very special 300B midrange. With a proper
300B SET amp you can play these speakers for
hours and hours without listening fatigue, a
clear sign of low distortion and proper balancing
of drivers.
In many ways life gets
easier when we make big speakers. We may
have more and bigger drivers and distortion may
all of a sudden be reduced significantly because
none of the drivers have to move much to produce
high sound levels and we don't have to rely on
drivers being capable of large cone excursions
either.
We may all have experienced a 6" driver
being driven to high SPLs and doing its best to
pump air in order to produce deep bass notes -
and at the same time trying to produce a smooth
upper midrange/lower treble, the 640-2560 Hz
range. It's not ideal but a compromise most of us
have experienced. As long as we don't push a
"six + one inch" too hard, things go
well.
TQWT mkII
2-way
tapered quarter-wave tube design
Replaced by TQWT mkIII
Click
heading or image to read to full story.
Designing
your own driver is a major challenge. Having
worked with hundreds of different drivers, you
eventually come to a point where you would like
to design your own driver, hopefully fulfilling a
wide range of desired features. Some people may
think that cost is a major constraint here, but
it is not, unless you want to use a lot of
chrome, copper and fancy metal coatings; things
that do not necessarily enhance sonic
performance. Metal for the motor system, magnets,
chassis, voice coils, cones and surrounds
basically cost very little. The problem is to get
the parts you want - and in the quantities you
want. If you order 10,000 units, no problem.
Smaller quantities are trouble. Obviously we're
not ordering thousands of units here. That would
be financial suicide. The driver presented here
is not designed to be a commodity product, rather
a carefully designed high-end product aimed at
people enjoying low-wattage, high-class
amplification, but it can obviously be connected
to any high-quality system. Be prepared it will
reveal possible deficiencies in the system
driving the speakers. Be also prepared that it
will urge you to use the best crossover
components available like those seen below.
Supravox DTQWT
experiments
A study into
rather nerdy high-efficiency speakers
using extended range drivers, allowing point of
crossover to be taken above 7-8 kHz, thus a
single driver covering the entire range of basic
notes plus most harmonics.
Nerdy? Well, this is not a speaker for everyone -
I think. It's a speaker for those who want to
explore the world of low-wattage, single-ended
triodes - and not least - the delicate
presentation of the very best recordings from
either CD or vinyl. It's a discriminating speaker
and if you have less than the best source
material, this speaker will tell you. Those
addicted to heavy metal or contemporary type of
music having a constant "noise" level
over the entire frequency band, please look
elsewhere. I like music having breaks, music with
low level passages, etc. How can we build up
expectation and excitement if we don't have
breaks? Anyway....
Driven by the best of SET
amps it can bring you close to the music
like only good fullrange drivers or electrostatic
speakers can do - but there's a price to pay: The
paper cone of the 215RTF64 is extremely thin and
careful damping behind the driver is necessary to
avoid rear reflections and there's a limit to
loud we can play before the membrane starts
breaking up and smears details. T
The 215RTF64 is a large
8" driver having a membrane area of
265 cm^2 and efficiency is around 96 dB. In commercial terms
this means 98-99 dB from the usual overrating of products. In
the treble range it actually does deliver some 100 dB/2.8V, but
this won't help if the upper bass and lower mid does not follow
- and it doesn't.
OB9, 2009 Open
Baffle Experiments
The recipe:
- 1 x JA8008/TW034 kit (= a pair)
- 2 x Eminence Deltalite II 2515 bass drivers
- 1 x electronic crossover, 24 dB L/R with
variable point of crossover
- 2 x stereo power amps, anything from 20 watts
and up will do. Small SET amps can easily run the
mid/tweeter section.
- A decent clone of the beautiful vintage
Wharfedale SFB speaker.
- Liniarise Deltalite II impedance from 15 uF +
10 ohms across terminals.
- Add baffle step loss compensation to the bass
drivers from 8.2 mH bypassed by 4.7 ohms.
- Hook it all up, set point of crossover between
80 Hz and 160 Hz to your liking - and you're
flying!
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OB7, 2007 Open
Baffle Experiments
I'm always ready
for surprises when it comes to speakers.
The sensitivity of this panel is phenomenal,
reaching a healthy 100 dB/2.8 volts in all of the
midband. Actually the JBL tweeter is working hard
to make up to the two other drivers, but despite
the apparent sloped response towards the top
octave, treble seems to be well balanced from
having no attenuation on the tweeter.
Reaching ear-shredding levels, I measure no more
than 5-6 volts peak RMS on speaker terminals,
accounting for some 5-6 watts. This means that
even flea-powered amps can be in here and I
haven't been able to drive the MAE1 amp to any
noticeable distortion levels.
Obviously there's no boxy
sound from this panel. The bass comes
out clear and punchy and listening to acoustic
bass is most enjoyable. It's also obvious that
the bass is not as deep as had the Goodmans been
placed in an e.g. Onken vented box. So, how about
the mid running so high? Well, I hear treble
crisp and clean, but dispersion - or lack of the
same - in upper mid and lower treble is very
noticeable. In that sense it resembles
electrostatic speakers. Move your head a little
and the soundstage changes a lot. There's a hot
spot, no doubt about it. However, due to the
dipole status, this is more tolerable than
expected. A dipole tweeter might be interesting
to try, but where do we find a suitable planar at
this level of sensitivity?
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