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As has been previously noted, there are lots of religious issues in speakers.
Dipolar vs. monopolar radiation, planar vs. conventional, soft domes vs. metal
domes, etc. - all have there adherents. It also happens that some companies inspire
religious devotion. Good examples are Magnepan and Quad. Lowther is a British
manufacturer of full-range drivers which not only has achieved religious status, but
actively promotes itself as such. You will find web sites for Lowther clubs
scattered all over Europe. Each is dedicated to the religion that the Only True Way
to build speakers is to use relatively small full-range drivers, horn loading the
back wave. Many have bought into this religion (Lowther drivers aren't cheap!) and
proudly share their designs with each other at these local Lowther clubs. Some of
the pictures posted on the web are truly impressive (and/or bizarre).
Lowther makes 3 main series of speakers:
- The A series uses Alnico magnets.
Alnico is one of the best magnet materials, and easy to form into the complex
shapes Lowther uses. Unfortunately, Alnico is extremely expensive. Of the A
series, the PM2A has been recommended as best all-around and best value. The
PM5A and PM6A are higher end units that compete with the Lowther DX and EX
series (see below). Lowther recommends the PM4A only for use with front (and
possibly back) loaded horns, although I've received at least one recommendation
for it as best all-around. The "A" series also has two 6.5" drivers which are
recommended for use only above 80 Hz.
view
- The C series uses ceramic magnets.
Cheaper and with less attractive magnetic properties than Alnico, ceramic
magnets are used to implement Lowther's "bargain" line. The "C" series also has
two 6.5" drivers which are recommended for use only above 80 Hz.
6.5" view 1
6.5" view 2
- The DX series uses rare earth
magnets. This is a new series, offering many of the advantages of Alnico, but
at a slightly reduced cost. This is probably a good move since the continued
international shortage of cobalt (the "co" in Alnico) insures that Alnico will
only continue to increase in cost. The "DX" series also has two 6.5" drivers
which are recommended for use only above 80 Hz.
9" view 1
9" view 2
6.5" view 1
6.5" view 1
- The EX series is the latest from
Lowther. In most repsects similar to the DX series, the EX series incorporates
a pressure chamber behind the cone and other internal modifications of the
originhal DX design. Because of the rear chamber, the EX driver cannot be used
in several classic Lowther enclosure designs due to mounting interference
problems.
view 1
view 2
Lowther purists generally dismiss the "C" series other than the 6.5" drivers
for special applications. Most of the published Lowther projects use "A" series
drivers, but recent reports indicate that the DX and EX series may be used as well,
and are probably superior in many applications.
All Lowther drivers share some common characteristics: 1) they are extremely
efficient, 2) they each are rated at 100 W, 3) each uses a dual paper cone
design, 4) each has a maximum VC travel of +/-1 mm. (sic!), and 5) each is
bloody expensive for a relatively small paper woofer with a whizzer cone and
limited excursion. These all reflect the Lowther design philosophy.
- Only one VC is used per driver, thus obviating problems caused by
crossovers and assuring accurate time and phase alignment.
- The special rolled (not formed) paper is extremely thin and light weight.
- The design is implemented as a 3-way: a) the radiation from the VC edge
radiates directly into the annulus between the phase plug and the whizzer
cone, b) the whizzer cone handles the wide midrange, and c) the main cone
handles the bass. The "crossover" is via mechanical decoupling between
the radiating elements.
- The VC's are wound with ferric materials rather than copper or aluminum
(silver wire is available as an extra cost option on some models).
Lowther claims this improves the magnetic circuit performance.
- Efficiency is high. Lowther's stated goal is that each of its drivers
should be able to play around 100 dB in an actual listening room with as
little as 1 watt of power.
- Lowther's magnetic circuits are unique in the current market. The size,
weight, and flux density of the magnets are enormous for the size of
cone.
The obvious major question here is how to get any real bass out of a 9" driver
with only +/-1 mm excursion? The answer is that most successful Lowther designs horn
load the back wave of the driver, effectively turning it into a compression driver
in the lowest octaves. On the other hand, others claim good results with Lowther's
in vented enclosures, but many others who've heard such systems say that a good
subwoofer is required for any serious bass. This makes sense- if the maximum VC
excursion is indeed +/-1 mm, significant bass below 100 Hz simply isn't
physically possible (although I don't know of anyone who's actually verified the
factory's 1 mm figure).
Recommended drivers include:
- PM6A, the bargain beginner's
Lowther. FR is rated as 30-20k Hz and sensitivity is rated at
96 dB.
view 1
view 2
- PM2A, the middle of the "A" series
range. FR is rated as 30-20k Hz and sensitivity is rated at
97 dB.
view
- PM5A, the top of the "A" series
range. FR is rated as 30-20k Hz and sensitivity is rated at
98 dB.
view 1
view 2
- PM4A, as previously noted, is
simlar to other A series drivers, but is specifically designed for use in front
loaded horn enclosures. Sensitivity is rated at 98 dB.
view 1
view 2
- DX45, is the lesser of the two
6.5" "DX" series drivers. FR is rated as 80-20k Hz and sensitivity is rated
at 93 dB. Note that the DX series 6.5" drivers are a better value overall
than either the A or C series 6.5" drivers.
view
- DX55, is the top the 6.5" "DX"
series drivers. FR is rated as 80-22k Hz and sensitivity is rated at
94 dB. Note that the DX series 6.5" drivers are a better value overall
than either the A or C series 6.5" drivers.
view 1
view 2
- DX3, once the top of the "DX"
series, the DX3 is still an good value for someone wishing a top-of-the-line
Lowther, but who can't quite afford the DX4. FR is rated as 30-20k Hz and
sensitivity is rated at 98 dB.
view
- DX4, the top of the "DX" series,
utilizing a "Lowther phase equalizer" in lieu of its usual phase plugs. FR
is rated as 30-20k Hz and sensitivity is rated at 99 dB.
view 1
view 2
- EX3, essentially an upgraded DX3
with additional damping on the rear of the driver, mated to a compatible phase
plug. FR is rated as 30-20k Hz and sensitivity is rated at 98 dB.
front view
rear view
- EX4, essentially an upgraded DX3
with additional damping on the rear of the driver, mated to a compatible phase
plug. FR is rated as 30-20k Hz and sensitivity is rated at 99 dB.
front view
rear view
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