We know you will be
rewarded with a new and wonderful listening experience for all the types of
music that you love to hear.
The IDS concept is
specifically intended to recreate all of the stereo information as it was
recorded. It brings to the listener accurate details of the artist's work,
whether it is a recording of a traditional symphony orchestra or electronic
instruments. The design eliminates major problems that have plagued
conventional systems for many years. IDS-25 eliminates distortion created by
woofers, mid-ranges, tweeters and crossovers. No subwoofers are needed. All
frequencies are radiated from a single wide-range column.
If you are a true
lover of music and you prefer a system that has great accuracy and brings
out all of the imaging, depth, spaciousness and coherence in the music, then
you will welcome what the IDS-25 can do for you.
This is definitely
a connoisseur system intended to be like fine wine or fine art to be savored
for what it can reveal. Listening is the most enjoyable when you have a
dynamic range that matches that of a live classical music performance, the
zip of big band sound, the velvety smooth jazz or the intimacy of your
favorite vocalist. The sound emanating from the IDS-25 remains completely
faithful from the softest whisper to the loudest crescendo.
Interest in sound, for
Roger Russell, may have started as early as fourth grade when he was taking
violin lessons. By ninth grade, he became a devoted listener to all kinds of
classical music. In the early 1950's, good sound was hard to find and
nothing seemed to accurately reproduce a violin. There were all kinds of
speakers available and they were all lacking in one quality or another.
There had to be something better and he was determined to find a way to
improve speaker performance.
His first exposure
to stereo recordings was in the early 1950’s when he heard Emory Cook’s
binaural demonstrations and the AM-FM stereo broadcasts from WQXR in New
York City. He was soon using a Viking stereo tape deck and two Telefunken
dynamic microphones to make stereo recordings of a Wurlitzer pipe organ at
the Lowes Theater in New Rochelle, NY. This was later followed with a
Magnecord professional recorder that he used to record a few concerts,
thunderstorms and even diesel trains at Harmon, NY.
in 1959 from Rensselaer Polytechnic Institute in Troy, NY with a degree in
Electrical Engineering, he gained experience while working as a senior
engineer in the Audio Products Section of the Sonotone Corporation in
Elmsford, NY, a well known manufacturer of hearing aids and other audio
products. He spent 8 years there designing a new line of loudspeakers and
microphones. Russell also wrote his first two magazine articles about a
stereo volume expander-compressor and sealed speaker system design.
Following this, he
was Director of Acoustic Research at McIntosh Laboratory for 25 years. While
there, he designed the C26 preamplifier, a wide variety of speaker systems,
and was awarded several patents. He continued to write magazine articles as
well as pursue other interests in photography, painting and music. He was
also a member of the Audio Engineering Society and the International Society
for General Semantics. Pictured at the left is the designer and one of his
devoting much of his life to designing loudspeakers, crossover networks and
cabinets, veteran designer Roger Russell has arrived at the simplest and yet
most effective of all of his creations. Compared to the complexity of many
systems made over the years by a host of different manufacturers,
straightforwardness and simplicity can still be found to be the best of all
worlds. In his pursuit of stereo sound over the years, he became even more
resolved to create a loudspeaker system that could dramatically advance
accuracy for stereo sound. The result is the new IDS-25 stereo loudspeaker
It is interesting
to note that almost all recordings are made with a small, single diaphragm
microphone that handles the entire frequency range; but when it comes to
speakers, drivers are almost always divided into at least a woofer and a
tweeter or even more. A woofer needs to be large in order to move a lot of
air. A tweeter needs to be smaller, lighter, and maintain wide dispersion.
Although a microphone can be used in reverse as a driver, as in headphones,
a single small driver is only useful for low power and/or close listening.
You certainly can't shake the room with concert hall sound. It handles very
little power, and has practically no bass output.
The IDS-25 system
is a single column of identical wide-range drivers that cover the entire
frequency range. That's right, the entire frequency range radiates from the
same line source. There are no crossovers, woofers, mids or tweeters. The
concept is an extension of two of his patents. Patent number 4,267,405
Stereo Speaker System for Creating Stereo Images is for drivers arranged
in a long column. Patent number 3,715,501 Loudspeaker System is for
the use of equalization to compensate for the natural low frequency rolloff
of a loudspeaker system.
depend on drivers that face in different directions or have radiation from
the rear as well as the front. This approach uses the room environment to
provide multiple reflections that are supposed to be like what happens in a
concert hall. However, in the real world, the reflections and absorption of
the listening environment control this “room sound” and each listening room
is different. This is hardly the way to convey what is in the recording by
adding extra room sound to the concert hall sound already in the recording.
In addition, a dipole speaker must be placed out in the room. The IDS-25 was
designed to be used within a few inches of the wall. The IDS 25 preserves
the recording and minimizes the room sound. It does this using only a single
column that radiates only from the front and distributes all frequencies
throughout the height of the room.
The IDS-25 Stereo
Loudspeaker System incorporates twenty five 3-1/2" drivers arranged in an
88-3/4" high column. The advertised driver size is deceiving because that is
not the size of the actual moving part. The effective diameter is only
2-11/16". So how can a few small drivers shake the room?
First, if you add
up the area of all the cones, the combined effective area is equal to a 16"
woofer. Impressive! Because the effective cone area is very large, very
little excursion is needed to efficiently couple to the air. A smaller cone
area with a longer excursion will not couple to the air nearly as
effectively. Despite the large effective area, however, these drivers are in
a relatively small enclosure and by themselves cannot provide significant
output at the lowest frequencies. That is where the equalizer comes into
play and is described further on.
Column systems have
been used successfully for many years as a public address loudspeaker. It
was valuable for its high power handling ability and directional properties.
The narrow vertical beam eliminates sound being radiated above or below the
audience where it is not wanted and that could cause acoustical feedback to
the microphone. At the same time, it radiates over a wide horizontal angle
to give adequate coverage where it is wanted.
The IDS-25 is very
directional vertically but the column extends from floor to ceiling. It
means that floor and ceiling reflections that would normally interfere with
the direct radiation are effectively eliminated over most of the frequency
range. At the same time, horizontal dispersion provided by the very small
drivers, ensures a wide radiation angle, even at higher frequencies. This
enables you to always be directly in front of the coverage area, whether you
are standing or sitting. It is a significant advantage over many systems
that radiate as much vertically as horizontally.
The IDS-25 has
another unique feature. All frequencies are radiated as a cylindrical
surface. The sound level decreases only by 3 dB for every doubling of
distance. It means that you can listen closer without being overwhelmed with
loud sound and makes the system ideal for use even in smaller rooms.
Normally, for a
single speaker, whether it is a woofer, mid or tweeter, the sound level
decreases by 6 dB for every doubling of distance. This is because each
frequency is radiated as a spherical surface.
unwanted floor and ceiling reflections, as well as less attenuation with
distance, extends the useful listening area further into the room than many
other systems. This is sometimes referred to as the near field, where most
of the sound comes directly from the speakers and not from room reflections.
When the sound is mostly from reflections, this is referred to as the far
field and is room dependent. The IDS-25 can project direct sound further and
extend the useful near field of your listening room from top to bottom.
In addition, low
frequency room resonances are greatly reduced. This is because the lows are
being radiated all along the height of each column, exciting room resonances
at low amplitude. In comparison, subwoofers located on the floor can build
up some resonances at very high amplitude.
The IDS-25, being a
single column, has a unique sonic advantage over other column systems
because ALL frequencies are being radiated from the same vertical
line. This provides additional sonic clues contained in recordings that
would be otherwise lost to the listener. Systems that have adjacent columns
of drivers, each radiating the same or different frequency ranges can cause
various degrees of image distortion and incoherence.
Normally, a woofer
or subwoofer must be used to extend the low frequency range. Rather than
accept this as the limit for low frequencies, Russell’s earlier patent of
electronic equalization is used to extend the response. The equalizer is
designed to precisely complement the unique response of the drivers and is
connected between the preamplifier and power amplifier. It can be used with
both separate preamplifiers and power amplifiers or with receivers or
integrated amplifiers that have jacks for preamp out and power amp in.
Balanced and unbalanced connections are provided.
The mode switch can
be used to bypass equalization. This way, you can leave the equalizer hooked
up to your system but play a different speaker that does not need
equalization. The equalizer can be left with the power switch at the on
position and it can be powered from a switched outlet at the preamp or power
response of the drivers is very smooth. However, a small amount of
equalization is also used to maintain output at the highest frequencies.
How can the little
drivers handle any kind of power? Not only are they small, but then the bass
is being boosted as well. This seems very contradictory to good design. In
fact, it seems totally unreasonable! If we look at the maximum power
handling for each driver, it can handle 10 watts. If we multiply by 25, we
come out with 250 watts and that's through the entire audio range! True,
boosting the lows increases the power to the drivers at low frequencies, but
even for very loud listening levels, much less power is needed than would be
expected. This is because the IDS-25 has an inherent 10 dB of acoustic gain
over most of the frequency range compared to a single diver. It means that
only one tenth of the power is needed for the same listening level. As a
result, typical listening levels require only one or two watts.
However, there are
occasional deep bass notes, such as a bass drum, pipe organ or even the 25
Hz heartbeats in Pink Floyd's Dark Side of the Moon that do require
much higher power. To safely handle the greatest low frequency peaks, an
amplifier of 200 to 250 watts is recommended. Under these conditions, the
system will play all types of music as loud or as soft as desired. This is
all within the peak power handling ability of the system. The quality of
bass peaks is very surprising, but then, what would you expect from a pair
of 16” woofers?
The IDS-25 is
protected against long-term, high power music levels. If an amplifier
greater than 250 watts is used for even louder listening, the protection
circuit may trip but there is no guarantee that this circuitry will protect
the system against all kinds of program material. In the unlikely event that
the system is driven at excessive levels and the sound becomes limited or
distorted, it means the protection circuit has been activated. Turn the
volume down and wait for ten seconds and then play the system at lower
levels for that particular passage. This will allow time for the automatic
protection circuit to reset.
Of course, a lower
power amplifier can be used if all listening is done at a relatively low
level. However, if a low power amplifier is used for listening at high
levels, the amplifier may occasionally go into clipping and sound distorted.
particularly where a subwoofer is needed, take up valuable floor space. The
IDS-25 has a footprint for the base that is only 14" wide and 12" deep. The
column itself is only 7" wide (tapering to 6" in front) and 9-1/4" deep.
Because the system is capable of significant output down to 20 Hz, no
subwoofer is needed.
The IDS-25 has
exceptionally low distortion. When an ordinary driver is used to cover the
entire frequency range, you can expect the harmonic and intermodulation
distortion to be relatively high. However, the IDS-25 drivers have the same
low distortion construction used in design of soft dome mids and tweeters.
The cone is actually made of woven fiberglass and dissipates energy over its
entire surface, reducing edge reflections and drastically lowering
In addition, the
magnet assembly employs the latest technology consisting of a copper
cylinder in the voice coil gap. This shorting cylinder is known to
significantly reduce distortion contributed by the magnet structure to
1/10th of conventional driver distortion. The improvement is particularly
noticeable in the voice range. The copper cylinder also reduces the
impedance rise normally encountered with most drivers at higher frequencies.
What's more, the entire magnet assembly is shielded to eliminate any stray
magnetic field that would otherwise affect the picture in some television
sets or other devices.
Related to this
distortion is another quantity called Doppler Distortion that is similar to
intermodulation distortion. This is encountered when the same driver
diaphragm radiates both low and high frequencies. The diaphragm motion at
low frequencies shifts the higher frequencies up and down at the low
frequency rate. The longer the low frequency excursion, the more distortion
is generated. If a single driver is used, distortion would probably be
audible at high levels. However, the IDS-25 is unusual because the diaphragm
motion of the combined 25 drivers at low frequencies is extremely small and
modulation distortion is far below audibility.
diaphragm assembly is very light, weighing only 2.5 grams. Use of a flat
spider, which is the major centering device for the voice coil, assures the
same linear cone travel in each direction while keeping the coil exactly
centered in the magnetic gap. A thin rubber surround eliminates the
possibility of deterioration often found with foam surrounds. The heat
dissipation capability at high power is incredible with 25 voice coils per
channel. A single coil used in a 16" woofer is not able to dissipate heat as
efficiently in comparison. Heat buildup in a voice coil can increase voice
coil electrical resistance and cause the driver impedance to change.
sensitivity today is often referenced to a driving voltage of 2.83 volts
instead of 1 watt. It means a 4 ohm system will play 3 dB louder than an 8
ohm system for the same voltage. However, the 4 ohm system is actually
drawing 2 watts of power from the amplifier to accomplish this while the 8
ohm system only draws one watt. This is confusing for the buyer and allows
the manufacturer of the 4 ohm system to advertise what can be mistaken for
higher sensitivity. The IDS-25 is 8 ohms.
Needless to say,
the elimination of crossover networks takes away many of the compromises
involved in juggling components, drivers and crossover frequencies to try to
make the best sound using this older technology. Passive crossovers often
involve losses and can cause unwanted changes to the system impedance in
order to gain an improvement in response. Having no crossover in combination
with the controlled impedance from use of the copper ring avoids presenting
complex load impedances to the power amplifier. Having no crossover
eliminates the debate about which passive components sound the best.
Electronic crossovers require extra amplifiers, adding a significant cost to
The enclosure is
made of high density non-resonant panels. Cross bracing is utilized at
intervals of every two drivers to ensure rigid construction. The braces are
integrally locked to the front, back and side panels. The angled sides not
only benefit by skewing any acoustic resonances but also provide a more
attractive appearance. Acoustic material is used throughout the enclosure to
effectively absorb internal sound reflections. The metal grille is designed
to give protection to the drivers and at the same time be completely
transparent to the sound.
Eighty one feet of
high grade Cardas™ chassis wire is used in each system to interconnect all
of the drivers. Cardas™ is one of the leaders in manufacturing high quality
parts for the audio industry. All connections are wrapped and soldered to
eliminate any contact resistance or corrosion problems. Cardas™ terminals
are used to connect wires that go to the power amplifier. They are solid
copper and plated with gold.
What would it be
like to hear a system like this? It is overwhelming. Perhaps your first
impression will be the unusually good bass response. When you first see the
system, your eyes and past listening experience with small speakers may tell
you that this system definitely needs a woofer or two. Common sense may tell
you that you can’t possibly get any deep bass from a bunch of 3-inch
drivers. But, the bass is not only impressive; it is free from ringing and
“boominess” that is found in some systems.
After making an
adjustment for what you see versus what you hear, more benefits can be
discovered. The response of the IDS-25 is very smooth. It is free from any
resonances, peaks or dips. However, this is not enough to explain the
instant reaction you get when you first hear the system. I found the
coherence, when an entire orchestra is playing, to be amazing. You may
realize, perhaps for the first time, that the stereo image, depth and
spaciousness provided by this system is totally mesmerizing and you are only
aware of what the artist has created.
There are several
qualities that explain how all of this comes together. First, the superior
imaging of the IDS-25 lets you locate the entire characteristic sound of
each instrument more accurately in space. For instance, if the fundamental
tone of a violin is in one place but the harmonics of that note are in other
places, the location and overall sound of the instrument is indistinct.
However, if all of the sound from the violin comes from the same place, the
sound appears more realistic. Then, when all the instruments are playing it
enables you to experience their complete sound at their individual locations
without getting all muddied up with each other. This is true whether you are
listening to the softest or loudest passages. Details are incredibly
A second, and
perhaps not so obvious feature, is the complete freedom from crossover
networks. A driver (or drivers) used to cover one part of the frequency
range does not have the same construction, tonal characteristics or
dispersion characteristics as a driver covering another part of the
frequency range. In the area of the crossover frequency, these differences
between drivers cause sudden discontinuities in the overall sound balance.
It results in a loss of valuable stereo information. By using the same
driver to cover the whole frequency range, a continuous coherent spectrum
can be presented and transients do not suffer.
Third, you will
also experience a completely effortless sound throughout the entire
frequency range. The reason is the large effective cone area that couples so
well to the air. Normally, the area available for mids and highs in most
systems is very small and single drivers are easily driven into distortion
at higher levels. Not only is the sound from the IDS-25 effortless but it
fills the room from top to bottom and appears to play louder than a typical
point source system. When you combine all of these impressions it goes
How many times have
you heard about the “sweet spot” which is the only spot between the speakers
where best listening can be found. This is easily revealed when you are
standing and then sit down. The sound changes. When you try this with the
IDS-25, the sound does not change at any listening height. When you play
spacious recordings, the sound can seem to come from almost anywhere but the
speakers. Sounds can be located in a wide horizontal area and centered in
the region of the listening height. You can even listen as close as 2 or 3
feet from the wall that they are against and still get excellent stereo
sound including spaciousness.
In addition, even
if you are not listening in the center position but way over on one side,
you still hear stereo, depth and spaciousness. The only exception is when
listening to monophonic program material. This could be a monophonic
recording or a combination of stereo sound with mono mixed as a solo at
center stage. The monophonic image will follow you as you move from center
to left or right.
No matter how the
recordings are made, the sound images will be revealed with razor sharp
accuracy when heard with a pair of the IDS-25 Stereo Loudspeaker Systems.
Even if you have been able to distinguish a few of these sounds when
listening to your existing speakers, the IDS-25 system can do this better
because it has inherent design advantages that other systems do not have.
You will most likely want to play your entire music collection over again to
discover the many details and enjoyable sounds that you did not hear before.