Infinity 4.1t User Manual

Floor-Standing 4-Way
Speaker with Powered
Subwoofer

Infinity
“Intermezzo” 4.1t

Infinity Systems, Inc., a Harman Interna­tional Company, 250 Crossways Park
Drive, Woodbury, NY 11797. Voice: (800)
553-3332. Fax: [phone]. Web:
www.infinitysystems.com. Intermezzo 4.1t
floor-standing 4-way loudspeaker system
with built-in powered subwoofer. $7000.00
the pair. Tested samples on loan from man­ufacturer.

Editor’s Note: I hasten to point out,
before the self-righteous element in the
audio community does, that Don Keele is
currently employed by Harman/Becker
Automotive Systems, which is owned by
the same parent company as Infinity Sys­tems, namely Harman International.
Harman/Becker and Infinity are totally
independent of each other, without any
overlap; in fact, they are located 700 miles
apart—but they are connected via Sidney
Harman’s pocket. He, or more precisely his
company, owns a significant percentage of
the audio industry, so that any one of the
limited number of truly qualified audio
engineers (like Don Keele) has more than
a small chance of falling within his
purview. It can’t be helped. As I pointed
out in one of the earliest issues of
Audio Critic, in the late ’70s, the alter­native is to use reviewers totally uncon­nected to the audio industry, such as
audiophile dentists. O

ther magazines do
Unfortunately, said dentists don’t know the
difference between MLS and ETF, and
that matters to me more than our
reviewers’ affiliations. I can assure you, in
an event, that no one at the corporate of­fices of H
about this r

arman International even knew

, let alone influenced it.

eview

The

.

Introduction

o:

mezz

nter

I

a shor

t musical mo
ment separating the major sections of
a lengthy composition or work; or
termediate: one that is in a middle po­sition or state. Both terms aptly

16 THE AUDIO CRITIC

v

in-

-

e

describe the subject of this issue’s loud­speaker review, the Infinity “Inter­mezzo” 4.1t, by appropriately tying
together function and music. The 4.1t
is simultaneously an intermediate
speaker in Infinity’s home theater lines,
positioned between the higher-priced
Prelude MTS and the lower-priced In­terlude, Entra, and Modulus lines; and
at the same time, of course, does an ex­cellent job playing music.

The Intermezzo 4.1t is a tall and
relatively narrow floor-standing loud­speaker with built-in powered sub­woofer, packaged in a total system that
combines first-class industrial design
and handsome good looks. The 4.1t
system couples a thr

ee-way dir

ect-radi
ator system operating above 80 Hz to
a powerful subwoofer using a side-fired
very-high-excursion 12" metal-cone
woofer operating in a closed-box en-

e, powered by a built-in 850-

closur

er amplifier.

w

watt po

The upper thr

ee-way por

tion of

the design is passive and combines a

1

⁄2" cone midbass driv

6

er with a 3

1

midrange and a 1" dome tweeter, all of
which are mounted on the front of the
enclosur

e and cr

ossed o

er at a rapid

v

24 dB/octave rate. The bottom half of

the system is devoted to a rather sizable
closed-box enclosure housing the 12"
woofer, amplifier, system controls, and
connections. All driver diaphragms uti­lize Infinity’s sandwiched composite
metal/ceramic diaphragm material,
which is said to be light weight, quite
rigid and inert, and allows all the dri­vers to operate essentially as pure pis­tons over their respective operating
bandwidths.

I last reviewed a set of an Infinity
systems similar to the 4.1t for
magazine back in 1996. These were the
Infinity Compositions P-FR systems,
which are similar to the current Pre­lude MTS line. It performed excel­lently in all regards except for a
low-frequency response that did not
quite keep up with its upper bass and
higher-frequency performance. My
measurements of the bass output of the
Intermezzo 4.1t, described later, reveal
that it quite significantly outperformed
the bass response of the P-FR systems.
Infinity has been doing their home­work! The bass improvements started
with the higher-priced Prelude MTS
line, whose subwoofer is quite similar
to the 4.1t’s. The Intermezzo line in­cludes a separate powered subwoofer,
the 1.2s, which is equally powerful.

The Intermezzo 4.1t includes a
rich complement of controls and in­puts on the r

ear panel of the sub­woofer enclosure (see rear panel
graphic). The system is equally at

-

home in a complex home theater setup
or a simpler two-channel stereo situa­tion. Inputs and controls have been

ovided for many different operating

pr
configurations, from standalone stereo
operation driven by an external power
amplifier with the system
its signal from the speakers terminals,
to a complicated home theater setup

⁄2"

driven by a Dolby Digital or DTS
processor with separate power ampli­fiers or a multichannel amplifier

The 4.1t’s subwoofer power ampli-

fier utiliz

es a high-efficiency switch-

Audio

s sub deriving

’

.

Manufacturer’s

Specifications

Type: 4-way, floor-standing, with
powered closed-box subwoofer

Drivers: 12" cast-frame woofer
with 3" voice coil, 6

1

⁄2" cone mid

-

ISSUE NO. 28 • SUMMER/FALL 2002 17

mode tracking po

wer supply powering

a class-AB amplifier. The power

’s output voltage tracks the

supply
audio signal in such a way as to mini

e output device power dissipation.

miz
Quoting the 4.1t’s owners manual:
“The result is an extremely efficient
audio amplifier that does not compro­mise audio performance.” The
tracking power supply is not unique
with Infinity, however; it first started
out primarily in the professional audio
field (Crown International and Carver
were among the first to offer the fea­ture on their amplifiers) and then
trickled down to the home market.

The 4.1t includes a single para­metric subwoofer equalizer in its bass
electronics, intended for smoothing
the subwoofer’s response in its listening
environment. As is well known, the lis­tening room heavily influences what is
heard from a loudspeaker in the bass
range below 100 Hz. The equalizer, if
set properly, can effectively optimize
the Intermezzo’s subwoofer response to
complement most listening environ­ments. The parametric equalizer can
provide a variable-width cut or dip of
arbitrary frequency and depth, which,
if matched to a room peak, can consid­erably smooth out the system’s in-room
response. As pointed out by Infinity,
this also improves the system’s transient

esponse

r

because

the low-frequency

speaker-to-room response is essentially

(Techno-geek com-

minimum

phase.
ment: If a system is minimum phase
and its frequency response magnitude

minimum-phase

a

with

flat

ed

equaliz

is
equalizer, its phase response will follow
and also be equalized flat, and hence its
transient response or time behavior will
be optimized.)

This theory is all well and good,

w does the user know how to set

but ho
his equaliz

er for optimum r

esults? On

the one hand he/she could hire an ex-

e acoustical engineer to come in

pensiv
with his one-third-octave real-time
spectrum analyzer, noise generator, and

-

R.A.B.O.S. Sound Level Meter

calibrated microphone, and properly
set the equalizer after doing some mea­surements. Or, on the other hand—
tuh da!—the user could employ
Infinity’s slim LED sound level meter
(see Sound Level Meter graphic) and
the accompanying test CD with de­tailed instructions, which are supplied
with the 4.1t to accomplish the same
task. Gee, Infinity thinks of every­thing! Infinity calls their adjustment
system R.A.B.O.S. or Room Adaptive
Bass Optimization System (love that
acronym!). It comes with documenta­tion and bass response graphs that the
user fills in, along with a circular
hinged clear-plastic protractor-like
gizmo, called a “Width Selector” by
Infinity, that allows the user to rapidly
determine the Q or r

esonance width of
the dominant peak in the system’s re­sponse (see Width Selector graphic).
Matching a speaker/room response
peak by adjusting the parametric filter’s
notch depth and frequency is relatively
easy; ho
the Q adjustment. M

wever, this is not the case with

e on this sub-

or
ject later, in the use and listening sec­tion.

Measurements

o 4.1t

zz

nterme

The I
response was measured using two dif­ferent test techniques: (1) nearfield
measurements to assess the low-fre-

s fr

’

equency

Width Selector Graphic

quency response of the subwoofer, and
(2) windowed in-room tests to mea­sure mid-to-high-frequency response.
The test microphone was aimed
halfway between the midrange and
tweeter at a distance of one meter with

2.83 V rms applied. One-tenth octave
smoothing was used in all the fol­lowing curves.

The on-axis response of the 4.1t,
with grille on and off, is shown in Fig.
1, along with the response of the sub­woofer. Without grille, the response of
the upper frequency portion of the
curve (excluding the sub) is very flat
and fits a tight 3-dB window from 95
Hz to 20 kHz. The woofer exhibits a
bandpass response centered on about
50 Hz and is 6 dB down at about 25
and 90 Hz. In the figure, the woofer’s
response has been level adjusted to
roughly match the level of the upper
frequency response. Averaged between
250 Hz and 4 kHz, the 4.1t’s 2.83 V
rms/1 m sensitivity came out to 86.2

’s 87

dB, essentially equaling I

nfinity
dB rating. The grille caused moderate
response aberrations above 4 kHz, with

een 3 and 11

eduction in lev

a r

el betw

kHz, a slight peak at 12.5 kHz, fol-

y a dip at 17 kHz.

ed b

w

lo

The grille
can be easily removed for serious lis­tening if required. The right and left
systems were matched fairly closely, fit-

±1.5 dB window above 150 Hz.

ting a

18 THE AUDIO CRITIC

Fig. 1: One-meter, on-axis frequency response.with 2.83 V rms applied.

Fig. 2: Horizontal off-axis frequency responses.

equency responses above axis.

f-axis fr

tical of

er

Fig. 3: V

ntermezzo 4.1t’s horizontal

The I
and vertical off-axis frequency re­sponses ar

espectively. The horizontal off-axis

r
cur

e shown in Figs. 2 through 4,

ves with 15° increments in Fig. 2
are well-behaved but exhibit rolloff
above 12 kHz at angles of 30° and be­yond. The system’s vertical off-axis
curves out to ±15° in Figs. 3 (up) and
4 (down) are exceptionally well-be­haved and exhibit hardly any response
aberrations through the upper
crossover region between 2 and 3 kHz.

Figs. 5 and 6 show the input im­pedance magnitude and phase of the
upper frequency portion of the 4.1t
(less subwoofer), with and without the
system’s highpass filter engaged. Fig. 5
indicates an impedance minimum of

3.2 ohms at 120 Hz with the highpass
engaged, and a maximum of about 18
ohms is exhibited at 2.8 kHz with the
highpass off. With the highpass filter
engaged, the system’s impedance rises
to above 20 ohms at 20 Hz. The min­imum rises to 4.4 ohms with the high­pass off. The system’s impedance phase
in Fig. 6 appropriately follows the
magnitude response as any well-be­haved minimum-phase impedance
should. With the highpass filter on, the
low-frequency phase drops to nearly
–90°, as it should for a capacitive
system. The 4.1t should be an easy

er ampli

load for any competent po

w

fier or receiver.

The continuous sine wav

e total
harmonic distortion (THD) of the In­termezzo 4.1t versus axial sound pres-

ig.

el (SPL) in dB is sho

e lev

sur

wn in F

7. The THD for each frequency in the
range of 20 to 80 Hz at each third oc­tave is plotted separately in the figure.
The level was raised until the distor­tion became excessive or the system
could not play louder because of the

The dis-

limits of its built-in amplifier

.
tortion was measured in the nearfield
of the woofer and then extrapolated to
the levels generated at 1 m in a free
space. My experiences with many sub-

-

ISSUE NO. 28 • SUMMER/FALL 2002 19

woofers using 12" to 15" diameter dri
vers indicate a ratio of about 28 dB be-

een the nearfield sound pressure and

tw
that measur
m gr

ed in the farfield (usually 2

ound-plane measurements, which
correspond to 1 m free-field measure­ments); i.e., the nearfield pressure is 28
dB louder than the farfield pressure.

Fig. 7 plots the THD values com­puted from the amplitude of the 2nd
to 5th harmonics as a function of the
fundamental’s SPL. The figure indi­cates a robust bass output rising above
110 dB at distortion levels less than
10% between 40 and 80 Hz. At lower
frequencies, the distortion rises to
higher levels at correspondingly lower
fundamental SPL levels, although,
even at 25 Hz, levels above 100 dB can
be generated at distortion levels below
20%. All in all, the 4.1t’s subwoofer
can reach some fairly impressive levels
in the bass range. Remember, however,
that at low frequencies in a typical lis­tening room, subwoofers can play sig­nificantly louder due to room gain
than they can in a free-space environ­ment without room boundaries.

Fig. 8 plots the 4.1t subwoofer’s
maximum peak SPL as a function of
frequency for a transient short-term
signal, which was a shaped 6.5-cycle
tone burst. The graph represents the
loudest the sub can play for short pe-

estricted fre-

w r

riods of time in a narr

o
quency band in a free-space
envir

onment. I

n-room levels will be
significantly higher. These levels are
significantly higher than the contin­uous sine wav

e lev

eviously

wn pr

els sho
in Fig. 7 and represent the peak levels
that can be reached short term, using
typical program material. These data
indicate that below 40 Hz the 4.1t sig­nificantly outperformed its prede-

, the Compositions P-FR system,

cessor
as I noted in the intr

oduction.

The
bass output of the 4.1t places it solidly
in the upper thir

d of all the systems I
have tested, including several stand­alone subs.

-

Fig. 4: Vertical off-axis frequency responses below axis.

Fig. 5: Impedance magnitude.

Fig. 6: Impedance phase.

20 THE AUDIO CRITIC

Fig. 7: Woofer harmonic distortion (THD) vs. fundamental level, 20 Hz to 80 Hz.

and Infinity’s attention to detail, they
definitely did not present the usual
mundane picture of wooden rectan­gular boxes. With grilles removed, the
picture was no less likable. The side­mounted woofers had a heavy-duty,
no-nonsense look that urged me to
“let’s turn these babies on and see
what they’ll do.” The low end of the

4.1t’s did not let me down. It was like
having a pair of good subwoofers, one
on both sides of my room!

I evaluated the Intermezzos as
two-channel stereo speakers and not
as home theater systems. Their per­formance was outstanding in almost
every area. They would perform very

They str

Fig. 8: Woofer maximum peak SPL vs.

equency

fr

.

ell in either situation.

w
competed with, and sometimes ex­ceeded, the per

formance of my r
ence speakers, the B&W 801 Matrix
Series III’s. I listened to them

Use and Listening Tests

Although each Infinity Intermezzo

4.1t is quite heavy at 93 lbs., they
were relatively easy to unpack and
move around. Without spikes at-

ith their

W

ound

nce

tached, they could be walked ar
on my listening room’s carpet without
much difficulty for positioning. O

esented a strikingly

s pr

set up

, the 4.1t

’
handsome appearance with a thor­oughly modern look.
curved and sculptured metallic design

standing by themselves as well as
alongside the reference speakers in a
rapid-switching A/B comparison
setup. The 4.1t’s did not require any
line-level attenuation to match the
sensitivity of the reference systems.
Their v

olume lev

el was essentially the
same as of the B&W’s when repro­ducing the same br

oadband pr

material.

I first went through Infinity’s

e of setting the

R.A.B.O.S. pr

ocedur

ongly

efer

ogram

el and equalization (EQ), using

bass lev
their sound level meter (SLM) and

y intentions were first to use

CD. M
their supplied SLM and CD along
with their suggested pr

ocedure long
enough to gain familiarity with them
to report in this review, and then
switch over to my one-third-octave
real-time spectrum analyzer (an Au­dioControl Industrial SA-3050A) to
finish the EQ and level-setting process.

But—I was fooled! Infinity’s
method worked so well I continued
using it to measure the room response
and set the built-in parametric equal­izer. I only used the real-time analyzer
to set the overall bass-to-upper-range
balance. Part of the problem with
using the real-time analyzer and pink
noise (played off the Infinity CD or
the built-in noise generator) was the
variability of the band readings due to
the inherent randomness of the noise.
The R.A.B.O.S. system, in contrast,
uses sine wave warble tones, which in­herently exhibit much less level varia­tion. The warble tones, interestingly,
worked better with the real-time ana­lyzer but of course energized only one
band at a time. The warble tones
sounded like something from a ’50s
sci-fi movie,

The War of the Worlds or

Forbidden Planet! The sci-fi ambience

was reinforced by the SLM, which
looked like a cr

oss betw

een a S

communicator and a Flash Gordon

etting the width or Q of the

. S

blaster

­parametric equalizer was made much
simpler with Infinity’s graphical
scheme, using the adjustable plastic
gizmo.

The measured bass response of
the 4.1t’s in my basement listening
room exhibited a broad peak of
about 8 dB at 26 Hz as referenced to

response between 60 and 100

the

the peak was equalized

When

Hz.
with the Intermezzo’s built-in para­metric

equaliz

the bass response

,

er
was much flatter and better behaved.
The equalizer’s controls, which vary

tar Trek

ISSUE NO. 28 • SUMMER/FALL 2002 21

equency, level, and width, are on

fr
the front of each system, accessible

a supplied screwdriver through

with

holes.

small

ow to the interesting part: how

N
did they sound? In a word, excellent!
Interestingly, their sound was ex­tremely close to my reference system’s
on almost everything I listened to. I
often had a hard time telling which
system was playing when set up side
by side. Sometimes I couldn’t believe
my A/B switch and had to walk up
close to the systems to determine
which was playing! Bass was very ex­tended and flat; midrange was smooth
and liquid; while the highs were quite
neutral and very revealing of whatever
I played. High-frequency response
was smooth and extended, but the
highs were slightly emphasized as
compared to the B&W’s, although
they did not lend an air of brusque­ness to vocal sibilance, unlike many
systems. Soundstaging and imaging
were excellent, with a very stable
center image on mono vocal material.
The systems really shined when
played loud on complex orchestral
material with percussion. Even so, I
did notice a bit of upper-bass/lower­mid congestion when I played loud
pipe organ material, as compared to
the reference systems.

The one standout sonic featur

e of
the Intermezzos was their excellent
bass r

esponse.

They could shake the
walls and everything attached when
played at high levels with material

eah…I

having sub-40-Hz content.

Y
know your are supposed to track
down and eliminate all the spurious
vibrations and rattles in your listening
room, but I use them to check for the
presence of honest-to-goodness high-

el bass energy in the room. Few

lev
systems I listen to ar

e capable of rat

tling the walls; the B&Ws and the In-

os can easily do this.

zz

terme

I found myself getting out all my

favorite CDs with high-level low-bass

content to audition o

ver the 4.1t’s.

This included Telarc’s Beethoven

Wellington’s Victory” (Telarc CD-

“

80079) with the digitally r
canons, the bass dr

um on “Ein
Straussfest” (Telarc CD-80098), the
kick drum on Spies “By Way of the
World” (particularly tracks 6 and 7,
Telarc CD-83305), the low pedals on
the organ version of the Mussorgsky
“Pictures at an Exhibition” (Dorian
DOR-90117), and the jet planes and
miscellaneous sound effects on “The
Digital Domain: A Demonstration”
(Electra 9-60303-2). The excursion of
the woofers of the 4.1t was truly scary,
a full 1.2" peak-to-peak capability.

The system really came into its
own on loud rock music with heavy
kick drum and bass guitar. I promptly
turned the 4.1t’s front-mounted bass­level control up to maximum to pro­vide concert-level bass on this
material. The 4.1t took all I could
give it while reproducing a very stim­ulating bass whomp that I could feel
in the pit of my stomach. There’s got
to be something humorous about an
early-sixtyish loudspeaker reviewer sit­ting around listening to the likes of
ZZ-Top, AC-DC, and Kiss at near
concert levels to evaluate speakers. It’s
fun though! Who said you couldn’t
have fun with your hi-fi?

pink-noise stand-up/sit-

the

n

O
down test, the 4.1t’s were nearly per­fect,

exhibiting

hardly any midrange
tonal changes when I stood up—the
full equal of the B&W 801’s in this

ver a bit of a

unco

did

I

d.

egar

r
problem with the Infinity’s upper
bass and lower midrange when I lis­tened to my 6.5-cycle shaped tone
bursts (the same bursts I used to
measure maximum peak SPL for Fig.

in an A/B comparison with the

8)

s. At 40 Hz and below the In-

’

B&W

­finity Intermezzos were the equal of

etween 50 to 80

the

B&W

systems.

B
Hz, the 4.1t’s could play signifi­cantly louder and cleaner than the

ecorded

’s. However, from 100 Hz to

B&W
200 Hz, the B&W’s output easily

the Infinity’s because of the

bested
limitations
cone

of the rather smallish 6

bass/midrange used by the 4.1t.

1

The 4.1t’s 61⁄2" bass/midrange has
generous excursion capability but
with its smaller area could not keep
up with the air-moving capability of
the B&W’s much larger 12" bass
driver.

The 4.1t’s did a particularly good
job on well-recorded female vocals,
projecting a nearly perfect, very real­istic center image with no trace of
harshness or irregularities. Although
the systems shinedon large-scale com­plex program material played loud,
they were equally at home on intimate
material such as string quartets and
other classical chamber music.

’Nuff said. I was very impressed
with the Infinity Intermezzo 4.1t’s.
They performed excellently on every­thing I listened to, and I was particu­larly impressed with their bass
capability. Their imaging and sound­staging was flawless, and they could
play loudly and cleanly on complex
program material that profits from
loud playback. I much liked their
adaptability to match their listening
environment, using the built-in para­metric equalizer and the easy-to-use

e with the supplied

setup pr

ocedur

sound level-meter and CD. Their

oughly modern good looks and

thor
top performance make them naturals
for any home theater or stereo lis­tening setup

.

To get more detailed information
on the Intermezzo 4.1t’s and other In­finity systems, I suggest checking out
their Web site (listed above) and also
requesting copies of their quite inter­esting and informativ
on their method of equalizing r

e white papers

oom
effects (R.A.B.O.S.) and the story be­hind their ceramic metal matrix di
aphragms (C.M.M.D.).

—Don Keele

⁄2"

-

22 THE AUDIO CRITIC