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: (516) 682-3523. 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"
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22 THE AUDIO CRITIC
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