3D Connexion IL120s User's Manual
Contents
1. can try adjusting the controls by ear listening to music of appropriate bass content The frequency bands on the test CD that form the basis of the measurement cover the bass range with much greater res olution than a third octave RTA there are 23 test frequencies from 20Hz to 100Hz R A B O S employs a type of parametric equalizer and differs in several important respects from conventional RTA based approaches The parameters that can be adjusted are level bandwidth and frequen cy The controls for level attenuation only from 0dB to 14dB and bandwidth from 5 to 50 of an octave each have 21 steps The frequency control has 19 steps from 20Hz to 80Hz each corresponding to fre quencies on the test CD The setup procedure requires that you first plot the subwoofer s response using the test frequencies and the sound level meter Stereophile Guide to Home Theater November 2001 75 108 0111 Infin p074 76 78x 1 24 02 1 32 PM Page 76 which determines the frequency of the dominant subwoofer room peak as well as the shape of that peak You then set the bandwidth control to match the shape of the peak and attenuate level at the appro priate frequency by an amount that will pro duce a flat frequency response After the equalization process is completed you can check the results by repeating the test tones and plotting the frequency response again R A B O S can correct for only a single dom inan2. no openings in the walls and walls of infinite rigidity Real rooms may be L shaped and have doors archways closets skylights and cathedral ceilings variables that can t be plugged into the formulas Real walls typi cally have rigidity that is considerably less than infinite which can affect the useful ness of the result in ways that are often unpredictable i One bit of advice that s hard to argue with is that the subwoofer should be moved around until you find the position that pro duces the best bass i e the greatest exten sion the most output the flattest frequency response and the smoothest integration Weight 45 lbs Price 899 Bass Optimization Test amp Measurement Kit 59 95 Manufacturer Infinity Systems 250 Crossways Park Drive Woodbury NY 11797 tel 800 553 3332 fax 516 682 3524 www infinitysystems com P Robert Deutsch with the main speakers Fair enough but even if you ignore the possibility that you ll have to make tradeoffs among the different criteria of subwoofer performance for instance the position that gives you the high est output might not produce the smoothest integration this approach assumes that you have considerable flexibility in subwoofer positioning Again the reality may be quite different The position that s ideal for the sub woofer may be exactly where you have the equipment rack with no other conve
3. 108 0111 Infin p074 76 78x 1 24 02 1 32 PM Page 74 SUBWOOFER Infini Interlude IL120s s everyone at least every one who reads this magazine knows the sound of a subwoofer in a room depends not only on the subwoofer itself but also on the room and the placement of the sub woofer in the room You can have a sub woofer that s a sterling performer when measured anechoically but that perfor mance may not be realized in a given home theater setting While some of us are in the fortunate position of being able to build a dedicated home theater room of ideal pro portions most of us are stuck with the rooms we ve got which leaves subwoofer position as a variable to be optimized There are formulas and computer pro grams that will suggest subwoofer position ing but in my opinion these are not as use SPECIFICATIONS Interlude IL120s ported active subwoofer Driver one 12 C M M D cone Frequency response 28 150Hz 3dB Amplifier output 500W 20 150Hz lt 0 1 THD Crossover frequencies 50 150Hz 24dB octave continuously variable Controls subwoofer level phase 0 180 crossover frequency R A B O S see text Finishes cherry natural maple onyx onigre Dimensions 1714 x 1744 x 19 HxWxD 74 Stereophile Guide to Home Theater November 2001 p Systems ful as they seem The ones I m familiar with all use a mathematical model that assumes a shoebox shaped room with
4. ass AB amplifier with a cool running switching power supply In addition to the R A B 0 S controls the IL120S includes a i a phase reversal switch and a continuously variable lowpass filter that can be turned off if the subwoofer is used with a Dolby Digital DTS surround processor receiver The IL1208 s sculpted front panel and grille are attractive and the review sample was finished in onyx anigre which I take to be a term for a better class of fake wood Listening Before trying to fine tune the IL120S with R A B O S I wanted to check out its raw performance with the R A B O S controls turned off completely I set up the IL120S as per my usual practice sub placed at front left just a bit out from the corner the main speaker subwoofer balance adjusted using the built in calibration tones of the Rotel RSP 976 surround preamplifier proces sor or when using the Thule PR 250B processor which lacks a subwoofer calibra tion tone the test tones on Stereophile s Test CD 3 To ensure comparability with my previous subwoofer reviews I used a RadioShack sound level meter Over a period of several weeks watching familiar DVDs as well as new releases I rent many more than I buy the impression that I formed of the IL120S was that for 899 it s a competent but unexceptional performer Extension was good and there was lots of volume available but the bass was a b
5. at stands out in any final system balance using another pair of R A B 0 S adjustments produced signifi cant improvements in measured and sub jective performance the frequency response becoming much more linear with audible improvements in bass evenness tightness and apparent extension major way from the competition But the As far as I m concerned the IL120s with R A B O S optimized is now the subwoofer to beat in the under 1000 category G D
6. es below 30Hz unaffected This would have the effect of the lower frequencies being given more nearly equal prominence with the higher watch for that pesky Low bass extension The IL120S s rated low end limit is 28Hz 3dB and that s pretty much how it sounded with the R A B O S adjust ments More upmarket subwoofers like the Bag End Infrasub 18 and the big Velo dynes go lower and with more authority but within its range the IL120S actually had them beat in linearity of in room frequency response I just wish the powered subs of my Avantgarde Unos in my 2 channel lis was just a single 6dB peak R A B O S controls ones which means effectively greater tening system were equipped with The improvements brought about by R A B 0 S were especially welcome with music There s a tendency for the bass in subwoofer equipped systems to sound dis connected from the rest of the range which e g 40Hz is Position 11 of the Frequency movie sound effects With R A B O S there was better integration of the sound of the IL120S with the main speakers for a more musically appropriate effect The bass was also more tuneful it was easier to follow string bass and bass guitar lines in the mix is more bothersome with music than with Conclusion Considered without the R A B O S para metric equalizer function the IL 120s impressed me as a good subwoofer for the price but not one th
7. it boomy lacking some tightness I played f REVIEW SYSTEM Sources Rotel RDV 1080 DVD player JVC HR 4700U VCR Surround Preamp Processors Rotel RSP 976 Thule PR 250B Power Amp Bryston 9B ST Speakers Dunlavy SC I 5 Cables Digital TARA Labs Decade Interconnect assorted AudioQuest Speaker AudioQuest Type 6 Misc Chang Lightspeed CLS HT1000 power line conditioner AudioPrism QuietLine LF 1 Mk II parallel power line filters 108 0111 Infin p074 76 78x 1 24 02 1 32 PM Page 78 gt Lew Pais Frog Adiust Low Poss gp w 4 ilter sley Sy a Speaker ain i On me SES X Line s0 150 ie RA ES cpat A Our amp Infinity INTERLUDE IL120s around with the surround preamp proces sors subwoofer level control but couldn t get rid of the boomy quality without mak ing the subwoofer sound too weak For the price the performance was still good enough to earn a recommendation but nothing to get too excited about Once I felt I had a good handle on the IL120S s basic sound it was time to try R A B O S I set up the sound level meter on a short tripod placed at the central listening seat and began adjusting first system vol ume then subwoofer volume as instructed by the R A B O S manual That is I tried to before I was able to finish making these adjustments which are preliminary to the fine grained measurement equalization process the sound le
8. ng up in the R A B O S manual the control settings corresponding to these parameters control and with the aid of the adjustment key a kind of small screwdriver turning the equalizer controls to the appropriate settings I then repeated the measurements to check the effect of the R A B O S adjust ments The plot of the retest showed that the peak centered at 40Hz was essentially eliminated with no change elsewhere in the frequency response Actually there was still a 1dB blip at 40Hz but I decided to leave it alone The last stage was setting the test signals on the R A B O S test CD Comparing the sound of the system with R A B O S engaged vs bypassed the sub woofer has a switch that allows you to do this using R A B O S resulted in the IL120S sounding much more subtle and natural more of a piece with the rest of the range The bass drum in Jumanji the scene where the children run upstairs to look for a whatever is making that ominous throb bing sound became tighter not as boomy with less of a sense of prolonged resonance The bass also seemed to go deeper I initial ly found the increase in apparent bass extension puzzling in that the before after frequency response plot showed no i changes in the region of 30Hz and below However the impression of greater bass i extension does make sense when you con sider the fact that R A B O S lowered the 40Hz peak while leaving frequenci
9. nient place in the room to put the equipment Or the subwoofer might sound best when placed in a position that will almost guaran tee that people will trip over it or its cables Equalization One approach to improving in room sub woofer performance is equalization atten uating the peaks and boosting the valleys a process intended to produce an overall more linear frequency response Unfortu nately there are several pitfalls to using conventional equalization in this fashion First boosting a frequency that corre sponds to a dip in the frequency response is not advisable A dip usually indicates acoustic cancellation and boosting the level at this frequency is like feeding power into an acoustic black hole You ll end up pushing the subwoofer to high output lev els with little to show for it except possibly driving the woofer into audible distortion Attenuating a peak might be effective 108 0111 Infin p074 76 78x 1 24 02 1 32 PM Page 75 PHOTOS 2001 CORDERO STUDIOS but as work by Floyd Toole and his associ ates at the National Research Council in Ottawa has shown the bandwidth of the sort of peak you re likely to encounter with subwoofers is often narrower than the tra ditional third octave Real Time Analyzer RTA measurement can detect and cor recting it requires attenuation with a corre spondingly narrow bandwidth I recently attended a talk given by Toole at a meeting of the Toro
10. nto chapter of the Audio Engi neering Society where he exhorted the assembled AES members most of whom work in pro audio to throw away their third octave RTAs R A B O S Floyd Toole now vice president of engineer ing at Harman International Industries Inc of which Infinity Systems is a division acknowledges that optimizing subwoofer performance starts with positioning the sub woofer in the room and that this typically involves some practical constraints Howev er while rejecting the use of conventional RTA based equalization he suggests that a subwoofer s performance can be improved considerably using what he and Allan Devantier Harman s director of engineering and another National Research Council alumnus call R A B O S Room Adaptive Bass Optimization System This is a dedicat ed low frequency measurement and equal ization system incorporated into Infinity s current line of subwoofers and full range speakers that include a subwoofer including the Prelude MTS reviewed by Joel Brinkleyin the July August 2000 issue of the Guide R A B O S is supplied as an optional Test amp Measurement Kit that contains a special ized sound level meter test CD measure ment templates bandwidth selector and an adjustment key An adjustment key is included with the IL120S even if you don t a get the Test amp Measurement Kit In that case you
11. t peak but this is said to be the most common subwoofer room interaction In situations where there are two significant peaks the R A B O S manual suggests cor recting the one at the higher frequency which is likely to be more audible and objectionable If there are adjacent narrow peaks and dips the manual says to leave them alone they re the result of interfer ence patterns that are specific to a certain spot in the room and in any case can t be corrected by this type of equalization 76 Stereophile Guide to Home Theater November 2001 Oh yes the subwoofer Aside from the R A B O S function the IL120S looks like a fairly conventional pow ered subwoofer with a rear facing port that s flared to reduce turbulence The IL120S is not one of those newfangled ultra compact subs and does not have servo control How ever it does have one high tech feature the driver is a special 12 inch unit with a propri etary Ceramic Metal Matrix Diaphragm C M M D and a 60 0z magnet structure According to research reported in a white paper on www infinitysystems com loud speaker cones made of C M M D have fewer inherent resonances and are capable of more linear pistonic movement than any other comparable material The effect is said to be the elimination of colorations due to cone modes which should result in dra matically reduced distortion Amplification is provided by a 500W cl
12. vel meter s Low Bat tery warning light came on The meter had been on perhaps 15 minutes Could the meter s 9V alkaline battery have been on the low side to begin with Perhaps I replaced it with a new battery Another 15 minutes or so of testing and the Low Bat tery light came on again Suffice it to say that I exhausted four bat teries during the R A B O S measurement process and would have needed even more had I not started turning the meter off at 78 Stereophile Guide to Home Theater November 2001 Phase p every opportunity I talked to Allan Devantier at Infinity about the meter s battery Bass ay eating habits and he admit ted that the meter draws ha i Si considerable current but of X said that this was a byprod uct of making it behave lin early at the low frequencies a required for accurate cre R A B O S measurements I Monus think the Infinity people were gotten to by the Ener gizer bunny Apart from having to Battery warning the pro cess of taking the R A B O S measurements plotting the results and making the adjustments turned out to be easier than I had antici pated The plot of the fre quency response based on the R A B O S measure ments showed that there centered at 40Hz and the bandwidth selec tor a neat curve fitting device indicated that the correction should have a 30 band width Then it was a simple matter of look i
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