Infinity IRS Beta

Infinity IRS BetaInfinity´s Beta Reference Loudspeaker System. Infinity started the classis American way as a garage-operation. Arnie Nudell, John Ulrich & Gary Christie, the first two were aerospace-engineers en the latter a pilot. They did not make it easy for themselves to start with complicated system called the Servo Statik l. The system consisted of one subwoofer driven by a Servo-amplifier with contained also the crossover for the mid- and highrange units. The subwoofer was a servo-controlled 18″ Cerwin-Vega cone, the two mid- and highrange planars have been altered a lot in the different incarnations of this speaker like at first two paper cones and an array of mid- and highfrequency electrostatic units and setups with all electrostatic drivers. Important features are the bipolar character of the system and the servo-controlled woofer that would be the key elements in all the highend systems that would follow from the factory at Chatsworth California.

The IRS Reference System
Twelve years later Infinity introduced it’s no holds barred Reference System the IRS. Weighing in at almost 1500 lbs or 680 kilograms it had two basstowers with six 12 inch woofers that were fed by their own dedicated internal 2kW amp. Ther were complemented by a set of mid/high range planars with twelve midrange units or EMIM’s and twenty-four tweeters called EMIT’s (Electro Magnetic Induction Midrange/Tweeter). These units are flat stretched voicecoils on a plastic carrier hung up between two powerful samarium-cobalt magnets to give them a pushpull action when the outputpower of an amplifier is applied.

Infinity IRS Reference System

Infinity IRS Reference System

As the IRS was the almost unatainable showboat for Infinity a more “manageable” version was offered called the RS-1. As the IRS the RS-1 also consisted of two basstowers (Six 8″ woofers) and two mid/highlevel planars (Seven EMIM’s and four EMIT’s). This system had no active amp on board the basstowers so it needed alt least two stereo-amps to be driven properly. Just like the IRS it did had the active servo crossover to actively filter the low frequencies, give a feedback signal to control the woofersection (the servo-part) and a passive mid/high frequency filter. On the unit several knobs controlled the cutoff frequencies, equalization and level for the low end.

The Beta System
In 1987 Infinty introduced its ‘Beta’ system as the succesor of the RS-1. The basic setup was the same as the RS-1 but now Infinity used four 12″ Polypropylene/Graphite woofers in the basscabinets and new units, besides the EMITS and EMIMS, like the Large-EMIM (L-EMIM) and the Super-EMIT (S-EMIT) in the high/midrange planars. Standing upright they are an imposing 64 3/4″ (165cm) long and weighing in at 420 lbs (almost 200kg) together.

Infinity IRS
The Infinity IRS Beta powered with Treshold amps

As with the RS-1 they need at least two amplifiers. One for the basstowers and one for the mid/high planars. Forget about moderate (priced) amps for this system and any highend Infinity speaker. They were all low efficient designs that really needed big amps to drive them properly. Amps that Nudell preferred were tube designs like the Audio-Research M-300 mono’s. Big VTL’s or Conrad-Johnson would also be good contenders. Other good results with solidstate counterparts from those days were achieved with big Thresholds en Rowland Research’s like the SA/1 and model 7. Brighter sounding designs from Levinson or Krell on the mid/high level units should possibly be avoided.

Infinity Beta with Pass Labs amps

Infinity Beta with Pass Labs amps

Fit and finish of the Beta seemed to be better then the earlier RS and Quantum Series. Placement and setup with auxillary equipment is just as cumbersome. With enough space to bloom and superb electronics they just may sound wonderfull and that’s the problem with this speaker and probably with all big multicolumn products from Infinity: it’s almost to difficult and cimbersome to get it right. So do not even consider to buy such a system on the secondhand audiomarket before you know what you’re getting into. And can be a very frustrating experience to reach the highs that lay in promise with the Beta.

Current Value
As explained above these speakers demand an lot of resources to sound as good as they can. That’s probably why you can sometimes get them at a mere fraction of their new price ( $ 15,000/pair) . Don’t fool yourself and expect at least a double or triple amount of money spending on the frontend-electronics, lots of space and patience. If you already have a large listening-environment, superb electronics and lost of time on your hand and no spouse, this maybe just the audio-bargain for you.

Type Four panel speakersystem with active equalization unit
Introduction 1987
Discontinued 1992
Designer Arnie Nudell
Nominal impedance 4 Ohm
Sound pressure level Sensitivity: 87dB/W/m
Power needed Mid/high section: 75 – 300W/ch, Low: 15 – 500W/ch
Height 65″ (1,60 meter)
Weight 430 lbs (200 kilograms) for the total system
Aditional infomation
Negative Feedbacksystem
According to its designer complexity is needed to reach the goal of the perfect illusion of that ‘being the room’ feeling. One the four 12″ woofers in each tower has an accelerometer that measures the speed and excursion of that particular woofer, feeds a signal back trough small wires to the servo-controlunit where this feedback is compared with the original signal coming from the amps and when discrepancy is monitored the servo makes the appropiate corrections by means of inserting a negative feedback signal into the main signalflow. Most important warning is related to this negative feedbacksystem: Do not create a potentially destroying positive feedback signal by wiring the bass-amplifier cables polarity reversed.
Phase inverting

An amp that’s phaseinverting the signal or has a wide openloop character can also get you into problems. There’s a provision for the this latest scenario right on the servo unit itself that is called the ‘Open loop Gain Comp(ensation)’. So before feeding the system a musicsignal be sure you have verified all the connections, that you have NO inverting poweramp connected and that the levelcontrol for the woofers is way down. Try before you die. As with all Infinity’s woofers they need a reconing/refoaming job in time. There are many sites that can help you out when the foam has been crumbled.
Interesting links
Infinity’s official website (Infinity is now a Harman company)
Infinity IRS Beta Stereophile review from October 1988

Added September 2011
Reviewed by Robert R.F. Sabelis for |

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