Infinity RS 1B - Why & How I Modified the Classic Design
Well the story goes like this.....In about 1982 I built my first version of the famous QRS 1-D Hybrid System which I have described above.....by about 1984 these speakers had evolved into mature stunning solid TEAK columns with detached Magnaplanar Tympani 1-D woofer panels.
You know how it goes. After about 5 years or so you always long for more and different no matter how good you have it. By 1990 I moved into a bigger house and had the opportunity to have two nice sound systems. On one the main floor primarily for listening to Hi Fi and Stereo and one in the floor below as a home theartre.
My upstairs system was the QRS 1-D Hybrid System with the Teak Columns, and the Tympani 1-D woofers.
The downstairs system was similar with 60 inch Carver Ribbons hung off the side of a second pair of Tympani 1-D woofers.
Then the inevidable happened. I fell in love with the Apogee Diva's. I found a great set and installed them in my main listening area (the picture with the Thomas Train Set in my pervious photos). I then sold the Carver 60" Ribbons and the attached set of Tympani 1-D woofers and moved my Teak QRS 1-D Hybrid system to the home theartre.
Again I was in bliss. For about 5 years or so. A divorce forced a change in lifestyle and another move. This time again to a new house. I moved the Apogee Diva's to the main room and the QRS 1-D Hybrid system to my new bedroom.
Then searching AUDIOGON out of boardom I ran across a set of INFINITY IRS SERIES III Loudspeakers. Well...no wife...no problem....(Did not have to deal with the Low Wife Acceptance Factor [LWEF] anymore) and so I just had to have them....and so....after a few phone calls....a week off work....a rental van....some hired hands.....and 3000 Miles of driving ....they were mine. In the meantime I had to make some room for them. No way was I going to sell the Apogee Diva's so I moved them to my bedroom and one of my long time friends coughed up the money to buy my complete Teak QRS-1D Hybrid System.
The pictures posted of my current systems with the Infinity IRS Series III Speakers in my main room and the Apogee Diva's in my bedroom are still as is and have been posted above. They remain unchanged.
What happened next? Well, 5 years later ( about a year ago now ) I bought a second house. With the second house comes the need for more stereo equipment. What to do, what to do?
I tried Carver ALS III's. Not bad but not good enough. I tried RS-1B's, again not bad...but not good enough. I tried another set of Carver 60" Ribbons in special hand made Oak towers ( very similar in design to the old Audio Concepts Speakers ) and got another set of Tympani 1-D woofers to mate with them...and it appeared I was getting somewhere close. A set of Infinity QLS-1's fell into my hands.....good...but not good enough.....then I ran into a set of IRS Series V's. Again I just had to have them.
Several phone calls, much money, rental van, some hired hands, and 2500 Miles later they were mine. Ahhhhh....perfection.
They are quite large for the little room I have them in, but after all I am still single and I could live like this....I could be happy. I just would just have to get rid of all my other stuff.
As I looked around I sat back and thought. Boy, those RS-1B's would really be a lot better in this room, if they only sounded as good as they looked. They are the right size. What is wrong with them anyway? Why don't they sound like small IRS Series V's? What is up with them?
So I tore apart one of them and looked at it's entire design, and to my dismay this is what I found...........................
The problem with the original design was that they were a very complicated 5 way design (6 way with the woofers), and although they looked much like the LINE SOURCE IRS Series the original RS-1B's were actually a point source.
The tweeters, although all the same physically were wired with 3 different crossover circuits. One for the back tweeter (3000Hz - 32,000Hz), one for the middle front tweeter (8000Hz-32,000Hz), and one for the top and bottom front tweeters (3000Hz-8000Hz). Thus they did not all cover the same frequency range and this caused several problems including, but not limited to, phase shift between the various EMIT drivers, increased distortion levels (causing the drivers to screach at high volumes - see below), and decreased power handling capabilities.
As for the EMIM's they are originally wired with two different crossover circuits. One for the third midrange down from the top (700Hz-3000Hz) and another for the other six (140Hz-700Hz). Thus all of the upper midrange came out of only one EMIM, the third one from the top, and the other 6 were wired in a series / parallel combination to produce just the lower midrange / upper bass. Again this caused phase shift problems, increased distortion, and reduced power handling capabilities.
Because of these crossover design flaws the RS-1b often blew drivers (especially the EMIM third from the top, as it handled all of the upper midrange by itself). Also even though you had this large array of seven EMIM's you were really only listening to one (the third from the top) and thus you did not benefit from the lower distortion and higher power handing capabilities possible if you used all the midrange EMIMs at once. Also the high frequency EMIT's tended to screach and become beamy when played loud...for the same reasons.
It is hard for me to believe all these design flaws were incorporated into one potentially great speaker. All the elements were there to make this a truely great speaker...but they were all designed out......making the speaker only a shadow of what it should have been capable of, if designed correctly.
You see, there are 2 ways to produce a given volume...A small speaker element moving a long distance or a large speaker element moving a smaller distance. They both move the same amount of air, so the volume is the same. However, in the first case distortion increases due to friction of the air molecules bumping into each other and heating up, and non-linearities in the speaker element the larger the excersion on the diaphram or voice coil, and furthermore you also risk blowing speaker elements when played loud. If the crossover were redesigned, all EMIT elements could share the same load, and all EMIM elements could share the same load...thus they could work in concert as one large speaker....reducing distortion and increasing power handling capability and significantly reducing phase errors between like drivers.
The question was....how to modify?
The main problem with the original design is the odd number of EMIM's (7 to be exact). There is no way of hooking them up in a parallel / series combination and get the same output from all the drivers. I toyed with the idea of only hooking up six, or carving into the cabinet to mount an eigth driver, but then it dawned on me.....I ran into the MONSOON driver some time back (described just briefly in a previous post) and they had all the right characteristics to meet my needs. They had the right impedance 4 Ohms. They had the right size and shape so that I could use 6 of them instead of the original 7 EMIM's with just a small baffle and it would fit into the RS-1B EMIM opening and look nice too. Their frequency response was right on the money and so was their sensitivity. It was obvious I was onto something when I then saw that Brian Chaney (the guy I let have the rights to the Strathern's in 1984) was already using them, yes the same MONSOON drivers I was holding in my hand, yes the same Monsoon drivers I was thinking about using; he was already using these exact drivers in the same actual application, in his new product line. That was it. I had to do it.
So I made the oak baffle plates to do the conversion. Mounted the new drivers. Designed a completely new crossover. Completely rewired the RS-1B speakers. Finally the original grill cloths fit back in place.
This new design eliminates all those prior problems. The Mid/Tweeter columns are now a 2 way design (3 way with the woofers) and the same midrange now comes out off all 6 dipolar planar midranges at once. That is to say all the EMIRM drivers put out the exact same frequencies (150Hz to 2,500 Hz). Also the tweeter array is now set so all 4 tweeters ( 3 facing forward and 1 facing rear) are all playing at the same time as well, from 2,500Hz to 32,000 Hz. The new Electro Magnetic Induction Dipolar Midrange Drivers are made using the latest technology including Neodynium Magnets and are in a permently sealed configuration to maintain their integrety. They are also a little bit bigger length wise, and thus have better impedance and frequency characteristics than the original INFINITY EMIM's.
Each module uses 6 brand new Electro Magnetic Induction Midrange Modules from 150 Hz to 2,500 Hz and then crosses over to 4 genuine INFINITY 1/2 Line Source EMIT tweeters 2,500 Hz to 32,000 Hz. The crossover used is set at 12 db/octave and uses audiophile grade polypropyline capacitors and audio grade inductors. Thus the frequency response of this mid/tweeter system is 150 Hz to 32,000Hz. The woofers cover from 35 Kz to 150 Hz. Thus the entire frequency respone is 35 Hz to 32,000 Hz.
The pictures show a completed pair of modified mirror imaged RS-1B Midrange/Tweeter towers complete with original solid OAK wood baffles and new crossovers. Each EMIM ( EMIRM) midrange driver is a real honest symmetrical push pull design. Each original Infinity EMIT tweeter is actually the same basic design (although the rear output is dampened and sound comes only out of the front of each tweeter...that is why one is used on the back.) I do have an improved EMIT but there was no way of using that EMIT in this design without modifying the cabinet...so I chose to stick with the original 4 EMITs in the design...although I rewired them as noted above in a series parallel combination so they now all play the same thing.
Impedance is 3-4 ohms depending on the frequency you measure it at, and is almost purely resistive. Recommended power is 20 Watts RMS to 200 Watts RMS per channel. Too much power is better than not enough. The sound is sweet and very detailed and they image beautifully.
I have had many questions as to who the actual maker of these midrange ribbon drivers are.....on the back bottom of the midrange ribbon driver it does say: (S)ONIGISTIX CORP. They claim that through the use of their Planar Focus Technology (PFT), these are the only flat speakers that offer the quality that you would expect from a high-end system. These flat beauties produce music based on a similar premise to cone woofers, except that in the place of a cone, a thin polymer membrane vibrates to create the necessary sound waves. Stretched out between powerful magnets, the membrane acts as a diaphragm when electrical currents create a magnetic field that causes the polymer to vibrate and create sound. In addition to looking cool, these flat panels are designed to reproduce sounds at a detail level that surpasses traditional cone speakers. I have added a picture of this logo so everyone can view it [note: the (S) in SONIGISTIX is under a portion of the metal plate and can not be seen].
Sonigistix of Richmond, B.C., Canada originally manufactured these PFT midrange drivers and sold them under the "Monsoon" brand name. The 'Monsoon' brand was also originally associated with OEM-sourced automotive audio speaker systems, notably supplied on a number of General Motors products and then later expanded onto other manufacturers, Volkswagen being one of them. By 2000, Sonigistix expanded its product line and Monsoon brand into the then burgeoning consumer computer multimedia market, developing a solid reputation for their flat-panel speaker designs that were popular with computer users keen on obtaining quality high fidelity from their computer hardware. Monsoon's speaker designs were based on planar magnetic technology, licensed from Eminent Technologies who developed the original concept. However, despite the brand's popularity among computer users--or perhaps because of it--within the next couple of years the assets of Sonigistix is purchased by Eastech, an Asian technology company that also focuses on providing consumer products in a variety of audio-based markets. Monsoon-branded retail audio products continued for a time under Eastech (under the Level 9 name), but by late 2004 the Monsoon brand had more or less disappeared from the U.S. marketplace. By 2005, Eastech no longer sold products under the Monsoon banner (it's assumed that they didn't renew any of the licenses for the planar magnetic technology that made Monsoon speakers what they are, though this information is not confirmed). As for Sonigistix, a privately-held company by that name currently resides in Little Rock, Arkansas, U.S.A. Although an online company profile on goliath.ecnext.com lists this Little Rock company as being in the home audio/video industry, it's not clear if this is the same company that originated in western Canada. As for the Monsoon brand, little is currently known about the company who makes it today. According to the GM, Monsoon speakers are a trademark of Delphi. Delphi happens to be a division of GM that supplies electrical parts to most major car manufacturers. This is smart on GM's part because most Monsoon in-car audio applications occur in GM vehicles anyway. So buying the rights to make them allows for a better relationship between the speaker manufacture and the car manufacture. Currently Monsoon in-car audio is an optional accessory on several GM cars as well as a handful of other cars. Monsoon-branded speakers, whether sold by Sonigistix or Level 9, have developed an almost cult-like following due to their incredible sound and accuracy, particularly uncommon (at the time of their run) for the personal computer marketplace. Dedicated owners of Monsoon flat panel speakers will often go to great lengths to keep their old Monsoons running, primarily because it's commonly held that available new replacements made and sold by other manufacturers are seen--or more precisely, heard--as inferior-sounding also-rans.
Also I have been told by some people who think they know what they are talking about, that Brian Chaney at VMPS Audio (
www.vmpsaudio.com ) uses the same or at least a similar midrange ribbon driver in his line of products. So interested parties might go there as well to find some useful additional information about this product.
Finally while Bohlenger-Graebner does make some great ribbon products, none of them are used in this speaker.
I hope this additional information is useful.
