Discussion in 'Infinity Loudspeakers' started by pauljh, Mar 13, 2018.
Are audio gear and pickles the only things that get better as they get older?
I don’t know about pickles and audio gear but surely my memory does, doesn’t it?
‘Cause it damn sure isn’t my ears!
It's time for an update. I still have one original and one modified tower, and I'm going to leave them that way until a few more friends have a chance to A/B them and weigh in with their opinions. But that doesn't mean that I don't have more to share.
Here are the measured 3db down points for each crossover channel for the RS1 and the RS1b crossovers:
As you can see, the two crossovers are close. The upper EMIM doesn't go quite a low nor quite as high. The mid-freq tweeters also overlap less with the EMIM on the bottom, and the High-Freq tweeters on the top. The High-Freq and Rear tweeters are essentially the same. Note that these measurements don't account for levels, only the 3db down points of the crossovers.
I also measured the impedance for the RS1 tower and the RS1b tower:
Two comments. 1st) People who say that these speakers are amplifier killers with impedances going down to 2 ohms are wrong. They do go down to four ohms, but that's about it. Also, the phase angle changes are quite modest. 2nd) the major difference between the two is the hump at 1K Hz. If I had to guess, I'd say this was the level pot for the upper frequency EMIM (#3) added in the RS1b spec.
One more impedance measurement graph, this time of one of the bass towers:
This is a normal sealed box impedance curve with a peak at about 55Hz. This means that the bass towers will roll off at 12db per octave below 55Hz. When using the Infinity Reference Standard Crossover, the servo feedback circuit corrects this so the system is flat to 32Hz or so. When you see people saying they are using Rane or Dbx or other third party electronic crossovers with their RS1(a/b) speakers and reporting that it works great, they are people who don't like deep bass, or they aren't telling you the whole story. At the moment I'm using a Rane AC22B crossover, but I'm also using a convolution filter in the JRiver Media Center DSP engine to boost the bass below 55Hz down to 30Hz or so. Without this correction, the system was obviously bass-shy.
Just stopped into say the depth of knowledge shared here great. 90% is way above my pay grade but it is interesting to read none the less. Another ak'er and I were talking about it. His word is "Jelly" and I think I agree for lack of better words.
Those Infinity's in your room, which I think is fantastic btw, are in the right place and the end result here is something I would certainly love to hear. My music taste is all over the board and I'm not selling myself short here, with Jazz and Classical music I can only wonder how GOOD that would sound in that room.
It's time for the next chapter: the Reference Standard Servo Crossover.
As I mentioned in the first post, although my Infinity crossover worked, it was noisy, humming and buzzing. I tried various fixes, lifting grounds on amplifiers and such, but never got it quiet enough to listen to, so I eventually gave up and started using the RANE AC22B that had been lying around in a cabinet for 20 years. Since the RANE was professional gear with balanced XLR connectors, I used two Henry Engineering Matchbox IIs to connect the RANE to my Adcom 555 Mk II, and Mondial/Aragon 4004. It was dead silent and I was happy for several months.
But, I kept worrying that I was missing the true Infinity RS1 experience by not using the servo crossover. I started looking around on the Internet and found an article with some tips (Google for "For all Infinity RS-1B owners having problems with their active controller" and you will find the same article). It suggesting that hum problems could be traced to faulty grounds. "The shields on all the RCA jacks - between themselves and the circuit ground point; should measure less than 1 ohm." Well! my measurements were 45 ohms for the inputs, 8 ohms for the low pass jacks, and about 0 for the high pass jacks. Clearly, this was a potential source of my noise problems. The original RCA jacks were very cheap with fiber insulators to keep the circuit ground separate from the chassis. Over the years, the fiber washers compressed, and the connection between the ground lugs and the RCA jacks got less tight. Since fixing this required desoldering everything and then tightening the RCA jacks, I decided to order some new gold-plated jacks to replace the cheap originals. I had to enlarge the chassis holes to fit the new RCA jacks. While I was messing around in the crossover, I replaced the existing TL082 op amps with the later Infinity-recommended LN353N op amps.
Here is what the original crossover looked like:
And here it is with the sexy new gold-plated RCA jacks from China (installation required enlarging the chassis holes for the jacks).
This fixed the buzz in the midrange/tweeter towers, but there is still some minor hum in the woofers (there must’ve been some reason that Infinity added a hum balance adjustment pot to later versions of the crossover). I have decided to live with it, and I'll now get down to some serious listening.
Hey, watch it! You'll dry up the supply out there and increase prices!
The Nielsen Third Symphony is such a wonderful work. (Serious listening).
This seemed like a good idea at the time. It’s a good thing I’m not trying to fit this in an Infinitesimal.
Not very pretty, but upgraded to get rid of all NPE caps, upgrade all the film caps, replaced out of spec inductors, and upgrade the crossover to RS1b version.
Here’s mine from my RSIIb a few years ago. We used the same caps! See that big 200uf on the right. I used the 250v though.
Okay, I'll admit it, when I first got the speakers, I bumped into one of the midrange/tweeter towers from the back and it fell over on to it's face. Bummer. And the seam between the middle panel and the right wing split. Double bummer. Since then I have put a UPS lead battery on the crossover box as ballast, but that didn't help me the first time. Here is what the tower looked like:
You can see the broken seam, and the water damage at the bottom of the panel. Yes, this speaker had water damage, so I didn't feel so put out about taking it to a local furniture restoration place to get it repaired and refinished. Here is what the repaired panel looks like...
Much Better!! It looked so much better than everything else, that I treated the other three towers with Howard Restore A Finish (Natural):
And though the final result isn't rosewood, it looks mighty improved...
Next is fabricating speaker grills for the two missing from the woofer towers. Does anyone have a source for the large gold Infinity logo pins?
P.S. Sharp eyes may notice the Infinity Modulus satellite on the stand. I recently got a pair of the satellites from eBay, and found a Modulus subwoofer via social media contacts. I was using the Modulus satellites with the RS1 crossover and woofer towers while the broken tower was being repaired. I thought it sounded very good, and the Modulus system (satellites and subwoofer) sounds DAMN GOOD on its own.
Very nice! I run my modulus sub with my rs-1b's, gives a little more punch!
Pardon my ignorance, but by whom is this conducted and performed?
My favorite recording is with Leonard Bernstein conducting the Royal Danish Orchestra.
Nielsen: Symphonies Nos. 3 & 5 (Royal Edition No. 60) https://www.amazon.com/dp/B0000027N6/ref=cm_sw_r_cp_apa_i_Ev3-AbFHF5E0H
I'll bet! The Modulus subwoofer can easily rattle things in my room. Thanks for the idea.
That had to be a heartbreaker when that panel hit the floor....I was fooling around with the 90's putting some old poker chips under one to level it out and damn near lost it. Forgot i could move that fast...LOL.
That's really crazy you guy's using a sub with these, I'd think that many woofers would shake the house ! But after having the QLS-1 which I could barely hear the emits I guess I can understand.
They sure look Purdy Now !
I tried running the Modulus subwoofer with the RS1s. I like it! I have the subwoofer low pass set at 40Hz. It provides a good solid foundation backing up the RS1s.
Glad you like it, I run mine all the time. I've actually got (2) of them, my next move is to run both of them!
As anybody who has gotten to this point in the thread will know, I learned a lot about the RS1b during this project. I also had some close knowledge of Infinity starting about fifty years ago and, thus, know what their design goals were. I have seen descriptions of the RS1 design as being either a "quasi line source" or a "pseudo-point source." I think it is something else, and here is what I think it is, and why...
Arnie Nudell started playing with line source techniques at the very beginning of his career. While developing the Servo Statik 1, he worked with RTR to develop a thin, long “ribbon electrostatic” tweeter to improve the dispersion of the high frequencies over what was available from other contemporary electrostatic panels, which were square. I can’t find any photos now, but the original Servo Statik had an electrostatic tweeter that was about an inch and one-half wide, and 30 inches high. This design, and subsequent work with line arrays, was based on page 36 of the 1957 Second Edition of Harry F. Olson’s “Elements of Acoustic Engineering,” where you will see proof that a driver like the one in the original Servo Statik will have very good horizontal dispersion (because of the small width compared to the wavelength of high frequencies), but a lobe-shaped dispersion for vertical dispersion (due to the line array behavior of the 30? tall tweeter).
At the beginning of the 1970s, the best speaker designers, were contemplating the difference between a loudspeaker and a symphony orchestra. I know that sounds glib and superficial, but the basic problem is that an orchestra (and almost everything else in the real world) has constant power output (power into a hemisphere) with frequency, but the power output of a loudspeaker falls off rapidly as frequency increases, because of baffle and driver size limitations (baffles too small, and drivers too big). Bose “solved” the problem by using an active device to boost high frequencies and then, spraying them all around the room by aiming the drivers at the wall. Infinity started experimenting with line arrays as a more elegant way to control power output by frequency.
Referring again to page 36 of Olson, you will see that by the time the length of the array is equal to the wavelength of the frequency, you achieve a nicely directional radiation pattern with little radiation beyond +/- 60 deg of horizontal. Thus, with a 54-inch line (the approximate length in the RS1b EMIM array), you can get a good directional pattern starting at about 250Hz. But with a 54-inch line, you get severe beaming by 2,500Hz (line size 6x the wavelength), and it only gets worse the higher you go. This kind of beaming can be observed by moving your head above and below the midpoint of the array, where you will notice a fall off of the higher frequencies. The solution to this problem is the secret to the design of the RS1b; it is a five-way speaker, utilizing successively smaller line arrays as the frequency increases. The first band is handled by the active crossover and the woofers from about 30Hz to 150Hz. The radiation pattern is essentially omnidirectional. The next band is from 150Hz to 700Hz and is handled by the 54-inch EMIM array (#s 1, 2, 4, 5, 6, 7). Above that is the upper midrange (700Hz to 3000Hz) array handled by a single 7-inch EMIM driver (#3), then the lower EMITs from 4000Hz to 8000Hz (using “1/2 line source” standard EMITS of about 2 inches), and finally, the upper high frequencies from 8000Hz to about 32kHz, using a “1/4 line source” EMIT (a standard EMIT with one-half of the radiating area taped over, having a line length of about 1 inch). The fifth part of the crossover is the rear tweeter. This was required as power output for a speaker in a room is defined as the radiation into a hemisphere. The EMIMs were dipoles and provided plenty of rear radiation. The EMITS only radiated in one direction, thus the need for a rear-facing EMIT.
And that is most of the story. I think the RS1b speaker was one of the most elegant of the classic Infinity speakers, as it used solid engineering to develop a speaker based on solid theory. Perhaps it is an intellectual speaker. It certainly sounds better than the Bose 901. And while it may not have mid-bass oomph, and the effortless dynamic range of other top high end speakers, it does solve the problem of constant power output very well. Although it doesn’t make much difference, due to the incredible number of drivers in the fabled IRS Vs, if you move your head up and down from the middle of the array, you can hear high frequency beaming, which you will not hear from the RS1bs.
I remember reading an early review of the RS1bs where the writer declared that the tape on the upper tweeter was to tame the highs by reducing output. That, of course, is ridiculous. That wasn’t the point of the tape at all. By shortening the length of the array, the power output at the high frequencies was actually increased. I wonder if Arnie ever sent a note to the reviewer to correct the mistake, or if he just let it go.
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