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Everything posted by soundminded

  1. I explained how and why I re-engineered my pair. Clearly 901 offers something that is valuable to many people or it would not have lasted on the market as long as it did and it would not have sold so many units. IMO the original and series II were the best design. The criticisms of 901 are actually valid. However, being an engineer and a tinkerer I don't give up on something I like for one reason that attracted me to buy it in the first place because of something(s) I don't like and I try to see why I don't like it and what I can do about it. I'm not in this industry but I have many relevant skills I was able to bring to bear. No highs, No lows, it's Bose. There's more than an element of truth in this for 901. Why are there no lows? Because the equalizer was designed incorrectly. Further equalization fixed that but power requirements were far greater. Why were there no highs? Because what is now called a midwoofer has too much inertial mass to produce much in the way of high frequencies no matter how hard it is driven and what little it does produce would beam in one narrow direction from a 4" driver. The fix for that was to turn it into a two way biamplified speaker system. This was not nearly as easy as it sounds. The first half hearted try ended in failure. I have to admit it wasn't much of a try. The second try about 10 years later took four years to get it to where I wanted it. I've re-engineered many of my other speakers to because I don't like them for other reasons. This one though was by far the most challenging. The results were well worth the effort and the envelopment effect and other attractions of this speaker were not compromised, in fact they were enhanced.
  2. It's a tough problem. There are still a lot of AR 12" woofers out there that can be restored. The original larger Advent woofer may be comparable. Others used it including John Dahlquist in his famous DQ-10. Finding a paper cone woofer manufactured today that is a close match for the AR woofer is a tough one. There are some dome midranges around but you need to find one with a low Fs. It should be no higher than 1/2 the crossover frequency. The tweeter is the real killer. I don't know of any dome tweeters made today that come remotely close to the AR3a 3/4" tweeter for dispersion. Even the tweeter in the AR9 is no match in dispersion for the AR3a because the dome is slightly recessed. Perhaps an array of 3/8 inch mylar tweeters could work. For the crossover network you're on your own. I'd likely buy an active crossover network and triamplify it. I think the problem with a poly woofer if you can find one that's comparable to the AR 12" woofer is at the high end. It could be useful if you wanted to duplicate something like an AR9 where the crossover frequency is 200 hz. You have a wide choice of 8" paper cone lower midrange drivers usually sold as woofers.
  3. Hi, I'm back again. Sorry to disappoint you folks who hoped I was gone forever. I think the real value of Bose 901 for me was what I learned from the design. Despite its flaws, its claims some of which were valid and some absurd, it was a novel idea and a bold departure from the conventional wisdom of the day. I'll never forget the first time I saw one in a store window with its price tag. I thought who would ever be stupid enough to buy such a thing. Turned out I was and I've never been sorry about it. It was a lot of fun experimenting with it, understanding its unique qualities that made it so attractive to so many people and understanding and correcting its flaws that made it one of the most maligned products by audiophiles I've ever seen. Now for many newbee audiophiles who never heard of it let alone heard a pair it's something from ancient history that at worst gets a shrug. RIP Bose 901 and RIP Dr. Bose who built a privately owned billion dollar company from scratch starting with this product. I'll bet you laughed all the way to the bank.
  4. IMO LST was designed to overcome some problems with AR3a. LST used the same drivers as AR3a but power handling capacity in the midrange and tweeters was quadrupled. This was before the era of AR invented ferrofluid cooling. Dispersion was increased dramatically. The AR 3a/AR2ax tweeter has the second best dispersion of any tweeter I know if, only being beaten out by Allison's own interesting design he produced for speakers under his own brand name. Allison was a great believer in wide dispersion. IMO he got it right and everyone else got it wrong. The way real musical instruments propagate sound into a room is much closer to LST than to any other speaker. The autotransformer in LST and the design of AR 10pi were at a time when graphic equalizers were not available to consumers. Now that they are, those level controls can be bypassed and the system spectral balance can be adjusted inexpensively by better means. As an owner of AR9s IMO in some ways LST was the best speaker AR ever made. In others it was AR9. Too bad there isn't one speaker that combines the virtues of both.
  5. The series III was the beginning of pandering to a lower end market that altered the balance between the cost of the speakers and the cost of the amplifier. The Series 1 and 2 were about $500 for the speakers and $1500 for an amplifier. They were acoustic suspension designes. I used the AR amplifier which actually delivered 90 wpc at 8 ohms. Starting with the series III ported design, the price inverted so that eventually you could drive the $1500 speakers with a $500 receiver. IMO the ported design sacrificed the bottom octave. Personally I thought it was an inferior product. I heard the Series 6 briefly at a Bose store in Newport Beach Ca. about 7 years ago. It has the same non existent high end I heard from my original 901s. I've redesigned mine making it a two way bi-amped system with both active and passive crossovers for the array of tweeters I added. I've posted elsewhere on this site about what I did. It took me four years to get it right. I've removed the 7 db hump at 250 hz I have and straightened out the 8 db falloff between 90 hz and 30 hz. The speaker is now even more power hungry than it was. It retains all of the desirable characteristics of the original 901 with none of its flaws. Except for its limited low frequency power handling capacity (it would take at least 3 pairs in parallel and 600 to 1000 watts of power) it will give my AR9s a run for their money and is actually superior in many ways.
  6. One minor correction about the original Bose 901 Roger, A speaker I'm very familiar with. The problem with that speaker's high end is...it doesn't have one. It cannot reproduce the top octave of sound no matter how much treble power boost is poured into it. Gordon Holt hit the nail on the head when he said the drivers had to much inertial mass. In plain language that means what we now call a 4" midwoofer makes one stinkeroo of a tweeter. At its indicated flat setting it does have a slight peak in the lower treble which is easily corrected by clicking the rotary treble control back one notch. Its other equally unacceptable problems are in the bass. Those are correctable with equalization but require massive amounts of power and multiple units. It should be noted when talking about AR3 and AR3a that many speakers of that era that were also highly regarded had a muted high end. That was the norm. Others that didn't, like Altec A7 were harsh. In the 1970s and 1980s the fashion became to produce speakers that were bright to the point of being shrill. These sold well to tyros in A/B shootouts in acoustically dead showrooms compared to better more accurate speakers. So did the booming ported designs that do not produce the deep undistorted flat bass AR speakers do. It wasn't until the customer got them home and listened to them for awhile that he became irritated by them. This created whole new opportunities of "fixes" for the industry including special wires, a rebirth of vacuum tubes, and the concept of break in. Ironically what facilitated this was the adapting dome tweeters by recessing them into small horns that narrowly beamed their highest frequency energy and making the domes out of metal that resonated, When CDs came along of course they sounded shrill. This gave rebirth to the phonograph record playing equipment industry but by then the recording companies had decisively abandoned vinyl production in favor of CDs.
  7. You have an air leak. Most likely it is between the woofer and the cabinet. Personally I like the black double sided tape Parts Express sells for this purpose. It is cheap and easy to use. I do not like putty. The putty in the AR2as I acquired had turned to glue. It took me several hours with a tool I fashioned to get enough of it out to remove the woofers. The putty in original Bose 901 hardened and cracked. Instead of removing 18 drivers I used clear GE silicone caulk to carefully seal the joints between the speaker frames and the wood and the screw heads. This is also cheap and easy to work with but takes about a day to cure, the tape works immediately. The GE silicone is also easy to remove if that's needed. Just be sure it isn't older than its use by date. If it is, volatile solvents in the mixture will have evaporated and the caulk will never cure. I found that out the hard way on another project. I had to call GE about it. Also be sure never to get any on the cones or suspensions. I think it's pretty safe and use my fingers to help form it before it cures. I just make certain to wash my hands immediately afterwards. So far none of my fingers have fallen off as a result of using it.
  8. AR knew long before 10pi and 11 it had a problem. This was why LST was created. Mid and high frequency power output capabilities where increased by a factor of 4. Horizontal dispersion, the best in the business at the time was also substantially increased. The cost of the angled cabinet had to be more than a rectangular box. The front panel adjustment of FR balance was rethought. Even so a certain individual who may have confused AR LST with Cerwin Vega blew those tweeters up on a regular basis (why didn't he fuse them?) My hunch is it got to the point when the counter men saw him coming they didn't wait to be asked, they started pulling replacement tweeters from under the counter knowing exactly what to expect. When it became obvious that this strategy was getting expensive and they didn't want to single him out by charging him for those replacements AR did the only thing it could do to recoup its losses on him...they hired him. Ken, you still out there?
  9. RoyC, In setting goals for a conventional high fidelity stereophonic sound system I chose a single objective to which everything else is subordinate. That objective is to accurately reproduce the tonality of acoustic musical instruments from recordings. For me if a sound system can't do that, whatever else it can do hardly matters, it isn't high fidelity by my definition. The more I studied the problem the more complicated it got. Timbre is only one aspect of tonality and spectral balance which affects timbre is a far more complicated subject than it first appears. The intuitive concept audiophiles have is a gross oversimplification to the point of being erroneous. Based on the understanding I developed, I have concluded looking at countless designs and no longer bothering to audition consumer audio equipment this problem has also defied engineering analysis of those working in the industry. No commercially available product or combination of products now or in the past when used as intended by their manufacturers can achieve this goal, that is they invariably fail almost every time. There may be a few experimental systems out there including my own which can come a lot closer when carefully adjusted for each recording. They take into account variables in parameters other designers haven't considered. Among these parameters is the three dimensional geometry of sound fields we hear. The inadequacy of equipment to control these variables satisfactorily is plainly obvious from their design. it doesn't mean they can't be enjoyed but they are not accurate, they can't be expected to sound like the real thing.
  10. Steve, I didn't mean to start a flame war....and I never said the sound of the AR3a was thick. The lower dynamic mass of the 10" woofer is easy to infer from the fact that the free air resonance is 26 hz against the 12" woofer's 18 hz. This is on the same page as the graphs I referenced. As one would assume the compliance of the two drivers is substantially the same having similar outer suspension and spider material, only more mass would account for a lower resonance frequency. This business about "speed" is so mixed up and confused among audiophiles it has gotten way out of hand. Let's start off with a fact. If two speakers of the same cone size and shape are playing the same signal at the same amplitude regardless of anything else they will travel at exactly the same speed at every corresponding instant. What may be different is called "group delay" which is the time elapsed between the application of voltage to the voice coil and the corresponding motion of the cone or membrane. There are many factors involved, mass being only one of them. Magnetic field strength is another. So is compliance. I have yet to see any demonstrated proof that so called time aligned or phase coherent speakers were better or even detectable from those that are less aligned. This test could only be performed with the same speaker using variable digital time delays between the drivers. Transient response and frequency response are two ways of looking at the same thing. It is the system response that is of interest to the user, not those of the individual drivers. If AR3a and AR5 woofers had the same FR at their high end the midrange would have had the same crossover point and slope and so would the two woofers. The only component differences would be to account for their different voice coil impedances. Frankly a 1 1/2 " dome driver is tough at its low end. Going by the same rule of thumb as for tweeters response should not extend below twice its resonant frequency. But looking at high quality dome midrange drivers from Morel, Hi Vi, and Dayton it's tough matching these drivers as low as 575 hz as in AR3a. AR5 pushed it up to 650. AR 9 pushed it up to 1.5 kHz and the tweeter to 7khz. Whatever difference does exist between the two speakers in this woofer to midrange crossover region can likely be reduced or eliminated with judicious equalization.
  11. The AR 12" woofer cone/voice coil assembly has greater inertial mass than the 10 inch woofer. This is of benefit at the low end of the woofer's range at the price of the high end. Recall one reason for the redesign of AR3 to AR3a was to cut the woofer's "ragged" response at the high end of the range. This required an improved midrange dome driver. Not only can the AR 10" woofer respond all the way to 650 hz to cross over smoothly to the midrange which BTW is less taxed not having to reproduce the frequencies between 575 and 650, in AR2ax it responds all the way to 1 kHz. In the same way KLH model 17 was superior transitioning from the smaller woofer to the tweeter than KLH model 6. AR5 should be a better speaker converting it to a 4 way with the addition of a subwoofer than AR3a alone. In Fact AR9 is a kind of AR5 where the size of the woofer used as an LMR is that of the even smaller AR4 series and the AR3a woofer is used (doubled) as a subwoofer. The audible superiority of AR5 over AR3a reproducing certain lower toned instruments like cellos has been noted by more than one reviewer. AR5 is therefore an overlooked "gem", an unwanted ugly duckling whose deep bass wasn't good enough for those wanting AR3as and too expensive for those who could only afford AR2ax.
  12. The tweeters are each 3/8" mylars. Unfortunately they are not adjustable, not in this configuration. Back in 1987 I went to a consumer audio show for the first time in a very long time. I liked the clarity of many speakers I heard and noticed that many high end speakers had a rear firing tweeter. I'd played with a 10 band graphic equalizer with my AR9s for years with no success. No matter how I adjusted it, it just never sounded right. I decided to take a chance. I went to Radio Shack and bought a pair of 3/8" 8 ohm mylar tweeters and placed them on top of the AR9s pointing straight up. I keep the AR9s against the wall behind them exactly as recommended by AR. I liked with I heard. Then I added another pair and another pair. Adjusting the program controls to LMR-3, UMR-6 and TW to -6 and using 10 band graphic equalizer (took 2 years) I got much better results. That's how it stayed until about 2008 when I acquired 175 4 ohm Sanyo 3/8" mylar tweeters at 28 cents apiece from Parts express. These were meant as snap ons for 6 X 9 car speakers. I arranged them to hang from each other vertically 4 per side firing sideways. I wired them in a 2 series strings which were wired in parallel combinations to keep the overall impedance a reasonable 8 ohms. (remember this is in parallel with three other 8 ohm outboard tweeters and the AR tweeter. I have never damaged or shut down an amplifier this way.) With 3.3 mfd caps for the whole bunch, the same used for each of the RS tweeters something was very peculiar. I'd created a duplicate of the strange sound I'd heard and remembered from the Snell Type AII and AIIIi. It was clear what was happening, a too strong lateral reflection at probably around 6 kHz or so created this coloration. This is done acoustically by the single Snell tweeter by gluing a piece of polyurethane to the center of the tweeter dome compromising its on axis output. I listened to it for a few hours, lost interest in it and never cared to hear it or Snell type A again. Eventually I settled on 2.2 mfd raising the crossover frequency of these 8 tweeters and the peculiar sound disappeared. Re-equalization has remained the same for the last 6 years with no plans to ever change it. With Bose 901 the opposite happened. That system is bi-amplified. At about the same time I added two of these tweeters per channel in series and placed them on top of the speaker aimed at the ceiling. This in addition to the four I'd also added horizontally 3 rear and one firing forward but the forward one having a resistor bridge network that cuts its output 75% compared to each of the rear firing tweeters. It is amazing how little sound these tweeters put out but what a powerful difference they make. I've concluded that while the human ear is not nearly as sensitive to these high frequencies as it is to midrange sounds, it makes great use of what it gets. Small differences in FR, loudness, and angle of arrival of these sounds mean a lot to what I perceive. Adjusting them for the room and matching the rest of the speaker system requires a lot of patience and perseverance. In the case of Bose 901 that took 4 years.
  13. In the library on this site there is a page which compares the FR of AR3a, AR5, and AR2ax. It is in the AR3a series frequency response and specifications. For some reason I can't cut and paste a link to it. These curves tell the story of what I hear. You can see right off the bat the low on axis output of the tweeter compared to the midranges and woofers. Despite the woofer having low sensitivity, AR3a tweeter pays the penalty of low on axis output for much better dispersion at the highest frequencies than contemporary tweeters that beam their high frequencies often making them shrill and piercing on axis. Look very carefully at the difference in the FR of the high end of the woofer for AR3a and AR5. There is more output from AR5 where it crosses over to the midrange dome, that is the dip where they have the same output is less for AR5 than for AR3a. AR2ax shows the crossover design defect where a 2 to 3 db peak at the woofer midrange crossover is to be expected from the graphs. And it is audible. The superiority of the AR3a woofer driver at the lowest frequencies over the AR2ax/AR5 driver is also obvious with AR 5's and 2ax's rolloff starting at a higher frequency and never making it to the left side of the graph which is 10 hz. It is also steeper than AR3a's. This points out a fact AR grappled with as well as all other speaker designers. A loudspeaker driver is a resonant device having a useful bandwidth of about 2 1/2 to 3 octaves. To cover 10 audible octaves with 3 drivers something always has to give and always did. AR9 killed the problem off with a fourth driver making it easy to cover the entire audible range. The added benefit of the super woofer design just added frosting to the cake. This low end capability results in a strange phenomenon unique in my experience to AR9, it can "take over" a room if you let it. It is unfortunate IMO that AR9 did not incorporate the tweeter section of LST using the same wide dispersion tweeters in multiples. I think if Roy Allison had a hand in it, it would have. To correct this I had to add 11 additional outboard tweeters per channel. They fire indirectly to create substantial high frequency reflections coming from above and to the front and sides of the listener the way AR LST does. With judicious equalization and use of the level controls AR9 is an excellent speaker by any standards. It's one flaw IMO is that it is not a direct reflecting speaker in my case between 200 hz and 6 kHz. To eliminate this flaw I'd have to design a speaker from the ground up. Altering AR9 to achieve these results with 4 additional LMRs and UMRs per channel would be an even more daunting task for me. OTOH, one day I might just try it.
  14. In the 1960s time after time AR3 and AR2ax sounded muffled, muted, lacking in treble, bland, call it what you like. Some generous people called it "polite." Phooey on politeness. My reference was and remains live unamplified performances of acoustic instruments. With musicians in my house and owning 3 pianos and assorted violins and violas, having attended countless live concerts I have the sound of live acoustic instruments well drummed into my head. One time I had a chance to directly compare the sound of AR3 with KLH model 17 for an extended period. AR3's bass was clearly far superior but from there on up there was no contest. KLH model 17 won hands down. Therefore I was surprised at what was until recently an unexplainable strong similarity between live music and recordings played through AR3 at the two demos I heard IHF trade shows in NYC in the 1960s. In the first one played against a guitar I was directly on axis and the AR3 was imperceptibly brighter than the guitar. In the second, Tom's statements to the contrary notwithstanding, The AR3s were on or near the floor while the nickelodeon was high on a table. The AR3 speakers flanked the table and AR4xs flanked the AR3s. The tonal similarity however was remarkable with full treble. In addition to most people operating these speakers with their controls in the "dot" position which is not their flattest response, as I now understand it Roy Allison who conducted the demos boosted the treble control on his Dynaco PAS3X preamplifier. This flattened the FR considerably. It was typical for audiophiles to always operate their preamps in the flat position and the obsession was so great, equipment manufacturers of better preamplifiers put a tone control bypass button on their equipment and then eliminated tone controls altogether. The last thing in the world an audiophile would consider is a graphic equalizer. That may be for the better since most in my experience don't know how to make the best use of them, expect instant results, and invariably fail. Nor are automatic equalizers called "room correction" particularly effective in correcting FR errors to the satisfaction of my ears. Having restored a pair of AR2axs when first turned on and played flat they had the same defective sound I'd remembered from the 1960s. However, with judicious adjustment of the level controls, tweeter full up, midrange slightly below the dot setting and appropriate equalization to boost the bass and treble and cut a small peak in the midrange AR2ax proved itself to be an outstanding performer with very high accuracy and not requiring outboard supplemental tweeters as all other speakers including AR9s do IMO. Placed diagonally in room corner AR2ax has the same treble sound everywhere in the room. In fact AR2ax's 3/4" tweeter has far better dispersion than AR9's recessed tweeter. Additionally AR2a and AR2ax (I have both now) demonstrated astonishingly clear and powerful bass. As of now with proper equalization I'd say AR2ax is clearly superior in every way to KLH model 6. I also have two pairs of those. However, it should also be noted that while AR2ax has outstanding bass it is not in the same league with AR9. You'd have to go some to equal that even today. The argument about HF rolloff of sound heard in concert halls to rationalize classic AR speaker performance by Villchur in the 1960s and the same argument used to design speakers for BBC in the 1980s is a flawed argument. These measurements were based on steady state response to what is clearly a transient phenomenon. The first arriving sound at the listener is the same you'd hear close up or out of doors with the strongest high frequency components that give sound their clarity and characteristic timbre. As the reflections die out the high frequency overtones die out faster than the middle and low frequencies. This can be seen in any text on concert hall acoustics in a graph of RT versus Frequency. By 8 kHz RT is usually about 50% of what it is at 1 KHz. Therefore unless you recreate the acoustics of a live venue you cannot accurately recreate the tone of instruments heard there. Most speaker designers today opt for brighter sounding speakers even though they are also wrong for recreating concert hall and opera house tonalities. At the current state of the art of home hi fi, the industry has not recognized this fact let alone addressed it. People seem happy enough with the current flaws in their equipment...for at least a week or two after they buy them when they start shopping for their replacements.
  15. AR5 should probably have been called AR2axa or AR2y. That's marketing for you. During the evolution of the AR2 series it slowly morphed into an AR3a with an AR2 woofer at which point it became AR5. The dilemma AR and everyone else faces who builds mulitway speaker systems is that loudspeaker drivers are resonant devices with a usable range of only about 2 1/2 to 3 octaves while normal human hearing is10 octaves. Something has to give and in AR's design of this era for its TOTL systems it was the match between the woofer and midrange driver. In AR3 the problem was with the woofer midrange crossover at the upper end of the woofer's range. In AR3a it was the same only the problem was with the low end of the midrange driver which had been improved over AR3. In AR2 series and AR5 it was at the lower end of the woofer's range which while remarkable for its size and cost is not nearly the equal of the AR 12" woofer. However the gain was in the woofer/midrange matchup. In some ways this makes AR5 a better speaker than AR3a at least to the way some people see it. The cost is the lower part of the lowest octave and power handling. The problem persisted until AR9 blew the whole problem out of the water with a separate lower midrange and two 12" woofers. Regrettably, at the same time AR gave in to popular market demand and compromised the dispersion of the midrange and tweeter going in the opposite direction of LST. LST was an evolutionary step up from AR3a in mid and high frequency power handling and dispersion.
  16. None of this looks right to me. I've never seen one but there is a clear story about how the first AR acoustic suspension speaker was created. The story has it that the surround was cut from a bed sheet by Villchur's wife who had skills to do this acquired I think during the war. The entire idea was to created a woofer with a loose suspension and to get away from the stiff accordion pleated suspension used even today by pro speakers. Perhaps the woofer in the left photo is a work in progress. The frame looks right, the magnet looks right, but the suspension looks wrong. It almost looks like someone else's design is being adapted by AR. Perhaps this was being trialed as an early prototype.
  17. dxho, I like the way you drew the schematic. It's closer to how I've redrawn it. The way many people draw schematics and wiring diagrams drives me nuts. I sometimes have to redraw them just to understand them. I also don't understand why the caps for the mid and tweeter aren't in series on the + side of the input and the speakers connected from the sliding contactor terminal 3 to ground (minus.) It's the same circuit and easier for me to understand. Why didn't someone tell me about vinegar BEFORE I took a wire brush attachment on a Dremel type tool to clean them and wrecked them? BTW I think they're 25 watts. I think I'm going to replace mine with L pads. There are very few speakers that use potentiometers as volume controls. The reason is simple, as the control position is changed, so is the crossover frequency. BTW, the AR2axs still work great. One problem with AR2a I noticed was the warpage of the cones on all of the 5" Jensen the midrange drivers. When I visited Bill at Millersound he was manufacturing new cones for these drivers for someone who wanted an authentic restoration. I still haven't decided what to do with them yet. Hey, It's only been about 7 or 8 years. Give it time, give it time.
  18. The treble of all of the classic AR speakers IMO was dreadful. Rolled off, muffled, not clear or distinct. In experiments directly comparing AR3 with KLH Model 17 AR3 had far superior deep bass but above that KLH Model 17 blew it away. In showroom after showroom, in experiments at school, it was always the same. How? Why? And then a strange thing happened. I heard two LvR deomos of AR3 and remarkably they sounded a lot like actual musical instruments. How was it done? Well I never found out until a few years ago on this site. And then experimenting with AR2ax. The tonal balance of these speakers as manufactured is awful. The bass overpowers everything. Villchur tried to justify the high end rolloff using the same faulty logic BBC used 20 years later. Restoring AR2ax, amazingly with properly functioning tweeters revealed that when carefully equalized these speakers sound very accurate. They beat KLH Model 6 every way there is. Dispersion of the AR 3/4" tweeter is superb. There is no audible difference on axis and 45 degrees off axis. Pushed hard the bass of AR2ax is also amazing. Personally I like the sound of the original cloth surrounds with ferrite magnets and the cast frame better than the newer versions. But the square magnet AR9 woofers in my version show this beast is a killer. No other speaker I ever heard seems able to dominate a room like AR9 if you let it. It is a very strange effect. Cutting the bass back makes it sound more like the original ferrite version. Unfortunately IMO the treble is still poor. It had to be substantially "augmented" with additional tweeters and the entire system rebalanced. When properly tuned, it's hard to beat for accuracy. Unfortunately I cannot convert it to a direct/reflecting system. Too much time and effort. But it can be made to have the timbre much like the Steinway piano at the other end of the room...but like other speakers, not the size or power of what is far closer to an omnidirectional radiator which is different from loudness. It can also emulate the sound of outstanding famous violins made in Cremona Italy very well, sounds I'm also familiar with. The AR 12" woofer works best as a subwoofer cut off at 200 hz. In AR9 Acoustic Research finally gave up and conceded that they cannot get 3 drivers having typical usable ranges of 2 1/2 to 3 octaves cover the full 10 octaves of sound. No one else can either at least without extraordinary effort.
  19. Small wonder the Magneplanars sounded better. You should have repaired these first and listened to them again before you compared them.
  20. DavidR, mine were original with cloth surrounds. The surrounds were fine but the putty had hardened and cracked. The enclosures were no longer air tight. Bose said the speakers were unrepairable but since I was the original owner they offered me a trade in for half off on a Series VI. I declined because I felt the ported design is inferior and compromises any possibility of rescuing the deepest bass. I caulked my with GE silicone and they've been air tight ever since. However, they require an additional low bass boost making power requirements enormous. One pair isn't sufficient because while they have the radiating area of a single 14" driver, their Xmax is low. The low bass cut and the upper bass hump are easily correctable with equalization. The real challenge was the treble. IMO 901 hasn't got the top octave at all. Most other speakers don't have the bottom octave. As I've said in the past I solved that problem with 6 tweeters per channel where about 95% of the radiation is indirect. They cross over around 9 kHz with a 6db per octave slope. The Bose equalizer is usually set at one notch below flat to reduce a lower treble peak. The speaker must be equalized for each recording. Four 2 channel equalizers (one is the 901 equalizer) are used. With that done correctly, the speaker retains all of the advantages of 901 and none of its disadvantages. It can easily be made to clip my 138 wpc Marantz receiver, the most powerful amplifier I own. Replacing it with a more powerful amplifier without adding more 901 systems would be a wasted effort as the improvement would only be 3db which IMO is too marginal. The resulting image BTW is the equivalent of a wrap around flat panel speaker.
  21. DavidR, I've had even more experience (by 15 years) with original Bose 901 than I've had with AR9. Bose 901 has some remarkable capabilities, it was a radical departure in concept. The nature of its flaws in execution are different from those of most other speakers making them unacceptable to audiophiles. They are correctable however. The engineering fixing them was much harder and took much longer than fixing AR9, in fact it was the toughest I've ever encountered. Two tries, the second successful attempt taking four years. I can say this categorically. With several re-engineered pairs (at least 4 pairs) and sufficient amplifier power (at least 1000 wpc) original Bose 901 will equal AR9s bass and outperform it in every other respect. It has several significant advantages over conventional loudspeakers that others cannot be corrected for. BTW, if I wasn't satisfied with a planar type loudspeaker I wouldn't know where to begin trying to fix it. I haven't heard Magneplanars except once a long time ago. Most planar speakers have among other defects narrow beaming of high frequencies which for me is not acceptable. Critically listening to electrostatic speakers like Martin Logan Summit and Soundlabs 8' tall curved panels I found serious FR flaws especially with the MLs. I cannot deny their clarity though.
  22. A Thorens Turntable with an SME arm is an excellent performer. I considered buying one myself when I shopped for my first serious turntable. Ironically it was the sales rep for these products who convinced me to buy Empire instead and now I have two of them. However, had I bought the Thorens/SME combination I'm certain I'd have been perfectly happy with them and I'd still have them and use them. One problem you won't have is acoustic feedback. AR9 and even Bose 901 as I've used them have bass so powerful, so much low frequency gain that a turntable is out of the question in the room where the AR9s live and I can easily get acoustic feedback if I'm not careful from Bose 901 too. Empire 698 has a suspended subchassis like the AR turntable but even so, much more isolation would be needed, say an optical table with air pistons.
  23. For all the accolades written about AR9, a speaker I've had experience with now for 30 years, out of the box played flat like all AR and other speakers I found it unsatisfactory for accomplishing what for me is the primary goal of a loudspeaker system, reproducing the tonality of acoustic instruments accurately. I experimented with a graphic equalizer for years and it didn't help. Like other AR speakers its main problem seemed to be its treble. Only after re-engineering high frequency propagation with additional tweeters combined with equalization could I get the timbre right. However, compared to some real instruments such as the Steinway piano at the opposite end of the room the AR9s still sounds small until you're a good 15 to 20 feet back. The problem there is its inability to radiate midrange sounds in many directions, it beams most of it forward. Re-engineering that would take a major effort and frankly it's not worth it to me. Whoever argued that Bose 901 made a piano sound like it's 8 feet wide and therefore bad has evidently never seen or heard a real concert grand piano. Steinway D is 8'-9". Baldwin SD-10 is 9'-6", Bosendorfer Imperial Grand is probably even larger and they sound large. That said as I've posted, 901 has other problems and also had to be re-engineered. M3.7's inability to reproduce the lowest octave means that it likely would not be able to reproduce the following instruments to my satisfaction; piano, tuba, string bass, bass drum, kettle drum, pipe organ. These very low frequency sounds give weight, power, and impact to music. Those with other priorities might find them perfectly fine and likeable.
  24. Faced with the same problem I'd build my own. I've considered converting AR9 to a direct/reflecting speaker by adding three LMRs and three UMRs per channel facing backwards and upwards (I've got a zillion 3/8" polydomes for tweeters) but I decided this would be a major project redesigning AR9 literally from the ground up. The direct reflecting principle results in the same kind of sound field a planar dipole large surface array equivalent produces although I require vertical dispersion as well. Combining ideas from AR9, LST, and 901 in a single package with my own ideas thrown in to boot. A retirement project.
  25. I hope and expect this will turn out to be a fine speaker Roy and his wife will enjoy for many years to come. IMO line arrays have inherent advantages over point sources and surface arrays have advantages over line arrays. Dipole speakers have advantages over monopole speakers. However, positioning and room acoustics are critical to obtaining the best performance. In their own way these speakers will require more experimentation with positioning and listener location than AR9 does. I'm not so sure other than that ribbon or membrane speakers really have advantages over conventional dynamic drivers. There certainly are disadvantages to them.
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