AR 9 and the anechoic chamber: An Out-of-Room Experienc...

[tysontom]

>Of course my main intention is to quantify if there are gross

>anomalies in the components of the crossover circuits and

>therefore a real need to change the capacitors. If I modify my

>approach, and play the frequencies from my computer through my

>amplifier to the "speakers" with a 4 ohm test load, would that

>be sufficient to identify any anomalies in the crossover

>components?

What makes you think that there are "gross anomalies in the components of the crossover circuits, that there a real need to change the capacitors?" Are you hearing gross distortion, or has the output of a driver fallen off significantly or stopped, or something to that effect?

The reason I ask that is that in the case of the AR-9 and AR-90, which are essentially identical except for about 1/3-octave of low bass, these speakers underwent exhaustive development and testing that lasted for over two years or so, and involved a large number of engineers -- both here and in England -- and the full resources of Acoustic Research, then a division of Teledyne, Inc. No expense (in practical terms) was spared, and except where it made no audible or measureable difference, no compromise was made in component materials, such as capacitors, resitors, coils and so forth used in the crossover. AR used extensive computer modeling, for the day, and many hundreds of hours of anechoic- and reverberant-test-chamber testing. I visited AR in Norwood during that period (around 1977) and saw an unusually large number of engineers and technicians hovering around a test AR-9 that was being put through its paces in one of the testing labs. It was at this particular time being tested for maximum power-handling and so forth, for its music-power and maximum-power rating. There was a large rack-mounted Hewlett-Packard 1000 or 3000 system computer (remember, this was in 1977, and this was state-of-the-art) that was connected to it. I was not allowed in the lab (I could see through a window) since the AR-9 had not yet been introduced), but there was a tremendous effort being put forth. In the AR Archives are dozens of test reports and frequency-response curves of all descriptions, including experimental crossover components and such, different crossover frequencies, and the justification and compromises of why the company used the components and crossover frequencies that they did. The operative word is "compromise," because a lot of that is necessary in the design of loudspeakers. There are trade-offs.

What I suggest is that you think carefully about making too many changes to the original design, unless you are willing to accept changes that may or may not improve the performance of the speaker system. Using heavier wire or perhap newer high-dollar capacitors will not hurt anything, but it will probably not make a measurable or audible difference, either, no matter how much you want it to. "Audible" is meant in the context of double-blind verification, not personal preference.

If you change the crossover frequencies, you are really "dancing with the devil," because in the end you will cause compromises that you probably did not see or visualize. For example, changing the 8-inch crossover so that it goes higher to prevent distortion in the 1-1/2-inch midrange tweeter is probably a big mistake. First of all, the resonance of the 1-1/2-inch driver is well down below the AR-9's crossover point for it, so it is well within its comfortable operating range. It also has much higher power-handling capability than with its use in the 3-way versions that use this driver. Secondly, the 8-inch driver is optimized for dispersion at its upper frequency, and to cross it over higher will make it directional, and this will adversely affect the off-axis smoothness, power response and ultimately affect the accuracy of the AR-9 or AR-90.

>I assume I could prepare a theoretical frequency response

>curve, in Excel, for the crossovers feeding a 4 Ohm resistor

>for comparison. (If the original frequency response curves of

>the crossovers ONLY, were available, and the test load used

>stated, a direct comparison with the original could be made).

"If the original frequency response curves of the crossover ONLY, were available, and the test load used stated...." There really is no such animal, because the crossover is composed of inductive-reactive-resistive elements, which include the speakers themselves. A resistive test load will not simulate the crossover.

>The CD I'm using is the Denon Audio Technical CD which they

>state is produced from a "high precision digital 16bit signal

>generator controlled by a computer and recorded in digital

>form onto the compact disc". Of course I'm not trying to

>measure the sound pressure levels in a room, rather, if the

>crossovers are working close or near to specifications I'll

>leave the capacitors alone and consider the other improvements

>mentioned elsewhere in the forum.

>

Again, what are you trying to accomplish? Do you suspect that the crossover is defective? Are you hearing distortion? You could take each capacitor out of the crossover circuit and test it separately to see if it is within spec, but unless you are hearing some major distortion, drop-outs from one or more drivers, etc., then the crossover might be okay.

--Tom Tyson

[rrcrain]

All you would prove by this mathimatical calculation is that the original values were correct. As far as I'm aware, no one has ever suggested otherwise. What your proposed test will not take into consideration is the known effect that age and time have on electrolytic capacitors and old capacitors in general.

If you compare the crossovers in the AR9 and AR90, they are exact except for the bass section. I can speak from first hand knowledge that the capacitors do drift with time and worse, start to leak rather badly; Bad enough that the upper midrange drivers in my AR90s had all but gone dead (silent, no sound reproduction)due to bad capacitors.

[Rlowe]

Tom, my “search” for a problem with my AR90s begins when I try to hear the same sound I’d previously heard from a set of AR38s’s. The AR38s seemed to provide better clarity in definition when listening to two violins playing in opposite speakers. I didn’t have to concentrate to identify the instrument sounds or pin-point their source in the soundstage. With the AR90’s I have to concentrate more and they are not as clearly separated or pinpointed in the soundstage as with the AR38s’s.

Also, believe it or not, I don’t think the “swell/envelope” of a Cello sound as the note reaches its final volume, on a low note, sounds as “tight?”/”realistic?” as I recall on the AR38s.

Do you have any comments?

With reference to your questions. There is nothing to suggest “gross anomalies” in the speakers. I was trying to suggest that the test I wanted to create need only be rough enough to pick up major anomalies IF they existed in the capacitors, without having to take them out of the cabinet.

I’ll leave any comment on changing the design to Sean.

By the way, I wasn’t contemplating changing the speaker design, I was focusing on upgrading the capacitors, if I could find a good reason. As you say I could take each capacitor out of the crossover circuit and test it separately to see if it is within spec.

Would you like to expand on your comment that most “changes will probably not make a measurable or audible difference, no matter how much you want it to”.

I have also attached 2 JPGs from an AR advertising brochure associated with this topic.

Richard

[Rlowe]

I could not see the attachments so I've tried again. Hopefully they'll be there. They don't show on the Preview. What am I doing wrong?

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Looked at Preview, no attachments.

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[tysontom]

>Tom, my “search” for a problem with my AR90s begins when I

>try to hear the same sound I’d previously heard from a set of

>AR38s’s. The AR38s seemed to provide better clarity in

>definition when listening to two violins playing in opposite

>speakers. I didn’t have to concentrate to identify the

>instrument sounds or pin-point their source in the soundstage.

>With the AR90’s I have to concentrate more and they are not as

>clearly separated or pinpointed in the soundstage as with the

>AR38s’s.

>Also, believe it or not, I don’t think the “swell/envelope” of

>a Cello sound as the note reaches its final volume, on a low

>note, sounds as “tight?”/”realistic?” as I recall on the

>AR38s.

>

Richard, I think that part of what you might be hearing in the AR-38's greater clarity or detail is the 4-inch midrange, which covers a broad, critical spectrum from 650 Hz to 3500 Hz, I believe, whereas in the AR-90 this frequency is covered by two drivers, the 8-inch lower-midrange and the 1-1/2-inch upper-midrange. Part of the cello's frequency band, as well as violins to some extent, would fall into this single-driver's frequency band. The four-inch driver is very flat and uniform in its range, and it does not suffer from any interference effects or lobing or whatever with the crossover. This characteristic would only be noticeable if you were listening relatively close to the speakers in the near field vs. listening back in the reverberant field. In other words (and I hate to say it), the AR-38 probably "images" somewhat better than the AR-90, but that is about it. It does not produce nearly as wide and uniform acoustic-power output as the AR-90. The AR-90 should exhibit a more spacious sound field well back in the listening room because of its superior dispersion in that frequency range. Lower-midrange and uppper-midrange frequency sounds would be more evenly dispersed through the AR-90 than the AR-38.

Also, if you can get the chance to compare the two speaker systems side-by-side, with equalized output levels, that would be helpful, too. You should try listening (1) up close in the so-called "sweet spot," and then (2) well back in the room. You might be able to identify this characteristic in a A/B comparison.

>With reference to your questions. There is nothing to suggest

>“gross anomalies” in the speakers. I was trying to suggest

>that the test I wanted to create need only be rough enough to

>pick up major anomalies IF they existed in the capacitors,

>without having to take them out of the cabinet.

>I’ll leave any comment on changing the design to Sean.

>By the way, I wasn’t contemplating changing the speaker

>design, I was focusing on upgrading the capacitors, if I could

>find a good reason. As you say I could take each capacitor out

>of the crossover circuit and test it separately to see if it

>is within spec.

>

I thought from reading your post (although not carefully enough it seems) that you might be suffering some drop-outs from your drivers, or distortion or whatever. If in doubt, of course, you have little choice but to (1) remove the capacitors and measure them individually or (2) take acoustic measurements of the loudspeaker to see if the output is uniform. The latter test is not easy, of course, unless you have a lot of acoustic-measuring instruments and access to anechoic chambers or gaited-measuring devices.

>Would you like to expand on your comment that most “changes

>will probably not make a measurable or audible difference, no

>matter how much you want it to”.

>

Yes, what I am saying here is that the use of heavy, pure copper or silver cable in lieu of the standard 16- and 14-ga stranded-copper wiring in the speaker crossover and cabinet will probably not make a measureable, let alone audible difference in the sound of the speaker. The runs are just too short, and there is no scientific basis for changing out the cable. In the case of the capacitors, somewhat more is at stake, of course, but I contend that the bi-polar electrolytic capacitors AR used are very high-quality units, and aside from eventually starting to leak or break down over time (not too likely), these caps are not known to cause trouble or introduce distortion or problems. Some people have complained about them, but I have not encountered many problems with them because they are so conservatively rated.

If you have doubts, your best bet is to check each capacitor individually. The same is true of the drivers: make certain that none of the drivers has been over-driven. An over-heated voice coil could cause a driver to distort even though it still works.

>I have also attached 2 JPGs from an AR advertising brochure

>associated with this topic.

I could not get these images to load properly.

--Tom Tyson

[Rlowe]

Tom, Thanks for the comments. A small point, I think the first part of your comment is refering to the AR48s as you mention the 4" speaker. The AR38s has 1X 10" and 1 X 1 1/4" liquid cooled CONE high-range driver, its crossover point is 2000Hz. I was always amazed at he high frequency dispersion in the room from the cone speaker.

I'll try a again to load the pictures.This time I watched the modem activity. So if it works I should have given it more time before. I didn't notice any acknowledgement by the Dialog that the file had been "attached". Is that a system feature? I did use the preview function but it didn't show the attachments at the time I looked at it. Oh Well!

Richard

[tysontom]

>Tom, Thanks for the comments. A small point, I think the

>first part of your comment is refering to the AR48s as you

>mention the 4" speaker. The AR38s has 1X 10" and 1 X 1 1/4"

>liquid cooled CONE high-range driver, its crossover point is

>2000Hz. I was always amazed at he high frequency dispersion in

>the room from the cone speaker.

I was actually referring to the AR38B, which was a 3-way with the 8-inch woofer, 4-inch midrange and 3/4-inch tweeter. I am actually a little out of my element when the "s" versions are brought into play.

>

>I'll try a again to load the pictures.This time I watched the

>modem activity. So if it works I should have given it more

>time before. I didn't notice any acknowledgement by the Dialog

>that the file had been "attached". Is that a system feature? I

>did use the preview function but it didn't show the

>attachments at the time I looked at it. Oh Well!

Well, at least you can get part of the image to load. I can't even get that far. Mine says it is downloading the file, but nothing actually downloads to the forum server.

--Tom Tyson

[Guest Sean]

"If you change the crossover frequencies, you are really "dancing with the devil," because in the end you will cause compromises that you probably did not see or visualize. For example, changing the 8-inch crossover so that it goes higher to prevent distortion in the 1-1/2-inch midrange tweeter is probably a big mistake. First of all, the resonance of the 1-1/2-inch driver is well down below the AR-9's crossover point for it, so it is well within its comfortable operating range. It also has much higher power-handling capability than with its use in the 3-way versions that use this driver. Secondly, the 8-inch driver is optimized for dispersion at its upper frequency, and to cross it over higher will make it directional, and this will adversely affect the off-axis smoothness, power response and ultimately affect the accuracy of the AR-9 or AR-90."

Tom, in this same post, you stated that the AR 8" woofer was used quite successfully at higher frequencies than what are being used in the AR-9. As such, either AR was selling smaller speakers that they new were poorly designed / suffered from a major compromise or the small crossover change that i suggest ( 250 - 500 Hz ) is not as big of a deal as you make it out to be. This would move the crossover point of the 8" / dome mid up to appr 1500 - 1700 Hz or so, which is still well below the point that these 8's were used in other designs.

As a side note, you either lack technical understanding of speaker design or are overlooking several very simple yet well known factors that contribute to the sound of a speaker under heavy load. Even though a speaker may resonate well below the point of actual use due to being crossed over, the break-up characteristics of the driver at or above those frequencies surely do come into play. This has to do with several factors with the first one being the fact that the passive crossovers used in 9's are not of a "brick wall" filter slope. That means that the driver is trying to reproduce energy at or near its' point of resonance, even though it may be measurably down in amplitude.

Now take that a step further and start pumping some big power into a driver ( ANY driver ). As the voice coil heats up, the electro-mechanical parameters of the driver change. The first things to change are the point of resonance and the Q*. Both of these go up, bringing the driver's point of resonance, along with all of the negative aspects of this part of operation, along with it. As such, the harder that you drive the speaker, the closer the driver comes to resonating at the point of crossover. While the point of resonance may ( should ) still remain well below the hinge point, the break-up characteristics with their resultant output of the driver start to come into play in greater fashion. That is because every note generated by the driver consists of a fundamental and multiple harmonic overtones. As such, the primary point of distortion / self oscillation in the driver, which is the point of resonance, may not come into play but all of those lovely harmonics do. As such, the harder that you push the driver, the more primary and secondary distortion that you get out of it. Hence the apparent "break-up" of a driver as "dynamic compression" and "overload distortion" come into play.

Given that most listening is done with very low power levels applied, one has to wonder how much AR concentrated on system analysis using hundreds of watts of applied drive power. We know that they did testing with levels of at least 6 watts steady state as they provide at least one specification for this. Above this level, only those involved with the testing of this speaker know exactly what is going on in that area. My comments are based on listening tests using very high grade components and other comparably well designed speaker systems.

Given the fact that i did make mention of the high frequency limitations within the 8" driver itself in previous posts on this forum, I may have taken for granted that others were already familiar with these comments. As such, i tried to clarify that by mentioning the change in crossover frequency i was discussing was minimal at best as far as the 8" driver was concerned. At the same time, the small change in frequency would limit the required excursion of the dome mid, increase power handling, reduce thermal stress and keep this driver further away from its' own natural "break-up" frequencies. Since all of these things are beneficial to the operation of the dome mid and the 8" driver is kept measurably below the 2000 Hz crossover point used in other AR designs, those driving the 9's quite hard might benefit from such a change. Given that the 9's are more likely to be used with very high powered amplifiers in larger rooms than any other AR product, the benefits obtained from such a change would "probably" FAR outweigh the drawbacks, if any. Should i continue to have problems "popping" upper mids, i'll either resort to doing exactly what i've mentioned here or replacing the stock AR mid-dome with that of a more robust design. Sean

>

* This applies to not only the mid-dome being discussed here, but also that of woofers. By AR using a lower Q to start off with, by the time that the woofers have begun to heat up and rise in Q, the Q is still quite reasonable and lower than most other designs. While this retains a more accurate presentation, it is the reason that many others find the bass on AR designs to be "dry" or "over-damped". They are simply used to a woofer / speaker design that doesn't take into account the rise in Q, giving them a far greater increase in apparent bass as the speaker is driven harder.

[Guest Sean]

Bose 901's work best in a live room because they lack high frequency response and articulation. This has to do with the fact that they use too large of a driver for the task at hand, their radiation characteristics at higher freq's are not conducive to flat response due to comb-filtering and much of their response at these frequencies consist of cone break-up and distortion. Placing them in a "dead" room only sucks up more of the reverberant high frequency energy, further compounding the problem.

As a side note, this was a speaker designed by someone that knew just enough to be dangerous. While ambient sound reproduction is part of what we hear, it surely isn't 89% of it. The designer chose operating parameters that results in SO many other problems that the end result is a mess. Not only does this design require equalization to achieve any type of linearity in terms of frequency response, it also requires a great deal of power due to the massive low frequency boost involved. On top of that, the time & phase response of this design, which places 9 drivers in series, all radiating at various angles from the seated listening position, is nothing short of a disaster.

Like i said, it is a sow's ear. It has some valid ideas that are / were very poorly implimented. If you like this design, more power to you. The fact that you have to "re-invent" this speaker and use design / driver attributes that go against the majority of design principles that were originally thought to be this speakers "strong points" should tell you something. That is, it should tell you how "under-whelming" and "under-designed" this product really was to begin with. Sean

>

[Guest Sean]

This is very similar to what i did with my 9's and 90's i.e. used Solen's and Kimber. It would appear that great minds think alike : ) Sean

[rrcrain]

I've been asked by the local audiophile shop to describe the difference the new crossovers made in my AR90s. The best I can do to describe in words is that perhaps it sounded as if a sheet of plastic was removed from in front of both speakers. Another metaphore is to compare the before and after sound to cut glass and fine cut crystal. Both are pretty and look good, but the crystal just has a brilliance and clarity that can't be matched by plain glass.

Sonically, the first thing I noticed whs that I could plainly understand lyrics in a song that was previously intelligable if I concentrated on it. Overall, detail, clarity, and definition were dramatically improved, yet they still sound like AR90s.

I use two Heathkit AA-1800s to drive them in a bi amp configuration. Yes, one does drive both quite well, but I discovered that biamping them with the old crossovers vastly improved the sound quality, and both amps tended to run on the upper end of warm. Since I've built and installed the new crossovers, each amp almost runs dead cold. I now have to PUSH them HARD to get either one to get warm to the touch, and at this volumn, my ears are starting to complain. I'm assuming this change is a direct result of reduced leakage through the new caps versus the old, original caps.

[soundminded]

>Bose 901's work best in a live room because they lack high

>frequency response and articulation. This has to do with the

>fact that they use too large of a driver for the task at hand,

>their radiation characteristics at higher freq's are not

>conducive to flat response due to comb-filtering and much of

>their response at these frequencies consist of cone break-up

>and distortion. Placing them in a "dead" room only sucks up

>more of the reverberant high frequency energy, further

>compounding the problem.

>

>As a side note, this was a speaker designed by someone that

>knew just enough to be dangerous. While ambient sound

>reproduction is part of what we hear, it surely isn't 89% of

>it. The designer chose operating parameters that results in

>SO many other problems that the end result is a mess. Not

>only does this design require equalization to achieve any type

>of linearity in terms of frequency response, it also requires

>a great deal of power due to the massive low frequency boost

>involved. On top of that, the time & phase response of this

>design, which places 9 drivers in series, all radiating at

>various angles from the seated listening position, is nothing

>short of a disaster.

>

>Like i said, it is a sow's ear. It has some valid ideas that

>are / were very poorly implimented. If you like this design,

>more power to you. The fact that you have to "re-invent" this

>speaker and use design / driver attributes that go against the

>majority of design principles that were originally thought to

>be this speakers "strong points" should tell you something.

>That is, it should tell you how "under-whelming" and

>"under-designed" this product really was to begin with. Sean

>>

I am sorry to say that I can't agree with many of the points you make including the general thrust of your arguement. This was a very interesting and unique idea which has found wide appeal for over 35 years although its market focus shifted away from audiophiles and toward a different segment of the audio market.

The problem of lack of high frequency reproduction is not due to the size of the driver but its mass. Because of the limitations of the strength of materials, inorder for four inch drivers to be stong enough to produce sufficient sound at low frequencies, their mass is so high that their inertia makes it impossible to overcome it at high frequencies with additional equalization and electrical power. Unlike direct radiating speakers, the high frequency dispersion of the front firing driver does not limit the overall power radiating capabilities of the system at high frequencies. I'd bet that at 12 Khz, Bose 901 has far better dispersion than any direct firing loudspeaker made. Unfortunately, at higher frequencies, the output of the system drops off rapidly.

Since the speaker is intended to reflect 89% of its radiated energy off walls, non reflective surfaces near the speaker reduce its special attributes at all frequencies significantly.

It would be naive and foolish for anyone to dismiss the knowledge of a PHD of electrical engineering and acoustical science who is also a professor at MIT. While I might question or disagree with some of his conclusions, I have great respect for his academic accomplishments.

The relative amounts of sound that is direct versus reflected at any given seat in a live performance depends on the acoustics of the room and the seat you are sitting in. In Dr. Bose's white paper, he stated that at 19 feet from the performing stage at Boston Symphony Hall, America's finest acoustical space for performance of music (Leo Baranek's opinion, not mine) he measured that 89% of the sound was reflected and 11 % was direct. In the graphs in his paper, he showed quite clearly that the percentage of reverberant sound continued to increas as you went further back in the hall. Even at 89%, the decrease in sound pressure level were the direct field eliminated would be well under one decibel. I have explained elsewhere that the time distribution and spatial relationships between direct and reverberant fields produced by BOSE 901 in a home and the corresponding relationship produced by musical instruments in a concert hall have little in common so I won't say any more. That being said however, the spatial radiating characteristics of Bose 901 are far more similar to most musical instruments than most direct firing loudspeakers produce.

The requirement for equalization and electrical power to get a loudspeaker to perform as desired is not a valid issue or detriment. In many recording studios, their monitors are equalized and frequently checked and adjusted using spectrum analyzers and calibrated microphones to assure the flattest response. The cost of electrical power in audio amplifiers is not the significant issue it once was.

There is no evidence that so called time aligned speakers sound any better or more accurate than identical speakers which are not time aligned. The fact is that for the front radiating driver, there is a direct correlation between frequency response and phase response. For a single driver, this is actually much better than the comparable phase delays for multiple driver systems due to different group delays and the fact that they are displaced from each other causing constructive and destructive interference patterns around there crossover frequencies. As for the indirect sound, you have exactly the same situation as with the indirect sound of live instruments. I don't see this as an issue either. What some proponents of time aligned speakers claim is that it provides better "imaging" meaning that the musical instruments seem to be spread out across an imaginary stage. Bose 901 accomplishes this by virtue of its spatial radiating pattern.

Practically all great speakers get "reinvented" AR303 is a reinvention of AR3a which was a reinvention of AR3. So what? The disappointment for me is that the concept was never developed to exploit its potential as an audiophile loudspeaker. The concept had much to offer but its commercial success is owed to its development along other lines.

[Guest Sean]

>The problem of lack of high frequency reproduction is not due

>to the size of the driver but its mass.

Size has a lot to do with frequency response, especially when using multiple drivers to share the load. There are such things as comb filtering, etc.... that take place. ALL of these things make up what we hear, not just amplitude linearity.

>Unlike direct

>radiating speakers, the high frequency dispersion of the front

>firing driver does not limit the overall power radiating

>capabilities of the system at high frequencies. I'd bet that

>at 12 Khz, Bose 901 has far better dispersion than any direct

>firing loudspeaker made.

Don't put money on it. I've got a speaker that fires directly at me, wherever i'm sitting. Not only does it radiate 360* horizontally, it has a wider range vertically than a 901 does.

Unfortunately, at higher

>frequencies, the output of the system drops off rapidly.

This is not only mass coming into play here, there is nulling of the signal due to cancellation taking place. Due to the time / phase differences from driver to driver and the wavelengths involved at high frequencies, the out of phase signals cancel each other out, causing massive high frequency roll off / lobing. This does not take place nearly as severely at lower frequencies because the wavelengths are longer i.e. less interference with each other. While cancellation of this type is gradual, combining the reduced output from roll-off / cancellation with the increased mass leaves us with a non-linear radiator and the need for a band-aid aka "equalization".

>Since the speaker is intended to reflect 89% of its radiated

>energy off walls, non reflective surfaces near the speaker

>reduce its special attributes at all frequencies

>significantly.

Once again, you generalize without stating facts. Reflections are far more likely to effect tonal balance at mid to high ranges. Given the indirect dispersion characteristic of sound as frequency is reduced, low frequencies are less apt to be "effected" in comparison to mid and treble response.

>It would be naive and foolish for anyone to dismiss the

>knowledge of a PHD of electrical engineering and acoustical

>science who is also a professor at MIT. While I might

>question or disagree with some of his conclusions, I have

>great respect for his academic accomplishments.

I make my living by correcting the design work of EE's, ME's and other "certified brain surgeons" that have a "piece of paper" from some school. "Valid ideas" that get "poorly implimented" don't excite me or make me want to show respect for those that didn't follow such ideas through to a logical conclusion. Having said that, Bose are the kings of mass-market delusion and profit margin.

That being

>said however, the spatial radiating characteristics of Bose

>901 are far more similar to most musical instruments than most

>direct firing loudspeakers produce.

I will agree with you to a certain extent. Once again though, we may have different ideas as to what you mean by "direct firing".

>The requirement for equalization and electrical power to get a

>loudspeaker to perform as desired is not a valid issue or

>detriment. In many recording studios, their monitors are

>equalized and frequently checked and adjusted using spectrum

>analyzers and calibrated microphones to assure the flattest

>response. The cost of electrical power in audio amplifiers is

>not the significant issue it once was.

This is true to a certain extent. Then again, when we are talking about the massive amount of EQ and power required to obtain deep bass response at high amplitude using a series of small drivers in a very small cabinet, we aren't exactly talking about trying to "correct for minor deficiencies" or "gradually" increasing the amount of power required.

>There is no evidence that so called time aligned speakers

>sound any better or more accurate than identical speakers

>which are not time aligned.

BWA-HAHaha.... You need to listen to a point source time and phase coherent full range speaker ala Soundlab's, Ohm A's, Ohm F's, etc... driven by high quality, wide bandwidth, low negative feedback audio gear. If that isn't enough evidence for you, i can understand why you are still messing with 901's.

The fact is that for the front

>radiating driver, there is a direct correlation between

>frequency response and phase response. For a single driver,

>this is actually much better than the comparable phase delays

>for multiple driver systems due to different group delays and

>the fact that they are displaced from each other causing

>constructive and destructive interference patterns around

>there crossover frequencies.

Poor designs don't take into account the radiation pattern of multiple drivers. As a side note, 901's are a perfect example of what you talk about here. They are STRICTLY based on driver over-lap, time & phase delays, destructive interference patterns, etc... This makes them everything that a knowledgeable audiophile DOESN'T want.

>As for the indirect sound, you

>have exactly the same situation as with the indirect sound of

>live instruments. I don't see this as an issue either.

WRONG!!! WRONG!!! WRONG!!!

An instrument produces an equal amount of in phase and out of phase information as it is played. Depending on one's position in relation to that instrument, it is possible to alter that ratio. Given that 901's start off with 89% of the information out of phase, you are screwed from the get-go.

> What

>some proponents of time aligned speakers claim is that it

>provides better "imaging" meaning that the musical instruments

>seem to be spread out across an imaginary stage. Bose 901

>accomplishes this by virtue of its spatial radiating pattern.

What Bose 901's do is provide a small percentage (11%) of focused energy, therefore everything becomes "diffuse" aka "spread across an imaginery stage". If you heard someone playing an instrument in a room, you could point in the general direction that the sound was coming from. That is, unless the room was quite large and extremely "live" in terms of acoustics. That has to do with the time, phase, quantity and spectral content of what you were hearing. 901's distort EVERY aspect of that equation due to their design i.e. you have more indirect sound focused in the opposite direction than you do direct sound. You can no longer localize the image because "89%" of the sound is "sprayed" in the opposite direction and is 180* out of phase with the primary source i.e. "11%" direct radiated energy.

>Practically all great speakers get "reinvented" AR303 is a

>reinvention of AR3a which was a reinvention of AR3. So what?

>The disappointment for me is that the concept was never

>developed to exploit its potential as an audiophile

>loudspeaker. The concept had much to offer but its commercial

>success is owed to its development along other lines.

Bose stopped trying to market to "audiophiles" because it doesn't meet the criteria that most audiophiles value i.e. accuracy. Having said that, please don't go off on some tangent equating "accuracy" with "amplitude frequency response linearity". That is but ONE part of a very large equation. Without the EQ, the 901 wouldn't even do very well in that category either.

On top of that, Bose made the speakers flimsier ( plastic rather than wood ), less controlled with poorer transient response ( vents always introduce transient problems ), cheaper to produce / distribute ( reduced weight due to cheaper and lighter materials ) and increased their profit margin with every new incarnation. As such, Bose has nothing to offer anyone that understands and appreciates product design and integrity and they have gone out of their way to demonstrate that fact. Their products are under-designed, ill-concieved pieces of crap that are nothing more than gimmicks designed to take a LOT of your hard-earned money. Bose thinks so much of their own products that they won't even provide you with ANY type of specifications. Who needs quality control when not even the manufacturer has standards to measure the products by??? J-U-N-K !!! Sean

>

[Guest Sean]

I do not doubt your experience one bit. It is much the same thing that i experienced. The greater sense of "flow" and "ease of presentation" is pretty amazing. The speakers are FAR more open sounding and no longer have the "stifled" or "tilted down" tonal balance that most older AR's present. The amount of air, detail and resolution that can now "sneak through" the speaker is amazing. At the same time, the details are presented quite naturally, with no sense of fatigue or "hi-fi etchings" that many other "audiophile" type speakers that are known for being "detailed" bring with them. I'm glad that someone else has both experienced the benefits to these type of mods AND taken the time to share those results with others. Sean

>

[soundminded]

Sean, I am really disappointed and overwhelmed with your diatribe. I just don't understand it. What I do understand is that there is so much disagreement between us that I feel it is pointless for me to discuss this any further here. I cannot find one statement you made in your long posting that I can agree with so I will just leave it at that.

[tysontom]

>I do not doubt your experience one bit. It is much the same

>thing that i experienced. The greater sense of "flow" and

>"ease of presentation" is pretty amazing. The speakers are

>FAR more open sounding and no longer have the "stifled" or

>"tilted down" tonal balance that most older AR's present. The

>amount of air, detail and resolution that can now "sneak

>through" the speaker is amazing. At the same time, the

>details are presented quite naturally, with no sense of

>fatigue or "hi-fi etchings" that many other "audiophile" type

>speakers that are known for being "detailed" bring with them.

>I'm glad that someone else has both experienced the benefits

>to these type of mods AND taken the time to share those

>results with others. Sean

>>

>

Sean,

You really should consider departing this forum. In my opinion you exhibit no objective, scientific knowledge (in your ramblings) on the subject of amplifiers and loudspeakers. I think that "a little bit of knowledge can be a dangerous thing" describes some of your ludicrous postings. It's really a distraction, because this forum is devoted to people who want to share, contribute and learn more about this topic of AR speakers. If you listened, and took note of what some of the members are trying to say, you might gain a little knowledge for yourself in this subject.

--Tom Tyson

[Guest Barrydor]

>Listening to speakers outdoors -- unless you hoist the speaker

>up on a platform 30 feet in the air, or bury them flush in the

>ground, and you get up in the air on-axis to listen -- is not

>truly an anechoic experience.

Like this?

Barry

http://www.arsenal.net/dc/user_files/131.jpg

[rrcrain]

Tom,

Sean's reply to my post was curteous and beyond reproach.

Now, concerning Sean's and Soundman's ongoing discussion. I have refrained from becoming embroiled in their discussion simply because I see merit in both of their points of view and fervently believe both to be equaly right.... and wrong.

There are as many opinions on what constitutes a decent stereo system as there are ears in this world. Generally, we can agree on a limited chriterion and thats just about it. The scientific mind sees only hard cold facts and figures; if it can't be mathimatically proven, it ain't so. Generally, these people could be classified as the "C" type personality. Cold facts please. Others fervently believe what they hear in spite of the facts and are not going to be swayed by any scientific evidence you present. Simply, they "know" what they hear. These generally are the "S" personalities. Those are gross generalizations only, don't take them for gospel.

Consider the reality that we possess only two ears which easily allows us to discern sounds eminating froum our right, left, or in front of us nad all variants inbetween. Yet, we are capable of identifying sounds that originate from behind us. A sound eminating 5 feet behind us will take the same amount of time to reach both ears as a sound eminating from the same distance dead in front of us. Why or how can we do this? Darned if I know, but I know we can.

The audio engineers of old assumed many things concerning the limits of human hearing, many of which are only now begining to be challenged.

Above all, be slow to anger, quick to forgive and always be willing to listen patiently to even a fool, for they still have a story to share.

Richard Crain

[tysontom]

>

>Tom,

>

>Sean's reply to my post was curteous and beyond reproach.

>

>Now, concerning Sean's and Soundman's ongoing discussion. I

>have refrained from becoming embroiled in their discussion

>simply because I see merit in both of their points of view and

>fervently believe both to be equaly right.... and wrong.

>

>There are as many opinions on what constitutes a decent stereo

>system as there are ears in this world. Generally, we can

>agree on a limited chriterion and thats just about it. The

>scientific mind sees only hard cold facts and figures; if it

>can't be mathimatically proven, it ain't so. Generally, these

>people could be classified as the "C" type personality. Cold

>facts please. Others fervently believe what they hear in spite

>of the facts and are not going to be swayed by any scientific

>evidence you present. Simply, they "know" what they hear.

>These generally are the "S" personalities. Those are gross

>generalizations only, don't take them for gospel.

>

>Consider the reality that we possess only two ears which

>easily allows us to discern sounds eminating froum our right,

>left, or in front of us nad all variants inbetween. Yet, we

>are capable of identifying sounds that originate from behind

>us. A sound eminating 5 feet behind us will take the same

>amount of time to reach both ears as a sound eminating from

>the same distance dead in front of us. Why or how can we do

>this? Darned if I know, but I know we can.

>

>The audio engineers of old assumed many things concerning the

>limits of human hearing, many of which are only now begining

>to be challenged.

>

>Above all, be slow to anger, quick to forgive and always be

>willing to listen patiently to even a fool, for they still

>have a story to share.

>

>Richard Crain

Richard,

Thanks for your message, and I agree with most of what you say. Regarding your last sentence, I can only say that a lot of the people here will not suffer fools gladly.

Certainly no one argues that audio -- especially loudspeakers -- can be an highly subjective and emotionally charged topic. Everyone has opinions, and that is certainly fine. But shouldn't we try to frame our opinions with some sense of decorum and moderation without trying to offend others? Beyond that, I think that what I most dislike is for someone to get off on a tangent and attempt to disparage well-known and accepted contributions to high fidelity. The following statement (Sean) about the Bose 901 is a good example of what I mean:

"...As a side note, this was a speaker designed by someone that knew just enough to be dangerous. While ambient sound reproduction is part of what we hear, it surely isn't 89% of it. The designer chose operating parameters that results in SO many other problems that the end result is a mess. Not only does this design require equalization to achieve any type of linearity in terms of frequency response, it also requires a great deal of power due to the massive low frequency boost involved. On top of that, the time & phase response of this design, which places 9 drivers in series, all radiating at various angles from the seated listening position, is nothing short of a disaster."

Bose 901s are anything but perfect, but I would never consider that it was a poorly designed speaker or a "mess" or a "disaster." It's just the opposite, and was carefully researched and has been thoroughly documented in the literature. Who could legitimately argue that Dr. Bose is not an accomplished engineer and researcher?

--Tom Tyson

[charger3834]

Tom,

You have an academic style based on objective thinking that is very much in the grand tradition of AR Inc.

[ar_pro]

I always read Tom's posts...every single one - his insight & knowledge into our favorite speaker company is unique, and unparalleled. I also admire his writing skills - he can explain a concept, give practical advice, or provide details from AR history without condescension or high-handedness. I wish he would write a book.

This Bose business is about as close to discussing politics or religion that our group gets...for some reason, people become apoplectic over the 901, and emotions run high. Google up Bose on the audio newsgroups to get an idea of what went on there, and probably still does. Most of it is unreadable, having degenerated into insult and slander - things that would probably not occur in "meat-space", because someone would get decked!

Like most of us, I've listened to the 901, and it's just not my cup of tea. It is, however, a loooooong way from the worst speaker I've ever heard, and in no way represents criminal activity on the part of the manufacturer or dealer. The 901's pedigree is far beyond that of most current "manufacturers", who CAD up a box stuffed with OEM drivers in whatever alignment currently sells; and unlike much of this stuff, the 901 was designed and constructed based upon actual theory & experimentation. In an era when the digital manipulation of an audio signal was either impossible or excessively expensive, the 901 attempted to solve many issues of reproduction in an applied (mechanical) fashion, and that is just plain impressive.

I get a big kick out of this forum...it's of tremendous value to all of us who enjoyed products from AR's "glory days", are trying to keep classic models working well into this century, or who've stumbled across a pair of 2ax's at the local thrift shop, and just want to get them up & running. We're all friends, here.

[Guest Sean]

I agree that we disagree. That is why i responded step by step and presented various technical arguments and explanations. Vague generalizations based on personal attachment to a product can not make up for a lack of performance and technical competence. I've owned 901's ( 1st series ) and heard every series after that. I've also had 301's, 501's and 601's in the house. I've worked with a stack of 16 Bose 801's with their matching subwoofers doing Pro Sound reinforcement. I am well familiar with their products. That's why i have no respect for them. Sean

>

[Guest Sean]

Tom: I wrote out a VERY thorough reply to you. Unfortunately, it somehow "disappeared" in a computer glitch. I guess it wasn't meant to be.

Other than that, my "ludicrous" comments are based on years of experience as both an electronics professional and avid electroics consumer. I design / repair / modify electronics for a living. I have been employed by over a half dozen manufacturers as a design consultant for products that they manufacture. On top of that, i have worked in both the Pro Sound Reinforcement and Recording industries. I have five different and very elaborate audio systems set up in my house. If you want specifics, please let me know. I'll be glad to discuss them with you or anyone else that is interested. As a side note and for my own private use, i have probably bought and sold multiple hundreds of "high end" audio components in the last couple of years. All of this adds up to experience and exposure to various electrical designs and sonic presentations that many people will never get to experience for themselves.

I'm sorry if you don't agree with my point of view or can't understand / relate to some of my comments. I don't know if this has to do with your lack of education or experience in this field, but i can assure you that i'm not a "quack" or speaking about things that i don't know or understand. Should you want further references pertaining to my level of understanding and / or experience with electronics and audio in general, please do a search in the forum archives at Audiogon.

With that in mind, i ask that you respond to my response to you. This was post #3667 that i made on 03/08/04 in this thread. I was quite specific in my comments, so please feel free to correct any flaws that you find. You took the time to criticize some of my suggestions and for your convenience and edification, i clarified my previous statements. We can proceed from there should you find the time to respond. Sean

>

[soundminded]

I'm really not interested in a flame war and it seemed to me that this dialogue was headed in that direction.

I am always puzzled as to why this particular speaker and this particular company generates so much emotional reaction. I find it impossible to get worked up over any machine having dealt with so many of them over the years. It's just an inanimate object.

I'm sorry you didn't get as much enjoyment out of listening to your Bose 901s as I got out of mine. Although my preferences and opinions have changed over the years, I still look back with happy memories listening to recordings with them. It puzzles me also why, considering that you had no respect for the concpts or manufacturing quality of Bose products, you kept buying and using them. I'd think that after a bad experience with 901, which came on the market before the other lesser models, you would have avoided them for other manufacturers' products.

I don't think personal credentials or a resume should have any bearing on this kind of discussion but that arguements should stand or fall on their own merits. I don't feel people who may regard their own credentials as less impressive or accomplished should feel intimidated by others posting here. Besides, no matter how much you know or think you know, nobody has a monopoly on knowledge and there are always people out there who know much that you don't. The world wouldn't be a very interesting place if everybody agreed on everything.

I am always happy to discuss my opinions and experiences with Bose 901 or other equipment I've owned or used but not in the tone this discussion has taken.

[Guest Brian_D]

Sean's manor offends me and I have been reluctant to respond to any post with which he is involved, until now.

Tom Tyson, Ken Kantor, soundminded and the other very active members of this forum are well-repsected within this forum. They are respected for both their technical knowledge of the AR products, as well as their objective advice given freely and without regard to compensation or personal gain.

When the technical knowledge or comprehension of subject matter discussed within this forum is called into question by any member, a debate is likely to ensue. In most cases it's harmless banter or joking stabs but only by you, Sean, has this become a personal issue.

Comments elluding to the ignorance of our members should not be tollerated. Examples:

"...can't understand / relate to some of my comments. I don't know if this has to do with your lack of education or experience in this field..."

"...As a side note, this was a speaker designed by someone that knew just enough to be dangerous..."

"...I hope that this explains some of my previous statements in a manner that Ken and others can follow along with..."

And most disturbing:

"...i am generally loaded with "contempt" for most loudspeaker designs / designers..."

Maybe you didn't know, or perhaps you don't care, but Tom Tyson is a well respected speaker designer who worked for AR for some time. He is certainly considered the "AR Expert" within this forum.

Something to keep in mind when posting here is that we are AR fans. If you want to talk amplifiers, let's talk about the AR amplifier. If you want to talk Bose, go somewhere else. This is an AR forum for AR topics and AR products. I would not stand for the insult you have given the others on this forum, should those insults have been directed towards me.

I for one will not be taking part in any of Sean's discussions, nor will I be commenting further on this particular topic.

-Brian