Need replacement for AR9 upper midrange part 200028.

[RoyC]

I've had the opportunity to dissect a number of these 4 ohm midrange drivers within the past couple of years.

To summarize my observations:

-The dimensions of the parts going back to the introduction of the cloth dome mid are the same.

-Prior to the rear terminal versions used in the AR-11/10pi and last 3a/LST, the roll suspension was inverted and more compliant. Later versions are less compliant, having more heavily treated rolls. The AR-9 series mids' rolls appear to be the most heavily treated and least compliant...hence the higher resonant frequency.

-The front-wired version has very thin leads running through the inverted roll to the voice coil coil. Later versions all have significantly thicker tinsel lead running under a heavily treated suspension roll.

-The 200028 and 200032 are virtually identical. No differences could be observed, including the amount and placement of ferro-fluid in the voice coil gap. (It should be noted that the 200028 mid is listed as a replacement for the 200032 mid in AR's 1986 parts list.)

-Dcr of front-wired versions is  2.5 ohms, and all rear terminal versions around 3.2 ohms.

-ALL of the above mids from earliest to later have fiberglass packed under the dome with the exception of the 200044.

-Typical issues being found are broken/worn leads at the domes of the front-wired version, and low to variable output due to congealed ferro-fluid in AR-9 series mids.

Roy

[DavidR]

I took a look at the1986 parts list in the library here and couldn't find anywhere it mentioning replacements.

I do have this on my hard drive:

Logic would say its the other way and I believe your previous post(s) state this as well. Also Carl measured the resonance and the 028 has 1/2 the resonance of the 032. The 028 won't play low enough for the AR91 and 92 and the 032 could burn out the vc if used in an AR9 or 90 when played hard.

[RoyC]

"Logic would say its the other way and I believe your previous post(s) state this as well. Also Carl measured the resonance and the 028 has 1/2 the resonance of the 032. The 028 won't play low enough for the AR91 and 92 and the 032 could burn out the vc if used in an AR9 or 90 when played hard."

OK, David...I see where only the 9 and 90 are listed. Later replacement guidance from AR in the early 90's actually recommended a universal Tonegen replacement for all models.

Whatever the case may be, I can't verify the small difference in the amount of ferro-fluid between these drivers, but I can tell you they are otherwise identical. Saying the 200032 cannot be used due to concern over burning out the voice coil is not something I would worry about in the least. In fact, there is a much greater possibility of problems and discrepancies from decades old ferro-fluid than anything else. I know you are an advocate of the Midwest replacement mid, and it does look like a promising universal replacement, but are you sure you want to recommend it with no AR technical papers or parts lists to refer to?

Btw, I'm not sure what posts you are referring to. In the past I've mentioned using all of these mids interchangeably in all models. Given the ever-diminishing numbers of original used replacements, it is fortunate any of the above work as well as they do. 

Roy

[soundminded]

The existing midrange works perfectly 99.99 percent of the time. Is it worth $200 for that extra .01 percent? Nah. Not really. My favorite turntable in the whole world is on sale in mint condition on ebay for $4000. I bought one around 1983 for around $250 still in mint condition and the factory offered me a brand new one for $450 but I didn't take it. I really wouldn't mind having another one now even though I listen mostly to CDs. But I've got about 3000+ vinyls. Do I really need another one? I've got other turntables too. Nah, not really. Even I have some commons sense.... sometimes. Crazy what people are paying these days for so called high end audio equipment. Glad I'm not an audiophile anymore. Do i use that well suspended turntable that copied the AR turntable suspension with AR9s? No, the bass of AR9 is so powerful it even knocked the laser off the track on some recordings on my old Denon CD player. Funny how you can buy a Wilson Alexandria speaker for $175,000 and then they want to sell you $40,000 subwoofers. I led a bass deprived childhood. That's what I call child abuse. AR9 has been making up for it for 37 years. Can't get enough of that bass. Incredible. IMO it does everything in the bass right. 

[Pete B]

On 1/26/2022 at 10:01 AM, teknofossil said:

Hey there Pete! Those were the 200032 mids. These are the ones intended for the AR91 that used a 700hz LF to mid crossover point.

That makes a lot of sense, I've mentioned this before but worth going over again.

What we now call a Linkwitz-Riley 4th order crossover is the cascade of two 2nd

order Butterworth (Q=.707) filters.  Some refer to them as Butterworth Squared crossovers:

https://www.aes.org/e-lib/browse.cfm?elib=3287

More on LR crossovers:

https://www.ranecommercial.com/legacy/note160.html

It seems that the AR engineers figured this out sometime before the LR paper was published

since in the AR-3a/AR-11 we see an XO around 500 Hz with the mid having an Fc also close to that.

Based on your measurements the AR-91 with a 700 Hz crossover also has the mid with an

Fc very close to the XO point.

Closed "box" dome drivers have a 2nd order highpass electro-acoustical transfer function

and tuning that properly with a 2nd order crossover can provide a nearly ideal 4th order LR XO.

You measured a slightly low Qtc but keep in mind that any resistance in the crossover to the

dome mid will raise Qtc.

[Aadams]

1 hour ago, Pete B said:

It seems that the AR engineers figured this out sometime before the LR paper was published

since in the AR-3a/AR-11 we see an XO around 500 Hz with the mid having an Fc also close to that.

Does this explain why the chart below appears to show a 24db/octave curve for the mid

[DavidR]

Roy, I did find it odd that the 032 tweeter and AR91 and 92 don't appear on that 1986 parts list. At least I was unable to find it.

[Pete B]

7 hours ago, Aadams said:

Does this explain why the chart below appears to show a 24db/octave curve for the mid

Yes exactly,  12dB/oct for the midrange and 12 dB/oct for the XO, cascaded (complex multiply or add dB s).

For an ideal LR it should be 6 dB down at the crossover point.

[Pete B]

By the way, I studied that curve over 15 years ago and simulated the crossover in LAUD pointing 

out to the board that the system input impedance did not simulate correctly with the 2.85 mH

woofer inductor, rather something like 1.9 mH was required.  We finally determined that early

AR-3a s had the 1.9 mH inductor, most of the later production had the 2.85 mH.   Roy pointed out

that he had worked on systems with both values.

It was not easy to find this thread, and note that one of the forum updates scrambled the order

of old threads:

https://community.classicspeakerpages.net/topic/1270-anyone-have-ar-3a-measurements-system-drivers/

Note that there is peaking at the top of the woofer's response, I believe that the 2.85 mH should

eliminate that and provide 1-2 dB more baffle step.

[Stimpy]

On 1/24/2022 at 3:15 PM, soundminded said:

I need a replacement upper midrange for AR9 part 20028. Anyone know of a source or know of one for sale. Thanks in advance. 

I had this UMR ad flagged, and forgot all about it.  It's for a NOS 028 mid.  A little pricey, but since it's been up for a while, I would think you could get it a little cheaper.

200028 DOME

[soundminded]

14 hours ago, Pete B said:

By the way, I studied that curve over 15 years ago and simulated the crossover in LAUD pointing 

out to the board that the system input impedance did not simulate correctly with the 2.85 mH

woofer inductor, rather something like 1.9 mH was required.  We finally determined that early

AR-3a s had the 1.9 mH inductor, most of the later production had the 2.85 mH.   Roy pointed out

that he had worked on systems with both values.

It was not easy to find this thread, and note that one of the forum updates scrambled the order

of old threads:

https://community.classicspeakerpages.net/topic/1270-anyone-have-ar-3a-measurements-system-drivers/

Note that there is peaking at the top of the woofer's response, I believe that the 2.85 mH should

eliminate that and provide 1-2 dB more baffle step.

Somewhere in the back of my cluttered mind I recall being confused about the AR3a crossover frequency being 475 hz and 425 hz from different sources. Did it change at some point during production? It always seemed to me that most loudspeaker drivers have a usable range of about 2 1/2 to 3 octaves but the full audible range is 10 octaves. Therefore in a 3 way system something's gotta give. For most speakers it's the bottom octave. But for AR3 and its derivatives it was the octave between the woofer and the midrange. This is why some people say AR5 was in some ways better than AR3a, it sacrificed some of the lowest octave to be a better match between the woofer and midrange.

 

AR 9 was for me AR throwing in the towel on the 3 way design for achieving its goal by adding a 4th driver. Problem solved. In fact many problems solved. I wondered how other people did it. I never heard Infinity IRS but it seemed to me by using a large number of midrange ribbon drivers Arnie Nudell had solved it that way. The servo woofers crossed over at 100 hz. In IRS Beta he added a lower midrange driver because he didn't have many of his EMIM midrange ribbon drivers that IRS V had. But Paul McGowan who restored a pair admitted many shortcomings of IRS V and one was 100% harmonic distortion at some frequencies in the woofer midrange crossover region. Apparently he had a lot of arguments with Nudell about among other things including the quality of the woofers. Nudell used 6 cheap 12" woofers per channel in a sealed enclosure. In a posting about the servo system design Bascom King who designed the servo amplifier showed the open loop response of the woofers to have a resonant peak at 60 hz, suboptimal by AR standards. Small wonder the servo amplifier had to be 2000 watts. Only one driver had an accelerometer sensor for the servo circuit, the rest being assumed to have identical response. 

This brings up another very funny thought for me about how many audiophiles change their minds  about their theology over time. In that example McGowan went from line source good to line source not necessary. Servo good to servo not necessary. Tubes bad to tubes good for input stages. Nudell's last effort before he passed away he called the IRS killer had a very similar woofer and lower midrange driver as AR9. Two side firing woofers and a front firing 6' lower midrange which was going to be replaced by an 8". However, Arnie passed away, McGowan hired a new guy and PS Audio's first speaker called FR30 is nothing at all like anything Arnie Nudell ever did. He will begin marketing it shortly. I think it will sell for around $20K a pair. 

 

[Aadams]

56 minutes ago, soundminded said:

Somewhere in the back of my cluttered mind I recall being confused about the AR3a crossover frequency being 475 hz and 425 hz from different sources. Did it change at some point during production? It always seemed to me that most loudspeaker drivers have a usable range of about 2 1/2 to 3 octaves but the full audible range is 10 octaves. Therefore in a 3 way system something's gotta give. For most speakers it's the bottom octave. But for AR3 and its derivatives it was the octave between the woofer and the midrange. This is why some people say AR5 was in some ways better than AR3a, it sacrificed some of the lowest octave to be a better match between the woofer and midrange.

3a 575hz  and 525hz

This thread is drifting BUT the 3a vs 5 vs LST vs AR9 mid range clarity topic was aired out about three years ago.  The AR3a is equal to the AR5 and AR9 in mid range clarity if it is optimally placed in relation to the listener’s position. For the 3 or 3a this means you start by recessing in a bookcase or a wall.  Roy Allison wrote a paper explaining the problem after he left AR.  Almost any other practical placement of a 10 octave, front facing, three way is a compromise and often results in mid range “suck out” due to cancellations from boundary reflections if the woofer is also reproducing mid-range frequencies.   This research led to the Allison 1 and the AR9. 

Welcome Back

Adams

 

[soundminded]

1 hour ago, Aadams said:

3a 575hz  and 525hz

This thread is drifting BUT the 3a vs 5 vs LST vs AR9 mid range clarity topic was aired out about three years ago.  The AR3a is equal to the AR5 and AR9 in mid range clarity if it is optimally placed in relation to the listener’s position. For the 3 or 3a this means you start by recessing in a bookcase or a wall.  Roy Allison wrote a paper explaining the problem after he left AR.  Almost any other practical placement of a 10 octave, front facing, three way is a compromise and often results in mid range “suck out” due to cancellations from boundary reflections if the woofer is also reproducing mid-range frequencies.   This research led to the Allison 1 and the AR9. 

Welcome Back

Adams

 

 

Allison's work was IMO brilliant and AR9 solved the problem of suckout too. Few other manufacturers to this day have managed to solve it. In fact they don't even understand it. Here's an example of a $109,000 speaker system. Compare figures 2 and 3. The suckout is about a 10 to 15 db drop between 50 and 150 hz, a loss of 90% of energy.  Would you trade AR9 for this? I wouldn't. IMO AR9 beats the hell out of this. https://www.stereophile.com/content/wilson-audio-specialties-alexx-loudspeaker-measurements

To make up for the lack of deep bass AR9 can produce, this manufacturer wants to sell you an additional $40,000 of subwoofers. 

 

[fedeleluigi]

On 1/27/2022 at 5:11 AM, RoyC said:

Later replacement guidance from AR in the early 90's actually recommended a universal Tonegen replacement for all models.

Roy, would you mind sharing these documents with the community? I do think that every member of this forum will thank you. Me first!

Thank you

[RoyC]

On 2/3/2022 at 6:51 AM, fedeleluigi said:

Roy, would you mind sharing these documents with the community? I do think that every member of this forum will thank you. Me first!

Thank you

Sorry, fedeleluigi, There are no documents to share. The information was based on phone conversations with AR (then in Benicia, CA) and AB Tech in late 1993. There were two versions of the mid available at that time. One had a screen and one did not, and I was told they were internally identical. The mid with the screen looked like the one used in the AR-3a Limited. The one without the screen had no plastic ring, and looked like the one used in the earlier Cello Amati. I was also told these were "suitable" for use in any AR model equipped with a dome mid (including the AR-5 and LST 2 with the addition of a series resistor of 2.5 to 3 ohms). These were obviously not original, and were all that was available...but I was never concerned about using them in the vast majority of speakers I have repaired in the absence of the original mid.

Some additional thoughts regarding this thread and similar threads:
-It should be noted that I have never seen a burned voice coil in an AR dome mid from any era, mostly worn/broken leads at or under the dome.

-Any iteration of later mid from the AR-11 onward was built more robustly than all earlier versions. Resonant frequencies were controlled by suspension treatment and fiberglass under the dome.

-Obviously finding a properly functioning original driver is always desirable, but in my opinion, the distinction between "absolutely original" and "suitable" for a satisfactory, near-original (and often indistinguishable) solution should be made to avoid undue concern on the part of an inexperienced person. This should be considered when discussing other components such as capacitors, resistors, etc, as well. Discussions in these matters are always interesting, but speaking in absolute terms can be unnecessarily misleading.

-A good example of the above is the subject of L-pads vs AR pots. I have never seen a burned out L-pad in an AR speaker, and Ebay's "Vintage_AR" has sold over 2500 L-pads to date with no reported issues. On the other hand, I have seen many AR pots with melted plastic shafts. Despite this, there is a guy on Ebay hawking $30 per pot replacements using (L-pad) scare tactics to sell them. (With that said, our own JKent is providing the same replacement pot at near cost to forum members...message him for details!)

Roy

 

 

 

[fedeleluigi]

On 2/4/2022 at 11:39 PM, RoyC said:

Sorry, fedeleluigi, There are no documents to share. The information was based on phone conversations with AR (then in Benicia, CA) and AB Tech in late 1993.

Roy, thanks very much for replying and clarifying;

 

On 2/4/2022 at 11:39 PM, RoyC said:

There were two versions of the mid available at that time. One had a screen and one did not, and I was told they were internally identical. The mid with the screen looked like the one used in the AR-3a Limited. The one without the screen had no plastic ring, and looked like the one used in the earlier Cello Amati.

As far as I know, after stopping in-house production of its 1-1/2 in. midrange (p.n. 200010-1), AR supplied a similar unit manufactured by Tonegen as a replacement part. Until circa 1990/early-1990s the part number of the Tonegen midrange was 1210010-1. Then the part number changed to 1210010-1A and this number was kept until the end of the production (around the mid 90's) of the drivers with screen and fiberglass pad in front of the fabric dome.

The Tonegen 1210010-1 and 1210010-1A  midranges were aesthetically practically identical and frankly I don't know what was the real reason for the change of the part number. BTW, in the same period also the Tonegen 12"  woofer used as replacement part for AR-3a, LST, 10 Pi, 9, 9LS etc. changed its part number from 1-2100030B or 1210003-0B to 1210003-2A.

As said, both of 1210010-1 and 1210010-1A  midranges had the screen and fiberglass pad in front of the fabric dome like the original AR 200010-1 midrange.

Later, before its final closure (which occurred around the mid-90s),  Tonegen produced the latest 1-1/2 inch midrange (p.n. 1210010-3A). It was used both by AR as a spare part and by CELLO for its latest loudspeakers using Tonegen components (CELLO switched to Dynaudio drivers when Tonegen closed down). As said, the part number of this latest 1-1/2 inch midrange made by Tonegen was 1210010-3A. It was basically the same midrange as before but lacked the distinctive screen and fiberglass pad of the original AR 200010-1 midrange.

So, it was the latest CELLO Amati, Stradivari Master and Grand Master and not the early ones to use the Tonegen midranges without screens (1210010-3A).  The last picture shows this.

Mark Levinson (who had founded CELLO Ltd. in 1984), one of the most skilled marketing strategists in the HI-End world, said that these latest AR midranges were an evolution and sounded better than their predecessors. Note that at the time no one (except industry operators) was aware of Tonegen and that the drivers used in these very expensive and made in USA loudspeakers were actually manufactured in the East by Tonegen itself.

Personally, I think Tonegen was actually scraping the bottom of the barrel and had no more screens available for that type of midrange as they were closing down. In other words, as far as I know, the 1210010-3A was the midrange of the last batches that Tonegen supplied to AR (and CELLO) through AB Tech and that was used while stocks lasted.

Obviously some vendors of AR replacement parts found themselves having both the old 1210010-1A and the new 1210010-3A in stock for some time. What I do know for sure is that, at some point, the official Italian distributor of AR (Arcona) stopped supplying the 1210010-1A midrange and started to supply only and exclusively the 1210010-3A midrange while stocks lasted.

-

-

A young Mark Levinson with the early Cello Stradivari Grand Master using the Tonegen 1210010-1 or 1210010-1A midranges. Note the midrange screens and fiberglass pads.

[RoyC]

On 2/7/2022 at 12:05 PM, fedeleluigi said:

Roy, thanks very much for replying and clarifying;

So, it was the latest CELLO Amati, Stradivari Master and Grand Master and not the erlier ones to use the Tonegen midranges without screens (1210010-3A). 

Great summary, Fedeleluigi...

I should clarify that the only AR mids I have found in Cellos were US-made drivers. I just meant that the screen-less Tonegen drivers looked like them. Unless you know differently, I believe the Dynaudio mid driver (and tweeter) were being used in the Cello by the time the Tonegens showed up (?).  Either way, the Tonegen drivers would have been replacements for the earlier version of the Cello Amati...which would have been equipped with AR-11/10pi era drivers.

Additionally, all iterations of the Tonegen mid have a bronze colored magnet. The magnet is also a tiny bit wider than any iteration of the AR manufactured mid I have seen, requiring a slight widening of earlier cabinet (ie AR-3a) holes to fit properly.

Whatever other reasons AR had to change driver part numbers, cosmetic differences were among them from what I have seen.

Roy