Measuring the AR-3

[Turbon]

Hi.

Got myself interested in measurements so I am slowly buiding a stack of instruments to use.

So far:

Kenwood HM-250 distortion meter.

HP 3562A Dynamic signal analyser. (broken when bought - no display. Fuse in the display electronics was gone)

E-MU 0404 Usb audio interface.

@juli PCI sound card.

ARTA software.

Der EE DE-5000 LCR meter.

A bunch of MM's.

Some parts are still missing though before the measurements can take of. What microphone should I use? I'm an sucker for HP instruments so I added an 5335A frequency counter (I really don't need it but it is cool , bought as a broken unit - oxides and hard to press keys prohibited it from working - fixed). Still looking for cheap 339 and 8903 units. A better oscilloscope is also on the list. Probably an older HP or Tek mainframe with the right options, have to keep the appearence up :D.

I also bought an Trimble GPSDO to ensure that the reference frequensies are about spot on. I'm also looking into good enough voltage references as well but I'm not quite ready to buy anything now. Add a bunch of DIY static frequency sinus oscillorators with very clean outputs to set the baseline - the Philips does not count among these and so does not the built in source of the 3562A. 

[owlsplace]

Looks like you are mixing it up equipment wise -- Old School and New School.

Here is a mic: http://www.parts-express.com/dayton-audio-emm-6-electret-measurement-microphone--390-801

Software based spectrum analyzer is probably the way to go these days.

Have fun,

Roger

[Turbon]

Oh yes Roger. A total mixup. The industry is moving to computer based instruments. I have my doubts about the input attenuation and input amplification. How would one check if the values are real? HP's from the golden age are just so cool - built to last as heritage items. Sorry to say that knowledge about the instruments are speedingly forgotten. If someone here have information - please share on multiple sites.

Another project I have in mind is to crack the HP code in the 3562A. I believe it is mostly the same code as in the 3563A. Probaby the crack will be useful for decoding mst of the equipment of the age.

Regards

[tysontom]

On 4/2/2016 at 11:03 AM, Turbon said:

Oh yes Roger. A total mixup. The industry is moving to computer based instruments. I have my doubts about the input attenuation and input amplification. How would one check if the values are real? HP's from the golden age are just so cool - built to last as heritage items. Sorry to say that knowledge about the instruments are speedingly forgotten. If someone here have information - please share on multiple sites.

Another project I have in mind is to crack the HP code in the 3562A. I believe it is mostly the same code as in the 3563A. Probaby the crack will be useful for decoding mst of the equipment of the age.

Regards

One little minor suggestion: don't attempt to measure the AR-3's "frequency response" as a system.  It will tell you exactly nothing, even if you have an anechoic chamber.  The interference effects, phase issues, diffraction and so forth are extremely difficult to separate from true performance, especially with a speaker with wide dispersion.  Those measured anomalies will cancel themselves out once the sound is reflected energy back into the reverberant listening field. 

You should remove each driver (mid and tweeter) and measure them on a flat baffle in anechoic space (you could do it outside if you don't have an anechoic chamber or gaited measurement instruments) and measure them separately -- with the crossover in place -- to determine if they are performing correctly.  You could compare them to the calibrated measurements AR did through the years to determine if the drivers are working okay.  You could also measure the woofer in a near-field environment with the microphone very close to the woofer cone's dust cap, and you could get an idea of how it is doing compared with the original.  It would be better, of course, to measure the woofer at one meter, facing into 180-degree solid angle, to get a proper idea of its performance now, compared with the original measurements.

Finally, the best way to determine the performance of the AR-3 is to measure it in a reverberant test chamber.  This, of course, is not easy to do without the chamber itself, but this testing shows a composite picture of the total energy -- acoustic power -- that the speaker puts into a room and what is actually heard. The acoustic-power response is a sum of all of the energy radiated from the speaker and reflected back into the room. 

1.  This is one of AR's early reverberant test chambers to measure the total radiated energy from the speaker.  Over 1000 speakers of all types were tested in this chamber and other AR chambers. 

2.  This is the reverberate-chamber response of one of the AR 3-way systems, measured above 1 kHz.  Note the uniform overall energy being radiated into the chamber.  The speaker is placed inside the door of the chamber, and the microphone (B&K condenser measurement microphone) is placed behind the speaker.   

3. Measurements of AR-3 drivers in one of AR's anechoic chambers and woofer in open field, facing into 180-degree solid angle. 

4. AR-3 laboratory and free-field response measurements, showing the extremely fine, linear performance, on- and off-axis of the drivers measured individually in an anechoic chamber.

—Tom Tyson

 

 

[DavidDru]

Turbon,  My tech here in Boise used to work for HP back in the day that testing equipment was built and of course he has it all and then some.  He probably built a lot of it back in his HP days and he has said the same thing.  They were built to last a long time. (Yes, we've had many interesting conversations about caps.)

Is there something I can ask him for you concerning the code?  I don't know exactly what you are referring to or about but I can convey info if helpful.

[tysontom]

I worked for Hewlett-Packard for 28 years, and I can tell you that HP equipment (test equipment and otherwise) was built to a higher standard than just about any competitive equipment in the field, anywhere.  All HP products for many years were heavily strife-tested, drop-tested, salt-spray tested and accelerated MTBF tested.  To have this level of reliability, these products were built with gold-plated circuit boards with conformal coating (tropicalization) and 100% incoming tested components.  All machine screws were stainless-steel Pozidriv units, and most chassis components were based on the corporate chassis (various versions) with cast-aluminum side rails and anodized-aluminum side pieces, etc.  Few other companies made equipment like this to meet this level of reliability.  Of course, HP equipment cost more, too, but if it was a better product, justification could be made by the buyer to purchase more reliable, long-lasting equipment that would result in lower "life-cycle" costs over time!

--Tom Tyson

Construction of a Hewlett-Packard 3312A Function Generator.  Note the aluminum frame, gold-plated boards, etc.

Top view of 3312A showing the gold-plated board, aluminum rails and premium components.  All parts were 100% incoming-tested for conformity.  HP later pioneered in the use of surface-mount component technology, which followed this generation of products a few years later.

 

[Sonnar]

20 hours ago, tysontom said:

One little minor suggestion: don't attempt to measure the AR-3's "frequency response" as a system.  It will tell you exactly nothing, even if you have an anechoic chamber.  The interference effects, phase issues, diffraction and so forth are extremely difficult to separate from true performance, especially with a speaker with wide dispersion.  Those measured anomalies will cancel themselves out once the sound is reflected energy back into the reverberant listening field. 

You should remove each driver (mid and tweeter) and measure them on a flat baffle in anechoic space (you could do it outside if you don't have an anechoic chamber or gaited measurement instruments) and measure them separately -- with the crossover in place -- to determine if they are performing correctly.  You could compare them to the calibrated measurements AR did through the years to determine if the drivers are working okay.  You could also measure the woofer in a near-field environment with the microphone very close to the woofer cone's dust cap, and you could get an idea of how it is doing compared with the original.  It would be better, of course, to measure the woofer at one meter, facing into 180-degree solid angle, to get a proper idea of its performance now, compared with the original measurements.

Finally, the best way to determine the performance of the AR-3 is to measure it in a reverberant test chamber.  This, of course, is not easy to do without the chamber itself, but this testing shows a composite picture of the total energy -- acoustic power -- that the speaker puts into a room and what is actually heard. The acoustic-power response is a sum of all of the energy radiated from the speaker and reflected back into the room. 

1.  This is one of AR's early reverberant test chambers to measure the total radiated energy from the speaker.  Over 1000 speakers of all types were tested in this chamber and other AR chambers. 

2.  This is the reverberate-chamber response of one of the AR 3-way systems, measured above 1 kHz.  Note the uniform overall energy being radiated into the chamber.  The speaker is placed inside the door of the chamber, and the microphone (B&K condenser measurement microphone) is placed behind the speaker.   

3. Measurements of AR-3 drivers in one of AR's anechoic chambers and woofer in open field, facing into 180-degree solid angle. 

4. AR-3 laboratory and free-field response measurements, showing the extremely fine, linear performance, on- and off-axis of the drivers measured individually in an anechoic chamber.

—Tom Tyson

 

 

Tom, do You have the reverberate-chamber response of AR 3 vs. AR 3a?  Thank You, Adriano

[tysontom]

Adriano, I have seen it, but I can't find a copy of it.  I think I have it somewhere, but for the life of me I can't locate it in the AR files.  I do remember that the response was very similar, but the dispersion advantage of the AR-3a seemed to be a slight advantage, as expected, in the acoustic-power response.  There was a bit more energy at the very high end, but not by much.  Differences between these two speakers becomes less noticeable once you are back in the reverberant field, but I still prefer the clarity and smoothness of the AR-3 a bit over the AR-3a, though either speaker could sound better than the other in A-B comparisons (as AR used to point out to listeners in the AR Music Rooms).   

--Tom

[Sonnar]

Thank You Tom. Now I'm in front of a pair of AR 3 and a pair of 3a , in A -B comparison, listening to Mozart's Eine Kleine Nachtmusik, DGG , Wiener Philarmoniker, James Levine. Both superlative speakers, but I agree with You , I prefer the AR 3's clarity and smoothness over the better dispersion of the 3a. However , I still have a doubt about more energy in the very high-end . To me AR 3's tweeter shows more presence and definition , but probably the better off-axis response of AR 3a could offer the impression of a more " open " sound .  Adriano 

[Turbon]

On ‎2016‎-‎05‎-‎17 at 1:37 PM, DavidDru said:

Turbon,  My tech here in Boise used to work for HP back in the day that testing equipment was built and of course he has it all and then some.  He probably built a lot of it back in his HP days and he has said the same thing.  They were built to last a long time. (Yes, we've had many interesting conversations about caps.)

Is there something I can ask him for you concerning the code?  I don't know exactly what you are referring to or about but I can convey info if helpful.

Hi David.

I would like to have the source codes for the 3562/3A dynamic distortion analyzers:) and information about the hardware differences in HP part numbers:)

If source code is impossible - then the binaries for burning the eproms for 3563A would be nice.

Regards

[Turbon]

On ‎2016‎-‎05‎-‎20 at 4:54 PM, Turbon said:

Hi David.

I would like to have the source codes for the 3562/3A dynamic distortion analyzers:) and information about the hardware differences in HP part numbers:)

If source code is impossible - then the binaries for burning the eproms for 3563A would be nice.

Do not put energy into this. I'll play with the equipment for a while and refurbish what I find refurbishable. I will probably pass them on when done with the units. Sometimes I loose my bearing of striving for the best sound for me - and that is something only my ears can decide :D. 

Regards

 

[Turbon]

On 24 maj 2016 at 5:13 PM, Turbon said:

I will revert to ARTA - a microphone and the placeholders will be gone. They are nice indeed.

[tysontom]

On 5/18/2016 at 0:32 PM, Sonnar said:

Thank You Tom. Now I'm in front of a pair of AR 3 and a pair of 3a , in A -B comparison, listening to Mozart's Eine Kleine Nachtmusik, DGG , Wiener Philarmoniker, James Levine. Both superlative speakers, but I agree with You , I prefer the AR 3's clarity and smoothness over the better dispersion of the 3a. However , I still have a doubt about more energy in the very high-end . To me AR 3's tweeter shows more presence and definition , but probably the better off-axis response of AR 3a could offer the impression of a more " open " sound .  Adriano 

Adriano,

The AR-3 super tweeter actually has a bit more sensitivity (and and thus output) than the AR-3a tweeter.  The 3a is certainly better in off-axis response, and this gives it a slight edge in overall power response and "spaciousness," but the AR-3 tweeter is somewhat better matched in output to the midrange and woofer.  

Certainly, the AR-3 super tweeter and midrange are as good as it gets in terms of transient response and smoothness, on- and off-axis, and this is very important. The AR-3 super tweeter is also completely flat and peak-free within its operating range, its only drawback being its larger size than the AR-3a tweeter and thus somewhat less output off axis.  The differences are never great.  In my experience, the AR-3 is slightly less "spacious" or 3-dimensional than the AR-3a, but I've always felt that the AR-3 seemed more neutral and natural-sounding by never calling attention to itself!  

The AR-3 was considered the finest loudspeaker money could buy for perhaps ten years after it was introduced, and it is still today considered one of the great achievements in the advancement of loudspeaker technology!

--Tom Tyson 

[Sonnar]

18 hours ago, tysontom said:

Adriano,

The AR-3 super tweeter actually has a bit more sensitivity (and and thus output) than the AR-3a tweeter.  The 3a is certainly better in off-axis response, and this gives it a slight edge in overall power response and "spaciousness," but the AR-3 tweeter is somewhat better matched in output to the midrange and woofer.  

Certainly, the AR-3 super tweeter and midrange are as good as it gets in terms of transient response and smoothness, on- and off-axis, and this is very important. The AR-3 super tweeter is also completely flat and peak-free within its operating range, its only drawback being its larger size than the AR-3a tweeter and thus somewhat less output off axis.  The differences are never great.  In my experience, the AR-3 is slightly less "spacious" or 3-dimensional than the AR-3a, but I've always felt that the AR-3 seemed more neutral and natural-sounding by never calling attention to itself!  

The AR-3 was considered the finest loudspeaker money could buy for perhaps ten years after it was introduced, and it is still today considered one of the great achievements in the advancement of loudspeaker technology!

--Tom Tyson 

Thank You, Tom , I 've ever thought AR 3's tweeter was more sensitive , linear and extended , and sometimes I' m wondering about its transparency  and smothness . It' s absolutely better than every high-quality Seas or Scan-Speak 1" modern tweeter. 3a 's tweeter shows a clear and progressive roll-off , and obviously the powerful midrange assumes primary importance. Someone used to this sound could easily mistake a better linearity for a midrange weakness. Adriano

[tysontom]

17 hours ago, Sonnar said:

Thank You, Tom , I 've ever thought AR 3's tweeter was more sensitive , linear and extended , and sometimes I' m wondering about its transparency  and smothness . It' s absolutely better than every high-quality Seas or Scan-Speak 1" modern tweeter. 3a 's tweeter shows a clear and progressive roll-off , and obviously the powerful midrange assumes primary importance. Someone used to this sound could easily mistake a better linearity for a midrange weakness. Adriano

Adriano,

There is also the issue of aging for these tweeters and midrange drivers.  Ironically, the AR-3a 1-1/2-inch midrange driver is very consistent and shows no deterioration over the years (if the crossover is okay), as it has no foam suspension parts or butyl-rubber sealing, etc.  It has a coating over the entire cloth dome, but no suspension or damping materials made from foam.  It has fiberglass both under and above the dome for damping.  However, the AR-3a tweeter often deteriorates over time, and it's sometimes difficult to determine if one has gone bad without measuring the output.  The foam under the dome often deteriorates (but not always), and the foam suspension is prone to the same fate.  The AR-3 foam suspension is slightly different and doesn't seem to go bad as readily; however, the 2-inch midrange drivers with the added white butyl substance show the effect of that material hardening over time, thus reducing the output.  I've noticed this on quite a few midrange drivers, especially the later ones with the smaller pole-piece magnet.  Roy C has worked on some of these drivers and removed the material improved the output sensitivity.  As for the 1-3/8-inch super-tweeter's issues, the big one seems to be the tendency to "pop" out of the gap for some tweeters, caused by the constant pressure under the dome.  Most later versions of the midrange have fiberglass above the dome that offsets the pressure under the dome, but the tweeter doesn't have it.  

These changes to the AR-3 were the result of work done by Roy Allison in the early 1960s, and these were small, incremental improvements at the time, but the materials are less stable over long periods.  The earliest AR-3 2-inch midrange drivers are less prone to this condition.  

--Tom Tyson

 

[Sonnar]

I 've seen AR 3's tweeter popped out , unfortunately it happens to a friend of mine . My four AR 3 shows sparkling highs, and I hope they will last until my death ! I can' t detect any weakness in the midrange , if it were it would be easily recognizable playing piano, strings, horns or percussions. AR 3's tonal balance reminds me Bowers & Wilkins 801 , excellent , neutral mids and vivid and shiny highs : however , AR 3 shows better bass. I use very often AR 3 listening to Miles Davis 's electric period , 1968-1975, and these speakers offer me the most transparent and detailed rendering I 've ever heard from a dynamic loudspeaker . Probably they 're better when new, but they' re still great even today. My best wishes, Adriano 

1 hour ago, tysontom said:

Adriano,

There is also the issue of aging for these tweeters and midrange drivers.  Ironically, the AR-3a 1-1/2-inch midrange driver is very consistent and shows no deterioration over the years (if the crossover is okay), as it has no foam suspension parts or butyl-rubber sealing, etc.  It has a coating over the entire cloth dome, but no suspension or damping materials made from foam.  It has fiberglass both under and above the dome for damping.  However, the AR-3a tweeter often deteriorates over time, and it's sometimes difficult to determine if one has gone bad without measuring the output.  The foam under the dome often deteriorates (but not always), and the foam suspension is prone to the same fate.  The AR-3 foam suspension is slightly different and doesn't seem to go bad as readily; however, the 2-inch midrange drivers with the added white butyl substance show the effect of that material hardening over time, thus reducing the output.  I've noticed this on quite a few midrange drivers, especially the later ones with the smaller pole-piece magnet.  Roy C has worked on some of these drivers and removed the material improved the output sensitivity.  As for the 1-3/8-inch super-tweeter's issues, the big one seems to be the tendency to "pop" out of the gap for some tweeters, caused by the constant pressure under the dome.  Most later versions of the midrange have fiberglass above the dome that offsets the pressure under the dome, but the tweeter doesn't have it.  

These changes to the AR-3 were the result of work done by Roy Allison in the early 1960s, and these were small, incremental improvements at the time, but the materials are less stable over long periods.  The earliest AR-3 2-inch midrange drivers are less prone to this condition.  

--Tom Tyson