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Restoring the AR-3a


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#21 Guest_pbda_*

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Posted 09 March 2009 - 12:29 PM

A fantastic resource. Thanks to the authors, and to Mark.

#22 mike tarelli

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Posted 05 July 2009 - 07:58 PM

Thanks to all concerned for this great document. As a direct result of it I have refoamed my early AR11s,had their cabinets re-polished,refoamed my AR3a improved,had their cabinets re-veneered and found out they were wired incorrectly(AR3a improved crossover schematic) bought a pair of AR6 to re-foam and re- veneer and thoroughly enjoyed myself!
Thanks again.
Mike.

#23 Dan Skye

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Posted 09 August 2009 - 02:50 AM

I think it's time we have a pinned topic for the "Restoring the AR-3a" document developed by six of our esteemed members - Roy Champagne, Ken Kantor, Minh Luong, John O’Hanlon, Bret Thiel, and Tom Tyson. The document is available here:

http://www.classicsp...ring_the_ar-3a/

Per John's suggestion, I have put a counter on this page (available when I run statistics) so we can see how popular this document becomes.

If you have feedback on the document and how it has impacted your restoration project, please reply to this thread.

Mark

Just want to let it be know how much I appreciate having the resoration guide It is exectionally well done
Hope to see more on AR 3' too: I am develloping a massive crush on these orange eyed beasts.They are quite different in many ways.
Prof' Dan Skye

#24 Guest_goldeneye57_*

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Posted 21 August 2009 - 08:02 PM

Hello!!! Is the first time I send a message to You. I have to thanks You for the marvellous AR3 AR3a Restoration PDF. Now I have to ask You a question:
I have a couple of AR3a of 70', I have a midrange broken so I have request two sobstitute to AB-TECH Services but I have also the two frames with clots very, very old and ruineds, so I have bought new clots (lambswool linen near Arezzo near Roma, my home) but I have read in Your file PDF to sobstitute the old frames with masonite. Now that is an economical metod or someting to respect the original sound of AR3a??? It is not better doing them with a sheet of plywood of the same tickness, more easy to sagomate and refine???

#25 RoyC

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Posted 21 August 2009 - 09:04 PM

Hello!!! Is the first time I send a message to You. I have to thanks You for the marvellous AR3 AR3a Restoration PDF. Now I have to ask You a question:
I have a couple of AR3a of 70', I have a midrange broken so I have request two sobstitute to AB-TECH Services but I have also the two frames with clots very, very old and ruineds, so I have bought new clots (lambswool linen near Arezzo near Roma, my home) but I have read in Your file PDF to sobstitute the old frames with masonite. Now that is an economical metod or someting to respect the original sound of AR3a??? It is not better doing them with a sheet of plywood of the same tickness, more easy to sagomate and refine???


Hello goldeneye57,

On behalf of myself and the rest of the AR-3a Restoration gang, welcome to the CSP forum.

To answer you're question, plywood or other materials could be used for the grille frame and not affect the sound. Plywood may be more prone to warping.
The original 3a grille frame was constructed of a masonite type of material. Whatever you use, make sure it is a full 1/4" in thickness, so your staples don't pop through the other side when you attach the grille cloth.

More importantly, be aware that the current AB Tech replacement drivers are not the same as the originals. You would be better off finding used original midrange units. Of the original 3a drivers, they have held up the best over the years.

Roy
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#26 Tekker

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Posted 15 October 2009 - 02:18 AM

Hi guys,

This is my first post here, but I've been reading your very knowledgable posts for a couple of weeks now and have been perusing the rest of this great site for probably a couple of years. I recently downloaded the restoration document and gotta say it's fantastic. I would've been willing to pay some money for this. Many thanks to the authors for this wealth of info and advice.
I've had my pair of ARa's for maybe 35 years now and would like to give them a makeover. Can anyone recommend a one stop .source for for all these polypropylene caps and noninductive resistors? I see some negative comments on the Solens. Any others I should lean toward or away from?
Through my own calelessness I managed to blow both my tweeters. I read about the AB Tech replacements. Audio Proz has another replacement and a restorer in Albany, NY has another. There's also a New Jersey guy on Ebay who says he can rebuild the voice coils. Has anyone had any experience with these.

#27 Dan Skye

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Posted 15 October 2009 - 03:17 AM

Hi guys,

This is my first post here, but I've been reading your very knowledgable posts for a couple of weeks now and have been perusing the rest of this great site for probably a couple of years. I recently downloaded the restoration document and gotta say it's fantastic. I would've been willing to pay some money for this. Many thanks to the authors for this wealth of info and advice.
I've had my pair of ARa's for maybe 35 years now and would like to give them a makeover. Can anyone recommend a one stop .source for for all these polypropylene caps and noninductive resistors? I see some negative comments on the Solens. Any others I should lean toward or away from?
Through my own calelessness I managed to blow both my tweeters. I read about the AB Tech replacements. Audio Proz has another replacement and a restorer in Albany, NY has another. There's also a New Jersey guy on Ebay who says he can rebuild the voice coils. Has anyone had any experience with these.

Hi
I had good luck with Vintage AR from Albany recently(they live on Ebay) Larry is a good guy over there.
What type of"a's" do you run? I have it bad:I have snapped up 2 sets of 3-a's and one set of 3's(which I think are awesome)
Audioguy

#28 JKent

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Posted 15 October 2009 - 02:53 PM

Hi guys,

This is my first post here, but I've been reading your very knowledgable posts for a couple of weeks now and have been perusing the rest of this great site for probably a couple of years. I recently downloaded the restoration document and gotta say it's fantastic. I would've been willing to pay some money for this. Many thanks to the authors for this wealth of info and advice.
I've had my pair of ARa's for maybe 35 years now and would like to give them a makeover. Can anyone recommend a one stop .source for for all these polypropylene caps and noninductive resistors? I see some negative comments on the Solens. Any others I should lean toward or away from?
Through my own calelessness I managed to blow both my tweeters. I read about the AB Tech replacements. Audio Proz has another replacement and a restorer in Albany, NY has another. There's also a New Jersey guy on Ebay who says he can rebuild the voice coils. Has anyone had any experience with these.

Hi Tekker and welcome
RoyC will get back to you regarding his experience with replacement tweeters. He has done a LOT of research and I believe he has had very good results with inexpensive HiVi tweets, but I'll let him address that.

Partsexpress has Dayton caps, which many people like, but caps are sort of a religion and you will get many conflicting opinions. The originals were non-polarized electrolytics and therefore cheap NPEs should work just fine, but film caps will last much longer, and as I said many people will debate the relative merits of different caps endlessly.
PE has some real nice Mills resistors, or their standard Dayton line.

The recognized expert on rebuilding speaker drivers is Bill LeGall at Millersound but as I said, wait to hear from Roy. His HiVi solution may be perfect for you (or in the meantime check out this thread, especially page 2):
http://www.classicsp...r...eeter&st=20

good luck
Kent

J. Kent Hollingsworth

#29 RoyC

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Posted 15 October 2009 - 05:18 PM

Hi Guys,

As Kent mentioned, the HiVi Q1R http://www.parts-exp...tnumber=297-417, with an added small inductor in parallel (.05mh to .1mh), seems to be working out for a number of forum members. Madisound also sells the tweeter and inductor.

Ebay's "Vintage AR" is selling them already assembled, and drilled for the original screw holes, as a drop-in replacement for the original tweeter. You can check out his listing to see some photos.

Feel free to send me a PM if you have any questions.

Roy
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#30 Tekker

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Posted 15 October 2009 - 10:22 PM

Hi Guys,

As Kent mentioned, the HiVi Q1R http://www.parts-exp...tnumber=297-417, with an added small inductor in parallel (.05mh to .1mh), seems to be working out for a number of forum members. Madisound also sells the tweeter and inductor.

Ebay's "Vintage AR" is selling them already assembled, and drilled for the original screw holes, as a drop-in replacement for the original tweeter. You can check out his listing to see some photos.

Feel free to send me a PM if you have any questions.

Roy


Thanks Guys,

I really appreciate your help. Seems I've already got 2 votes for Vintage AR, and I live in downstate NY. I've been following his Ebay sales, but haven't spoken to him yet. I saw a response curve for an AR-3 with the AB tweeter mod in here somewhere and it was a thing of beauty. How do you feel the HiVi driver compares? Guess I can't lose for $22 without the coil. I actually think I've got a pair of original tweeters on the way, but as I've read here they're flaky at best and I want to be prepared. It's funny, but the speakers still sound good even without tweeters.
Thanks much for all the tips. I'll have to run them down and let you know how I'm making out.

Tekker Bill

#31 Tekker

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Posted 15 October 2009 - 10:35 PM

Hi
I had good luck with Vintage AR from Albany recently(they live on Ebay) Larry is a good guy over there.
What type of"a's" do you run? I have it bad:I have snapped up 2 sets of 3-a's and one set of 3's(which I think are awesome)
Audioguy



Hi Dan,

Between you, Kent and Roy I've some nice leads to follow up on. I'm familiar with VAR's ebay sales, but haven't dealt with him yet. Wanted to get some more info first.
I've owned my pair of AR3a's since about '73. They're family. I'd love to get some more to play with. Time will tell. My old Pioneer receiver is pretty played out, but a friend loaned me his Apt Holman pre and Bryston 2B amp and I think I've got the fever again.

Thanks for your help,
Tekker Bill

#32 Tekker

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Posted 19 October 2009 - 11:22 PM

Hi Guys,

I'm putting together my shopping list. Still torn about recapping. I have the original block caps and I don't believe they're electrolytics.
Going to bypass the tweeter replacements for now, as I bought 2 original used AR3a tweeters from Audio Proz. They arrived today and have cracks in the mounting ring, but I can work around that. The drivers work really well. He has others and tests them before sending them out. You can browse his site for inventory, but you have to call him to order: www.audioproz.com
Also you may want to check out this ebay link:
Tweeter repair
He says he can rebuild voicecoils on AR2ax, AR3 and AR3a tweeters for $40. I'm going to send him my 2 old tweeters with bad voice coils and I'll let you know how it goes.

Tekker Bill

#33 danajohnhill

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Posted 06 February 2010 - 03:59 AM

Allow me to add my voice to the chorus praising "Restoring the AR-3a". This document was my bible throughout my just-completed restoration of my AR-3as. When I got my speakers a couple weeks ago, the first thing I did was go in search of information. The restoration guide was absolutely indispensable for me. I have been telling everyone I know how helpful it was.

Everyone who refurbishes AR-3as probably has their own quirky experiences. I had one or two myself. If, down the road, you decide to amend the guide, I have a couple humble suggestions. Likewise, if anyone could benefit from the many detailed photographs I took during my project (I was working on 100% original 1969 AR-3as that had never even been opened), I'd be more than happy to share. The fact that this group exists to disseminate this information means that other people like me, who happen to luck upon these great old speakers, will have the resources they need to go forward with the project.

My copy of the guide is now filed away together with the original documentation that happened to come with my speakers. Whoever inherits my speakers ages hence will be glad to have it all.

Thanks again.

#34 3abill

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Posted 28 January 2011 - 06:44 PM

I am a semi-retired electrician, not an electronic tech, and my computer skills are as limited as my typing skills but thank god i stumbled on this well-written,intricately-detailed,easily-understood manual. i am undertaking a restoration project on the ar3a`s i bought in 1973 while stationed in germany. I had a woofer reconed about 10 years ago and just purchased a replacement for the other one from abtech because I didn`t know if reconing is still available.I also bought 4 new `pots` that turned-out to be 8ohm L-pads.Should I return them or use with 25ohm resistor? Anyone who has the time and pity to help would be appreciated. thank you and thank you to the authors

#35 RoyC

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Posted 28 January 2011 - 08:54 PM

I am a semi-retired electrician, not an electronic tech, and my computer skills are as limited as my typing skills but thank god i stumbled on this well-written,intricately-detailed,easily-understood manual. i am undertaking a restoration project on the ar3a`s i bought in 1973 while stationed in germany. I had a woofer reconed about 10 years ago and just purchased a replacement for the other one from abtech because I didn`t know if reconing is still available.I also bought 4 new `pots` that turned-out to be 8ohm L-pads.Should I return them or use with 25ohm resistor? Anyone who has the time and pity to help would be appreciated. thank you and thank you to the authors


Welcome to CSP, 3abill!
Did you purchase the replacement woofer from ABT recently? If so, I would return all of the items, as ABT's current woofer replacement does not meet original specs. The l-pad/25 ohm resistor combo works well, but you can purchase the same l-pads for more than 50% less than ABT's price elsewhere.

When you say "reconing", do you mean replacing the deteriorated foam surrounds? Regardless, your original woofers are repairable, and your very best bet.

...sent you a Personal Message.

Roy
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#36 Carlspeak

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Posted 05 February 2011 - 07:58 PM

Page. 21 of the document states that 28 oz. "is required" for alnico magnet speakers and 20 oz. is the norm for ceramic magnet speakers. I believe this text was put into the document based on a series of stuffing measurements taken over time by one or more of the authors. Restorations I have completed with Alnico magnet woofers has shown that 28 oz. may not be required and perhaps the text of the document needs to be revised.

I recently completed restoration of an AR3 and a AR3a. Both had Alnico woofers and # 7 coils and both had rock wool stuffing. I re stuffed each with 20 oz. of OCFG obtainable from standard R-13 wall insulation and measured Fc. One speaker got 41 hz and the other 35 hz. The woofers had Fs of 16 and 19 hz. I have seen this same result once before. The 35 hz. Fc speaker had a measured Q of 0.78. The 41 hz. speaker measured 0.64. On average, this particular pair of speakers was a very respectable 0.71 with Alnico magnet woofers, #7 coils and 20 oz. of FG.
In June if last year I saw a similar result (http://www.classicsp...opic=2080&st=20). See post #31.

The good news here is the reduction in FG weight did not raise Q significantly - making the speaker sound like a boom box.

It's becoming evident to me that the difference in stuffing weight may be attributable not to the change in woofer type and series inductor coil but, instead to the inherent density difference between rock wool and the yellow fluffy FG AR used and modern, OC pink FG. Perhaps it took 28 oz. of rock wool to accomplish the same cabinet size enhancement effect that only 20 oz. of a more fluffy FG (my OCFG included) obtained.

if I can get the same box target resonant frequency (Fc of 40-42 hz) with 20 oz. of FG with an Alnico woofer as 28 (or so) oz. of rock wool, was the switch to 20 oz of fluffier FG around the same time as the switch to ceramic woofers just coincidence? I also question the connection is between inductor changes and stuffing with the AR3a # 7 to the # 9. The ceramic woofer had about the same Fs target (high teens) as the Alnico one. Same Fs & same cabinet volume but different density of stuffing for the same results all seem to point to mere coincidence with the timing of the woofer change. I'm just speculating here, but the bottom line is 20 or so oz. of modern, fluffy fiberglass will work just fine with older Alnico woofers and #7 inductor coils.
IT'S ALL ABOUT THE MUSIC!

Carl
Carl's Custom Loudspeakers

#37 RoyC

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Posted 09 February 2011 - 08:21 AM

Page. 21 of the document states that 28 oz. "is required" for alnico magnet speakers and 20 oz. is the norm for ceramic magnet speakers. I believe this text was put into the document based on a series of stuffing measurements taken over time by one or more of the authors. Restorations I have completed with Alnico magnet woofers has shown that 28 oz. may not be required and perhaps the text of the document needs to be revised.

I recently completed restoration of an AR3 and a AR3a. Both had Alnico woofers and # 7 coils and both had rock wool stuffing. I re stuffed each with 20 oz. of OCFG obtainable from standard R-13 wall insulation and measured Fc. One speaker got 41 hz and the other 35 hz. The woofers had Fs of 16 and 19 hz. I have seen this same result once before. The 35 hz. Fc speaker had a measured Q of 0.78. The 41 hz. speaker measured 0.64. On average, this particular pair of speakers was a very respectable 0.71 with Alnico magnet woofers, #7 coils and 20 oz. of FG.
In June if last year I saw a similar result (http://www.classicsp...opic=2080&st=20). See post #31.

The good news here is the reduction in FG weight did not raise Q significantly - making the speaker sound like a boom box.

It's becoming evident to me that the difference in stuffing weight may be attributable not to the change in woofer type and series inductor coil but, instead to the inherent density difference between rock wool and the yellow fluffy FG AR used and modern, OC pink FG. Perhaps it took 28 oz. of rock wool to accomplish the same cabinet size enhancement effect that only 20 oz. of a more fluffy FG (my OCFG included) obtained.

if I can get the same box target resonant frequency (Fc of 40-42 hz) with 20 oz. of FG with an Alnico woofer as 28 (or so) oz. of rock wool, was the switch to 20 oz of fluffier FG around the same time as the switch to ceramic woofers just coincidence? I also question the connection is between inductor changes and stuffing with the AR3a # 7 to the # 9. The ceramic woofer had about the same Fs target (high teens) as the Alnico one. Same Fs & same cabinet volume but different density of stuffing for the same results all seem to point to mere coincidence with the timing of the woofer change. I'm just speculating here, but the bottom line is 20 or so oz. of modern, fluffy fiberglass will work just fine with older Alnico woofers and #7 inductor coils.


Carl,

I've conversed with Tom and John, and have been been looking over the data we used for the AR-3a restoration document cabinet stuffing recommendations. The average amount of original stuffing found in all AR-3a cabinets with cloth surround woofers was around 30 oz, ranging from 28oz to 32oz. The statement regarding using this amount of stuffing for the cloth surround woofer was based on what was found to be in the original cabinets for the purposes of authenticity, *and possible unmeasured differences in upper bass and midrange response between the two types types of woofers*. In other words it was safer to state the original specification for cabinets equipped with cloth surround woofers. It was *not* based on our measurements. If it had been, and fc and Q were our only considerations, we would have recommended 20oz across the board, as our measurements agree with yours. In fact, I found fc remained within specification at amounts less than 20oz as well as over 32oz with most of the 3a woofers I measured.

Some other things need to be taken into consideration when discussing the AR-3a woofer and cabinet stuffing.
-Cloth surround woofers and very early foam surround 3a woofers were at the lower end of the 18 hz+/- 15% fs specification, and the later, foam surround versions were at the higher end.
-There are response differences between the two types of woofers, which is the most likely reason for the change from #7 (1.88mh) to #9 (2.85mh) woofer inductor.
-Q was raised closer to 1 in all AR speakers around 1970, when the foam surround woofer was introduced. The cloth surround 3a woofer has lower Q, in and out of cabinet, regardless of stuffing amounts.
-We did not find significant differences between the behavior of fiberglass vs rock wool. Cabinets with 32oz of either material were stuffed VERY tightly, and had similar test results.
-AR speakers were designed around fiberglass stuffing. Rock wool was used for a two year period when fiberglass was in short supply, and was inserted at the same weight as fiberglass.
-According to John, fiberglass fibers are 3-5 um in diameter then, and today. There is no difference between the number of fibers when stuffed with the same density then or now.

It is probable that just one amount of stuffing, whether it be 20oz or 28oz or 32oz, is not "optimal" for ALL 3a woofers, but we all seem to agree that a range from 20oz to 32oz will preserve the fc specification. This certainly provides wiggle room for the restorer with regard to the fc parameter. (I personally find 3 small 8 oz utility bags/24oz of unfaced fiberglass per cabinet to work to my satisfaction for most 10 and 12 inch AR woofers of the 70's, and subjectively find 20oz to be a bit too little.) OTOH, the document simply states what was there in the first place, as it relates to an authentic restoration.

Roy
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#38 Carlspeak

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Posted 09 February 2011 - 01:32 PM

Carl,

I've conversed with Tom and John, and have been been looking over the data we used for the AR-3a restoration document cabinet stuffing recommendations. The average amount of original stuffing found in all AR-3a cabinets with cloth surround woofers was around 30 oz, ranging from 28oz to 32oz. The statement regarding using this amount of stuffing for the cloth surround woofer was based on what was found to be in the original cabinets for the purposes of authenticity, *and possible unmeasured differences in upper bass and midrange response between the two types types of woofers*. In other words it was safer to state the original specification for cabinets equipped with cloth surround woofers. It was *not* based on our measurements. If it had been, and fc and Q were our only considerations, we would have recommended 20oz across the board, as our measurements agree with yours. In fact, I found fc remained within specification at amounts less than 20oz as well as over 32oz with most of the 3a woofers I measured.

Roy


I may be nitpicking here, but based on what you've written above, the first paragraph in sect. 4.3 still could use a minor revision or two in order to avoid confusion on the part of someone (like myself) using the document as a guide for their restoration. No were else in that section does it state clearly how much FG to use other than the first paragraph.

For example, if I read that my early Alnico-woofer speaker 'requires' 28-30 oz. of yellow FG, that's what I will use and, based on my earlier post and your concurrence, that is not the case.

If, instead, I read my early-Alnico woofer *required* or *used* 28-30 oz. of FG, then it would be clearer to me that's what the specification WAS ( i.e., in the past).

Thus, my suggestion is to change the word 'requires' to 'required' or, 'used' in the two sentences that describe stuffing amounts in Alnico and ceramic woofer speakers. Additionally, a sentence could be added stating clearly how much fiberglass should be used when re-stuffing. I'll leave that up to the document's authors to decide how much or give a range as you described was feasible based on your experience. I'm not saying 28-30 oz. of modern, fluffy FG won't work although it would be a tight fit. I just feel it's overkill and may provide excessive damping.

Roy, your other comment regarding the raising of Q in foam surround woofer speakers was interesting. I wonder why. Could it be perhaps the overall bass response with the ceramic woofers was not quite a good as the Alnico woofers and raising Q was a way to make up for that?
IT'S ALL ABOUT THE MUSIC!

Carl
Carl's Custom Loudspeakers

#39 RoyC

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Posted 09 February 2011 - 05:37 PM

Thus, my suggestion is to change the word 'requires' to 'required' or, 'used' in the two sentences that describe stuffing amounts in Alnico and ceramic woofer speakers. Additionally, a sentence could be added stating clearly how much fiberglass should be used when re-stuffing. I'll leave that up to the document's authors to decide how much or give a range as you described was feasible based on your experience. I'm not saying 28-30 oz. of modern, fluffy FG won't work although it would be a tight fit. I just feel it's overkill and may provide excessive damping.

Roy, your other comment regarding the raising of Q in foam surround woofer speakers was interesting. I wonder why. Could it be perhaps the overall bass response with the ceramic woofers was not quite a good as the Alnico woofers and raising Q was a way to make up for that?


Carl,

There is concern that 20oz may not be more "correct" than 28oz. It is not within the scope of the restoration guide to make that determination, or to decide how AR should have designed the speaker. All stuffing amounts between 20oz and 32oz seem to "work", but 28oz to 32oz is the original specification for the cloth surround woofer. There has never been any indication that 28oz provides excessive damping, and no restoration will be compromised by using this amount. While I agree 32oz seems like alot to jam into the cabinet, it always meets the fc specification.

As I mentioned above, there are aspects of the upper bass and lower midrange response which are influenced by increased or decreased amounts of stuffing. The big AR-3a woofer reaches much farther into the midrange than modern designs will typically allow for a 12 inch woofer. Varying amounts of stuffing in the 3a affects the sonic character of the speaker, regardless of fc measurements. Q measurements tell some of the story, but not all of it. I have personal preferences, but they are not necessarily "correct" from an authentic restoration point of view.

...which leads to your question. Your guess is as good as mine. We have speculated that Q was raised in the 70's to enable AR to better compete with more bass "boom" in audio show rooms, which had become crowded with competitors demonstrating popular music. Maybe it was a change in design philosophy along the lines of our discussion above. Both types of 3a woofers seem to have the same low bass response with some differences apparent at higher frequencies.

Most folks who replace the original stuffing do not have the means to weigh new fiberglass. As I mentioned above, my preference generally agrees with yours in that 3 utility bags (see photo below) of fiberglass per cabinet, or around 24oz, will likely provide satisfactory results across the board for all iterations of the AR-3,3a,2,2a,2x,2ax and 5.

Carl, Your point about using the term "required" is well taken, and I'm confident any revisions to the restoration document will include some discussion and clarification along the lines of our conversation. (As always, your input is very appreciated.) Comments could also be added regarding "yellow" fiberglass, which has become difficult to find, and appears to have been replaced by a white type (see photo). The yellow fiberglass was recommended in the document because it was denser and seemed more like the original AR fiberglass, even though we knew the pink stuff would work adequately. BTW, it is somewhat easier to cram 28oz to 32oz of the new, softer, white fg into a cabinet than it is to do so with the pink.:)

Roy

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#40 davidro

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Posted 14 November 2011 - 04:13 AM

Oh I forgot to acknowledge my gratitude to the authors of the Guide. I've been able to fix my 3a and love them so much. The first speakers that I'm really happy with. Special thanks to Roy who's confirmed the physically un-matching drivers would sonically be matching, which proved to be true to my ears!




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