wool stuffing for the speakers

[roundhome]

hello i was wondering, I have read here that wool is the best stuffing for the speakers.

I have a sorce for fresh new wool and if it would be a good upgrade to switch to wool?

Jim

PS thanks for the hard work getting the forum back up I'm a main frame tech and know how hard fixing these things can get.

I was going through withdrall not have the information that comes on here.

Thanks again

[stan461]

I re-stuffed my AR3as with Acousta-Stuf. I weighed what stuffing was in the box and added a similar weight of Acousta-Stuf.

The bass now sounds perfect to me. BTW, there were varyiations in the weight of the original struffing from box to box. I have 2 pair and the boxes varied +- 2 grams. So much for exactness. I think the average was 1 lb. 13 oz.

The old stuffing was truly nasty and it looked to be breaking down. Did I "have" to change it? Probably not. But I was in there replacing pots that kept cutting out (even after I cleaned them) and also I replaced those wonderful 30 year old caps. I especially got a kick out of the wax jobs.

Acousta-stuf will probably not break down for a century. Its a little expensive but so is this hobby.

[soundminded]

We've discussed this in the past in a somewhat different context. Who told you wool was the best, Audio Note's Peter Qvortrop? I think he uses wool shorn from sheep in New Zealand or something. I know he is a believer in minimal damping and although he has at least one model which uses a sealed enclosure (model K) I don't think his philosophy would apply directly to AR speaker systems.

The stuffing whether it is wool, fiberglass, Acousta Stuff or whatever plays a critical role in the velocity damping of the woofer which controls its mechanical Q. The speaker is forced to work to overcome the frictional drag of pulling and pushing air between the fibers. But the volume of the material not counting the air space between the fibers controls the amount of air remaining in the box and therefore the critical spring constant that the restoring force will provide. So it contributes to two of the three variables which mechanically tune the speaker. Whether the physical properties are consistant from one batch of wool to another, it is not likely to be comparable to the fiberglass which was originally installed by AR.

I would venture a guess that the optimal amount of fiberglass and the optimal size of the enclosure was determined by extensive trial and error. While Dynaco's enclosure used a somewhat different principle, their website discloses that the amount of fiberglass was adjusted for each production unit by actually measuring the woofer response and adding more until the desired response was obtained, a very labor intensive process. I think the speakers were actually manufactured in Denmark.

[johnieo]

>But the volume of the material not

>counting the air space between the fibers controls the amount

>of air remaining in the box and therefore the critical spring

>constant that the restoring force will provide. So it

>contributes to two of the three variables which mechanically

>tune the speaker.

>I would venture a guess that the optimal amount of fiberglass

>and the optimal size of the enclosure was determined by

>extensive trial and error.

Based on what I see presented in Dicakson's 6th Ed, Table 1.21, I would agree with soundminded that Fiberglass is best and that its weight was very carefully determined.

Dicakson describes an experiment with an 8" driver sealed in a 1 cf box. He measured several parameters for various stuffings including Fiberglass (1-, 2-, 4-lb/cf), Dacron, foam and Acousta-Stuf. He observed--for the case of 100% cabinet filling--that the lowest f sub s was achieved with 1-lb/cf Fiberglass. The only other case in which a slightly lower f sub s was reported was for a cabinet filled 50% with 2-lb/cf Fiberglass! This highlights soundminded's comment about the importance of the volume of air remaining after packing--they are about equal in these two examples. Other combinations evaluated by Dickason did not show f sub s values as low as these two. He did not evaluate wool and only evaluated one box/driver combination. Even so, the results are interesting to compare. The AR-3/3a cabinet has an internal volume of 1.5 cf (23.5" x 12.5" x 8.75" minus components). Most folks who have measured the weight of Fiberglass in their AR-3a speakers report weights of ~1 lb, 12 oz +/- an ounce. AR's very carefully determined Fiberglass weight is quite close to what Dickason measures for a different box/driver combination! Based on his data, I fail to see what would be gained by replacing Fiberglass.

I became interested in this last year, when replacing the Fiberglass in my 3a units--there was a lot of glass dust in one cabinet. I couldn't find which glass density (0.5-, 0.75- or 1.5-lb.cf) to use. Some sources said use R-19, but R-value describes heat flow through a blanket not glass density. So gave up, bought what was in Home Depot, and filled by weight. If I had to do it now, I don't know what to do differently.

[soundminded]

If you are experimenting with building a loudspeaker from scratch, you have many options. I'm considering using heating system filters possibly in multiples which may present sufficient drag with less volume taken up. This might allow either a smaller box or a lower F3 for a given driver. An assembly of multiple fine tubes might also work.

I would bet knowing AR's meticulous reputation for quality that they periodically tested their fiberglass for consistancy with the original specification in the prototype and the performance of assembled units to verify that they were true to the original design. If the fiberglass has shown deterioration over the decades to the point where performance has been changed or where separated broken fibers themslves present a risk to reliability of other components in the system or to people opening the boxes, that is truely a shame. Fiberglass is potentially a dangerous material. I don't want to sound alarmist but there has been discussion at times of placing it in the same hazardous class as asbestos. Anyone using exposed fiberglass should at least wear protective clothing and most importantly, a disposable filter mask. They are available at very low cost at Home Depot among other places. A pair of thin disposible latex gloves and a disposible paper suit is also a good idea IMO.

[johnieo]

>If the fiberglass has shown

>deterioration over the decades

No, the fiberglass is stable in this environment. It had not degraded chemically. The issue is multiple handling. One of my AR-3a began its life as a 3 well over 40 years ago. I found glass dust and as well chunks of small size. This I attribute solely to removal and restuffing when it was converted, and later when pots were cleaned. More recently, the caps were upgraded and the woofer inductor replaced. Obviously, handling causes chunks and fibers to break; care, not alarm, is in order.

[RoyC]

I've been collecting '3a data and have some to share regarding stuffing. I weighed the fiberglass (in plastic trash bags) from 6 AR-3a cabinets with a digital fishing scale. The serial #'s ranged from 09xxx (1968 alnico woofer) to 96xxx (1974).

These are the results rounded to the nearest ounce along with the actual measurement in lbs:

09xxx(1968) 1lb 15oz(1.95lbs)

43xxx(1971) 1lb 13oz(1.80lbs)

67xxx(1972) 1lb 4oz (1.22lbs)

67xxx(1972) 1lb 4oz (1.24lbs)

96xxx(1974) 1lb 2oz (1.12lbs)

96xxx(1974) 1lb 5oz (1.32lbs)

All cabinets had the typical AR yellow shredded fiberglass with the exception of the oldest which had darker yellow/brownish cut batts.

All markers such as glued on grills (the 74's had velcro), pots, wiring, etc indicated that they were previously not tampered with. The weight includes thin plastic bags and the "behind-the-woofer" tissue paper.

Roy C.

[soundminded]

Whatever the risk of fiberglass, it is not chemical, it is physical. Asbestos is virtually chemically inert. The danger is that it becomes friable, extermely crumbly. If small particles of fiber, so small they cannot be seen by the naked eye become airborne and find their way into the lungs, they are a physical irritant which cannot be removed by the body. Normal body defenses are the minute hairs and mucous which line the nasal and bronchial passages. These tend to trap and eliminate the fibers. Injury resulting in actual disease if it will happen at all usually takes two to three decades. For several years, I was involved in the largest asbestos abatement project in the state of New Jersey. I don't know if fiberglass presents a similar risk but it is prudent to take precautions. An additional precaution besides a mask and disposible paper suit and gloves is to wash your clothing and shower after working with it. It is not a cause for alarm but people exposed to it should be aware that there are precautions which should be exercised. (even mild exposure makes me itch like crazy.)

[Guest radkrisdoc]

Does anyone know the weight of stuffing in an AR-9/90? And what are your recommendations for the rolls of stuffing in the upper part of the enclosure in the 9/90? Are these rolls made of fiberglass/felt or foam? What about the lower midrange compartment?

Interesting thread, this one. I am trying to put together information like this for at least a series of speakers like the 9, 90, 91, 92 in a word document, as a source of information for everyone who are interested. I've started with a list of models that have similar drivers, including the numbers on each driver and will keep adding info as I come across them.

Thank you all in advance, Kris

[r_laski]

Kris,

>Does anyone know the weight of stuffing in an AR-9/90? What about the lower midrange compartment?<<

In the AR information section of this web site are some of the system assembly "blueprints" for the AR 9. Here is the stuffing info from the AR 9 Assembly notes:

6. The 40 ounces of polyester wadding (item 10) consists of 4 pads, each about 2 ft square, and weighing 10 ounces. Each pad MUST BE weighed. Each pad is rolled up and placed in the cabinet as shown. With all 4 rolls in placed there shall be no voids at the top of the cabinet. The 4 rolls shall be straight and even and not bunched up. The wires leading to the drivers shall be located in the wadding in such a manner as to prevent them from buzzing.

11. The 8” lower midrange cavity is filled with 2 ½ ounces of shredded polyester wadding (item 11). This must be weighed. The wadding shall be pushed towards the outside of the cavity to create a hole in the middle for the driver magnet. (I had to look at the materials list on the other drawing to confirm 2.5 oz. The fraction is unreadable on the “Notes” page).

There isn't a similar document for the AR 90. However, the lower midrange cavity is exactly the same as the AR 9, so the 2.5 oz polyester wadding should be the same.

You could extrapolate the weight of the stuffing for the AR 90 cabinet by comparing the internal volume of the AR 9 (120 liters / 4.24 cu. ft.) to that of the AR 90 (90 liter / 3.18 cu. ft.).

>>And what are your recommendations for the rolls of stuffing in the

upper part of the enclosure in the 9/90? Are these rolls made of fiberglass/felt or foam?<<

AR used "polyester wadding". This can be obtained from fabric stores. Most speaker parts retailers also sell some kind of dacron/polyester stuffing material (Parts Express sells Acousta-Stuf).

You might be interested to know that AR switched from fiberglass to polyester wadding sometime during the production of the AR 11 -- ADD / Truth in Listening series.

>>Thank you all in advance, Kris<<

Hope this helps.

Rich

[Carlspeak]

>hello i was wondering, I have read here that wool is the best

>stuffing for the speakers.

>I have a sorce for fresh new wool and if it would be a good

>upgrade to switch to wool?

>Jim

>PS thanks for the hard work getting the forum back up I'm a

>main frame tech and know how hard fixing these things can get.

>

>I was going through withdrall not have the information that

>comes on here.

>Thanks again

>

I suggest you contact Ed Dell at Audio Amateur publications and ask about articles that were published in Speakerbuilder magazine regarding different types of speaker stuffing. Some good articles are in their archives that contain some decent research.

Carl

[Pete B]

The first I saw of long hair wool being used in speakers was Bailey's transmission line articles in Wireless World and/or Speaker Builder, back in the 1960s IIRC:

http://www.t-linespeakers.org/design/biblio.html#Bradbury

I've mentioned this paper from the AES online in the past:

L.J.S Bradbury, 'The Use of Fibrous Materials in Loudspeaker Enclosures' JAES Vol24, April 1976.

The paper is discussed here somewhat:

http://www.t-linespeakers.org/projects/tlB...endix/bradbury/

Some online "experts" claim that there are errors in the original Bradbury paper, but it's a difficult subject and I've not done any controlled experiments with long hair wool, but I have used it. I usually use fiberglass, the pink stuff, it works well. AcoustiStuff also works well.

There've been some enthusiastic claims for long hair wool over the years and I believe this has caused much excitement over it, however it's always important to check such claims as they're usually blown out of proportion if not erroneous.

>hello i was wondering, I have read here that wool is the best

>stuffing for the speakers.

>I have a sorce for fresh new wool and if it would be a good

>upgrade to switch to wool?

>Jim

>PS thanks for the hard work getting the forum back up I'm a

>main frame tech and know how hard fixing these things can get.

>

>I was going through withdrall not have the information that

>comes on here.

>Thanks again

>

[roundhome]

Idea don't shoot those that think please.

If you take 100 AR 3A speakers unless you were lucky none of them would have the same base responce.

Now before you thow me out listen. they are flilled with randome size chunks of fiberglass thus having randome drag co. and random air space between the chunks. meening no consitancy.

only if a you had a good control over spacement of the fibors and the volume of air would you be able to get consitancy Like said above using stacks of filters compresed evenly in the void and having the same amount of open air volume would you have the type of control needed for the same base responce in each speaker. being able to adjust for the specs by adding or taking out the stacks

the open air before the filters would compress faster then the air going through the filters

Now being able to compress the filters to get the propore drag co of the air would be needed to.

but you would have to still take into considrasion the open air volume as the filters were comperessed there could be no void behind the filters this would alow the air to bonce adding unwanted harmonics.

once the disired compresed filters and open air combination was reached for the spec using the driver selected for the volume of the cabinet.

you could consitantly recreate the same sound in each cabinet used. as long as the drivers had the same specs.

this could not be done with randome chunks of randome sized fibor glass.

?????

sorry I think to much

working on air flow through a manifold of a race car and all that the air has to put up with in there has me thinking this way about speakers

roundhouse

let me have it guys

Ps

Taking into considration the rooms efect on the base would require that both be adjustable the drag co and the open air volume

this would require acoustic feedback with the ability to adjust both specs to match the room

One mic fed to a set of spec stored in the the system compaired to the sound picked up by the mic.

logrithems to do the tuning of the mechenical parts for filter drag and open air volume.

A computor program.

I know i'm out to lunch

whare is Mr Kantor when you need him?

I could use his input about now.

[Carlspeak]

Well, I guess you've gotten your fill of ideas and free advice. But you know, loudspeaker stuffing isn't that expensive after all. So why not try that wool you're thinking of using. Try some acousta stuff also. Try some R30 home insulation fiberglass and decide for yourself which works best for your listening tastes.

Personally, I don't think it will make a whole hell of a lot of difference to bass response for an acoustic suspension speaker which type of stuffing you use. However, beware, the hyper-anal 'don't change anything because the original designer's voiced the speaker with the parts they put in there' buffs may cringe at the thought of Acousta Stuff.

Now, if you've got a transmission line speaker, then the stuffing ype would probably be more of an influence on what you hear because the stuffing acts to dampen the cone's backwave, but sound escapes from the port opening anyhow and you hear that.

Have fun!

CarlSpeak

[soundminded]

"However, beware, the hyper-anal 'don't change anything because the original designer's voiced the speaker with the parts they put in there' buffs may cringe at the thought of Acousta Stuff."

I don't think that's the point. The original design as it was offered to customers was the result of extensive scientific and engineering work which optimized the box, the driver, and the damping material. Acoustic Research had the resources to experiment and adjust all of the variables to tune the driver/enclosure combination to give the best combination of flat frequency response down to the lowest frequency with the least distortion. When you experiment on your own, you will likely find it difficult to obtain comparable results. The good news is that the data needed to get back to where the original engineers were nearly fifty years ago is still available.

[RoyC]

I have generally agreed that messing with the original design is unlikely to succeed unless you are very lucky or very smart (I'm neither :-)), but I'm puzzled now that I've measured '3a's with fill varying up to a half pound. I'm wondering how "exact" the manufacturing process was...or required to be.

Roy C.

[roundhome]

>

>Well, I guess you've gotten your fill of ideas and free

>advice. But you know, loudspeaker stuffing isn't that

>expensive after all. So why not try that wool you're thinking

>of using. Try some acousta stuff also. Try some R30 home

>insulation fiberglass and decide for yourself which works best

>for your listening tastes.

>Personally, I don't think it will make a whole hell of a lot

>of difference to bass response for an acoustic suspension

>speaker which type of stuffing you use. However, beware, the

>hyper-anal 'don't change anything because the original

>designer's voiced the speaker with the parts they put in

>there' buffs may cringe at the thought of Acousta Stuff.

>

>Now, if you've got a transmission line speaker, then the

>stuffing ype would probably be more of an influence on what

>you hear because the stuffing acts to dampen the cone's

>backwave, but sound escapes from the port opening anyhow and

>you hear that.

>Have fun!

>CarlSpeak

First please don't put words in my mouth.

I have not gotten fed up with anything! fact this is vary informative for all. As for the three types of stuffing none in the form they are will acheave consistancy just by stuffing it into a box. it will require more then that to gain consitancy.

My last statement showed no disrespect for any of AR hard work perfecting the sound of there speakers . It more address the fact of consitancy in manurfactoring them after all the hard work was done. we have noted difference in woofer outputs and croosovers and in the amount of stuffing!

all will effect the sound. You can't test every speaker coming out.

so why not come up with a consistant way to acheve the same sound out of each . That was the point I was getting at.

these are not transmission line speaker we are talking about.

And there are Many now wanting to use AR speakers for seround sounds systems and would like some consistacy in sound what is wrong with that.

I wish no Flame outs on the this forum others have that problem

If we all work toghther to find

A good replacement for are aging tweeters

consistant foam replacements

good caps

thr right type of oil for tha cabinets

the correct foam for are AR 9s

Then It takes Ideas and testing and working together like the woofer project that is going on now.

I even sent a set of foam rings off my own Ar 9s to see if someone could make more good ones for us all.

and that was the first tiem they were out of the box since 1983 when they were only out for three months. I bought them new in 1980.

And seeing how this is my retirment project after getting put back together by the Navy doctores and I can't do much else It is vary fun for me plus to be able to talk to the likes Of Mr Tyson and Mr Kantor. Is a plesure in its own.

every thing changes sometimes for the better but sometimes the wost but it has to change so let find the stuff that is avalible now to try and fix are changing speaker since we cannot fix are changing ears. will we ever know if we got it right.

For someone elses EARS.

I Thank all that input on this forum.

roundhouse

I live In a dome house that the I disigned and built and the counties enginers said it would cost 1200 a year to Heat funny It has never cost me more then 200 a year for the past ten years!

so much for there computer programs

[soundminded]

It is possible that a change such as the one you describe in the amount of fiberglass will not change the f3 or Q substantailly but that would not be my first guess. Or it may not be obviously audible. That's also just a guess. Still there is an optimal amount and type which is the goal for matching the prototype. AR3 and AR3a were engineered long before ISO 9000 was invented (I think) but the principles of quality control and building production units to conform to an engineered prototype in every detail to assure the customer that his unit will perform as closely as possible to his expectations and that any two units will perform identically as well were well known. When you change the fiberglass, you are effectively retuning a critically tuned mechanical system. Just so you are aware.

[RoyC]

I am aware..just wondering about AR's quality control.

Roy C

[soundminded]

AR's quality control was outstanding, exceptionally so especially for a consumer products company. How do I know? My father was the quality control manager of Hazeltine Electronics Corporation, a small manufacturer of military electronics on Long Island. Their quality was among the finest in the world. Somebody specified an AR driver for an intercom in an electronics console and he personally audited the manufacturing facility. He was shown barrels and barrels of drivers which were deliberately destroyed because they were out of spec. They were not sold to another party at reduced cost, they were not given to employees for their home brew projects, they were destroyed so that they would never see the light of day in any AR product or anyone elses. Remarkable given those times and what other manufacturers were doing. They were uncompromising. I think it was Tom or Ken who posted photos of those barrels on a thread some time ago.

[RoyC]

Ok, so if we agree that its not a quality control issue, then we shouldn't sweat the differences of 8 or more ounces of original fiberglass fill in our finely tuned vintage AR machines.

We know they were tweaking the woofer along the way, maybe the fill quantity varied with production runs.

Roy C.

[soundminded]

I can't say. All manufacturing specifications must have tolerances. That means the maximum permitted deviation from the specified norm or goal which is acceptable. Usually this is based on the compromise in performance or reliability that such a deviation would create and is kept within safe limits. It is hard to believe that a deviation as high as eight ounces in a spec which calls for a pound and a half would be acceptable. What could the explanation be? Was there a production run of such awful quality control that this could have gotten through? Not likely. More plausible is the possibility that someone opened the enclosure after the unit was sold and didn't restore it to its original condition. Impossible for me to say, you'd probably know more about the history of these speakers than anyone. Once a manufactured item leaves the factory and is delivered to the customer, the manufacturer loses control over it. All except for Siemens but that's another story.

[RoyC]

>More plausible is the

>possibility that someone opened the enclosure after the unit

>was sold and didn't restore it to its original condition.

Plausible maybe, but not likely. I've been restoring speakers for 20 years (mostly AR-3a's in the past 12) and I chose those cabinets because there were absolutely no signs of previous tampering. Also, all fiberglass was identical and unique to AR of the time.

I'm going with midstream design changes in the same vein as crossover changes (#7 to #9 inductors), and woofer alterations (magnet, surrounds and spiders)....either that or production run issues.

Roy C.

[Guest radkrisdoc]

Thank you Rich! That definitely helps. Kris