±1980 8" woofers

[ra.ra]

I am seeking some opinions and advice from more knowledgeable minds regarding the differences between several similar 8" woofers from AR speaker models from the late 70's and early 80's. In particular, the part numbers are: 200035, 200036 and 20037. As I understand it, 200035 was the woofer in the AR-93 speaker; 20036 was the lower midrange for the same speaker; and 20037 was the woofer in the AR-18 and several others.

These three drivers appear nearly identical, yet they obviously were intended for very particular speaker models. My review of the parts lists indicates that the only three components that differed among these drivers were: dust cap. tinsel adhesive and spider/coil.

200035 AR-93 woof 1980-82
200036 AR-93 low-mid 1980-82
200037 AR-18/18s/28 woof 1977-82

Attachments here are posted in order: 035 drawing/view; 036 drawing/view; 037 drawing/view. What is meant by this note about "treatment" which overlaps the cone-surround interface, which is sometimes located on topside, and other times on bottom?

I am generally curious about the factors that might have necessitated these somewhat subtle differences in the design of these drivers originally, but also, I have a current specific application in mind. I am trying to resurrect a pair of AR-6 speakers, and while I have been unable to source original replacement woofers, some of these other woofer models are either in my stock or available to me, and I would like some advice on which might be most appropriate fit for the AR-6 (at least on a temporary basis).

[michiganpat]

FWIW, the actual AR17, AR18, and I think AR25 woofer is the 200001, which IIRC is the same PN of the AR6 and AR7. the ones in my 2 pair of AR18's are this part number, with a flat, heavy cardboard dustcap like the 200036 under a porous cloth dome dust cap. They are also the lower woofer in the AR94, and I thought the midwoofer in the 94 was the 200036.

I'd probably use the '37 or '36 as a replacement....my SWAG with the '35 with the white dust cap is probably heavier to add mass to reduce Fs (which would also reduce sentivity) since those are more or less the "subwoofers" in the 93's setup (not a true 2.5 way as the '36 is high passed with a big NPE)

[ra.ra]

Thanks, pat from great lake state - - - when I look at the AR library drawing for 200001 (for entire woofer assembly, with two dust caps), I see it referenced as being used on AR-94, AR-25, AR-18, AR-17, and AR-15. When I look at a different drawing for only the sub-assembly of basket and magnet, it notes models AR-6, AR-7, AR-4xa and AR-MST. I know I've never seen an original AR-6 or AR-7 woof with anything but a flat dust cap, so this would all seem to make sense that many 8" woofers shared the same basket and magnet, and that the differences beyond that involved the spider/coil, tinsel and dust cap(s).

Your response seems to suggest that the 036 and 037 parts might offer a bit more blended sensitivity in an AR-6 speaker, rather than the 035 intended for the lower frequencies. Thanks, I'll keep this in mind and it sounds like good advice. And, much like yourself, I remain a huge fan of the many variations of these 1-1/4" tweeters, ferro-fluid or otherwise.

[michiganpat]

well, another thing is there were revisions along the way, 1200001-1, 1200001-2, 1200001-3 and I'm guessing the domed cloth dust cap was probably added for asthetics more than anything else....I don't remember for sure what the actual part number is in my 18's, if it's -1 or -2. I'll try to remember to bring some allen wrenches to work tomorrow to pull a woofer....

and yep, I love that allison designed tweeter....in fact, while I really like the bass of the 2ax's I recently restored, I'm fairly underwhelmed by the mids and highs of them compared to my 18's.....I have a feeling I might like the AR8's, or am kicking myself for not picking up the AR93's that were on my local craigslist a few years ago---would have been basically my 18's with the extra extension afforded by 4 more 8" woofers in a larger cabinet....

[ra.ra]

Interesting - - - I had never been aware of the double dust cap but you are totally correct - - - on the attached parts list the outer dome cap is noted as "cosmetic dust cap", plus you can clearly see them both in the section drawing.

Clearly, this basket/magnet assembly had many different iterations resulting in the various woofer part numbers. It appears that the original date of this drawing was from year 1975 or 76, and what I have not shown here is the list of revisions which runs from K thru Z (this drawing apparently supersedes a similar drawing which went thru revision J), and the date of the final revision is in 1980.

Any idea what is meant by this "treatment" note at the cone-surround interface? And, did all of the 8" woofers from this era utilize the same foam surround, or were there different compliance factors (foam density, roll radius) required for these various woofers?

Your note about the AR-8 speaker is also curious - - there seems to be so little interest and information on this particular model from the dying days of the "classic" era, but with your fondness for the 10" foam woof and this 1-1/4" tweet - - - who knows? It just might be a great speaker for your listening tastes.

[michiganpat]

it's been 3+ years since I refoamed my 18's, so I don't remember the total details of the treatment on the cone/surround edge, but the tonegen woofers on my Rock Partners had a very similar treatment. it was like some sort of rubbery substance was applied on the edge of the surround and the surround was compressed under it. not sure how you could duplicate the proccess/look/geometry with a refoam.....

[ra.ra]

As soon as you mentioned the Tonegen woofers in your Rock Partners, I realized that I think that is the very same woofer that became the universal replacement (p/n 1200001-1) that I have in a pair of AR-7 speakers, which Roy C clarified for me several months ago. After closer inspection, I've attached a pic of my AR-7 woofer, where you can see the applied "treatment". Its coverage is not quite as extensive as the several drawing details suggest, and it sits solely on the surround right where the slope meets the roll. It looks almost like a very thin bead of transparent silicone sealant, but my curiosity had to do with its purpose, not an attempt to replicate it. What function does it perform?

In an attempt to answer my own question about the surrounds used in these various 8" woofers, I looked more closely at the parts lists and confirmed that the cone and skiver (what a great word!) assembly is indeed identical for all of these woofers.

[michiganpat]

BTW, if you look at the drawings library, there are specification drawings on all 3 of these drivers listing Fs, sensitvity, and showing a FR diagram....

35 and 37 are near identical frequency response, but 35's rated senstivity is 84db, 37's is 88. 35's Fs is 28hz, 37's is 30. so.....looks like the big white dustcap on 35 adds some mass, lowering Fs and senstivity. DC resistance of 35 is listed at 8ohm, 37 at 4.6 ohm

36's frequency response looks much different, but it was also tested in a different test box...DCR is listed at 7.9-9.7 ohm, and sensitivity 86.5 db....no fs given

[ra.ra]

Not sure if anyone else has ever experienced this, but I sometimes have difficulty getting AR drawings from the CSP library to open properly. As much as I might like to tout the superiority of my Mac computer over PC's, I am usually able to access these drawings much mo' better from a PC. Thanks, MI Pat, but I'm still a-lookin', and a-readin', and a-learnin' about the comparative specs of these 8" woofers.

Recently, I obtained yet another different pair of 8" AR woofs. At the MIT flea market last month, I purchased a pair of AR-28B's for the princely sum of one Abraham Lincoln. While I've never really liked this series all that much (vinyl cabinets, bullnose front, brown grilles, lesser build quality), I've noticed very good drivers used in these speakers, even as AR was trying to lower costs.

The tweets in this speaker are the excellent p/n 200034 (exact same as 200038, but with added screen protection?). The woofers, unlike other parts already mentioned in this post, are part number 200050, which I had never encountered. Very much like other 8" woofers, but I have detected two obvious physical differences - - dust cap and basket - - but I'm not sure how this relates to performance or sonic characteristics.

See pics attached. First pic: 050 (L) and 037 ®. Second pic: 050 (distant) and 037 (near). Third pic: 037 w/solid duct cap (with pollen dust), Fourth pic: 050 w/more transparent dust cap (sim. to AR-4x). Anyway, am just curious if anyone might help explain to me the differences between this woofer and others already discussed in this post. Does this deeper basket represent a longer dimensional travel of the voice coil? Does this more porous dust cap suggest that this speaker is not fully airtight? Any and all thoughts are appreciated.

[RoyC]

ra.ra,

Did you measure the resistance of each woofer?

Roy

[ra.ra]

Thanks, Roy, for mentioning this. Normally, when I bring home new speakers, I first take notes on a little 3x5 card - - - i.e., speaker model; date, location and price purchased; woof and tweet part nos. and dates of production; DCR measurements; and cap values.

Even though this post remains curious about several versions of AR 8" woofers, the measurements for these two pair of speakers, which both have a single 5 mf cap in the x-o, are as follows:

AR-18b

tweeter p/n 200034-0: DCR 5.2 and 5.3 ohms

woofer p/n 200037-0: DCR 4.6 and 4.7 ohms (later reading 4.9 and 5.0 ohms)

AR-28b

tweeter p/n 200034-0: DCR 5.4 and 5.5 ohms

woofer p/n 200050-0: DCR 5.0 and 5.4 ohms

My earlier mention of scouring AR dwgs. was meant to suggest that I have not yet looked into this 050 woofer in detail, to see how and where its parts list might differ from other woofers. Nonetheless, I am curious about two components in particular - - - the surround and the dust cap. First the surround - - - in restoring these various versions of 8" AR woofers, is it reasonable to think that they would all benefit by having surrounds replaced with the same highly compliant foam surround, or would it be better to use different foams for different woofers ..... and if so, how to determine? On the dustcaps, I was surprised to see that the 050 woofer dustcap was reasonably transparent, much like that of the 4x woofer, which leads me to believe that perhaps this 28b speaker was designed to operate somewhat differently from its brethren.

Almost forget - - - and the basket. Clearly these have very different shapes.

Any and all comments/advice appreciated.

[ligs]

Has anyone measured the inductance of these different 8" woofers. As a first approximation, the upper end frequency response of a speaker is related to its inductance, the lower the inductance the more the highend extension.

[RobHolt]

I've noticed that woofers from the later 8" models - 8S, 18S, 18LS and probably others have slightly lower impedance coils with the DCR at 5 Ohms.

This would at least go some way to explaining the apparent higher sensitivity of these units compared to the older drivers used in the 6/7/8/17/18.

All of the bass drivers I've re-foamed (taken from (7/8/18/18S) with the correct high compliance surrounds have measured around 25Hz for Fs (+/- 10%).

I also recently replaced the cloth surrounds on a pair of AR4xa drivers and the Fs sits at 30Hz.

[Steve F]

Those Fs figures are spot-on original specs for the foam 7/6 woofers and the cloth 4x-type woofer.

Amazing--not many people realize this: I've worked in the loudspeaker biz for decades--Bose, Boston Acoustics, Atlantic Technology--and the vast majority of 12-inch woofers in the last 25 years or so have an Fs of around 25Hz. 12-inch, not 8-inch.

8-inchers are more likely to be in the 35-45Hz area.

These Classic-era AR woofers were really something. Try to find an OEM 12-inch woofer with an Fs of 17-18Hz like the 3a. If--IF-- you can find one, it will run you $200 each, easy.

At AT we made some really excellent 12-inch sealed powered subs, but any reasonably-priced available drivers were all in the 25-30Hz Fs area. When you have onboard amplification, you can EQ the final FR to be anything you want, so it wasn't an issue. But if we were trying to make a passive full-range system, that FS wouldn't fly.

AR did things with reasonably-priced drivers to make modestly-priced systems have amazing bass response that has never been equaled, even to this day.

Steve F.

[der]

Great information Steve. This, in part, is the reason we hang on to and nurture our 50 year old AR loudspeakers. I've heard other speakers that I've liked over the last 50 years but none that I considered replacing my AR's with.

der

[Alessandro]

On 14 maggio 2013 at 4:43 PM, michiganpat said:

FWIW, the actual AR17, AR18, and I think AR25 woofer is the 200001, which IIRC is the same PN of the AR6 and AR7. the ones in my 2 pair of AR18's are this part number, with a flat, heavy cardboard dustcap like the 200036 under a porous cloth dome dust cap. They are also the lower woofer in the AR94, and I thought the midwoofer in the 94 was the 200036.

I'd probably use the '37 or '36 as a replacement....my SWAG with the '35 with the white dust cap is probably heavier to add mass to reduce Fs (which would also reduce sentivity) since those are more or less the "subwoofers" in the 93's setup (not a true 2.5 way as the '36 is high passed with a big NPE)

Hi,

I think I can confirm that it is correct as stated by "ra.ra."

Alessandro