Carlspeak

Mark: For your item 1) question, check out Wikipedia.org's Acoustic Research write up. It's not bad and probably could be edited a bit to suit your needs. It's all about the music Carl Carl's Custom Loudspeakers

Attached are some photos of an original and upgraded crossover. The particular speakers I worked on for a customer had the 3 position switch, 3 ohm resistors and 10 uF cap and one #4 coil attached to a ceramic magnet woofer #200001-1. Also included on pg. 2 of the .pdf document are response curves showing the relative changes in the tweeter's response to the 3 position switch. Response changes about plus and minus 2-3 dB. Crossover point appears to be in the 1200-1400 hz range. Vintage is 1970's. Ser. #041326. This speaker had 425 grams of FG stuffing. Cabinet vol. calculated at 0.68 cu. ft. yielding a rather high stuffing density of about 1.4 lbs/cu. ft. This .pdf document is offered to add further information to the AR6 discussion. It's all about the music Carl Carl's Custom Loudspeakers

I did not use an amp between the function generator and the crossover. The function generator's output impedance across the plus and minus clips was 20 ohms. After re-assembling the crossovers into the cabinets, I ran some response curves using a special pink noise signal and a mike located about 4 inches from the baffle board and centered between the tweeter and mids. The woofer was not yet installed. Attached is a scan of 5 superimposed curves I generated. The results support your contention that the mids are not affected - only the tweeter. Curves 1,2 & 3 show the increase in output in the 2-9 kHz range. Curves 4&5 show the bulging response of the tweeter as the switch was moved to the mid and hi positions. It's all about the music Carl Carl's Custome Loudspeakers

Pete: If you ever get another chance to talk to Andy K., could you ask him if it was general practice back then to 'voice' capacitors when the designer/developer was in the final stages of identifying specific components to purchase in quantity for crossovers going into a new model. Thanks, It's all about the music Carl Carl's Custom Loudspeakers

>Let me guess, Carl: Are those my crossovers, by any chance? >;-) YUP! :-) They will be done next week It's all about the music Carl Carl's Custom Loudspeakers

While working on the repair and component upgrading of the subject crossover, I became curious about exactly how the two function switchs affect the frequency response. The switch markings on the back of the speaker are rather vague (i.e. the 2500-7000 switch I call switch "A" has a 'lo, mid and hi' setting). The greater than 7000 Hz switch I call switch switch "B" has the same markings. But, what do they accomplish exactly acoustically? The model 5 brochure claims "far more precise and repeatable adjustments than do the simple variable resistors offered for high-frequency adjustment of most multi-speaker systems." I thought that a bit ambitions; claiming a 3 position switch could be more precise than a rheostat of the type used in the early Acoustic Research speakers. Anyway, using a function generator, Tenma digital dB meter, spare cone midrange and dome tweeter (neither are KLH products), I generated 108 data points via separate dB measurements of each driver at 6 different frequencies (2-12 kHz @ 2kHz intervals) while changing the two switch positions in 9 different combinations of settings. Obviously, because I used NON KLH drivers in the tests, I can't say with any certainty, what would occur with original KLH drivers. However, I expect the general up/down trends to be about the same. Here is what I found. (Write me directly at the email address below and I will send the original M'Soft Excel file containing the raw data matrix, charts and additional details of the study). Please ignore the absolute dB readings. Only the trends are of value in this study. There is no explanation why the drop in dB level in the midrange at the 4 and 12 kHz levels. The function generator power setting was set constant for each driver over the frequences tested but was lowered to a starting level of 80 dB for the more efficient midrange driver. 1)At 2 kHz level there was virtually no change in output of either driver at the "A" lo switch position. 1-2 increase in dB level was measured at the mid and hi positions when switch "A" was moved to the mid and hi positions. 2)At the 4 kHz level, the tweeter increased about 7 dB going from lo to hi settings. The midrange stayed about the same or dropped a few dB at the "A" switch mid and hi positions. 3)At the 6 kHz level, the tweeter responded about the same with about a 3 dB increase going from lo to hi. The midrange driver dropped a bit again as in 2). 4)At the 8 kHz level, about the same results as the 6 kHz level. 5)At the 10 kHz level, there was about a 2 dB increase for the tweeter going from lo to hi. The mid dropped again. 6)At the 12 kHz level, the tweeter increased 3-5 dB while the midrange behaved the same as in 2)-5). carlspeak@aol.com It's all about the music Carl Carl's Custom Loudspeakers

Here's a pic of Tim Tyson's AR1 from the library. I realize it's not a 1x It's all about the music Carl Carl's Custom Loudspeakers

>>Interesting discussion. >> >>Peter would often sit in the listening position with the >>crossover in his lap, and with long leads going from the >>crossover to the speaker. This way he could change and >fine >>tune the settings easily and quickly. Once a design was >>finalized, a reference speaker would be retained at the >>factory, against which all production speakers would be >>individually hand tuned to achieve an identical result. >In >>addition to basic driver level and crossover point >variations, >>these adjustments are used to fine tune the phase >>relationships between the drivers affecting time >alignment. >>Without having the reference system at hand to perform >this >>critical tuning, any attempts at 'upgrading' the speaker >>beyond simple wire and connector changes is almost >certainly >>doomed to failure. Peter's designs are a classic case of >how >>careful implementation becomes far more important than >using >>expensive designer parts that don't work happily >together. > >Thanks for the info, Michael. It's great to hear these first >hand stories about Peter Snell. I still want to get a pair of >A's, when I have the room (I presently have JII's, original >K's and EII's, the latter two actually set up). It's been a >surprisingly long time since I've seen them come up for sale. > >Your home theater set up sounds... big. > >I wanted to ask you more about this crossover tuning. This is >more or less what Audio Note does, as well. When you say Peter >used a 'hand tuner,' I assume you're talking about a >potentiometer of some sort? I'm just trying to get a sense of >what parts in the xover were actually hand tuned. The >inductors are custom wound, but the capacitors, I imagine, >would stay the same, as would the resistors, correct? Are you >saying the drivers had a certain output, and the inductors >would be wound to complement that, correct? > >I guess my question is, what are the hand tuned components of >a snell xover? I think the answer is inductors and the >wirewound resistor on the tweeter, matched to the output of >the drivers. > >Dake All the Snells I've upgraded or repaired had a unique sliding wire wound resistor in series with the tweeter. Loosen a screw and one could affect the series resistance by sliding the connection along the wire wound body. This may be all that was done. It's a clever way to match the SPL of the tweeter to the rest of the drivers. The only other thing I suspect Peter fooled with where the caps. He had all sorts of strange combinations of capacitors wired in series and parallel in order to get the capacitance he was looking for. In retrospect though, IMO it may have been his way of using the ones he had in stock to come up with a uF value he didn't stock. It's all about the music Carl Carl's Custom Loudspeakers

".....Yes, the AR-2AX has the flat front wire meshed cone driver with fiberglass as it's midrange driver. This third party driver was also used as the earlier AR-4, AR-1X, AR-2X mid/tweeter driver..." I have a pair of these I'll sell for $30 Plus shipping if anybody wants them. It's all about the music Carl Carl's Custom Loudspeakers

Vern. Are you sure those are tweeters and not the mids? I've worked on some 2a's and can confirm what you are showing are the midranges which measure about 5 inches. They were the predecessor to the flat and dome mids to follow in later versions. I've got a pair of salvaged flat dome mids from a pair of 2a's. The AR history table in the library does not show a pair of tweeters for the 2 or 2a. It does list a pair of 5 inch mids for the 2a. It's all about the music Carl Carl's Custom Loudspeakers

....I have removed the domes from a number of the later, black 3/4" dome tweeters, and found crumbling deteriorated foam. Roy Yipes! Doesn't that mean there would be a deterioration in the tweeter's performance? Sounds scary to me considering the number of vintage 3/4 inch AR tweeters out there. It's all about the music Carl Carl's Custom Loudspeakers

>Does anyone have information on the original Model Four? I'm >trying to find any test reviews on this speaker. I have some >historical data, but no test reviews. I'm not sure if the >speaker was formally reviewed, but I do not know. > >--Tom Tyson Tom: You can try browsing the web site at the link below (if you haven't already). It's a very comprehensive compendium of audio reviews from Audio, Stereo Review and High Fidelity magazines - some going back to the 50's. There's a pretty good collection of early AR reviews as well. Each review is a few dollars. http://www.roger-russell.com/magrevaudio.htm#a1968 It's all about the music Carl Carl's Custom Loudspeakers

Wow, it looks like the pot took the brunt of some high voltage from a cranked up high powered amp. That may be your whole problem with the tweeter. Have you tried bypassing the pot to see if the tweeter still works? The 4.7 uF cap is a fairly common crossover cap for modern tweeters rated at 8 ohms nominal impedance. It's beginning to look like you've got a bastardized speaker there. Have you checked both to see if they are outfitted the same? For your reference, I've attached a schematic I drew from an un-altered 4ax. It had a 3/4 inch dome tweeter. The schematic shows exactly what wires go where and how to wire a new pot. Note the cap is 20 uF. Good luck and I hope the problem is just the fried pot. Remember, it's all about the music Carl Carl's Custom Loudspeakers

>Hi all >I just picked up a pair of AR4x speakers (my 3rd pair) and >they're in rough shape. pulling the grilles I found that some >previous owner replaced the tweeters with some no-names. I >figure I'll watch ebay for some original tweets, but I have 2 >questions: >1. Besides watching for "AR4x" tweeters, are there >other models (or even brands) that are correct replacements? >2. I read somewhere that early 4's had cone tweeters, but >later 4's had dome tweets and the domes were superior. True? >Should I hold out for domes? >I'm attaching photos of the front & back of the no-names, >in case anyone recognizes them and can tell me if they are >worth keeping. >Thanks! The 24 XXXXX may indicate it is a Becker manufactured speaker. Do they sound okay? Are the pots not part of the problem? I recently bought a tweeter from AB Tech for an AR 4x speaker. It fit and sounded fine. One slight problem though. It was significantly more efficient than the woofer. I had to turn down the pot almost completely to match the SPL's. Carl Carl's Custom Loudspeakers

>>Thanks Roundsound. >>What was the list of woofers at the bottom of your post >all >>about? Were they supposed to be links to other specs or >were >>all those the same as the 1210130-1? >> >>Remember, it's all about the music >> >>Carl >>Carl's Custom Loudspeakers >Those are other woofers I have specs for just can"t type >for vary long >Jim Well thanks Jim. I have much patience and will await further postings on this subject from you. Regars, Remember, it's all about the music Carl Carl's Custom Loudspeakers

Thanks Roundsound. What was the list of woofers at the bottom of your post all about? Were they supposed to be links to other specs or were all those the same as the 1210130-1? Remember, it's all about the music Carl Carl's Custom Loudspeakers

>Would anyone here have the T/S specs on the AR 9 woofers? >Also what is the net cab volume of the AR 9. > >Thanks DC I'd like to expand that question a bit further - "Would anyone here have the T/S specs on ANY AR woofer?" Remember, it's all about the music Carl Carl's Custom Loudspeakers

>PM, > >It appears that the earlier version AR-2ax equipped with the >cloth surround woofer contains 28+/-oz of rockwool, and the >later version equipped with the foam surround woofer contains >18+/-oz of yellow shredded fiberglass. This is based on >measurements I have taken of a number of AR-2ax specimens in >the last two years. Roy - I have to wonder what really drove the reduction in stuffing weight between the two woofers. Was it the foam surround? A different woofer altogether? different coil? or, simply the yellow fiberglass accomplished the same target Q as the rockwool did? Here again, we need some factual AR history to answer these questions. > >Of four early '70's AR-5's (same cabinet as 2ax with a >slightly different foam surround woofer) I have weighed only >yellow shredded fiberglass ranging from 20oz to 21oz. > >Roy Thank you Roy for some additional data on another classic AR speaker. In an effort to help answer P.M.'s question, I tested a pair of original AR 2a woofers I salvaged and did some calculations on box Q and stuffing quantity. The speakers I tested were 11" od and had original cloth surrounds and + & - terminals on opposite sides of the magnet. Results for both were very closely matched. Below is a summary with nominal values Fs = 28 Hz (seems high relative to Villcur's AS patent stating 18 Hz as ideal. Perhaps the spider has stiffened over the past 30-40 years?) Qts = 0.51 Vas = 6.35 Cu ft. Mms = 29 gms Eff = 89 dB. An AR 2a box internal volume is slightly less than the AR 3a. I estimate it to be net 1.3 cu. ft. with bracing taken into consideration. With that box volume and the above T/S parameters, I calc. a box Q or Qtc of 1.24 for a non-stuffed box using the formula: Qtc=Qts*sq.rt.(Vas/Vb)+1). It is generally accepted that 100% fiberglass stuffing material will add about 18% to the effective volume of an AS speaker. Recalculating Q with a new Vb of 1.53 cu. ft yields an expected reduced Q that computes to 1.15. At this Q, there will be a theoretical response ripple at box Fs of about 2 dB. P.M. Summer: If you use standard 3 inch thick OC R-19 fiberglass as stuffing material, it's uncompressed density is 1 lb/cu ft. Thus for a 1.3 cu. ft box, 20.8 oz. should be used. This is very close to what Roy measured with yellow stuffing. Remember, it's all about the music Carl Carl's Custom Loudspeakers

>RE: stuffing density > >Stuffing *density* is not the appropriate parameter by which >early AR speakers should be compared. A major issue for the >designer was setting the cabinet Q correctly. If too little >stuffing, the cabinet would be underdamped, if too much it >would be overdamped. AR's designers determined the appropriate >stuffing weight to meet each speaker's design parameters; the >final weight in a given speaker did not yield a common >density. Examples: > >Early AR-4x: AR-#4 woofer coil-- 18 oz. (511 gr.) fiberglass >or 1.7 lb./cu-ft. > >Later AR-4x: AR-#5 woofer coil-- 12 oz. (340 gr.) fiberglass >or 1.15 lb./cu-ft > >Early AR-3a (sn >magnet woofer-- 28 oz. (795 gr.) fiberglass or 1.18 >lb./cu-ft. > >Late AR-3a (sn > ~39,500): AR #9 woofer coil, ceramic >magnet woofer-- 20 oz. (567 gr.) fiberglass or 0.844 >lb./cu-ft. > >All AR-4x and AR-3a cabinets have interior volumes of, >respectively, 0.65 and 1.48 cu-ft. The stuffing weights many >of us have measured were within ~10% of the design value. > >These numbers are only for fiberglass. When using an alternate >fiber, a different quantity will be required to obtain the >correct damping; but other parameters will not be the same. Thanks for all the details John. I understand the designers needed to target a box Q in developing a new speaker that didn't exist. I was simply trying to establish some historical emperical data on some of the more popular AR speakers and the effects various stuffing materials. Your response is most welcome in filling in most of the blanks. You have also verified the initial data point in my results table. The AR 4x speaker I used did indeed have #4 coil and my results closely match the stuffing density you listed above. But, I also have to wonder why my 0.9 lb/cu. ft Owens Corning glass trial matched my initial data point so closely. Your apparent wealth of AR facts and details has raised some questions in my mind: 1) Do you know exactly what Q were they targeting for for various models? something in the range of 0.5-1.2 perhaps? My BassBox Pro Qtc results from my Qts tests on the 8" woofer in a heavily stuffed .625 cu. ft box resulted in a Qtc of slightly over 1. Is this anywhere near the designer's target for that speaker? 2) How did the engineers measure Q back in those early days? Was it 'seat of the pants' trial and error or was some science used? 3) Villcur's AS patent mentioned Q briefly relative to the use of fiberglass stuffing but didn't mention any target in his claims. When did the AR engineers adopt the use of T/S parameters in loudspeaker design? 4) Did the AR engineers go back and measure the Qts of some of the prior woofers following publication of the Theil/Small AES papers? Surely spares were still around in the early 70's. The engineers would have gained mutch knowledge from such data. 6) If that data was collected, could someone like yourslelf share it with us mere AR mortals? I find posts from time to time that give glimpses of AR facts on the 'classic' speakers from the 60's and 70's. Your box stuffing info is a glaring example. Surely, there must be some people around that worked at AR in its heyday who could share some memories and/or facts from those days. AR posts are far and away the most active of any speaker discussed on these pages. That kind of information would be of great value to many of us around the world who visit regularly that are trying their best to be as accurate as possible with their salvaging efforts of those classics. Remember, it's all about the music Carl Carl's Custom Loudspeakers

Two new data points to share with you all. I just finished opening up 2 AR 3a speakers. I'm preparing to replace the pots and upgrade the tweeter caps. One had no serial #. The other was marked #68861. Each contained the more recent yellow fiberglass. It was completely removed from each cabinet and weighed separately. The unmarked cab. was 590 grams. The marked cab. was 515 grams. The inside dimensions were measured and some allowance for bracing was subtracted from the total internal volume. The stuffing density calculated to about 1 lb/cu. ft and 0.81 lb/cu. ft respectively. The median of these densities falls in the range I found was quite satisfactory (0.9 lb/cu. ft.) for OC fiberglass in my study using AR 4x speakers. Remember, it's all about the music Carl Carl's Custom Loudspeakers

FYI all. New flyer from Old Colony Sound Labs shows the Loudspeaker Cookbook is in its 7th Edition and the price is reduced from $40 to about $28 until Dec. 29th. Remember, it's all about the music Carl Carl's Custom Loudspeakers

Okay posters, I have to eat some crow here. In the first paragraph of my report, I mentioned that little had been published regarding this subject. Today, I was browsing thru my copies of the first and fourth editions of Vance Dickason's Loudspeaker Design Cookbooks. In the first edition he devoted a couple of columns to AS speaker stuffing. He targets a starting point of 1.5 lbs/cu.ft. which is midway in the range I explored. He also referernces Chase's 1974 IEEE paper which, I believe, has been discussed here already. However, when I opened up the forth edition to the same subject area I discovered Vance had expanded his discussion to almost 9 pages and included a new detailed emperical study somewhat similar to mine, but much more comprehensive in the measurements taken. Numerous impedence and SPL charts are presented for the 17 stuffing variables studied. He doesn't reveal who did the study or when. A larger box (52% larger) was used than what I used. However, his study used the same size woofer. This seems to me to be a rather large box for the woofer used. It's outside David Weem's recommended box volume vs woofer size chart depicted in his 1984 Tab publication: "Building Speaker Enclusures". It's not clear to me what effect the difference in woofer/box size relationship might have on the outcome of such a study. I guess that's another varible worthy of further study? I won't go into any further detail here regarding the study results published in the 4th Edition due to potention copyright infringement issues. However, I do recommend those who seek further information might want to pick up a copy. The Cookbook now is in a much later edition. The 1st ed. 1987. 4th ed. 1991. Who knows what may have been published beyond the 4th ed.? Remember, it's all about the music Carl Carl's Custom Loudspeakers

I would tend to agree with Dynaco Dan's theory. The pumping action of the woofer pulls and pushes air back and forth thru the grill cloth. Any 'stuff' in the air - and those of us who clean house know, will get captured in the microfigers that stick out of the strands and build up over many years of use. I'll stick with this theory until a degreed chemist can convince me otherwise. Remember, it's all about the music Carl Carl's Custom Loudspeakers

>Just a thought... > >Having just recently jumped back into vintage AR (after a 30+ >year absence), I've noticed a couple of thing: some AR >speakers have pots shot to hell, others simply need a >cleaning; AND some grills look fine, while others are badly >stained (darkened) over the cut-outs. > >In my LIMITED experience there is a correlating factor: rock >wool. > >The ARs with fiberglass stuffing have pots in better condition >(as has been discussed), and the grills don't have as much (or >any) darkening of the cloth over the grill cutouts. > >Isolated, or is the sulfur leeching out of the rock wool also >darkening the cloth? > > Is there a chemist in the house that might be able to answer Mr. Summer's question? Having posed that question, I wonder how the sulfur can get past the sealed drivers. Could fumes leak thru the "porous" cellulose speaker cones or screen dust caps? The grill cloth is made mostly of linen but I suspect the original stuff also had strands of burlap in it. Remember, it's all about the music Carl Carl's Custom Loudspeakers

>>What brought me to this is the large number of posts and >views >>of the brown stuffing post. I thought I'd evaluate some >>alternatives to rock wool. I think I've found 1 or 2. For >>those of you cleaning or replacing those corroded pots, >please >>consider throwing out that old rock wool and replacing it >with >>something more friendly to those cleaned up pots and less >>dangerous to work with. >> > >Both fiberglass and rock wool are non-flammable and won't melt >at any temperature likely to be found inside a speaker >enclosure. Previous posts here indicate that the pots used in >AR speakers can get quite hot. Replacing the fiberglass with >poly-fill would require evaluating the risks associated with >replacing non-flammable fiberglass with a flammable stuffing. > Thanks Joe. Your point is well taken. If polyfill is what someone wants to use, perhaps a simple cover could be fabricated to cover the pots and keep most of the fiber away from them. If ohmites are used to replace the Aetna-Pollak pots, their wipers are completely exposed and a cover is necessary anyway to avoid shorting. BTW, the melt point of polyester is about 450 deg. F. That's pretty darn hot. It's hard to imagine a 25 watt rated pot could get that hot. But, then again, Vern's fusing recommendations make all this discussion moot should they be followed. Remember, it's all about the music Carl Carl's Custom Loudspeakers