dynaco_dan
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Posts posted by dynaco_dan
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Hi Pete;
Good write-up, thank you.
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>Interesting Vern,
>
>Yes I'd agree about prototypes and spot checks, makes sense.
>I'd read about the partioned cabinets for the A-35 and 50 but
>have never had a look inside one.
>
>Thank you,
>Pete B.
Hi Pete;
AR used to show in a photo, that of a tester, using a stethoscope to test an AR speaker for cabinet resonances.
I felt, that, they were saying, that, they tested each and every one.
Maybe, I wasn't the only one thinking that, at the time.
Buried somewhere, is all of the measurements from an A-25, A-35 and A-50 cabinet from when I serviced them.
I also have Dynaco literature which shows drawings of different A-50 partition locations, as well as different versions of the basic Dynaco 400 amplifier.
I think sometimes the engineering, manufacturing and sales lose touch with each other, the sales have brochures drawn up pre-matureley.
The material that covered the internal vent opening was, typical felt material, it covered the internal hole.
I never tried to remove the felt to see if it was on the other surface of the partition.
When I dig up those notes, I'll add to this topic in the future.
I have A-25's, A-35's and A-50's, I tend to just use them and not take them apart.
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>Hi Vern,
>
>Thanks for the dates of those reviews. I might look them up
>one day.
>I do remember the old Dynaco literature that mentioned tuning
>each A-25 with a 5 Hz square wave. I think this was marketing
>hype, every A-25 I've seen has been stuffed the same way. I
>do also think they showed the tone burst tests. I do think I
>have that around here somewhere but I've not had my finger on
>it in some time.
>
>Best,
>Pete B.
Hi Pete;
You are very welcome.
I feel that they did perhaps have to do a bit of fiddling around for the prototypes.
Afterwards they quite likely ordered either rolls of a certain thickness and cut them into pieces or ordered the pieces in bulk.
I am also certain that they would have done spot checks, to be certain of their suppliers quality control.
It would be interesting for an employee of that company to reply.
Also a write-up regarding the relationship of Scan, Seas and Dynaco, would be of great interest, as well.
As a side note, the A-35 and the A-50 had an internal divider/partition with a vent opening, no external vent openings.
I believe yhat they used a felt type material, as I remember, to cover one side of the internal opening, not fibreglass.
Those memories are from the early '70's, I am certain that there were no details that I forgot about these models.
The divider/partition in the A-50 was done in two internally different locations, as well.
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Hi Pete;
>I don't know about any 9-10 kHz resonance,
My comment was from an Audio magazine un-dated review about a 9khz small peak.
They found a 10khz small peak in the June/69 issue of Stereo Review and more interesting, they also did a tone-burst-response-photo at that same 10khz peak.
Obviously it had no negative effect, as it was published in Dynaco's 22 page brochure D669.
it's probably
>inaudible if it's just a few cycles of ringing.
You appear to be absolutely correct in your comment, Pete.
Was this tone
>burst testing, as was common in the old days? I don't think
>I've seen any A-25 reviews in a very long time, except for
>those in Stereo Review for the A-25 and A-50 which are not
>very detailed and mostly praise them. I did look on the web
>recently. Who were the authors of these reviews?
>
>Pete B.
Also High Fidelity magazines review July/69, there was no mention of any peak.
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>If Cizek had more than one model of speakers, then why in the
>hell are they so hard to find? Where did most of the speaekers
>end up anyways? I seen a very impressive photo of the dual
>Cizek subwoofer, on the forums here. Does anyone have one of
>those? By the way does anyone have a picture of Roy Cizek.
>Cizek seems like such a mystery to me and I want to know more
>than what I've read here. Sorry for all of the questions, but
>I just find Cizek so fascinating.
>
>Sincerely,
>Brian
Hi Brian;
If I had not come to this web site, I would never have even heard of Cizek speakers.
From what I have read here, those that own them, cherish them.
Paolo, a valued member, is very likely the most knowledgeable member on Cizek speakers.
He really cherishes his Cizek speakers and has been very helpful in helping both the members and the library with literature.
I feel that he will try to assist you with you questions, if I know Paiolo, and if he has the spare time, he is a very busy man.
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Hi pete;
I did not read your write-up as being cranky, just informative, as usual.
Thank you though, Pete.
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Hi again;
I forgot that, Carl, did a really excellent and unbiased grille cloth review recently, in the AR forum.
He evaluated the original, versus several lookalike cloths available today through his speaker repair service.
Appearance is one issue, but sonic neutrality of the cloth is most important as his review points out.
A very interesting read for anyone attempting to find just a replacement cloth without any knowledge.
The job of replacing the correct cloth, with at least as close to neutral as possible, takes the same effort, as the wrong cloth.
Price also in not an indicator of what cloth is suitable.
Carl, put a lot of labour of love into his report.
Good luck.
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Hi Pete;
Always nice to read your write-ups, Pete.
I personally have not heard double Dynaco A-10, A-25, A-35 or A-50's, yet.
I have enough A-25's, both versions, to try something in the near future.
I plan on seeing if I can hear a difference between, the Seas and Scan, versions.
It is particularly noteworthy, that, since the Double Advent's were written up in the Absolute Sound, many decades ago, that no other reviewer or manufacturer ever did a double's trial of any model, that I am aware of.
Since I started comming here, a few members have tried and commented briefly on several smaller, the AR-LST's are the biggest, speakers.
There was something, "magic", with the Larger Advents, it seems.
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Hi Pete;
Nice write-up, as usual.
I wonder what tilting the enclosure does with the tweeter now being in more direct eyeshot as well.
The tweeters dispersion was satisfactory but never outstanding.
With the time tilt and beaming maybe you have just discovered a new speaker POOGE at no cost.
Have you ever tried Double Dyna's?
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Hi there;
I went to that site for a looksee.
None of what I saw, on any of their pages, looks remotely useful, sorry.
Perhaps as time goes by, other members will give you another suggestion.
I tried a solution called, "Pink Solution", which I read is carried by Costco's now.
Pink Solution is a concentrate made here in Vancouver.
You water it down per instructions.
I tried a patch test on an AR grille cloth, looks very promising.
In the near future I am going to sacrifice that entire cloth to complete the job.
I am going to lay the cloth and frame in a 1/16 - 1/8" bath so I will see the effects on the frame as well.
If I am successful or not, I'll post a write-up.
I would wait for better advice before spending any money, the original grille clothes were fairly neutral.
Good luck.
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Hi there;
Welcome to the site.
I believe the original speakers used Larger Advent woofers with the masonite ring.
Usually these should be able to produce sufficient clean bass.
Good luck.
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Hi Pete;
Another great write-up, as always, thank you.
More referrence material to print out for future referral.
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>Why would you take the crossover board out of the cabinet?
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Was there something wrong with the photos?
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Why would you take the crossover board out of the cabinet?
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Hi Frank;
Thank you very much for your kind words, Frank.
I look forward to everyones input here, from all over the world, even if it is above me.
Every day is a learning process for us all.
I am really looking forward to your next way out in left field humour.
I haven't recovered from your last two yet.
You really had me in stitches.
Thank you, Frank.
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>Well you can't have my 66's, if you want to look at them
>though you can look at the pic on Huw's site of the
>"series 2". I sent him that pic a few years ago.
>Along with Genesis I also like the EPI line, I have a pair of
>Epicure 2.0's (also on Huw's site) in the living room driven
>by an Onkyo reciever and my "surround" system
>consists of Human 81-10's for surrounds (and spare parts) and
>the 66's for mains. I used to have a cc and a Velodyne sub,
>but after adding a couple of 200 W monoblocks for the 66's the
>sub just wasnt needed anymore. It was only for movies anyway,
>most of their use is music. The 66's image so well that a cc
>isnt needed either, if anyone else in the family ever starts
>to enjoy watching movies at home the way I do I may have to
>add one again for the "off center" seating positions
>but unitl then....
>
>I have a friend with some Epicure 3.0's those are pretty
>sweet, compare quite favorably with the 66's (I honestly dont
>know which I like better, although I always say mine
)>
>Anyone in the midwest with a pair of EPI 1000's in working
>order, I would love to hear those.
Hi Greg;
I had an opportunity to hear a pair of 1000's a long time ago in a stereo store.
They were six feet tall and about 12 - 18" square.
At the time, a local band was blowing out all of the AR-LST tweeters, when playing back master recording tapes at their home, so finally, they took a pair of these home, and were unable to blow out the tweeters.
They were room filling and clear as I remember.
Of course we liked everything reeeaaal loud back then, and they were unfused as well.
I saw a post here recently of one in a photo laying horizontal in a garage.
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>those round-magnet woofers are not a well-regarded
>replacement for the original woofers. ok, they suck eggs, but
>somebody might like them. the best (cheapest) way to get back
>to the original sound would be to buy a pair off ebay, either
>refoamed or DIY. i am running 5 or 6 woofers that i refoamed
>myself over the last 3 years or so. no problems.
Hi there;
I certainly am not an expert, but, I believe the original The Large Advent woofers had the masonite ring.
After that I don't know what happened except I see woofers without a masonite ring.
There was a Advent/1 which I know absolutely nothing about except the name.
Can anyone clear this up for me, please.
I believe the original, The Large Advent, had a raised tweeter less screen and applied it later on.
Advent/1 had a flush tweeter which I believe had ferrofluid.
Do I have a problem with my understanding or order?
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>It's been said that most good ideas have already been done,
>and I'd have to say that this AR woofer is an example of prior
>art with regards to my thoughts on black anodizing, I didn't
>know about it at the time.
>
>I've usually seen aluminized paper used in smaller drivers and
>I'd think that a thin layer of aluminum on those Nomex formers
>would help quite a bit as far as heat sinking goes. On the
>other hand solid metal formers have the advantage that both
>sides serve as heat radiating area. One problem with pure
>aluminum is the difference in the coefficient of thermal
>expansion as compared to the copper windings, it does seem
>that they've gotten around this since aluminum is common these
>days. This is one reason that I like bronze type formers.
>
>I'm curious to know what the source material was used for your
>drum test, live recordings often have a lot of subsonic
>material that should be filtered. Vocal pops, string initial
>impact and so on. Were you running the active filter for the
>801s? It's an interesting challenge to try to reproduce
>uncompressed material at realistic levels.
>
>Keele probably half joking, referred to a system I
>particularly like as the 10,000 Watt speaker. The original
>PSB Stratus Golds will handle his short term burst test at
>10,000 W above 700 Hz. He runs a bridged Crown amp to do
>this. One has to wonder if the voltage rating of the
>capacitors is exceeded in this test. This system crosses and
>stays above the 120 dB mark (at about 4 kW bursts) from 70 Hz
>on up in Max SPL capability. I don't need this SPL level but
>it just shows how much head room is available and the robust
>construction.
>Many here talk of specs and the flat response of AR speakers.
>The first version of the Stratus Golds were rated at +/- 1 dB
>from 36 Hz to 20 kHz on axis. This is hard to believe and
>Keele was only able to confirm +/- 1.5 dB from 40 to 20 K,
>still not bad and Keele does outdoor tests with spliced near
>field woofer response if I remember correctly, so there's some
>room for error. Both specs are certainly outstanding. I
>found this hard to believe and actually measured the Thiel and
>Small parameters of the Stratus Gold woofer, then simulated
>the response, -.9 dB at 36 Hz - impressive.
>They claim hand selection of inductors and caps to a 1%
>tolerance, resistors are 2%. There are no exotic parts but
>I'd expect tight quality control on drivers. I'm just
>offering this as a comparison to a value engineered modern
>design.
>
>Pete B.
Hi there
I wrote a story a few months ago from memory about the KEF-107's and how thirsty they were.
I believe it was a report from Audio? and about 12 pages long.
A custom 5,000 watt amplifier was used.
The reviewer had commented on the fact that clipping amps had been a major limitation previously for testing speakers.
They had this amp clipping using just the tweeter section.
Maybe this is what we need, now that we can't hear as well, from playing rock music so loud when we were young.
Pardon me while I go replace my hearing aid batteries.
Have a good one.
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Hi there
Isn't digital photography a wonderful tool?
I never even spent 5 minutes really ever looking at a voice coil before, but with these pictures and the feedback it certainly makes this more interesting.
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>>>Hi there
>>>
>>>Another 2 1/2 cents worth from me now.
>>>
>>>Have you tried, Acetone, which is similar to lacquer
>>thinners,
>>>for softening the spider glue?
>>>
>>>That is all I've ever seen used up here.
>>>
>>>All safety procedures must be followed, read the safety
>>>haszard sheet, this stuff is not for inhaling.
>>>
>>>I have seen a spider come off in about 30 seconds once the
>>>glue is dampened.
>>>
>>>Just use a 1/2" wide paint brush to apply it.
>>>
>>>Good luck.
>>
>>Vern,
>>
>>I haven't tried acetone on the AR parts, but it's probably a
>>great chemical to use. Ironically, I use acetone and
>lacquer
>>thinner on a pretty regular basis on other projects, but
>I've
>>never tried them on the AR speaker glues! I think I was
>>surmising that acetone would damage urethane-foam materials;
>>but after all, there is no surround to dissolve at this
>point!
>> Both acetone and lacquer thinner are very volatile and
>>flammable, so you have to be very careful with them.
>>
>>Thanks for the suggestion!
>>
>>--Tom Tyson
>
>
>Hi again.
>
>Lacquer thinner wasn't used, but Acetone is still being used
>here locally.
>
>If I remember correctly, Acetone, is considerably more
>dangerous than Lacquer thinners.
>
>Sorry, I didn't expand upon this more thoroughly, previously.
>
>I must repeat that, "you should," "rather, "must read," the
>health haszard sheet on the internet.
>
>Also read the containers caution label very carefully and
>abide by their recommendations.
>
>Acetone is, as Tom points out, very flammable, but more
>importantly, it's not to be inhaled under any circumstances.
>
>It has an effect on the lungs, and probably the brain as well.
>DUH.
>
>It should be used either outdoors or in a well ventilated and
>exhausted cabinet or room.
>
>As Tom mentions, use caution when contacting materials, if it
>should be something like a new surround, it will disolve it
>real quick, there is no time even for oops.
>
>I have watched a local speaker repairman, from a distance mind
>you, use it for over 10 years.
>
>Thanks again Tom for your feedback.
>
>Good luck and do be careful.
>
Hi again;
I always remember something else to rattle about after I've walked away from my computer. Duh.
I am sure most of you wouldn't use acid swabs or synthetic bristled brushes for the Acetone.
I believe that the acid swabs are synthetic material.
I, forgot to suggest a natural hair type paint brush, otherwise I think you would dip the brush into the can of Acetone, and find you wouldn't have any synthetic bristles left.
Reminds me of a time I was hunting and wanted to put gas from a non-funneled gas can into my gas tank.
I used a sterifoam cup.
Ok, only this one time.
Well, the cup did fill up once, just before the bottom and the rest of it disolved. Duh. Canadian genius at work here. NOT.
Live and learn.
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>>Hi there
>>
>>Another 2 1/2 cents worth from me now.
>>
>>Have you tried, Acetone, which is similar to lacquer
>thinners,
>>for softening the spider glue?
>>
>>That is all I've ever seen used up here.
>>
>>All safety procedures must be followed, read the safety
>>haszard sheet, this stuff is not for inhaling.
>>
>>I have seen a spider come off in about 30 seconds once the
>>glue is dampened.
>>
>>Just use a 1/2" wide paint brush to apply it.
>>
>>Good luck.
>
>Vern,
>
>I haven't tried acetone on the AR parts, but it's probably a
>great chemical to use. Ironically, I use acetone and lacquer
>thinner on a pretty regular basis on other projects, but I've
>never tried them on the AR speaker glues! I think I was
>surmising that acetone would damage urethane-foam materials;
>but after all, there is no surround to dissolve at this point!
> Both acetone and lacquer thinner are very volatile and
>flammable, so you have to be very careful with them.
>
>Thanks for the suggestion!
>
>--Tom Tyson
Hi again.
Lacquer thinner wasn't used, but Acetone is still being used here locally.
If I remember correctly, Acetone, is considerably more dangerous than Lacquer thinners.
Sorry, I didn't expand upon this more thoroughly, previously.
I must repeat that, "you should," "rather, "must read," the health haszard sheet on the internet.
Also read the containers caution label very carefully and abide by their recommendations.
Acetone is, as Tom points out, very flammable, but more importantly, it's not to be inhaled under any circumstances.
It has an effect on the lungs, and probably the brain as well. DUH.
It should be used either outdoors or in a well ventilated and exhausted cabinet or room.
As Tom mentions, use caution when contacting materials, if it should be something like a new surround, it will disolve it real quick, there is no time even for oops.
I have watched a local speaker repairman, from a distance mind you, use it for over 10 years.
Thanks again Tom for your feedback.
Good luck and do be careful.
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>>>It appears that the late-70s designation of the
>200003/1210003 woofer (AR-9/AR-11B) you show is consistent the
>advent of the aluminum voice-coil former.<<
>
>Tom, I believe you are right about when AR changed from Nomex
>to Aluminum voice coil formers. When AR changed the ADD line
>from what we on the forum have referred to as "A" model ADD
>speakers -- Brass logos, White/yellow fabric on tweeter, black
>screen on midrange... The 200003 woofer was the same as that
>used in the AR-3a and AR-LST -- Black flange, wide masonite
>ring, hex screws...
>
>I have my Dad's AR-11 "A's" here with me. I just pryed up a
>small portion of one woofer dust cap (a replacement porous
>dustcap installed by a shop he had refoam the woofer for him,
>it isn't glued down very well) --
> Nomex VC former, just like the AR-LST woofers I refoamed a
>few years back.
>
>All the AR-11 "B", and AR-9 200003 woofers I've refoamed are
>the silver flange version -- all have Aluminum VC formers.
>Pretty good indication this is when the change from Nomex to
>Aluminum was made.
>
>>>One way to help in removing the glue on the woofer flange is
>to use denatured alcohol to soften the glue, and then
>carefully scrape away.<<
>
>Just to add my techniques --
> I've used "Goof Off" and Isopropyl alcohol to loosen the
>glue. The alcohol works better than the Goof Off. I use Q-Tips
>saturated with alcohol to "scrape" the foam remnants away
>before going after the glue.
>
>The best tools for scraping the glue from the masonite ring
>and the outer edge of the cone are razor type knifes --
>X-acto, Stanley retractable blade knife, Box cutter/Wallpaper
>razor knife with break-off blades. Whatever type knife you
>use, use the BACK OF THE BLADE (not the sharp edge) to scrape.
>You will not cut the cone or damage the masonite when you use
>the back of the blade.
>
>>> It's slow, laborious work, but a clean surface is mandatory
>for good results.<<
>
>Absolutely.
>
>Rich
Hi there
Another 2 1/2 cents worth from me now.
Have you tried, Acetone, which is similar to lacquer thinners, for softening the spider glue?
That is all I've ever seen used up here.
All safety procedures must be followed, read the safety haszard sheet, this stuff is not for inhaling.
I have seen a spider come off in about 30 seconds once the glue is dampened.
Just use a 1/2" wide paint brush to apply it.
Good luck.
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>>Hi Tom,
>>
>>I'll weigh them at some point if I get a chance. The former
>>must extend past the windings somewhat as with most voice
>>coils, do you know what that dimension is?
>>
>
>Pete B,
>
>To answer your question, there is about a millimeter or two
>above the coil winding, and quite a lot below the windings.
>The voice coil is 2-inches in diameter and about 1.02 inches
>in length. Following are images of two damaged AR#200003
>voice coils:
>
>(1) This AR-3a voice coil was bottomed during strife-testing,
>and the nomex former and coil suffered slight damage at the
>edge where the coil touched the back plate in 1+ inch
>excursions during sine-wave testing.
>
>(2) This AR-3a voice coil was heavily damaged by extremely
>high power at low frequencies, causing the coil to compress
>the former when the coil hit the back plate violently. This
>coil bottomed repeatedly before deforming the bobbin.
>
>--Tom Tyson
>
Hi Tom
With the quality of your photos, I wish I could go back in time, to when I was working at the AR local warantee depot.
When a picture is worth a thousand words, this is a great example.
It might be difficult for the average reader, who may never have seen a voice coil in their life, to imagine this type of damage.
The photos I would like to have shown, would be, Dynaco A-25 woofer
voice coils burnt like toast, without exaggerating, charred.
Common with SCA-80 and Q models which were exremely popular here, at the time.
These two were mentioned only to show that the power was adequate for hifi, not disco or rock levels.
AR-3A voice coils, after being plugged into an AC outlet in error. OOPs.
Certainly gives, a 1 amp fast blow 25 cent fuse, a certain feeling of some security from that type of damage.
Your quality photos, sure make this web site, much more interesting, to be sure.
Thank you, Tom.
)
AR pots & L-pads AR-2?
in Acoustic Research
Posted
Hi there;
AR pots and L-pads used in an AR-2 speaker system?
I am choosing the, AR-2, as an example only, I am certain this was not the only model affected by this topic.
I am writing this because, with all of the write-ups I have seen, I find it overwelming, I cannot read between the lines, as to which is or not correct to use.
I have read, that some listeners do not like the sound with the L-pads.
Why not?
What does a pot do, that an L-pad doesn't?
What does an L-pad do, that a pot doesn't?
This is a simple question, yeh sure, regarding the past and present purposes of both items.
I have come across what appears to be L-pads, rather than pots, in old AR-2 speakers, which I have not opened, yet.
They turn with considerable ease, smoothness, lack of resistance, and quietness compared to the Aetna-Pollock pots.
This was done without any audio connections.
Am I correct in my assumption?
Did AR start out using L-pads?
When and why, did they switch to the 16 ohm pots at some point?
What does the pot do to the AR-2 tweeter output, if plotted on a graph?
What effect does the potentiometer have with the tweeter output, with the pot at maximum to start with?
A. Does decreasing the tweeter output, cause the total tweeter output to drop horizontally equally, from the crossover to the maximum output?
B. Or does the tweeter output start at the extreme top end and slowly start reducing the topend highs of the tweeter, such as an AR amplifier treble control?
I am certain that A. is correct, but, I would appreciate a techies input please.
Also if an L-pad was used, what would happen to a graph profile when the L-pad was slowly turned down?
C. Does turning an L-pad down, cause the entire horizontal tweeter output to lower equally?
D. Or does an L-pad, cause the tweeter output to lower itself starting from the extreme highend tweeter output, such as an AR amplifier treble control?
If an L-pad was used, is replacing it with a pot a simple and worthwhile operation?
Looking at an AR-LST literature profile, I can see the switched steps of the tweeter, with no difficulty.
I realize this is also a stepped switch via the autotransformer.
I hope I made this simple question clear?