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Honorable mention of AR products in A-25 review


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In the review of the A-25, there are several mentions of AR products. I guess at the time of this review, AR was the standard against which everything was compared.

http://www.stereophile.com/content/dynaco-25-loudspeaker#KOozMceFiJCv3uCu.97

Anyone know whatever happened to the "aperiodic" design?

Today most speaker systems are ported, but there are a number of sealed bookshelf systems. Further, some of the best subs around are sealed boxes. I can't remember ever seeing a modern aperiodic system.

Regards,

Jerry

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I’m surprised no one else has chimed in here yet. The thing about this review that has got to strike any avid AR enthusiast/historian is the remarkable degree of inaccuracy and carelessness with which Holt refers to AR speakers. He casually and randomly conflates the 3a, 5 and a fictitious “5a,” and calls the 5 the “successor” to the AR-1. He says the 3a was virtually flat down to 25Hz, which, of course, is ridiculous and just a further indication of his total lack of intimate knowledge and familiarity with AR. He should have known, because the specs were published: System resonance: 42 Hz. Sealed is a 12dB/oct rolloff below system resonance (he should have known that too—Julian did!), so it’d be -12dB @ 21 Hz. 25 Hz would be around -8 or -9dB. Hardly “flat.” C’mon Gordon!

His characterization of the behavior of acoustic suspension and its operating principles are also off base, by just enough, again, to betray his lack of true understanding. This is the “legendary” J. Gordon Holt, the dean and originator of the oh-so-sophisticated “high end” review.

In fact, this review is far less technically or historically accurate than what Julian Hirsch was doing at Stereo Review or what the editors at High Fidelity were doing.

The Dynaco A-25 was a terrific speaker and like the Classic ARs, they’ve stood the test of time and still sound great. But Holt’s mentions of AR serve only to reveal his embarrassing lack of understanding and familiarity. This was cringe-inducing to read.

Steve F.

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Steve, do you know whatever happened to the aperiodic design?

From what I've read, aperiodic is essentially acoustic suspension with some "tweaking".  In short, the vent is used for pressure relief NOT for sound augmentation as in ported or reflex. I also understand that it is "tricky" getting the vent stuffed correctly.

 

Regards,

Jerry

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On 4/20/2017 at 2:43 PM, genek said:

I don't read Stereophile. It's probably the least credible hifi publication I've ever read. 

Dear gene, I read both TAS and Stereophile.

Both publications are obviously suffering because there is so much information available on the net.

Although I prefer TAS, Stereophile does have a number of good reviewers but, I'm curious as to why you're not so keen on Stereophile?

"Least creditable" in what way?

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My experience trying to read both TAS and Stereophile date back to days of measurement vs golden ear reviews. Both of those publications were the epitome of the "our ears are so good we can hear things that can't be measured so why measure" school of audiophilia. Or have they changed?

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17 hours ago, genek said:

My experience trying to read both TAS and Stereophile date back to days of measurement vs golden ear reviews. Both of those publications were the epitome of the "our ears are so good we can hear things that can't be measured so why measure" school of audiophilia. Or have they changed?

Hi Gene, not sure if I can speak to your point other than I've been reading Stereophile on again and off again since 1988-89 or so and I subscribed to TAS in 2005.

I will say that a couple of the recent reviewers aren't any better at reviewing than I might be except that I'm sure they probably get all kinds of help and opinions from the-more experienced ones there before they go to press. I do appreciate some of the older more seasoned and experienced reviewers though.

Of course most every component reviewed is ridiculous in price, whether or not the end results are similar is a matter of taste listening preference.

AD, JV and couple of others are some of my favorite reviewers.

Regarding the amount of time these publications remain in their positions is another story, especially when they duplicate most of the printed version on line. However, the written page I hope remains supreme.

The European publications are very costly and to me, aren't worth their cost.

Personally, I browse through them simply to stay abreast of what's current just like I did with the big-three in the early seventies.

Other than that fact, the cost of equipment is in the stratosphere that even thumbing through these magazines can sometimes make me very

angry at what's going on in the industry and world.

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Since the only things in my home entertainment system that are more recent than 20 years ago are the TV and the Roku box, what's current is not much of an issue for me. I do wish that the current owners of the rights for Audio, High Fidelity and Stereo Review would make their archives available, though.

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Hi everyone I enjoyed reading the old stereo reviews as everyone else I still have my test cd from Stereophile . I personally think that Audio was much more credible in there reviews and practical,  Stereophile used to say one almost every other review that this was the next big thing, and I won't start with the snake oil products like 5000 dollar cables or interconnects I also have found a Web page that has all the old Audio magazine http://www.americanradiohistory.com/Audio-Magazine.htm

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Actually, Stereophile magazine is doing perhaps the best job of providing technically-accurate, precise, credible reviews of any source these days. While 30-40 years ago, it's true that Stereophile produced the nondescript pablum such as that valueless JG Holt A-25 "review," these days they provide extremely detailed and comprehensive measurements such as the ones I've attached here. Waterfall plots, impulse responses, anechoic FR in a 30-degree window at a 50" distance, individual driver traces with the port contribution separated out, etc.--this is first-rate reporting. Their measurements for amplifiers, DACs, etc are similarly detailed and comprehensive.

While the editorial comment is still full of idiotic terms like "liquid midrange," their quantitative documentation is as good or better than anyone's.

As far as whatever happened to aperiodic, I don't know. I think the KLH33 used a variant of it, and we were going to look into it for a wall-mounted subwoofer at AT, but the theoretical literature supporting it is "thin," to say the least. My gut feel--and I'm sure I'm right-- is that this was a really excellent idea by a Dynaco engineer as to how to refine the sealed principle a bit, but it was a 'seat of the pants' execution, not a nailed-down mathematical process.

Steve F

Stereophile 1.JPG

Stereophile 2.JPG

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When did they start including measurements? My recollection of TAS and Stereophile the last time I looked at either was that the editorial content, i.e., "listening impressions" were all that there was in the reviews.

It's all academic for me, though. I pretty much stopped reading audio reviews and buying brand new audio gear when Julian Hirsch retired.

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The quick answer is that Stereophile has been doing these kinds of measurements for at least 15-20 years. When I was at Boston Acoustics (1992-2003), we developed a 1-inch aluminum tweeter for our Lynnfield Series of high-end speakers (1992), and we used a version of that tweeter in our floorstanding VR speakers (1994). This tweeter had a plastic “bridge” over the dome that had a series of holes cut in it. We called it the AMD, or Amplitude Modification Device. These holes (which were actually of slightly varying length) acted as mechanical attenuators for the metal dome’s naturally-occurring resonance at around 25kHz. It’s not that 25kHz is audible or offensive to any human, but every metal dome doesn’t just experience that peak: there’s a corresponding 2-3dB “sway” in its output in the 10-20kHz region and that is audible. When the resonant peak was removed, the energy in the 10-20k octave increased.

 

I was putting together some literature for one of our speakers and I wanted to show this. I knew Stereophile published very detailed FR curves and I looked—sure enough, every single metal dome tweeter, regardless of the actual material and regardless of the company, show the ~25kHz peak (±) and the 10-20kHz trough.

 

I copied a competitive curve from a Stereophile test report (I didn’t mention the brand, of course) and I showed the BA tweeter curve with the AMD. Those are real curves, not made up! The AMD really worked. Anyway, that was a 1999 BA speaker, so Stereophile curves date from before then.

 

Steve F.

VRM50 p2.png

VRM50 p1.png

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On 4/17/2017 at 11:59 AM, onplane said:

In the review of the A-25, there are several mentions of AR products. I guess at the time of this review, AR was the standard against which everything was compared.

http://www.stereophile.com/content/dynaco-25-loudspeaker#KOozMceFiJCv3uCu.97

Anyone know whatever happened to the "aperiodic" design?

Today most speaker systems are ported, but there are a number of sealed bookshelf systems. Further, some of the best subs around are sealed boxes. I can't remember ever seeing a modern aperiodic system.

Regards,

Jerry

In the early 1970s, Consumer Reports tested the Dynaco A-25 along with several others of the period, such as the ADC 303AX, the AR-2ax, Scott S15 and the KLH Six, and the A-25 and 303AX  models were considered "Best Buys" because of their low price.  All of these speakers were "check-rated" and all considered "Acceptable—High Accuracy," and were at the top of all of the tested speakers.  However, the ADC 303AX, AR-2ax and KLH Six all surpassed the Dynaco A-25 in bass extension, even though the differences were small.  This test also mentioned the earlier 1966 test of the AR-4x and the small ADC 404, both considered equal to any of the top-rated speakers except for extreme bass; all you would be giving up in quality for what could be a significant savings at the time.

This was back in the period when CU tested loudspeaker in their anechoic chamber and in free-field tests, and they relied on these objective tests in conjunction with subjective listening tests (but they had not yet adopted the integrated-output tests to be used later in their rating methodology).

Gordon Holt at Stereophile was a quasi-scientific tester, but he did not perform exhaustive objective tests.  His comments in that article on the A-25 were strictly off the top of his head—his subjective rating.   The A-25 was surely a great little speaker, and it sold like hot cakes because of its low $79.95 price.  For its price, it was comparable to any speaker in that price range during that period.  

—Tom Tyson

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Back in those early seventies when I read in "Consumer-Reports' that they weren't completely as enthused about the AR-3a compared the the 2ax was when I stopped reading that publication for good.

And presently with the advent of the internet, I don't need that magazine any longer.

Additionally, with-in that time, my ears have grown wise.

FM.

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Notwithstanding the inaccuracies in the Stereophile review, I'm a bit nonplussed by the glowing descriptions of bass response from the Dynaco A-25.  While the review compares the A-25 favorably to the venerable "AR-5A", my own tests confirm that even budget AR-4x has superior bass response, forget about models higher up on the food chain. .  Here are my comments from a forum inquiry awhile back, where a forum member was curious about the AR-4x vs, the Dynaco A-25:

"I recently did just such a comparison (AR-4x vs. Dynaco A-25). I would characterize the Dynaco A-25 as having one of the most neutral and uncolored sounds of any speaker I've come across. By comparison, The AR-4x has a noticeable roughness in the midrange. However, in the lower bass region, it's a different story. While the A-25 lends absolutely no coloration to the bass it can reproduce, it does not have any usable output below about 50 Hz. The AR-4x however continues to respond well, albeit with reduced output, all the way down to around 30 Hz. In fact, I ran a 31.5 Hz test tone ( a sub-contra 'C') through both speakers. The Dynaco responded with upper harmonics and virtually no fundamental tone. The 4x's responded well enough to rattle glassware on a wall-mounted shelf about 10 ft. away from the speaker (I ran the same test with an AR-7 with similar results). So again, it depends on what's more important to you"

Those of you who have read my posts know of my oft mentioned "sub-contra C" test, which no AR speaker, even the 8" woofer models, has ever failed. 

That's why I love ARs!

Rich W

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Rich, that is a very interesting report on your measurements.

As I recall the A-25 has a 10 inch woofer vs an 8 inch in the AR-4x.

So what is going on here?

Do we get a "faster" bass roll off in the aperiodic design similar to the 24db per octave we see in vented systems?

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7 hours ago, onplane said:

Rich, that is a very interesting report on your measurements.

As I recall the A-25 has a 10 inch woofer vs an 8 inch in the AR-4x.

So what is going on here?

Do we get a "faster" bass roll off in the aperiodic design similar to the 24db per octave we see in vented systems?

Good question, and I have to admit this was a purely subjective test.  I never ran a frequency response curve on the A-25 in order to do a true "apples to apples"  comparison with my ARs.   But the roll off below 50hz must be much steeper than the typical acoustic suspension speaker.   While it is true that the A-25 is a 10" design, its magnet is smaller and lightweight when compared to AR 8" woofers.  Its excursion range is less as well.  Again, I'm not disparaging the A-25 - it is a fine speaker.  It just doesn't deliver quality low bass when compared to AR's even most modest models.  Also, "sins of omission" at frequency extremes are far preferable to a speaker which adds higher harmonics when it can't reproduce fundamental frequencies.

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If memory serves me correctly, the AR5 was not yet available at the time of the Holt article and I believe that the references to AR5/AR5a, etc., are transcription errors that did not appear in the original report.  I think he was actually referring to the AR2 & AR2a. I have the original Stereophile article somewhere (as well as the CR loudspeaker article mentioned by Tom) which I will try to find to help sort this out. 

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