Altec 605A versus 605B

[bfish]

Quote from BobR;

"And then have a `normal' loudspeaker hobbyist/enthusiast (that is, not a vacuum tube / vintage freak living in a retro-dream-world of phonograph LPs, Scotch 111 analogue tape and mono optical soundtracks) accurately measure the 605s"

Another quote from BobR in a thread last summer;

"Anyhow, I will be purchasing a brand-new pair of 704-8As sometime this year; my father is retiring next summer (at 71) and I want to build a nice tri-amped system (704s + sub) for him so he can enjoy his 2000+ classical LPs, CDs and open-reel recordings of 1950s-60s FM broadcasts. A nice way to repay him for the Altec 605A he gave me as a child which introduced me to a lifetime interest and eventually a career in engineering and teaching audio."


Just curious, Bob, do you call your father a "freak" to his face, and lecture him with seemingly-never-ending empirical data, trying to convince him that his "retro-dream-world" source of pleasure is inferior garbage?

MY Dad would have considered such insolence as just cause for a trip to the woodshed........at any age.

[joyspring]

It is possible to get 90 dB signal to noise + or ? 1 dB 7 to 35K Hz with 30 ips 1? tape with no digital hf distortion.

<font size="2" face="Verdana, Helvetica, sans-serif">At great expense, both in monetary cost and LF frequency response. Somehow, using a 2400' roll of 1" tape for 15 minutes seems highly inefficient with much higher-performance, lower-cost options readily available...

90 dB signal-to-noise ratio is easily exceeded by inexpensive 16-bit audio interfaces, DAT and compact flash recorders. 24-bit (144 dB) exceeds the max EIN (-131 dB) of analogue electronics theoretically and does attain 105 dB+ S/N in practice.

Digital HF distortion?

44.1 khz sampling frequency yields an upper limit of 22.05 khz (Nyquist frequency, from the Nyquist-Shannon theorem in communication theory).

Modern oversampling and improved filters minimise the earlier transient anti-aliasing filter issues.

And 96 khz sampling rates (what seems to be the current standard in recording and film) keeps the Nyquist frequency and anti-aliasing filters far above human hearing and handily exceeds the bandwidth of 1" 30-ips analogue tape.

So compromised performance at higher cost? No compromise; the newer digital recording technology wins on both counts.

It is possible to get acceptable (undetectable) distortion without feedback using pp triode tubes.

<font size="2" face="Verdana, Helvetica, sans-serif">This is true but one can still attain lower harmonic distortion at lower cost and higher reliability with newer solid-state technology.

Yes, it is possible to make a modern overhung speaker with low distortion but I have yet to see one with the same efficiency as the older alnico drivers excepting perhaps the latest JBL big dogs at about 5 times the cost.

<font size="2" face="Verdana, Helvetica, sans-serif">Yes, the loudspeaker efficiency does exact an extremely high cost but in the 1950s/60s was unavoidable as amplifier power was extremely expensive and wide-bandwidth 200 W+ unavailable.

Now, the common wisdom is that wide-bandwidth low-distortion amplifier power is for all intents and purposes "free".

Anyhow, using the constraint of high-efficiency, I'll concede that your point does stand...

Additionally, most modern speakers still have higher distortion than the Altec drivers most of us use.

<font size="2" face="Verdana, Helvetica, sans-serif">Definitely false, particularly at a comparable price point to the Altecs (which, during their heyday, was comparable to contemporary mid/high-end, at least for the Altec models that concern us on this forum).

There are many loudspeakers -- even a few sub-US$2000 systems -- that have less than 2% THD at reasonable acoustic sound pressure above 100 hz. Some now boast less than 1% at 90 dB SPL, 2 metres. And closed-loop systems (i.e. - Velodyne) extend this performance down to 30 hz at realistically high average sound pressure levels.

Upon inspection, the THD vs. frequency plot of the 604-8K isn't so impressive really and is most likely representative of the 515 and 902 as well (I haven't found second- and third-harmonic vs. frequency plots on other Altec drivers).

...the modern ?advancements? have been aimed at convenience and cost as all conceivable performance goals were met decades ago.

<font size="2" face="Verdana, Helvetica, sans-serif">True for certain aspects of audio, particularly power amplification.

Within the last decade, 24-bit/96 khz digital audio now far surpasses the dynamic and bandwidth limits of human hearing.

But your assessment is definitely false for transducers and in the context of this thread, loudspeakers; these can undergo far more improvement to achieve more even wider-bandwidth power response and better system-room interface.

Is the new stuff easy, consistent and more affordable? Yes it is. Does it offer the absolute best possible performance at any cost?

<font size="2" face="Verdana, Helvetica, sans-serif">In nearly every point, the newer stuff DOES offer superior performance, often at far LOWER cost.

That's always been a primary goal in the fields of engineering and applied science.

BobR

PS - Speaking of distortion, here's something I dug out of a dusty old book on my shelf:

"Four-percent distortion of 20,000 Hz (which is the second harmonic of the 10,000-Hz fundamental) has no meaning to the listener's ear, since he cannot hear that high anyway. The highest frequency of interest, as far as distortion is concerned, is one-half the highest frequency one can hear."

Technically true though personally I still believe that lowering distortion near the limits of human hearing is a laudable goal and exhibits good design decisions.

What's interesting is the source:

<ul>[*]Badmaieff, Alexis and Davis, Don. How to Build SPEAKER ENCLOSURES. Howard W. Sams & Co., 1966. p. 120 (ISBN 0-672-20520-3)[/list]

Yes, two excellent Altec engineers, one of which is Todd's mate who moved on to form Syn-Aud-Con with his wife Carolyn.

Interesting, no?

[joyspring]

bfish:

Quote from BobR;

"I don't believe in `faith'; I believe in objective, empirical data."


Let us know in about 50 years how that's workin' out for ya'.

<font size="2" face="Verdana, Helvetica, sans-serif">I surmise that you're referring to whatever religious beliefs that I may or may not possess...

Well, I'll let you infer what you may from my observations:

<ul>[*]According to the Pew Global Attitudes surveys, the US populace is highly religious, comparable to third-world nations and diametrically opposed to other industrialised first-world nations[*]US K-12 students lag two or more years behind their counterparts in northern Europe and the Far East (and probably every other nation that has a public education system) in physical and biological sciences and particularly mathematics. They never achieve parity with their foreign counterparts.[*]US citizens have extremely poor quantitative and analytical skills (observe the national debt, unbelievable rates of personal indebtedness)[*]the US must import more foreign expertise (engineers, scientists) for a shrinking pool of R&D and engineering positions[*]`Intelligent design' in public education would not be in issue in any other industrialised nation, particularly in northern Europe or Japan[*]Hal Lindsey books are best-sellers in the US[*]With the authors' names undisclosed, US citizens would probably consider Jefferson, Madison and Franklin to be subversive, terrorist-loving Godless communists based upon their letters and correspondence. Talk radio hosts would tell them so.[/list]

Utterly depressing for a nation that purports to be a technological leader (well, in consumption rather than creation or comprehension of technology anyways).

BobR

[joyspring]

bfish:

Another quote from BobR in a thread last summer;

"Anyhow, I will be purchasing a brand-new pair of 704-8As sometime this year; my father is retiring next summer (at 71) and I want to build a nice tri-amped system (704s + sub) for him so he can enjoy his 2000+ classical LPs, CDs and open-reel recordings of 1950s-60s FM broadcasts. A nice way to repay him for the Altec 605A he gave me as a child which introduced me to a lifetime interest and eventually a career in engineering and teaching audio."


Just curious, Bob, do you call your father a "freak" to his face, and lecture him with seemingly-never-ending empirical data, trying to convince him that his "retro-dream-world" source of pleasure is inferior garbage?

<font size="2" face="Verdana, Helvetica, sans-serif">You don't know my father or my relationship with him.

From my statement, you believe that my father is an analogue-phile, I surmise from the fact that he owns LPs and analogue tape recordings and once owned now-overpriced and severely overrated analogue **** .

No bfish, I don't have to call my father a `freak' nor do I have to lecture him because he is not an analogue/vintage freak and he highly values empirical data.

You see, my father is a retired research chemist, statistician and classical musician who happens to prefer (through good quantitative analytical skills) newer digital technology and wishes that such technology existed in the 1950s/60s to more accurately capture those performances that he enjoys.

Like most sensible folk, he doesn't like LP surface noise and rumble competing with pianissimo string passages. He finds `ticks and pops' to be utterly annoying and never mistakes them for percussion. And he absolutely detests having to flip sides, mid-movement.

And no, he did not choose the Iconic 704s in any event; he chose a pair of NHT model 4s from a candidate pool that also included the B&W Nautilus 801s.

Mated to a Yamaha 100 W/channel receiver and Pioneer CD/DVD-A/SACD player, the NHTs provide 23 dB above the target sound pressure level at his desired listening position.

He is digitising his 550 favourite LPs to CD but is dispensing with doing the tapes as they obviously require baking in order to transfer (which he can't be bothered with). Oh well, yet another reason to archive (and re-archive) digitally...

BobR

[bfish]

And, Mr Rhyu, you don't know us.

[martyh45]

BobR,
The Nyquist theorem assumes an infinite number of samples in any time period. As I have pointed out in the past, this is quite impossible to attain in practice. In reality, the HF waveforms of 16 bit digital are visibly distorted when viewed on a scope. Past experience has taught me that I can hear distortion long before I can see it.

Analog tape may not be the best cost vs. Performance compromise but the best machines have virtually undetectable noise and flat frequency response beyond the limits of most home speakers or studio monitors for that matter.

Digital has its place, I.E. when too many generations of work are required to get the recording to the end user. Current recording practices have sucked the life out of music. Put five guys in one good room at the same time, use a few microphones, a good tube system, record it all on tape and master away. No silly digital fixes, no cut and paste, no fix it in the mix, then you have something worth talking about ??..and listening to.

Marty

[Steve Mac]

Befroe this thread was severly hijacked...and I have no idea why...being my first post here and all...I had received from great info here on my duplex speakers. So thanks for that! Also, in another thread there was a post to a web archive link to the old sound practices website and lo and behold I have found some literature finally on the 605B. It was a 1965 product sheet which clearly points out:
a: xo at 1600Hz versus 1500 for the 604e
b: power handling of both speakers at 35 watts.

Here's the pertinent pic and thanks all for helping!