Active Crossover/Biamp for 604 duplex?

[Steve M]

Thanks Don for your reply...... I was just glancing at the official Altec spec sheets for the 604-8g and 604-8k duplex loudspeaker system (AL-1889 and AL-2401).

A couple of points worthy of mention perhaps,

Re:604-8g

Frequency response: Uniform, 20 to 20,000 hz
Distribution Pattern: 90 degrees horizontal and 40 degrees vertical.

Re:604-8k,

Frequency response: 40 to 20,000 hz
Distribution Pattern: 60 degrees horizontal and 40 degrees vertical

The 604-8k utilized a different dividing network, Dual section,shelving control/dual band equalizer.

Is it true would you say that the 604-8k achieved a higher power rating and pressure sensitivity at the expense of a slightly rolled off bottom end?

Re:Urei Time Align official specs 10/86:

Model 813c

Frequency Response: 50 to 17.5 khz + or - 3db


Model 815c (Single coaxial with two low frequency drivers)

Frequency Response: 40 to 17.5 khz + or - 3db

I am the proud owner of a pair of 604-8g loudspeakers that I purchased new back around 1977. These feature the Tangerine phase plug.
I use them now in a domestic situation.

I also use the original dividing networks and have set the speakers up for a flat frequency response with pink noise.

Interestingly enough they are flat prior to adjustment at 16khz and they were up 2db at 2khz and 3 db at 4 khz. Of course those measurments do take into account the interaction of the loudspeakers with the room acoustics. After adjustment they are flat from 31.5 to 16khz

In conclusion I believe the 604-8g, utilising alnico magnets is nothing short of outstanding.
Perhaps one of Altec Lansing's finest hours.

[joyspring]

Hi Steve,

The Thiele-Small parameters of the 604-8G and 604-8K are fairly close; they both can be characterized by low Qts (~0.2), high compliance (~14ft^3) and low fs (~25-30hz).

The discrepancy between frequency response specs between the 604-8G and 604-8K can be explained by a lack of an important qualifier: +/- dB.

For comparison, the Altec tear sheet on my Altec 605A states the frequency response as a very optimistic `20 - 22,000 cps.' What's not stated is that the output is probably down > 20dB at those extremes ;-)

I'm somewhat surprised that your Altec 604-8Gs have Tangerine(tm) phase plugs as those in the my old UREI 813s have the standard annular slit unit.

I thought that the Alnico Altec 604-8H was the first Duplex to have the radial phase plug though my memory is definitely failing with age ;-)

Don, would it be possible to verify this?

BobR

[marcuswilson]

Don,

Yes the 'quote' thing looks like a 'software upgrade for the indefinite future'

Interesting with the 4350s. I had a new pair of 4435s and thought they were OK, but definitely had problems. The 2235s did not really make it to 1K (or 1.2K I can't remember) where the 2425 came in. The 1" driver was inadequate also, especially at high levels where it compressed and got harsh.
The 4350s were a revelation with the most effortless dynamic ability of any monitors I've used.
The plan was to get a pair of double 2245s under them, but I think I'll do the Altec 817 thing first.

By the way, does anyone know anything about a pair of Western Electric 1.4" comp drivers I have, called "594A Loud Speaking Telephone". They have a 24 volt field coil (I think) and nice short horns ending in an oval mouth with a huge lens assembly. I also have the 18" woofers TA4181A.
Would love to know some technical info on them.

M

[Don McR]

The 594A is one of the most sought after compression drivers made. I've seen a single unit go for $5000 on Ebay. It is a 2" throat driver, not 1.4". JBL pretty much copied it and converted the field coil to an Alnico PM to come up with the 375. Performance characterisitics are very similar to the 375.

[Don McR]

To BobR

The 604-8H of 1978 was the first Duplex I've seen that advertized the use of the Tangerine phase plug. It also introducted the Mantaray horn on the Duplex. However, it appears that Altec began installing Tangerine plugs on late run 604-8G's after 1976. I've come across three people that own such drivers. The original 604-8G of 1974 definitely used the older annular slot phase plug.

[marcuswilson]

Don,

Thanks for the info.
I've had ideas about getting the W.E.s cabineted and running, one wonders what all the fuss is about?
People go silly over old Tannoys, the older they are, the more they pay. Yet if you listen to them, the later ones sound much better!

Your comment on JBL copying the W.E., I'm amazed at how intertwined the history of the speaker development was in the US back then. I guess it was such a small industry at the time. We get gear from the UK as well and it is quite different to the US stuff, although some things show influences from the US.

Has anyone written any comprehensive history of the development of sound gear, especially speakers. Your site is excellent within it's scope, I was first shown it by the JBL service rep for the South Pacific, JBL reps I've met like it.

I went to the JBL factory and they were still using some machinery that Lansing made. They said that they were very careful at dismantling the wire coating machine when they moved it as no-one really knew much about it and they had nothing to replace it, I guess it was so reliable, nobody had to know it's intricacies. They still talk about Lansing with high regard, it's amazing how long his designs have remained at the top level of their field, most of the improvements have been in materials technology since his time.

It was interesting to see them winding voice coils by hand. One would think that machines could do it more consistently, but my observation of the many speakers I repair is that JBL make better coils than any other manufacturers and usually have smaller gaps, so require tighter tolerances. Hand making coils seems to be the best.

M

[Steve M]

Hello BobR,

Thank you for your post, I understand and agree with what you are saying re: frequency response of speakers.

It was only an observation on my behalf that the spec sheet for the Altec Lansing 604-8g utilises the word "Uniform" when stating frequency response.
Frequency Response: UNIFORM 20 to 20,000 hz

Re: The Tangerine Phase Plugs.

The Australian distributor at the time I purchased was "Rank Industries".

As I mentioned I purchased a pair new back in 1977/1978.

Shortly after purchase I detected a difference in the sound of the high frequency response of the two loudspeakers ....... Upon further physical investigation I discovered that one 604-8g had a Tangerine phase plug and the other the original annular slit phase plug. To cut a long story short I phoned Altec Lansing in Anaheim and explained my situation. They were most helpful. The Australian distributor promptly replaced the non-Tangerine model.

If yourself or Don are ever in Australia, please let me know. You would be most welcome to have a listen.

If I may say, this is a great site with some very dedicated people. Thank you

[Don McR]

Marcus

I agree that the logic of the retro craze eludes me. Regarding speakers, there has been so much greater understanding of the science of accoustics, and so much more accomplished with new materials, that I can't understand why some pay tens of thousands of dollars for 70 year old technology.

That being said, I am also amazed at how much the early pioneers in the speaker industry got right. In particular, Western Electric, and more specifically AT&T Labs, was responsible for inventing virtually all basic loudspeaker technology. Over a ten year period, they invented the compression driver, the dynamic cone speaker, the cross-over network, bass reflex enclosures, multicellular horns and even electrostatic speakers.

All of this was driven by the movie sound industry and most of the players were associated in some manner. Jensen was used by W.E. as their contractor to build their cone speaker designs. The principals behind Altec, JBL and Stephens Tru-Sonic all got their start on the Shearer Horn Project as an attempt to get around the monopoly held by W.E. The industry was small enough (and pretty much centered geographically in Southern California) so that most of the industry pioneers knew each other.

Even to this day, the pro speaker industry has an aspect of smallness to it. Even though it is a billion dollar industry, there are only a small number of influential engineers responsible for the bulk of research and design. They are all familiar with each other, and many have circulated through the major firms at one time or another.

Regarding a comprehensive loudspeaker history, none yet exists. However, there are a couple of promising starts. Check the links page on our site. There is a section devoted to general loudspeaker history sites.

Lansing Heritage Links



Regarding hand winding of coils at JBL, I'm afraid those days are over. The above picture was taken in October 2000 during our first tour of Northridge. That week, they were in the process of moving the pro loudspeaker manufacturing to a state-of-the-art production facility. It included computer automated coil winding. The station pictured would be shut down within a month.

The machine that is depicted in the above photo was designed by Jim Lansing. Our host, John Eargle, said that some of the people working this equipment were only two degrees removed from Jim Lansing. In other words, the staff that trained the current workers were personally trained by Jim Lansing.

[eibei]

With all due respect to the statement that WE designed the bass reflex cabint. If this is true did Jensen buy the patient from WE? My reference states that Jensen owned the rights to the bass reflex cabinet [which they have placed in public domain].

Lynn

[Don McR]

Here's W.E.'s patent. I don't know what relationship W.E. had with Jensen regarding this patent.