604-8K or 604-8L in M600 Maestro?

[gearfreak]

I now have a pair of 604-?? in M600 Maestro units, questions at bottom.

My observations:
++++++++++++++++++++++++++++++++++++++++++
- Rear Label:
ALTEC LANSING THE MAESTRO SERIES
Loudspeaker System M600 8 Ohms
ALTEC LANSING CORP., OLKA. CITY, OK MADE IN U.S.A.

- No rear HF cover. I am not sure what to call the plastic housing otherwise, but it holds the diaphragm to the mag with 3 screws.

- HF Diaphragm marked with:
26420 (so we assume it's a 26420 pascolite)
32980
91 31

- Xover: MODEL N604-8A (stamped: 8167 ?)
- on woofer cones: 035400
- on woofer frame: Instead of the expected green (e.g.) "AL 70" in-a-square QA symbol, I see what appears to be: (green) "PI 15" in a circle.

- From a copy of an M600 spec sheet, it spec's :
R604-8L recone kit
16" coaxial loudspeaker 50-03-026768
N604-8A
++++++++++++++++++++++++++++++++++++++++++



...direct or tangentially related quotes from Altec forum posts RE 604-8L:
##########################################

01)
"The M-600 uses the 604-8L. It is a K with a higher LF power voice coil and uses the Pascolite Alluminum H.F. Diaphragm. That ought to be confusing enough fo now, Jim."

02)
"Incidentally, these improvements and T/S's are exclusive to the ICONIC Model 704-8A - the 604-8L off by ALPro is NOT the same speaker, nor does it share these characteristics (and it's more expensive)."

03)
Altec 604-8L
HF horn: 60h40v "Manta Ray"
X-over:
Power:
Impedance: 8 ohms
Weight:
Magnet: Ferrite Ceramic
Response:
Frame: cast frame dark grey paint
Cone: paper cone with an "accordian edge" cloth surround
comment: a K with a higher LF power voice coil
uses Pascolite Alluminum H.F. Diaphragm

04) from: http://www.altecpro.com/pdfs/vintage...%20Summary.pdf
"604-8K" (K)
N1500-8A (L)
LF = 12 dB/oct
HF = 18 dB/oct

604-8L = Same as K with new crossover network, hand-built for Altec Lansing Professional by Great Plains Audio, USA

05) "ALPro is (or already has) dropped the 604-8L from their product line. They have always been made by GPA in OKC, but they are different than the 604-8H-II he makes now."

06) The "L" was nothing but a late "K" with all of it's flaws and is no longer being made.
ALPro has dropped everything from it's line that is not made in China, including the 604.
The 604-8H-II is a redesign of the 604, taking it back to what it was, yet making it better in several ways.
##########################################




My questions are:

a) do I have a 604-8k, or a 604-8L ?

b) What are the flaws mentioned in (06) ?


thanks for any input!



*Small pics should be posted in a moment...

[GM]

The plastic rear cover is called a loading cap. It's used to reduce the rear cavity volume (Vb) causing it to be somewhat under-damped, so it can handle more power. Should be replaced with a standard felt lined cap for HIFI/HT apps for smoothest response: Altec Compression Driver Rear Loading Caps

No personal experience with them, though here it lists the 8K in M600 and in a later doc it states that the 8K, 8L are identical, so this implies that at some point they became the same except for the 8K's consumer cosmetics Vs the 8L's stripped for action 'look' as yours do: http://www.lansingheritage.org/image...ro/1993-35.JPG

GM

[whitebroncoii]

The information below was pulled off a document that I have updated a few times over the years;

604's Forever!
The first production 604 appeared in 1944 and quickly became the industry standard. The 604 is a "Duplex?" or coaxial loudspeaker utilizing a 15" woofer and a 1" throat HF compression driver (1.75" voice-coil). The HF magnet mounts directly to the back of the woofer magnet and the throat of the HF driver extends through the center of the woofer to a small horn. This basic configuration has remained unchanged for 50 years . . .

604 B,C,D,E
16 ohm, Alnico, Circumferential Phase Plug, Multicellular Horn, 15.2” rear-mount woofer frame, network = N-1000-B (B), N-1600-A (C, D, E), crossover frequency = 1000Hz (B), 1600Hz (C, D, E), 30W (B) and 35W (C, D, E)

604-8G
8 ohm, Alnico, Circumferential Phase Plug, Multicellular Horn, 16” front or rear mount woofer frame, network = “604-8G” with LF 12db/oct and HF 18dB/oct, crossover frequency = 1500Hz, 65W Pink Noise

604-8H
8 ohm, Alnico, Tangerine? Phase Plug, Mantaray? Horn, 16” front or rear mount woofer frame, network = “604-8H” with LF 12db/oct and HF 18dB/oct, crossover frequency = 1500Hz, 65W Pink Noise


604-8K, L
8 ohm, Ferrite, Tangerine? Phase Plug, Mantaray? Horn, 16” front or rear mount woofer frame, network = “604-8K” (K), N1500-8A (L) with LF 12db/oct and HF 18dB/oct, crossover frequency = 1500Hz, 75W Pink Noise


Notes:
604 B,C,D,E = Only small differences in construction. The B/C used a true multi-cell horn and the D/E used a sectoral-style horn with divider vanes.

604-8G = New crossover and diaphragm assembly improved power handling, delivered smoother mid-range, and exhibited lower distortion

604-8H = New Tangerine? phase plug and Mantaray? horn improved high frequency coverage. New crossover network offered HF and MF controls.

604-8K = New magnet offered same flux density as Alnico. Improved adhesives resulted in higher power handling.

604-8L = Same as K with new crossover network, Duplex? component hand-built for Altec Lansing Professional by Great Plains Audio, USA

[gearfreak]

Thanks GM and whitebroncoii


Ahh, so that's the loading cap. I didn't realize it'd be mechanically fastened to the magnet, figured it sat in the back of the cover instead.

I'll have to give GPA a call and see if and at what cost they will sell me a pair of covers w/felt.

[gearfreak]

Finally was able to scan the M600 spec-sheet (only 1 page) that I happen to have.
Created an HB 'album' which thus seems to offer some extra space for pics.
Had to split into top/bottom to meet pixel reqs. Severely cropped and slightly edited to make smaller.

Res is low on the posted copies, but perhaps you can zoom in and still glean something from it.

+++++

* Update: Scans removed. For some reason, they were replaced with someone else's pics of a makeshift XO on a kitchen table, and mine deleted... (during hostboard upgrade?). Oh well.

+++++


...came back to this post, and added the transcription, alas, the post app has removed all of my pretty aligned spacing. oh well, we will all live.

SPECIFICATIONS FOR THE M600 MAESTRO MONITOR LOUDSPEAKER SYSTEM

System Type: Two-way coaxial, vented, full range loudspeaker system.

Pressure Sensativity: 98.5 dB SPL (1W, 500 Hz - 3kHz,
re: 20?Pa, see Note 1)

Frequency Response: 60 Hz-20kHz (see Figure 1, Note 2)
Power Handling: 150 Watts, 60hz - 20 kHz, AES method
(see Note 3)

Maximum Long-Term Output: 119.8 dB SPL (150 watts input, 1m,
re: 20?Pa, see Note 4)

Impedance: 8.5 ohms minimum, maximum inductive phase angle = 65? @ 8 Hz,
maximum capacitive phase angle =
68? @ 78Hz, (see Figures 3 and 4,
Note 5)

Distribution Pattern: 60? horizontally by 40? vertically
(See Figure 8)

Components: 16" coaxial loudspeaker, part number
50-03-026768.

Crossover Network: Part Number N604-8A, at 1.5kHz, with
choice of high frequency attenuation.

Enclosure: Vented type for optimum response
built of 3/4" (1.9 cm) black stained
birch plywood, lined with glass wool,
includes 5/16" tee-nut mounting points
on each side and a removable grille.

Input Connection: Red and black five-way binding posts.

Replacement H.F.
Diaphragm: Model 26420

Replacement L.F.
Recone Kit: Model R604-8L

Replacement Grille: RG-M600

Dimensions: 26" (66.0 cm) high
22" (55.9 cm) wide
17" (43.2 cm) deep

Net Weight: 67 lbs. (30.5 kg)

Shipping Weight: 81 lbs (36.8 kg)

Finish: Black stained birch veneer, black
grille cloth.

[Panomaniac]

Gearfreak - thanks for posting the scams. Great info.

My buddy John, who lent me the 604-8Ks I have now, says that there where some early versions that used EV magnets and are not very good. EV was forcing Altec to use what they had in the way of ferrite magnets. A little later Altec went back to using their own magnets which were much better. That's what I have.

At this point that is just rumor, but someone here might know more about it.

[gearfreak]

My pleasure, hopefully they are a help to us or someone down the road.

Yes, I recall some mention of the magnet issue, somewhere.
I suspect that is what might be alluded to by the statement (copied from first post here) ...

_______________________________
<snip>
06) The "L" was nothing but a late "K" with all of it's flaws and is no longer being made.
<snip>
##########################################
My questions are:
<snip>
b) What are the flaws mentioned in (06) ?
_______________________________

...I'll have to re-research it and see what comes up.

[whitebroncoii]

Gearfreak - thanks for posting the scams. Great info.

My buddy John, who lent me the 604-8Ks I have now, says that there where some early versions that used EV magnets and are not very good. EV was forcing Altec to use what they had in the way of ferrite magnets. A little later Altec went back to using their own magnets which were much better. That's what I have.

At this point that is just rumor, but someone here might know more about it.

I worked at the Altec plant in OKC from 1983 through 1995. Magnets are ordered from vendors by documented specifications. Purchasing sends the specs to the vendor, a sample is made, the sample is tested and approved. Purchasing places an order for needed quantities. Altec and EV buy magnets to make speakers. It is entirely possible that Altec and EV bought magnets from the same vendor. This does not make the magnet an EV part. Since the Altec and EV magnets are very different, I do not believe EV magnet parts were ever used in true Altec speakers.

[GM]

Don't remember where I got this or who wrote it, though I assume it was Jim Dickinson since it's with some other postings of his.

GM
==========
"Not all 604Ks are the same either. Early versions had cast iron magnetic returns. They had problems getting the HF passage through the LF pole piece plated and some "grew" rust growths that look like bugs in this area. Later Oklahoma built ones used steel parts which cured the problem. Toward the end of 604K production, EV managers mandated the 604 use a larger EV magnet, this overdamped the LF performance.
The first 604L was made by Oklahoma for their slant front stage monitor (can't remember the #)and the M600 Monitor. This was a late 604K motor with with high temperature-regular length LF coil and standand K cone and Pascolite HF diaphragm.
When ALTEC Pro had GPA build their 604s, they also used the L designation. It was essentially a late 604K, complete with the overdamped LF section.
Later, we at Iconic, working with GPA, got the top plate thickend and restored the proper LF performance. These units, our 704, the last of the ALpro 604Ls and GPA's unit are best sounding and most linear of any of these speakers ever made, period... All three of these speakers differ in their soft parts, naturally we think ours has the best combination."

[whitebroncoii]

Don't remember where I got this or who wrote it, though I assume it was Jim Dickinson since it's with some other postings of his.

GM
==========
"Not all 604Ks are the same either. Early versions had cast iron magnetic returns. They had problems getting the HF passage through the LF pole piece plated and some "grew" rust growths that look like bugs in this area. Later Oklahoma built ones used steel parts which cured the problem. Toward the end of 604K production, EV managers mandated the 604 use a larger EV magnet, this overdamped the LF performance.
The first 604L was made by Oklahoma for their slant front stage monitor (can't remember the #)and the M600 Monitor. This was a late 604K motor with with high temperature-regular length LF coil and standand K cone and Pascolite HF diaphragm.
When ALTEC Pro had GPA build their 604s, they also used the L designation. It was essentially a late 604K, complete with the overdamped LF section.
Later, we at Iconic, working with GPA, got the top plate thickend and restored the proper LF performance. These units, our 704, the last of the ALpro 604Ls and GPA's unit are best sounding and most linear of any of these speakers ever made, period... All three of these speakers differ in their soft parts, naturally we think ours has the best combination."

Jim is a good guy, but, I think he is probably trying to sell his 704. The 938-8A floor monitor and the M600 were speaker systems that did not use a standard 604. They used a high-power version that was needed for the target applications (stage monitor and FOH). The 938-8A floor monitor even used a 2kHz crossover. This crossover made the 938-8A a little harsh and edgy to cut through stage noise. By using a different LF voice-coil and a 909 HF these high-power models were rated at 150W AES versus 75W for the standard 604 . The recone kit was part number R604-8L (over ten years before Altec Pro introduced the 604-8L). The higher power woofer could have been over-damped, but, I think it was over-damped by Altec parts, not EV. I can tell horror stories about the Mark IV (EV) days. The 604 was not one of them . . .