Testing Altec 604-C and 1600-A crossover with no test gear

[Squarewave]

Hi,

I'm trying to figure out if this driver is working properly, but I have no experience with this model, and so, nothing to compare it to. All I have is a meter, my ears and eyes.

HF=7.7 LF=8.1 ohms. Date stamp is Sept.of 56. Physically this looks like new, except for a 3/16" hole punched in the treated paper surround, no doubt from a failed mounting attempt.


I have run it with both a 100 watt amp, and a 20 watt amp. I was very careful with the 100 watt, because I know it is likely more power than this speaker is rated for

It seems to sound really great when run flat at low and medium volumes, but "bottoms out" or rubs at high volumes, and sometimes med high volumes with low end kicked up, (for a split second) on peak bass notes. Again, I really don't know how much to expect from this driver,and thinking it's not fair to compare it with Pro PA drivers that I do know better.

Any info or opinions from more experienced people would be great!

Cheers.
Dan

[Progneta]

Oh yes, I know exactly what you are talking about. I have had a dozen 604c's. A very common problem which I discovered with a few of them is that the tube that the woofer voicecoil was rolled on, was actually a hair to long for the cylinder upon which it moved up and down in. You could actually see where the voice coil former had been banging the bottom of the speaker (it had a small dent)

I find this problem only to exist in 604C original cones/kit. After they are reconed with a GPA kit, the problem goes away.

Its funny, but it annoyed the heck out of me. If you have a program such as "Room Wizard EQ", free download from hometheatershack.com, at medium volume run 30-50 hz tone through the speaker and you will hear the former literally bottom out, almost like a knock.

I have seen this problem so far on three 604c's. As good as altec was in the 50s, funny this got goofed up. If it really bothers you, you could recone, however GPA doesnt have the ribbed cone like the original altec 604 had, but instead the later accordion surround which I reconned one and it sounds fantastic.

-G

[Squarewave]

Progneta,

I thank you for your reply. I listed the driver today on e-pay. I described it there as I did here, and will leave it to the new owner as to what to do with it (if anything).

I tracked another 604-c on e-bay recently, and I do believe that they described the same kind of performance, or at least something like it. I also seem to recall that their driver was manufactured in Sept of 1956, as this one was.

If what you described is the trouble here, than I have to wonder if some voice coil tubes may have been cut too long in September of 56?

This also begs the question: Were these not tested before leaving the factory?

These seem to fetch decent prices online, as long as the owners don't get too proud.

If it sells, the money will go to keeping a roof over the rest of my gear!

Again, thank you very much
Dan

[Lee in Montreal]

Hi Dan

I don't have a specific answer for you, but perhaps just a clue. You mention using a 100w amp. What was the average amplifier rating back in 1957? 20W, 50W maybe. With 80 W you could even set-up a PA. Therefore, my take on the subject is that you are maybe asking too much from a 54 years old driver... Not to mention that the dynamic from a 1955 record has nothing to do with contemporary recording and reproduction systems.

[Robh3606]

Hello Dan

604C's have underhung coils. Their X-Max, excursion range, is about the width of the top-plate which isn't much. You really should run them with subs and high pass filtered with modern music at any real spl level. They are on the excursion limited side compared to a more modern driver. What kind of cabinets are they in??

Rob:)

[Squarewave]

Hi there Rob,

Thank you for the info.
I have only one 604. It came in a huge front loaded Hartsfield sized corner enclosure that looks as though it was either built in a cabinet shop, or by a fairly skilled handyman. I don’t recognize the design. I have tried to add a picture to this post, waiting to see if it works.

Port is about 4x14 and not far from the driver so it washes a bit. Every time I see one of these big old cabinets, I imagine the original 50’s owner reproducing fog horns, or 1812 cannon shots to impress his friends at get-togethers. Exactly what I would have done had I been more than 1 year old in 56.

Cheers,
Dan


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