Thinking 604B, 604D, & etc.

[selmerdave]

Bruce,

Same problem where B has a different horn than the later 604's, and as far as I know it's not possible to make a horn "conversion".

Dave

[Jim D]

OK, the early 604s, all those with the paper hinge cone,604, 604B, 604C and earlier Ds have the same woofer magnetic top plate as the original 515. It is chamfered and the usable magnetic gap is not as deep as the later alnico 604s-later D, E, G, and H which have the deeper 515B top plate. The early voice coils were almost the same length as the gap and the speaker is very overdamped. It works great in the mids, but any lengthy excursion will immediately take it out of linearity, works great for low power amps. The later units with the accoridion hinge cone have a the longer gap and a shorter voice coil for increased linearity. The early speakers are probably a bit more efficient than the later ones, they all have the same size alnico magnet. The G and H are some better as their cast pot is more magnetically efficient. The best result of a recone of the older units would be to use the later cone and voice coil. The result will not be the same as a complete later unit, probably a bit more efficient, more overdamped, but will have more linearity than the early cone assembly and will produce some more bass with the increased compliance. So you cannot make a C, D, or E into a G. Later Ds and Es will be close. There are very few B horns around, I do believe that they will fit the later alnico units. B horns were fragile and broke, so that compounds the problem. A B model with later parts is a great unit, especially in 8 ohms. Someday we will make a good retrofit horn for the C, D, E, and G models, but only after we finish a few of our other projects first. JIM

[BACarr]

Excellent information, thanks very much.

Since the 604's will also be used in the home theater situation, I was figuring to use a sub anyway, something like the Sunfire True, crossing over at between 70hz and 100hz.

Do you think 70hz would be too low to start running the 604B (assuming I can find another one)?

If I find another 604D before that, how can I tell the early from the late? The B has serial number 223 marked right on it, but the D only has markings on the cone (500438, with S14 in a circle below it, then 20750 on the other side).

Thanks again; I can see I'm getting closer.

[BACarr]

Well, son of a gun.

After reading what you've said, digesting and mulling a bit, I took the initiative and bid on the 604D at that online auction in Indianapolis ... and DID just barely win it. They'll keep the cabinet.

So, suddenly I have two D's and one B, and things are looking to be a lot easier. Assuming the D's are the same early/late era.

I'll still need some hand-holding in regards to crossovers, though, once they're all properly reconed and serviced.

[Jim D]

It's odd people are finding D's. The D was never a catalog item, officially the 605 had replaced the 604. There however, remained a demand for the 604 and the factory built custom 604D's for studios and the like. From what I have seen, the early D was merely a 604C with n N1600 xover
from the 605. I have seen later original D's with the 416-515B-604E cone in them and was once told by a long departed ALTEC person that the later D was very simlar to the E but painted green like the C. If the speaker has the paper hinge cone, you have an early D. If it has the accordian hinge cone, you--may-- have a later one. Look for the original ALTEC cone number and the older real goopy hinge dope. In reality, the only way to tell if it is a later D is to take out the cone and see which bass top plate it has , as it may have been reconed somewhere along the way by either a proper reconer or ALTEC. Either way it's still agreat speaker. The problem is which way to rebuild them if they need it, and probably only one of them does need it. More fun and games. JIM

[Jim D]

It's odd people are finding D's. The D was never a catalog item, officially the 605 had replaced the 604. There however, remained a demand for the 604 and the factory built custom 604D's for studios and the like. From what I have seen, the early D was merely a 604C with n N1600 xover
from the 605. I have seen later original D's with the 416-515B-604E cone in them and was once told by a long departed ALTEC person that the later D was very simlar to the E but painted green like the C. If the speaker has the paper hinge cone, you have an early D. If it has the accordian hinge cone, you--may-- have a later one. Look for the original ALTEC cone number and the older real goopy hinge dope. In reality, the only way to tell if it is a later D is to take out the cone and see which bass top plate it has , as it may have been reconed somewhere along the way by either a proper reconer or ALTEC. Either way it's still agreat speaker. The problem is which way to rebuild them if they need it, and probably only one of them does need it. More fun and games. JIM

[Jim D]

It's odd people are finding D's. The D was never a catalog item, officially the 605 had replaced the 604. There however, remained a demand for the 604 and the factory built custom 604D's for studios and the like. From what I have seen, the early D was merely a 604C with n N1600 xover
from the 605. I have seen later original D's with the 416-515B-604E cone in them and was once told by a long departed ALTEC person that the later D was very simlar to the E but painted green like the C. If the speaker has the paper hinge cone, you have an early D. If it has the accordian hinge cone, you--may-- have a later one. Look for the original ALTEC cone number and the older real goopy hinge dope. In reality, the only way to tell if it is a later D is to take out the cone and see which bass top plate it has , as it may have been reconed somewhere along the way by either a proper reconer or ALTEC. Either way it's still agreat speaker. The problem is which way to rebuild them if they need it, and probably only one of them does need it. More fun and games. JIM

[BACarr]

I'll have to see what arrives. Let's hope it's a match to my other D. If not, I'll have three mismatched 604's.

As if to make things more interesting, I came across what I think is a very late 604 in a speaker cabinet I forgot I built many years ago (I know, it's hard to "lose" a giant cabinet like that but my excuse is it was in the attic and it's a big house).

In the end, I might be the only person on the planet with four mismatched 604's.

[BACarr]

Update...
Well, the 604D finally arrived from the auctioneer and luckily it's a match for my other D ... the serial numbers put them within 50 units of each other (mine came from a radio station and the other came from a mono audiophile). Both are "late" model units, supposedly close to 604E specs ... we'll see how they tune once they're in enclosures and equipped with modern crossovers.
It looks like I'll be building the 604B into a center channel unit (in a smaller box - blaspheme! - and probably use an active crossover to keep it out of the low frequencies).
Then the D's as left and right and also for stereo music listening.
Still to be decided is what to use for rear speakers, as the 604's are so darned efficient.
I have a couple of Polks supposedly good for that application, so we'll start there.
This is a project (series of projects, really, if you include scrounging more matching McIntosh tube amps and electronics) that will take some time to play out, but I'll post links to pictures as it gets a head of steam this summer.

[Steve Burger]

Hah! 604b center channel! I got you thinking with my early post, didn't I.