Raising the While Flag on 604 Project

[vuki]

That's cool.

Vuki did you know that your HP filter (before the contour) has the topology of a 3rd order, but the electrical function of a 1st? You might double check me, but it looks like the filter functions is very near 1st order at 4KHz. A single 5uF cap would do the same. The inductor and resistor do pull it down a little faster. Did you do that by ear?

No, I didn't do it by ear. I did it through measuring and ear. You probably analyzed it with some simulation software which didn't tell the whole story. In reality there is significant difference between simple 1st order and this crossover. With 1st order there is no way to get crossover at 1600hz and no midrange hump (at aprox. 2-2,5khz). Anyway, as I said it measures and sounds pretty good.

[aeyb701]

The 604K's, almost without exception, have the wrong magnet on them - after EV bought Altec, they forced them to consolidate on some standard magnets EV was already using, and they made Altec use the DH-1A HF driver magnet, if memory serves, for the 604 and the 515.

Hi Todd:

In 2005 you said on this forum, "You see, during the years EV owned Altec Lansing (after the move to OKC), they forced Altec to standardize on a few magents, rather than the large number Altec was using. The early, Anaheim K's were actually quite good - almost as good as the "H"....but the change to a different magent hurt it a lot."

How do you tell an early vs late (Anaheim vs OKC) K? Serial number, but I recall no one kept a serial number list in all the reorganisation. I have K's and am quite satisfied with their overall balance, using K-xovers and Stonehenge encl's. S/N's are in the low 1000's.

-Jon Archibald

[Todd W. White]

I believe the serial number stickers tell the difference: Serial numbers beginning with a printed A are for OKC (believe it or not), and those beginning with a printed K are Anaheim.

Gary can correct me if my memory is wrong on this.

[Seadweller]

Wait !!! You've gone through six different crossovers? Hmm ! The gentleman from Chicago should have suggested L-pads for his second build. This would have given you some control of the slope and the balance (similar to the model 19 crossover).

There have been L-Pads in all the XO's he's built, but it's a struggle to control the horn energy without killing the highs...

Perhaps some experimentation with the range that the L-Pad covers would help?

[Seadweller]

Seadweller - have you tried removing the 3 ohm resistor on the bass circuit? Or replacing it with a different value one? I know the MLTL design for these drivers call for it, but if the bass is anaemic in your room, maybe this might help tune to your bright room?

David

Yep, I've tried it without, and have tried varying values...I actually even tried a baffle step circuit just to satisfy my own curiosity...

[Kercher]

I believe the serial number stickers tell the difference: Serial numbers beginning with a printed A are for OKC (believe it or not), and those beginning with a printed K are Anaheim.

Gary can correct me if my memory is wrong on this.

I've been wondering how to tell these apart too, but my 604-8k's don't have an A or a K on the serial number sticker, only 02191. Are there any other tell tale signs, like magnet sizes?

Dan

[Todd W. White]

The date code will also tell you - it will be something like 8234 - whcih means 1982, week 34.

If I remember right, Altec moved to OKC around 1984, so anything before that would be the original design, but beware - they had lots of QC problems then...

The other is the size of the magnet - it's huge.

[Kercher]

The date code will also tell you - it will be something like 8234 - whcih means 1982, week 34.

If I remember right, Altec moved to OKC around 1984, so anything before that would be the original design, but beware - they had lots of QC problems then...

The other is the size of the magnet - it's huge.

OK, both mine are labeled 239792. Is it possible that 8k's were made as early as 79?
Thanks,
Dan

[GM]

There have been L-Pads in all the XO's he's built, but it's a struggle to control the horn energy without killing the highs...

There should be a by-pass cap to let the extreme highs through unattenuated, but it sounds like either it's not there and/or not a high enough value and/or not wired to be inversely proportional to the L-pad's setting. Ditto for the mids L-pad.

Bottom line, I don't know if Altec built enough adjustment into these later designs and GPA has shown a penchant for maintaining the status quo, so not sure how any of these sound since my 'hand's on' experience is limited to the 604E, which at the time only required adding a bypass cap by ear around the single attenuator once it had been adjusted to balance the horn's lower BW to make it sound pretty @#$% smooth, tonally balanced all the way up as high as vinyl, RTR tape recordings went.

The more I've read about the later XOs though, the more I wonder if the extra adjustment causes more trouble than they're worth as just like adding drivers causes a ~exponential increase in design complexity, so it seems with two separate L-pads for only a two way speaker system, at least WRT the 604s.

GM

[Seadweller]

Thanks for the wonderful input everyone...So it looks like I have several options here:

1. Go with an active digital XO
2. Try the XO designed by Vuki
3. Experiment with caps and such

Any concensus which way to go?

By the way, how much of a difference does the port configuration make when it comes to bass response? Is diameter more important, or is length the key? Could a 6" port be too small for this cabinet?

Thanks!