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Interesting crossover. 12db/octave slope?
I have no idea, It's a series crossover I think. I don't really get how it works. They used the inductor to attenuate the HF. I was thinking of building a pair but I wouldn't be able to do the taps on the inductors. All I would be able to do is build an un-attenable one. I wonder if I could use another small inductor to imitate the original attenuation or if it wouldn't work because it has to be part of the LF inductor?
cradledorf,
Thanks for posting the N-1600-A. It's one of the few Altec duplex crossovers I never had the opportunity to open up and examine. It's a series crossover, as you suspected, using first-order filters and taps on the inductor for HF attenuation steps. You could recreate it with mutiple inductors, or substitute a continously variable resistor shelving control instead like the N-1500-A used later on with the 604E.
Jeff
Thanks Jeff, I used the sketch I made as I was dissecting it and the Altec 604E schematic you have on your site to put it all together. Hopefully it helps others because a N-1600-A schematic on the net is pretty much non existent. :) Since were on the subject, I understand the variable resistor on the "E" crossover (R2) but what purpose does the other resistor have (R1)? Considering the size I would be tempted to assume it's an attempt at a zobel?
- Here's a calculator ( from LHF ) that might help you build your own autotransformer ( though , I've never used it ).Quote:
Originally Posted by cradeldorf
- Ostensibly, your coils should be kept together so that they are working as a single, unified inductor / but the problem with that, is that Mutual Inductance of all the coils together gives a final inductance figure that is larger than the sums ( of the individual coils ) .
- ie; One can't simply add a .75mH coil onto a 2.25mH coil and expect the resulting coils inductance will be 3 mH ( assuming you stack the coils in their proper orientation & that they are wired in series the result will be larger than 3 mH ) .
http://www.hostboard.com/forums/hbmc...2012/12/27.jpg
- Running one example ( to find the winding ratio for the -6 db point ) is; power of 10(-6/20) = .5012
- Running another ( to find the winding ratio for the -3 db point ) is; power of 10(-3/20) = .708
:)
It's not a series crossover as far as I can see. Normal 2nd order low pass with variable L on the woofer, 1st order high pass (cap) on the tweeter. Unless I don't understand the drawing. Is the horn connected into the spiral switchy thing?
To me it seems to be a 2nd order (12db slope). The 16uf cap and the .92mh coil are doing double duty.
The 16uf cap is bypassing HF to the tweeter but also shunting HF from the woofer. Same is true of the
.92mh coil. It's shunting LF away from the tweeter and bypassing LF to the woofer.That's how it looks to me
anyway , but I'm sure the experts here will clarify!
cradledorf,Quote:
Originally Posted by cradeldorf
You're right about N-1600A references being hard to find on the net.
R1 & R2 on the N-1500A crossover provide a voltage divider to selectively shunt part of the HF energy going to the HF driver. This is a simple type of "tone control" that does not have constant impedance like an L pad attenuator, but is pretty close to the desired impedance when adjusted to the "normal" listening level. When adjusted, it varies from constant impedance a bit more. Simple but effective.
Jeff
Nice post, Cradeldorf! This is the kind of stuff I like to see. Disect these old pieces of engineering excellence and see what makes them tick. I think in many cases, there are some great things to be learned by studying how Altec did what they did.
It's nice to be able to provide something back to the group. Were all in this together. :)
This is my final crossover for the 604C's They sound as good as their gonna get I think.
http://www.flickr.com/photos/8281241...in/photostream
I've got to hear a 604 one of these days. If the HF is lacking you could try a 1uf-2uf bypass around your 3 ohm 10w resistor. And if that's not enough increase your 3ohm resistor to 6 ohms. It works for me with 811's/511's but may not apply to 604's , may be too much a different animal.
The High frequency wasn't lacking, it was more of a mid frequency honk/sharpness. At 5 am I had the cabs open and was adding carpet to the back side of the baffle, It cured what I was after, the sharpness disappeared. I used that thin black stuff that's on the walls. I also put it across the ports and replaced that saggy cloth that was on there. It is very porous and doesn't appear to have altered the ability of the port to do it's job.
They sound like this. This is before adding the carpet to the back side of the baffle.Quote:
Originally Posted by rontec
DSCN6256_WMV V9 | Flickr - Photo Sharing!
Listening to my speakers last night and I could swear I heard the HF dropping out on the right side. So I removed the cover and checked everything. Found that the lead in wire where it was connected to the loop for the phram screw was hanging on by 3 strands. That made them sound a little better. Also realized that without the loading caps, the screws I was using were steel where the original ones won't stick to a magnet. so I put the loading caps back in. They must be stainless or something. Not sure if that was affecting their operation but I feel better about it now.
I tossed together a pair of mock N-1600 crossovers. To be honest I didn't even want to put them in because I was happy with how they sounded. I was skeptical about them being able to sound better And was almost positive that I would be switching them right back out after 10 minutes. There still in!!! I can't believe they are better sounding but they are!!!. I wired in the attenuators and they are set at 1 ohm.
MockN1600 | Flickr - Photo Sharing!
I was watching a movie last night and it got to a boring part so I flipped over to the ole FM and was immediately thrust into a 3D sound like I had never heard before. The speakers truly disappeared!!! When I woke up this morning I flipped it on again because Jazz Brunch was playing and it was truly magical. I still can't believe that these crossovers are performing as good as they are. Movies sound a little better than with the old crossovers but for some reason it doesn't compare to the FM sound.
You can check it out if you'd like.
Mock N1600.wmv | Flickr - Photo Sharing!
Hello friends,
I would like to try N1600A crossover with my Altec 605b's Could someone please let me know the inductor values for -2 and -4 db steps, my calculations give me approx .58 and .36mH.
Regards,
Sandeep