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Time to winnow down the speakers. Cornwalls? Valencias? 605A's?

Zilch said:
Link to the N1600(C) crossover schematic, please....
Click to expand...

http://www.audiokarma.org/forums/showthread.php?t=39472&highlight=altec+605a

Scroll to bottom. I made this as shown. I cracked the original N1600 open and found a 5uf where I would expect a 4uf, so the choke in my N1600 probably isn't 1mh.
No matter. I just wanted a pair of crossovers with good caps in them so I could listen to the pair of speakers together as some kind of baseline. I don't trust 45 year old wax box caps to match any more. It was easier to gin up new ones than reverse engineer & repair the old ones.

I just got back from butchering up the crossovers in a pair of mint K-horns, then adding a Sunfire subwoofer under the couch. Hey, it's not my money. I just do what I'm told. I have to say after hearing his Dyna ST-70 with the new driver board (Triodeel EF86) I put in it, it's a vast improvement over the cruddy stock board.

I'm gonna go build that second crossover now so I can have steeerio like the folks across the street....
 
Okay. I now have both 605As running with clones of N1600 crossovers. In these cabinets they roll off drastically below 70hz, so I've rigged a mono powered sub up to run below that. I just can't evaluate them properly unless they're full range. Sounds promising so far, but I'm just playing some Dub to get the bass balance in the ballpark. I'll leave these up for a few days to get a feel for them and in the meantime scare up something more suitable in teh way of bottom end enhancement (stereo, more controllable).
I sort of hope the 605's win out and get to stay. They're the *narrowest* of the options available. I'd probably still have the Model 19s except the things blocked too much of my view out the windows.
I already like the treble more than the Cornwalls, and if anything it seems a bit more extended than the Valencias (smaller horn?)
More info as things proceed.
 
Compare:

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The R across the inductor makes it a step filter, variable with the HF attenuation in N1500.

I believe Don's saying it should be there in N1600 as well, fixed at 12 Ohms, across 1.4 mH in lieu of the 1.0 mH shown.
 

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Zilch said:
Compare:

The R across the inductor makes it a step filter, variable with the HF attenuation in N1500.

I believe Don's saying it should be there in N1600 as well, fixed at 12 Ohms, across 1.4 mH in lieu of the 1.0 mH shown.
Click to expand...

Not quite following you. I built the upper one more or less as shown. I don't see 1.4mh in parallel with a fixed 12 Ohms in either one. I think you're one step ahead of me in your inference from the drawings presented.

Ultimately, I'd probably build something like the Markwart '1240' second order Butterworth, which I just priced out at $120 in parts for 2 channels. It has the mid freq EQ, which seems like something I'd use.

I'm listening to the last Morphine album right now and the sax sound is really nice. I need to spend a few more days with these.
 
Bauhausler said:
I sort of hope the 605's win out and get to stay. They're the *narrowest* of the options available. I'd probably still have the Model 19s except the things blocked too much of my view out the windows.
I already like the treble more than the Cornwalls, and if anything it seems a bit more extended than the Valencias (smaller horn?)
More info as things proceed.
Click to expand...
The response is shown in the last image of Don's link, rolled off above 10 kHz, similar to Valencia.

I'm not seeing forward midrange, tho; the N1600 seems to have knocked that down substantially more than N800-F does in the Vals, as shown in the next image up.

I can't read the scales, and I can't copy either to sharpen.

Perhaps Don could post them here, please? :yes:
 
Bauhausler said:
Not quite following you. I built the upper one more or less as shown. I don't see 1.4mh in parallel with a fixed 12 Ohms in either one. I think you're one step ahead of me in your inference from the drawings presented.
Click to expand...
R1 + R2 is in parallel with L1 in the N1500 comprising, at once, attenuation for the HF and a step filter for the LF.

C2 equivalent in N1600 isolates the parallel resistance(s) from the 1.0 mH inductor, and there's no longer a step filter function for the LF there. I believe Don is saying that should be there, and thus the 1.0 mH should be 1.4 mH with 12 Ohms in parallel.

Either we don't have an accurate N1600 schematic, or Don is recommending a mod.... :dunno:
 
Zilch said:
R1 + R2 is in parallel with L1 in the N1500 comprising, at once, attenuation for the HF and a step filter for the LF.

C2 equivalent in N1600 isolates the parallel resistance(s) from the 1.0 mH inductor, and there's no longer a step filter function for the LF there. I believe Don is saying that should be there, and thus the 1.0 mH should be 1.4 mH with 12 Ohms in parallel.

Either we don't have an accurate N1600 schematic, or Don is recommending a mod.... :dunno:
Click to expand...

Riiiiight. Now I gotcha. I thought you meant the other Don, so I went off chasing the wrong flock of wild geese.
I see what you mean about the step filter. Well, I wouldn't want to make a change at this time that gave me more mids out of the woofer. I'm going to listen to these as is for a while & form impressions about what changes I might make. This is in lieu of testing the response. I know that's the preferred method for development, but anything too big/heavy to be carried downstairs to the bench is probably only going to be ear-tested here.
I can make that inductor/resistor change easily later.
I think in the meantime I'm going to buy a bunch of 15ga magnet wire so I don't have to wait for boxes from Parts Excess when I want to change things. IIRC, there's a nifty online calculator for inductor dimensions somewhere.....

http://www.lalena.com/Audio/Calculator/Inductor/

Man! When did copper get so expensive??
 
I'd have to run the particular values in Spice to be certain, but I believe, while the resistor is going to defeat the major woofer rolloff from the inductor, with a higher inductance, it will lower the mids, actually, and allow more of whatever bass is there to be better balanced, assuming the woofer has a rising response as most of that genre do.

It further depends upon where the natural rolloff of the woofer occurs, how much the HF cap across it contributes to the lowpass, and at what frequency.

[Series crossovers are a trip to figure, folks; this is fun stuff for speakergeeks.... :yes: ]
 
The schematic for the N-1600-C has a 1 mH iron core coil.
If you use an air core coil it should be 1.4 mH with a 12 Ohm parallel resistor; to get the same freq resp curves. The schematic shown was drawn from my 605As bought new in 1963
Don
 
dlp4341 said:
The schematic for the N-1600-C has a 1 mH iron core coil.
If you use an air core coil it should be 1.4 mH with a 12 Ohm parallel resistor; to get the same freq resp curves. The schematic shown was drawn from my 605As bought new in 1963
Don
Click to expand...

The 'should be' in there is ambiguous, as it could mean 'the drawing is drawn wrong' or it could mean 'the response is better if you do it this way instead' or it could mean '1mh iron core and 1mh air core are not equivalent'.

Are you saying that in this circuit different results will be obtained when simply substituting a 1mh air core coil for the 1mh iron core, and that the correct equivalent when using an air core coil in place of the iron core is 1.4mh air core in parallel with 12 Ohms to replace the 1mh iron core?

Just trying to parse out what you mean.
 
Okay, I've got a proper fullrange stereo setup with the 605As running. I cloned the N1600 crossover as described above, subject to future fiddling or replacement. The speakers roll off acoustically around 80 hz in this cabinet/room. For bottom end I reassembled a pair of AR3 cabinets with their original woofers & no passive crossover, well sealed and heavily damped. I'm driving them with an active 18 db/oct xovr set at around 70 hz at the moment. The power amp is the mighty Accuphase P-300. The subs put out healthy output at 25hz, which is plenty low enough. There's a big suckout at 63 hz, so I have to fool with the phasing of the sub & crossover point, but it's 90% there.
The AR3 cabs have the advantage that when I set the 605A's cabs, which are 19" cubes, on top of them the height is just about perfect. But it looks stupid, so I won't be posting a pic of that maneuver.
I have to say that having a solid bottom end makes an enormous difference to this and nearly any other speaker. I'm not a bass freak, but if the bottom octaves are out of balance, it's impossible to judge the merits of the rest of the speaker.
I need to leave this arrangement alone & listen to music for about 5 days on it. I think it sounds quite different from the Valencias, but it's difficult to quantify because teh bass is so radically different. I'd like the 605A's to work out for 'packaging' reasons - smaller footprint as implemented.
While I was writing this an audiobuddy came over. He sold audio for 35 years at various Detroit high end audio salons. He listens to Lowthers in Hedlund cabinets (big tall back horns) as his primary system and builds all of his own electronics. He's a jazz fan so I put on Dave Brubeck's Gone With the Wind, which I wasn't aware I owned until I stumbled over it yesterday. The 605As really open up on this old analog recording. It's super nice and I think I'm going to like them a lot.
Next I need to try a bad recording of music that I like a lot, like The Shins or the New Pornographers to see if the 605As will kill me playing a bright, compressed modern recording. Got lotsa those and I have to be able to listen to them.
 
Bauhausler said:
The 'should be' in there is ambiguous, as it could mean 'the drawing is drawn wrong' or it could mean 'the response is better if you do it this way instead' or it could mean '1mh iron core and 1mh air core are not equivalent'.

Are you saying that in this circuit different results will be obtained when simply substituting a 1mh air core coil for the 1mh iron core, and that the correct equivalent when using an air core coil in place of the iron core is 1.4mh air core in parallel with 12 Ohms to replace the 1mh iron core?
Click to expand...
From the Altec Forum:

donaldpatten said:
FYI I tried to copy an N1600 XOV for a 605A with an air core coil. I did not get the same freq resp or sound. Then I changed the coil in the factory N1600 from stock ( iron core )to air core , and got the same result as the copy XOV . So the iron core coil is key.I went on to find if I added a resistor ( 15 ohm 10 watt )across the air coil I could duplicate the iron core coil resp & sound. With out the resistor, both LF & HF resp are are way off. With the resistor & air coil the resp was right on. I tried both # 15 & 18 awg coils with the same result.
Click to expand...

I put the several alternative designs into Spice last night, and then read 26 threads over on the Altec Forum, where it was originally alleged that the difference between the air and iron core response is associated with placing an air core in proximity to a steel enclosure. How it morphed from 1.0 mH to 1.4 mH is indeterminate.

Bottom line: Unless you have the original factory schematic AND an actual sample of the stock crossover (multiples, preferably,) for verification, it's a crap shoot.

I'll post the Spice results, if you like. It's NOT pretty. :no:

[I believe 1.4 mH is correct, BTW, but there are other problems.... :banghead: ]
 
Bauhausler said:
I have to say that having a solid bottom end makes an enormous difference to this and nearly any other speaker. I'm not a bass freak, but if the bottom octaves are out of balance, it's impossible to judge the merits of the rest of the speaker.
Click to expand...
That's been my experience with the single-driver, fullrange speakers I've listened to. Thanks for writing up your experiment - this is fun!
 
Billfort said:
May be a fun challenge to do your own thing and it might work out well but based on my experience with 604s, I'd proceed directly to these pages and build what's detailed there for the 605.

http://home.earthlink.net/~jmarkwart/index.html
Click to expand...

All roads lead to Markwart, apparently. I haven't settled the crossover issue yet. I built the N1600 clones to have a pair of identical crossovers of some sort as a baseline for evaluating the speakers more or less as they were originally intended. After I decide whether to keep the Vals or the 605As I'll get into the business of improving networks.
 
Billfort said:
May be a fun challenge to do your own thing and it might work out well but based on my experience with 604s, I'd proceed directly to these pages and build what's detailed there for the 605.

http://home.earthlink.net/~jmarkwart/index.html
Click to expand...
That's easily modeled, as well, which I just did, and there's no compensation in it as there is in the earlier Altec series topology crossovers.

Altec knew what was up with how their product sounded, and, examined in detail, their crossover designs reveal what they did to optimize them. Seems like everybody's willing to throw that part away.

The Markwart design may incorporate time alignment, but it does not mitigate 806A's forward midrange response.
 
Zilch;
Thanks for the clarification of the air/iron issue. Thinking this through, if an air core was installed in the original N1600 steel box, the inductance would increase in an unpredictable way. I don't know why anyone would do that on purpose. I have 2 original N1600 here, but I don't know how easy it would be to test the L and DCR of the choke nondestructively. I suppose I could take one of the originals, one of my clones, load both with R's on the outputs and watch the 'scope while I manually sweep them with a sine wave. This is where the scope's invert/add function comes in handy because you can see only the difference between the two signals if you want to. It's a crude but simple method. Not very revealing, though. I doubt the 45 year old N1600s have their caps still at the original values.
At this point having got them running with equivalent crossovers & subs I need to stop changing things for a while & listen to them. It'll take a few days of listening to lots of music for any deficiencies to become evident. As it is, the balance is very good. There's no glaring problem or I'd be going after fixing it before settling down for long term listening. The N1600 clones seem to be doing a good enough job for now.
 
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