D1050 Restoration Project Nearing the End

[glen]

BTW, does anyone know how to determine the polarity of the terminals on the cross-over I have pictured above? I don't see any "+" or "-" symbols for either input or output.

Thanks!

Howe

Hi Howe,

I just happen to have gotten an N1000 crossover of a similar vintage. I'll see if I can open it up later and post some pictures of it's innards.

Meanwhile looking at many pictures it seems like slightly later versions came with the output terminals numbered(from left to right) 1, 2, 3, 4 and the left input terminal labeled "B" (black, presumably ground) and the right input terminal labelled "R" (red). And from a later N1200 schematic with the three way hi-frequency level switch the inner pair of the top row of four (numbers 2 and 3) are shown strapped together and connected directly to one of the input terminals (labelled "5" in the schematic) which makes think that they are the ground terminals.

Here's a couple of pictures of a D-1004 speaker with similar wiring

and a later C34 that matches Harvey Gerst's description of standard factory wiring (although I think your speakers are a little earlier than his time at JBL):

factory wiring would have been black/green for the woofer, and black/red for the HF driver.

[Howe]

I have green and black wires from the D175 and yellow and black wires from the woofer pair so I'll assume from this that black is common and will be the center terminals or 2 & 3. Interesting that the woofers in the picture are 16 ohms. Wonder how hey are doing that impedance-wise. I've heard about a later model (C31?) that is a similar configuration but with the later potatoe masher 175 DLH.

Thanks Glen, I'll follow that configuration with the black wires at 2 & 3 (center 2 terminals) since its the best information I have at present. I can always reverse the polarity on the inputs from the outside if I have phase problems with the output (input) polarity. Nevertheless, I follow the convention you recognize. I hope to have these installed later tomorrow.

Best Regards,

Howe

[glen]

Interesting that the woofers in the picture are 16 ohms. Wonder how hey are doing that impedance-wise. I've heard about a later model (C31?) that is a similar configuration but with the later potatoe masher 175 DLH.
Howe

Hi Howe,

Sorry if I confused the issue. I just didn't have any good close ups of that D-1004 speaker (first two pics). The 16 ohm 130A is from a single woofer C-34 system (last 3 pics) with a 175 potato masher horn, just as you said.
The dual woofer systems like yours used two 32 ohm woofers.
I think Steve Schell has speculated about whether there was different resistance padding in the crossover for the high frequency when a crossover was built to be used with the single vs. double woofer systems. I've opened up my N1000 (will post pictures soon) and the HF is definitely padded down significantly.

[Howe]

Hi Howe,

Sorry if I confused the issue. I just didn't have any good close ups of that D-1004 speaker (first two pics). The 16 ohm 130A is from a single woofer C-34 system (last 3 pics) with a 175 potato masher horn, just as you said.
The dual woofer systems like yours used two 32 ohm woofers.
I think Steve Schell has speculated about whether there was different resistance padding in the crossover for the high frequency when a crossover was built to be used with the single vs. double woofer systems. I've opened up my N1000 (will post pictures soon) and the HF is definitely padded down significantly.

Glen,

Thanks for clearing that up. I do wonder at this point if there is padding on the N1200 that comes with the later system. Serial numbers match up so it could be but then again, I do wonder. Sweeping both with a frequency generator I didn't see a noticable difference. but my phasing was reversed on the HF driver. I wouldn't think that would make a difference on high frequencies?

[glen]

Hi Howe,
I just happen to have gotten an N1000 crossover of a similar vintage. I'll see if I can open it up later and post some pictures of it's innards.

Posted the N1000 pics and info in a new thread:

http://audioheritage.org/vbulletin/s...ad.php?t=11949

Hope that can be useful to you.

[Howe]

Glen,

Nice job. I think this clears up the connection configuration. I'll assume the early N1200 follows the same. Would be nice to compare schematics though. I'm also assuming the R1-R3 resitors form a pad to the HF driver.
Is there a N1200 (early) schematic somewhere in the forum?

Thanks,

Howe

[Zilch]

http://www.jblproservice.com/pdf/Net...tics/N1200.pdf

[Howe]

http://www.jblproservice.com/pdf/Net...tics/N1200.pdf

That is an interesting schematic. I've never owned a N1200 with a selector switch for HF attenuation. I should assume the not so fully featured unit or a system with a selector placed elsewhere in the enclosure would default to the 0 dB scenario?

[Zilch]

That is an interesting schematic. I've never owned a N1200 with a selector switch for HF attenuation. I should assume the not so fully featured unit or a system with a selector placed elsewhere in the enclosure would default to the 0 dB scenario?

Unknown. Somebody'll have to dissect one, or we wait for Giskard to come back and tell us....

[Howe]

Posted the N1000 pics and info in a new thread:

http://audioheritage.org/vbulletin/s...ad.php?t=11949

Hope that can be useful to you.

Does anyone know approximately at which frquency the N1000 and the older N1200 (without selector switch) are supposed to cross over at? I'd like to verify my crossovers are working correctly using an audio generator. I could imagine some of those 50 year + capacitors aren't what they used to be. Glen, you know that. don't you?

[glen]

Does anyone know approximately at which frquency the N1000 and the older N1200 (without selector switch) are supposed to cross over at? I'd like to verify my crossovers are working correctly using an audio generator. I could imagine some of those 50 year + capacitors aren't what they used to be. Glen, you know that. don't you?

They are both supposed to crossover at 1200 cycles.
Both specified as 18db/octave

N1000 here:
http://www.lansingheritage.org/image...1950/page6.jpg

Early N1200 here:
http://www.lansingheritage.org/image...1951/page2.jpg

Both had the same case and shipping weight.
Was the name change just to be more desciptive of it's function?
Was the N1000 originally intended to crossover at 1000 cycles?

[Howe]

They are both supposed to crossover at 1200 cycles.
Both specified as 18db/octave

N1000 here:
http://www.lansingheritage.org/image...1950/page6.jpg

Early N1200 here:
http://www.lansingheritage.org/image...1951/page2.jpg

Both had the same case and shipping weight.
Was the name change just to be more desciptive of it's function?
Was the N1000 originally intended to crossover at 1000 cycles?

Glen,

Thanks for your help. I should have dug deeper. I'll give a critical test with my function generator. I've already done a casual sweep but I'm not convinced I'm getting that kind of performance. 18 dB / octave is a steep slope. But, it is a 3rd order filter. The individual drivers tested separately are in very good health, however.