Altec crossover

[bluelobster]

I have a pair of 846u and would like to try some experimenting. Since I have nice cabinets and decent drivers, 806-8z HF, 811 horn and 411 or 413 8a woofer from the Santiago, I can't recall right now.
I would like to raise the crossover from 800hz to 1200hz as in the model 19.
Which crossover network would I need? I have a spare set of n501-8a that could be used as a test bed if need be.
I still have the original 416-8z woofers if needed to make things work.I just liked the bass response of the 411/413 better.

[Don McRitchie]

I'd be very surprised if the 411 would work with that high a cross-over. The 411 is a medium efficiency driver that has been optimized for LF extension with a much heavier cone than the 416 used in the Model 19. It required an attenuator to be used with the standard Altec cross-overs of the day so that the HF driver could be stepped down to match the lower efficiency 411.

[Earl K]

Hi bluelobster

- You can search eBay for the N1201-8a or N1209-8a crossovers.

- These both have 1200 hz points and were mostly used with the 416 type woofer.

- Look HERE to see a past sale of the N1201 type.

- Both of these crossover models have a "midrange" suppression circuit to help rebalance the midrange response to the top-end response. I'm guessing this is why you want to move your existing crossover point higher .

- If you get any of these crossovers, seriously consider upgrading the series inductor for the woofers, to a 14 ga "air-core" type. Also, I'd recommend "bypassing" the existing caps. Read "The Bypassing Thread" for an education on "Bypassing" capacitors .

- As Don stated, the 411s heavy cone mass may disappoint you in its reproduction of the extra 1/2 octave that you'll be adding to its' playback duties . If that becomes the case , then go back to the 803/416 woofer . Or, consider putting a JBL 2235H speaker in there . The 2235H speaker has a mid-weight cone but has extra "mass" added to it in the form of a circular aluminum ring glued to the VC former. This added mass ( like the heavy cone of the 411 ) is what gives this speaker the ability ( among other factors ) to generate convincing bass . This speaker ( 2235h ) offers a well engineered balance between VLF, LF and Midband response. It's sensitivity is about the same as the Altec 411 .

regards <. Earl K

[bluelobster]

Thanks Earl. I have another question now. I am familiar with what an inductor is but not your terminology. Could you better describe the 14ga inductor in series?

[Earl K]

Could you better describe the 14ga inductor in series?

- I guess I was being vague .

- I mean the inductor that's in the "lowpass" portion of the crossover .

If you buy , one of the 2 mentioned crossovers, then consider replacing the lowpass inductor with an aircore type made of 14 gauge wire . You can buy inductors of this nature from
Parts Express - AirCore up to a certain value. If you can't get an aircore mh value in your budget ( or it won't fit the crossover ), see if the Iron Cores made by "Erse" (at Parts Express ) can be made to work . I don't know which value you might need .

Here are pics of the two types of inductors .

regards <. Earl K

[Earl K]

Hi bluelobster,

Looks like I was wrong to assume there was just a single series inductor in the woofer circuit of the N1201-8a.

Here's the schematic , as laid out by Jim Easley, this was downloaded from Jeff Markwarts' Corner "Web-Page"

- As you can see, an upgrade to better inductors in the woofer circuit involves replacing 2 inductors. Jeff recommends better parts compared to my own articulations.

- Also, here's what the inside looks like of the N1201-8a crossover, with the "cowling" removed.

- Here's a picture of the insides of a N1209-8a that I own. The 25¢ piece is added for scale , along with a 16 or 18 gauge / 1.6mh coil . As you can see the inductors / coils / "chokes" are physically quite small inside the crossover . Retrofitting in better ( larger ) types will be a challenge .

- Here's a picture of the insides of one of the two types of cap found in these crossovers. You can see from the picture that its dielectric type is "Paper in Oil" . The other dielectric type "made by Callins" is still unknown ( since I haven't yet "sacrificed" a cap to find out ). When I opened this other cap (about 2 months ago ) there was already some "oxidation" to the most "oiley" portions. My point ??? most likely, all these 20 to 40 year old "paper in oil caps" should be replaced - unless a person can check them out and verify that there's no "capacitance drift". FWIW ; I've heard some pretty nasty "resonances" ( in the past ), particularly on female voices, when auditioning these ( aged ) surplus-type "PIO" caps.

regards <> Earl K