N1209-8A SCHEMATIC NEEDED

[whitebroncoii]

Sent your schematic about 2 minutes ago . . .

[rondo3000]

I would like to build an audiophile quality replacement for the N1209-8A crossovers that are in my Altec 1234 systens. Please email a schematic to [email protected].

Thanks; I will post pictures of the new crossover when done.

Ron

[rondo3000]

Thanks Gary.

[Richard C.]

So which loudspeakers use the N1209 xover? I researched it a little and it seems like they are mostly used for pro audio or theater stuff. One person called it "general purpose". The added Zoebel network doesn't make it that general purpose to me.

I know it's a little more "traditional" than the Model 19 xover. I wonder if it's for 515's more than 416's?

Richard C.

<font color="#FFFFFF" size="1">[ October 25, 2008 11:05 AM: Message edited by: Richard C. ]</font>

[rondo3000]

My Altecs are Model 1234. Each has an 808A driving a 511 horn, and a 421 woofer. The 421 has an aluminum dustcover, like the JBL D130. It was used in guitar amps, and is an extended range speaker in the high end (to maybe 3 or 4 khz). The N1209 crossover has a 1200hz crossover point with 12 db/octave slopes. Like some of Atec's newer crossovers such as the N1201, it has equalization for the HF driver in the form of a parallel capacitor/resistor network. This EQ circuit causes a shallow dip in the middle of the HF range, resulting in extended highs, and less midrange Honk.

Ron

[bowtie427ss]

It's been a while so i'm a little foggy on this, but if your 1234's have N1209 XO's, they are not original/stock.

From what i can remember the 1209 is very similar to the 19 XO with the biggest difference being the 1/4 inch panel mounted input jacks.

My 1234 XO's are as described in the above post with a fixed RC for EQ on the horn, they also use a pair of air core, bobbin type inductors.

The N1209's i had were equipped with MF and HF pots/controls, and used three iron core inductors, and a more complex circuit very similar to the 19 XO.

Again, going from memory here so please don't shoot me if i'm wrong.

Also, FWIW, if i were looking to make "hifi" improvements to the 1234, i'd begin with internal bracing of the box and get aluminum phragms and felt damping in the 808's while losing the loading caps.

Just my .02........................

[rondo3000]

I bought my 1234's used, so I don't know what was the origianl crossover.

Thanks for your tweek suggestions. I have already greatly improved the sound by dampening the outsides of the 511 horn with window putty-rope, which can be purchased at any hardware store. Boy, those horns rang like a cow-bell (with sustain!) before dampening. I recommend this to everyone.

[Richard C.]

The N1209-8A is similar to the one used in the Model 19; it looks about the same from the outside.

Both schematics are available in the "Modell 19 Crossovers!" thread. The components are very different, and from what I was able to model, (in my "Multisim" simulation software), they are quite different. The Model 19 (N1201) has a broader hole in the midrange (electrical drive), than the N1209-8A. The 416 must have fantastic output from ~750 Hz to past 1200 Hz, because the electrical drive drops off like that of an 800 Hz xover! Simulating a crossover seems to be just a small part of what's going on.

One thing I've seen, and heard, is that electrical drive doesn't have much to do with actual sound output.

Richard C.

[rondo3000]

Richard C., the 1209-8A crossover has a zobel on the woofer, so it responds the the crossover as an 8 ohm load. The 1201 doen not have a zobel, so the impedence of the woofer is much higher at the crossover frequency, hence the need to much more inductance in the crossover than a true 8 ohm load would need.

[Richard C.]

Thanks Ron,
I never thought of it that way...

I need to be able to measure the response better, because I bet it would be much different if you added a Zoebel without changing any other parts!

I changed my Model 14 xovers to a more conventional 12 dB/octave for the woofer. (They are normally run full range) As soon as I added a ~1800 Hz low pass filter to the woofer, I got a terrible peak in the response, which was flattened with a Zoebel. I simulated it with Multisim (Electronics Workbench) and it told me the values to use once I measured Le at about the problem freq.

Richard C.