jbl 2404 H network need help

[amicus]

Hello,

I would like to make little souuround speakers with jbl 2404 H and 18sound 6nd430 16 Ohm.

A lot of questions:

In calculationg software. Do I take Re or inpedanz in ohm at crossoverpoint?

If I take a look to network of jbl 4612b there is C1 2.5 uF, LPad 8 Ohm and L2 0.4 mH. Does the L Pad has an impedanz himself of 8 Ohm??

Every calculating software for crossover of 3 KHz does not give me 0.4 mH and 2.5 uF????

Need help for crossover.

Thanks

amicus.

[Robh3606]

In calculationg software. Do I take Re or inpedanz in ohm at crossoverpoint?

I use the average measured impeadence through the crossover point.

Every calculating software for crossover of 3 KHz does not give me 0.4 mH and 2.5 uF????

Measure a 2404 and model the response then it will make more sense. They should be around 10 Ohms if they fall in line with the rest of the ring radiators. If I get a chance I will measure one and post the graph.

Rob

[Robh3606]

Here's what one of my 2404's looks like.

Rob

[Robh3606]

Here's what LEAP comes up with. Not sure where the 3K comes in. Would have to measure the 2118's. It looks a bit higher than that.

Rob

[Baron030]

Hi Amicus

After, down loading the JBL 4612B technical manual and looking over its crossover network.
Well, maybe this will sound like an overly simplistic approach.
But, have you considered using most of the 4612b crossover’s component values?
I would suggest using the existing C1, R1, and L2 values for the 2404.
And then modify the L1 value to best suit your low frequency drivers.
If the L1 value is too large then there will be a hole in the response and if the L1 value is too small then a peak will occur.
It might be best to start will a L1 coil value that is slightly too large.
And then test the response and then remove a few winding from the L1 coil and then test again until you get a flat response.
The characteristics of the 2404 are pretty well known around here.
But, the “18sound 6nd430 16 Ohm” driver is a real unknown.
How does the “6nd430” driver compare to 2118J electrically and acoustically?
If might give some insight as to a L1 starting value.
And are you using 1 or 2 “6nd430” drivers in your project?

Since, Rob is playing around with his “LEAP” Crossover shop. You are certainly in good hands here.

Good luck with your project,
Baron030

[Robh3606]

Hello Baron

That actually a good starting point. The issues will be how sensitive the other driver is compared to a pair of 2118's and what the response is. That's a weird cabinet with only one of the 2118 rolled off. The other is fullrange??

Rob

[johnaec]

That's a weird cabinet with only one of the 2118 rolled off. The other is fullrange??

Yep, that's what they do. The 2118J is also 16 ohm. And in the Oak vinyl 4612OK version, the L-pad is left out - no HF adjustment on those...

He may also want to look at the crossover in the 4628B, where the 2404H-1 crosses over from a single 8 ohm 2118H. I don't remember offhand if the crossover frequencies are the same...

John

[ratitifb]

800Hz and 3000Hz for 4628B

[amicus]

Thank you all for your help.

I will need some days to translate, my english is not that good. (I hope you understand what i want to write ).

I made a copy of the data sheet of 18sound6nd430.

I will use for each cabinet
- one 18sound 6nd430 16 Ohm and
- one JBL 2404H
- in a 14 Liter vented cabinet, tuned to 60 Hz.

5 of those cabinets with an active contolled subwoofer of t+a should give a nice sourround system, I hope?

That's the projekt.

But first I need a network (without having equipment for measurment .

yours

amicus

[duaneage]

I would not cross that tweeter over any lower than 4500hz. If you do go down to 3000hz you would be advised to use a steep network, 18 or 24 db per octave so to prevent the driver from operating in it's resonant frequency. It is not a good idea to run a tweeter at or near the Fs (resonant frequency)

[amicus]

I just finished cabinets and a first network.

2,7 uF and 0,4 mH for jbl 2404h and 2,2 uF and 1,2 mH for 18sound 6nd 430. With an aktive sub it sounds quite nice, now work to optimize starts. When ready, i will post frequenze range plot.

Please give me help for crossover.

[jerv]

I just finished cabinets and a first network.

2,7 uF and 0,4 mH for jbl 2404h and 2,2 uF and 1,2 mH for 18sound 6nd 430. With an aktive sub it sounds quite nice, now work to optimize starts. When ready, i will post frequenze range plot.

Please give me help for crossover.

I have played a bit with the 18sound 6ND430 16 ohm. It's a little 6 inch driver. Sensitivity about 91 db/W (compared to the 2118J 95dB).

Here is my measured frequency and impedance curves on the 6ND430 in a 12 liter closed cabinet (I use them for midranges in my office system):

[jerv]

I just finished cabinets and a first network.

2,7 uF and 0,4 mH for jbl 2404h and 2,2 uF and 1,2 mH for 18sound 6nd 430. With an aktive sub it sounds quite nice, now work to optimize starts. When ready, i will post frequenze range plot.

Please give me help for crossover.

According to my simulations, you need to increase the capacitor a bit. 1,2 mH and 6 uF gives a nice, 4th-order rollof at about 4000 Hz. See curve with network as described:

(PS: I cannot help you with the 2404. I have no experience with that unit).

[amicus]

Hy,

tomorrow i will have time in studio to test network. I will send what I have got.

amicus

[martin_wu99]

I'm also thinking about this question of my 4628B.
Waiting for your studying.