View Full Version : Modeling networks

jim henderson

10-22-2003, 04:54 PM

I’m trying to model the 4344 MKII network’s MF section so I can see the effects of any component changes. I took the forum’s advice and got a student/demo copy of PSpice and entered the network schematic and the 2123H’s equivalent circuit. (I couldn’t find an L-Pad in the component library so I used two 8-ohm resistors and set the top one to 0.1 and the bottom one to 0.9 to get 90% full scale.) Does this look right?

jim henderson

10-22-2003, 04:55 PM

Here's the graph:

jim henderson

10-22-2003, 04:57 PM

Now I’d like to model the HF section of the 4430/4435 network. There are generally few T/S parameters published for compression driver/horn pairs. The 2426 spec only has Re and BI. What do I use for an equivalent circuit?

I’m not an Electronic Engineer, so I may be missing some fundamental concepts here.

Robh3606

10-22-2003, 06:04 PM

Hello Jim

Take a look at the Pi speaker site. Wayne Parham uses Aimspice. If you down load his Crossover Document I think he has what you are looking for. Basically what the motor breaks down into LRC.

Spice model:

! tweeter virtual circuit (JBL 2426)

! voice coil reactance

R4 6 10 3.3

L4 10 11 0.1mH

! mechanical reactance (on 2370)

C6 11 12 30uF

L6 11 12 3mH

R6 11 12 100

C7 12 13 15uF

L7 12 13 1.5mH

R7 12 13 100

C8 13 0 7.5uF

L8 13 0 0.75mH

R8 13 0 100

R9 11 0 20

C9 11 0 80uF

http://www.pispeakers.com/contents.html

This is out of context you should look at the whole document,

Where did you get the Pspice??

Rob:)

jim henderson

10-22-2003, 06:22 PM

Here's the one I used http://www.ee.mtu.edu/faculty/rzulinsk/pspice/80dlabe.exe

Here's another that I downloaded but haven't used yet http://www-ferp.ucsd.edu/najmabadi/CLASS/COMMON/PSPICE/91pspstu.exe

This looks like an alternate source http://www.cadencepcb.com/products/downloads/PSpicestudent/91pspstu.exe

Robh3606

10-22-2003, 06:33 PM

Thanks hope Waynes document helps you out.

Rob:)

4313B

10-22-2003, 06:46 PM

Originally posted by jim henderson

Now I’d like to model the HF section of the 4430/4435 network. What do I use for an equivalent circuit?

4313B

10-22-2003, 07:04 PM

More info on the 4430 & 4435 compression driver & horn combination (http://www.audioheritage.org/vbulletin/showthread.php?s=&action=showpost&postid=7400)

4313B

10-22-2003, 07:14 PM

Originally posted by jim henderson

I couldn’t find an L-Pad in the component library so I used two 8-ohm resistors and set the top one to 0.1 and the bottom one to 0.9 to get 90% full scale.For some reason that doesn't sound right, but I could be wrong. You might want to measure the poles of an actual L-Pad or just leave the L-Pad out of the circuit.

4313B

10-23-2003, 10:51 AM

Here is what I get measuring an L-Pad.

Earl K

10-23-2003, 12:25 PM

Hi Giskard

Great Info !

If you reduce that speaker load to 6.0 ohms , what do you get as a variation of resistance values as measured between pins 1 & 3 ?

( I do need to buy an 8 ohm Lpad sometime so I can answer these questions myself ).

Thanks <. Earl K :)

4313B

10-23-2003, 12:59 PM

Hello Earl,

Measuring a 6.2 ohm resistor yields a variance of 7.4 ohms with L-Pad closed to 6.2 ohms with L-Pad wide open. Maximum resistance occurs roughly between the 9 o'clock and 11 o'clock position where the resistance is 8.8 ohms. Setting the L-Pad right at 12 o'clock yields an 8.0 ohm load (3 to 1) with the "series" resistor portion of the L-Pad being 3.6 ohms (2 to 3) and the "parallel" resistor portion of the L-Pad being 17.0 ohms (2 to 1).

*****

For this particular L-Pad (JBL 58450) when series (3 to 2) is x then parallel (2 to 1) is y.

x =~ 1.0 ohms y =~ 29.2 ohms knob =~ 3 o'clock position

x =~ 2.0 ohms y =~ 24.2 ohms knob =~ 2 o'clock position

x =~ 3.0 ohms y =~ 20.0 ohms knob =~ 1 o'clock position

x =~ 4.0 ohms y =~ 14.6 ohms knob =~ 11 o'clock position

x =~ 5.0 ohms y =~ 9.4 ohms knob =~ 10 o'clock position

x =~ 6.0 ohms y =~ 4.8 ohms knob =~ 9 o'clock position

x =~ 7.0 ohms y =~ 0.2 ohms knob =~ 7 o'clock position

Anyway...

Earl K

10-23-2003, 01:11 PM

Thanks !!

- Good to know .

<> Earl K :)

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