4345 4355 networks

[4313B]

Greg often used 1.0 mH and 3.5 mH air core inductors having 7.5 ohms DCR across midrange and high frequency transducers back in the 70's and 80's to mitigate their resonance frequencies. Note L3 and L4 below in the L212 parts list. These exact same L212 parts are shown above in my L-Pad board photo. Way back in the early 80's I purchased a bunch of each from JBL Parts.

It turns out that he also used them in the 4344 Mk II many years later sans the high DCR values, at that time he used resistors in series. L3 and L6 in the schematic.

[Odd]

7,5 ohm DCR on a coil would be quite unusual...wasn't it combined with a resistor placed in series?

Yes, read here and here.


Edit. Didn't see the post above before I posted.

[Hans Bleeker]

NVM, I should look at previous posts first

[Dr.db]

Greg often used 1.0 mH and 3.5 mH air core inductors having 7.5 ohms DCR across midrange and high frequency transducers back in the 70's and 80's to mitigate their resonance frequencies. Note L3 and L4 below in the L212 parts list. These exact same L212 parts are shown above in my L-Pad board photo. Way back in the early 80's I purchased a bunch of each from JBL Parts.

It turns out that he also used them in the 4344 Mk II many years later sans the high DCR values, at that time he used resistors in series. L3 and L6 in the schematic.

Thanks a lot for that clarification!

So these 7.5ohms DCR coils on your L-Pad board photo do not belong to the 3155 circuit at all, right?

[Odd]

Thanks a lot for that clarification!

So these 7.5ohms DCR coils on your L-Pad board photo do not belong to the 3155 circuit at all, right?

They are also used in 3155

[Hans Bleeker]

They are also used in 3155

Can you explain to me where they are used in the 3155, see attached schematic.

[Odd]

They are not used in the original 3155
I was referring to 3155 equivalent schematic in post 50

[Hans Bleeker]

In that schematic I dont see that coil with 7.5DCR or a combo Resistor - coil, what am I missing, I'm speaking schematic, I build that filter thats posted but not with a 7.5Ohm coil. Is there an assumption I should have known it should be there but without putting it in the schematic?

[Odd]

In that schematic I dont see that coil with 7.5DCR or a combo Resistor - coil, what am I missing, I'm speaking schematic, I build that filter thats posted but not with a 7.5Ohm coil. Is there an assumption I should have known it should be there but without putting it in the schematic?

You are right in terms of schematic.
Photo in post 50 and 57 shows DIY 4345 as "4313B" built it.
There they are.

[Hans Bleeker]

This is realy stupid, I never noticed those remarks about that coil resistor network , red all again starting from post 1, how could I mis that, might be the reason I have to turn my L-Pad almost to the closed position to get the 2"driver in balance, its way to loud . I wonder since its probably rounded of values, would an 6.8 ohm resistor and a 3.9mH coil do the job as well on the 2202 that is ofc? Thats the values sold in Europe. The larger coil value shifts the frequency only little bit lower, and the total DCR will be 6.95 together with the coil, I would say dampens a little bit more but hope it wont influence the rest of the design to much.

[martin2395]

Hi Hans,

You can order custom value coils through RumoH in the Netherlands, not sure about the DCR though.

[Odd]

1.0 mH and 3.5 mH air core inductors is fairly common values.

You can buy here, and in many other stores.

For exact DCR put a resistor in series.

[Dr.db]

@ Odd:
Please don´t get me wrong, I don´t want to dubitate your statement but 4313B´s posting says this L-Pad board was used with the 4344 network. He had a seperate 4355 network...
I have read all your linked threads but I can´t find any posts saying their have to be 7,5 ohms coils in the 3155 equivalent network.

The L-Pad board in the photo above was for the 4344 MkII network that I also tried. The compression driver has the 1.0 mH 7.5 ohm DCR coil across its terminals and the 2123H has the 3.5 mH 7.5 ohm DCR coil across its terminals as per Greg's schematic.

Listening to the 4344 Mk II network side by side with the 4355 network I personally preferred the 4355 network, greater power and dynamics, which is what I expect from such a large loudspeaker.

[Odd]

The crossover will work just fine without, but better with.

[Dr.db]

Thanks for your patience!