Filter help needed for SR4725a clone with 2226J and 2426H/2370

[sebackman]

Dear all,

I have a bunch of JBL 2226J (16 ohms) woofers and two pairs of 2426H/2370 laying around and I'm planning to build 2 pairs of "party" boxes.

My idea was to copy the SR4725a filter but it was made for the 2226H (8 ohms). -And I don't want to run 2*15" (16 ohm/2 = 8 ohm) in each box due to size.

My question is if anybody on this fantastic forum does have a re-calculated filer for a SR4725a but with a 16 ohm woofer?

Or if someone do have any other idea on filter for the 2226J and 2426H/2370 combination.

Or if someone can do the re-calculation including the adjustment of attenuation and share.

One pair of the drivers are actually 2417H's but they should behave very similar, I guess.

All help much appreciated.

Kind regards
/RoB

[Ruediger]

... in theory at least.

If You go from 8 Ohm to 16 Ohm, multiply all resistor and inductor values by two, and divide all capacitor values by two.

The TS params Le and Re for the 2226 follow this pattern quite well.

So modify the 4725a crossover as follows: replace the 27 uF capacitor by one with 13,5 uF, replace the 2,6 mH coil by one with 5,2 mH.

Leave all other components as they are.

Ruediger

[sebackman]

Hi,

Thank you.

In a basic filter without sensitivity compensation between the drivers and no compensation for driver/horn drop-off in higher frequency, I agree. So for the woofer I have to change the components as suggested.

I found a newer and much simpler version of the filter in the SR4725X. The only difference between the boxes seems to be the filter and since it is newer and less complicated I will use that.
JBL SR4725X

Would not the fact that my 2426H is 8 ohms and my 2226J is 16 ohm's (compared to 8 ohm for both drivers in the original JBL box) change the need for attenuation of the 2426H to achieve the correct output? At the same voltage on the terminals the 16 ohm woofer would produce 3db lower sound pressure compared to the 8 ohm version. The 97db JBL specification is the same for both woofers but that is @ 1W/1m which would need higher voltage (2x) for the 16 ohm woofer. Right?

If this is true, the SR4725X filter for the 2426H also needs to be tweaked to reduce the sound pressure 3db compared to the original. Or?

How to I change the components in the filter to do that. The extra headroom could be used to boost the higher frequencies a little maybe…

Or do I just put an attenuator link (two resistors) between the filter and the driver.

Best regards
//RoB