Zaphaudio SR71 with 4 ohm ER18RNX

Ugg10

Member
2017-11-18 9:59 am
UK
From what I understand just matching the impedance is only the start. It will have a different sensitivity (fairly easy fix) but the TS parameters will be different so box size and tuning will be different.

Example - using the mh-audio bass reflex calculator as a quick estimate with a similar driver -

Satori MW16p-4 = 13.3l box, f3 of 50hz with 5cm diam x 22cm long port and spl 88dB (flat response)

Satori MW16p-8 = 24.7l box, f3 of 39hz with 5cm diam x 15cm long port and spl 87.5dB (flat response)
 

bcrazy

Member
2005-10-20 8:43 pm
Measured the impedance curve. Seems to pretty much be about halv the impedance of the 8 ohm version, apart from peaking at a higher fs

ER18RX4ohm_impedance.jpg
 

TMM

Member
2007-09-01 8:37 am
Australia
T/S parameters look way different to the 8ohm version. You're probably going to get a peaking midbass and a lack of lower bass in the enclosure designed for the 8ohm version. It'll probably want a sealed enclosure that is 20-50% larger. Vented enclosure will need a total redesign.

Aside from that, make all inductors and resistors in the woofer section half the value, make caps in the woofer section twice the value.

Adjust R0 to between 1-3ohm to set tweeter level to match.