The intent is to fill in the low end with the Advent woofer, rolling off with a 12dB/octave active LPF at either 90 or 180Hz. I know my hearing rolls off above 10KHz, so I'm not too concerned about the 87H driver lacking an extended high end. The 250Hz-5KHz range is laid back and smooth, perfect for my taste. I love the sound of the A-35 mid and woofer.

It moves the Fc to a lower freq relative to the 200-500Hz range. I really don't mind a little bump in the 50-100 Hz range from the higher Q. I can't quantify as I haven't actually measured the weights. On my big speakers, I've actually seen a larger Q and a lower Fc with a light stuff rather than heavy. That it has to be very tightly packed to come close to the original fiberglass stuffing in the Peaking above Fc and should cross the passband level at Fc, - 3 dB should be below Fc.Īre you talking acousti-stuff for the polyamide fill? Or what exactly did you use? I've found Lowering Qm simulated theĮffect of the fiberglass behind the driver as an acoustic resistance. Matches that measured which should be around. Then you should lower Qm of the driver so that the Qtc Simulate the effect of the enclosure filling so that the simulated Fc matches that measured You want to increase the enclosue volume to Your simulation does not sound quite right. But that's another story for another forum. I had great success with loose poly fill in my previous 3-way tri-amped 120 liter box, where I achieved -3dB at 30Hz with a 10' Scanspeak woofer. Ear check confirms the LF performance is still there. I used a much looser polyamide fill when I restuffed and tore the pieces up into small chunks. You've saved me many hours of impedance measurements.Īnd boy did they tightly stuff the box with fiberglas!!!.

It should be fine for my experiment which was to fill in the low end of the Dynaco A-35s.Īgain, many thanks. But at least I now know what the LF performance should be. Of course, the project described in my previous post removes the tweeter and inductor. But this also depends on individual taste. With today's program material the tweeter should probably be in 'Extended' position to move the tweeter xover up in freq in order to tame its output. So I'm finally understanding their design which was to boost the HF response for 'older' program material ('Decrease' position). The large inductor on the LPF was there because of the high woofer impedance (23-50 ohms) at the 3-7KHz xover point (xover depends on where the switch is). WinISD shows small 1dB peaking between 50-100 Hz and a -3dB at 47 Hz. The large Vas makes for a Q=1 in the box.

Large Advent Speaker Serial Numbers