I'm doing a "thought experiment" by originally doing a three-way, but was concerned an Eighteen wouldn't work right up to the intended 700hz cross-over point. The specter of a four-way cropped up...with an appropriate ten-inch in a 0.5 Qts sealed will roll off to match with an 80hz coil for the eighteen. Yes, the amp will see impedance approaching four ohms when the eighteen comes in ??? Foolish idea or what?
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Rick...
I guess you're not counting on the 18" to begin narrowing at 700, you'd rather have a wide radiator.
Next, you don't want to high pass the 10".
Is there a reason, other than the lower impedance, for not doing this? Yes, the different rolloffs might put the 10" and the 18" somewhat out of phase. This would reduce efficiency and knock down the response.
Next, you don't want to high pass the 10".
Is there a reason, other than the lower impedance, for not doing this? Yes, the different rolloffs might put the 10" and the 18" somewhat out of phase. This would reduce efficiency and knock down the response.
4 way sounds fun.
Sounds good to me. I would tolerate a 4 way just for that reason.
Using a woofer that has a actual very low Fs.
Assuming the inductance is rather high, bring in a smaller sealed woofer to complete upper bandwidth of bass.
Sealed the way to go.
I have gone back n forth with either a 10" or 8" for midbass.
Wanting enough off axis to use a dome mid instead for mids.
The dome of course having smaller size and better sensitivity.
So the mid bass needs enough top end to use a very small mid.
Sounds good to me. I would tolerate a 4 way just for that reason.
Using a woofer that has a actual very low Fs.
Assuming the inductance is rather high, bring in a smaller sealed woofer to complete upper bandwidth of bass.
Sealed the way to go.
I have gone back n forth with either a 10" or 8" for midbass.
Wanting enough off axis to use a dome mid instead for mids.
The dome of course having smaller size and better sensitivity.
So the mid bass needs enough top end to use a very small mid.
I have more or less that system, with a Dayton RSS460 (18 inch/460 mm) crossed over actively (LR4) at 160 Hz to a baby full-range bookshelf comprised of a Purifi PTT6.5W8 (7 inch/176mm) passively crossed over at 2 kHz to a Scan-Speak D3004/6600 AirCirc tweeter.
Yes, I know, subwoofers shouldn't go above 100 Hz. Too bad. The RSS460 sounds just fine up to there, and crossing over at 160 is more coherent between bass guitar and kick drum than at 100, at least to my ears.
Even at high volumes the 7 inch barely moves. Crossing over an 18" at 700 is asking for trouble, however, because either it's close to cone breakup or it's already in ugly resonant modes.
If you can swing the extra amp sections then active between woofer and everything else is the way to go.
Yes, I know, subwoofers shouldn't go above 100 Hz. Too bad. The RSS460 sounds just fine up to there, and crossing over at 160 is more coherent between bass guitar and kick drum than at 100, at least to my ears.
Even at high volumes the 7 inch barely moves. Crossing over an 18" at 700 is asking for trouble, however, because either it's close to cone breakup or it's already in ugly resonant modes.
If you can swing the extra amp sections then active between woofer and everything else is the way to go.