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In Reply to: RE: Bass reflex port -tuning help please posted by Alnicoman on February 26, 2012 at 08:49:19
It's simple, the Qts is too high for bass reflex.
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So does that mean I should just build sealed enclosures?
The PE specs say it will work well in a vented system?
I'd hate to lose the efficiency by sealing the enclosures.
In a proted box, good old boxplot says 7.7 cubic feet, per speaker - i.e. 15.4 cubic feet for two. Extension to 28Hz but so what? The 2mm xmax would make that pretty useless.
In your box, sealed, I get about -3dB at 60Hz, with a mild 1dB hump around 110Hz. Not bad.
The port has no effect on midband sensitivity, it only changes the deep bass extension.
Thanks Paul.
Should I stuff the enclosure completely full of insulation, or just attached it to the top, bottom, sides, and back?
Depends on the stuffing. Unless you have access to detailed knowledge of the acoustical properties of the stuffing, experimentation and listening are the order of the day.
I was going to point out exactly the same stuff as Paul, but probably less well.
A couple of things I can add:
1) Most speakers - or, at least every speaker I have owned or modelled - are excursion limited (you can't turn it up beyond X loudness because the cone will move too far) rather than power limited (where the limit is the coil overheating).
2) These speakers require a huge box to work well vented. In a small box (and for these speakers, 100 litres each is small), sealed may be less efficient, in that it will have less output for its lowest half octave, but it may be able to play louder overall than a 100 litre vented box, and have flatter response (less of a resonant peak).
E.g. you feed a hypothetical 2mm excursion woofer a mix of tones at 20, 40, 80, 160, 320, 640Hz
100litre sealed box - at 1.5 watts, it reaches its excursion limit.
100litre vented box, tuned to 40Hz - it can take only 0.5 watts before reaching excursion limit.
...the vented box is more efficient, but at max excursion, the sealed box will be getting triple the power, or about +4dB, for most of its range.
Tried modelling a transmission line?
I think modeling just about anything is beyond my capabilities.
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