Does this matter when the cutoff is adequate? i.e. 12db down 10hz below Fs? I have a "house curve" I tend to prefer to throw on after EQ'ing the room to flat. Is it bad to have a 20hz boost and a 50hz cutoff?
A high pass somewhere just below tuning.
For serious EQ you would do sealed (+ more amp & excursion). One of the pro companies ran they subwoofers fully below small box resonance.
dave
For serious EQ you would do sealed (+ more amp & excursion). One of the pro companies ran they subwoofers fully below small box resonance.
dave
Scott has folded up that TL into a Baby Labirinth but for that one you will have to wait for a drawing ( the code used needs to be translated)
dave
dave
"Fs" is the driver's free air resonance. The resonance in a sealed box, Fcb is always higher than Fs.
Four times the displacement (excursion) is required for each halving of frequency (one octave lower) to maintain the same output level in a sealed box.
Typically a bass reflex box tuning frequency, Fb, would be tuned near Fs for maximum output and "flat" response to near Fb.
The Speedster's Fb is around 55 Hz. Cone excursion and impedance are the least at Fb.
At Fb, the output of the port and the front of the cone are "in phase", resulting in more output than a sealed box.
Lower tuning (Fb) in the same size box will result in less output at Fb.
Cone excursion is highest about 1/3 octave above Fb, below Fb, the port is an air leak, it's output is out of phase with the cone, cabinet response drops off at around 24dB per octave, any large boost below Fb will simply blow air as the cone excursion rises without any appreciable output.
If you want much SPL below the Speedster's Fb, get some subs that can provide the displacement needed.
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Construct a 3rd order 60hz electronic high pass xover and route the bass to a 8 inch sub in a tuned enclosure. Then adjust your eq to match
So to “max out” the speedster via EQ I have to run the cutoff at or before the Fb. Right now I’m running a fourth order at 50hz after hearing what the comments had to say.
The next and possibly last step I would take beyond port redesign is running FIR filters to counter all this group delay. I really wish I could run a variable cutoff to increase hz with spl, but that would be very complicated I’m sure. Plus the ostensibly required delay may not be optimal.
Are those nulls in low frequency response that you're trying to correct for due to port or driver reflections?
you can use a larger diametre vent which will not chuff but it will be much longer to keep the tuning the same so you may be looking at a cabinet mod or a whole new cabinet. You could experiment with adding a sub. If you have trouble blending. I suggest adding a sub into your system try blocking the vents on your speakers use them as a sealed box you will get less bass hump but you will get deeper extension sealed vs reflex and adding a sub be should easier.
Group delay and port design won't address the issue: there is no replacement for displacement.
If you are hearing port noise, the driver is also likely exceeding Xmax. Your 4" driven past Xmax will sound bad reproducing upper frequencies to the 4kHz crossover. If you see the driver moving 10mm (3/8") peak to peak it has reached it's 5mm Xmax, past that distortion rises, and amplitude modulation will cause the upper frequencies to "gargle" on extended bass notes.
The pair of 4 probably hit Xmax around 90-96 dB (peak) at one meter, at 50Hz that sounds about equal in loudness to medium level (60dB) conversation.