I would not call the extra bass "free", it has its drawbacks. In a ported design, the driver is uncontrolled in displacement below its tuning. Hence, unless the port tuning is below the lowest frequency that the sub will ever see, its not "free" as it will severely limit the linear performance at higher SPLs. Closed box response can be raised up below resonance and the driver stays in control as long as the driver has enough excursion capability to handle it. That's why I use big drivers with lots of excursion eq'd well below their resonance. My bass never losses control.
I found MSO so confusing and hard to implement that I gave up.
RE Sealed boxes that are bigger than optimum.
Point taken re: DSP i.e. any size box you like. The only thing I assume is needed (but not stated) is to put a very low frequency high pass filter in? As I found out, an 8" speaker in a (larger) box designed for a 10" resulted in the coil hitting the backplate.
This would not happen in the (smaller) box at the same power. The effect of a large (too large) sealed box is a bit like the vented enclosure below resonance.
Point taken re: DSP i.e. any size box you like. The only thing I assume is needed (but not stated) is to put a very low frequency high pass filter in? As I found out, an 8" speaker in a (larger) box designed for a 10" resulted in the coil hitting the backplate.
This would not happen in the (smaller) box at the same power. The effect of a large (too large) sealed box is a bit like the vented enclosure below resonance.
You are taking a trivial rare issue with sealed boxes (which I can't recall anybody every moaning about) and magnifying it into a shortcoming of the type of "suspension" which is otherwise favoured for its SQ.
There is no "optimum" in human life without specifying just what it is you are optimizing. BTW, that is sometimes a hidden secret in sims... as in the present instance.*
There is only a single parameter for sealed boxes: volume**. The bigger the box, the less low freq low end you are throwing away. The bigger the better.
B.
* now a days with DSP, we can EQ the FR a lot, so that isn't primarily what anybody needs to optimize today
** or when stuffed, effective volume and isothermal behaviour
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Time out please. I just recounted my experience with a small driver in a large box. I don't recall moaning or showing negativity, just what I had observed.
Assuming I'm listening and interested in solutions I wasn't aware of (I am) can I ask the question again?
Is a subsonic filter required for a driver in a conventionally large enclosure required? I am guessing yes, but am quite happy to be advised.
😎
Assuming I'm listening and interested in solutions I wasn't aware of (I am) can I ask the question again?
Is a subsonic filter required for a driver in a conventionally large enclosure required? I am guessing yes, but am quite happy to be advised.
😎
In the new world of DSPs, simple to block lowest frequencies but not too practical to get a sharp slope otherwise.
Increasingly important these days to keep unhearable, unplayable, and possibly undesirable very low notes out of your driver. That's because systems today can feed low notes to the driver and no constraints on what unplayable garbage might flow from an aberrant (or typical) recording studio.
Letting a subwoofer cone flop about making unhearable vibrations harms the good vibrations, even for those who don't believe in Doppler distortion per se.
I can remember turntable noises and off-centre holes, as a youth. Wow, as we said.
B.
Nor in the larger, more efficient, box at the same SPL when driven with fewer watts. Reducing box volume "to increase power handling" seems rather upside down.
I don't think that there is one right answer here. It depends on the ability of your subs to handle what you throw at them. I don't use any subsonic filters, but I am not even close to the limits with my multiple subs. If you are close to the limit then you might want to do this with a shallow filter.
24dB slope is pretty good but the math is not your friend at low frequencies since even a 24dB filter is nothing like a brick wall.
Unless you own a copper mine, no way to get 24dB except electronically or digitally.
B.
So a PEQ should make less of a phase change, than a shelving or LR filter?
I do not play that loud and have 4 x 12" subs for a 50 squaremeter room, so I dont protect my subs from low frequencies at the moment, at havent had problems so far.
Why, of course not passive. Linkwitz-Riley 24dB is my favorite, I put it everywhere I can, LR48dB can do too 😉
PS. A humble Dayton Audio sub amp SA1000 has a switch-on infrasound filter , among other cute functions.
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Generally PEQs are 2nd order and a 24 dB/oct slope is fourth order, so the phase shift is double. But then if the PEQ corrects a room peak then it also corrects the phase, so there is zero phase shift.
Ok. So since it is a linear problem and if I do it right(proper measurements). Then the phase will follow the amplitude response, so that no serious problems occur - at least none we can hear?
Is that why most correction software uses IIR for subwoofers and FIR for the rest - besides the latency issue?
I would say "yes" to the first and "probably" to the second. I am not an expert on what the software guys do and why. I have never used it. I don't believe that it is necessary.
That's nice and thank you for your answer.
That simply means that I understood a few things and proof that the theory works in my room and with my system too 🙂
That totally depends on the transfer function of your vented sub.
If you make that completely identical to a closed system (so the frequency response and group delay are (nearly) identical) there is only very little difference.
At that stage it comes down to the non-linearities of your port vs more cone-excursion in a closed-box system.
The problem is that seldom people compare systems that are equal.
Is it needed?
Well, that totally depends how low and load someone wants to go.
Also depending on other criteria like design and visuals.