It will not make technical or sonic sense. Based on your musical taste, you select the type of bass you want which detects the type of cabinet. You must pick your driver carefully to meet the requirement of your cabinet selection.
Sonce, very well put. I believe that the aperiodic can go as deep as a vented cabinet with loss in efficiency. In particular, it looses the punchiness and boomy bass some listener carve.
Usually, the same driver can work well in either a vented or an aperiodic box. For a closed box design, you probably want a high compliance driver.
The fiber glass or wool stuffing plus the resistive vent in an aperiodic cabinet change the acoustic loading to the driver completely making it non-resonant (not single frequency tuned). The vented box software does not take into consideration of the non-linear character of the stuffing and is usually not applicable.
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As you might have noted from my earlier post I wasn't just thinking of aperiodic for bass, and I do think the differences in enclosures with the same driver would be instructive. The vas question still has me wondering.
What question about Vas? As far as I'm aware, all we're dealing with here are leaky sealed boxes / [more-or-less] resistively vented boxes. T/S filter theory still applies.
As far as bass enclosures go, you can obtain a lower system Q for a given box size than a sealed box, so a smaller cabinet can be used for the same alignment. You may (may) also be able to reduce the LF impedance peak, although it's rarely if ever flatted, so they are not 'non resonant'. About the closest you can get to the latter is a maximally flat impedance TL, or a full-sized horn within its passband.
As far as bass enclosures go, you can obtain a lower system Q for a given box size than a sealed box, so a smaller cabinet can be used for the same alignment. You may (may) also be able to reduce the LF impedance peak, although it's rarely if ever flatted, so they are not 'non resonant'. About the closest you can get to the latter is a maximally flat impedance TL, or a full-sized horn within its passband.
In reference to my post a few posts above(#75), that was my intention with a 3-way I built using a SS 25W/8565, aperiodic loaded in a 60-70 litre box, when that woofer could use an even larger box due to it's unusually large 225L Vas. Seemed like the right thing to do with that driver, anyway.
To me a 3-way adds a sub below the woofer in a WAW.
You could use it for a mid in a conventional 3-way, it would have all the same advantages.
dave
Yes, I did with a Peerless TA305F, a 12 inch woofer they built in the US back in the 80s. I tried vented and then sealed. I was not happy with either. Eventually I tried a Scan Speak Variovent aperiodic port. That one was the keeper for 20 years until the foam surround rotted out.
I have a dual 15" single reflex bandpass sub in my living room. It was originally aperiodic. I changed it to a sealed back chamber because the aperiodic vents were super ugly. (I basically took a sealed back chamber and drilled a bunch of holes in it until the F3 started to get lower.)
The aperiodic thing worked; it played measurably lower. But when I sealed up the holes (for cosmetic reasons) it didn't sound any different whatsoever.
My hunch is that we can't hear the difference between a subwoofer with an F3 of 30Hz and a subwoofer with an F3 of 28.5Hz
For my project, the aperiodic thing might have been more interesting if it was in some type of transmission line, like the B&W Nautilus designs. A larger vent may have also worked better.
Long story short, give it a try! They're hard to screw up and it's an interesting angle on what is (mostly) a sealed box.
I agree, "give it a try" seems the best way to go. Also I'm just thinking that hearing the difference in the midrange might be a lot easier than trying to hear differences in the subwoofer range. And I suppose if scan speak says their vario-vent reduces the apparent enclose size by 20% then as a producer of well regarded drivers they must have some data for making that statement.
My observation with the aperiodic was that by relieving the pressure, the cabinet walls were quieter. I thought the lower mids were cleaner with less boom.
It would be. You've just lowered the system Q, increasing the relative damping of the alignment, which in many cases will have an impact up into the lower midband. That may also have a slight impact on vibrational modes in the structure, but you'd have to be bleeding a heck of a lot of pressure away & assuming the box was well-built, as I'm sure it was, the effects should be swamped out by the change in the acoustic alignment. That said, if it was MDF every little helps, as it's not great for bass enclosures unless you really ratchet up the panel thicknesses.
No one has answered this. I read somewhere that it does, but having read more I doubt this is the case, can anyone tell me from experience?
you may wish to read http://www.ejjordan.co.uk/PDFs/A-Cabinet-of-Reduced-Size-with-Better-Low-Frequency-Performance.pdf
In terms of filter theory a speaker in closed box can be described as a second order high pass if Q is about 0.75 it is a Butterworth. If a capacitor is in series with the - electrical analogue- of the 2nd order hi pass it becomes a thrid order hi pass. Thus a flow resistance is just this a capacitor with a parallel resistor in series with the said second order hi pass. The same thing was announced with much unnecessary fanfare as hi pass filtered closed box with a "real" capacitor in series with the speaker in closed box
In terms of filter theory a speaker in closed box can be described as a second order high pass if Q is about 0.75 it is a Butterworth. If a capacitor is in series with the - electrical analogue- of the 2nd order hi pass it becomes a thrid order hi pass. Thus a flow resistance is just this a capacitor with a parallel resistor in series with the said second order hi pass. The same thing was announced with much unnecessary fanfare as hi pass filtered closed box with a "real" capacitor in series with the speaker in closed box
This is a BS explanation that reeks of confirmation bias and a misunderstanding of how the box works. The amount of sound radiated by any enclosure is proportional to the pressure in the box. The only way you can get less pressure is if there is less sound. This means that the poster merely prefers less bass.
Ron, put a resistive hole in a box and the inside pressure will be relieved because it is leaking out.
dave
dave
See my post #73 on this thread.
I use a pair of modified "Wharfedale M-138 Transmission Line Monitor", which is an aperiodic design. See my post #38 atkeilau said:
TDL Studio 3 crossover upgrade
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Fernando's observation that in a aperiodic enclosure, "the cabinet walls were quieter" and "the lower mids were cleaner with less boom" are correct. Even if his explanation is not. The aperiodic enclosure is non-resonant in nature which means no single tuned frequency. That reduces the resonance of the cabinet as compared to tuned closed or vented bass reflex boxes. For the tuned cabinet design, both the fundamental frequency and its higher harmonics contribute to the box "singing", making reinforcing brace and cabinet wall damping more important.
It is not to say that an aperiodic enclosure does not benefit from reinforcing brace and cabinet wall damping. It just has a better starting position. The internal sound pressure is A factor, but it does not explain the difference between tuned vs. non-resonant enclosure.
It is not only the amount of bass, but also the quality of bass that counts. You can read Ted Jordan's paper to understand what that means.
I hope that all of us can remain civil while discussing audio topics. That is music all about.
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