APERIODIC ENCLOSURE- Very small subwoofer boxes that "breathe" through a moving membrane. Both the membrane and cone can not be in the same exterior space. Either the membrane part has to be isolated by cutting a hole in the car so that it is outside, or the subwoofer has to be isolated from the rest of the trunk in a similar fashion to free air woofers. The "box" has to be as small as possible (ideally the membrane should be right up against the sub), since it is used only for coupling the sub and membrane. Aperiodic membrane configurations are very hard to design and tune, but give good frequency response and respond faster to transients, giving accurate and tight bass as opposed to boomy sound. They are not ruled by Thiele-Small parameters like other designs, so any woofer would work with the membrane.
THIS SOUNDS TO BE QUITE INTERESTING..HAS ANYONE OUT HERE EVER TRIED MAKING SUCH AN ENCLOSURE.. IF YES PLEASE GUIDE ME CAUSE I AM PLANNING TO MAKE ONE AND THEN START A MASS PRODUCTION ALONG WITH THE BANDPASS ENCLOSURES I AM ALREADY SELLING..
Replies (6)
asplundher on 10/18/2004 19:13:56
That info can be somewhat misleading (no offense).. The fact is that even though they can work with almost any sub; higher Q/ high Vas subs yield better results. The higher Q subs costs more and are rare. The low frequency ouput is not what most will like unless they listen to classical music and such. Also the design calls for sigificantly more power than a normal setup. The actual box will have to be measured by impedance rather than thiele/small predictions as stated. This can be very annoying when each box will have to tuned to the specific vehicle tedious work if you have to keep building boxes for the same car.
In my opinion the cons outweigh the pros, but if you really want to try, Partsexpress sells a Scan-Speak aperiodic membrane fairly cheap. You could experiment around with it a little before jumping head first.
Victor on 10/18/2004 19:21:51
well i got this info from a website.. dont remember the url.. but thats what i wanted to check out.. is it feasible??
Thanks.. please educate me about this particular design form if u know something more about it..
Victor..
asplundher on 10/18/2004 19:35:47
It is a very hard topic to find, though I know your hungry for knowledge. I've learned most of the info from experience and from reading Vance Dickason's (the "Stereo Bible"). If I find anymore I'll fill you in on where to look.
asplundher on 10/19/2004 10:01:39
Oops, let me correct myself. The one part I used was a Variovent by Scan-Speak. It was a roughly 5" diameter short port kind of "thingy". Sandwiched between the front and back "grills" of the vent was fiberglass insulation. This worked to allow a resistive path of air flow for a underdamped woofer, which the end result is readily seen with higher Q woofers that require large enclosures in "home stereo". Lower Q woofers are normally used for vented designs.
Now in car audio, this may not readily apply. Although they work the same way and are measured the same; the technique and woofer selection may well be different. The membrane might also be quite different. All this I assume for the environment and electronics are different.
Heres a link if you hadn't seen this one already: http://www.maximacar.com/aperiodic.htm
Victor on 10/19/2004 11:33:54
Thanks asplundher.. the link was quite useful to have the basics of a Aperiodic membrane enclosure.. but they have not discussed a very important aspect " The membrane"
the thickness.. the type .. the weave of the membrane.. material used to make the membrane etc.. lemme know if u find something on it.. i am lookin around too.. so incase i find something i shall let u know..
one more thing.. are u interested in taking up this project?? lemme know..
thanks
Victor...
asplundher on 10/19/2004 12:17:09
Heres another quote from another site:
" An "aperiodic membrane" is one part of a type of subwoofer enclosure.
It is an air-permeable sheet which has frequency-dependent acoustical
resistance properties. The original design goes back to Naim, for use
in home systems, but has been applied by several individuals and
companies in car audio.
The completed system will be aperiodic, which means it will prove to be
over-damped with a Q well below 0.7. In contrast, the most commonly
used sealed enclosures have Qtc's in the range of 0.8 to 1.1 which are
considered, by definition, to be underdamped. When improperly used, a
high-Q system may have poor transient response, nasty peaks in
frequency response, and high rates of roll-off. Aperiodic systems will
feature excellent Aperiodic systems are characterized by better
transient response, flatter frequency response and somewhat extended
low frequency response.
Another benefit of the system is that you can pretty much choose
whichever driver you'd like to use, as long as they are big. The
Thiele/Small parameters (which would normally determine what kind of
box would be used) are taken into consideration by the membrane
designers so that the response is extended and overdamped, regardless
of the characteristics of the driver.
Physically, the aperiodic membrane isn't for every car. It requires
sealing the trunk from the passenger compartment in an air-tight
manner, as well as sealing the trunk from the outside for best results.
The drivers are then mounted into the baffle between the passenger
compartment and the trunk, as would be standard in an
infinite-baffle/free-air set-up. The aperiodic membrane is then placed
either in front of the driver or behind the driver, depending on the
type. When mounting behind the driver, the membrane is used as the
rear-wall of a very small box which the driver sits in (as in Richard
Clark's infamous Buick Grand National). So, in short, it's not
suitable for trucks, jeeps, R/V's, or hatchbacks.
You should probably only get an aperiodic membrane if you've got money
to burn, lots of amplifier power, some big subs, a sedan, a desire for
trunk space, and no wish to boom. If your tastes lean towards
bass-heavy booming, as opposed to well-recorded acoustic instruments,
you're not going to be pleased with the result."
Still this another vague description that provides very little extra info. All that I can tell is that they are complicated and expensive.
If you can find the membrane used for autos I'm quite sure it will be relatively high in cost. I've been looking but can't seem to find a direct link to one other than the fact that the same engineers of Dynamat makes one (Dynamic Control of North America,Inc).
THIS SOUNDS TO BE QUITE INTERESTING..HAS ANYONE OUT HERE EVER TRIED MAKING SUCH AN ENCLOSURE.. IF YES PLEASE GUIDE ME CAUSE I AM PLANNING TO MAKE ONE AND THEN START A MASS PRODUCTION ALONG WITH THE BANDPASS ENCLOSURES I AM ALREADY SELLING..
Replies (6)
asplundher on 10/18/2004 19:13:56
That info can be somewhat misleading (no offense).. The fact is that even though they can work with almost any sub; higher Q/ high Vas subs yield better results. The higher Q subs costs more and are rare. The low frequency ouput is not what most will like unless they listen to classical music and such. Also the design calls for sigificantly more power than a normal setup. The actual box will have to be measured by impedance rather than thiele/small predictions as stated. This can be very annoying when each box will have to tuned to the specific vehicle tedious work if you have to keep building boxes for the same car.
In my opinion the cons outweigh the pros, but if you really want to try, Partsexpress sells a Scan-Speak aperiodic membrane fairly cheap. You could experiment around with it a little before jumping head first.
Victor on 10/18/2004 19:21:51
well i got this info from a website.. dont remember the url.. but thats what i wanted to check out.. is it feasible??
Thanks.. please educate me about this particular design form if u know something more about it..
Victor..
asplundher on 10/18/2004 19:35:47
It is a very hard topic to find, though I know your hungry for knowledge. I've learned most of the info from experience and from reading Vance Dickason's (the "Stereo Bible"). If I find anymore I'll fill you in on where to look.
asplundher on 10/19/2004 10:01:39
Oops, let me correct myself. The one part I used was a Variovent by Scan-Speak. It was a roughly 5" diameter short port kind of "thingy". Sandwiched between the front and back "grills" of the vent was fiberglass insulation. This worked to allow a resistive path of air flow for a underdamped woofer, which the end result is readily seen with higher Q woofers that require large enclosures in "home stereo". Lower Q woofers are normally used for vented designs.
Now in car audio, this may not readily apply. Although they work the same way and are measured the same; the technique and woofer selection may well be different. The membrane might also be quite different. All this I assume for the environment and electronics are different.
Heres a link if you hadn't seen this one already: http://www.maximacar.com/aperiodic.htm
Victor on 10/19/2004 11:33:54
Thanks asplundher.. the link was quite useful to have the basics of a Aperiodic membrane enclosure.. but they have not discussed a very important aspect " The membrane"
the thickness.. the type .. the weave of the membrane.. material used to make the membrane etc.. lemme know if u find something on it.. i am lookin around too.. so incase i find something i shall let u know..
one more thing.. are u interested in taking up this project?? lemme know..
thanks
Victor...
asplundher on 10/19/2004 12:17:09
Heres another quote from another site:
" An "aperiodic membrane" is one part of a type of subwoofer enclosure.
It is an air-permeable sheet which has frequency-dependent acoustical
resistance properties. The original design goes back to Naim, for use
in home systems, but has been applied by several individuals and
companies in car audio.
The completed system will be aperiodic, which means it will prove to be
over-damped with a Q well below 0.7. In contrast, the most commonly
used sealed enclosures have Qtc's in the range of 0.8 to 1.1 which are
considered, by definition, to be underdamped. When improperly used, a
high-Q system may have poor transient response, nasty peaks in
frequency response, and high rates of roll-off. Aperiodic systems will
feature excellent Aperiodic systems are characterized by better
transient response, flatter frequency response and somewhat extended
low frequency response.
Another benefit of the system is that you can pretty much choose
whichever driver you'd like to use, as long as they are big. The
Thiele/Small parameters (which would normally determine what kind of
box would be used) are taken into consideration by the membrane
designers so that the response is extended and overdamped, regardless
of the characteristics of the driver.
Physically, the aperiodic membrane isn't for every car. It requires
sealing the trunk from the passenger compartment in an air-tight
manner, as well as sealing the trunk from the outside for best results.
The drivers are then mounted into the baffle between the passenger
compartment and the trunk, as would be standard in an
infinite-baffle/free-air set-up. The aperiodic membrane is then placed
either in front of the driver or behind the driver, depending on the
type. When mounting behind the driver, the membrane is used as the
rear-wall of a very small box which the driver sits in (as in Richard
Clark's infamous Buick Grand National). So, in short, it's not
suitable for trucks, jeeps, R/V's, or hatchbacks.
You should probably only get an aperiodic membrane if you've got money
to burn, lots of amplifier power, some big subs, a sedan, a desire for
trunk space, and no wish to boom. If your tastes lean towards
bass-heavy booming, as opposed to well-recorded acoustic instruments,
you're not going to be pleased with the result."
Still this another vague description that provides very little extra info. All that I can tell is that they are complicated and expensive.
If you can find the membrane used for autos I'm quite sure it will be relatively high in cost. I've been looking but can't seem to find a direct link to one other than the fact that the same engineers of Dynamat makes one (Dynamic Control of North America,Inc).
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