Whats a aperiodically-coupled bass-reflex box?

[natural sound]

Originally Posted by talaerts

Yes, I remember a number of variovent equipped Dynaudio designs in old Elektor magazines.

Sounds like it's a old type of box design? Jm

[planet10]

You using the FE126 as a mid-tweeter?

dave

[natural sound]

Originally Posted by planet10

You using the FE126 as a mid-tweeter?

dave

No I paid a guy I knowto make a box design for the fostex fe126en drivers and it came out to be this kinda box? I have never heard of this type of box before? So I thought I would ask if there were any programs on how to do this kinda box and how would you go about it? Looking into getting a deeper understanding? Jm

[planet10]

FE126 really needs a horn. If i eas doing an aperiodic box for it, it would reach 150-200Hz.

dave

[Keriwena]

In the old days, for a small manufacturer that was dependent on the slim selection of OEM drivers, the process was to find a woofer with good mids, as the tweeters weren't all that back then, and the crossover region was critical. The more the woofer could handle, the better. Having found a woofer, then we'd futz around with the box, trying to get acceptable bass out of it.

These days, there are many, many more choices, and woofers behave better on the top end, while tweeters go octaves lower. So mostly one chooses the woofer by T/S specs to fit the box desired and then rolls off the top with the crossover. Simple.

That Dave still uses aperiodic designs is understandable, because as a full-range advocate, he's still more concerned with the top end.

Augspurger's TLwrx might be a better choice than WinISD, as it allows you to enter more parameters for the damping which can be used to model losses. However, there's no data available, so you'd have to do a lot of measurements to know what values to enter. You'd also be working with a "lump sum" of cabinet stuffing and port attenuation.

IG81 covered the gist of the purpose of aperiodic design (unless Dave knows better). You basically make the box/port too small, usually to avoid over-excursion, then damp the resulting bass spike with a resistive port.

[planet10]

Originally Posted by Keriwena

I
That Dave still uses aperiodic designs is understandable, because as a full-range advocate, he's still more concerned with the top end.

huh?

Augspurger's TLwrx

Is very dated. MJK has been continually upergrading his sw and provides support... much better bet. If someone provided Martin with the test data for high densities of various stuffing, this software should be quite capable of modeling aperiodic boxes.

You basically make the box/port too small, usually to avoid over-excursion, then damp the resulting bass spike with a resistive port.

That is one use. There are others.

dave

[Nanook]

Consider an aperiodic enclosure as a mass coupled BR. You can do this a bunch of different ways.

• Build a BR using a typical vent, but stuff it full of straws that are held in a bunch with elastic bands. This has worked wonders for small, inexpensive BR speakers that are often part of "executive" micro stereo set-ups in my experience.You can also try open cell foam, an old pair of stockings, an old pair of socks, "Scotchbrite", or Dacron/Accoustistuff/treated pure wool or whatever. There can be a fine line between too much stuffing and not enough.
• Dynaudio used to sell the "variovent". Just follow their instructions and you should have success (this becomes a "leaky" sealed box). I am unsure if Dynaudio still has them available.
• Look at the old Dynaco A-25 loudspeakers as an example and consider emulating it. HiFi World used to have an updated kit available (WD25?), but they also had the design articles on their website that can provide some insight into aperiodic enclosure driver requirements and design.

To me, rather than the use of a "too small" box, the aperiodic enclosure's real benefit is the reduction of the impedance peak's magnitude. The driver is then capable of much more output at or near the resonant frequency. This point seems to be lost in the rest of the "arguments" for and against them.Thus, even if you don't make a "too small" box, or a "too big" vent what you end up with is an enclosure capable of a more balanced sound, with a more benign load presented to the power amplifier to drive (and therefore a smaller amp can often do the job of a much larger one). If you consider Dave's "Fonken" and other "Onken" designs a similar result occurs (I must defer to Dave for any actual verification regarding impedance loads and output---my points are not "thoughts, but I have no way of providing any data).

caveat: I consider Dave a friend. I have had several of his loudspeakers in my home (whether commercial offerings or DIY versions using his designs) and have never had what I might consider a poor sounding one of the lot (4 or 5 pairs up until this point in time). However, I do not blindly accept whatever anyone says. If Dave's, or Chris' or Daniels's (2 others parts of the planet10-hifi team) suggestions go against my understanding, I go back and ensure that I am understanding their explanation(s) and if that still fails I go back to first principles and start at the beginning. I have done this with many audio products whether I was selling them in high end shops, trying to educate myself within the audio hobby or writing about them in reviews. One infamous occurrence was when I was new to selling Theta Digital years ago. They had some sort of "magic cable" that allowed for better clocking or timing between a transport and a DAC. My first day on the job I questioned the manager what it actually did and I called "BS" and told him what it most likely was. I was told to call Theta, which I did and their designer agreed that I was absolutely correct. The result was the same, but the understanding of the store manager and the rest of the staff was not. Blind acceptance is not a good thing, but I have never found any at planet10-hifi to avoid explanation or to try to baffle any regarding their products and the underlying science .

[Melo theory]

Originally Posted by Nanook

To me, rather than the use of a "too small" box, the aperiodic enclosure's real benefit is the reduction of the impedance peak's magnitude. The driver is then capable of much more output at or near the resonant frequency. This point seems to be lost in the rest of the "arguments" for and against them.Thus, even if you don't make a "too small" box, or a "too big" vent what you end up with is an enclosure capable of a more balanced sound, with a more benign load presented to the power amplifier to drive (and therefore a smaller amp can often do the job of a much larger one). If you consider Dave's "Fonken" and other "Onken" designs a similar result occurs (I must defer to Dave for any actual verification regarding impedance loads and output---my points are not "thoughts, but I have no way of providing any data).

Yes, great point of course. I'd like to add that there are a couple more great benefits for an aperiodic vent.
Less box resonance (vibration), and cancellation at bass frequencies, which give a bigger bass sound, not in amplitude but in scale......like an OB, less room interaction.
Of course the second point doesn't apply to a stuffed BR port, as that will reinforce bass at resonance.

[planet10]

Originally Posted by Nanook

To me, rather than the use of a "too small" box, the aperiodic enclosure's real benefit is the reduction of the impedance peak's magnitude. The driver is then capable of much more output at or near the resonant frequency. This point seems to be lost in the rest of the "arguments" for and against them.Thus, even if you don't make a "too small" box, or a "too big" vent what you end up with is an enclosure capable of a more balanced sound, with a more benign load presented to the power amplifier to drive (and therefore a smaller amp can often do the job of a much larger one). If you consider

An exampleof this would be the PEARL PR2 -- Bill has more practical knowledge on aperiodic designs than anyone else i know.

dave

[planet10]

Originally Posted by Nanook

Dave's "Fonken" and other "Onken" designs a similar result occurs

The vents in the miniOnkens push what is nominally a bass reflex towards an aperiodic one, but not all the way.

dave