Speakers that have an "Aperiodic" design

So many different types. The ScanSpeak are the ones that are so similar to Dynaco. I'm going to try and find a pair and audition them. wow

I also found.
----------------------------------------
1. Dynaco (60's-70's)
2. Rogers Reference Monitor System (1978)
3. Griffin loudspeakers (1970's)
4. Wharfedale Jade 5 (current)
5. Omega loudspeakers (current)
6. ScanDyna (1970's)
7. some B&O designs (1970's)
8. ScanSpeak (1970's)
9. some Philips designs (1970's)
 
Is this one? (Scroll down.)

http://www.troelsgravesen.dk/JBL_L100_08.htm

May 2014: The Variovent is out of production but you can still get the same thing from using a conventional port and stuff it lightly with acoustilux. I suggest a 68 x 200 mm port (Jantzen Audio). Cut it to 10 cm length. Now, the question is how much acoustilux should be added? I suggest for a start rolling a 10 x 20 cm piece of 30 mm acoustilux at insert it into the port. If you can do an impedance plot you add damping material until you get the same impedance profile as can be seen below. If you cannot perform measurements, you have to tune by ear. No damping will make a boomy bass peaking 4 dB at 63 Hz from a 65 litre cabinet and Fb = 30 Hz. Stuffing the port really hard (closed box) will reduce the bump by 2 dB. The full length - non-stuffed - port (20 cm) will make a Fb = 22 Hz. Try it out.

The Variovent consists of two grilles with some damping material stuck in between. Simple as that. The diameter, amount of damping material and the compression of the material determines the air flow properties = acoustic resistance. The late Gilbert Briggs (Wharfedale) made slits in the rear panel and added damping material over the slits. Works the same and costs nothing. But you have to be able to follow the impedance of the system to tune the amount of damping material needed.

The Variovent is a device sometimes causing much debate. What is an acoustic vent? Well, an acoustic vent allows some ventilation at low frequences and virtually none at higher frequences. So what's that supposed to be good for? Neville Thiele studied the Variovent in detail and concluded it didn't offer any advantage over a properly designed vented systems. The general advice on the use of acoustic vents is simple: Try it! Which offers little comfort to those addicted to math. But box calculation based on Thiele/Small data really only apply for speakers with a Qt = 0.35, which only counts for very few drivers. Based on experience we use speakers with high Qt in cabs too small and drivers with low Qt in cabs too large compared to strict box simulation.
 

Yup, that is a aperiodic design, it doesn't use as much stuffing as a lot of other designs. (that site is full of completely awesome projects).

Another way of making a flow resistor is to sandwich some coffee filters between two pieces of metal mesh, where the holes are lined up.
More layers of coffee filter = higher air resistance, making it easier to fine tune.
 
So many different types. The ScanSpeak are the ones that are so similar to Dynaco. I'm going to try and find a pair and audition them. wow

I also found.
----------------------------------------
1. Dynaco (60's-70's)
2. Rogers Reference Monitor System (1978)
3. Griffin loudspeakers (1970's)
4. Wharfedale Jade 5 (current)
5. Omega loudspeakers (current)
6. ScanDyna (1970's)
7. some B&O designs (1970's)
8. ScanSpeak (1970's)
9. some Philips designs (1970's)

I have 2 Wharfedale and 2 TDL models to add.

I own the Wharfedale aperiodic speakers from the early 2000's era:

"Wharfedale Transmission Line MT-138" and MT-128 models. They are NOT TL enclosure, but are aperiodic instead. The 138 has a pair of 7" Wharfedale 1772 woofer and the 128 has a single woofer.

The enclosures look identical to the TDL G20 and G30 models with same external dimensions. But the TDL woofers and tweeter are different.

http://www.imf-electronics.com/Home/tdl

I use one pair of stock 138 for subwoofer in my main audio room, electronically crossover to a pair of NHT Super One for the high end. The 3rd 138 was repaired with 2 Peerless CSC 850460 7" woofers and used as my full range center speaker.

The pair of 128 are used as full range in the family roon TV setup.

I like the non-boomy bass of the aperiodic enclosures. They go quite deep for the enclosure size and have excellent transient response.
 
I once owned the Audio Concepts G-3 tower speaker. It was an aperiodic design and sounded very good.
 
I think the resistive line tunnel in the Fried Q, R, A, and so on was a close relative of the aperiodic enclosure.
 
Why the need for aperiodic?
Sure the Dynas work well.
But a good sounding speaker design is neither limited to nor dependent on Aperiodic loadings
Lotsa ways to the same result.
 
Point was that the Dyna's worked reasonably well. Owned a pair 'back then'.
Just pointing out that if locating a Vintage aperiodic is problematic.. there are other speaker designs that are least the sonic equal.
My 2 c
 
Bass loading affects loudspeaker sound

Why the need for aperiodic?
Sure the Dynas work well.
But a good sounding speaker design is neither limited to nor dependent on Aperiodic loadings
Lotsa ways to the same result.

The aperiodic bass loading is a compromised design to get non-resonant bass at moderate enclosure size.

The majority of today's loudspeaker are in a bass reflex enclosure which can go fairly deep with a smallish box and has good efficiency. But the twin impedance peaks in such an enclosure is impossible to completely damped out. It impairs the transient response of the bass and give it a "ringing" type character. The bass sounds "lossy" or "boomy" to some listeners, but good, deep bass to others.

The aperiodic enclosure gives the kind of tight (rapid transient and decay) bass some listeners consider "more accurate" in a moderate sized box.

It is a personal choice that which type of bass one prefers. But they are very different to listen to.

The design of aperiodic enclosure was first published by Ted (E. J.) Jordan in the Feburary 1956 issue of Wireless World, pp 75-79. Interestingly, Ted Jordan called it a "absorbing Labyrinth" enclosure and named it "Axiom". I am not sure when the term aperiodic came into being. It could mean "non-resonant" or not tuned to a single frequency. And this type of enclosure was made famous to the US audiophile by the Dynaco A25 speaker. The attached image is the last page from Jordan's Wireless article. The picture showed the different impedance curves and how his Axiom (aperiodic) design differs from others. In the last 2 paragraphs, Jordan described the benefits of his aperiodic design. This work was done around the time when Edgar Villchur invented the air suspension enclosure. The acoustic suspension design seemed to fall out of favor for deep bass design because the woofer is expensive to make. The closed box design is still the favorite in bookshelf enclosure for many loudspeaker designers due to the bass transient performance mentioned above.
 

Attachments

  • Ted-Jordan-Aperiodic-Design_Page_5.jpg
    Ted-Jordan-Aperiodic-Design_Page_5.jpg
    153.9 KB · Views: 27
Last edited:
The Dynaco aperiodic design uses fiberglass stuffing but many others use wool or foam in aperiodic designs..
The Madisound Dynaudio kits used virgin wool in their aperiodic designs.
I still have the literature from one of their old catalogs from the early 90's.

The link below has a review of the Fried model Q4 which is an aperiodic design.
There is also an explanation of the aperiodic design on pages 20-21.

http://www.theaudiocritic.com/back_issues/The_Audio_Critic_17_r.pdf
 
The Dynaco aperiodic design uses fiberglass stuffing but many others use wool or foam in aperiodic designs..
The Madisound Dynaudio kits used virgin wool in their aperiodic designs.
I still have the literature from one of their old catalogs from the early 90's.

I found the long fiber wool used by A. R. Bailey in his transmission line enclosure gave the best result stuffing the aperiodic enclosure. Fiber Glass comes in as second. The Polyfill batting is pretty useless.

The link below has a review of the Fried model Q4 which is an aperiodic design. There is also an explanation of the aperiodic design on pages 20-21.

http://www.theaudiocritic.com/back_issues/The_Audio_Critic_17_r.pdf

It is interesting that the article did not mention Ted (E. J.) Jordan who was credited with inventing the aperiodic enclosure.

http://www.ejjordan.co.uk/ted/
 
North Creek Audio. supposedly improved upon the aperiodic design and changed the letters around with the (MAPD) Multi-Chambered Aperiod Progessive Damping cabinet.
http://www.northcreekmusic.com/MAPD1.htm
I built a pair of full-rangers using the Northcreek MAPD math. The design was used to let the small full-rangers dig lower without the driver running out of steam or over-excursion. Unfortunately, the speakers were used by my, then, teenage Son and he drove them to extinction.
Over all, I thought the design returned a good, balanced sound.

IMG_0001-3-1.jpg


This small enclosure has a driver chamber and a second, larger chamber. The entry from the first to the second chamber is damped by my own version of a "Variovent" with materials I had on hand. There was some tuning of the vent to produce the best overall sound. If DIY'er has a driver with a high QTC, it might be worth your while to experiment with the aperiodic design.
 
Last edited:
Back
Top Bottom