Aperiodic Enclousure

[Holty]

Been searching for quite awhile for speaker kits and speaker configerations and its all confusing as to which to choose. I like the idea of full range as there is no crossover to worry about. The Fostex FE206ES-R seems like a good bet but i dont really like the look of the horn enclosers. Would an Aperiodic Enclosure work with these on stands. As my room is only about 12 foot by 13 foot and 8 foot high i wont need huge amounts of bass. Thanks.

[planet10]

Any of the Fostex drivers that end in 6 really need a horn to do their best due to the low Q. At least that is the general wisdom.

Bill Perkins in his PR-2 has developed probably one of the most advanced aperiodic boxes and his bass driver measures a lot like a low Q Fostex, so i'm going to say it is possible. Bill's driver does have significantly more excursion -- that might be your limiting factor.

dave

[Phergus_25]

somethign like the austin horn could be built so it looked like big rectangle.

[lt_texan]

Holty,

If you're looking for an aperiodic kit, and since you're in the UK, why not take a look at the kit offered by World Designs

http://www.world-designs.co.uk/

I havent heard them by they seem toget some pretty good comments on their bulletin board

Dan

[ronc]

After having as my first higher end system in college that being an old Eico ST40 3 way with Dynaco A25s on the outside and an A35 in the middle i can vouch for aperiodic alingment.
The cabs are smaller and the impedance curve is flatter , all in all a very good sound. However it needs a generally higher Qts. but at the same time a strong motor as its basically a restrictive filter in a volume that is being pumped. The motor has to overcome the restriction but at the same time have enough movement to hit the low frequencies. Like everything its a balance.
My early attempts was nothing more than a volume of between .5 to .7 Vas with the opening .5 Sd and i just tuned by ear and an ohm meter with the port cover till it all balanced.


ron

[moray james]

if I recall correctly Bill used a combination of diffraction generating material that was I think cellulose based and looked like a ramdom stack of wet noodles gone dry and hard, he also had some plastic that looked like it was exploded that performed the same task of ramdomly breaking up the waves that passed through it. The primary damping material was against the commonly accepted grain as it was at the time, not long fiber material but rather short fiber material instead, kapok which is a cotton based fiber used in furniture stuffing. The combination was and is extreemly effective. I believe that the idea was to generate as much internal difraction/resistance as possible throughout the volume of the inclosure rather that just at the port as is done with the Variovent device. It is an idea that proved itself extreemly well as anyone who has ever heard Bill's speakers can attest to.
I had some very impressive results using Pearl Lite (the large particals (size of a rice crispy) as damping material and reported on same some time back. B&W published a paper on the same principal using activated charcoal. Both materials are extreemly porus. Pearl Lite is much cleaner and far less expensive than activated charcoal. Note that you do have to take precautions to prevent these materials from getting into your drivers as well as getting out of the cabinet into your air.
Using Pearl Lite in a sealed enclosure you need to isolate the drivers and simply fill the internal volume to achieve excellent results. After a near disaster with a couple of very expensive ATC bass mid units in a set of ATC SM 7 cabinets I decided that the safest way to contain the Pearl Lite damping material was to place it into a thin membrain plastic bag which is then sealed off. You can use a cheap thin guage plastic garbage bags. Place the bag into the volume of the empty cabinet, fill with Pearl Lite and seal the bag with a twist tie. A layer of poly batting between the bag and the driver will insure that there is no chance for the bag to get into any future trouble as well as eatting up any possible minor plastic flutter from ever being heard through the cone. The improvement of this method over other natural fiber or synthetic fiber or foam damping is immediately noticable. Covering box walls with natural wool felt or high density fiberglass (with a wide band width of absorption) is also usefull. In reflex cabinets you need to keep a damping free volume about the reflex vent to insure the necessary cavity resonance to activate the vent (vents need room to breath at both ends). In the general proximity of the vent you can damp the cabinet walls with felt or high densith fiberglass. Regards.

[peterbrorsson]

Hi Moray!
I fail to see what effect one gets, when Pearl Lite is in a plastic bag. I have used nylon filters with a grade of 400 micron to keep polyester "fluff" in place. It is acoustical transparent and easy to work with.

Cheers
Peter

[Holty]

Thanks for the replies and suggestions.

What i do like is the fostex206ES-R drivers and really looking for the smallest cabinet for these. The 8in driver should be plenty for my room, but which cabinet design to choose. I do like the look of these with the solid wood baffle.

http://www.cain-cain.com/abby/index.html

But i dont think the wife would like them that tall. Is there a design using this type of cabinet but with that top 2 foot or so cut off. Jim.

[lovechild]

Hi Jim,

you might want to look at Martin J. Kings ML TLs here, just look in the "Projects" section.

There's a Project for the Fostex FE-208 Sigma that, I think, could easily be addapted for your driver. Maybe you even find a nice fellow here in the forum who is willing to modell your Fostex' in a MLTL with MJKs worksheets. I would do, but my PC died recently and the software won't run on Mac...

best, LC

[planet10]

Originally posted by lovechild
the software won't run on Mac...

I have the same problem, but now have a symbiotic in the UK who can run circles around anything i'd do... am Intel mac will come soo thou. The wife just got her MacBook so i'm next for a new puter.

dave