Aperiodic boxes for Ciare CH250

[foniton]

Hi everybody.
I have a pair of Ciare CH 250 (single magnet) drivers from an old open-baffle project...

Impedance: 4 Ohms.
Sensivity (1w/1mt): 96 db.
Qts: 1,36.
Vas: 52 l.
Xmax: 0,5 mm.

and I think that would be interesting to make a pair of aperiodic boxes with ScanSpeak´s 130 mm flow resistors...
http://www.tymphany.com/products_ScanSpeak.html
I don´t have any experience with aperiodic boxes, so any advice is very welcome.

My doubts are:
-dimensions (a big floor-stander is prefered).
-number and best location of flow resistors.
-box material (normally I use finland birch but maybe MDF is better for this “hot” driver).
-best type and location of stuffing material.
...so, at this point, I need a lot of help.

Power-amp: EL84 single push-pull, around 10 Watts.

Many thanks.

[Nanook]

look here..

No first hand experience here, but I do own a set of original Dynacos. You can also make your own restrictive vents, see the link.
Basically an aperiodic acts like a "leaky" sealed box. The real benefit is the peak impedence and smoothed, and reduced.

Seas sells a driver suitable. Anthing that will work in a vented enclosure (Qts approc .4)

look at World Audio Designs, and not the price!

You will need to be able to measure impedence of the loudspeaker, to adjust the resistive layer in the "vent". Looking further, I am pretty sure a variovent or resistive port is not suitable with the driver you have .

Here's a floorstanding version

here's the specs

that's about all I can add.

[planet10]

With the Qts on that, the receipe boils down to:

1/ figure out how big a box you can live with -- if one dimension is a fair bit longer than the others that is good

2/ mount the drive at one end and start playing with ports and port resistance at the other end. use GM's click test, or use an impedance jig to tune until you have flatest impedance.

3/ making your own "resistive vents" is much more versatile than buying the scan vents.

dave

[lovechild]

Hi

here's an example of another way to build an aperiodic enclosure.
It's for an Onmes Audio L8 data sheet , in ca. 40 Liter and 120 holes (8mm dia.) in the back.



The old Saba tuberadios with the famous greencones in them, where build like that.

best,
LC

[lovechild]

Here is an enclosure modelled with MJKs ported box worksheets.

About 85 Liter with stuffed port (Density 0.99lb. ft^3) - see yourselfs - this way, Martin once explained, aperiodics can be modelled with his worksheets.

As you might see, the port still adds some impact in the LF and the woofer displacement is reduced, but the response is relatively flat and the impedanz peak around zero. I think the most critical point is to find the right material and amount of stuffing for the port.

BTW, I own a pair of Dynaco A25 and I kind of like the bass they offer - although I have to say, it's a shame to use such a great woofer in a way too small enclosure and give away all the deep bass it could deliver. For high Q drivers, like the ciare, aperiodic loading seams a good thing though.

ciare.pdf

best, LC

[foniton]

Hi everybody.
Many thanks, Nanook and Dave, for your comments and suggestions.

According to "Audionutz on AP Enclosures" article (thanks for the link) it seems that drivers with Qts higher than 0,45 aren´t good for aperiodic boxes.
The idea of aperiodic boxes came to my mind after reading about the Omega A8´s on ...
http://www.6moons.com/audioreviews/redwine3/system.html
Given that Visaton B200´s Qts is on the high side (0,75), I thought It would be a good idea trying something similar with my Ciares. But what is good for a certain driver could be less than optimal for another.
Equally, many things that couldn´t work (on paper) are offering surprisingly good results.

What attracts me of aperiodic boxes resides in their potential for clean bass, with a soft decay in response, and that you don´t need a lot of internal stuffing (with the consequent loss of life and transparency).

Please, any information is very welcome.
Best regards.

P.D: Dave, sorry for my poor understanding of english. What does "GM's click test" and "impedance jig" means?

[planet10]

Originally posted by foniton
it seems that drivers with Qts higher than 0,45 aren´t good for aperiodic boxes.

Maybe not ideal, but if you have to put a driver that would prefer to be in an open baffle into a box, aperiodic is your best bet. I did a quite nice speaker, with a driver with Q>1. I took a set of old boxes (close to floorstander height), slapped some scrap MDF to the front, mounted the driver on the side, drilled a bunch of holes (simillar to the picture above) and tuned the cabinet by ear by adjusting the amount & density of the foam i placed over the holes on the inside. My mom enjoyed these for quite a while, before i found something littlier that would squeeze in beside the TV.

P.D: Dave, sorry for my poor understanding of english. What does "GM's click test" and "impedance jig" means?

I'm hoping GM comes by and describes clik test....

Impedance jig, is kit to measure the impedance of your speaker.

dave

[Nanook]

Here...

I think this may help answer the need for more bass....

[Henkjan]

with such a high Qt you might also want to apply a series condensator to smoothen the bass frequency curve

[felixx]

So...how can we calculate that capacitor?