What Box for Focal 4" coaxial?

[sifis_samos]

What Box for Focal 4" coaxial?

Hello guys..I am new in here and i really apreciate all the info i can find here!..
So here is my questions..A friend gave me for free a brand new pair of 4" Focal - Access 100 CA1 http://www.sonicelectronix.com/item_11729_Focal+100+CA1.html .. that what i need to do is build a small hifi system for my worklab..so i am looking for the ideal box for these speakers.i intend to build it using plexiglass 1cm thick mainly for good looks....so can someone tell me what size the box should be for optimal acoustics?.i searched through the net but i couldnt find something specific.. any comments are welcome!

by the way, these speakers will be driven by a Chinese amp using the very well known Tripath ic's, giving about 15-20Wrms..🙂

 

[sifis_samos]

on the poduct datasheet it suggests a 30Liters sealed enclosure!!!..isnt it too much?..my Focal Access 12" subwoofers needed 35Lts vented..

 

[Cal Weldon]

They are a car speaker. Being a 4" driver means it likely has a high Qts to give it some bass sound in the door or back shelf. A high Q often means a high Vas, unlike that of a longthrow woofer.

 

[pblossom]

Specifications

Specifications are desirable to design a box for optimum bass. After a short google search, I found this link for specs: http://www.focalaustralia.com.au/pdfs/acc_100CA1.pdf

 

[BHTX]

IB is best. Don't put it in an enclosure, unless you have no other choice. It'll be under damped when you do. It could be much worse though.

 

[sifis_samos]

well acording to the specifications a 30Lt box is suitable but its way too big from what i am thinking..i was thinking something around 4-5lts. 🙁

 

[BHTX]

well acording to the specifications a 30Lt box is suitable but its way too big from what i am thinking

That's because it was designed to be used in an infinite baffle (IB) application, which is the most common configuration for midbass/midrange loudspeakers in automobiles. Qts for that driver = .632, which indicates that infinite baffle is pretty much mandatory IF a flat response and reasonable damping characteristics are desired.

IB = an infinite number of liters. 😉

 

[sifis_samos]

then these are useless speakers for me...damn..anyway thanks for your help guys!

 

[pblossom]

You can certainly put them in a 4 or 5 liter closed box. Two things will happen, the frequency response in the low end may have a peak, and the system won't go as low as it might otherwise. In a 5 liter box, according to my software, the -3db point is about 100Hz.

 

[sifis_samos]

well if it can go down to 90-100Hz i believe it will be ok...i dont expect something extraodinary...that what i want though is great mid bass and midrange performance...i like Metal, folclore and rock music so i think it will be ok..i will use 10mm plexiglass and when i am done i will tell u my impressions!..😀

 

[bjorno]

...well if it can go down to 90-100Hz i believe it will be ok...

Hi sifis samos,

If you try using your proposed driver in a 5 L ported box (See picture 1(3)) you reach about 70 Hz f(-3dB) but the will be peaking with a system Q about 1.4. See picture 2(3).

This Q value can be lowered down a bit by using the method of Qm damping (See picture 3(3), as the driver Qm can easily be pushed down from 9.05 to about 2 or even lower.

A Qm of 2 virtually results in a more suitable(usable) Qts value of 0.51 compared to the original Qts of 0.632.

The box system Q will then be lowered to about 1.26 (Qm=2) and the f-3dB point at about 75 Hz.

More reading concerning Qm damping at:

http://www.diyaudio.com/forums/showthread.php?threadid=104828

b

1(3)

 

[bjorno]

2(3)

 

[bjorno]

3(3)

 

[sifis_samos]

Now that is interesting...but isnt sensitivity harmed by doing Qm damping?...i believe that by doing as you said it will be more than enough.. thank you my friend!.if you come to Samos Island ever i will by you a Beer! 😀

 

[Andersonix]

Perhaps you can mount them in a 6-8 inch dia acrylic sphere intended as a lamp diffuser?

 

[sifis_samos]

i will order this monday trhe boxes made of 1cm glass!!..he he he..even the tube for the bass reflex will be from clear Plexiglass...when i am done i will upload some photos!