Diy generally end up with large Enclosures. How do companies manage to design compact enclosures ??

Naveenbnc

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Hello All, im asking this question for Ported Speaker enclosures.

Lets say...... im building a 6" BS (bass reflex)
I end up making the box bigger to get as much low end extension as possible.
But branded 6" BS are very compact.

Same case with a Diy 12" subs.
We end up making a large boxes.
But branded 12" subs are very compact.

Lets forget about some high end R&D companies do, and stick to basic design fundamentals.

The question is, what driver parameters demand a bigger box?
Do the branded companies compromise on the low end extension and design small enclosures?
Or is there any trick that is totally different?

Do the companies select drivers with low Vas and low Qts to come up with compact enclosures?
(Low Qts gives higher F3, and that's a disadvantage.
(As far as I know, subject to correction)

Can you throw some light on this please ....

Thanks & Regards,
Naveen
 
basically the aim is to make the enclosure compact as far as possible.
(without compromising much on Sq or low end response)

What kind of drivers should we select for this? (I mean with respect to TS parameters)
 
Driver compliance is a important factor. If your driver compliance is low ( high stiffness of the suspension) then you may require a larger box with very low stuffing. If it's a high compliance driver ( low stiffness of suspension) then you can design a smaller box (low compliance box).
 
Driver compliance is a important factor. If your driver compliance is low ( high stiffness of the suspension) then you may require a larger box with very low stuffing. If it's a high compliance driver ( low stiffness of suspension) then you can design a smaller box (low compliance box).
Thank you Hari....
High compliance driver has an advantage of smaller enclosure. Are there any disadvantages of high compliance driver ??
 
As I understand, if the total Q of the system (driver+ enclosure) is around 0.7, we get a maximally flat responce.

So we have to choose a driver, and design a box in such a way that the overall Q will be around 0.7 (hope i am correct)
 
As I understand, if the total Q of the system (driver+ enclosure) is around 0.7, we get a maximally flat responce.

This is applicable only for sealed enclosures and the value of Qtc determines if the enclosure acts more like an infinite baffle (larger and over damped enclosure) or acoustic suspension (smaller or under damped enclosure) depending on the compliance or say the VAS of the driver.

At a Qtc of 0.707, the enclosure has optimal damping. This value is more critical for woofers and subwoofers and full rangers in sealed enclosures that need to produce bass, and not critical for midrange and tweeters.

Small enclosures:
If the Qtc goes more than 0.7, the air in the enclosure will have more spring (or say suspension) so is effectively under damped. This will make the enclosure more efficient but the roll off will become more steeper, if it too high then it will affect the frequency response close to the f/s in a bad way leading to a far steeper roll off and can also over exert the cone.
In effect it will enhance the upper bass response at the cost of losing out on lower bass.
when the Qtc crosses 1.2, then it is usually defined as a one-note-wonder.
So it is advisable to stay between 0.7 and 1 for optimum response.
Larger Enclosures:
If the Qtc starts to fall below 0.7, the air has lesser suspension or spring action to influence the cone response. So lower QTc will lead to better lower frequency response but at significant loss in efficiency. If it is too high, then you may as well not have a box.

Ideal Qtc is suggested between 0.6 and 0.9.
 
Thank you Hari....
High compliance driver has an advantage of smaller enclosure. Are there any disadvantages of high compliance driver ??
High compliance driver benefit from easy cone movement. If the cone movement is easy, you can just design a small enclosure to get the air mass inside the box to support the cone like a spring with some stuffing. The only disadvantage is to get the right stuffing balance to get the correct air mass inside the box. You need to measure the impedance curve to get the stuffing right for critical damping. Once done perfectly this will sound great.
 
There are too many variables so a simple answer is difficult. A commercial product is made with price/performance ratio in mind. Thats what good engineering helps achieve.

Then the -3db response is often not specified. Some provide -9db or -10db response which is of no use. Peak SPL capability is also not specified but power is specified and that too exaggerated. So, the user does not know what he is buying :)

On the other hand, a DIYer generally will go for textbook response.

If you want to reduce box size then tune low with passive radiators, the kind of low tuning provided by PR is just not practically possible with ports.
 
@Kannan @Hari Iyer @diyaudio

Thanks a lot for a very detailed explanation .... I am able to understand most of it.
Just out of curiosity, I already cut the material for two speakers. (8" and 5.5" BS)
I depended on software for simulation.

But understanding basic design principles is very satisfying !!!:)
 
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