is a bigger enclosure better?

[legendaryfrog]

today when i was watching finding nemo in my basement with my brother i got the idea of using our crawl space, which is under our projector, as my sub enclosure. The whole thing is totally insulated with the fiberglass facing out.
their is a 2 ft. opening. If i sealed the opening with MDF and mounted the driver (a titantic mkII) in the MDF would i get lower frequencies vs my 300 liter sonotube.

PS the crawl space is 1300 cubic ft

[Lothar34]

You'd need an IB capable sub for that and I don't believe the Titanics mkII is suited for IB.

Dayton has or used to have an IB sub.

[looneybomber]

Originally posted by legendaryfrog
today when i was watching finding nemo in my basement with my brother i got the idea of using our crawl space, which is under our projector, as my sub enclosure. The whole thing is totally insulated with the fiberglass facing out.
their is a 2 ft. opening. If i sealed the opening with MDF and mounted the driver (a titantic mkII) in the MDF would i get lower frequencies vs my 300 liter sonotube.

PS the crawl space is 1300 cubic ft

2ft by 2ft? If so, you might be able to get 2, 15's to fit in their diagonal, otherwise, I would not tear apart your sonosub and pull the driver out of it. You will lose a few db's above12-15hz (depending on how you're tuned) but gain a few db's in the single digits. Not worth it for me, that's what buttkickers are for.

[Ron E]

When you run IB, you essentially get a leaky sealed box with the same Q as the woofer. You will want a woofer with a Qts above 0.6 or so, IMO, as larger enclosures are lossier. If you get a couple long excursion woofers with a Q of ~0.7 or so and fit them into the opening, you could have very nice deep bass.

IF you find some high sensitivity woofers with decent excursion, you can add mass and lower their resonant frequency and increase the Q to suit the application. The sensitivity will be reduced by the added mass.

[Gibbi]

Dayton's IB woofer

http://www.partsexpress.com/pe/showd...number=295-455

[hifiger]

If you are interested in IB(Infinite Baffle) subs, i strongly advise you to check out this forum dedicated to just that:

http://ibsubwoofers.proboards51.com/

Infinite baffle subs with sufficient air dicplacement, such as 4 AV15's can reach frequencies as low as ten hz in an IB configuration. Some more ambitious projects can reach five hertz at reference levels(110db).

[Hezz]

The IB method would be ideal but you have to use a few drivers to get down low and handle the SPL's since there is no air spring behind the woofer. Still these designs when properly done offer the highest quality sound down low as they have the highest transient response of any bass system.

[hifiger]

Yep

[AndrewT]

Hi Ron,

Originally posted by Ron E
.......IF you find some high sensitivity woofers with decent excursion, you can add mass and lower their resonant frequency and increase the Q to suit the application. The sensitivity will be reduced by the added mass.

I want to lower the bass turn-over frequency and the mass loading of the cone combined with re-tuning the vent (longer) would get me nearer.

But, does the Q also change when the cone mass is increased?

What are the parameters & formulae that depend on moving mass?

[hooha]

Originally posted by Ron E
When you run IB, you essentially get a leaky sealed box with the same Q as the woofer. You will want a woofer with a Qts above 0.6 or so, IMO, as larger enclosures are lossier. If you get a couple long excursion woofers with a Q of ~0.7 or so and fit them into the opening, you could have very nice deep bass.

Hi Ron,

Folks over at 'the Cult' seem to be dispelling the Qt issue as unecessary, as many are going with normal Q drivers in their IB's. Excursion and power handling are key here. Surprisingly, many have sucessfully used my MJ-18's in IB configs.

Originally posted by AndrewT
Hi Ron,I want to lower the bass turn-over frequency and the mass loading of the cone combined with re-tuning the vent (longer) would get me nearer.

But, does the Q also change when the cone mass is increased?

What are the parameters & formulae that depend on moving mass?

Hi Andrew,

Yes, Qts does rise when you add mass - an available formula I am unsure about. However, to give you an idea of added mass to a cone, here are some quick measurements on a 12" subwoofer:

Before Added Mass:
Fs - 23.3Hz
Qts - 0.26
Qes - 0.28
Qms - 3.01

With 133g Added Mass:
Fs - 15.9Hz
Qts - 0.36
Qes - 0..41
Qms - 3.34

Mark