Bandpass enclosure for JBL GT4-12

low_bass_makker · 27th January 2008, 13:31

The simulation softwares are good to play with. Help a lots of time but the results can be very weird when wrong parameters are used.

Any particular reason for a bandpass enclosure ? why not ported.

Xmax · 28th January 2008, 09:43

The addition of polyfill in the port side of the design helps in attenuating the vent, as the ported chamber is responsible for the upper F3 value. The downside is that port length should be increased compared to a no fill which may become a constrain when the ported chamber has a reduced volume.

Xmax · 28th January 2008, 14:14

Quote:

Originally Posted by low_bass_makker

The simulation softwares are good to play with. Help a lots of time but the results can be very weird when wrong parameters are used.

Any particular reason for a bandpass enclosure ? why not ported.

I will try to justify my choice here

Main reason being the Gt4-12 driver parameters are not great for a proted enclosure as per what i understand. It can either do well with a sealed or a single tuned bandpass.
The driver noises would not be thrown out due to enclosure's upper f3 which, an active or passive LPF will not be able to deliver.
The acoustic boom factor or in-car dynamics at 50 hz crossfades well with the rollout.

low_bass_makker · 28th January 2008, 17:32

Quote:

Originally Posted by Xmax

I will try to justify my choice here

Main reason being the Gt4-12 driver parameters are not great for a proted enclosure as per what i understand. It can either do well with a sealed or a single tuned bandpass.
The driver noises would not be thrown out due to enclosure's upper f3 which, an active or passive LPF will not be able to deliver.
The acoustic boom factor or in-car dynamics at 50 hz crossfades well with the rollout.

The EBP of the sub is 53.8 so it is close to 50 but greater than 50. which means ported. Also the qts is .429 which is again at the margin point.

In which car are you going to use the sub. Hatch or sedan.

The best roll out is for the sealed enclosure. But then again there are compromise.

Xmax · 28th January 2008, 18:52

i am planning this for a sedan - lancer's boot to be precise.

JPL · 28th January 2008, 20:58

Quote:

Originally Posted by Xmax

i am planning this for a sedan - lancer's boot to be precise.

Xmax can we all have the pleasure of an intro?

Xmax · 28th January 2008, 22:22

Quote:

Originally Posted by JPL

Xmax can we all have the pleasure of an intro?

JPL bhai, I tried one at the introduce yourself thread and finally had my share from our jkdas .

http://www.team-bhp.com/forum/introd...91-hi-all.html

low_bass_makker · 28th January 2008, 22:30

Quote:

Originally Posted by Xmax

i am planning this for a sedan - lancer's boot to be precise.

Hate to say that the sub will get a bit low in the sedan when compared to a hatch.

Bass&Trouble · 29th January 2008, 00:27

Hi Vimal Paul! Welcome to the ICE section!

For someone not professionally into audio, you have a good hold on audio concepts. It will be great to have you around here, and read your contributions.

JPL · 29th January 2008, 10:55

Quote:

Originally Posted by Xmax

JPL bhai, I tried one at the introduce yourself thread and finally had my share from our jkdas .

http://www.team-bhp.com/forum/introd...91-hi-all.html

Sorry for that man..thanks for the link though.

Quote:

Originally Posted by Bass&Trouble

Hi Vimal Paul! Welcome to the ICE section!

For someone not professionally into audio, you have a good hold on audio concepts. It will be great to have you around here, and read your contributions.

I agree, welcome again.

Xmax · 29th January 2008, 14:05

Thanks B&T. Its the simplicity you gurus maintain in this forum, that makes newbies participate without hesitation. The ICE section especially has always been a great place for learning things in its best possible. Keep up the good work.

grizzly · 25th February 2008, 10:17

Quote:

Originally Posted by Xmax

Hi Sam,

Thanks for the design. Just to clarify, do you really need it that big? Because I am able to achieve an f3 low at 30 and f3 high at around 90 (in theory) with a chamber lesser in size.

V rear 27.98 L
V front 24.5 L
Port 3.5 in
Length 8 in

Hey Gurus, What say? After alll that we have dicussed so far on this thread, Will it be worthwhile sticking to these for the enclosure parameters for my GT4-12 ?

low_bass_makker · 26th February 2008, 01:27

you can try the ported box as suggested earlier. I will be easy to build when compared to the bandpass.

navin · 26th February 2008, 10:45

Quote:

Originally Posted by low_bass_makker

Hate to say that the sub will get a bit low in the sedan when compared to a hatch.

the extra efficiency of a band pass box might help over come this.

Quote:

Originally Posted by hydrashok

Is it intended more to reduce the velocity of the air exiting the port, and so to reduce port whistle?

not really it is to ensure that none of the midbass get out. a 6" dia port will not have much air noise (even if it is 10" long).

I dont have the T/S of the woofer but with a Qts or about 0.4 it is ok for band pass.

LBM, remember not to take the published T/S parameters as the gospel. There are often variations that are significant. With an EBP of 50 the woofer can swing both ways.

grizzly · 31st March 2008, 15:52

Quote:

Originally Posted by low_bass_makker

you can try the ported box as suggested earlier. I will be easy to build when compared to the bandpass.

Thnx for reiterating the same.But LBM; what will be the specs for the Ported one...can't really figure that out!!

27th January 2008, 13:31	#16
low_bass_makker Senior - BHPian Join Date: Mar 2006 Location: Faridabad Posts: 6,815 Thanked: 305 Times View My Garage	The simulation softwares are good to play with. Help a lots of time but the results can be very weird when wrong parameters are used. Any particular reason for a bandpass enclosure ? why not ported.
	() Thanks

28th January 2008, 09:43	#17
Xmax BHPian Join Date: Dec 2007 Location: Bangalore Posts: 29 Thanked: 0 Times	The addition of polyfill in the port side of the design helps in attenuating the vent, as the ported chamber is responsible for the upper F3 value. The downside is that port length should be increased compared to a no fill which may become a constrain when the ported chamber has a reduced volume.
	() Thanks

28th January 2008, 18:52	#20
Xmax BHPian Join Date: Dec 2007 Location: Bangalore Posts: 29 Thanked: 0 Times	i am planning this for a sedan - lancer's boot to be precise.
	() Thanks

29th January 2008, 00:27	#24
Bass&Trouble Senior - BHPian Join Date: Mar 2006 Location: Bombay Posts: 2,756 Thanked: 136 Times	Hi Vimal Paul! Welcome to the ICE section! For someone not professionally into audio, you have a good hold on audio concepts. It will be great to have you around here, and read your contributions.
	() Thanks

29th January 2008, 14:05	#26
Xmax BHPian Join Date: Dec 2007 Location: Bangalore Posts: 29 Thanked: 0 Times	Thanks B&T. Its the simplicity you gurus maintain in this forum, that makes newbies participate without hesitation. The ICE section especially has always been a great place for learning things in its best possible. Keep up the good work.
	() Thanks

26th February 2008, 01:27	#28
low_bass_makker Senior - BHPian Join Date: Mar 2006 Location: Faridabad Posts: 6,815 Thanked: 305 Times View My Garage	you can try the ported box as suggested earlier. I will be easy to build when compared to the bandpass.
	() Thanks