Bandpass enclosure for JBL GT4-12

[Xmax]

Hey Gurus,

I would like you opinion on the same as I am confused. I am planning to put in a subwoofer in a Lancer. I already have a JBL GT4-12 with me and I find that the JBL GT4-12 has got a Qts factor of .43 which is quite ok for to create a fourth order band pass box with a steady response curve between 37 and 90 Hz. But my confusion is how this thing is going to behave in the trunk. I am looking for clean deep bass as with just one Gt4-12 I am not looking much into the SPL.

[Sam Kapasi]

The GT4-12 does perform beautifully in a 4th order BP. A good choice.
With adequate power, it will deliver deep bass in the trunk.
It will also have an excellent transient response, delivering some pretty accurate bass.
Make sure you have lots of power.

Here you go. Enjoy.

[jkdas]

Thats gonna be a BIG box.

And this is why I hate custom boxes. Too much specs to take care-of .

Sam, how much RMS would he need?

[low_bass_makker]

With which amp are you gonna run this sub ?

[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

Not sure if this is a good design since I am not sure about the Group delay and the vent air velocity.

Could you help me with the group delay and vent velocity factors as well?

[Xmax]

Originally Posted by low_bass_makker

With which amp are you gonna run this sub ?

Hey LBM,

I am planning on the JBL GTO301.1. I was told it would cost me around 9000 Rs. Can you help me with choices within the price range. I would love it to be a Class D Amp.

[Ajaybiz]

Thats right grey price for GTO 301.1 also have a look at GTO1260BR its 60th annirversary edition available for 5500.May be you can push off your GT4-12.

[Xmax]

Originally Posted by Ajaybiz

Thats right grey price for GTO 301.1 also have a look at GTO1260BR its 60th annirversary edition available for 5500.May be you can push off your GT4-12.

Is that a bandpass enclosure? I guess it is a bass reflex, aka vented. Was the car you installed these, a hatchback or a sedan ? Any idea how much a GTO1204BP would cost ?

[Ajaybiz]

Its Bass Reflex but low frequency responce is too good just check its features.
Mine is Hatchback(Swift) still that woofer and amp is waiting for suitable day to get loaded in my car(no time man) :(.

[Xmax]

Originally Posted by Ajaybiz

Its Bass Reflex but low frequency responce is too good just check its features.
Mine is Hatchback(Swift) still that woofer and amp is waiting for suitable day to get loaded in my car(no time man) :(.

IMHO ported and even bandpass enclosures for that matter, give good results in hatchbacks... hope we get to see the installation pictures soon

[low_bass_makker]

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

Not sure if this is a good design since I am not sure about the Group delay and the vent air velocity.

Could you help me with the group delay and vent velocity factors as well?

How did you calculate the sizes ??

[determinus]

@Sam: Why do you have polyfill on the port side of the design? What's the need to increase the virtual volume there?

@Xmax: 301.1 is a class AB. Under 10k I think Pioneer D510 (500x1@2) is the only class D mono.

[Xmax]

Originally Posted by low_bass_makker

How did you calculate the sizes ??

I did it in a trial and error method using Bass Box pro. As i told earlier I have not done one before and therefore its all theory for me.

It would be great if i could get some info on how these measurements might behave in the actual environment based on your experience.

My requirement is to achieve the best possible flat response between 35Hz and 90Hz with minimal vent air velocity. I am ok with high group delays if they are beyond my required response curve.

[Xmax]

Thanks for the update determinus.... I find the pioneer model to be outdated. Is it still available for purchase ?

[hydrashok]

Originally Posted by determinus

@Sam: Why do you have polyfill on the port side of the design? What's the need to increase the virtual volume there?

I was wondering the same. Esp. With 2 cu.ft. In the Ported section.

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