sub woofer box problems, need info

[minuteman]

we currently tried making a band pass box to put into back of a jeep
wrangler, with the back seat still in the vehicle, however it dosent
function as well as i had hoped. the boxes sound is weak, and we dont
know what it is due to. we are running 2 type e alpines, 750 watts
each and a 1200watt ultimate amp. the box itself has to be the
problem, beacuse the amps were being used in another box sucessfuly,
with subs. the cubic feet is meant for two 10ns, so we have adaquate
space. we need your input on what we should do to improve performance,
and or make the sound more powerfull. thanks for all future imput.

[KU40[_29_]]

what are the specs on the box you built?


--
KU40

[Matt Ion]

ruens wrote:
> On Wed, 13 Jun 2007 17:40:47 -0700, minuteman >
> wrote:
>
>> we currently tried making a band pass box to put into back of a jeep
>> wrangler, with the back seat still in the vehicle, however it dosent
>> function as well as i had hoped. the boxes sound is weak, and we dont
>> know what it is due to. we are running 2 type e alpines, 750 watts
>> each and a 1200watt ultimate amp. the box itself has to be the
>> problem, beacuse the amps were being used in another box sucessfuly,
>> with subs. the cubic feet is meant for two 10ns, so we have adaquate
>> space. we need your input on what we should do to improve performance,
>> and or make the sound more powerfull. thanks for all future imput.
>
> A little more info would be helpful such as available space you have
> to work with, and speaker size.

More to the point: what exact models of speakers, their T/S parameters,
and how you've got them wired, would help.

Also be useful to know how the box is designed, and what it's
constructed of - 1/2" plywood < 1" MDF.

[GregS]

In article om>, minuteman > wrote:
>we currently tried making a band pass box to put into back of a jeep
>wrangler, with the back seat still in the vehicle, however it dosent
>function as well as i had hoped. the boxes sound is weak, and we dont
>know what it is due to. we are running 2 type e alpines, 750 watts
>each and a 1200watt ultimate amp. the box itself has to be the
>problem, beacuse the amps were being used in another box sucessfuly,
>with subs. the cubic feet is meant for two 10ns, so we have adaquate
>space. we need your input on what we should do to improve performance,
>and or make the sound more powerfull. thanks for all future imput.

When I make a BP box, I use the calculations to predict SPL and filtering. The only
way to verify the box is run a sweep test outside the vehicle, best
outside in the yard. By comparing actual to predicted, this will tell if it
working as it was predicted.

greg

[s3sqguy[_21_]]

You have to use software or factory specs to make a bandpass box. I did
one before I could get it a long time ago and it worked nice, it was
tuned low and I hooked a small house stereo to my PC with some nice
bookshelf speakers....it sounded great, could play CD off the PC, and
could play radio too. It went loud for PC speakers and thumped. It was
about 30 or 35W/ch stereo. All that you did was hooked it up parallel
with no crossover, that is why I made one with a DVC 10".

Anyway, later I ran out of room and made a smaller 8" one because the
10" made more than enough bass. It didn't work! I moved my stuff later
and bought a small speaker set with sub for the PC. Ran the 10 in a car
briefly but it didn't go loud enough for that and was tuned too low. One
day I plugged both into winISD and the 10" was right on for what I
wanted, but the 8"....it was all wrong. Turned out it was an IB speaker
and had a nasty response curve; it only hit in two different Hz and
nothing between. Even changing the box would not fix it. Also the box
and port has to be real close to right or it screws it up. I did use
the 10 box with a bought 10 BP (both single driver) and it worked real
nice, mine was low and that one was higher. Problem was it filled my
whole trunk.


--
s3sqguy

[GregS]

In article >, s3sqguy > wrote:
>
>You have to use software or factory specs to make a bandpass box. I did
>one before I could get it a long time ago and it worked nice, it was
>tuned low and I hooked a small house stereo to my PC with some nice
>bookshelf speakers....it sounded great, could play CD off the PC, and
>could play radio too. It went loud for PC speakers and thumped. It was
>about 30 or 35W/ch stereo. All that you did was hooked it up parallel
>with no crossover, that is why I made one with a DVC 10".
>
>Anyway, later I ran out of room and made a smaller 8" one because the
>10" made more than enough bass. It didn't work! I moved my stuff later
>and bought a small speaker set with sub for the PC. Ran the 10 in a car
>briefly but it didn't go loud enough for that and was tuned too low. One
>day I plugged both into winISD and the 10" was right on for what I
>wanted, but the 8"....it was all wrong. Turned out it was an IB speaker
>and had a nasty response curve; it only hit in two different Hz and
>nothing between. Even changing the box would not fix it. Also the box
>and port has to be real close to right or it screws it up. I did use
>the 10 box with a bought 10 BP (both single driver) and it worked real
>nice, mine was low and that one was higher. Problem was it filled my
>whole trunk.

I think you need software, and driver specs. Actually you don't need software, as
I did before software was available, use longhand. By using bandpass, you can
modify elements to make it fit in your application, such as Q, S, SPL, and
bandwith. Sometimes it will not work since there are limitations on those
and the driver.

grge

[D.Kreft]

On Jun 19, 10:08 am, s3sqguy <s3sqguy.2sf...@no-
mx.forum.carstereos.org> wrote:

> Turned out it was an IB speaker
> and had a nasty response curve; it only hit in two different Hz and
> nothing between. Even changing the box would not fix it.

Yep, not all drivers are suitable for bandpass enclosures.

On a somewhat related note, here's how modifying the various
components of a single-reflex bandpass enclosure will alter you
response curve (this is all from ancient memory...let's see if I
remember correctly):

* Sealed chamber: controls high-pass filter. The larger this
chamber
is, the lower your HP f3 will be and the lower the mechanical
power
handling will be for the enclosure. Conversely, shrinking this
chamber will increase your HP f3 and increase mechanical power
handling.

* Ported chamber: controls the overall efficiency and bandwidth of
the system. Increasing the size of this chamber (while keeping
the
tuning frequency constant) will make for a narrower passband with
a smoother frequency response, though if you get too narrow it'll
look like Mt. Fuji--a single peak in the middle of the band.
Shrinking this chamber (again, keeping the fb constant) will
result
in a wider passband and the double-peak response curve you
described.

* The port: controls the center point of the passband. Increasing
the
tuned frequency will shift the curve to the right (up the
audio spectrum) and decreasing the fb will shift the curve to the
left.

It's important to note that designing a SRBP's is a lot like flying an
old-skool helicopter. In an older helicopter (one without all the
modern computers), changing one control (e.g. speed of the rotor)
requires changes to the others to keep you from losing control of the
craft. The same is true in a SRBP--changing the port, for instance,
will not only change the high pass f3, but it'll also change the shape
of the response curve, so it's not like you can just simply tune lower
and get the same response curve just at lower registers.

If you attempt to design a bandpass enclosure sans computer software,
you are either really macho or really naive...I'm not sure which. I
surely would never want to try it without good modeling software!

-dan