Team-BHP - suggestions regarding making of subwoofer box

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Originally Posted by low_bass_makker (Post 587043)

I dont understand what you two guys trying to say. The Sub is bottoming out, But why ? how come what is the problem.
Bai ji we are trying to figure out the problem too.....May be the enc is not right or the enc is too big for that sub to handle at that power!!!
SS if the sub is coming back at a slow speed then it is a good sealed box. Like I said a very small leak will work but one can check for any major leak but playing the sub only and see that any air is coming out or not.

LBM Bai ji, I read somewhere and i mentioned it in earlier post that if sub in comming out slow then there is a leak!!Hold on i will give u the link too

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Originally Posted by kURETI (Post 587324)

before u check for airleaks check the dimension as per the specification of the sub.

Yep. Done. Dimensions ok. Angle of the rear slant also ok.

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Originally Posted by kURETI (Post 587324)

forget to check airleaks, put it on and test if the bass is tight else check for dimension or build an other enclosure with proper care.

Dont know what is the best way to check for air leaks except ripping out the carpet and then checking.

I think time is ripe for building another one.

Problem faced is that Sub bottoms out very easily even at moderate settings.

Read up on internet and found that a leaky box can do that. A friend also told be his incident when a leaky box was causing his IDQ's to bottom out easily.
Box changed and everything back to normal.

Why, Even our SPL Guru LBM's subs will bottom out if he tries to cover ports with hands. Which shouldnt happen because in a sealed enclosure, the Sub will effectively handle more power than a ported one. But a hand cannot achieve a good seal. Hence leak. And Hence Bottoming out.

What's your take Navin Ji?

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Originally Posted by ScarySkulls (Post 587569)

Why, Even our SPL Guru LBM's subs will bottom out if he tries to cover ports with hands. Which shouldnt happen because in a sealed enclosure

no covering the port with hands is not a good way to seal a box.
ask LBM to try this. stuff about 0.5lb of polyfill or even opencell foam in the port (make sure it can be removed) and see if this sub stil bottoms out. what you guys are doing is tuning the box to a very low freq and the sub acoustically decouples when driven at that freq. and bottoms out.

if your HU had a Subsonic filter you could engage that and the sub would not bottom out as easily.

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Originally Posted by ScarySkulls (Post 587569)

Why, Even our SPL Guru LBM's subs will bottom out if he tries to cover ports with hands. Which shouldnt happen because in a sealed enclosure, the Sub will effectively handle more power than a ported one. But a hand cannot achieve a good seal. Hence leak. And Hence Bottoming out.

What's your take Navin Ji?

As we are talk here a new enclousre of 15 x 15 x 12.5 inch is being made. The internal volume comes to 1.16 cuft. And after removing the woofer displacement volume which is 0.12 cuft the final volume is 1.04 cuft.

The enclosure volume is taken 1 cuft because more power handling is required as 1200 watts rms is going in to the sub.

I will try to run the sub with 1200 and 335 watts from the Steg and 700 watts rms with the alpine mrd-1005. So that I will get a fair idea how the sub handle different wattages...

Will be posting some details about the test tomorrow.

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Originally Posted by navin (Post 587534)

what is the problem you are facing? bass is not tight? can you detail the sound?

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Originally Posted by ScarySkulls (Post 587569)

Aaargh! Too many assumptions, too many conjectures, too many ideas in the expression ...
* @scaryskulls has not described the symptoms that make him infer that the sub is bottoming out, since he couldn't have actually measured the travel, nor has he described he circumstances under which it happens
* That there is a leak is a conjecture
* That the circumstances of whoever said "bottoming=leak" are comparable to this situation is also conjecture
* It is possible for the sub to bottom out in a perfectly sealed box. After all, the air behind the sub is not solid, incompressible medium that will prevent the cone from traveling any further. It will at most only try to slow it down
* The bottoming out can be caused by
- the nature of the signal (independent of box) - faster the acceleration of the cone, more the chances that it will bottom out
- the amp is 'too good' or 'too bad' for the sub: too large output di/dt (no reflection on the ID sub) or too much peak clipping/ringing
* The leak, if at all, is more likely to be between the sub frame and the box, if the gasket is not seated well
* If the box is much larger than idea Vb, it could possibly lead to bottoming out under some circumstances
* Comparing sealed box behavior with ported/BR box behavior (with port closed by hand) is not correct - the internal volumes and dynamics are different

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