suggestions regarding making of subwoofer box

[Gill]

Originally Posted by low_bass_makker

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

[kURETI]

1st the enclosure needs to be airtight if its an sealed enclosure. before u check for airleaks check the dimension as per the specification of the sub. Yes using screws are better as they dont loosen when the sub is playing.
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.

[kURETI]

performance of the sub calls for a good amplifier and a good enclosure - selection of enclosures largely depends upon the vehicle and the amplifier.
a good and a knowledgeable installer will be of a great help to decide the sub, enclosure and amplifier.

Remember the more u spend the better you get.

[ScarySkulls]

Originally Posted by kURETI

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.

Originally Posted by kURETI

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.

[navin]

Originally Posted by ScarySkulls

I tried with all my might. Got all dimensions perfect. Sealed up the insides with a mix of the dust and fevicol. Then topped it with silicone sealant. Still leak in the end

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

[ScarySkulls]

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?

[navin]

Originally Posted by ScarySkulls

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.

[low_bass_makker]

Originally Posted by ScarySkulls

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.

[DerAlte]

Originally Posted by navin

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

Originally Posted by ScarySkulls

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?

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

[ScarySkulls]

Originally Posted by DerAlte

* @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

Symptoms:- Bottoming out at a volume level prior to when the HU starts clipping. Bottoming out with Zero bass boosts or EQ.

Originally Posted by DerAlte

* That there is a leak is a conjecture

That is true.

Originally Posted by DerAlte

* That the circumstances of whoever said "bottoming=leak" are comparable to this situation is also conjecture

Cant understand why. Please educate more on this.

Originally Posted by DerAlte

* 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

Happens on all varieties of songs. Mp3 or Audio cd. Signal from Amp appears clean too --> Components play clean all the way.

Originally Posted by DerAlte

- 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

I dont think a GTO75.4 amp should be either of the two for a 10" ID sub.

Originally Posted by DerAlte

* The leak, if at all, is more likely to be between the sub frame and the box, if the gasket is not seated well

Very much possible. Best way to detect and correct leaks caused by this?

Originally Posted by DerAlte

* If the box is much larger than idea Vb, it could possibly lead to bottoming out under some circumstances

Box has been built to exact specs as on the recommended enclosure sheet.

Originally Posted by DerAlte

* Comparing sealed box behavior with ported/BR box behavior (with port closed by hand) is not correct - the internal volumes and dynamics are different

Yes, Yes. Ofcourse. That is what many others think also

[DerAlte]

Originally Posted by ScarySkulls

Symptoms:- Bottoming out at a volume level prior to when the HU starts clipping. Bottoming out with Zero bass boosts or EQ.

What makes you infer it is "bottoming out"?

Originally Posted by ScarySkulls

Cant understand why. Please educate more on this.

It is a conjecture since it is not established that bottoming out, if so in your case, is due to a leak

Originally Posted by ScarySkulls

Happens on all varieties of songs. Mp3 or Audio cd. Signal from Amp appears clean too --> Components play clean all the way

Mechanics of the components are not comparable to the sub at all. In fact the root cause of bottoming out (excessive travel) is at frequencies (< 40Hz) that the components don't handle.

Try playing "Jaane kyun log pyaar karte hain" from that Aamir Khan movie - it has a synthetic bass accompaniment which slides really really low on every note. You can figure out at what point (even at low volume) the cone really starts to reach limits of excursion.

Originally Posted by ScarySkulls

I dont think a GTO75.4 amp should be either of the two for a 10" ID sub.

I agree, though I have not personally experienced the combination.

Originally Posted by ScarySkulls

Very much possible. Best way to detect and correct leaks caused by this?

Talcum, or any other, powder sprinkled around the periphery of the frame. Will not be affected by the normal bass but will be blown away by a leak! The leak should go away if you unmount and mount the sub again - make sure that you tighten diametrically opposite screws / bolts. If it still doesn't use a thin layer of either a silicone sealant or a gasket sealant used in automobiles.

Originally Posted by navin

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.

I agree, this could be the most likely cause and remedy. Or a smaller sealed box (ID is comfortable down to 0.7cft).

[Bass&Trouble]

Originally Posted by DerAlte

Try playing "Jaane kyun log pyaar karte hain" from that Aamir Khan movie - it has a synthetic bass accompaniment which slides really really low on every note. You can figure out at what point (even at low volume) the cone really starts to reach limits of excursion.

People who tried "Jaane kyun log pyar karte hain" also tried:

Bally Sagoo's version of Chura Liya
Karunesh - Punjab
Nitin Sawhney - Nadiya

[low_bass_makker]

I would use sine waves for the same.

[Bass&Trouble]

Originally Posted by low_bass_makker

I would use sine waves for the same.

Yeah, on a 2400 W rms amp at that. At full tilt. No wonder you're in the market for a new battery.

[ScarySkulls]

Originally Posted by DerAlte

What makes you infer it is "bottoming out"?

If the general notion that "Speaker fat rahe hain yaar"....Or crossing excursion limits means bottoming out, then that's perfectly it.

Good idea on the Talcum powder. Thanks.
Lets see what happens. Give it a shot Gill.