[bdman]

Originally Posted by bdman

This is true. I opened up the front grill (rear is pretty much the same)...

I just installed rear speakers, and the dimension of the cavity behind the speakers are even more cramped than the front . The same model 5 1/4" beefier speakers that dropped into the front required some cutting before they could be installed in the rear. Beware.

[bdman]

After not being satisfied with the sound quality even after replacing my speakers -- not enough bass, mid-range lack of focus -- I decided I would try to stuff the doors with padding. What a huge difference in sound that made! Bass is much deeper and mids more clear.

Procedure is simple:

1. Procure 2 nos, 12"X12" sofa cushions with polyfill. Available at most big stores like big bazar etc. Rip cover.
2. Detach speaker grill
3. Remove speaker - you will need a Torx Screwdriver
4. Stuff as much polyfill as you can into door via the speaker hole (about 1/2 cushion)
2. Replace speaker and grill.

I highly recommend this as the first option for any one who wants to improve their sound, as it is the cheapest.

[ampere]

Originally Posted by bdman

1. Procure 2 nos, 12"X12" sofa cushions with polyfill. Available at most big stores like big bazar etc. Rip cover.

I got the doors damped both inner and outer linings along with speaker change. Now based on what you mention, it looks like it does make a difference to the sound. I got it because I just wanted a heavier door feeling, which I got too!

So improvement in bass/mid range, does show up. I thought it may happen, but was not sure about it.

[condor]

@Ampere, he has filled the cavities. You have damped your doors using Damping sheets.

Would be good to compare both ..

[bdman]

Originally Posted by ampere

So improvement in bass/mid range, does show up. I thought it may happen, but was not sure about it.

Depends if they have damped the front of the doors (behind the panels) or the rear (against the metal). If the former, I think you may still get some benefit of stuffing.

IMHO, the sound gets distorted because of internal reflection/resonance from the door.

Related Article

[ampere]

Originally Posted by bdman

Depends if they have damped the front of the doors (behind the panels) or the rear (against the metal). If the former, I think you may still get some benefit of stuffing.

IMHO, the sound gets distorted because of internal reflection/resonance from the door.

Thats what I thought to. I got the full door inner and outer linings damped.
As condor said, I did not fill the cavities part, but got the doors damped.

[condor]

Originally Posted by bdman

IMHO, the sound gets distorted because of internal reflection/resonance from the door.

So when you damp the sheets in the door, it alters the reflection & resonance. I have damped the doors of my Ikon (only outer sheet). I think it made a good difference - no stuffing, or damping of inner sheet.

[DerAlte]

Originally Posted by condor

... no stuffing, or damping of inner sheet.

Stuffing is anyway ruled out - where will you stuff what?

What you have done is quite right, @condor, the inner metal is broken up by large gaping holes and doesn't resonate. Some judiciously placed damping does help reduce rattling.

[condor]

May be the foam that was mentioned a few posts back, between the two sheets of the door ? (Not that I want to do that)

Originally Posted by DerAlte

the inner metal is broken up by large gaping holes and doesn't resonate.

Sir.ji, then why do the auto accessories shops close these holes (on the inner sheet) with damping sheets ?

[DerAlte]

Originally Posted by condor

... then why do the auto accessories shops close these holes (on the inner sheet) with damping sheets ?

A very innocent assumption: closing all the holes in the inner sheet is going to make a box out of the cavity between the inner and outer layers, and give more bass!!! One has to realize that when the damping material is not stuck to a metal / FRP layer, it is *not* doing *any* damping - it is transparent to sound. And not just auto accessory shops, even many experienced installers do that. They also think it will save them time if the just plaster on a whole sheet of damping material.

It is a good practice to close the holes, though - but with the plastic sheet that was the original vapor barrier. This is to prevent moisture ingress into the cabin.

[bdman]

Originally Posted by DerAlte

A very innocent assumption: closing all the holes in the inner sheet is going to make a box out of the cavity between the inner and outer layers, and give more bass!!!....

True, but stuffing has the theoretical effect if making the enclosure seem much larger, hence even more bass!

And the stuffing can be done quite simple by removing the speaker and stuffing through the same hole that lies behind it. Unless, the damping material has closed up that hole too.

[DerAlte]

Originally Posted by bdman

... the theoretical effect if making the enclosure seem much larger, hence even more bass! ...

If the enclosure is created with rigid walls *not* transparent to sound (like the enclosure of a sub), one can understand. With large holes covered with a rubber-like material which is transparent to sound - it is definitely a 'theoretical effect'!!! Even then, done without accounting for the T-S parameters of the speaker would be like taking pot shots in the dark.

Originally Posted by bdman

... And the stuffing can be done quite simple by removing the speaker and stuffing through the same hole that lies behind it. ...

Not sure I understand what you are trying to say. Stuffing what in which hole behind where? To remove confusion, 'stuffing' would mean stuffing cotton waste, CC foam or thermocole between 2 planes.

[bdman]

Originally Posted by DerAlte

Not sure I understand what you are trying to say. Stuffing what in which hole behind where? To remove confusion, 'stuffing' would mean stuffing cotton waste, CC foam or thermocole between 2 planes.

Stuffing would mean any soft sound absorbing material. I used polyfill with is used to to fill pillows etc. It is polyester fiber and would not absorb water in case of leaks etc. When the speaker is removed, there is hole behind it that opens up into the door cavity. The polyfill can be stuffed through this hole into the door. Thermacole and other rigid material would not work as it would disintegrate.

[sumeshmani]

I am not an expert, just sharing some internet findings.
http://moneyexpertsteam.blogspot.com...er-louder.html

This page says:
"Fill your subwoofer enclosure with polyfill can help increase the volume level of your subwoofer. Its simply buying a cheap bag of polyfill and stuffing it into your subwoofer box. What polyfill does is it tricks the subwoofer driver into thinking it is placed in a larger box with more cubic volume."

[DerAlte]

Originally Posted by bdman

... I used polyfill with is used to to fill pillows etc. ...

So you used polyfill to fill the bottom 20% of the door (assuming the rest 80% is required to be kept free for window operation)!!! Interesting, though I wouldn't expect anything to happen - neither lowering of bass nor improvement of sound.

Originally Posted by sumeshmani

... This page says: ...

Very simplistic, though not untrue - but only for specific configurations and setups. One wishes that one can extend such logic to other circumstances, or explain the maths behind it in easier terms.

1. One adds polyfill first and foremost to cut out the resonance in the subwoofer enclosure. Usually one uses 0.5-0.8Kgs of polyfill in a box with internal volume of 1cft. (approximation) for this

2. All this is dependent on Thiele-Small parameters of the subwoofer and the exact volume of the enclosure

3. The same logic cannot be extended to relatively higher frequencies, i.e. mid-bass speakers
a. The door cavity volume is much larger than what calculations with T-S parameters of the mid-bass would indicate as required enclosure volume
b. Putting stuffing in 20% of the enclosure volume doesn't even tickle any of the variables in the equation