Subwoofer enclosure vibrating.

[Aucosticraft]

I made my subwoofer an year ago. It sounds good. but recently when I touched it while it was on, I found vibrations. when It was newly built I never checked if it vibrates. I used 18mm MDF with 200mm woofer. I wonder why does it happen so? It happens even at the volume level is low.I am attaching the pic of the sub woofer cabinet for better understanding of its structure. please help me to understand the problem.

[Osvaldo de Banfield]

Did you do the test under the same conditions of type of music, and volume? If yes, then some can be not well done when building it...

[Aucosticraft]

Yes, when I realized that the enclosure vibrates I kept the music going on . lowered the volume to very low. thinking that the vibrating might be because of high volume output.
I understand something might be wrong in shape of it, that results in vibration. but then what is it ?

[weltersys]

Originally Posted by Aucosticraft

Yes, when I realized that the enclosure vibrates I kept the music going on . lowered the volume to very low. thinking that the vibrating might be because of high volume output.
I understand something might be wrong in shape of it, that results in vibration. but then what is it ?

All woofers have moving mass which causes some degree of vibration.
Try sitting on the enclosure and see if you still feel the vibration.
Feel the floor, it probably is vibrating as much as the cabinet.

Excessive cabinet wall flex, which would be unlikely in a cabinet as small as yours with 18mm MDF, can be fixed with bracing.

Since it sounds good, don't mess with it .

[Osvaldo de Banfield]

I have 3 Karlson speaker enclosures, 2 of them 15" plus a 4" tweeter, and a 3rd 12"+4". Although the construction is very rigid per se, and the speakers ar rated for 70W, and I´m using only 12W max from TDA2006, I can tell you allways a small amount of vibrating in the walls must be, because internal pressures are very big and the waffle walls are not perfectly rigid. You can do a simple test to see what happen in it. I read it in some audio magazine from 70's in Argentina wrote by Saul Sorin or Julio V. Rueda (I believe): you need an audio generator and some dry sand. Put the cabinet in some fixed location, on the floor. Place over the top, some sand, set the generator in the lower frequency as you can, and increase it slowly. You can see that the sand separates and joint forming the nodes and peaks of the standing wave, and if you continue augmenting frequency can see the harmonics of it. Try this in the faces except that one containing the speaker. If the frequency of all faces are equal, then try some absorbent material inside the cabinet, but not near the walls, because it doesn´t do nothing, air velocity near the wall is zero. And, you can try some strengthen or encourage (Sorry if my english is not so good) by means of a piece of wood in the places where standing waves are most important. But have in mind that zero vibrating can be done if and only if rigidity of walls are infinite.

Good luck.

[chris661]

The seperated volume: is that for a plate amp?

If so, could that be the cause of the vibrations? I've come across vibrating transformers before.

[Aucosticraft]

Thank You for the help and suggestions.

Originally Posted by weltersys

Try sitting on the enclosure and see if you still feel the vibration.
Feel the floor, it probably is vibrating as much as the cabinet.

Excessive cabinet wall flex, which would be unlikely in a cabinet as small as yours with 18mm MDF, can be fixed with bracing.

Since it sounds good, don't mess with it .

I would try sitting on it and see if it vibrates. sure.

Originally Posted by Osvaldo de Banfield

Try this in the faces except that one containing the speaker. If the frequency of all faces are equal, then try some absorbent material inside the cabinet, but not near the walls, because it doesn´t do nothing, air velocity near the wall is zero. And, you can try some strengthen or encourage (Sorry if my english is not so good) by means of a piece of wood in the places where standing waves are most important. But have in mind that zero vibrating can be done if and only if rigidity of walls are infinite.

Good luck.

I will work this out too will need couple of days.

Originally Posted by chris661

The seperated volume: is that for a plate amp?

If so, could that be the cause of the vibrations? I've come across vibrating transformers before.

Yet the amplifier is not placed on subwoofer cabinet so sure thats not the reason.

[chris661]

Originally Posted by Aucosticraft

Yet the amplifier is not placed on subwoofer cabinet so sure thats not the reason.

Ah, I was just guessing at the use for the volume that appears to be seperated off.

[ODougbo]

A similar problem was discussed a few weeks ago; do you happen to see this?

Subwoofer box rattle issue

[Aucosticraft]

friends, I will get back here after sometime. I am not well got HAI ( hospital acquired infection) hope i recover soon.