Stuffing problems?

[Vikash]

The enclosure is sealed and approx 90 litres, and I've stuffed with approx 1Kg of "100% hollow polyester fibre filling".

The aim was to reduce the harsh mid frequencies but instead the bass has dropped significantly compared to the other yet to be stuffed enclosure.

Perhaps too much stuffing, or the wrong type of stuffing?

I also couldn't hear any improvement to the sound that I was hoping for. Dagnammit.

[Bull]

Well for bass reflex only dampen the rear wall,because the air is essential for their operation.
For sealed, wadding on all sides except for baffle board.
And Acoustic Labyrinth/Transmission Line, wadding on flare path only.

Hope this helps.
Good quality and thick amounts of BAF wadding is the one of the best to use,also 'egg crate' studio foam is another great dampening for enclosures.

[roddyama]

Do you have free space behind the driver?

[Vikash]

The bracing splits the cab into six, and all are equally densly packed with stuffing, including right behind the drivers. There is space for the diaphragm to move without touching the stuffing - but that's about it.

[roddyama]

Try removing the stuffing from directly behind the driver. You should have some "chesse cloth" type material behind the speaker to protect it from fibers that can get into the voice coil area.

You should be able to get the bass back assuming nothig bad happened to the speakers. But it's possible that may never get rid of the harshness. It simply be a characteristic of the driver. You might start to look at things like the x-over.

[Vikash]

I will try removing the stuffing from the sub-cabs behind the drivers and see if this helps (update: I've taken some pics - how much to take out?). I have however just noticed that I can't get a DMM reading for the 10uf cap in the xover. I guess this may be the culprit.

Regarding the harshness, I'm sure it's not the drivers as they sounded ok in their previous enclosures.

I want to redo the xover, and need all the help I can get!

[ashok]

Hi Vikash,
The density of the filling is quite important. If it gets stuffed too much you could also reduce internal volume. You should make sure that the stuffing is not ' compressed'. The area behind the driver should have some stuffing but not right up to the driver. As mentioned in an earlier post , you can avoid that by putting a muslin cloth around the rear of the speaker.
Especially the top part behind the upper driver is potentially bad . It will reflect back upper frequencies and they will have to be absorbed.
In fact you could use light filling behind the drivers and add stuffing in the rest of the cabinet to suit the performance.
Right now it really looks overstuffed.
I can't see a duct. If you did have one , they recommend a clear - stuffing free- path from driver to the duct.
I suggest you remove all the stuffing from the rear section , stuff the frontal sections with very fluffy material and test it. It might just be enough. You may have to fluff up the existing material and use less of it.
Cheers.

Edit: Measuring the impedance curve will show you what is happening. Resonance frequency and the damping ( Q ) can be seen from that.