Stuffing AND lining cabinets?

[unknownuser]

I know I've asked about this before, but I couldn't find anything in the search, nor could I remember any details, such as the answer ;)

I'm knee deep in a pair of sealed MTM's right now, and though the walls are quite rigid (1/2" thick curved layered lamination), they still aren't quite as dead as I'd like. I planned on stuffing the cabinets for bass purposes, and I have some left over Sonic Barrier (The expensive multi-layered stuff.)

I want the walls as dead as possible, and it seems to me that going all-out on the inside will be an easier way to get this done than adding another two layers to bump it up to 3/4" wall thickness. (That would take two weeks at my current pace - per speaker)

Does stuffing affect the "deadness" of the cabinet at all? Is there any reason NOT to stuff the cabinet AND line the walls?

Thanks!


(Originally posted by: Kyle)

[cjd]

Start out lining the walls near the drivers and behind them. The goal being elimination or at least control of rear-wave reflections.

Stuffing works a bit differently, but you'll want to take care in both lining and stuffing that you don't over-do it.

At any rate, there is value in both. ANd I think the 3-layer Sonic Barrier works quite well. I've used it a couple times. On my 3-ways, it was a dramatic difference inside before and after adding the barrier to the walls (since I could stick my head in the box). Wall deadness by the knuckle rap test was improved also. I subsequently stuffed these cabinets lightly.

C

[aztd]

The arced wall is stronger than a flat wall. Look at bridges. My guess is that the wall is deader than you think. If is the one that I have seen pictures posted of, you have done an excellent job of bracing. Just an idea maybe a ½ inch of fiberglass on the inside would help. I am talking about the fiberglass used to make boats. The car audio guy use it a lot to make odd shape boxes?

[bking]

Kyle, try the PE asphalt-based damping sheets, part number 268-010. Easy to apply with adhesive backing and very effective. Then stuff the enclosure with the appropriate amount of fiberglass or dacron fill.

[thylantyr]

Cabinet deadening can be referred to as lowering
it's resonant frequency. Knock on the cabinet
and the sound is high pitch right? Knock on
the cement floor and it's a very low pitch. Point
is, you have to add lots of mass to the speaker
box design to lower it's frequency and you can use
bracing techniques to help you out. Even a cross
brace helps. The cheapest way to add mass is to
make this walls and use MDF. The expensive way
to add mass to the walls is to buy esoteric product
that cost way more than a hunk of wood. If you
are in a pickle, add some tiles to the inside of
your cabinet to add mass.

Next, sound conditioning. After you have a dead
box, add the polyfil, fiberglass, wool, etc type\
of product to remove 'echo' {standing waves} for
a cleaner midrange sound and you can do it for
bass reasons too.

It's really a 2 step process.

[unknownuser]

> The arced wall is stronger than a flat wall.
> Look at bridges. My guess is that the wall
> is deader than you think. If is the one that
> I have seen pictures posted of, you have
> done an excellent job of bracing. Just an
> idea maybe a ½ inch of fiberglass on the
> inside would help. I am talking about the
> fiberglass used to make boats. The car audio
> guy use it a lot to make odd shape boxes?

It is a very well braced box, and the concept was based on the idea that arced walls are stronger, but with one hand on this MTM, and the other hand on my 3/4" MDF Sonic Barrier'ed tower, I can tell that it is resonating more. I know absolutely nothing about fiberglass... But it sounds complicated (and expensive)


(Originally posted by: Kyle)

[bobblickle]

I don't think fiberglass lamination is the way to go. Use of fiberglass in autosound is usually driven more by the need for max enclosure volume and odd shapes than some inherent low resonance. Why not try floor tiles, the panels someone recommended, or some high density carpet foam? Or just try out the SB you have and tell us how it did. If it doesn't help, pull it back out and reglue it to the next project. Do one and compare it to the other with your knuckle test.

Good Luck.

bb

> It is a very well braced box, and the
> concept was based on the idea that arced
> walls are stronger, but with one hand on
> this MTM, and the other hand on my 3/4"
> MDF Sonic Barrier'ed tower, I can tell that
> it is resonating more. I know absolutely
> nothing about fiberglass... But it sounds
> complicated (and expensive)

[Andy_G]

> I'm knee deep in a pair of sealed MTM's
> right now, and though the walls are quite
> rigid (1/2" thick curved layered
> lamination), they still aren't quite as dead
> as I'd like.

1/2" isn't really thick enough even for laminated curves (IMO), but you may find that even one extra layer makes a significant difference.

[jtaylor]

> I know I've asked about this before, but I
> couldn't find anything in the search, nor
> could I remember any details, such as the
> answer ;)

> I'm knee deep in a pair of sealed MTM's
> right now, and though the walls are quite
> rigid (1/2" thick curved layered
> lamination), they still aren't quite as dead
> as I'd like. I planned on stuffing the
> cabinets for bass purposes, and I have some
> left over Sonic Barrier (The expensive
> multi-layered stuff.)

> I want the walls as dead as possible, and it
> seems to me that going all-out on the inside
> will be an easier way to get this done than
> adding another two layers to bump it up to
> 3/4" wall thickness. (That would take
> two weeks at my current pace - per speaker)

> Does stuffing affect the
> "deadness" of the cabinet at all?
> Is there any reason NOT to stuff the cabinet
> AND line the walls?

> Thanks!

I believe I've seen the pictures of the curved wall speakers you have been working on. I can understand your reluctance to add the last two layers of lamination. You have already spent a lot of time and effort so far and your to the point that you want to move on. I believe that you need to suck it up and put the last two layers of laminate on each cabinet. I think you have done a great job to this point and should finish the cabinet construction as required. At least if you have built the lamination to the correct thickness, you can't blame that shortcut if the cabinets don't sound solid.

I know how tiring the lamination process can be in a complex project. I just think you will feel better with the final project if you take the extra time and do it 100%. I know you hate to think of two more weeks, but in the long run it will show. The extra thickness and weight all adds up to more strength, and less vibration.

I'm sure you could take a shortcut, using materials on the inside to make up for the lack of wall thickness. That would be something I would expect from some one building a commercial product. Take your time and put your pride into making a top notch speaker that you will be very proud of for many years to come. JMHO.......

Jack T.

[edlafontaine]

Owens Corning makes a peel and stick material called "Starter Shingle Roll". 7.2" wide X 33' will cost less than $15. I bought mine from Lowe's. Floor tiles are available for ~ $0.99 ea. You will need to use a mastic adhesive between them. Auto weather strip adhesive works well. Wear gloves or you'll be totin' the evidence around with you on your hands after foolin' with it. Cut the tiles into strips to conform to the inside of your cabinet.

[damkor]

> Is there any reason NOT to stuff the cabinet
> AND line the walls?

Yes, if you care at all about the bass response of the cabinet/woofer. Unless this is a midrange cabinet, you need to watch that you don't end up removing all the volume of air from the box by over-stuffing. Obsessive over-stuffers tend to choke up their boxes, and end up with thin, under-whelming bass. I would keep the wall lining thin, use a cross-brace, and then listen to the system with no stuffing, add some stuffing to one speaker, and see if you hear a difference. Sometimes, people mistake decent bass for boomy bass.