Speaker stuffing. How much?

Braddles

Had a bit of time to spare and thought i would answer the question for myself.
I unziped the cushions on the couch and found the filling is very similar to the stuffing in my monitor 12's. A bit more dense if anything. As most who have had some experience with the 12's would know they can be a bit to bassy at times so i thought i would see what difference (if any) playing with the amount of stuffing would make.

I tried a number of different ways of placement and amount of stuffing and even with no stuffing at all. The one i have settled on for now is with the heavier cushion inners , rolled up and stuffed right up behind the drivers till they hit the top. (one on each side) and the stock filling also rolled up under the cushions so i had 2 rolls of stuffing side by side for almost the full length of the box. I played the same song with each change and i am pretty pleased with the last change. Have lost some bass over all but the sound is more balanced overall and a little less boxy. Vocals sound a little more natural too.

Cabinets lost a bit of ring and i suppose the internal sound waves would be affected.

Anyway i will live them like this for a few days and then go back to stock set up and see if i have really found the above or not.:p

ben62670

With the vintage Polk's you want free air flow to the PR's. Tuning with stuffing can help. Jerry stuffed his SDA's pretty full(loosely) and the bass tightened up and dug deeper. He had a little too much boom before. I think it helped clear up the mids a bit too. I have never heard a speaker reproduce snappy drums like his.

Braddles

ben62670 wrote: »

With the vintage Polk's you want free air flow to the PR's. Tuning with stuffing can help. Jerry stuffed his SDA's pretty full(loosely) and the bass tightened up and dug deeper. He had a little too much boom before. I think it helped clear up the mids a bit too. I have never heard a speaker reproduce snappy drums like his.

I took note of the way the factory had the stuffing behind the drivers only and took it to another level by putting the slightly heavier stuffing behind the drivers and the lighter stuffing in the bottom half of the box.

Have been just listening for the last hour or so and i aggree that they still dig as deep but tighter and more controled. Mids are clearer as you said.

Jstas

I think the better question to ask is what KIND of stuffing. I like Stove Top Cornbread stuffing myself.





Actually, the rule of thumb for loose stuffing is about a pound of polyfil for every 1 cubic foot of enclosure space.

If you are going to be lining the inside of the box, of course you need sheets of batting and that is usually about an inch thick.

In both instances, you must make sure that the stuffing is far clear of the motor structure and if so equipped, the outlet/inlet hole for the vented pole piece. The fibers can get caught up in parts and destroy them.


As for using fill, I've used it on many enclosures, even ported/slot loaded. It can help reduce cavatation and drops air speed in a small box. That reduces port noise and evens out pressure in a box with a high performance sub but a small amount of air space.

I built a box that was half the size of a slot loaded enclosure with flared ports. The slotted enclosure I was trying to beat was about 152.8 dB. I built my box with 1/3rd less internal airspace and a smaller port. That brought port velocity way up. To drop it down a bit and get some control, I stuffed it with loose fill. My box, with the same amps and subs, pushed 153.6 dB. Stuffing can help an enclosure perform to full potential but enclosure design is critical. But it can make a big difference in the end, just gotta experiment.

skrol

I had heard here and from Polk CS that you should only have the dacron (stuffing) behind the mid-drivers. Or in some cases above an behind the mid-drivers. That the why it is placed in my RTA11TL's (see attached).

That said, I was surprised how much dacron is stuffed in my Monitor 5A's. It really packed and even behind the PR. I have been meaning to ask Polk CS about this. I believe that this is the way it came from the factory as I don't think the previous owner touched them. Other wise he certainly would have remove all the glue scraps that were rattling around inside.

Stan

skrol

I am certainly no expert on this but in general, the amount and where and type depends on the type of enclosure. In a sealed enclosure, the absorption material tends have the effect of making the enclosure acoustically larger. You can tune the enclosure to some degree by adding more or less material. It also is used to absorb the back wave from the driver. This prevent the sound wave from the rear of the driver from reflecting off the parallel back of the enclosure back at the driver.

In a ported it is usually lined along the inside panels but usually not filling the enclosure as much as in a sealed enclosure. This helps to absorb the back wave and to reduce the boxy sound from exiting the port. You should avoid having the material interfere with the air flow in and out of the port.

I am still learning the physics of the Passive Radiator enclosure but as I understand, it is similar to the ported design. You do not want to interfere with the PR motion. As far as what the proper placement should be (behind the PR or not) I am not sure. I thought that you generally did not place it behind the PR but, as mentioned above, this is not the case with my Monitor 5A's.

Stan

jimbo1421

Braddles wrote: »

Had a bit of time to spare and thought i would answer the question for myself.
I unziped the cushions on the couch and found the filling is very similar to the stuffing in my monitor 12's. A bit more dense if anything. As most who have had some experience with the 12's would know they can be a bit to bassy at times so i thought i would see what difference (if any) playing with the amount of stuffing would make.

I tried a number of different ways of placement and amount of stuffing and even with no stuffing at all. The one i have settled on for now is with the heavier cushion inners , rolled up and stuffed right up behind the drivers till they hit the top. (one on each side) and the stock filling also rolled up under the cushions so i had 2 rolls of stuffing side by side for almost the full length of the box. I played the same song with each change and i am pretty pleased with the last change. Have lost some bass over all but the sound is more balanced overall and a little less boxy. Vocals sound a little more natural too.

Cabinets lost a bit of ring and i suppose the internal sound waves would be affected.

Anyway i will live them like this for a few days and then go back to stock set up and see if i have really found the above or not.:p

Hi Braddles,
Inquiring minds need to know:
What did your wife or SO say about the empty sofa cushions?
Where are you sitting now?

Jim

Braddles

Hey Jim,

Very good question.

I didnt even get to tell her what i had done when she came into the study and read my first post over my shoulder and said "what!' my cushions".

Busted!

BTW. They were only the scatter cushions that you throw on top of the sofa not the main cushions.

fbm211

Did she run to see what you had done to her cushions? Did it go like this---Hand on hip and pointhing a finger at you and say---Put them back...NOW!

fbm211

Maybe you can ask her if you can but 5 pounds of that acousta stuf they sell at parts express http://www.parts-express.com/wizards/searchResults.cfm?searchFilter=acousta stuf

jimbo1421

Don't get me wrong, Braddles. I think it is a great idea to experiment with things that are just lying around the house before spending your hard earned money on Acousta-stuf. Your wife should appreciate that, too. You should also try the feathers from the down comforter. With a little shaking they will plump up the mid range nicely.

Jim

Braddles

jimbo1421 wrote: »

Don't get me wrong, Braddles. I think it is a great idea to experiment with things that are just lying around the house before spending your hard earned money on Acousta-stuf. Your wife should appreciate that, too. You should also try the feathers from the down comforter. With a little shaking they will plump up the mid range nicely.

Jim

I like your attitude Jim. You and i think very much alike.:cool:

Im very lucky. My wife was cool with the whole thing. In fact i took the cushion infills back out on the weekend and she asked why i was taking them out for if i was happy with them in.

skrol

You can get Dacron and other stuffing materials fairly cheap at fabric stores. Might also find acceptable grill cloth type materials.