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Discussion Starter · #1 ·
OK, I am not talking about getting an early jump on Thanksgiving, I just need advice on if I should add poly or a few pillows or not.

This is a sealed enclosure for a LMS Ultra 18" at 4cuft with a box Q of 0.597. I used Sonic Barrier 3/4" on the inside and have to admit that it deadened the panels even further, this stuff works. If it wasn't for the LMS Ultra I wouldn't use SB again though, it's too expensive IMO.

My question is does Sonic Barrier offer the same properties as adding poly into the enclosure for damping or should I add some more poly or a few pillow's?

Here is a cut & paste from the SB description that sounds like it does what poly does:

An exclusive embossed surface finish helps to trap the acoustic energy into a 1/2" acoustic foam where it is converted to low-level heat. A 1/4" foam layer covered with 1/2 lb. limp copolymer vinyl barrier separates the absorptive layer from the cabinet walls.

Here is a pick of the inside with the SB already installed:



A build thread is coming soon, I just have to clear some items from my schedule to get it started.
 

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I used the same 3/4" SB to line my midbass enclosures, and I agree that it's a good product, but overpriced.

As for stuffing, the real advantages of the SB lining are the additional panel damping, and the prevention of internal reflections. For a sub, you're not going to get standing waves at sub frequencies, but the higher harmonics produced by the cone above the program passband could be reflected back to the cone. This is more of an issue in ported systems, when you don't want to hear objectionable high frequencies produced by the port. For a sealed sub, stuffing will provide the advantage of adiabatic / isothermal conversion, resulting in a response similar to a slightly larger enclosure. Stuffing material, whether polyfill or fiberglass, is generally cheap, so my suggestion would be try try some and see how it sounds. My guess is that you will want to stuff to some extent. While the SB material performs this function to some extent, the lining will not be as effective as stuffing for that purpose.

In my own system, I have a large ported subwoofer / bass enclosure which is unlined except for the faces immediately opposite the ports. I didn't require any additional panel damping, as this box is 1" MDF, which is 2.37 times stiffer than 3/4" MDF. Depending on your box design, SB can be helpful damping a resonant panel, but it is otherwise overkill IMO. I put some fiberglass opposite the ports to eliminate any possible mid-frequency reflections out of the port, but the box is otherwise unlined.

My midbass enclosure is lined completely with 3/4" SB - this enclosure is ported, so I wanted to stay away from stuffing so as not to interfere with the port, but still needed to eliminate internal reflections and standing waves at the higher midbass frequencies - this is where the SB shines, in addition to providing a bit of additional damping to the 3/4" MDF panels. My midrange enclosure, conversely, is a sealed enclosure which is not lined, but which is completely loosely stuffed with fiberglass.

The bottom line is that SB, as you noticed, helps with damping panel resonances, but IMO that sort of thing is best avoided by using thicker enclosure walls. 1" MDF instead of 1/2" ply makes a bigger difference than any amount of lining. The SB, being a hybrid material, also provides some of the same function as polyfill or fiberglass stuffing, but is somewhat superfluous if you are going to stuff anyway, unless you need the additional damping. I usually put some on the panel opposite the driver, and cover features like jack plates and handles which might ring, but otherwise would not line an enclosure I intended to stuff unless it had panel resonance problems. This is not to say that what you did is a bad thing - just unnecessary if you are going to stuff, which is my preference with sealed enclosures.
 

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Discussion Starter · #3 ·
Thank you for the very informative response.

I agree and freely admit that my enclosure is definitely OVER-KILL. To tell you how insane I went the box is actually 1 layer 3/4" Ultra Light MDF followed by another layer of 3/4" 13 ply Baltic Birch for a total of 1.5 inches all around except for the baffle which is 2.25" BB. I actually made 2 so I added the SB to the first enclosure and did the knuckle test all around both boxes and the SB treated box was noticeably deader.

I didn't start out to make them 1.5" thick but part of the way through I decided I would hide the ply edges with 1/4 round maple trim so I needed to double up on the thickness. Once I made that decision I already had the materials so decided to use them.

I wouldn't have gone to this trouble if it wasn't for the LMS Ultra subs which vibrate my Mal-X box which is nicely braced. My former box just made too much motion and felt cheap with the LMS so I figured what the hay.

Here's a pic before the maple trim:





Here's a pic of the corners after all the sanding and stain/varnish:

 

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Nicely done. If you're going to go all-out with a sealed enclosure, nice thick panels, strongly bonded at their edges, reinforced with internal bracing, lined with SB, and stuffed with fiberglass or polyfill (fully stuffed while keeping this material at its maximum expansion, and keeping it clear of your driver motor vent) can't be beat.

How does it sound?
 

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I just realized I made a mistake when I wrote that 1" material is 8 times stiffer than 3/4" material. Panel stiffness is proportional to the cube of material thickness, so doubling a panel makes it eight times stiffer (which must have been what I was thinking of). Going from 3/4" to 1" only makes it 2.37 times stiffer.
 

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Discussion Starter · #6 ·
I am swamped this week so I haven't had a chance to load the subs yet.
Right now the single LMS in my old box sounds really good besides the resonance I am getting from the box. With dual LMS in these new enclosures I am expecting really good things.

I also have to wait until I can get home early enough to have a friend come over to help me install the 80lb subs. Normally I am not this patient but there are just too many things going on.

Thanks again for the advice, I will fully stuff the box avoiding the motor vent and let you know how they sound.
 

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I don't think you need anymore than you already have installed.
You have done an excellent job of construction and design. The box and LMS are a killer combo.
What power do you have to drive it with? It'll take a ton.
 

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Discussion Starter · #8 ·
Hey Phil,

Are you still cranking your LMS subs? I remember you were one of the pioneers with the LMS.

The power will most likely be a QSC RMX-5050 but I have a PL 9.0 too but I would have to run a 30 amp line for that monster. The PL 9.0 also has 4 fans so I would probably have to have it in another room as it's too loud in the same room. I actually never listen at reference level, normally -10 at the most and generally -15 most of the time so the 5050 will probably be enough.

Thanks for the compliment on the box and design. It was actually supposed to be a much simpler design that morphed into over-kill. I still need to make grills but that will have to wait until I can free up some time.
 

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YEOW!! A 5050 and a PL 9.0 ! You don't fool around. :gulp:

I've retained the LMS and the 100L box. I still drive and analyze with a Crown Xti 4000.
I HAVE added a new PIONEER receiver, Elite vsx-23TXH with the MCACC system. The MCACC system has almost overcome the room modes and really does a good job integrating my mains with the LMS.
Daily use of this combination gives me a smirk every time there's an accidental mike dropout or station switch thrown or even an outdoor wind gust across an unprotected microphone, the sub cone jumps reproducing the unintended low Hz thump. It never burps on anything though . . . . even when I purposely play a string a ridiculously HEAVY bass loaded material, the latest I found was in the movie, "The New Daughter". The LMS and Crown were working on that material and it was obvious visually by blinking lights on the Crown, the cone movement, and audibly by my closet door which rattles at 13 Hz @ 104 dbs.
You're gonna become very satisfied over time realizing you've filled-in the bottom of the audio spectrum with the best there is.
 

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My suggested stuffing material is mineral wool. It's cheap and highly effective. I use 2.5 density because in Tom's reading it lowers box tuning the most.
 

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Discussion Starter · #11 ·
Crown Xti 4000 ain't fooling around either, nice amp:T

I wish they still made the red basket like what you have, it really made it stand out even more from the other TC lines.

Did you notice any break in on the driver over time? I have seen Kyle from TC mention the VMP's would break in for a bit of a lower tune over time due to the suspension softening up as they come very stiff at first. I figured this must be the same for the drivers but you have had your LMS long enough to know.

Thanks for the tip on the movie, 13 Hz @ 104 dbs is impressive and it's not a movie that was on my radar.
 

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Discussion Starter · #12 ·
My suggested stuffing material is mineral wool. It's cheap and highly effective. I use 2.5 density because in Tom's reading it lowers box tuning the most.
Where do you buy mineral wool from? I did a google search and found Mineral Wool Boards for sale at Grainger but I would suppose that's not the same thing.
 
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