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Sub Stuffing

post #1 of 20
12/3/12 at 8:00pm
Thread Starter 
Hey guys,

I just read several "box stuffing" threads but didn't really get an answer to what I'm confused about.

I built two sealed enclosure that contains two drivers each (infinity 1260's) and I built the enclosures a little on the large side. I did not stuff the cabs with anything. I watched a movie the other day and I was getting some muddy sounding bass. This was the first time I heard this issue and it has only happened during this one movie, Iron Man 1. All other movies and music have sounded great so far. I was thinking about stuffing the cabs to tighten the sound up a bit or see if I've been missing anything, but here's my issue.

If I stuff a cabinet that was built on the large-ish side, would the stuffing have an adverse effect? Would it trick the drivers into thinking they are in an even larger enclosure?

If I should stuff, would I see any benefit to using a layer of mineral wool on the walls and pillow type stuffing in the open areas?
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post #2 of 20
12/3/12 at 8:25pm
maybe, probably just the movie its self stuff it anyways with a few pillows
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post #3 of 20
12/3/12 at 8:30pm
It is easy to try stuffing to get some direction if it is an improvement or not. But 1st, have you exhausted all other tuning ideas like changing position of the subs relative to your listening area, Cross-over settings, Phase, etc?
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post #4 of 20
12/3/12 at 9:21pm
Thread Starter 
Quote:
Originally Posted by Gaugster View Post

It is easy to try stuffing to get some direction if it is an improvement or not. But 1st, have you exhausted all other tuning ideas like changing position of the subs relative to your listening area, Cross-over settings, Phase, etc?

I've had my setup in its current position for a few months now and it has sounded great. But when we watched Iron Man the other day there were a few spots that sounded really boomy and out the ordinary. So I don't see a need to change placement. It just got me thinking about stuffing and whether or not it would help to correct the sound for whatever frequency is being presented in that movie (and maybe others I haven't come across in my library yet).

Before I start messing with stuffing:
If I stuff a cabinet that was built on the large-ish side, would the stuffing have an adverse effect? Would it trick the drivers into thinking they are in an even larger enclosure?

If I should stuff, would I see any benefit to using a layer of mineral wool on the walls and pillow type stuffing in the open areas?
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post #5 of 20
12/3/12 at 10:33pm
I don't think there is a right answer to your question. It sounds like you are trying to correct a problem that exhibits itself on 1% of your material. You could stuff them and another problem rears its head elsewhere. If it sounds great on 99% of the material you listen/watch, I personally would leave it alone. But hey, stuffing is cheap so what the hell. biggrin.gif

You don't mention what sound treatments you have done. Tailor the room to your sound, not the sound to your room.
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post #6 of 20
12/3/12 at 11:06pm
the problem is almost certainly unrelated to stuffing in the subs and is because the iron man bass was hitting on a room mode that you have. room modes can make bass boomy (too loud) and sloppy (ring in the time domain).
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post #7 of 20
12/4/12 at 6:02am
Quote:
Originally Posted by jayHRC51 View Post

If I stuff a cabinet that was built on the large-ish side, would the stuffing have an adverse effect?
What's the Qtc of the cabs? If it's much more than 0.8 stuffing will reduce it, which can help with boom. If It's less than 0.8 reducing Q might be beneficial, but probably not.
Quote:
I watched a movie the other day and I was getting some muddy sounding bass. This was the first time I heard this issue and it has only happened during this one movie, Iron Man
That indicates the fault lies with the guy in the mixing booth.
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post #8 of 20
12/4/12 at 12:58pm
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

What's the Qtc of the cabs? If it's much more than 0.8 stuffing will reduce it, which can help with boom. If It's less than 0.8 reducing Q might be beneficial, but probably not.

Bill, that's an excellent question. I'm not quite sure what the Qtc of the cabinet is. I have a pair of the following - two Infinity 1260's in a single sealed enclosure that is 4 cuft. I took recommendations from others on cabinet size so I didn't do the modeling myself. How would I go about calculating the Qtc of the cabinet?

Driver specs were as follows:

VOICE COIL DCRESISTANCE: REVC (OHMS) . . . . . . 3.59
VOICE COIL INDUCTANCE @ 1KHZ: LEVC (MH) . . . . . . . 2.89
DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 82.30
SD (M2) . . . . . . . 531.00
MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 16.90
COMPLIANCE VOLUME: VAS (FT3) . . . . . . . . 2.92
VAS (LITERS) . . . . . 82.96
SUSPENSION COMPLIANCE: CMS (μM/N) . . . . 206.00
MOVING MASS, AIR LOAD: MMS (GRAMS). . . . 222.00
MOVING MASS, DIAPHRAGM: MMD (GRAMS) . . . 214.00
FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 23.50
MECHANICAL Q: QMS . . . . . . . . . . . 6.99
ELECTRICAL Q: QES . . . . . . . . . . . 0.41
TOTAL Q: QTS . . . . . . . . . . . . 0.39
MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . 0.314
HAG (MM) . . . . . . . . 8.00
VC (IN) .. . . . . . . . . 1.34
HVC (MM) . . . . . . . . . . 34
MAXIMUM EXCURSION: XMAX (IN) . . . . . . . 0.512
XMAX (MM) . . . . . . 13.00

Thank you
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post #9 of 20
12/4/12 at 1:32pm
Quote:
Originally Posted by jayHRC51 View Post

Bill, that's an excellent question. I'm not quite sure what the Qtc of the cabinet is.
Speaker modeling software would tell you. If you're going to build your own you need to learn how to use it.
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post #10 of 20
12/4/12 at 3:00pm
Thread Starter 
You're right, I should learn more about the software!

I have WinISD but I'm not very proficient at it. I can enter all the data and build a box, but I have no idea how to really use the program to its fullest... That said, I just entered all of my specifics into the program and it gave me a Qtc of 0.61. Is that good or bad?
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post #11 of 20
12/4/12 at 4:39pm
Quote:
Originally Posted by jayHRC51 View Post

You're right, I should learn more about the software!
I have WinISD but I'm not very proficient at it. I can enter all the data and build a box, but I have no idea how to really use the program to its fullest... That said, I just entered all of my specifics into the program and it gave me a Qtc of 0.61. Is that good or bad?
It's a bit on the low side, indicating a too large box. The result is lower extension than the 'ideal' .707, with lower sensitivity in the passband as a result. OTOH that low a Q would reduce boom. BTW, with that driver Qts of .39 it would probably be best in a ported cab.
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post #12 of 20
12/5/12 at 3:37am
Recommended sealed enclosure size for those subs is 1.25 cubes per driver. So the box is likely too large. Can you try putting a block of heavy wood in there, to reduce the size by a cubic foot?
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post #13 of 20
12/5/12 at 7:01am
Related questions. I came across this old post referencing a Tom Nousaine study which suggests:
Quote:
Stuff small enclosures – those with up to about 3 cubic feet of internal volume or less – with 1.5 pounds of fiberfill for each cubic foot of internal volume and you should get about a 30-percent increase in box volume without seriously affecting other performance variables. For larger enclosures, add stuffing at a rate of approximately 1 pound per cubic foot and you should get a virtual-space boost of about 25 percent. One thing's certain:

1) Is this sound information?

2) If I want to aim for the .707 from WinISD - let's say it is 4 ft³ - if the above is true, I could make a box with 3.2 ft³ net, and add 3.2 lbs of stuffing, for a theoretical increase to 4.0 ft³. It appears that folks often build their box according to the model, and THEN add polyfil. If gains in apparent size can be so significant, shouldn't that be part of the design from the start?
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post #14 of 20
12/5/12 at 7:19am
Quote:
Originally Posted by baniels View Post

1) Is this sound information?
No. Nousaine's data was incomplete, leading to inaccurate assumptions. He didn't measure the Q, or the speaker impedance curve, nor did he compare a larger box with the same Q as a smaller stuffed box. That would have revealed the two to have different responses.
Quote:
2) If I want to aim for the .707 from WinISD - let's say it is 4 ft³ - if the above is true, I could make a box with 3.2 ft³ net, and add 3.2 lbs of stuffing, for a theoretical increase to 4.0 ft³.
No. You may achieve the same Q as a larger box but you won't realize the same response as a larger box.
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post #15 of 20
12/5/12 at 8:00am
Thanks, Bill. I was hoping you'd chime in. So for a sealed box, would you recommend building for a net volume that yields a .707 Q, and then add stuffing to further lower the Q? I guess what I'm after is how to determine the amount of stuffing - or model for an amount of stuffing - when one does not have WT3 or it's latest evolution.
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post #16 of 20
12/5/12 at 10:32am
Thread Starter 
I built my boxes a little on the large side based on recommendations for the amount of power I was throwing at them. I was told that if I used an amp with more power than my Crown XLS1500, then I should build to a smaller spec. Something more in line with the 1.25 or so size.

By the way, this is really good info, thanks for sharing Bill. I'm thinking about a new ported build for these subs and I may lean on your expertise when I do. I was also thinking about doing a horn from your site but I haven't decided if I want to get more drivers and give up the space required. I'm too busy with Christmas coming up to start building new boxes right now though. I just wanted to see if I could make any improvement to my current setup.
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post #17 of 20
12/5/12 at 10:55am
Quote:
Originally Posted by baniels View Post

Thanks, Bill. I was hoping you'd chime in. So for a sealed box, would you recommend building for a net volume that yields a .707 Q, and then add stuffing to further lower the Q? I guess what I'm after is how to determine the amount of stuffing - or model for an amount of stuffing - when one does not have WT3 or it's latest evolution.
I'd go for a .7 Q and line it unless after measuring the cab the Q turns out higher than it should be. This assumes of course that the driver models best with a .7 Q in a sealed cab. Ultimately it boils down to getting a desired result, and that doesn't always mean having an 'ideal' Q. Unless you have a WT3 or the equivalent you can't measure Q anyway. In that case measure frequency response, and if you have a response bump try adding stuffing until it either comes down to acceptable or you can't stuff the box any more.
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post #18 of 20
12/14/12 at 7:26am
Quote:
Originally Posted by Bill Fitzmaurice View Post

I'd go for a .7 Q and line it unless after measuring the cab the Q turns out higher than it should be.

What is your preferred material for lining a sealed cab?
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post #19 of 20
12/14/12 at 11:44am
Quote:
Originally Posted by baniels View Post

What is your preferred material for lining a sealed cab?
I use foam, polyester batts, felt carpet underlayment, type 700 rigid fiberglass, with no special regard to which other than I have it on hand. If I'm stuffing it then it's polyester batts or pillow stuffing.
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post #20 of 20
12/14/12 at 11:45am
Thanks, Bill.
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