I'm getting ready to build my 22 liter vented Tritrix towers, and I'm still a bit confused as to the best way to go about stuffing and/or lining the walls... I've heard different recommendations from different people, so I'm a bit lost...
The towers I'm making are about 33" tall with an 8" internal depth... the vent is in the back wall directly behind the tweeter (the Tritrix is an MTM design)... the drivers obviously are up towards the top of the towers.
What's the best way to stuff and/or line the walls of these things? I've heard recommendations of a few different approaches...
Just stuffing? How much? What kind? I was thinking the PE acousta stuff (or whatever it's called)
I've read that I should avoid stuffing behind the drivers... how much clearance behind the drivers should I leave? All the way to the back wall?
One approach I was considering, since the internal depth is only 8", was to use some eggcrate foam on the back, sides, and top in the upper section of the towers where the drivers are (and no stuffing in the upper area, that way I don't have to worry about stuffing interfering with the drivers and port)... and then use stuffing in the lower area of the towers, below where the drivers and port are... sound like a plan?
Other suggestions?
here's the design... for those of you who were following the progression of my design here, yes I did back off of the curved back walls... a buddy of mine who makes acoustic guitars from scratch informed me that I'd be in for a world of headaches trying to make those curves... so I've gone with a simpler design here...
Unless that is accounted for in the crossover (a redesign) they won't sound as Curt intended.
What happens, is the acoustic centers of the drivers is off, and the way they sum in the crossover is changed. You can angle them, but it has to be acounted for in the crossover.
Thou shalt not stuff vented boxes. Not without a good reason, anyway. Stuffing changes the apparent size of the box, and it's not all that easy to calculate by how much. Acoustic foam does it, too, but by a much more fractional amount.
Your best bet is to line the back wall and DEFNINTELY the bottom of the cab since 33" is a significant distance and can cause a strong resonance (lest you unintentionally build a MLQW transmission line box). Use a nice thick foam. And possibly two layers on the floor of the cab.
Unless that is accounted for in the crossover (a redesign) they won't sound as Curt intended.
What happens, is the acoustic centers of the drivers is off, and the way they sum in the crossover is changed. You can angle them, but it has to be acounted for in the crossover.
Greg
Hmmm... Curt said it wouldn't be a problem.... it's only a 4 degree tilt... you really think there will be a problem?
Also, note the false floor... the floor is parallel to the top, if that makes any difference.
Thou shalt not stuff vented boxes. Not without a good reason, anyway. Stuffing changes the apparent size of the box, and it's not all that easy to calculate by how much. Acoustic foam does it, too, but by a much more fractional amount.
Your best bet is to line the back wall and DEFNINTELY the bottom of the cab since 33" is a significant distance and can cause a strong resonance (lest you unintentionally build a MLQW transmission line box). Use a nice thick foam. And possibly two layers on the floor of the cab.
Ok, now I'm totally lost
I've got Deward Hastings recommending that I stuff the living hell out of them, Curt telling me to stuff them but only moderately, you telling me not to stuff them at all, but rather to only line them...
help?
BTW, note the false floor inside... the internal volume doesn't go all the way to the floor.
I've got Deward Hastings recommending that I stuff the living hell out of them, Curt telling me to stuff them but only moderately, you telling me not to stuff them at all, but rather to only line them...
help?
BTW, note the false floor inside... the internal volume doesn't go all the way to the floor.
You've hit upon the crux of the matter. No one really seems to agree on this point.
I've also tried to come to a conclusion based on other's opinions, and fallen flat.
I would always, always yield to Curt.
I wasn't aware he said it would be okay.
Alot of what I know about speaker building I have learned from Curt. He is far, far more knowledgeable and has infinite more experience than I.
I'm glad you're making progress, and you have such a good mentor (Curt, not me) watching over your shoulder.
Greg
Thanks Greg...
Still completely lost on the whole to stuff or not to stuff question...
So I think I'll do this: Line the back wall and bottom with thick eggcrate foam... then experiment with stuffing and see what I like better (the ole' try it out and see approach... what a concept, eh? )
But since you had asked, I responded. See attached.
It's kind of hard to model the exact changes one can expect by messing with the box Qa (absorbtion losses). More, it's hard to quantify just exactly what different materials will equate to what Qa. But here's my stab:
Green trace: Qa = 80. Should be similar to acoustic foam on walls.
Cyan trace: Qa = 20. Should be similar to light stuffing. Say, 10oz per box.
Orance trace: Qa = 10. Should be similar to heavy stuffing.
Absorbtion increases the apparent box volume. If you make a box bigger while keeping the port length exactly the same, you are in effect lowering the tuning of the box. After making this image, I added one more trace and noted that the orange trace very closely matches the output of the box should the tuning be dropped much lower.
*shrug* Again, this is all just what I simulated. As designer, Curt wins.
So I think I'll do this: Line the back wall and bottom with thick eggcrate foam... then experiment with stuffing and see what I like better (the ole' try it out and see approach... what a concept, eh? )
Best plan of all! Make sure to give the woofers time to break in and make sure to live with the speakers for a week before changing the stuffing. Be really sure you're familiar with what you're hearing. It'll make your stuffing changes easier to hear.
As some have noted...I don't use Acousta-Stuf or dacron stuffing for vented boxes, but DO for sealed. For vented, I line with the egg-crate foam on all interior walls and forego the stuffing. Listening tests I've done seems to be in line with this method, but I have no measurements. I'd line the walls w/acoustic foam, maybe try some stuffing in the bottom, listen a bit and add/remove to see if you hear any changes for better or worse. I don't think 4 degrees of angle will affect the SQ to the point that you'll hear it. That's a nice looking design, can't wait to see the end result!
John A.
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As some have noted...I don't use Acousta-Stuf or dacron stuffing for vented boxes, but DO for sealed. For vented, I line with the egg-crate foam on all interior walls and forego the stuffing. Listening tests I've done seems to be in line with this method, but I have no measurements. I'd line the walls w/acoustic foam, maybe try some stuffing in the bottom, listen a bit and add/remove to see if you hear any changes for better or worse. I don't think 4 degrees of angle will affect the SQ to the point that you'll hear it. That's a nice looking design, can't wait to see the end result!
John A.
Thanks John,
Eggcrate foam: 1.5" thick or 2.5" thick?
I don't mind spending an extra few bucks on the 2.5" if you think it's better...
+1. Be sure to line it all. In a reflex the purpose of lining is to prevent midrange reflections back to the cone and/or out the port. Stuffing is used in a sealed cab to lower system Q, and in a TL to suppress harmonic resonances above the pipe frequency. In a reflex cab stuffing usually does more harm than good.
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Re: Stuffing and/or lining my Tritrix towers...
Originally Posted by billfitzmaurice
+1. Be sure to line it all. In a reflex the purpose of lining is to prevent midrange reflections back to the cone and/or out the port. Stuffing is used in a sealed cab to lower system Q, and in a TL to suppress harmonic resonances above the pipe frequency. In a reflex cab stuffing usually does more harm than good.
Bill, I fail to see why the effects of stuffing would be inconsistent when properly incorporated into two 4th order enclosures, one reflex, one TL. Perhaps it has more to do with the appropriate placement (and the opportunity to place it appropriately) than anything else.
My experience is that lining the walls with foam does little to ameliorate standing waves, which I find very audible. Different enclosures may require different solutions, and no one type or application of stuffing/damping will be optimal for every possible example of a particular enclosure type.
Use the force young Jedi -uh, Lunchmoney... Your ears will guide you...
Is that because of maximum wave velocities? Don't wall treatments have the same problem? I often hear that hanging a absorber panel out a few inches from the wall can greatly improve its effectiveness.
Bill, I fail to see why the effects of stuffing would be inconsistent when properly incorporated into two 4th order enclosures, one reflex, one TL. Perhaps it has more to do with the appropriate placement (and the opportunity to place it appropriately) than anything else.
My experience is that lining the walls with foam does little to ameliorate standing waves, which I find very audible. Different enclosures may require different solutions, and no one type or application of stuffing/damping will be optimal for every possible example of a particular enclosure type.
Use the force young Jedi -uh, Lunchmoney... Your ears will guide you...
C
Thanks Curt... gonna line all of the walls with 1.5" eggcrate to start with, then play around with stuffing... the stuffing is easy to add/remove after it's all glued together... the foam, not so much.
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Re: Stuffing and/or lining my Tritrix towers...
Originally Posted by Dirk
Is that because of maximum wave velocities? Don't wall treatments have the same problem? I often hear that hanging a absorber panel out a few inches from the wall can greatly improve its effectiveness.
My experience is that lining the walls with foam does little to ameliorate standing waves
C
If a cabinet dimension is long enough to allow standing waves to develop it's true that lining alone won't suppress them, and that stuffing is probably required. But stuffing also messes with system Q, and not always in a good way, which is why it's generally best avoided in reflex systems. The preferred method of dealing with standing waves is to configure the inside of a tall cabinet with baffling that eliminates dimensions long enough to allow standing wave development, and that baffling can also do double duty as bracing. The alternative is to take advantage of a cab tall enough for useful 1/4 wavelength resonance and make it a TL.
If a cabinet dimension is long enough to allow standing waves to develop it's true that lining alone won't suppress them, and that stuffing is probably required. But stuffing also messes with system Q, and not always in a good way, which is why it's generally best avoided in reflex systems. The preferred method of dealing with standing waves is to configure the inside of a tall cabinet with baffling that eliminates dimensions long enough to allow standing wave development, and that baffling can also do double duty as bracing. The alternative is to take advantage of a cab tall enough for useful 1/4 wavelength resonance and make it a TL.
Interesting... so what would you recommend for this design?
Stuffing and/or lining my Tritrix towers...
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