Jackseric

iTrader: (1)

I've been planning to build the DIY hidden enclosure someone posted on this board a while back. (the one where you relocate the spare under the car) In the DIY it mentions the boxes are fine for 12s. I am only planning on dropping in either my 2 10" RF or my 2 10"Vegas that I have sitting in a closet. Each calls for only a 1 cubic foot box. Will the bigger box be a problem, or degrade the ability to play?

mohawkboom

iTrader: (1)

nope..a bigger enclosure is generaly a better thing.. it may reduce power handling a little bit..but otherwise it's nothing to worry about...also you can always add wood blocks to decrease the volume of the enclosure

WhiteRabbit

in my experience, drives are far more sensitive to overlarge boxes than oversmall boxes. we built a box to demo 4 12's at my shop, but made it a little over a cubic foot too big. sounds horrible and doesnt get loud at all. we plan to eventually fill the box untill its the ideal size to see if thats any better.

other than that, we put 4 12's in a budie's volvo 240 (pics used ot be floating around here of it) we put the woofers in 5 cubic feet which was great for low ported applications, but when we went to sealed or ported high, the response went way out teh window.

this is all of course only personal experience/opinion, but any QTC between .78ish or so to 1.3ish or so sounds absolutely awful. ideal qtc is root2/2, or .707, but many manufacturers make their woofers perform oddly (compVR is a great example) where they perform best with a rediculously high Q. if you try modeling up that woofer, youll see that it wants 17ish cubes sealed. manufacture specs put it about 1.31 qtc, which works a hell of alot better than if you just run it in the biggest sealed box you can.

i would highly reccommend agasint running an overlarge sealed box, or an oversmall ported box. i experiemnted with a small ported box for a pair of junk 10's i have lying around, and it was a terrible sound, i ended up turning them off for my 3 hour drive across the state.

maybe you will have a different experience than me, but i have yet to run an overlarge box that sounded good.

slikor

iTrader: (1)

i have a Alpine SWE-1041 Type-E 10" sub that i just bought, and i made a custom sealed box for it with an internal volume of around 0.5 ft^3 (~ 847in^3). the manufacturer says the sub's recommended sealed box volume is from 0.6 to 1.25 ft^3. now, i tested the sub out (running off a Profile 600MSX mono amp w/ 300W RMS output) in my trunk and it seems to hit well and its sounds pretty clean to me, not too muddy or distorted.

the box is made out of 1/2inch MDF, and i secured the seams with liquid nails then with screws, and sealed it with silicone on the inside. now my question is: was loading the box with polyfill and that it was well constructed what makes it not perform as horribly as i thought it would (and as i read should be the case), or is it in general not such a problem having small box like this?

WhiteRabbit

its not a problem persay, when i got my sony xplods as my very first woofers, i had never heard a good stereo in a car. i thought i had teh best streo money could buy. by was i wrong [IMG]i/expressions/face-icon-small-smile.gif[/IMG]

as i upgraded myself and heard others systems, it opened my eyes to a whole new world or music. chances are (and i mean no disrespect) that if you think it sounds really good, when its *probably* a bit peaky, then its not that your "fine" or "not fine" its just that your response is going to be a bit different than the ideal SQ stereo with a flat response playing acurate recordings.

youll find that we greatly overexxagerate any issues in performance from a woofer cause we know what to listen for, we know what we are trying to hear, and trying to avoid. youd be fine with an overlarge or oversmall box, techincally

back to my shop example, we'd be playing with it and a customer comes in, and hear the box and say holy **** thats so insanely loud, what ARE those woofers?

when i first heard them i had no idea how loud they are supposed to get. i was pretty impressed but my manager who has competed with those woofers was very dissapointed with their output. after hearing his daily driver car, i have to agree. 4 12's and 2000 RMS should get a hell of alot louder than what we have is getting. but does that stop everyone who walks through our front door from getting way impressed? nope. having never heard an ultra high quality stereo, nor hearing what these woofers really can do, they are quite impressed.

and i think thats whats happening here, and in 90% of the threads i reply to. i cant tell you how often i demo my stereo to audio friends and they arent impressed at all. tempests do it for me, but not for many out there. again, same deal.

slikor

iTrader: (1)

awesome, thank you so much for that very helpful explanation, WhiteRabbit. that helps soooo much

i guess i'll just stick with adding my other sub in the same size box, and for now that'll be plenty good enough for me i think

Jackseric

iTrader: (1)

OK... More questions from the ignorant:

1. Polyfill ~ I've read that adding this gives the effect of a larger box. I've also read I should probably line the box with a small amount of this regardless because empty boxes tend to have funky acoustics. Is this true? Won't that further the effect of too much volume in the box?

2. If it sounds horrible, and I can't work out the issues.... is there anything keeping me from dumping the 10s, cutting the holes larger and dropping in a pair of 12s?

WhiteRabbit

i have NO CLUE how poly fill does its job. ive heard the arguments (mo will present them in his next reply) but i see too many holes in them to understand HOW it works.

as to it actually working, try this: play your stereo without it, then stuff the bejesus out that box and try again. does it sound better? if so, keep it [IMG]i/expressions/face-icon-small-smile.gif[/IMG] if not, you can yank it anytime.

and there is nothing keeping you from cutting bigger holes, just liek there is nothing keeping you from putting covers and running a pair of 8's or sealing one hole and running a single 12, or taking it to the beach and flat out burnign the box, etc.

you have to now worry abotu the new response the 12's will have...... but you CAN do it. nothing will stop you.

mohawkboom

iTrader: (1)

Polyfill in principle lengthens the rear pathwaves of the woofer..

The "sound" must travel through and around the fibers in order to reach the rear of the enclosure. The effects low end only by tricking the sub into thinking it's in a bigger box with longer rear waves...

for the physics part of it..I have no idea..

WhiteRabbit

this is what i was waiting for [IMG]i/expressions/face-icon-small-wink.gif[/IMG]

mo, ive asked around, noone knows this, maybe you cna help me. so polyfill lengthens the time it takes for the backwave to reach teh back of the box, simulating a larger box. ok, but the polyfill takes up space as well! it has mass! so doesnt that *technically* DECREASE the airspace inside the box? is it a process of diminishing returs, where the slowing down of the wave is greater than the air they fill physically takes up? explain.

edit: the reason this argument came up is because i was told by a hardcore HT guy that the only way polyfill works at all is if you stuff teh bejezus outta the box. thats alot of polyfill! i cant quote from experience, ive only used either no polyfill, or mass stuffing, but if you mass stuff a box, thats quite a bit of fill! (kinda reminds me of the ideal gas law, works great as a model, doesnt really work out in real world situations.....)

LudlamTheory

stuffing the crap out of it WOULD in essence reduce the amount of airspace... its pure physics, but again, more physics, the polyfill matter is so damn small that a majority of it is just air, but lets say you took a 1 cu ft box and put 6 pounds of polyfill in it, youd probably be dropping the amount of matter it really takes up.... i think im gonna experiment with polyfill some.... take a pound, melt it down into a solid chunk, and measure the amount of volume that 1 pound takes up.....

now im gonna take my stance as a car audio ignoramus and ask a few silly questions.... you gotta learn some how =)

1 - the fact that the wave takes "longer" to get to the back of the box, wouldn't that make the intensity of the wave decrease to to more movement....
2 - if the wave has to go around all this stuff, wouldn't it get deflected around and maybe cancel itself out?

i had another question but i forgot

WhiteRabbit

i stopped caring HOW stuff works a long time ago. [IMG]i/expressions/face-icon-small-smile.gif[/IMG] in the end, if it sounds good, thats what i do. as to what i SHOULD tdo to get it to sound good, i just try everything till its performing at its best [IMG]i/expressions/face-icon-small-wink.gif[/IMG]

and yoru test idea, is a VERY good idea, lud! BE SURE however that you dont exeed the burn temperature of the polymer! heat to JUST above teh melt temperature, or else youll lose a great deal of material as it decomposes or boils away! (ie, lighter wont work well as a heat source ;p) id be GREATLY curious of the results tho.

as to MY definition of "stuffing the bejesus" out of a box, i have half a pount in .3 or less cube kickpanels, and its not enough fill. i should have about a pound in there before im stuffing it to all hell. if youve tried cramming that much crap into that small of a space, youll quickly see where my problem with the theory comes inot play [IMG]i/expressions/face-icon-small-smile.gif[/IMG]

mohawkboom

iTrader: (1)

Okay...after talking to an "expert" here's what I've learned..a little polyfill does nothing.. moderate to stuffing the bajesus has effects..

The polyfill material resonates at a very low frequency, it also takes up space.. 1lbs of polyfill takes up approx .013 cu.ft. It works in 2 ways.. 1 it loweres the internal volume of the enclosure causing the woofer to have a little more "acoustical suspension"

Secondly, the fibers themselves lengthen rear waves as well as resonate at about 30hz...this works almost like a passive radiator but to a much lesser extent..It lowers the overall "Q" and increases low end output.

For kickpanels and higher tuned woofers, Fiberglass has a better effect as it resonates at a higher frequency. But it's a bish to do because you have to pull the fiberglass insulation a part making it more "fluffy" about 3-4 times it's original mass.

For your kickpanels you can greatly increase the apparent size of the enclosures by using an Aperiodic setup. This I have no clue how to tunr, however you can make a .3 cu.ft enclosure behave exactly as though it were about 3 times it's size...

slikor

iTrader: (1)

hmmm, this is all very intruiging...

i have a custom 0.9ft^3 sealed box for my Alpine Type-R 12" Dual 4ohm Voice Coil sub, and i plan to stuff it pretty well with polyfill. i have 2 questions:

1. is stuffing a box full of polyfill going to reduce the of cooling abilities of the air in reference to my sub (e.g. will my sub heat up more because if the polyfill?)
2. do i need to use some kind of adhesive on the walls to make the poly fill sort of stick, or should i stuff the box so full there is no room for movement? [IMG]i/expressions/face-icon-small-wink.gif[/IMG]

WhiteRabbit

#1 no clue, but if the answer is yes, it will still be WAY under the tolerance for the woofer. not a concern at all

#2 no glue is neccesary, cause stuffing the bejesus out of teh box implies that there will be no room for movement.