Subs, Ported, Sealed, Bandpass and size?

[Rdubois]

Ok here is the problem. Hopefully someone can explain this to me. I currently have two A/D/S 10" in a sealed box that holds both. It is a .88cuft box which is what they are suppose to be in. It is my understanding that if you go with a little bit bigger of a box the amount of bass will increase but I will lose some SQ. That is fine since I'm looking to add alot in the Fronts and rears. My question is, I was looking at boxes on ebay and liked a few. Some sealed and others bandpass. I've heard that A/D/S subs are primarily a sealed box sub. What is the difference between the two and would SQ be HORRIBLE if I put them in Bandpass boxes. Also if that were to happen would I have to look for different size boxes and how big of a difference in size can you go before having it sound like ****. Anyone with knowledge on the subject any help you can give would be appreicaited.

[Atomic]

Basic differences between sealed and ported boxes:

Sealed(recommended): Smaller box size required for speaker(s), crisp & clean bass produced due to sealed enclosure(less speaker excursion, always good), easy to build/tune, narrow frequency range response (20-120hz normally).

Ported(not recommended): Larger box size required for speaker(s), sloppy bass due to flutter at higher volumes(more speaker excursion, most times bad), have to tune ports to box size/speaker requirements, wider frequency response (50-300hz normally).

Here's what I would do, try cranking up the gain on your amp to the point of distortion, then back off a notch, if you haven't already. Also, depending on the frequency range of the speakers, you can retune the box you have with some poly-fill. I wouldn't add more than a half pound of poly-fill to each sub box hole, you won't hear the difference above that. This will basically fool the speaker into thinking there's more air in the box(like a ported, but not), giving you a wider frequency range and you'll be able to push those speakers a little bit harder to get that louder bass your after, and without as much risk of blowing them like in a ported box.

[Rdubois]

Thanks for the advice. I was planing on sending about 100 to have to separate boxes but I'll probably just put that towards a 10-15 farad cap now. Thanks again. I'll buy some poly fill and try that out. P.S where can I find that?

[Atomic]

Here ya go:

http://www.crutchfield.com/S-2lFa2zKBByR/cgi-bin/ProdView.asp?i=027808&search=poly+fill

[joeypasta]

You can also find polyfil at a fabric or craft store.

[NorthernYankee]

Atomic I don't know where you get your info but its really off base on some things, this is not meant to bash you its just that I see a lot of misinformation out there and you just happened to post it. Hopefully this topic will help a lot of people make more educated decision on box design. Now I don't know if you put the "recommended/Not Recommended" specifically for his subs or just as a general comment...hopefully you meant for his A/D/S subs.

Basic differences between sealed and ported boxes:

Sealed(recommended): Smaller box size required for speaker(s), crisp & clean bass produced due to sealed enclosure(less speaker excursion, always good), easy to build/tune, narrow frequency range response (20-120hz normally).

Yes it can be a small box size for sealed but there are many sealed set-ups with box sizes well over 2 cu ft, Yes you will get a "Tighter bass" due to the damping effect of the sealed enclosure...Now whats really off base is the speaker excursion. Speakers in a sealed box actually actually have a higher excursion as the frequency gets lower. Yes they are easier to build/tune since its just a big closed box. Now for the frequency range...20-120 is narrow? 98% of all subs are or should be crossed over below 85-90 hertz because anything above that the human ear can pick up the direction of where the sound is coming from and that ruins your imaging.

Ported(not recommended): Larger box size required for speaker(s), sloppy bass due to flutter at higher volumes(more speaker excursion, most times bad), have to tune ports to box size/speaker requirements, wider frequency response (50-300hz normally).

In general yes ported can take up more space but not always. Flutter at high volumes? I believe you are refering to Port noise at high volume and yes a poorly designed port will do that but that is not a flaw of a ported box but a poorly built box. Now as for the excursion a ported box has an extremely low excursion above the tuning frequency of the box because the port actually controls the excursion...now you will have to use a subsonic filter set approx 2-5 hz below the tuning frequency of the box because below the tuning frequency excursion does increase immensely. But a ported box can be tuned to say 30-35 hz to still give you a good amount of low bass with minimal loss below that. Lastly a wider frequency response 50-300hz? Again cross over at 85-90hz as a baseline. And unless you are building a box specifically for SPL you wont tune it at 50hz, it would be more like 30-35 with a frequency response of 30-90.

Here's what I would do, try cranking up the gain on your amp to the point of distortion, then back off a notch, if you haven't already. Also, depending on the frequency range of the speakers, you can retune the box you have with some poly-fill. I wouldn't add more than a half pound of poly-fill to each sub box hole, you won't hear the difference above that. This will basically fool the speaker into thinking there's more air in the box(like a ported, but not), giving you a wider frequency range and you'll be able to push those speakers a little bit harder to get that louder bass your after, and without as much risk of blowing them like in a ported box.

Yes poly-fill can help but I don't feel its to the degree he is looking for...And you analogy of more air like a ported box, hows that? Ported boxes can be smaller than sealed. Poly-fill works by increasing the temperature inside the box thus making the warmer air a little thinner thus reducing resistance to movement. And just because a sub is in a ported box does not mean you are going to blow it...most of the blown subs you see from ported boxes is becuae of a poorly built box/lack of a subsonic filter...which are both human error not the fault of a ported box.

And chosing a sub for what you want is just as important as choosing the right box...putting a sub designed for a sealed box into a ported box is bad and vice versa.

--NY

[hyunelan2]

On the topic of polyfill, I bought brand-name "polyfill" last week. 20 oz for $2.50 at Walmart in the craft section. (It's for my home subwoofer). Crutchfield will charge you 4x that for the exact same stuff.

[Atomic]

I did make a GENERAL comment based on my experiences in the past. I actually read what he was asking, and based my answer off of that. I didn't post help to have it picked apart, whatever. Next time try adding just your knowledge and not flog someone else for helping out a fellow member, whether you think the knowledge is "flawed" or not.

Oh, and good find on the polyfill hyunelan2.

[kylemorg]

By the way, most cheap bandpass and ported boxes I've tried have not sounded good.

The only one I've used that had both deep and accurate bass is one I got at circuit city on a closeout. It was a 10" JBL GT-series sub in a bandpass box about 12"X12"X2.5' (~1/3 sealed, 2/3 ported). I still have it and I'll probably eventually put it in my wife's car. It really pounds with only an Infinity Beta Digital 300W amp!

I tried some smaller 12" sub boxes, including a single 12" ported "truck box" and one of those black carpet and plexiglass-covered small 12" bandpass boxes with the two big chromed plastic ports in it. Neither the 12" ported enclosure nor the 12" bandpass speaker box had accurate frequency reproduction, just boomy, muddy bass.

You can sometimes get Kicker Comp VR boxes fairly inexpensively on Ebay. The one I got was for dual 12's, but I think they make single 10 and 12's and dual 10's as well. The Kicker box a nice tight sealed unit.

Just thought I'd put in my $0.02...

:)

[NorthernYankee]

Atomic I am sorry I upset you...but I said I was not trying to bash you...I was trying to correct misinformation.

Take one of those Electric Superchargers for example...a lot of people ask about them. Now say someone says oh yeah they are great they give 50HP. Now should everyone just agree with that person just so that person does not feel bad...or should he be corrected and given the correct information so in the future he knows.

My point was to get "correct" information out and not misinformation. I would rather be corrected and learn true information than to think something and have it be wrong.

Again I am sorry if I offended you.

[southpawboston]

Poly-fill works by increasing the temperature inside the box thus making the warmer air a little thinner thus reducing resistance to movement.

NY, your advice is pretty good except for that above statement. poly fill (or other insulation like fiberglass) works by reducing the amound of soundwave reflection that occurs within the resonance chamber (the box). according to your logic, a non-poly filled box will sound like a larger box at warm ambient temps than a poly-filled box at low ambient temps. that is just not true. also according to your logic, the same effect would occur at high altitudes, which also isn't true.

however it is true that a sealed box does cause more resistance to movement, which reduced the efficiency of the speaker, but increases its power handling and also increases its q (a measure of how quickly a driver can mechanically respond to changes in the signal).

[2loud2k2xd]

Thanks for the advice. I was planing on sending about 100 to have to separate boxes but I'll probably just put that towards a 10-15 farad cap now. Thanks again. I'll buy some poly fill and try that out. P.S where can I find that?

what do you need with a 10-15 farad cap? the general rule of thumb is 1 farad per 1k watts. i only have a 3 farad cap in my set-up. but i also have a dedicated 1125cca yellow top for the system.

[NorthernYankee]

NY, your advice is pretty good except for that above statement. poly fill (or other insulation like fiberglass) works by reducing the amound of soundwave reflection that occurs within the resonance chamber (the box). according to your logic, a non-poly filled box will sound like a larger box at warm ambient temps than a poly-filled box at low ambient temps. that is just not true. also according to your logic, the same effect would occur at high altitudes, which also isn't true.

however it is true that a sealed box does cause more resistance to movement, which reduced the efficiency of the speaker, but increases its power handling and also increases its q (a measure of how quickly a driver can mechanically respond to changes in the signal).

You're right Southpaw my Logic was flawed on that one...by doing some searching I did find this info just now

"Damping material changes the operation of the box air from adiabatic (constant heat) to isothermal (constant temperature). With the isothermal process, the damping material absorbs and gives up heat which maintains a more constant temperature inside the box. This also has the added effect of reducing sound velocity, which shortens the wavelengths and makes the driver "think" it is in a larger air volume."

I found that here http://diyaudiocorner.tripod.com/faq.htm

Thanks for the info SPB