View Full Version : two different box types?
02-25-2003, 11:08 PM
is it ok to have, say, four subs total but two of them are in single sub sealed boxes and two of them are in a two sub bandpass or iso push/pull bandpass (total of three enclosures)?
i didn't think there would be, but i was just making sure that they wouldn't be producing different sound waves that might interfere with eachother or anything like that...
02-26-2003, 12:56 PM
if you of yoru subs were in single sealed 1.25 cube enclosures.... and two were in a "dual" sealed 2.5 cube enclosure, they're gonna sound the same...
but... two bandpassed subs and two sealed subs willl not sound hte save.... its a totally difft response curve, and mixing subs mounts like that will probably sound like ****.
02-26-2003, 09:13 PM
really? i thought that maybe having sealed boxes would kind of "fill in" the lack of accurate tight bass when you hear it and the bandpass would give the powerfull bass....it doesn't work like that?
mixing enclosure types is bad news?
and also i've heard that mixing sub sizes is bad magic as well...any truth to that?
02-27-2003, 03:14 PM
mixing sub sizes is "bad magic" as you say if done "blazee" ...
if you just wire up two 10's and 2 15's both running from like 20 hertz to 100 hertz or whatever, you're in deep doo-doo.
if you however wire two 15's at 0 to 50 or 60 hertz... and two 10's from 50 or 60 up to 100+, you will in fact (if tuned properly) get a fantastic sound.
same goes for 12's and 8's... 0 - 70 on the 12 // 60 or 70 to 140 or so on the 8 and u've got a good mix.
that's how u "fill in" ... ghetto rigging difft boxes may work if only by the nature of sheer luck... i doubt there's any way u'll get it to consistently perform well though.
02-27-2003, 05:09 PM
you mentioned pairing 15's with 10's and 12's with 8's.....would it be bad to pair 12's with 10's?
02-28-2003, 06:43 PM
well... see.. the idea of pairing a 15 with a 10 is that the 15 hits much lower w/ accuracy than th 10.. and the 10 hits higher a/ accuracy than the 15... so u cross them over and run them independently.
12's and 8's go the same way --- the 12 hitting lower.. the 8 higher.. each accurate in its own freq range.. 12's and 10's are too close to gether in response range to make it WORTH pairing them together... u can try -- definatly not worth your time though...
you'd be xing the 12's at like 0 - 65 hertz and hte 10's at 60 to 90 or 100... it'd prolly sound the same as one good 10 or one good 12.
... def not worth the time/effort of building crossovers for subs and all that ****.
if you ran them both "full range" of 0 to 100 or 0 to 80, they'd sound funny together me thinx.
03-02-2003, 11:31 PM
ok thanx....and btw i think you're the most helpful overall person i've spoken with on these forums, pbd...thanx for all of your help
03-02-2003, 11:52 PM
Well, I have to inteject something here. I would not pull off the diff enclosures with Polk subs. They will no respond the way you are thinking. However, I did do a box with a bandpass and a sealed enclosure for 2 different subs. One in the bandpass and one in the sealed.
It filled in nicely and gave alot of boom from the bandpass but under tolerable listening levels, the sealed enclosure performed very well with emphasis from teh bandpass so well fitted that there was no need for a bass boost or loud button of any kind to be instituted. However, I did use Pioneer IMPP woofers that worked well in sealed or ported enclosures. I imagine that had alot to do with it.
03-03-2003, 08:49 AM
steve, no problem.
jstas, heres something thats been buggin me, if u have any idea...
-- the concept of free air.
like i ran my idmaxes with the tops off the boxes at low power for a few days to psuedo break them in - as per the ID guy's reccomendation... now there was like no sound from them.. even when i turned the volume up -- they made very little sound.... but then u put the top on the box and BOOM BOOM BOOM. so i'm not understanding how a free air sub would be any good -- i had 1250 rms on each and got zilch... and this is from a sub that is stated as being "perfectly fine for free air / ported / or sealed use". and i dont mean like "less bass that sealed" or anything like that... i mean like INAUDIBLE... nothing. if u turned off the highs and turned off the engine and listened carefully u could hear something... that was it.
i'm just trying to get an idea, as i keep kicking around the idea of using a free air sub in another car and i want a general notion of how it works / why before i go hacking at it.
03-03-2003, 10:13 AM
From what I know of Free-Air subs, the only company to ever successfully pull them off was Pioneer. Every other sub sounded very weak even if it was over-powered.
The idea behind free-air is that you mount the speaker like you would a pair of 6x9's in the back deck or components in the doors. They use the confined space behind the mounting surface as an pseudo-enclosure, just like your full range.
The free-air designation is a misnomer. Any speaker, aside from ribbon speakers, will make little noise in an open environment. This is because, you need to seperate the front of the cone from the rear of the cone. That is because for every action, there is an opposite and equal reaction. The cone will move out a certain distance but it will also move in the same distance, 180 degrees out of phase. Just like wiring stereo speakers out of phase, a speaker will cancel itself out. Which is why your topless box made no noise. The two sides of the speaker were not seperated.
Now that we understand that, lets get back to the free-air misnomer. There is no such thing as Free-Air. It's properly referred to as "Infinite Baffle". You need a seperate enclosure for it to work. Hence the need to mount the speaker with one end pointing into the cabin and the other end pointing into the trunk or door. The door or deck panels are the seperating baffle and the walls of the door pocket or trunk are your infinite baffle. Kind of a contradition but infinite baffle does not refer to the finite dimensions of an enclosure. What it refers to is the ability of the speaker to control itself rather than using the pressure of the enclosure to give it something to push against and limit movement. Infinite baffle needs only a seperator baffle like the front mounting panel on a typical sub box. However, that mounting plate must extend to the ends of the pseudo-enclosure to seperate the two, no matter how far away they are. Now within reason, you will not need a 1 mile long baffle for a 10 inch sub. However, since it is hard to determine what will be needed as it could be any size, it has a potetial of being infinite. While that is a very diluted way to think of it, it gets the point across. It's not 100% accurate and there is other stuff involved but that is the basic idea. Also, installing a free-air sub in a box will destroy it. You can truncate the space you need to create the free air feel but you would need a large box and large vents. The vents would have to be so large I wouldn't even call them ports.
An infinite baffle speaker is designed differently. Usually it has a super light cone with a more rigid surround and spider. The problems with infinite baffle subs is that the frequency response is truncated in the lower range but greatly expanded in the upper frequency range. Think of it more like a 10 inch or 12 inch mid-bass driver. Most typically have a lower response of 50 hz, gradually dropping off to about 35-30 Hz and then sharply dropping off after that. I mean, like a straight drop down from 30 Hz to 28 Hz. They will extend up to 6,000 Hz in the upper scale in some cases though. They really aren't a sub woofer but due to the sheer size of the speaker, they are capable of semi-extreme bass. Most people use two or three infinite baffle subs in a typical 20-30 cubic foot trunk. It provides plenty of loud boom but no real low end extension. It can also be muddled and inaccurate.
If you are going to use infinite baffle subs, use multiple speakers and max them out on the power. Make sure you mount them so that one side fires into the passenger compartment and the other side into a seperated compartment like the trunk or a door panel. The enclosure can be any size but it cannot be sealed or ported. A door or a trunk is not air tight and works just fine. DO NOT mount the subs to a board and screw them to the back of a seat frame in the trunk. It doesn't work that way, vibrates things loose and ends up destroying your subs as they slam into the seat back repeatedly. Believe it or not, I have seen that done.
So, if space is an issue and all you want is boom, free-airs will work, if you set them up properly. I wish I could give a better explination. It's a very easy concept to understand, just difficult to explain without a visual aid.
03-03-2003, 01:50 PM
actually u did an amazing job of explaining that and i'm in your debt...
i get the idea now... makes sense. and from what u said, i probably will never do a free-air sub... prolly better off doing a sealed and then bolting a box up under the deck.
i've been batting those two ideas around (box under deck versus free air) for over 6 months now... and no one's been able to explain the pro's con's of either to me... least now i understand it and can make an informed decision.
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