posted
My qustion is a fairly simple one, but i'd like a the most detailed answer someone can give: When building a ported box for multiple subs (3 in this case), is it better to build it with one shared chamber, or separate them? I'm not worried about what would happen if a sub blew (besides, wouldn't that be good when it lowered the tuning freq?).
For sound quality reasons, which is better, and why?
I'd like to do a shared chamber, so i can use only 2 ports instead of 3, but i don't want to sacrifice sound quality or SPL.
posted
You wont see any difference in sound, but you can only do common chamber if your running the subs mono, not in stereo mode, otherwise it will mess them up, so Ive heard. Oh and sound quality and SQ are the same thing Posts: 149 | From: Columbia University Med School | Registered: Dec 2002
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I'm going to add another question: What is wrong with porting into the cabin? Do you think i will get cancellation? If so, how can i reduce/eliminate it?
My ultimate problem is trying to make a box with a face that is only about 40 inches wide and 14 inches tall fit 3 12" subs and a port that will be big enough not to whistle like a damn train. I'm hoping for around 40sq.in.
posted
what do you mean by "porting into the cabin"? where is your box going? in the trunk i'm assuming...so you want to fire the subs which way, into the cabin or trunk?
never put the port on the opposite side of the box as the subs unless you are a fan of cancellation...the only way to really reduce that is to fire the subs into the cabin as well and seal them off from the trunk so all the sound stays in the cabin.
you can move the box around in the trunk but will always have cancellation if you do it the way i think you're talking about (subs fire back, port fire forward)...you'll just change the frequency that the worst cancellation occurs at.
you can put the port on the side of the box however and be ok
40in^2 comes out to about a 4" round port per sub...definitely wouldn't go any smaller
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--------------------------------- Loud...it's when you can see the ground move, it's when you have to force yourself to breath, it's when the rest of the world ceases to exist. Posts: 4136 | From: Lafayette, LA | Registered: Sep 1999
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posted
I meant to have the subs fire towards the rear of the car, but have the port going up through the rear deck. I wouldn't put the port on the opposite from the subs, but how much of a difference does the side make? I'm sure it would normally be less than optimal, but would it have a huge affect if it was going right into the cabin, whereas the subs are firing into the trunk?
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Looking for the following: Image Dynamics IDMAX 12" Crossfire BMF1000d or VR1000d Posts: 48 | From: Buffalo | Registered: Oct 2002
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posted
putting the port on the sides prob own't have a huge impact on output provided you allow the ports enough clearance to "breath" properly. That would be at least the diameter of the port...preferably more, from the port to the nearest surface.
as for porting thru the rear deck and firing backwards...not sure, haven't tried mine that way. had mine firing forward from behind the rear set (sealed off from the trunk) and ported thru rear deck. Three 12's that is...just like what you wanna do, and they were hittin decently hard for 300W total. Never metered it legal, but was about a 141 or so (did a 145 outlaw and my car tends to be 3dB down from that on the dash).
if i were you i'd try that if yuo're gonna port the rear deck anyway. You won't have all that air in your trunk to pressurize so it'll be more efficient. And seats up it will still be decently loud and maybe sound a slight bit better at high volumes because of the "filtering/muffling" effect of the seat foam...
-------------------- "Those who give up liberty for the sake of security deserve neither liberty nor security" - Benjamin Franklin
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Elemental Designs
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--------------------------------- Loud...it's when you can see the ground move, it's when you have to force yourself to breath, it's when the rest of the world ceases to exist. Posts: 4136 | From: Lafayette, LA | Registered: Sep 1999
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posted
my buddy has an 03 nissan sentra spec v, he runs a mtx blue thunder extremem 10 in a ported box with a 3 inch port going up to where his factory sub went in the rear deck...it sounds ok...not too loud but sounds boomy......
-------------------- Jon Elia 2-12w3v2's 1-jbl 1200.1 hope to change the subs soon
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DIrTy SoUtH DEAF SQuAD Posts: 257 | From: longview texas | Registered: Mar 2004
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posted
OK, there are advantages to both. Running a common chamber, like stated above, will let you have more port area, and a little more volume. But, running individual chamber will raise the resonance frequencies of the box above the range a subwoofer is played at.
Say you have a 4 foot wide box, thats 1/4 wave of (I think) of 70 Hz, that will effect the sound of a sub box, but dividing it will raise the resonance to 140 Hz, which in most cases will not effect the sound.
quote:Originally posted by tucked65: OK, there are advantages to both. Running a common chamber, like stated above, will let you have more port area, and a little more volume. But, running individual chamber will raise the resonance frequencies of the box above the range a subwoofer is played at.
Say you have a 4 foot wide box, thats 1/4 wave of (I think) of 70 Hz, that will effect the sound of a sub box, but dividing it will raise the resonance to 140 Hz, which in most cases will not effect the sound.
yep but dont divide it in half,divide it unequally so that the resonances dont sum-at 140hz it woudnt matter though.
other than this point,the two choices are very similar.
posted
For SPL, I would say that separate chambers would be better.
1. No in-box interactions between drivers that don't match means less cancelling
2. More panels = more rigidity to box = less box compliance = more emitted sound energy
3. A port for each driver
For SQ, there is almost no question: You need to tune low, and it is easier to tune a larger chamber lower, so you combine the two. However, you should do at least a rudimentary matching of drivers if they are to share a common space.
ShadowStar
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It's all about knowledge, love and respect. Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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