tjamz Posted August 20, 2012 Report Share Posted August 20, 2012 Alright..... I read through page 1 on this and had to comment without reading further (sorry if this got covered somewhere else already in this thread): Ported/vented inherently is about 3 dB louder than their sealed counterparts when tuned for optimal sound at the expense of linearity below the F3 point (F3 meaning the point in the tuning frequency where the subwoofer has exhibited a 3 decibel loss per octave). It is strongly recommended that a high pass (subsonic) filter be used at or slightly below the F3 point to help filter out frequencies that are outside of the normal bandwidth of the sub/enclosure combo. Ported enclosures CAN be more than 3 dB louder than a sealed box but this is ALWAYS at the expense of added port noise and/or narrower bandwidth (higher F3). In other words when you build them to be SPL monsters they suck as musical reproduction units. When done properly a vented enclosure will retain excellent musical output throughout its bandwidth, though MOST audiophiles will argue that a sealed enclosure is more "pure" sounding. The "tuning frequency" of the enclosure is the frequency that the port will resonate at. Think of it as a 1 note pipe organ basically. This does NOT necessarily mean that this is the frequency that the sub will be most efficient or that your vehicle will make it's peak SPL, though a properly tuned enclosure CAN be used to maximize output at a given frequency especially if you know the resonance frequency of the vehicle and tune your enclosure accordingly (that is a WHOLE new discussion beyond this). I think that covers the basics of enclosure fundamentals as they pertain to vented/ported enclosures. EDIT: Forgot to add that yes, a bigger port opening requires a longer length to tune to the same frequency.... again, see my pipe organ analogy. Link to comment Share on other sites More sharing options...
vrollin Posted August 21, 2012 Author Report Share Posted August 21, 2012 So I may have effectively wasted my time building this box because I dont know what the port will tune it too? I just made a port with the same cubic volume as the focal specified one. Didnt get the bit about the size of the port opening. FML... Link to comment Share on other sites More sharing options...
Jessica Posted August 21, 2012 Report Share Posted August 21, 2012 You havent wasted your time if you learned from it. Thats the name of the game man. Rest in peace, walled 87 accord build log 03' Corolla build with AA Mayhem inside. My super random youtube channel and terrible camera work. Wiring comparison by CaptainzPlanetz Wire and fuse guide by Guest SyKo13 Link to comment Share on other sites More sharing options...
vrollin Posted August 21, 2012 Author Report Share Posted August 21, 2012 Yeah but I havn't learnt, still don't know how to figure out the port length based on the size of its opening to bring the box to a certain frequency.... My box dimensions are externally, 480mm wide x 320mm tall, bottom is 250mm deep, top is 145mm deep, all using 16mm thick wood. From my calcs I get that as a 21.3L box, approx. Now my port opening is 30mm, and built to match focals recommended .0335cu ft or .948L. Is anyone with one of them programs able to please tell me how big my port depth needs to be to tune to around 30-35hz? I found this; http://www.the12volt...calcs.asp#porsq If I keep going with a port of 30mm wide height 288mm my port length to attain 35hz is 36"? Does this seems right? If it is right, then my port length I have made will tune the box to around 100hz Link to comment Share on other sites More sharing options...
vrollin Posted August 21, 2012 Author Report Share Posted August 21, 2012 My brain is exploding trying to figure out how to fit a port of suitable size into the box design I have to work with, could anyone tell me how small of an opening is too small for a port? Should I expect port noise with say a 2" pipe? Could probably make a port out of some pvc and mould the end so I can attach it...? Link to comment Share on other sites More sharing options...
vrollin Posted August 26, 2012 Author Report Share Posted August 26, 2012 Did a whole lot of research about port opening in relation to length etc, and turns out my understanding obviously was very wrong, sooo after alot of calculations and dicking around have come up with this complicated to build little bastard, port opening may be too small in the end and in turn be noisy, but time will tell, fingers crossed I will have the box all finished up by the end of tomorrow night ready to be trimmed installed the next day and that it will be a great success Link to comment Share on other sites More sharing options...
goldeneye4564 Posted August 31, 2012 Report Share Posted August 31, 2012 Did a whole lot of research about port opening in relation to length etc, and turns out my understanding obviously was very wrong, sooo after alot of calculations and dicking around have come up with this complicated to build little bastard, port opening may be too small in the end and in turn be noisy, but time will tell, fingers crossed I will have the box all finished up by the end of tomorrow night ready to be trimmed installed the next day and that it will be a great success I am curious to see what this is going to sound like I RREEALLY ANGRY WIT U PHOTOBUCKET. HAD TO USE DROPBOX NOW HOLYYYYYY. Wanna ride bikes? Quote On 9/16/2017 at 3:28 AM, Jake Pace said: Oh i know how a 12v system works I did take 3 years of electronics in High school hands on and some in college and also worked on cars in college an always got A's to B's in each class. But oh well enough dealing with ppl who have probably not even lived as long as ive been into electronics! On 7/8/2013 at 4:01 AM, Banshee421 said: Do horns get low Link to comment Share on other sites More sharing options...
vrollin Posted September 1, 2012 Author Report Share Posted September 1, 2012 Realised I didnt update, have one of the boxes in now, overall seems to be doing the job, can feel the sub kick harder now and is almost as loud as having the two running before, also I cant hear any form of port noise, well havnt noticed it if it is there... So now gotta make another box for the passenger side so I can get the two running asap and clean the interior after months of neglect while im at it Link to comment Share on other sites More sharing options...
goldeneye4564 Posted September 1, 2012 Report Share Posted September 1, 2012 right on glad it worked out ok. I looked at that port and was like smallllll? but if it works well thats all that matters man! I RREEALLY ANGRY WIT U PHOTOBUCKET. HAD TO USE DROPBOX NOW HOLYYYYYY. Wanna ride bikes? Quote On 9/16/2017 at 3:28 AM, Jake Pace said: Oh i know how a 12v system works I did take 3 years of electronics in High school hands on and some in college and also worked on cars in college an always got A's to B's in each class. But oh well enough dealing with ppl who have probably not even lived as long as ive been into electronics! On 7/8/2013 at 4:01 AM, Banshee421 said: Do horns get low Link to comment Share on other sites More sharing options...
vrollin Posted September 1, 2012 Author Report Share Posted September 1, 2012 Yeah looks quite small, opening is 1.25 inch by 4inch, but seems to be doing the job. Would love to trial a much bigger box and see how it effects it all, may build one some day for shits and giggles, but unfortunately if I want the style I have gone for in this car then Im stuck with smaller boxes... Unless I relocate the battery.... Dun dun dunnnnnn..... Link to comment Share on other sites More sharing options...
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