CAS Posted January 20, 2006 Share Posted January 20, 2006 It appears from the website pics that the slots on the KW-120's are approximately 17" by 2" tall. With that area it would seem the port probably has to turn a corner or two internally. Do you think 2" is the minimum height you could use before port noise becomes apparent? What about 1-1/2"? Or is it a function? Quote Link to comment Share on other sites More sharing options...
Scp53 Posted January 20, 2006 Share Posted January 20, 2006 That all depends on the tuning freq., cabinet size, woofer,etc. The port needs to be designed to stay small enough to take up the least space but yet not go over an air velocity of 10% the speed of sound(which equals chuffing) at max spl through all the subs pass band. At least I think its 10%....Not sure if that helps ya... scp53 Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 20, 2006 Share Posted January 20, 2006 It appears from the website pics that the slots on the KW-120's are approximately 17" by 2" tall. With that area it would seem the port probably has to turn a corner or two internally. Do you think 2" is the minimum height you could use before port noise becomes apparent? What about 1-1/2"? Or is it a function? Yup it has to be bent Slot loaded tends to reduce port noise a little more than a round one. Also it is important to have a flared port on either a round or slot loaded. This reduces the chuffing at higher volumes plus you need less port length when it is flared. From WinISD help: Very important here is to make your ports large enough, so that peak air velocity won't exceed 5% of sound velocity in air. That is, about 17 m/s assuming normal environmental conditions. But most professional subwoofers use the 20 m/s as the chuffling increase spl a bit more and it is less noticeable on the stage than in a quiet home. But remember most subwoofers on the market with ports will experience chuffling at max volume. Even the mightly SVS B4 chuffles but reviewers said it's at such rediculous levels that no sane person would ever hear it. Safe to say I would go as far as at max volume 25m/s is fine.... Atleast when you hit max amp power then the chuffling noise will tell you hey its at max volume you idiot! I am going to break if you push me harder. Quote Link to comment Share on other sites More sharing options...
Scp53 Posted January 20, 2006 Share Posted January 20, 2006 My bad.. I thought it was 10%... not 5%... oh well Thanks for the pic btw. Ive never seen the inside of the thx ultra sub. Do you really think the flare helps that much on this thx sub in terms of affecting length? The flare seems very slight from the pic you posted... imo Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 20, 2006 Share Posted January 20, 2006 anything is better than nothing. espcially sharp edges which increase turbulence. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 20, 2006 Share Posted January 20, 2006 kw 120 woofer notice the triple stack magnets hmm lookie at the rsw15 motor and the kw120 motor! Quote Link to comment Share on other sites More sharing options...
Scp53 Posted January 20, 2006 Share Posted January 20, 2006 No No Jay, I wasnt doubting that the little round overs dont help with turbulance, Im sure they do! I was just saying I doubt they affect the over all length of the port. As for the woofer, as many know, looks arnt everything. There are some VERY modest woofers out there capable of much more than "big potent" looking ones. Im talking about both sq and spl. scp53 Quote Link to comment Share on other sites More sharing options...
CAS Posted January 21, 2006 Author Share Posted January 21, 2006 I notice the slot curves around instead of right-angles at the corner. Would that be out of the question? Quote Link to comment Share on other sites More sharing options...
CAS Posted January 21, 2006 Author Share Posted January 21, 2006 I think I answered my own question. JL does it with some W7 enclosures so I feel safer doing it as well. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 21, 2006 Share Posted January 21, 2006 oh I doubt the flare does really shorten it. I remember having a 6 inch port and a flared 6 inch port which is like 9.5 inches wide on the ends [] reduce the port by a measly 2-3 inches. So I doubt it then. but for turbulence, hell remmeber the first plane to hit the speed of sound had to be redesigned over and over and the thing that did it was to curve the back end of the airplane more like an hourglass. Even the pilot went to the engineers, "Is that really going to help?" Also JL W7 has the 90 degree ports because they are forced to. The W7 moves soo much air that no round port is capable without the length being astronomical. The slotted port is bent also to help make it fit in your car. The thing is though the port tuning and specs do change when they have a bend or a curve. Hence the kw-120 tries to reduce the curve to a min. They could have done a 90 degree and gain alot more internal space, see pics, and lose the handle in the back of the sub. But there obviously must be a reason. also think water management when thinking about the 90 degree bend for a port. A 90 degree bend in plumbing does work but it does lose total flow of water. But its a compromise then making the walls and floor bigger to accomodate gently flowing pipes. Heck the rw series subwoofers used the angled port just so they would not bend the port. So they had the one end of the port on the corner and the port ended up in the front. If JL could have they would not have put a 90 degree bend as it sorta changes the tuning frequency of the port. Think string instrument and when you place your finger on the fingerboard to make a different sound. Yes same length overall but you just shortened it a bit by whereever you placed the 90 degree bend. I am sure DrWho can elaborate more on this. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 21, 2006 Share Posted January 21, 2006 No No Jay, I wasnt doubting that the little round overs dont help with turbulance, Im sure they do! I was just saying I doubt they affect the over all length of the port. As for the woofer, as many know, looks arnt everything. There are some VERY modest woofers out there capable of much more than "big potent" looking ones. Im talking about both sq and spl. scp53 true just with life, some dogs are all bark and no bite. I know some offenders just think having a triple stacked magnet is stronger, Some people are all about how much xmax instead of Bl, efficency, FS, etc. Some speakers are more rubber surrounds than actual cone (Think sunfire junior). Some have a better basket that is more like an automobile rim. Heck some are square, some are painted red, or silver, etc. Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 21, 2006 Share Posted January 21, 2006 CAS, what's the specific project you're working on? Curving the port will change the tuning frequency - I don't remember which way, but generally a good subwoofer design can be +- a few Hz without causing too many changes. And don't forget that ports can go at any angle into the cabinet (diagnals maximize their length). Also, I believe the KW's are pushing 40m/s at peak output. I know of a few other commercial "quality" subs with the same issue too. If you're using winISD it might be a more practical approach to figure out how loud your usual peaks are and then adjust the port size to be 20m/s at that SPL. And if you make it a rear-firing port, then you will even further minmize the audibility. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 21, 2006 Share Posted January 21, 2006 40m/s ummm wow no wonder there has been talk saying that port noise is very noticable on the kw120. Quote Link to comment Share on other sites More sharing options...
Scp53 Posted January 21, 2006 Share Posted January 21, 2006 I wondering why Klipsch did this? I guess its obviously to save space.... Does anyone know if that chuffing comes into play on the subs published output specs? I know they only publish what is under 10% thd but would they still leave chuffing distortion in it? To me, chuffing at 40m/s would be very bad. Just as bad as thd or any other distortion. hmmm.... scp53 Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 21, 2006 Share Posted January 21, 2006 It was a design choice to make the subwoofer completely front-firing so it could be flush mounted. And yes, the chuffing comes into play during loud scenes - but it's usually drowned out by the rest of the sounds (not to mention it's not very audible when explosions happen either). I don't think it would be listed as part of the THD spec because it really isn't harmonic distortion... Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 21, 2006 Share Posted January 21, 2006 but distortion none the less, I guess my distortion definition is any sound that is undesirable or not on the original recording. Quote Link to comment Share on other sites More sharing options...
Scp53 Posted January 21, 2006 Share Posted January 21, 2006 exactly! well said... Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 21, 2006 Share Posted January 21, 2006 but distortion none the less, I guess my distortion definition is any sound that is undesirable or not on the original recording. Well there are different types of distortion and it's important to specify the differences between the different types. The new RT-12d's are supposed to be the lower distortion versions [] (just less position friendly) Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 21, 2006 Share Posted January 21, 2006 true and not at all stack 4-5 of them in a corner for some power! Quote Link to comment Share on other sites More sharing options...
CAS Posted January 23, 2006 Author Share Posted January 23, 2006 CAS, what's the specific project you're working on? Curving the port will change the tuning frequency - I don't remember which way, but generally a good subwoofer design can be +- a few Hz without causing too many changes. And don't forget that ports can go at any angle into the cabinet (diagnals maximize their length). Also, I believe the KW's are pushing 40m/s at peak output. I know of a few other commercial "quality" subs with the same issue too. If you're using winISD it might be a more practical approach to figure out how loud your usual peaks are and then adjust the port size to be 20m/s at that SPL. And if you make it a rear-firing port, then you will even further minmize the audibility. The problem with winisd in this project is no matter what configuration I try I can't get the velocity to read anything but Qes/Pe!. I'm doing a down-firing slot-vented rear-port enclosure with an old car audio Orion XTR and a spare plate amp. Quote Link to comment Share on other sites More sharing options...
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