Scp53 Posted January 23, 2006 Share Posted January 23, 2006 CAS, what do you mean by qes and pe? qes is the electrical q of the driver and the pe is rms power handling. what does this have to do with finding air velocity of the vent/port? you should be able to "plug in" X watts and go to the air velocity graph and see where it peaks,etc. What version of winISD are you using? the "standard" or "pro"? I think only the "pro" version will show the air velocity and all the other advanced stuff.The basic version of winisd wont(at least I dont think so)... scp53 Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 23, 2006 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. You need to input the power level that you want to read the port velocity at. It'll be under the signal tab in the window for the driver you're modelling. So looking at the cone excursion graph, you want to increase the power until the excursion is at its max. This will maximize the port velocity through the port where you will then try to adjust the mouth size and number of ports to get it below 20ms, while also making sure the port will fit in the cabinet. Also, make sure you are looking at the "rear port velocity" and not the front port. For basic reflex cabinets they put the port measurements in the "rear port" section. Btw, the reason you see the "Qes/Pe" error is because those are two of the bigger variables used in the port velocity calculation... Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 23, 2006 Share Posted January 23, 2006 Oh on top of DrWho, I would not try to build the port size on max volume..... When was the last time you played you music at max volume. Most of the times when I configured ports for a DIY sub, the port size or the length was way too much if you try to match the port to max wattage. I would say 2/3 of the max wattage is what you should match the port size too. Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 23, 2006 Share Posted January 23, 2006 Oh on top of DrWho, I would not try to build the port size on max volume..... When was the last time you played you music at max volume. Most of the times when I configured ports for a DIY sub, the port size or the length was way too much if you try to match the port to max wattage. I would say 2/3 of the max wattage is what you should match the port size too. A better way to word that would be to calculate your average listening level and then allow for 6-10dB of headroom (so as to best avoid port nonlinearities). It is also better to use a single larger port than multiple smaller ones. And you should pay attention in your designs to the fact that an overloaded port will actually have a lower tuning point...so in combination to your amplifier frequency response and whatever EQ/filters you're using - you will want to make sure that you don't run the risk of over-excursion. So try to center on a tuning point where you can change it 10% in either direction (+-3Hz) and not have any big changes on the response/excursion. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 23, 2006 Share Posted January 23, 2006 is the overloaded port having a lower tuning point due to the fact that the port effect extends a few more inches? I wonder if winisd accounts for that? I remember reading that once the air is out of the port that the sir still holds its shape for a few more inches and actually extends the tuning lower. Correct me if I am wrong DrWho[:$] BTW to extend to my post even further. Even the mighty SVS are not ported for max volume. They do exhibit port noise at max volume too... There are reviews that the cylinder ports had a rattle and whistle when a screw that was not tightened all the way that held the port grill. Also the B4 was under ported and claimed that port noise wasa exhibited at redicously high spl. Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 23, 2006 Share Posted January 23, 2006 I think it has more to do with pressure build up inside the port - essentially making the apparent mass of air heavier (due to a higher density). And just like a PR, raising the mass lowers the tuning. Btw, just because manufacturers allow for port noise doesn't mean DIY needs to. The whole point of DIY (especially with subs) is to exceed the performance of an off-the-shelf product while also saving money. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 23, 2006 Share Posted January 23, 2006 an audio question that DrWho doesn't exactly know !!! [] Btw, just because manufacturers allow for port noise doesn't mean DIY needs to. The whole point of DIY (especially with subs) is to exceed the performance of an off-the-shelf product while also saving money. no one ever told me that I am saving money !!! http://forums.klipsch.com/forums/585881/ShowPost.aspx oops! I calculate I would have saved more money by buying two kw-120! but the knowledge I gained from winisd, this forum, the members, lots of reading online, articles, physical woodworking experience, etc etc is priceless. Now I crave a CAM Router [6] and a workshop. Quote Link to comment Share on other sites More sharing options...
CAS Posted January 25, 2006 Author Share Posted January 25, 2006 an audio question that DrWho doesn't exactly know !!! [] Btw, just because manufacturers allow for port noise doesn't mean DIY needs to. The whole point of DIY (especially with subs) is to exceed the performance of an off-the-shelf product while also saving money. no one ever told me that I am saving money !!! http://forums.klipsch.com/forums/585881/ShowPost.aspx oops! I calculate I would have saved more money by buying two kw-120! but the knowledge I gained from winisd, this forum, the members, lots of reading online, articles, physical woodworking experience, etc etc is priceless. Now I crave a CAM Router [6] and a workshop. Well, if such tools and knowhow are present (or if it can all be borrowed) then DIY should save you quite a bit of money. All you need is a few weeks worth of research and a drill, a planer, a router, a jugsaw, clamps, adhesive, wood screws, sheet metal screws, sander, fiberfill, finish material, gasket material, the kitchen sink, your next born..... Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 25, 2006 Share Posted January 25, 2006 NOT MY NEXT BORN!!! Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 25, 2006 Share Posted January 25, 2006 an audio question that DrWho doesn't exactly know !!! [] Btw, just because manufacturers allow for port noise doesn't mean DIY needs to. The whole point of DIY (especially with subs) is to exceed the performance of an off-the-shelf product while also saving money. no one ever told me that I am saving money !!! http://forums.klipsch.com/forums/585881/ShowPost.aspx oops! I calculate I would have saved more money by buying two kw-120! but the knowledge I gained from winisd, this forum, the members, lots of reading online, articles, physical woodworking experience, etc etc is priceless. Now I crave a CAM Router [6] and a workshop. Well, if such tools and knowhow are present (or if it can all be borrowed) then DIY should save you quite a bit of money. All you need is a few weeks worth of research and a drill, a planer, a router, a jugsaw, clamps, adhesive, wood screws, sheet metal screws, sander, fiberfill, finish material, gasket material, the kitchen sink, your next born..... Or you just hire out someone to build the cabinet for you....or do like I did and have a friend build it for free [H] Quote Link to comment Share on other sites More sharing options...
thxsubwoofers Posted February 2, 2006 Share Posted February 2, 2006 kw 120 woofer notice the triple stack magnets hmm lookie at the rsw15 motor and the kw120 motor! A little off topic, but does anyone have a picture of the RW-12 motor? Or any picture of the RW-12 with out the subwoofer box. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted February 2, 2006 Share Posted February 2, 2006 you mean the rt-12d? the new corner subwoofer? Quote Link to comment Share on other sites More sharing options...
fabulousfrankie Posted February 2, 2006 Share Posted February 2, 2006 "Slot loaded tends to reduce port noise a little more than a round one." I've always been under the impression round ports reduce port noise more than a slot loaded port. I have no way to really verify either way though. Just curious where you came up with this? Quote Link to comment Share on other sites More sharing options...
DrWho Posted February 2, 2006 Share Posted February 2, 2006 Really the only thing that is going to reduce port noise are flared ends on the port (they act as an impedance coupler to force the sound to spread out and slow its velocity down). I think the only thing in a slotted port's favor is that they are easier to implement with a large cross-sectional area. However, you do want to maximize the surface area to circumference ratio (the less boundaries on the port inlet/exit, the less noise) - and circles are the optimum shape for such a thing. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted February 2, 2006 Share Posted February 2, 2006 doesn't flaring make it psuedo hornloading? Quote Link to comment Share on other sites More sharing options...
thxsubwoofers Posted February 3, 2006 Share Posted February 3, 2006 you mean the rt-12d? the new corner subwoofer? No, no the old RW-12 Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted February 3, 2006 Share Posted February 3, 2006 hahahahahhaha I dunno then. Quote Link to comment Share on other sites More sharing options...
thxsubwoofers Posted February 3, 2006 Share Posted February 3, 2006 hahahahahhaha I dunno then. I guess nobody has unscrewed the woofer? [] Quote Link to comment Share on other sites More sharing options...
TheEAR Posted February 3, 2006 Share Posted February 3, 2006 doesn't flaring make it psuedo hornloading? The size of the flare and the freq. of tuning...not much gain to be had.Flaring will above all reduce port noise. Quote Link to comment Share on other sites More sharing options...
CAS Posted February 9, 2006 Author Share Posted February 9, 2006 Suppose I'll post some pics tonight of my finished product. I forgot to take construction before and after pics since I gave it away so swiftly to my brother in his haste. I'll post a couple perhaps tonight. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.