brennyE Posted November 23, 2006 Share Posted November 23, 2006 I just modeled the subwoofer I am putting together on Win ISD. Now I dont have much experience on these programs so I probably input something wrong. I am using a FUSION subwoofer (this sub is NOT for critical listening[]) http://www.fusioncaraudio.com/products.php?region=1&action=view&product_id=31 a 130L enclosure and I have a behringer EP1500 on the way that delivers 1200WRMS bridged into 2 ohms and 900WMRMS into 8ohms. I modeled this on Win ISD with 2 85mm ports tuned to 25hz. The program tells me the subwoofer will give me 125db between 30hz and 100hz and will be 3db down at 25hz...........Now I know this cant be possible with the small amount of money I spent and fairly small enclosure! I know there has to be a draw back somewhere (or two or three.......) and I would like to know what I have done wrong? could I get some one with WIN ISD or another subwoofer modeling program to double check this for me, so I can see what someone else gets? sorry if this is off topic being a DIY project and all but I just had to ask! Regards Brendan Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 23, 2006 Share Posted November 23, 2006 Is 14mm one-way capable of 125dB? even at 30Hz? Make sure you're entering the one-way peak into WinISD. Is this a home audio application or car audio? Another big thing to keep in mind is the power compression of the system. The system is going to be very non-linear at peak output. Resistance of the voice coil is going to increase as the temperature increases - which means less current is going to flow for a given amplifier voltage and then that 1400W is going to be increasingly wasted as heat instead of power in the motor (which will even further increase the resistance). Combined with the decreased magnetic force at peak output and extra stifness of the suspension... You're left with a lot of variables you just can't model in WinISD. I would scratch off 10dB from the predicted peak output to get an idea of the clean performance of the driver - and that's all assuming the driver manufacturer's specs are accurate... [] When I get home from break I'll be sure to check out the design. 4.5 cubic feet is a lot larger than you might think. Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 26, 2006 Author Share Posted November 26, 2006 Yup i entered the drivers Xmax as linear (not peak to peak) to get the results I got back. I also know how big the 130L enclosure will be because I have already built it, braced it and sealed it up, I also filled about 1/4 of the enclosure with accustic stuffing behind the driver. So the box is built (still needs painting, I cant think of a finish for it) and the driver mounted and ready to go. all I need to do is pay of the amplifier from my layby and it shall be ready to go. Another quick question, I read somewhere a while ago that accustic stuffing in a sealed subwoofer enclosure increases the volume of the box that the subwoofer driver "sees" so this means that the enclosure should be calculated as a bigger box? I think there is an equation for working out how much volume it would add. Regards Brendan Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 26, 2006 Share Posted November 26, 2006 hmmmm....so I've got it modelled here and I'm only seeing 117dB peak at ground plane. As far as absorbtion in the cabinet, I'd follow what the help file talks about. In fact, if you haven't read through it all I would highly recommend it. See attached picture. Quote Link to comment Share on other sites More sharing options...
colterphoto1 Posted November 26, 2006 Share Posted November 26, 2006 I think the gain in apparent volume due to completely stuffing an sealed cabinet is in regards to general full range speaker design, not subwoofers. Don't know why that would not be the case with all enclosures, perhaps it's just in the mids region? Michael Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 26, 2006 Author Share Posted November 26, 2006 ohhhhh ouch 117db...... is that after taking all the variables into consideration (compresion etc) or before? will this sub make a good party sub in your opinion or have I wasted time and money building it? Regards Brendan Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 26, 2006 Share Posted November 26, 2006 117/118dB is assuming you achieve peak excursion on the driver (which you'll probably be able to do). You can tack on another 6dB or so by putting it in the corner of your room. In my opinion, there is no such thing as wasting your time building things as long as you learn from the process. I have tons of crappy designs laying around [] (not to imply this is a crappy design) I think if you throw a peaking 2nd order high pass filter before the amps that you will really be able to rock it out at parties. Gotta protect that cone from over-excursion at frequencies below the tuning point - it makes a world of difference. Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 26, 2006 Author Share Posted November 26, 2006 Im fairly sure that the amplifier I am getting comes with 2 subsonic filters, one at 30hz and one at 50hz. I might use the 30hz filter which I suppose wouldnt be that detramental to the sound anyway as it begins to fall around 30hz anyways [] As for reaching excursion, the amplifier I am getting should be able to make this driver wheep in anguish because ill be stuffed if I believe the 1200W power handling for the FUSION. 600W is probably pushing it i would be thinking. I noticed that you are using WIN ISD PRO, so I just went out and dowloaded it. I will see if I get different results! Thanks for the quick reply! Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 26, 2006 Author Share Posted November 26, 2006 I have definatly learned from this! next subwoofer project I undertake I am going to make sure the subwoofer driver I am going to buy will do what I want it to do, before I buy it! I think given the results you just told me ( I just calculated it on WIN ISD PRO and got 119db peak at 45hz, alot more believable than my last results) this sub should fullfill the reason it was built. To go fairly loud and whilst doing that go deeper than your average pro audio subwoofer. Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 27, 2006 Author Share Posted November 27, 2006 wow that 2nd order high pass adds alot of gain! is it safe to place it at 45hz at around 6db, or would this be pushing the mechanical limits of the subwoofer to far? Remember though I will have a high pass on the sub at 30 hz, thus cutting out everything from underneath (this option is intergrated into the amplifier) would this cutting of the extreme low frequencies allow me to play with the plus 35hz stuff? This sub doesnt need to dig down mind blowingly deep, it just has to keep a tad of Low frequency impact. Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 27, 2006 Share Posted November 27, 2006 Well all you need to do is look at the cone excursion and apparent amplifier power graphs. You want to keep the cone excursion below its xmax - so to do this you'll have to manually calculate the effective surface area of the cone (which I found to be 1017 square centimeters). As you change the signal level and tuning point you will see the cone excursion move around. What you're trying to do with the peaking high pass is to make the peaks above and below the tuning point the same amplitude, while boosting the excursion at the minimum that occurs at the tuning frequency. You then only want to add so much boost as to keep within the thermal limits of the driver while maximizing cone excursion above and below the tuning point. To make sure you're within limits you'll need to look at the apparent amp power and keep it below the thermal rating of the driver. I would build everything to peak out at the 600W RMS rating and not the 1200W theoretical peak. You will also want to make sure you keep the port velocity at maxSPL below 20 m/s. The more boost you use, the worse this gets, so it's not totally free output unless you take care of the other variables. I went ahead and modelled your 30Hz high pass and it looks to be more than sufficient to control cone excursion below the tuning point - and will even work to swamp nonlinearities with power compressions. For a party sub I think you're going to be more than satisfied with your results. Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 30, 2006 Author Share Posted November 30, 2006 I have found myself bored with a digital camera, so I thought i would use my amazing ([]) camera skills to post a few happy snaps of the half finished sub and the listening room. Please no one have a fit because the subwoofer will be moved to a larger room when my family moves houses. here we have the unpainted, but ready to be run subwoofer, with a cd leaning against it for scale. I never thought I would buy a car audio subwoofer (or a PA amplifier for that matter [:|]) But the discount price I got (half price) and the massive magnet sold me. It is sealed at the moment, but if I am unhappy with the spl this will be changed! Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 30, 2006 Author Share Posted November 30, 2006 my RF-15 and sub having a nice one-on-one in the corner. hopefully soon the sub will have a bigger friend to chat with [H] Quote Link to comment Share on other sites More sharing options...
brennyE Posted November 30, 2006 Author Share Posted November 30, 2006 and last but not least the entire front wall of my *cough* huge *cough* bedroom. It took me at least a good solid 1 years savings to buy all the equipment ( I just let go of an RW-12 ) as it was purchased last year when I was 16 and getting paid less than I do now []. The RF-15's sound very, very good at low, to low-moderate levels (especially at night, sounds so good it makes your skin tingle!) and they make very good bedroom 2-channel speakers. At night (when I really listen properly) I move the speakers further out from the wall. Thanks Dr Who for all your help and advice! look forward to dabbling in the art of making another sub woofer in the near future (hopefully with more of your expertise!) Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 1, 2006 Share Posted December 1, 2006 So how does it sound? Quote Link to comment Share on other sites More sharing options...
brennyE Posted December 1, 2006 Author Share Posted December 1, 2006 The sub? Being as young as I am I have no amplifiers laying around the house to be able to test the subwoofer with, unlike allot on this forum that have amplifiers laying about everywhere [H] I am AUS$350 dollars away from paying off my amplifier, so once I have that the fun will begin! I have been able to test it out using a channel off the HK3480 (120W) using test tones (because i thought if i played normal music it would damage the sub? not to mention sound absolutely ridiculous!) to check for any leaks in the enclosure and such. I was happy to say it made things violently move around at about 30hz, and at 15hz my blinds and window were sounding very unhappy indeed. so.......all in all I was pretty happy! (because of such violent movement at 120W)well.....as happy as you can be with test tones any way. And also! I found what I was doing wrong on WIN ISD pro! when I went to calculate cone excursion to help me best tune the enclosure, it said i needed around 2metres travel (linear!) to reach 40hz at 100db...........in the end I worked out that I had the surface of the subwoofer all screwed up......like 8"squared.......[:$] but now that's all fixed I am getting the same results as you achieved.....all-in-all a happy ending. can't wait to get the big boy finished! Regards Brendan Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted December 1, 2006 Share Posted December 1, 2006 pie are squared What? you're an idiot look at it again pi r squared [] Quote Link to comment Share on other sites More sharing options...
brennyE Posted December 2, 2006 Author Share Posted December 2, 2006 oops double post [*-)] Quote Link to comment Share on other sites More sharing options...
brennyE Posted December 2, 2006 Author Share Posted December 2, 2006 yeh it went something like that.......but its all under control now....i think[] Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 2, 2006 Share Posted December 2, 2006 The sub? Being as young as I am I have no amplifiers laying around the house to be able to test the subwoofer with, unlike allot on this forum that have amplifiers laying about everywhere [H] lol! You pretty much called everyone on this forum old, classic [Y] Btw, you've just not been in this hobby for long enough...you're not too young. Heck, I've got plenty of amps to plug crap into and I haven't acquired any new ones since I was 18 (4 years ago). [] For the record...test tones are more dangerous than music, for both the amp and the speaker. [] Quote Link to comment Share on other sites More sharing options...
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