michael hurd Posted November 3, 2003 Author Share Posted November 3, 2003 Good news that a 6" straight port will work. This simplifies things alot. I also have talked to a local shop here in scarborough, speakers direct. They produce studiolab loudspeakers in house. Although a tube is quite simple to make, they said that they can machine and assemble a box cabinet for me, provided I give them the dimensions and cutting lists. That gives me another option. I kind of like the tube concept still. Aargh! The choices! Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 3, 2003 Author Share Posted November 3, 2003 Hmm. Just finished reading all the threads that come up under "tempest" in the forum. Some good information in them. I have kind of given up on the pvc pipe for the enclosure, unless I can find a piece of scrap somewhere. Rona has both 18" and 24" diameter x 12 foot sonotube in stock.$ 59.83 for the 18" and $ 88.75 for the 24". I think that I could probably get away with a single tempest, in an 18" diameter sonotube, and having the port at the opposite end. If I get a 4'x8'x1" piece of mdf cut down to 20"x20" than I will have 8 pieces to work with. That's enough to make 2 enclosures with. What's your thoughts? Make two enclosures ( roughly the same work ) and try one out? If that's all I need, then maybe I could load the other one and sell it, for the right price of course. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 3, 2003 Author Share Posted November 3, 2003 Help! What's a good rule of thumb to keep the port velocity ( in m/s ) down to? The simulation I'm running is a 275l enclosure with 10% fill , tuned to 19.0 hz, and a port diameter of 15.2 cm. The drive level being a modest 175 watts, at 20 hz, the port velocity is 9.23m/second. Also, it appears that this is approaching 36- 38 mm peak to peak above 20 hz. As the enclosure size goes up, excursion goes up, and also the impedance starts to climb. I wonder if that would have any effect on the amplifier? Anyone? Quote Link to comment Share on other sites More sharing options...
fire pinch Posted November 4, 2003 Share Posted November 4, 2003 9,23m/sec for the air velocity? Excellent!!! You won't hear any port noise at all. as a rule of thumbs, considere 35m/sec as the maximum acceptable air velocity (10% of the air speed). But it is recommanded that you keep it down to half of this value so about 17m/sec. WinISD PRO by memory justly tell us to not surpass 17m/sec for the air velocity so a recommanded value. According to WinISD, the air velocity reach 35m/sec at 20 Hz for my subwoofer and this isnt a problem at all unless I run a 20 Hz test tone at full power But I dont hear ANY port noise in all kind of material, music or DVD's. A 175W amp you will use? Anyway, if you use all this power, you will most likely, theorically, bottom out your Tempest woofer. So I guess you will turn the volume down if you hear your woofer stressing. I dont think that this rising in impedance can be a problem for your amp. Is your amp rated for a 4 ohms load? I say this but... how will you wire your Tempest? You know, this is a dual voice coil woofer Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 4, 2003 Author Share Posted November 4, 2003 I bought a used yorkville ap500 power amp a while back for cheap. It works okay, but I don't know too much about it. I have tried the yorkville site, but that particular model isn't listed, so I can't print off an owners manual. I am pretty sure that I will power each coil with one amplifer channel. 8 ohms in stereo should be fine, as the amp won't even have to break a sweat. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 4, 2003 Author Share Posted November 4, 2003 I'm pretty sure that the amp will produce an honest 175w/ch in 8ohm stereo. The torroidal transformer is 5-6" around and really heavy, so I don't really think that the rising inductance should cause a problem. Quote Link to comment Share on other sites More sharing options...
fire pinch Posted November 4, 2003 Share Posted November 4, 2003 "so I don't really think that the rising inductance should cause a problem." This is what I think too... and I find very curious that you can reach a peak of 36-38mm of excursion with only 175W of power. Normally, the Tempest need more than that, between 200 and 300W of power depending of what size of enclosure and tuning point you choose. But even if this is a 300L enclosure tuned to around 19-20Hz, by memory, you should need more than 175W of power to reach the Xmax of the Tempest... gotta verify this. Quote Link to comment Share on other sites More sharing options...
fire pinch Posted November 4, 2003 Share Posted November 4, 2003 I just verified with WinISD Pro. My memory told me that I was right, if you really want your Tempest to reach its Xmax, considere more 300W of power. What you saw is that with 175W of power, the Tempest could reach 36-38mm of excursion around 15 Hz. I dont know if you have a subsonic filter setting in your amp, but if you dont have any, its true to feel safer with less power as your woofer will unload like sky rocket below the tuning point. I would recommand you to buy a subsonic filter, something like the SVS amp interface Box. You would set this at 18 Hz and you could use 300W of power for your Tempest and get the most of it IN CASE you want an amp suggestion, I suggest you the Rythmik Audio 350W plate amp. 350W? Even if you see that number, if you know very well your subwoofers, having more headroom is always a good thing! At 140$USD this is one of a very good amp for your money and it has a build-in subsonic filter. Quote Link to comment Share on other sites More sharing options...
formica Posted November 4, 2003 Share Posted November 4, 2003 ---------------- On 11/4/2003 1:26:56 PM fire pinch wrote: if you really want your Tempest to reach its Xmax, considere more 300W of power. ---------------- Pincette, your reading quickly today, huh? i think he said it's 175W/CHANNEL into 8ohms. That'll give him 175W to each voice coil or the equivallent of 350W mono into 4ohms. Sounds just about right... Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 4, 2003 Author Share Posted November 4, 2003 According to the simulation, transducer excursion above the tuning point of 19 hz goes up. At the tuning frequency, the transducer excursion is lower, as the port is doing most of the work. I don't want to hurt the driver by overdriving it, so keeping the power levels lower should reduce the chance of noise and/or damage. Quote Link to comment Share on other sites More sharing options...
fire pinch Posted November 4, 2003 Share Posted November 4, 2003 LOL! Yeah, true! Thanx for this Formica. His amp would be fine but I dont think that it has any subsonic filter. I was thinking at the same time of the guy who should call me in the next minutes for my QSC amp. I buy it today! Michael, Remember when I said in my post that you should buy a subsonic filter box? Then I forgot to tell you that IN that case, your amp would be very fine (because of powering each voice coil with 175W). But well... I thought this way: the subsonic filter box cost more (well I supposed the SVS one) than a Rythmic Audio amp WHICH HAS a subsonic filter build-in. So you could buy that amp and keeping your existing amp for another sub, a sealed one for example if your 175W amp doesnt have a subsonic filter. Quote Link to comment Share on other sites More sharing options...
fire pinch Posted November 4, 2003 Share Posted November 4, 2003 "I don't want to hurt the driver by overdriving it, so keeping the power levels lower should reduce the chance of noise and/or damage." True in general but not totaly true in all occasions IMHO. Just so you know, and maybe you already know, you might set the volume level of your sub at a certain point during a movie so you feel like it will never bottom out. But lets say that the volume setting was enough high to your ears so during an explosion, the signal requires that the amp sends a full load of extra power in your woofer. Whopps, the woofer bottomed out! If you say to me: when you know your movie, you know how to set the volume setting down so the woofer wont bottom out. -> good point Or... when you have enough of 95dB of power, you set the volume knob so you can hear an average of 95dB SO you dont bottom out the driver during a BING BANG movie part! I dont know by the way if in any movie, you can measure something like 95dB average to 120 dB!!!! Quote Link to comment Share on other sites More sharing options...
formica Posted November 4, 2003 Share Posted November 4, 2003 ---------------- On 11/4/2003 3:46:24 PM fire pinch wrote: I was thinking at the same time of the guy who should call me in the next minutes for my QSC amp. I buy it today! ---------------- I got my second coat of varnish on last night... another 5 to 10 to go... Rob Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 4, 2003 Author Share Posted November 4, 2003 Race? Did someone say race? Lol! You guys are sure hardcore at it eh? Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 4, 2003 Author Share Posted November 4, 2003 Time to get out the powersaw and the duct tape, eh fire pinch? Quote Link to comment Share on other sites More sharing options...
fire pinch Posted November 4, 2003 Share Posted November 4, 2003 LOOOL!!! haha YEAH THIS IS a race, a WAR ! Omg I must run right now with my scissors, cutting all the 1/16 thick MDF pannels that I will stick together with some tape!!! No but we understand each other eh Formica! We just say this for fun, we are just kidding! Notice that he can win anytime if we want to... he just have to buy an amp at a nearby store and voilà!!! Ive bought mine today, just after I wrote a post, I was waiting for a call. The amp should arrive in about 2 weeks. During that delay time, I will begin slowly to make the enclosure, so the sub will be finished around November 20th... I hope Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 4, 2003 Author Share Posted November 4, 2003 I wish I could start on one soon! Darn it, it'll be christmas before I'm home, and then I probably won't be able to start before the new year. Quote Link to comment Share on other sites More sharing options...
formica Posted November 4, 2003 Share Posted November 4, 2003 yup... its a race... and I've already won... lol... unless you figure that FirePincette is onto his SECOND sub while I haven't finished my first... but I'm actually looking forward to hearing his new Tumult "baby to be" Later... Rob Quote Link to comment Share on other sites More sharing options...
fire pinch Posted November 4, 2003 Share Posted November 4, 2003 FirePincette... ROFLMAO!!!!!!!!! You guys makes me laugh so much each time you deform my nickname!!! Yes, and me looking forward to hear his AV15 This is a very sharp beautifull sexy looking woofer that AV-15 Quote Link to comment Share on other sites More sharing options...
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