30532
From: kicker 18's, [abq-215.13-185-64.nts-online.net]
Subject: Passive Radiator system for 18" subs
| I found stryke audios last night and am interested in possibly doing a settup with there 18" passive radiators for my kicker comp vr dual voice coil subs I use in my home. These are the newer style and specs are qts.-.365, vas-14.86, fs-16.4 hz, and Xmax-14mm. Im sure it would require at least 2 of the PR's per enclosure, but it is either this or a transmission line style box, and would much prefer to get the added spl near the fs out of a much smaller pair of boxes(the trans line settup would be enormous for just one of my subs, 54" wide x 72" tall and 40" deep), and am tired of sealed box sound. I have an earlier model 18" comp vr with the single voice coil in a 9.5 foot box for a q of .5, and the sound is good, just low power handling. With newly built 5.5 foot sealed boxes for my 2 new 18's, for a q of .7, I am seriously dissapointing in the performance of the 15 to 25 hz range even room loaded. Please help, I know nothing about PR settups!!! |
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30535
From: norman bates, [oproxy3.rockwellcollins.com]
Subject: With that driver you can port low, here's a ported design...
|
Standard Ported Vb 12.36 ft3 F3 17.48 hz Tuning freq 17.06 hz 8" Port length 31.81 " long Ported equations Vb = qts^2.87 x 15 x Vas F3 = qts^ -1.4 x .26 x fs Fb (tuning) = qts^ -.9 x 0.42 x fs A = 1.463 x 10^7 x R^2 B = Fb^2 x Vb (volume in cube inches) Lv = (A / B) - 1.463 x R R = radius of port I believe passive radiators need to have more area than the driver (2 15s with 2 18s for radiators). Tuning that low would be like the earthquake sub ($3,000). Sealed qtc.707 yields a f3=fsb=31.77hz. Corner loaded should produce flat to near 20s. There ain't crap down there besides organ, cannons, low synth, or bass cds used to show off your system or blow some steam by making your own earthquake. But hey, if you want to, go for it. This ported alignment will go damn deep, but the box is big ( my 2 boxes of double 18s need 9ft3 each and room for a plenum and a 12" port 14" long, it's 6th order tuned to 26hz for -3db@below that in room and can hit 128db from 28hz up.) and will bottom out Like your qtc .5 at 25hz with the same amount of power as your sealed did, but you can put in more power from 17hz to 25hz, you are not gaining a hole hell of a lot by tuning, as yes you can take more than 100 watts at 17hz if you have enough port area to account for the massive amount of air rushing through the port but it may only take 40 watts at 25hz to crash into the bottom of the magnet. My recomendation would be multiple drivers in that sealed qtc.707 and slot load them like the bassault by bag end (that costs $8,400, yikes !!!). As you double the drivers you gain 6db (but you need more power). Use 4 of them. If that doesn't work use eight. 6db is not double loud in treble region but it is in the bass region (till a certain point on the fletcher munson curve). I would want a much larger port, but a 10" port in a 12.36ft3 box tuned to 17hz needs to be 51.5" long !! |
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30538
From: kicker 18's, [abq-215.13-185-64.nts-online.net]
Subject: Re: With that driver you can port low, here's a ported design...
| Thanks alot! That helps me out knowing I don't have to purchase multiple PR's to get decent output down low. I've already spent enough money lately on subs and a 1400 watt amp, my wife wants to kill me now that im not happy with the sound of the new subs and boxes. Couple questions for ya, is that 12.36 feet spec needing to be enlarged for the back volume of the motor structure and bracing e.t.c. of the box? If so by how much do you suppose? What material do you use for ports? And 128 db!!! You have what im reaching for here. What brand subs do you use? Pro sound? Thanks alot! |
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30540
From: norman bates, [oproxy2.rockwellcollins.com]
Subject: I use Eminance (bought on closeout parts-express $100 each)
|
18s have qts near .34, Fs 28hz and vas can't remember. 8 ohm drivers, 96db spl 1w/1m. Paper with accordian surround. The car audio guy that built the boxes scoffed at them. Them we hooked em up after boxes were built. He said that's alot fast than I'd ever heard out of 18s. The bracing and such you'll have to figure out brace space, I figure .125ft3 for an 18" motot stuff of space. ports can be pvc or cardboard tube used for concrete pillars availiable at home depot. 128db is a lot easier to reach at 28hz than it is at 15hz. You can put in over 100 watts at tuning, but even on my subs, 1 box can take 800 watts rms at tuning frequency (won't go louder than if had 200 watts though due to voice coil heating/losses and compression) but it would only take 100 watts at 40hz on 1 driver to bottom 1 out. the excursion on a ported is similar to a sealed until about 1/3 octave above tuning, then the excursion decreases till tuning, then skyrockets below it. 28hz tuning is fine for me. The ported I recommend will go a lot lower louder below 28hz than mine, but you probably would be lucky to get above 110db from 30 to 25 hz without bottoming them out. |
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30542
From: kicker 18's, [abq-215.13-185-64.nts-online.net]
Subject: Re: I use Eminance (bought on closeout parts-express $100 each)
| Not sure I understand the ported design if it will bottom out the subs at 25 to 30 hz at 110 db or less. Would the response at 18 to 20 hz be capable of the same 110 db? If so, I could probably deal with the lower than hoped for spl levels, if not then what is a good compromise for high spl levels down to at least 25 hz? I appreciate all your help on this, like the other guy posted, being car audio drivers I knew they placed more emphasis on durability and power handling than trying to enhance the low end any. Im certain of 110 db levels at 30 hz with the two .7 qtc boxes I have now, probably well over that. I almost bought some of those drivers myself when parts express was clearancing them out. I should of bought some obviously!What kind of power handling would I have with the 12.5 foot ported boxes? I went and checked out the bassault from bag end, all I can say is wow!!! 104 db sensitivity with one watt, yet will hold 3200 rms! I can just imagine one in the corner of my living room. Go check out www.servodrive.com, they got some cutting edge stuff that is out of this world as far as bass production goes. I appreciate your help on this subject. One more quick question, what kind and how much damping material per foot do you use in your ported boxes? |
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30550
From: norman bates, [oproxy2.rockwellcollins.com]
Subject: hey
|
If you put a driver in a sealed and ported box of the same size, the sealed excursion increases until fsb then doesn't travel much further (same power at all frequencies. The ported excursion follows the sealed almost exactly until about 2/5 an octave above the tuning frequency. Then the excursion decreases to almost nothing (if you have a large enough circle port based on the amount of air flowing through the vent ). I like to see for a 28hz tuning a 6" port for 1 12", a 8" port for 2 twelves or 1 eighteen, and 1 twelve inch port for 2 eighteens. If tune lower you'd need a bigger port. Take your .5 qtc, port it to 18hz. If the sealed bottoms out at 60 watts at 35hz so will the ported. The drivers will mover further and further till fsb on the sealed box. As frequencies are halved, excursion is quadrupled. At 25 hz the sealed may need 38 watts while the ported may need 90 watts. Speaker programs can be used to figure this stuff out. Anyway my subs are parallel 8 ohm 96db 1w/1m, making a 4 ohm load with 102db 1w/1m. I don't believe in stuffing. I'll email again near 7:00 iowa time. |
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30552
From: djk, [tc031.cedar-rapids.net]
Subject: Wood
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I think I am getting a wood. Hey, I built a box just like this one for a Ford Escort. Had four 12s though. 21" ? |
30555
From: norman bates, [oproxy2.rockwellcollins.com]
Subject: How's it going djk !!!!!!
|
Didn't we talk about building something like the bassault ? Slot 18s push/pull ???? Clarion makes a 32" (I believe mostly europe though). See if anyone wants my jbl m151-8s (70 each seems fair). Good to see you posting............ Don't put forth too much effort online as any jackass will argue that the sky is falling. Maybe you'll trade jbls for mcintosh amplifier. |
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30553
From: kicker 18's, [abq-225.13-185-64.nts-online.net]
Subject: Re: Wood
| Norman Bates said that once a sealed box system reaches fsb( frequency of box resonance) that the sub doesn't really do any more excursion that so to speak. That makes sense now on how bag end and carver True Subwoofers make incredible bass down low without killer excursion levels out of 2000 + watts. They make sealed enclosures out of high qtc settups (like .9 and higher) and only use the enclosures below the fsb, with a butt load of eq and watts for some serious bass. |
30652
From: mikeported, [httpproxy.clear.net.nz]
Subject: Re: Wood
|
www.linearteam.org winisd shows excursion in different configurations |
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30556
From: norman bates, [oproxy2.rockwellcollins.com]
Subject: Take any advice from djk when you find some....
|
He's taught me more than years of stereophile and audio issues. If I could bottle him up and sell his knowledge, I'd be a multimillionaire. |
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30551
From: kicker 18's, [nts-99.13-185-64.nts-online.net]
Subject: Re: hey
|
You seem much more educated than myself on this topic, so I apologize for all the annoying questions, but I have to ask to learn. Does that mean that a ported enclosure is clearly superior for spl levels if it will hold 90 watts (compared to the sealed less than 40 watts) at 25 hz? What would be a guestimated 25 hz spl level out of two seperate 12.5 cubic foot enclosures tuned to 17 or 18 hz? Would the spl levels above 25 hz be signifigantly or just moderately enhanced by a tuning frequency of 25 to 28 hz? You may be talking me into a higher tuning frequency for more spl levels in the more used range here. I have a 30 hz subsonic filter on my amp I have turned off now, but could use it with higher frequency tuning. I do really enjoy the serious house shaking factor of the sub 30 hz region, but i also like the serious spl levels. Thanks again |
30557
From: kicker 18's, [nts-87.13-185-64.nts-online.net]
Subject: still fiending info on my previous post! Please!!!
| I will wait on yalls replies, but have one more quick question. I went over to eatel.net, and used the program on there to predict a ported box for my subs, and rather than 12.36 cubic feet like norman bates recommended, it said 10.68 cubic feet with a 18.1 hz tuning and a F3 of 18.9 hz with the same exact 8" diameter port 31.81" long recommended to me for the 12.36 foot boxes. Whats up with this? Who has the correct software? Getting confused again!!! Thanks for all help |
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30564
From: norman bates, [cache-rl03.proxy.aol.com]
Subject: there is no 1 exact enclosure......
|
Like sealed you can run small and high roll offs, you can run big. You can tune where you want. If you do a search on ported formulas you can find a number of different alignments. How much power could you get without bottoming out ??? at what frequencies ??? |
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30534
From: mrvinecelli, [12.22.48.2]
Subject: Re: Passive Radiator system for 18" subs
| im just guessing at this but im gonna say that since the comp vr's are meant to be used in a car environment that they were designed with a lower end that would need that cabin gain in order to get GOOD spl results so in a home environment where there isnt as much of a gain for the lower frequencies your not going to get the sort of results that you would expect in a car environment but being 18 inch woofers this shouldnt be much of a problem but still i think could be part of the problem and being in a sealed box could also be part of the problem |
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