SuperRed Posted December 23, 2015 Report Posted December 23, 2015 Ran into a bit of a conundrum when designing the 1/4 Wave for my x12. My issue comes into play with the driver area. The surround on these are massive and the driver surface itself is concave. Pretty deep as well...so the question comes in as should I go directly across center to center of surround, or measure from center of surround, down the face of the driver, and back up the other side to the center of the surround? There is roughly a 4.5-5" length difference. Meaning the area of my vent would be greatly effected. Any tline pros or great minds out there to help would be greatly appreciated
Triticum Agricolam Posted December 23, 2015 Report Posted December 23, 2015 What are your goals for the system? Setting the line area = cone area is not always the best thing to do anyway. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds:
3vil Posted December 23, 2015 Report Posted December 23, 2015 Use the Sd parameter from the Thiele/Small data. If you have the time and money I'd try building a straight t-line and see how it sounds. Then build a, not sure the correct term maybe "reverse horn" t-line where the line area near the sub is 1.5Sd and tapers down to maybe .75Sd by the time it reaches the terminus. There is a lot of testing and rework that goes into a t-line, I've been working on my first one for about 3 months in my spare time. Constantly tweaking the design to see if any improvement can be found. I'll also admit that I'm not anywhere near the acoustical engineer of many of the builders here, there is a lot science and testing involved in "perfecting" a quarter wave enclosure.
Yellow1000 Posted December 23, 2015 Report Posted December 23, 2015 Subscribing here , I'm curious about this as well.
SuperRed Posted December 23, 2015 Author Report Posted December 23, 2015 Goals are honestly a mix between highest output/daily use and wide band. That's why I decided on the tline in the first place. If going off of surface area=line area isn't always a good idea, than what is suggested most? And 3vil, I can't seem to find definitive parameters for this woofer. I've seem numerous differences in them from different sources all claiming to be sundown reps... It's annoying.
Yellow1000 Posted December 23, 2015 Report Posted December 23, 2015 3vil, where do you come up with the formula for designing a tapered line? What's the logic behind it? Not being a smart ass here , just wanna pick your brain some.
bbeljefe Posted December 23, 2015 Report Posted December 23, 2015 Calculate Sd from center of surround to center of surround. The measurement doesn't have to be exact.As for the differences in line area and what their benefits/drawbacks are, I'll try to hit a few brief points. Lemme know if you want elaboration on any one point and if I know, I'll do so. If not, I'll make some sciency sounding shit up and add some long words to it so you think you're getting your money's worth. • Larger than Sd lines produce smoother response and wider bandwidth but raise tuning and lower power handling • Smaller than Sd lines increase SPL & power handling but lower tuning and narrow bandwidth • Tapered (gets smaller toward the terminus) lines increase output but lower tuning. However, they also displace volume and thus, are easier to fit in small places Regarding the formula for tapered lines, there is a lot of information on quarter-wave.com but it's kinda geeky. What's easiest for me to calculate (because I'm retarded with respect t maths) is a 4:1 ratio line. Basically, you'll start at full driver Sd and reduce the line area to 25% of Sd at the terminus. Oh and, I'm not well versed enough yet to explain why that ratio is good or what may be better or worse for any particular purpose. But, I've build a lot of t-lines and that formula for tapered lines has produced munch successful for me. Facebook: facebook.com/audioanarchyllc Instagram: audioanarchyllc Youtube: youtube.com/bbeljefe
Triticum Agricolam Posted December 23, 2015 Report Posted December 23, 2015 T-lines can have a very wide frequency range and sound very clean, but its unlikely to get that kind of performance purely by chance or accident. Really T-lines and ported boxes are very similar, they both do the same thing, they just do it in a different way. Just like how you can change how a ported box sounds by adjusting the net volume and tuning frequency, you can change how a t-line sounds by adjusting the line area/shape and tuning. There is a problem with the common t-line design methodology of setting the line area equal to cone area and tuning to Fs. You are basing the design off of only two subwoofer attributes. There are lots of 12" (or 10", or 15" or 18") subs with a Fs in the low to mid 30s, but they are certainly not all the same and will have very different specs despite the fact they all have the same cone area and Fs. These different subs will all perform VERY differently if put in the same T-line design. This is just like how not all 12" subs perform best in a 2.5 cube ported box. This is why if you care about how the enclosure is going to sound you have to put more effort into the design and consider ALL the specifications of the sub/s you are going to be using. Setting the line area equal to cone area is usually going result in a t-line that has a huge peak in output around the tuning frequency (small bandwidth) and has pretty low mechanical power handling. This is especially true with higher RMS rated subs since they usually have low Vas (tighter suspensions). Tapered lines perform like they are longer than they actually are, the main benefit of this is space savings. They are much more difficult to lay out though and there is a little bit of a loss of efficiency. There is definitely more than one way to design T-lines. The way I do it it is using software, such as Hornresp, which can model T-line output. Hornresp is free, but it is not intuitive and it takes some effort to learn to use. It is very powerful though. I wouldn't even consider designing a t-line without the use of modeling software, but that's just my opinion on the matter. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds:
3vil Posted December 23, 2015 Report Posted December 23, 2015 And 3vil, I can't seem to find definitive parameters for this woofer. I've seem numerous differences in them from different sources all claiming to be sundown reps... It's annoying. I checked the Sundown site bit didn't find any quick info, I'd try emailing/calling them directly through the website to get all the T/S data. 3vil, where do you come up with the formula for designing a tapered line? What's the logic behind it? Not being a smart ass here , just wanna pick your brain some. Honestly, I started here http://www.stevemeadedesigns.com/board/topic/1828-quarter-wave-t-line-tutorial-updated/page-1 and read the WHOLE thread. Then I went to http://www.quarter-wave.com and read everything about 3 times. I'll admit a TON of the info there is way over my head, but I tried to glean as much information as I could before I sat down and began the design phase of my first enclosure.
SuperRed Posted December 23, 2015 Author Report Posted December 23, 2015 So, what I'm getting fully out of this, is that I should find hornresp and attempt a design from that? I've read hours and hours of tline write ups, but as I'm sure some of you guys are, you can only ingest so much information before it becomes meaningless, or you're like me and can get a decent grasp on the concept yet never fully understand it until you're put in a hands on situation. Guys I really appreciate the help thus far and I will surely post more ideas or questions on this thread regarding the build. Thanks again
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