transmission line sub

So... You're in San Jose? I get up there on a regular basis, and my brother and I have been known to SHOW UP for Sharks games! (We sometimes actually SEE them, too!) Yeah, let us know! I love TL's... For SUBJECTIVE opinions, Ask DYohn, dwarren, tcss, jfinks, and hamzter (who I have not seen online in about a year), but the responses from them have all been very positive! They have all heard it. My input is this: Smooth, perfectly integrated, deep - like subterranean deep... Linearity is fantastic! One of the most impressive aspects of my system is the way the sub doesn't sound like it's behind me. It integrates so smoothly with the doors, that it sounds like the sub is in the kick panels. The install manager at my local Best Buy has been working on an SQ system for his car for a LONG time (he says) and is now asking me for tips! OBJECTIVELY, I'll have to run an RTA again, and get a few screenshots... Swamped this weekend, but I'll try to get something soon!It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Hah! What are the chances of that. It seems like every time I meet someone new they always live on the other side of the country. But the one guy's car I would like to listen to, he lives nearby!? Awesome. When my box is all done, do you want to meet up for lunch sometime? I gotta get back to the garage, the car is still in pieces but I need to be somewhere in two hours ... -JustinMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

Haem...how low does your TL audibly play down to?? Mine plays down to 25Hz...you can still feel it pretty well...thats unstuffed...then pretty much immediately after that it just falls on its face...lol

Dude! Count me in! (You have PM) Better hurry! It's never as easy putting things together as you think they will be! IIRC, my Fs is right about 24Hz. It goes respectably down to that, but that IS with one 10 incher, too... I've never been able to even REMOTELY call it an output monster, it ain't that, at all... Flat, articulate, and deep, though...It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Right on, and thanks for the PM too.Aaaaand, back on topic. The wood glue and caulk is all dry, the wiring for the amplifier is nearly done, but I need to sand down the box a little bit. The cuts on the MDF were a pinch less than square so the top of the box doesn't seal properly. Looks like tomorrow will be a fun day with the belt sander ...Stay tuned for more of my research and simulation screencaps, I'll post them later today.-JustinMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

Step the third: high efficiency woofer with low Fs to help achieve goal of 20hz and low power requirements Efficiency of a woofer is measured in decibels (db), and the industry standard is 1 watt / 1 meter. This means put one watt of power through the woofer and place a microphone one meter from the front. The signal being played is often not mentioned, but it could be a reference 1khz tone or most anything else imaginable so long as the amplifier is putting out 1watt of power. The decibel scale is a little like the Richter scale, in that the energy increases exponentially with respect to the reading. On the Richter Scale, a 4.0 earthquake releases 1,000 times the energy of a 2.0 earthquake. The decibel scale however, doubles every +-3db. So a reading of 6db is twice as great as 3db, just the same as 87db is twice as great as 84. If you think about competitions where cars are putting out 140db and higher, it's humbling to think about your "rig" that can sustain 120db ! On top of efficiency, I want to find a woofer with a low Fs, the resonant frequency of the speaker. The lower this number is, the lower I can tune the enclosure and the easier it will be to reach my goal of 20hz. This concept is true of all enclosures I know of, but don't let this number be the only thing you consider. Afterall, it's just a number. With that in mind, I began to look at 10" woofers within my price range, and about 300-400w power handling to match the amplifiers I have in mind. Using such sites as crutchfield, woofersetc, sonicelectronics, and tons of reading forums like this one for user reviews, I found a few to choose from:              RMS / Fs / db Alpine Type-R 500 / 31 / 83 Boston G210   300 / 37 / 83 Eclipse SW8000           625 / 18 / ?? Infinity Kappa 102.7w   350 / 20 / 89 Infinity Perfect 10dvc    400 / 25 / 90 JBL Power     400 / 34 / 92 JL 10W3v3     500 / 31 / 85 Kicker 08 S10 L52       450 / 33 / 86 Rockford Fosgate P3 400 / 29 / 83 The Alpine, although highly reviewed, has miserable efficiency compared to the others. I would have to use 4x the wattage to match the Infinity or JBL. Same goes for the Boston, Rockford, and Eclipse since I can't find the rating. The JL and Kicker were hard to find at much less than retail price, so I scratched them as being too expensive. The JBL's Fs was way too high compared to the Infinity's, so scratch it too. This leaves the two Infinity woofers. The Perfect is their top-end and more expensive, but does not offer me anything except a few more watts and negligible efficiency. The Kappa is easy to get for less than retail, has a stunning Fs of 20hz, great efficiency, the power handling I was looking for, it's highly reviewed everywhere I look. I might add, it's beautiful in a not everything has to be chrome and shinny kind of way. Sweet, $112 shipped. Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

I figured out why I couldn't post an image earlier. The system doesn't like images with hyphens in their name. So, here is the image I wanted to put up for step 2, on the bottom of the first page. Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

Step the fourth: select amplifier to compliment the woofer in power rating and crossover frequencies Power ratings are very often misunderstood. To skip a big rant on my part, lets just summarize that RMS power ratings are good, and MAX power ratings are bad. Also, pay attention to the impedance listed right after the wattage. If your amp can do 1kw at 1ohm but you only have one woofer at 4ohms, then you're screwed and wind up with 250w being used. Always match impedance of the woofer(s) and the amplifier. Crossover frequencies however, are really simple. I want a low-pass filter, which skims away all the high frequency signal and leaves me with just the low frequencies. From the measurements in earlier steps and experience with home theater, I know I want my crossover to be set in the 45hz to 55hz range, so I need to find an amp that can filter this low. Also, I know that certain designs like the transmission line and the bandpass enclosures have a tendency to blow up woofers if they are overdriven below the system's resonant frequency, much more easily than other boxes. This is often called unloading, where the woofer is no longer encountering resistance to it's movement from the air pressure. The only force restraining it at these frequencies is the surround and the spider materials, not the big cushion of air like in a sealed box. To counter this, I'll find an amplifier that has a subsonic filter to roll-off the frequencies below 20hz or so. Frequencies below about 30hz are often called subsonic and the consumer is often misled to believe these are "bad" or "useless" because we can't hear them. I like to think the opposite. When you experience music or movies that have sub-30hz material, there is a certain realism that shines. It's like in Jurassic Park when the T-Rex is first introduced in the movie. He doesn't make a big roar, and the characters don't really know what they're hearing when he is approaching. The big clue is the glass of water vibrating with each foot step. The audio is felt, not heard, this is what I want! So using the websites mentioned above with reviews, I narrowed it down to the following amps:                     RMS@4     RMS@2     Subsonic Alpine MRP-500          300     500     15 hz Eclipse XA1000          320     480     18 hz Kenwood KAC8104          300     500     15/25 McItosh MCC301M          300     600     20/28 All four of them have exactly what I'm looking for, and match the woofer I choose in power handling (350w RMS). I will run the woofer in 4ohm mode so the 4ohm power rating is what I'm looking at. All of these amps also have a great subsonic filter just below 20hz. I was looking at JL amps however, and their subsonic filters are set at 30hz !? For such such quality products, I cannot for the life of me figure out why they set the filters so high. Anyhow, the first one of these four I found at a decent price was a used Eclipse XA1000. The McIntosh was tough to find, and they were usually quite expensive : ) Awesome, $85 shipped. Malcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

Step the fifth: research to find useful information about building the transmission line (won't be easy!) And it certainly wasn't easy. It seems transmission line enclosures are a bit esoteric, nobody really knows how to predict it's performance but some people can often get great results by building, modifying, building, and changing a few more times. A lot of the designs I see people make are copies of one another which further illustrates how difficult it is to make something from scratch or a specific size. The infant stages of reading was based off search engines and forums which yielded mediocre results. One thing let to another I found a few people who seemed to know what they were doing: aznboi3655's thread aznboi's thread led me to these articles and later led me to haemphyst’s system Transmission Line Speakers .org Here are many projects that are single full-range woofers and some systems reach an incredible 35hz all the way up to 20khz. There is some good information on the site, and on the member's projects' sites as well. Brines Acoustics This guy builds full range transmission line speakers and sells them, but is not shy to share what he knows about building them. His site is a great resource and one of the first times I heard about Dr. Martin King's research. Pearls from Martin King Quarter Wave Design This was a huge turning point for me. To hear that somebody had a working model for building transmission lines was music to my ears. After looking around more, King's work is highly respected and his simulations are very accurate. Quarter Wavelength Loudspeaker Design If there is a person more respected in transmission line theory than this guy, I would be surprised. King's site is both the most rewarding and most frustrating source of information I found. His research is hugely in depth and at times hard to follow due to all the math, but after reading through it a few times the knowledge was amazing. This is THE site if you are competent with math and building enclosures. King's most important piece of work, in my oppinion, is the worksheet for simulating transmission lines. You have to input a whole variety of theile-small parameters from your woofer, and completely guess what your box will be like. But from reading about everybody's projects above, a pattern started emerging. I won't go into details here because the above sites cover the material so well. If you are serious about building a t-line, then do some reading and get comfortable with the concepts. When you're ready, go to King's site and pay the subscription fee to gain access to his worksheet. I promise you, it's totally worth it. I paid $25 for one year's access, with free updates and the understanding that King will reply to emails and help with questions as best he can. And yes, he did try to help me with my questions. --- Once again I've worked myself into a corner and must get some sleep. I promised some build pics and all, but they are going to have to wait. But I will say the box hits so low, I need to build a new test CD. My disc only has test tones down to 25hz and I cannot hear any roll-off from 30hz to 25hz, so the response must hit 20 with ease. It's scary what notes this low feel like in music. I keep thinking someone is opening the garage door, or we're having an earthquake so I turn down the volume all the time to try and figure out what is shaking the neighborhood. Oh wait, that's me. Also, I'm using my ASW600's amplifier since the Eclipse XA1000 is still in the mail. The ASW600 is only putting out 150w, but already the system hits harder than my cousin's dual 10" at 350w. Score one for high sensitivity woofers! Good night. -JustinMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.

Step the sixth: design transmission line with cabin gain, woofer properties, and physical limitations in mindLets start with Martin J. King's worksheet and inputting the theile-small parameters for my woofer. These numbers are found on the manufacturer's website and detail how a woofer will perform mathematically and are imperative for a good simulation.His worksheet does not deal with dual voice coil woofers unfortunately. Because I'm wiring my coils in series, I will double the Re and Lvc values when putting them into the worksheet. King agrees with this concept, but has only worked with single voice coil woofers and is not absolutely sure. Hopefully in the measuring phase I can see if this was a good idea or not.Note: Fd = Fs, Vad = Vas, Qed = Qes, Qmd = Qms, Qtd = QtsThe next step is to set the transmission line length, taper if any, and stuffing if any. This required a LOT of guess-and-check to figure out how the values effect the frequency response of the system. In this step, I was trying to construct the frequency response of my hypothetical subwoofer from step two on the first page. Remember it needs to hit -3db by 20hz, and gradually roll-off by 8db as it approaches 60hz. The dimensions must also be no greater than 34" x 33" and some unknown height to adjust for internal volume.After some quick drawings, I guesstimated I could put 120" of length inside my enclosure and still have it fit within my cargo area comfortably. So that is the length I started with, and coincidently, the length I ended with.The tapered line tends to be most popular, because it will allow the shortest line at any given resonant frequency. This means you put the woofer at the large end of a tube and taper the other end into a smaller area, much like a reverse horn but linear rather than exponential. Lots of people have had success with a ratio of between 2:1 and 4:1, so I started with these and kept massaging the numbers little by little. Eventually I settled on a 2.1 : 0.7 ratio. These ratios are based on the surface area of the woofer I'm using, 339cm^2.This is very similar to the 3:1 ratio which I loved, but the internal volume required is more in line with the space I have available. Below is the frequency response curve of the box I plan to build. Not shown here is an impedance vs. frequency graph which shows the system's resonant frequency is at 22hz. The graph below shows much of what I am trying to achieve. The -3db point is in the very low 20's, there is a roll-off going towards 60hz, and for 1-watt of power the system is really efficient.note: the red line is my box, the blue line is an infinite baffle with the same woofer for comparison. Notice how much more efficient the enclosure is? For the range I'm using, it's about 6db higher meaning 4x the output!There are dozens of graphs and ways to pull data from these worksheets and I don't want to cover them all, but there is one more I am interested in. Will my woofer be moving enough air to make a hissing noise as it passes through the tapered opening? (the terminus) To find out, we can simply scroll down a few pages to find this graph. The recommended highest air velocity is 10m/sec, and this box is close but definitely under the threshold.So there we have it. I need to build a box with 120" length of transmission line, with a taper ratio of 2.1 : 0.7 of the surface area of the woofer. The line must be folded into a box of 34" x 33" and 10.5" tall to house the woofer. The internal volume should be about 170 liters. It would be nice to have access to the entire length of the line so I can tune by adding stuffing later on.---Build pics, dimensions, and everything else to follow. The carpet will be glued on tomorrow morning, and the amplifier is arriving in the mail early this week.-JustinMalcom: "This is the captain. We have a...little problem with our engine sequence, so we may experience some slight turbulence and then...explode."

Jayne: "We're gonna explode? I don't wanna explode.