# twin 6.5" transmission line enclosure



## pauldurkin_trail (Apr 10, 2013)

Hey guys, brand new member here, and my first post is shaping up to be, well, interesting.

First off, the car audio scene is not new to me, but I am re-visiting an old passion later in life. I was into it all in a big way ( sound quality) from the early to late 1990's, but is all sort of went by the wayside (house, marriage, career... the usual suspects).

Now that I have "matured" (I think that means lost most of my hair), I am building a custom install for my car, which is a 1994 Supra twin turbo.

My listening tastes have ALWAYS leaned towards accuate, musical sounding woofers. My home audio system has a nice set of older KEF uni-Q speakers, ( they could use a bit of help in the deepest bottom end, IMO), and I like that lively, musical sound , and listen to everything from classical to metal to electronic music.

I have never been a fan of bandpass enclosures with "one note bass", and haven't ever heard a large (12"+) woofer I have liked.

OK, so the all important question is this:

"Back in the day" I always wanted to try a transmission line enclosure, but not much info seemed to be available on the ins & outs of that enclosure style at the time. Today I can look it up and calculate it no problem, but it still is a bit of a uncommon enclosure style. I don't know what to expect for its musicality, and in fact I have never even had the pleasure of hearing one in a car.

The calculations, fabrication work, fiberglass work, etc. are no problem to do, and are quite a neat project for me.

SO, I am planning on running two 6.5" subs - CDT audio ES-6MSub, and having this enclosure in the (shallow) spare-tire well of my Supra. The enclosure's interior will be much like a snail/nautilus shape within the tire well, to get the needed duct length and area for the 43hz resonant freq. and cone area of these subs. I know that the Supra's interior shape (tapered from hatch to front) SHOULD be ideal for a TL.
Being that the Supra is a performance sports car, weighing it down with a clunky (and ugly, IMO) conventional box is just not where I want to go. 

One "problem" I see, is the specification of these subs lists a Qts of .8564, with a Qms of 4.62, and (from what I have read) TL style enclosures "like" a much lower Qts.


What is likely to happen sound-wise with these drivers having this high Qts in a TL style enclosure....anyone?

Anyone here have experience with small subs in a TL that can comment on their musicality and depth?

Am I wasting my time?

PAUL


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## Orion525iT (Mar 6, 2011)

Not sure if they will work. Not too many people run t-lines. I am curious as to how you plan to build the snail though.

I have some older cdt M6plus 6.5 subs. Fs 39hz and Qts .386. I have been really wanting to try them in a t-line, they seem to be perfect for the job.


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## Brian Steele (Jun 1, 2007)

Given your vehicle and your listening tastes, I'd suggest something that's capable of a bit more output while still sounding clean. 10" or 12" driver (or two!) in a simple sealed box comes to mind immediately. Easy to build, and you'll get excellent results if you use a good driver. 

If you still want to look at TLs based around 6.5" drivers, have a look at the Exodus Anarchy 6.5" driver or the Tang Band W6-1139SIF, both of which have specs that suggest decent output capability if used in a subwoofer design.


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## jpswanberg (Jan 14, 2009)

go over to pwkdesigns.com. There are a number of those designs on his website. Please note that if you ask him to design a subsystem for your car, it may or may not be a transmission line design, all depending on what his program(s) tell him concerning what will work best in your situation. JPS


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## SynRG (Jul 30, 2007)

Brian Steele said:


> Given your vehicle and your listening tastes, I'd suggest something that's capable of a bit more output while still sounding clean. 10" or 12" driver (or two!) in a simple sealed box comes to mind immediately. Easy to build, and you'll get excellent results if you use a good driver.
> 
> If you still want to look at TLs based around 6.5" drivers, have a look at the Exodus Anarchy 6.5" driver or the Tang Band W6-1139SIF, both of which have specs that suggest decent output capability if used in a subwoofer design.


Ditto on these driver recommendations. Also the Sundown SD-8 might be a good marginally larger driver with plenty of displacement to experiment with at a reasonable cost. 

Also be sure to search on Patrick Bateman's posts. He has done considerable research in this area regarding TL's and derivatives. Main drawback to TL is the size of the enclosure, and as with other designs potential SPL output as a function of driver displacement. If you can cope with size and have reasonable expectations of the SPL output for the drivers you have selected it can be a very natural sounding solution. 

Some of the best subs I have heard are TBI home subs which are said to be a TL derivative design. Limited output due to eight inch driver used with limited displacement but sounds very natural. 

You may also find it interesting to explore enclosures made using a Fibonacci Spiral. Since you are using a fairly small driver, this type of enclosure might fit in your spare tire area. 

Good luck with your design. Be sure to post here. I appreciate your sense of adventure and eagerness to learn and try something different.


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## I800C0LLECT (Jan 26, 2009)

I don't mind watching this develop. I'm hoping to hide a simple horn as close as possible to the firewall using a 6.5" sub myself. My backup plan is just to port it up front.


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## SynRG (Jul 30, 2007)

Oh, one more thing. Since your design might be a little more complex than a simple box, you might be interested in searching on building enclosures using foam craft board. Search for "diyaudio full range foam core board speaker". This lets you prototype a potential design quickly and cheaply for proof-of-concept. You could also use 3/4 foam building insulation sheets and the adhesive that is specifically for that foam in the caulk section if you need a heavier material. Once you lock in on the design you can then build final version in more durable materials. May be helpful to help you work out a more complex design and minimize cost for prototyping the design.


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## chad1376 (Dec 27, 2012)

I'm no technical help - but I am interested in how this develops. 

Many-many years ago I built a TL with a cheapo Radio-Shack 8" DVC sub. I didn't do any "real" calculations, other than setting the length at 1/4 the wavelength at 50-hz (or something). I was very surprized and pleased at both the sound quality and efficientcy. Some day, I would like to do another, more upscale version.

Good Luck and please post progress as you dive in.


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## 94VG30DE (Nov 28, 2007)

Sweet car, so I'll post. 
I love using the spare tire well area, and 100 internet points for using the word nautilus. However, please don't discount all 12s as not sounding good. I have heard 15s sound great in a car, it just depends on what you put them in. 
A search for threads started by Patrick Bateman will get you some good reading material on atypical enclosure designs. Personally, if you have decent processing and power available, I would be stuffing 8" high-displacement subs in sealed enclosures and putting in as many as you can fit.


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## Justin Zazzi (May 28, 2012)

pauldurkin_trail said:


> What is likely to happen sound-wise with these drivers having this high Qts in a TL style enclosure....anyone?
> 
> Anyone here have experience with small subs in a TL that can comment on their musicality and depth?
> 
> Am I wasting my time?


Not wasting your time at all! If the goal is to have small subwoofers to save weight and keep your amplifier demands small as well, then you are on the right track. The tradeoff of course will be enclosure size; it will have to be larger than normal to give you the efficiency you will need to make up for the lower power and smaller drivers.

When I built a transmission line for my car, the only person with significant research, models and equations was Martin J. King at quarter-wave.com. You could purchase his modeling equations, but his free resources are still excellent. He has a page called Classic Transmission Line Enclosure Alignment Tables  that detail some of the differences in frequency response as you change a single variable at a time (tapered or expanding line, stuffing density, driver T/S paramaters, etc) and on page 19 you will find his summary of how a driver's QTS makes a difference.

Some tips I have found common along the way: model the total length of the line to be roughly the resonant frequency of the drivers you are using, and have a cross-sectional area of no less than 1x to 1/2x the area of the drivers depending on their displacement. If you want to taper the line, a 3-to-1 ratio is common (something like 2.1 area near the woofers tapered down to 0.7 area near the terminus, or end).

I also recommend looking for Patrick Bateman's notes on transmission lines, folded horns and other large enclosure subwoofers. From other research, it seems that placing your two drivers along the long dimension of your line provides best results by exciting multiple nodes in the line and "spreading the chaos" as some have labeled it. Using a spiral shape is a smart use of the space in the spare tire well, I like it!

As for musicality, they are awesome and you should not be disappointed. A transmission line will play much louder than a sealed box so I would not worry too much about their output considering you enjoy realistic rather than boom boom. As for depth, they dig deep! I had a single 10" fed by 300 watts and it was enough to seriously modulate your voice during when talking and playing a 25hz tone : )


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## phxdemon (Jan 13, 2013)

jpswanberg said:


> go over to pwkdesigns.com. There are a number of those designs on his website. Please note that if you ask him to design a subsystem for your car, it may or may not be a transmission line design, all depending on what his program(s) tell him concerning what will work best in your situation. JPS


Agreed. This guy knows what he is doing and designs/build subwoofer boxes for a living.


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## pauldurkin_trail (Apr 10, 2013)

First off, let me say WOW! 
Thanks for all the positive responses to my little adventure into TL land.
Jazzi, I was planning on putting the two drivers "in line" (mainly for space saving issues with the design), and hadn't really given much thought that each would hit slightly different tuned frequencies, which could work out nicely in my favour.
I'll post some pictures as this little project takes shape. I know that not too many people have seen the shape of a MKIV supra's spare tire well, but it seems to lend itself to this "curled" transmission line shape very, very well. 
I am not an SPL guy, never really have been, so I think this enclosure choice could work nicely. 
Also, I am hoping that the completed enclosure weighs around the same amount as the 17" temp. spare that is being removed from the tire well.... I might just have to do a weight comparison once its all finished up.

BTW :94VG30DE, I actually have heard a large (15") sub setup that I liked at an IASCA SQ event around 1993 or so. 
"Never" shouldn't have been the term I used, more like "rarely" in regards to large subs.
That car made excellent use of some 8" midbass drivers, and the 15 was filling in that bottom end in a beautiful way. Cant remember whose car, or even what the hell it was (some random 4 door sedan), but it was a very, very well sorted SQ setup for the time.


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## Brian Steele (Jun 1, 2007)

pauldurkin_trail said:


> I am not an SPL guy, never really have been, so I think this enclosure choice could work nicely.


Using bigger drivers is not always about SPL. There's that "noise floor" in car audio that you need to get above, and much of this appears at lower frequencies. Using larger drivers allows you to get above this noise floor with less distortion.

Anyway, looks like my next build is going to be "small driver" one too, though in this case the "small driver" in question (and there are going to be two of them) is Alpine's 8" Type R subwoofer. About 3 cu.ft. of T-line or Tapped Horn - haven't decided yet. Probably not going to fit in the spare tire well .


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## I800C0LLECT (Jan 26, 2009)

Hopefully nobody hates me for this....I picked up two Hybrid Audio I6SW's for my venture  (they were cheap!!)


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## pauldurkin_trail (Apr 10, 2013)

Well, took my first step towards this interesting enclosure:

I spent QUITE some time preparing the spare tire well for fiberglass. I did a layer of duct tape, then a couple layers of tin foil with packing tape on the seams. I also built a couple small "backing sections" to smooth out a couple odd edges in the well's shape that would have been a PITA to fill with layers of fiberglass.

You can see the shape of the well makes for a close-to nautilus shape, thanks to Toyota's shaped-foam jack & tool carriers, and the "hump" that covers the fuel-pump access.

I think the two 6.5" will go in the top, left hand corner, to "start" the T-Line, as the "line" compresses slightly from that point, going clockwise. Sorry, the side view pics didn't get rotated for some reason





my handy-dandy foil, tape, and backing modifications (almost finished):



Well, heres hoping that all goes well with the fiberglass, and the stench comes out of my car in short order!


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## Oscar (Jun 20, 2010)

Don't wonder, model it. You can get decent approximations using Hornresponse and with Akabak.

Also, I would have just cut out the whole "bumped" section since you're not gonna carry a spare, and welded it flat to get more space in there.


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## pauldurkin_trail (Apr 10, 2013)

Oscar said:


> Also, I would have just cut out the whole "bumped" section since you're not gonna carry a spare, and welded it flat to get more space in there.


Sorry, absoloutely NO way that is going to happen.
Two reasons - the first is that the top of the fuel tank comes up to the center of the bump, where the fuel lines exit the pump.
The second reason is that the car is a MKIV Supra, twin turbo, 6 speed hardtop. 
These cars make Lamborghinis look commonplace, which means that cutting the car up is a no-fly zone for me.


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## Orion525iT (Mar 6, 2011)

pauldurkin_trail said:


> Sorry, absoloutely NO way that is going to happen.
> Two reasons - the first is that the top of the fuel tank comes up to the center of the bump, where the fuel lines exit the pump.
> The second reason is that the car is a MKIV Supra, twin turbo, 6 speed hardtop.
> These cars make Lamborghinis look commonplace, which means that cutting the car up is a no-fly zone for me.


So its more a ring t-line than a nautilus t-line.


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## pauldurkin_trail (Apr 10, 2013)

Orion525iT said:


> So its more a ring t-line than a nautilus t-line.


Yes. That would be a better description of it. I can get all the `port`length I need for the 43hz Fs of the drivers without having to curl around more than once.


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## Jroo (May 24, 2006)

Im gonna watch to see how this turns out. I have done the "math" several times to see what a 1/4 wave will look like and they always end up taking half my hatch. If your port length is tuned to get 43, how much lower will this truly play? So can a line that is tuned to Fs of 43 reach into the 30's? I see this as a lot of work to get what a 10" or 12" would do in a sealed box using a smaller space.


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## pauldurkin_trail (Apr 10, 2013)

Well, heres what I am hoping for: (and why I chose to go this way).

I feel that the 6.5" driver's 43hz Fs and TL tuning SHOULD let it play cleanly down into the low 30's bracket somewhere.
I can HOPE for lower, and have read that TL configurations can play almost one octave lower than the tuned frequency quite cleanly. That translates to about 21-23 hz, if I'm not mistaken. 
In reality, that sounds quite optimistic to me.

CTD's provided info pack on these woofers shows several different ported configurations hitting between 22-28hz on a graph before dropping off. (most have a 2-3db hump at 45-50hz, dropping to a 0 hz gain at 22-28hz ).
What it doesn't say is if that is factoring in cabin/room gain or not, and how they actually sound at those frequencies.

Regardless, I would be building a fiberglass tire well enclosure if I were to go ported, sealed, or a TL.
I just don't want a clunky "box" in my hatch area at all for this car. (and I have a couple gallons of resin around from a boat repair project that "need" to be used up  )

The actual difference in effort doing a "curled" TL in this car isnt too awful much more than something more conventional using a larger driver in this particular tire well area. A little more fiberglass, but not really too much more effort.

I hope to have a fairly light, fully concealed enclosure that makes "musical" bass down to frequencies that seem to defy what I think a 6.5" woofer is capable of.

I'll update as progress happens.


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## Justin Zazzi (May 28, 2012)

Jroo said:


> Im gonna watch to see how this turns out. I have done the "math" several times to see what a 1/4 wave will look like and they always end up taking half my hatch. If your port length is tuned to get 43, how much lower will this truly play? So can a line that is tuned to Fs of 43 reach into the 30's? I see this as a lot of work to get what a 10" or 12" would do in a sealed box using a smaller space.


A small sealed box could reach a similar volume level and frequency response, but at the cost of more amplifier power and requiring more displacement (bigger speaker, or more of them). The transmission line is a tradeoff that has increased efficiency and lower frequency response but at the cost of a larger enclosure size. So you can use smaller or less robust speakers and amplifiers with the T-line to achieve similar results to a sealed box in exchange for a larger box. Other enclosures like ported, bandpass, and horns also share tradeoffs like this.

-J


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## Justin Zazzi (May 28, 2012)

pauldurkin_trail,

Do you know what length of line you are planning on building? Roughly 7 feet is the quarter wavelength of 40hz, and about 9 feet is quarter wavelength of 30hz. You should keep in mind that when playing frequencies below the final in-car fully-assembled tunning frequency of the sub, the woofers will not have any resistance to their movement (sometimes called "unloading"). So if your installed resonant frequency is 40hz, then you will really want a subsonic filter just below that to prevent damaging your woofers. Most subwoofer amplifiers have a filter like this built in, thankfully.


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## pauldurkin_trail (Apr 10, 2013)

I have measured out a 78 to 80" total line length possible in this area, from the magnet of the woofer to the terminus of the TL. That works out to 42-43hz tuning frequency on a non-tapered TL (which matches the Fs of the drivers). 
It was measured using string down the center of the proposed pathway, and should be accurate to within an inch.
By the existing shape of the tire well, and its "hump" location, this TL will be a tapered design, somewhat tightening down its length, which makes the effective tuned frequency drop, according to the TL alignment papers from Martin King.

I'll have to do some more math as this goes along, to attempt to estimate the "true" tuned frequency of this tapered, curled TL.

This all gets more and more interesting!


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## thehatedguy (May 4, 2007)

I hate to be a naysayer, but I just don't see this working like how it is planned in the space you are talking about.


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## chad1376 (Dec 27, 2012)

Crazy Idea - what if you added internal baffles to increase the effective length of the line. My sketch is laughably crude, but gets the concept across.


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## Oscar (Jun 20, 2010)

pauldurkin_trail said:


> and have read that TL configurations can play almost one octave lower than the tuned frequency quite cleanly. That translates to about 21-23 hz, if I'm not mistaken.
> In reality, that sounds quite optimistic to me..


It is quite optimistic. What you likely read, or what was meant to be said, was that you can *tune* them an octave lower than the _Driver Fs_, but not drive them an octave lower than the main _tuned frequency_. No way it's gonna happen, as it will quickly unload below the main Fb, just like a standard ported box where the vent no longer loads the driver's cone, and you'll quickly mechanically damage the speaker.

This is where simulations are worth their cyber-weight in gold. You can see and investigate things like this if you model them properly and leave nothing to optimism/mysticism/anything-cism


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## thehatedguy (May 4, 2007)

Have you thought about a tapped horn?

More efficient than a TL. There is a thread or two over on DIY Audio about some using SDX7s...I think they were called "unhorn" or something like that. Rather small, but still too large to fit in the massive tire well in my IS300.


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## pauldurkin_trail (Apr 10, 2013)

Thanks for everyones input!

I have done a bunch more math and research on TL enclosure design, (thanks to Martin King's TL tables, and quarter-wave.com), and have come up with something that sounds extremely promising for the space I am working with.

Since my ultimate line length is limited to approx. 78-80 inches, I did a bunch of research on tapered TL designs, and their benefits. From there, an interesting bunch of math calculations (and re-calculations...and re-re calculations :inquisitive came up with a very nice outcome.

It seems that I will be able to achieve an actual tuned frequency of between 32 and 33 hz by designing my TL to have approx. 77.79 square inches of area at the driver end, and compressing down to 51.34 square inches at the terminus.

This tapered shape should lend itself very nicely with the tire well's limitations, and allow me to maximize the somewhat limited length available in the space. Adding in a taper to the equation of calculating a TL enclosure makes for some VERY interesting possibilities!


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## thehatedguy (May 4, 2007)

Yeah, that would be a better way of doing things.


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## Patrick Bateman (Sep 11, 2006)

ugh this won't end well.

Transmission lines are big, they are power hungry. Designed properly, you're basically nullifying the rear wave. That requires a lot of space and a relatively complex enclosure.

I built a transmission line with a pair of Dayton DVC 12s, and it was way more trouble than it was worth. It basically sounded a *little* better than a sealed box... just barely. And it was huge and needed gobs of power.

And you're trying to do this with six inch drivers?!
in a SUPRA?!

Colossal waste of time and money.


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## Patrick Bateman (Sep 11, 2006)

pauldurkin_trail said:


> Well, heres what I am hoping for: (and why I chose to go this way).
> 
> I feel that the 6.5" driver's 43hz Fs and TL tuning SHOULD let it play cleanly down into the low 30's bracket somewhere.
> I can HOPE for lower, and have read that TL configurations can play almost one octave lower than the tuned frequency quite cleanly. That translates to about 21-23 hz, if I'm not mistaken.
> ...


I don't get it.

In a car, the challenge isn't getting a woofer to play to 20hz. Even a 4" woofer can play to 20hz in a car due to cabin gain.

In a car, the challenge is LOTS of clean output. The other challenge is that you get a lot of ugly peaks and dips in the response, plus an impulse response that's completely nuts, due to all the reflections.

I think this is the reason a lot of people get good results when they stick a sub up front. It's not because the sub is up front; it's often because there are TWO subs, spaced about eight feet apart, and that makes the peaks and dips in the response curve less severe, plus it smooths out the impulse response a bit.

But transmission lines don't solve either of these problems, in fact they make them worse because transmission lines don't give you as much output as other box types such as sealed, vented, tapped horns, etc. (A lot of this depends on the construction of the box; I can make a transmission line with the same response curve as a vented box, but the vented box will be more space efficient simply because the vented box requires less wood. This is one of the reasons that I use crazy composites in some of my sub boxes, it allows me to use walls that are thinner.)

Hoffman's Iron Law rules above all, and anyone that says that a transmission line can make a woofer play lower than a vented box doesn't understand how Hoffman's Iron Law works.


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## I800C0LLECT (Jan 26, 2009)

My reading tells me that tapped horn has more potential. That's the road I'm headed down if I could ever get hornresp downloaded


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## Patrick Bateman (Sep 11, 2006)

I800C0LLECT said:


> My reading tells me that tapped horn has more potential. That's the road I'm headed down if I could ever get hornresp downloaded


Tapped horns are very trendy right now, and they're one of my personal favorites. But Hoffman's Iron Law rules over all, *and it's possible to generate equal or even higher output with a plain ol' sealed box.*

The best box will really depend on how much you have to spend, the space the box is going into, and which variables you want to maximize.

For instance, I can make a tapped horn that can hit 140dB with a single 15" woofer that costs $300. But I can also hit the same level with a lot of sealed boxes. But the sealed boxes will cost more.

I can make a vented box that's louder than both of those boxes, if I'm willing to live with a group delay curve that makes the box sound like it's farting.


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## pauldurkin_trail (Apr 10, 2013)

Patrick Bateman said:


> ugh this won't end well.
> 
> Transmission lines are big, they are power hungry. Designed properly, you're basically nullifying the rear wave. That requires a lot of space and a relatively complex enclosure.
> 
> ...


Patrick:

Thanks for your input on this. 

I do debate the idea that this would somehow be a "colossal waste of time and money", however.

Mainly, I would be doing a spare-tire enclosure for this car no matter what. So, 80% of the actual work/time in doing the fiberglass would be happening regardless if it were to be a sealed enclosure, or the TL idea. 
I would be making the same fiberglass piece regardless.

Also, the money "waste" is a moot point. The fiberglass is free. It is leftovers from a boat project from a couple years ago, and the resin will soon go bad if it is not used up.

Mainly, I am into this for the price of a 1/2 sheet of birch ply ($30 CDN), the two drivers, and any finish work I choose to do.

Now, lets say the TL design doesn't work out, it sounds like a frozen turd, and has the output of a transistor radio.

Then , it looks like I'll end up changing out the "lid" of the enclosure ($30 for more birch ply), and get ahold of a 10", and run it as a sealed enclosure, which I have had before.
The 6.5" drivers could then be used elsewhere, and I will have satisfied my curiosity about this "tire well" TL idea, and be no worse off.


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## 94VG30DE (Nov 28, 2007)

pauldurkin_trail said:


> Patrick:
> 
> Thanks for your input on this.
> 
> ...


I think he's referring to the time more than the money. The TL would be far more complex than a simple sealed box. If the result is no better than sealed box, then you just 'paid' all that time to 'learn' something that is already being suggested. 
But it's a hobby, so do what you want


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## Patrick Bateman (Sep 11, 2006)

All enclosure types have their pros and cons. And all enclosure types are subject to Hoffman's Iron Law. Sealed boxes are simple, idiot proof, and have the potential to generate the most output with the least space IF you have enough power. (They're power hungry.) Vented boxes are much more complex, but if done properly, you can sacrifice good phase response for higher output over a narrower range. You can also tune a vented box for *wider* bandwidth at the expense of efficiency.

The most attractive thing about transmission lines is that you can just nuke the rear wave. Designed carefully, you end up with a box that sounds a bit like a sealed box. And like a sealed box, the transmission line has low efficiency. Flip a transmission line on it's head, and you have a back loaded horn. And a horn has the *opposite* advantage than a transmission line. Instead of muting the output of the rear wave, you're amplifying it. Transmission lines and back loaded horns are two sides of the same coin.

Due to their low efficiency, the best drivers for sealed boxes are drivers that have a LOT of xmax, and a LOT of displacement. Twelves and fifteens are great candidates for sealed boxes, and they're also great candidates for TLs.

And *that* is the main reason I do a facepalm when I read this thread. A 6.5" woofer is a TL will be anemic in a luxury car. I should know, my car has an 8" woofer and I hate it! At any speed over 30mph, I can't hear my sub.

So the idea of a 6.5" woofer in a Supra is just silly. You won't be able to hear it.


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## Patrick Bateman (Sep 11, 2006)

Oh, the other reason that transmission lines in the car are dumb is because aperiodic boxes achieve the same goal with less space.


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## thehatedguy (May 4, 2007)

Sealed 12 or 15 in the tirewell= done.

2 6s are small for a midbass much less a sub.


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## I800C0LLECT (Jan 26, 2009)

I definitely don't see any advantage to 6.5" in a trunk. Up front is a different story imo. But before I start playing with hornresp I'll be building a vented design. I'm in agreement with everybody here thus far. If using the trunk I think you should go a different route.

Due to Hoffman's Iron Law my goal isn't low lows, never was actually. I'm fine only going as low as 40hz. *shrug* I think that's where the op and myself differ in perspective.

My factory setup has an 8" below the rear deck that is just awful. Still interested to see how his idea turns out. I won't be able to build anything until my deployment is over.


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## pauldurkin_trail (Apr 10, 2013)

Patrick Bateman said:


> ugh this won't end well.
> 
> Transmission lines are big, they are power hungry. Designed properly, you're basically nullifying the rear wave. That requires a lot of space and a relatively complex enclosure..


Patrick: I noticed in this quote, you state that a TL enclosure is "basically nullifying the rear wave" from the driver.
This seems to fly in the face of what is researched/reported by Martin King's papers on TL enclosures, in which the rear wave is utilized as output from the terminus. 
Am I misunderstanding something?


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## n_olympios (Oct 23, 2008)

Read this:

Folding up | PS Audio


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## pauldurkin_trail (Apr 10, 2013)

Well, this little project is nearly complete!

Let me start off by saying that the dual 6.5" cdt ES6m Subs have far exceeded what I thought possible for their size, and running them in a hybrid, tapered transmission line is just fantastic!

There is MORE than enough output for my listening pleasure, and it is very amazing to hear these tiny drivers perform.
The best description of the sound of this TL is the bottom end depth of a high-quality single 10" in a properly-sized enclosure with the tightness and "snap" of dual 8's.


I'm not sure if that makes any sense to read, as it is hard to describe the exact sound "qualities" in words, but I am very , very happy that I decided to go through the calculations and research for Transmission Line enclosures.

As a little side bonus, The whole enclosure weighs slightly less (by feel) than the 17 inch temp. spare. I'll have to get out the scale and give some exact weights.

I am powering it from two channels of my old-school Alpine MRV-F400, an "oldy-but-goody".

Anyhow, on to the pictures!

Lid off, you can see at the driver end of the line, I went with some fiberglass under the drivers, and starting down the line a bit. I have not done any playing with that, just made a "that looks right" guess. I'll play with it more as time allows. 
At the terminus end of things, I applied some sound-deadener material, as I wanted to avoid any weird possible vibrations as the soundwaves make some abrupt turns in that area. I'll need to use some urethane sealer at all the edges to make sure no lifting happens over time.

Sorry about the weird shadowing and funny angle, it makes the "line" look a bit wonky. The sun was beating down hard today, and I couldn't see the screen on my camera well when I took this pic!




With the lid on, screwed down against the urethane gasket material all around. I will likely re-finish the topside of the enclosure and smooth out around the terminus top, but that will wait until I'm finished "tuning" the fiberglass fill.
I still need to fabricate up some protection for the drivers and to prevent crap from falling into the terminus too, but you get the idea.





Thanks to all who gave me solid information on here, especially Jazzi, who posted info and links to Martin King's research. That really helped keep me going with this idea, and let me research, learn, and calculate how to make this idea work in this unusual way and space. Thanks!


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## phxdemon (Jan 13, 2013)

Nice progress!!


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## Justin Zazzi (May 28, 2012)

pauldurkin_trail:

Glad we could help! Thanks for coming back to post the results.

Also, what did you use to build the walls of the enclosure? I do not recognize it from the photo.


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## pauldurkin_trail (Apr 10, 2013)

The walls are fiberglass, made with a couple different weaves in different areas. Imperfections were filled with long-strand kitty hair for the interior and smoothed.
I just gave the exterior a rough sanding, as its not visible.
The top "ring" is made of birch ply, and was fiberglassed in place, then sealed with a high-strength urethane sealer / adhesive.
The enclosure is coated inside and out with spray-on bedliner over top of the fiberglass, and the top "rings" were then coated with flexible urethane for a "gasket" that the birch ply lid seals against.


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## Patrick Bateman (Sep 11, 2006)

pauldurkin_trail said:


> Patrick: I noticed in this quote, you state that a TL enclosure is "basically nullifying the rear wave" from the driver.
> This seems to fly in the face of what is researched/reported by Martin King's papers on TL enclosures, in which the rear wave is utilized as output from the terminus.
> Am I misunderstanding something?


Depends.

Let's say you have an exit that's larger than the mouth. When you do that, you have a back loaded horn. As the exit gets smaller, it starts to move from being a back loaded horn to being a transmission line. *But at the same time, the output from the far end of the line is reduced.*

Generally transmission lines are designed so that the impedance peak of the woofer is reduced.

Doing this reduces the resonance that occurs at the Fb of the enclosure.

If you looked at a waterfall plot of an enclosure, you'd see there's a big 'hump' at the Fb of the enclosure. And that hump in the waterfall stores energy, which tends to make an enclosure sound 'slow.'


This is one of the reasons that ribbons can sound good; ribbons don't have that big resonant peak at Fb. And conversely, it's the reason that bandpass boxes can sound 'slow'; bandpass boxes have a resonant peak that's right in the middle of the passband.


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## pauldurkin_trail (Apr 10, 2013)

Patrick: I have noticed that you choose to express your opinions in fairly absolute terms.

I think by using over-statements such as these:



> Transmission lines are big, they are power hungry. Designed properly, you're basically nullifying the rear wave.





> The most attractive thing about transmission lines is that you can just nuke the rear wave.


I was unsure if you were even talking about the same enclosure type. By using the terms "nullifying" and "nuke", it sounded like your opinion was that TL enclosures make little or no use from the rear wave, when quite the opposite is true.

Also, when strong opinions such as these are voiced:



> A 6.5" woofer is a TL will be anemic in a luxury car.





> So the idea of a 6.5" woofer in a Supra is just silly. You won't be able to hear it.





> ugh this won't end well.





> Colossal waste of time and money.


It leaves a person open to having some backpedaling to do if proven wholly, or even partially incorrect after stating such strong opinions.

As a person seeking information from this forum, your opinions COULD have been mistaken for facts derived from experience. 
Fortunately, I chose to research my topic (thanks to those members kind enough to post useful links) and form my own opinion about the advantages or disadvantages of a TL enclosure for my application, and desired outcome.

Interestingly, none of your strong opinions about the enclosure style I chose to research and build have come true.

I am very happy that I have enough experience in life to be able to filter out such bold opinions presented as factual information.
Someone 20 or so years younger than myself may not have been able to see through the façade to get to the actual facts.


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## Justin Zazzi (May 28, 2012)

If you were more familiar with some of Patrick's experiments and musings, then yes, a 6.5" woofer transmission line might appear small, boring, and inadequate  I do love his work though, and his eagerness to share and contribute.

But ... you do have a point. Sometimes, that's just the way it works.

-J


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## Patrick Bateman (Sep 11, 2006)

pauldurkin_trail said:


> Patrick: I have noticed that you choose to express your opinions in fairly absolute terms.
> 
> I think by using over-statements such as these:
> 
> ...


There's no magic formula to making bass.
It's not about buying unobtanium woofers.
It's not about using a $2000 amplifier.

Making bass is about DISPLACEMENT.

Pure and simple.

And a $50 12" woofer in a sealed box has more displacement than a couple of seven inch woofers.

As Jason Winslow wisely observed, "2 6s are small for a midbass much less a sub.
"


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## mattyjman (Aug 6, 2009)

i haven't read the whole thread (skimmed, really) but isn't the final product just a ported box? excuse my over simplification, but from the looks, that's all it seems to be.


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## Oscar (Jun 20, 2010)

mattyjman said:


> i haven't read the whole thread (skimmed, really) but isn't the final product just a ported box? excuse my over simplification, but from the looks, that's all it seems to be.


Exactly why you should read whole threads. 

I for one would like to see quantitative data to back up the said performance of this project. No project is complete without data. Meaning bust out the impedance curve and the frequency response curve normalized to 1W/1m levels.


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## Brian Steele (Jun 1, 2007)

mattyjman said:


> i haven't read the whole thread (skimmed, really) but isn't the final product just a ported box? excuse my over simplification, but from the looks, that's all it seems to be.


It's a 1/4 wave resonant enclosure. More a tuned pipe than a transmission line IMO. The output should be similar to a vented box, but maybe with a bit more low end output, and quite likely a deep null around 150~200 Hz, a "feature" of these types of enclosures. I'm guessing the Fb is around 40 Hz or above, which should be ok for those 6.5s. 

I think it's an interesting approach to a spare tire well enclosure. I might've tried using that space in the center and start the line from there instead of blocking it off and leaving it unused, but that's just me. Another possibility is to use that empty space as a tuned resonant enclosure to reduce the out of band port resonance, but that might take a lot of fiddling to get right. 

Concerning what to expect from it, maximum SPL (or the ability to produce low bass without noticeable distortion) would of course be limited due to the size of the drivers. My first car audio subwoofer used two 6.5" drivers. My current one uses two 12" drivers. Of course there is a noticeable difference in output capability and distortion (measured and audible) when using larger drivers with more excursion capability. However, if the builder is happy with what he came up with, who are we to tell him that he shouldn't be?


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## Brian Steele (Jun 1, 2007)

Oscar said:


> I for one would like to see quantitative data to back up the said performance of this project. No project is complete without data. Meaning bust out the impedance curve.


Agreed.


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## Oscar (Jun 20, 2010)

Brian Steele said:


> It's a 1/4 wave resonant enclosure. More a tuned pipe than a transmission line IMO.


Are you saying this because of the taper ratio?


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## Brian Steele (Jun 1, 2007)

Oscar said:


> Are you saying this because of the taper ratio?


Yep. It seems quite low from the pictures.


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## Oscar (Jun 20, 2010)

Brian Steele said:


> Yep. It seems quite low from the pictures.


low "numerically" or low as is "nearly non-existent"?


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## pauldurkin_trail (Apr 10, 2013)

Patrick Bateman said:


> There's no magic formula to making bass.
> It's not about buying unobtanium woofers.
> It's not about using a $2000 amplifier.
> 
> ...


I'm rather enjoying this overstatement stuff now.

Unobtanium woofers? Is that what CDT audio is calling these subs now? They sure have some creative marketing terms.
And I did not know that my alpine MRV-F400 had such a high value! whew....$2000??  Would you like to buy it? Its for sale at that price!

Fortunately, you are right about the 12" woofer......it is bigger. 

Anyhow, if what I wanted to do was simply throw some bump in the back of my car, I would have done just that. A $50 12" sub in a box. Sweet. 
I'm sure my ears would never know the difference.....


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## mattyjman (Aug 6, 2009)

wow... you totally got patrick wrong, dude...


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## mattyjman (Aug 6, 2009)

Oscar said:


> Exactly why you should read whole threads.
> 
> .


dont get flippant... i read enough to understand what the objective was... just noting that from what i saw it looked like a box with an external vent is all.... im not a know it all, thus my initial disclaimer.


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## subwoofery (Nov 9, 2008)

mattyjman said:


> wow... you totally got patrick wrong, dude...


Agreed... Unsubed

Kelvin


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## Justin Zazzi (May 28, 2012)

Can you blame someone new to the forum (14 posts) who has seen almost nothing but negativity in the first thread he starts for being defensive?

I'm surprised at the lack of support, all the nay-sayers, and especially the elitist attitude of "I wouldn't like it so your ideas are terrible". I thought this was a place to collaborate and encourage the diy'er.


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## Hoye0017 (Mar 23, 2010)

Jazzi said:


> Can you blame someone new to the forum (14 posts) who has seen almost nothing but negativity in the first thread he starts for being defensive?
> 
> I'm surprised at the lack of support, all the nay-sayers, and especially the elitist attitude of "I wouldn't like it so your ideas are terrible". I thought this was a place to collaborate and encourage the diy'er.


Word. Check out the thread titled "lots of amps" same thing there. I hope There's more of us out there looking for something new. All build threads are starting to look way too similar.

Thank you, OP for sharing your experience. It inspired me to try some new enclosure designs in future installs. I'm glad you like it and I can see how it would work well in a Supra. By the way, got any pics of the car? I can appreciate how rare it is.


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## Orion525iT (Mar 6, 2011)

Jazzi said:


> Can you blame someone new to the forum (14 posts) who has seen almost nothing but negativity in the first thread he starts for being defensive?
> 
> I'm surprised at the lack of support, all the nay-sayers, and especially the elitist attitude of "I wouldn't like it so your ideas are terrible". I thought this was a place to collaborate and encourage the diy'er.


I am not sure I have seen much negativity, just sound advice from people with tons of experience. Advice from people who have gone through years of design, empirical testing and all form of contortions to try something new or to get more out of a design.

Its not about trying new things. Sub frequency is all about displacement, period. Point is, for the same money (or nearly) and space, a 15" or even an 18" would do just as well if not better and for a fraction of the design time and effort. With todays drivers, and todays amp power (especially class D), plain old sealed has a lot going for it. That is the major point here. 

You have to remember, this thread will be referenced for the next "new guy". It would be unfair, and honestly improper, not to mention the alternative, proven configurations. These new designs and experiments mean absolutely nothing if there is not a qualitative and quantitative comparison. Without that, these experiments are worthless. In any case, its not like this configuration hasn't been tried before.


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## Patrick Bateman (Sep 11, 2006)

Orion525iT said:


> I am not sure I have seen much negativity, just sound advice from people with tons of experience. Advice from people who have gone through years of design, empirical testing and all form of contortions to try something new or to get more out of a design.
> 
> Its not about trying new things. Sub frequency is all about displacement, period. Point is, for the same money (or nearly) and space, a 15" or even an 18" would do just as well if not better and for a fraction of the design time and effort. With todays drivers, and todays amp power (especially class D), plain old sealed has a lot going for it. That is the major point here.
> 
> You have to remember, this thread will be referenced for the next "new guy". It would be unfair, and honestly improper, not to mention the alternative, proven configurations. These new designs and experiments mean absolutely nothing if there is not a qualitative and quantitative comparison. Without that, these experiments are worthless. In any case, its not like this configuration hasn't been tried before.


^^^ this post sums up my feelings on this better than I could



People were telling ME similar things back when I was doing tapped horns with eights. They were basically saying "a sealed box with a high excursion twelve will generate more clean output without the hassle"

At the time, I didn't want to hear it. It's FUN making weird boxes.

But they were right, and I put my money where my mouth is. I threw away my transmission line on Tuesday, and I threw away the "triple 8" tapped horn last year. I also threw away my 10hz tapped horn that I documented over on diyaudio.

If anyone wants to purchase the drivers, they're for sale on Craigslist in Seattle


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## Justin Zazzi (May 28, 2012)

I see where you're coming from, I get it. For any generic installation advice for a subwoofer you would make recommendations based on your years of experience and so on. That advice will serve the next guy who wants to learn, absolutely.

But for this particular car, with all of the constraints, that advice does not help at all. Reread the OP's stated goals:



pauldurkin_trail said:


> ...I am building a custom install for my car, which is a 1994 Supra twin turbo...
> 
> ...SO, I am planning on running two 6.5" subs - CDT audio ES-6MSub, and having this enclosure in the (shallow) spare-tire well of my Supra. The enclosure's interior will be much like a snail/nautilus shape within the tire well...
> 
> Being that the Supra is a performance sports car, weighing it down with a clunky (and ugly, IMO) conventional box is just not where I want to go....


So he has a rare sports car that cannot be modified, wants to save weight and has limited space, seems to already have two woofers on-hand, and the shape of the enclosure is already dictated by the shape of the spare tire well.

No matter how many times you suggest that larger woofers and more displacement is better, there is no way he will be able to fit a 15" or 18" into that space (look at the photo!).

So the advice is good, but not usable. Then you continue to warn against him not using your advice, even though he can't. It just doesn't make sense, and helps no one.

Do you still not see why this is frustrating?

I don't know why I'm so worked up over this, it's not even my project. But this same kind of thing happens so often it drives me crazy.


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## I800C0LLECT (Jan 26, 2009)

Maybe I can shed some light since I'm in a similar situation...

I will be using a 6.5" sub. My wife wants me to limit/remove any footprint from installing an audio system because she wants to keep as much room as possible for our family.

In my opinion, the correct use for a 6.5" sub is for limited space considerations. I don't plan on going below 40hz either. So I'm trading off "low end" for more efficiency elsewhere. I honestly can't figure out how to build anything that I can hide in the passenger footwell or under the dash that ISN'T a ported enclosure or MATCHES a ported enclosure output.

I think this is exactly what Patrick is trying to say. Why waste all of this hard work trying to fit a horn in/under my dash when all I have to do is a simple ported and tuned enclosure? He's right.

Maybe it's neat...maybe it isn't a horn...maybe it "sounds" exactly like what the Op was hoping for but it does not contradict the truth in any way shape or form. That's all Patrick has presented.

I haven't built anything yet...but all of the modeling I've done thus far, the ported enclosure is most efficient and I'm only utilizing .3 cubic feet + speaker displacement.

I can imagein that the op's tire well has much more space than what I'm hoping to use and he could therefore get a much better response if he just sticks to the old school rule that displacement is king.

I don't even want to mention how much output is lost by placing in the trunk. That's why I commented earlier that 6.5" sub in the trunk doesn't seem like a great idea.

I was really hoping to see a crafty placement of a 6.5" sub up front.


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## thehatedguy (May 4, 2007)

So I am supposed to tell my children to go a head and stick their fingers in light sockets so they'll know what I know...or I should tell them before hand it's a bad idea and let them skip the pain and agony?


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## Hoye0017 (Mar 23, 2010)

thehatedguy said:


> So I am supposed to tell my children to go a head and stick their fingers in light sockets so they'll know what I know...or I should tell them before hand it's a bad idea and let them skip the pain and agony?


That is the worst analogy ever. Please don't compare us to children. And don't compare failing at a subwoofer box to a potentially fatal accident. The OP was fully aware of the minor risk he was taking in time and expense before he did it. 

Some suggestions were helpful. Some are just someone trying to say that they know better and really brought nothing constructive to the conversation.


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## thehatedguy (May 4, 2007)

Lighten the hell up.


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## bassfromspace (Jun 28, 2016)

This has turned into a comedy.


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## chithead (Mar 19, 2008)

thehatedguy said:


> Lighten the hell up.


Is this another finger in the light socket reference?


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## thehatedguy (May 4, 2007)

Something like that.


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## Hoye0017 (Mar 23, 2010)

chithead said:


> Is this another finger in the light socket reference?


Ha! Good one. That's comedy right there.


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## pauldurkin_trail (Apr 10, 2013)

Boy, this thread is ruffling a few more feathers than I had figured.

What is also interesting is that I figured out exactly what patrick is talking about over 20 years ago. If you want lots of bass, a big speaker will do it. Simple.

At that time, I built two sealed 12's, with a 100w amp, running off a tape deck (Car audio CD players were JUST available...if you had huge bucks), and pounded the rust off my VW bug wherever I parked.
From there, i went through ported 12's, a variety of sealed 10's, bandpass 15" (moaning and groaning garbage that would only fit a stationwagon) from plans Orion used to publish, different push/pull configurations, etc, etc. 

I also fiddled with some early attempts at front soundstage and imaging configurations, some of which worked extremely well, some kinda ****ty. Computer modeling was non-existant, and most things were a "cut and try" situation.

*I also realized that "loud" was pretty easy to do. Big speaker(s)+wattage=BASS.*

During that time, the idea of transmission line style enclosures was being fiddled with by some home audio fanatics, some with success, but one in a car might as well have been a unicorn. I loved the concept, but so little was known that it was like alchemy. I was massively intrigued, and still am!

Somewhere around then, I listened to a set of KEF uniQ reference home audio speakers, and fell in LOOOOOOOOVE. I sold all my car audio stuff, scraped together every cent I had, borrowed, begged and starved, and bought them.

I still listen to that same pair of speakers almost every night. 
Absolutely my favorite sounding home speaker to this day. Just tight, lively, musical, detailed, and responsive.
BUT.....NOT a "Rockin house party" sort of speaker. More of a "sit and listen closely" speaker.

To me, large diameter woofers in a car mainly sound like someone clubbing a seal to death. Yes, they make BASS. Cant argue there.
But compared to my "reference" at home, as crude as a cavemen's club in most cases.

Which, brings me back around to my unusual choice in this enclosure. The TL has held a certain "mystique" with me from long ago.
(Just like the Supra did when I first saw it in road and track back in 1993/4, and guess what, it STILL turns me on all these years later when i can finally afford one!)
Also, I love the sound of good small drivers. Tight, responsive, detailed. Beautiful.
BUT, getting the low bass output up to a nice listening level in a car is a challenge. 

Sealed wont do it with 6.5" drivers.
Ported, perhaps, but at the possible sacrifice of getting "farty" sounding.
A horn is just damn big to get any reasonably low tuning in the space I am willing to work with, not to mention peaky.
So, thats where the TL seems to be the logical choice *FOR ME*, in this application.
Not to mention kinda cool, challenging, and unique....... Has anyone on here seen another "spare tire well" transmission line done??


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## Hoye0017 (Mar 23, 2010)

Which KEF speakers do you have? We had a set of 207's in the showroom at a place I used to work. Great build quality and a sound that I would call extremely neutral. which isn't really my cup of tea. Most people loved them though. I actually preferred the XQ series.


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## Oscar (Jun 20, 2010)

ok so you like it....when are we going to see measurement plots, graphs, numbers, etc, etc...stuff to for us (who can't hear it and won't ever hear it) to have something to go by when you say it was a "success"??  And please don't feed us the "I have nothing to prove to anyone, so long as I like it..." kinda speech...please....lol.


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## pauldurkin_trail (Apr 10, 2013)

Oscar said:


> ok so you like it....when are we going to see measurement plots, graphs, numbers, etc, etc...stuff to for us (who can't hear it and won't ever hear it) to have something to go by when you say it was a "success"??  And please don't feed us the "I have nothing to prove to anyone, so long as I like it..." kinda speech...please....lol.


Well, I guess when I go ahead and buy an RTA setup of some sort. I'm interested enough in providing data to spend a couple of bucks, and have heard that stuff has come WAYYYYYYYY down in price since 1990!
Of course, this wouldn't be something I will be likely to use too often, so lets not get crazy.
Any suggestions? (oh god!)


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## pauldurkin_trail (Apr 10, 2013)

Oh - 1800collect: I'm not sure if you realise this, but a supra is a hatchback.
That's another reason I felt this design had some merit in this application.

MkIV Supras have an extremely long nose, a good cockpit for two (technically rear seats.....for a midget with amputated legs, and no need for any head support), and a shallow, high hatch, with a very sloped rear window. The two woofers aren't actually that far away in distance, and at a similar elevation to your shoulders when seated.
One of the things I was hoping to take full advantage of (and feel I did) was the shape of the hatch above my two little woofers.
If this was a car that had a "real" trunk, this enclosure and woofer choice would have been an absolute, total failure.

Heres a pic of my car, so you can get the idea of the layout.


Your seated position is very close to the tiny quarter windows behind the doors, and the woofers are pretty much lied up 3/4 of the way back on the rear wheel arch. The terminus lines up with where the wing attachment point is.

I can reach back and come within 3 inches of touching the front woofer, if I try hard ( I'm about 6 feet tall, however).

If you look at the overall shape of a MKIV supra, from the hatch area to where you are seated, its shaped.....like a giant, smoothly curved, horn!
I guess we all know what horns tend to do.....increase output!

Anyhow, thought you guys might enjoy the picture, and since these cars aren't seen too awful much "out and about", get a better idea of the layout of this car, and get another little insight into how my little brain figured this enclosure might be worth the experimental time and "risk".


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## I800C0LLECT (Jan 26, 2009)

Now that changes everything!! I remember supra's but I honestly didn't remember their layout. I'd like to buy a new car just to get a hatch back  Probably a Golf TDI.

In my grand prix I had a hard time using the trunk the way I had hoped. My DIYMA R12 was my favorite but with the cold temps in Idaho(don't live there now) I ended up having to take long drives to warm everything up before I could really play anything loud.

Personally, I still think I would have gone with a bigger sealed woofer. Mostly because I wouldn't want to give up any low end. I've seen people fit a LOT inside those spare tire wells. Simplicityinsound is a huge fan of using that space in his installs with false floors. You should check out his stuff.

But we're all about playing with our speakers around here. Maybe you'll get the itch to try something different? 

I still believe the mid is the most important part of the install in a two-way so I kind of shrug at most sub installs. Hopefully when I get home from deployment I'll have time to play with my purchases :>

But thanks for doing something different. Take it easy on Patrick too. He loves to play but he's very dry and his tone doesn't carry well. As much as it seems he's been negative I think he was just trying to be certain you knew what you were giving up with respect to install and low end output.


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## Brian Steele (Jun 1, 2007)

pauldurkin_trail said:


> Well, I guess when I go ahead and buy an RTA setup of some sort. I'm interested enough in providing data to spend a couple of bucks, and have heard that stuff has come WAYYYYYYYY down in price since 1990!
> Of course, this wouldn't be something I will be likely to use too often, so lets not get crazy.
> Any suggestions? (oh god!)


Got a laptop?
Room EQ Wizard is free
So is HolmImpulse

You'll need to get a decent mic though, for basic measurements, and an external sound card for more accurate results. Check Parts Express for their calibrated mics.


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## 94VG30DE (Nov 28, 2007)

Brian Steele said:


> Got a laptop?
> Room EQ Wizard is free
> So is HolmImpulse
> 
> You'll need to get a decent mic though, for basic measurements, and an external sound card for more accurate results. Check Parts Express for their calibrated mics.


Also MiniDSP has one that is already set up for REW: UMIK-1 | miniDSP 

OP, glad you like the KEF Uni-Q. Great concept and fanstastic execution, it's been talked about a fair amount on here and a lot on diyAudio I think. 

I think your comments about large woofers sounding slow and smaller woofers sounding tight and ported enclosures sounding farty is the same tired dogma that we keep debunking. 

You gotta remember, sub bass is about moving air, and you can either have two 6.5" woofers moving at 'x' excursion, or one 15" woofer moving at 0.38(x) excursion (if I did my envelope calc correctly). Which do you think is going to sound better?

Here is a really good read that discusses some of these things. You might not like the OP though  http://www.diymobileaudio.com/forum...audio-discussion/144040-bass-race-2013-a.html


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## EmptyKim (Jun 17, 2010)

pauldurkin_trail said:


> Any suggestions? (oh god!)


Virtual Audition?

DIYMA Virtual Audition Forum - DIYMA Car Audio Forum


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## xrk971 (Jul 11, 2013)

Paul,
Fantastic job there with the dual driver TL! I am glad you did not let the naysayers dissuade you. I am not sure why folks kept pushing a 12 in driver in a sealed cabinet. You simply don't have the space for it. A TL or other type of waveguide cabinet will always have more specific efficiency of bass output than a sealed cabinet. You have great fiberglass building skills there. I have built several of the Cornu spiral horns and other TL type designs. I am pretty handy with modeling most speaker cabinets in AkAbak and if you can provide dimensions of your cabinet as built and driver TS params, I will throw a model together. One thing to consider to get deeper bass extension - easy with your relatively high Qts drivers is too constrict the terminus to make it a mass loaded TL. You can get usually 10 to 15 Hz extra deep bass extension at slight drop in SPL efficiency. This can all be modeled and simulated of course. You an also play with constricting the exit with plywood and duct tape to gradually see the effect. Since you have a tiny space in a car, a slight drop in efficiency is probably a worthwhile trade off for deeper bass. 
Nice job! Congratulations. 
X


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## xrk971 (Jul 11, 2013)

pauldurkin_trail said:


> Well, I guess when I go ahead and buy an RTA setup of some sort. I'm interested enough in providing data to spend a couple of bucks, and have heard that stuff has come WAYYYYYYYY down in price since 1990!
> Of course, this wouldn't be something I will be likely to use too often, so lets not get crazy.
> Any suggestions? (oh god!)


Buy a $2 Panasonic wm61a mic capsule (flat as a board response from 10 hz to 20 khz). Wire it to a 3.5 mm jack from old discarded headphone. Download Holmimpulse software (free). You now have a very capable system for almost free. You need a pc (laptop in your case since outdoors in car) with sound card input.


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## mojozoom (Feb 11, 2012)

Or if you aren't soldering iron inclined, buy an old Denon Audessey mic and use it with Holm or REW. Same as above but less DIY, but more $$. Still less than $20 though.


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