8" quarter wave (transmission line) box

[TJElite]

I just built one for a Treo SSi 8. Well, the woofer isn't here yet, so I threw a simple Crossfire DB38 in it. On 300 ish watts (back half of Sundown 4x100) its whopping 8mm of xmax belted out 133db on music. This was with the box just sitting in the very back of the Escalade, no tuning, brand new woofer, very conservative gain setting. And it has a very nice, full, natural sound, as a Tline should.

I'm really looking forward to putting the SSi in there, with its 500w rms power handling, and 26mm of xmax.

I also got around to testing that big folded horn box I built. 2 10's on about 800 watts did 139.9 db. Again on music, in the back of the escalade, no tuning.

Toby

[Notladstyle]

any links on specs to that type of box? never tried anything like that.

[the727kid]

I jsut got my 100.4 today....and all I can say is wow. I'm amazed at how well it performs, it's gunna be real nasty when I bridge it.

[the727kid]

BTW do you have an o-scope Toby? I'm not bridging these until I can use one.

[TJElite]

any links on specs to that type of box? never tried anything like that.


The transmission line? Simplest box you've ever designed.

Take speed of sound in air (I use 1130 fps) divided by Fs of woofer...that gives you wavelength. Now, divide by 4, giving you 1/4 wavelength. This is how long the Tline has to be. In my case, it was 8.8'.

Now, take the Sd of the woofer. This is the area of the Tline. I used 37.5 sq in.

That's it. Imagine the woofer in one end of a 5 sided 'port' 37.5 inches in cross section and 8.8 feet long. That is a 1/4 wave box for an 8" woofer with an fs of 32hz.

Now, the fun part is folding that up to fit in the car. My enclosure ended up being 31.5 long x 9 wide x 18 tall...not exactly compact, especially for an 8. The box sits on one side of the cargo area, and both the 8 and the other end of the line fire up.

I didn't get any pics before my wife drove off with it. I'll take a couple tomorrow.

Toby

[TJElite]

BTW do you have an o-scope Toby? I'm not bridging these until I can use one.


No, no scope. Just curious...why do you need a scope to bridge the amp?

Toby

[the727kid]

Don't NEED it. But I have to be very careful putting that much power to those speakers.

[TBSpyder]

Yo Toby dawg, I bet you could like totally stomp a 13w7 with that mad tyte setup. You'll prolly be bangin' out like 180dbs or some skit, right yo? ;) :wiggle:

[Notladstyle]

Yo Toby dawg, I bet you could like totally stomp a 13w7 with that mad tyte setup. You'll prolly be bangin' out like 180dbs or some skit, right yo? ;) :wiggle:





:werd:.. ....and a few posts later:ibtl:

[TJElite]

Yo Toby dawg, I bet you could like totally stomp a 13w7 with that mad tyte setup. You'll prolly be bangin' out like 180dbs or some skit, right yo? ;) :wiggle:

Nah Dawg, I iz-aint wastin this mack daddy gat on yo 13w7. Tha shizzle is wiz-eak. I gots a stack sayin my foe inch Vifa in a trip tuned alphapbet closure wud cold smi-zak a duece of w7's, biatch.

[POST]

Nah Dawg, I iz-aint wastin this mack daddy gat on yo 13w7. Tha shizzle is wiz-eak. I gots a stack sayin my foe inch Vifa in a trip tuned alphapbet closure wud cold smi-zak a duece of w7's, biatch.


I HAD to log in from work................ROFLLMAO!!!!!:lol: :lol: :lol: :lol:


funniest shit i've ever seen Toby post.

[Notladstyle]

Nah Dawg, I iz-aint wastin this mack daddy gat on yo 13w7. Tha shizzle is wiz-eak. I gots a stack sayin my foe inch Vifa in a trip tuned alphapbet closure wud cold smi-zak a duece of w7's, biatch.


Toby gangsta speak > AHQ

[TBSpyder]

:lol: :lol:

[Skee]

post pics of the 8 Tline i wanna see it

you can tune the box to the amp to shortin your tline still getting that 20-60 hz clean bass range

[kpr10is]

Don't NEED it. But I have to be very careful putting that much power to those speakers.

Personally Id bi-amp em if you're staying passive. Those Germ crossovers are sweet for that. You hardly need an o-scope. Theyll love the power, and youll love the midbass response you're about to get out of em.

[the727kid]

I'm too lazy to bi-amp them. But I can't take the slighest risk of clipping them at that high of power.

[kpr10is]

Uhhh...biamping them is the exact same amount of work as what you are already doing. You do know what I mean by biamping right? aka 2 channels of output unbridged from the amp going to each crossover, like the Germ crossovers so nicely accept. Like I said...you wont clip them. Add some deadening if you dont have it already and youll be set. The set I biamped was off a Kicker 350.4 in fully deadened doors. Played with em without a HPF for a bit, those mids get down to say the least.

[the727kid]

I know what it is, and don't really want to run the wires across the whole car again. If I ever decided to biamp I would actually go Active instead. But my Raammat and Ensolite should be here today to deaden the doors.

[jseville88]

i'm having some trouble understanding how this enclosure actually works.For whatever reason it doesn't make sense to me.If your enclosure is 31.5x9x18 that's only about 2.20 ft3 if your line or port is 37.5 sq inches and 106 inches long then the displacement of the port would be greater than the amount of space actually in the enclosure.

[TJElite]

The enclosure is just a big port...think of it as a long pipe, with a speaker in one end. So actually, the port displacement equals the box displacement plus or minus some bracing.

Toby

[jseville88]

so when building a t-line enclosure you dont have to calculate for space that the woofer needs you just build it to the size of the line and thats it?

[Skee]

ya thats about it port area/ length and drop some 45 degree angle it will give ya another 1.5db or so nothing noticeable unless you have a meter.

[Notladstyle]

i'm having some trouble understanding how this enclosure actually works.For whatever reason it doesn't make sense to me.If your enclosure is 31.5x9x18 that's only about 2.20 ft3 if your line or port is 37.5 sq inches and 106 inches long then the displacement of the port would be greater than the amount of space actually in the enclosure.

From what I understand, the point is to bring the backwave of the output from the subwoofer into sync with the front wave(so that the net output is positive and both negative at the same times).

In order to achieve that, the port is the exact length that sound at the fs frequency of the subwoofer would travel in one cycle of the subwoofer. The area of the port has to be the same area displaced by the subwoofer because friction will slow air and and put the back wave out of sync.

I guess =/ Sounds very inefficient because it only works at the fs.

[TBSpyder]

Holy shit, welcome to last year!

[TJElite]

From what I understand, the point is to bring the backwave of the output from the subwoofer into sync with the front wave(so that the net output is positive and both negative at the same times).

In order to achieve that, the port is the exact length that sound at the fs frequency of the subwoofer would travel in one cycle of the subwoofer. The area of the port has to be the same area displaced by the subwoofer because friction will slow air and and put the back wave out of sync.

I guess =/ Sounds very inefficient because it only works at the fs.

Basically correct. The length is actually 1/4 of the wavelength at Fs. I'm pretty sure it could also be other multiples, but length would be prohibitive.

It is not ineffcient, however. While it is tuned at Fs, it is like any other port, in that it 'hangs over' each end...i.e., the Fs is the top of the hump, but there is still improved output on each side. Typically, it will cover one octave up, and one down. Similar to a ported box tuned to Fs.

And, just like any other ported box, the woofer still plays all the frequencies that it is given...it doesn't magically shut off...output is just maximized at Fs. They are not only very efficient , but they are extremely accurate as well. Some say it is the ultimate setup for sq.

Per my original post, we got 133 db on a simple 8, with about 300 watts, on music. Later, in the same enclosure, we got to about 137 with a treo 8 on 500 watts. Some of you heard it at the last meet...I don't think inefficient is a good descriptor :D

I have a bandpass Tline (you do this when the Qts of the woofer is a little high for straight Tline) as a center console in my Ultimate Tailgating Suburban, if any of you want to hear it at the meet Saturday. That's also the vehicle that has the tactile transducers in it.

Toby

[TJElite]

Holy shit, welcome to last year!


Yeah, but at least it was an intellegent excavation, instead of something like

'I got a 8 4 sale it slams ht me up'

Toby

[Notladstyle]

Holy shit, welcome to last year!

Holy shit, welcome back to the forum

[Notladstyle]

Basically correct. The length is actually 1/4 of the wavelength at Fs. I'm pretty sure it could also be other multiples, but length would be prohibitive.

It is not ineffcient, however. While it is tuned at Fs, it is like any other port, in that it 'hangs over' each end...i.e., the Fs is the top of the hump, but there is still improved output on each side. Typically, it will cover one octave up, and one down. Similar to a ported box tuned to Fs.

And, just like any other ported box, the woofer still plays all the frequencies that it is given...it doesn't magically shut off...output is just maximized at Fs. They are not only very efficient , but they are extremely accurate as well. Some say it is the ultimate setup for sq.

Per my original post, we got 133 db on a simple 8, with about 300 watts, on music. Later, in the same enclosure, we got to about 137 with a treo 8 on 500 watts. Some of you heard it at the last meet...I don't think inefficient is a good descriptor :D

I have a bandpass Tline (you do this when the Qts of the woofer is a little high for straight Tline) as a center console in my Ultimate Tailgating Suburban, if any of you want to hear it at the meet Saturday. That's also the vehicle that has the tactile transducers in it.

Toby

Efficient at the tuning freq, but what would a 30-200hz graph look like?

... Wait, cant your meter produce such a graph?

[TJElite]

Efficient at the tuning freq, but what would a 30-200hz graph look like?

... Wait, cant your meter produce such a graph?

I'd have to guess that it would look like a ported box, tuned to the Fs. Probably a large ported box.

Actually, it would probably look more like the woofer response curve, with a hump at FS. Like I said, this is not some sort of bandpass, that filters the response.

Since I typically don't run subs above 63hz (sometimes not above 50), I don't care what it would look like up to 200. If I use a woofer with Fs of 30, I can expect peak response to be from 15 to 60, which is about perfect in a car.

I don't know well Termpro would actually graph. It does have the little bar graph below the SPL, which will show where the peak SPL occured. I guess if we fed the woofer pink noise, it would draw some sort of graph. If not, I also have an RTA package that definitely would.

Unfortunately, the only Tline I currently have is in a convertible (more like a converted, since it has no top) Suburban...not the best for accurate readings.

Toby