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?

 

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.

 

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.

 

Holy shit, welcome to last year!

 

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

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

 

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

 

Holy shit, welcome back to the forum

 

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