T-Line for ED8 Home Theater is it right?

[JLJunkieMX107 10+ year member]

I made up a design for an ED8 i am using for a home theater setup. I forgot the paper I wrote the design on at work so i will try to go from memory. Here are the specs that I recall. Port is 10" x 5". Box dimensions are 41.5" height x 11.5" width x 11.5" depth. The port is aprx. 82 inches long. I was shooting for 41hz.

Just looking to add a little bass to my home theater and get some practice on the t-line. So what do you think?

If it isnt right could you steer me in the right direction. I am not experience in T-Lines and am trying to learn. Thanks.

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[Immacomputer 10+ year member]

http://www.quarter-wave.com

Read some of the papers there before attempting to design a transmission line enclosure.

If you want some extra bass for a home theater or music system, I would suggest putting that in about 2-3 cubes tuned around 20-25hz with about 15in^2 of port.

 

[JLJunkieMX107 10+ year member]

Alright. Imma, what formula do you use to design a t-line?

 

[Immacomputer 10+ year member]

Well, you have to take a bunch of things (and parameters) into consideration. You first need to decide whether or not to taper. For sub enclosures, there is really no need to taper the line so I would go with 1. From there you need to calculate your driver's resonant frequency given the amount of air you're going to use. This is tricky as you need the point of resonance to find the line length and the line length (along with the cross sectional area) to find the point of resonance. At this point, you can assume something close to the free-air resonance of the sub. Now, you need to check out the alignment tables from the Alignment Table PDF in the link above. Find Dz and Dr for your specific driver and calculate the recommended cross sectional area for the line (this will probably not be equal to Sd like many people say to do). From there, you can also get the effective line length for the enclosure. At that point, calculate the volume of air in the transmission line and model the sub with a sealed enclosure of that size. From there, you can get the point of resonance. If it is close to the 1/4 wave line length you chose, you can move on. If it is off by a decent margin, start over using this resonance point and find your Dz and effective length and then make a new line and then check everything after that to make sure your resonance points are correct.

Stuffing can help get the line spot on and driver offset can also affect the sound and output.

If you're serious about it, read the entire articles posted on that website and don't skip over the parts with the math in them.

 

[JLJunkieMX107 10+ year member]

Thanks man, that was a HUGE help. I always thought it was as easy as 1127/ fs /4 = line length but now I know otherwise.

+1 for Immacomputer

 

[BrianChia 10+ year member]

A bass reflex box would probably bette for home theater.

 

[JLJunkieMX107 10+ year member]

Alright so I will be better off going with a ported box and not trying to mess with a t-line

 

[PV Audio 5,000+ posts]

Alright so I will be better off going with a ported box and not trying to mess with a t-line

Not with that driver, no.

 

[JLJunkieMX107 10+ year member]

Well im gonna take a crack at it. I guess the best way to learn is trial and error. Thanks for the advice guys.

 

[Immacomputer 10+ year member]

Not with that driver, no.

I had pretty nice results with a bass reflex for those exact subs. I was able to get them to easily play down to 23hz at the -6dB point and that's in a room with not much boost below 30hz. In the actual theater room, they easily played down to 20hz and were very smooth from 20hz to 100hz where they were crossed at. They also handled a Dayton 240wrms amp on the pair with no problem. I really doubt the FR would be extended or the sound quality be improved much with a T-line.

 

[JLJunkieMX107 10+ year member]

Alright I just went with a 3 cube bass reflex enclosure. Tuned to 20 hz with 16 in^2 of port. Im throwing a flare port on it just so it looks pretty lol. Thanks again.

 

[PV Audio 5,000+ posts]

I had pretty nice results with a bass reflex for those exact subs. I was able to get them to easily play down to 23hz at the -6dB point and that's in a room with not much boost below 30hz. In the actual theater room, they easily played down to 20hz and were very smooth from 20hz to 100hz where they were crossed at. They also handled a Dayton 240wrms amp on the pair with no problem. I really doubt the FR would be extended or the sound quality be improved much with a T-line.

I was saying no to the T-line //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

 

[Immacomputer 10+ year member]

Alright I just went with a 3 cube bass reflex enclosure. Tuned to 20 hz with 16 in^2 of port. Im throwing a flare port on it just so it looks pretty lol. Thanks again.

I think that's a good call. It's a very laid back sounding sub in an alignment like that but it really melts away in a corner and disappears. It's not aggressive at all or punchy but the response is very nice and smooth.

I was saying no to the T-line //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

Oh ok, re-read his post though and you'll see why I got confused.

 

[JLJunkieMX107 10+ year member]

Awesome, its going in a 12' x 13' room so it should add plenty to my lows. I am starting the build tonight!