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Forevrbumpn

Quarter Wave / T-Line tutorial-UPDATED

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I've got an 8" sub that's about 6.5" diameter (halfway on the surround on each side) so...

3.25x3.25x3.14= 33.2137 Port Area

FS of 46 so 1130/46= 24.6521

24.6521/4= 6.141304

6.141304 x 12 to go to inches = 73.695648 port length

How would I tweak this for 3 Subs? I'm assuming I would increase my port area for each sub like 33.2137x3 and get the port area needed but keep the port length the same? Any advice appreciated in advance!

BTW GBW801 subs.... going to do a 3x3 config of them

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if a sub is rated for 1000 watts rms and 2000 peak , if a t line makes it so this sub can only play 400rms safely what happens peak?   also can the t line play at the 1k rms?

 

 

can someone clear this up for me, i am clearly  confused

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5 hours ago, JohnDoeVolvo said:

if a sub is rated for 1000 watts rms and 2000 peak , if a t line makes it so this sub can only play 400rms safely what happens peak?   also can the t line play at the 1k rms?

 

 

can someone clear this up for me, i am clearly  confused

There is a bit of a complicated answer to this.  Subs have two limitations on how much power they can take, there is the mechanical limit of how far the cone/coil can travel before bad things happen, and then there is the thermal limit of how much heat the coil can dissipate before stuff starts to overhead and come apart.   Both of these limits are impacted significantly by the type & specs of the enclosure and the type of sound being played.  The mechanical limit is more cut and dry, a sub can handle X number of watts at Y frequency before there is mechanical damage.  The thermal limit is a bit harder to nail down.  A sub can hand X watts at Y frequency continuously for Z amount of time.   Notice I said "continuously".  This is related to what the RMS rating is.  Most subs can handle brief periods of MUCH more power, as long as its for a short amount of time and the sub is given a chance to cool back down, and as long as it doesn't exceed the mechanical limits.  For example, when playing a ported box around the tuning frequency, there is tons of cone control and it will be extremely difficult to ever exceed its mechanical limits, however cooling isn't as good and impedance is low so there is lots of heat going into the coil.  This is a situation where you could give a QUALITY sub 2-3 times its RMS rating, as long as it was quick.  

Now, here is how all that applies to T-lines.  The way most people build t-lines these days results in a very oversized enclosure, IMHO.  This reduces the mechanical power handling of the sub significantly.   If the T-line reduces the mechanical power handling of a 1000 watt sub down to 400 watts, that's its.  If you play more than 400 watts and the wrong frequency, say goodbye to your sub.  You sub may still have tons of thermal capacity left, but its doesn't matter, in this situation mechanical power handling is the weakest link in the chain.  

The proper way to determine how your sub will do in a T-line is to model that T-line in simulation software such as HornResp.  Then you will know just what you can get away with.  

Edited by Triticum Agricolam
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"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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I bought a pair of 3 inch full range Daytons to make a soundbar for the living room with, but as im reading, I'd kinda like to try my hand at a T-line...

Do you think these -

https://www.parts-express.com/dayton-audio-pc83-4-3-full-range-poly-cone-driver--295-154

- paired up with a tweeter and a woofer will work in the same enclosure or should I stick to the soundbar with these and make a dedicated woofer for the T line instead?

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9 hours ago, Triticum Agricolam said:

There is a bit of a complicated answer to this.  Subs have two limitations on how much power they can take, there is the mechanical limit of how far the cone/coil can travel before bad things happen, and then there is the thermal limit of how much heat the coil can dissipate before stuff starts to overhead and come apart.   Both of these limits are impacted significantly by the type & specs of the enclosure and the type of sound being played.  The mechanical limit is more cut and dry, a sub can handle X number of watts at Y frequency before there is mechanical damage.  The thermal limit is a bit harder to nail down.  A sub can hand X watts at Y frequency continuously for Z amount of time.   Notice I said "continuously".  This is related to what the RMS rating is.  Most subs can handle brief periods of MUCH more power, as long as its for a short amount of time and the sub is given a chance to cool back down, and as long as it doesn't exceed the mechanical limits.  For example, when playing a ported box around the tuning frequency, there is tons of cone control and it will be extremely difficult to ever exceed its mechanical limits, however cooling isn't as good and impedance is low so there is lots of heat going into the coil.  This is a situation where you could give a QUALITY sub 2-3 times its RMS rating, as long as it was quick.  

Now, here is how all that applies to T-lines.  The way most people build t-lines these days results in a very oversized enclosure, IMHO.  This reduces the mechanical power handling of the sub significantly.   If the T-line reduces the mechanical power handling of a 1000 watt sub down to 400 watts, that's its.  If you play more than 400 watts and the wrong frequency, say goodbye to your sub.  You sub may still have tons of thermal capacity left, but its doesn't matter, in this situation mechanical power handling is the weakest link in the chain.  

The proper way to determine how your sub will do in a T-line is to model that T-line in simulation software such as HornResp.  Then you will know just what you can get away with.  

 

 

ok so basically i can buy a smaller amp based off of what software tells me.  seems like this is the best for people who dont compete considering the weight saving and cost .

 

im looking for anything above 130db for my small 2012 camry was thinking about doing quad 8's infinite baffle but now maybe ill do 1 twelve or maybe even one 8in sub...

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On 1/21/2018 at 7:48 PM, dbmode2 said:

I AM THE ONLY ONE WITH NOT 1 2 3 BUT 6 8'S IN A 1/4 WAVE T-LINE SUB TUNE AT 31HZ'S  IN A 4 DOOR SMALL SEDAN  MY OPINION T-LINE SUB BOX IS THE CHEATER SUB BOXES OF OUR GENERATION......

can you elaborate a little more on the details? subs, amps car, etc..

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On 11/20/2006 at 8:47 PM, Forevrbumpn said:

, you measure the cone, by useing a tape measure, and measure from middle of surround, to middle of surround on opposite side) 10" is usually close to 9"- 8.5"-9". This is where Pie comes in  9"/2 = 4.5-------- 4.5"x 4.5"x 3.14" = 63.58sq"

That is your Port AREA ( usually round this number Down- say 60sq")

 

also can someone take a picture of this process?  this is just the diameter of the come correct?

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9 hours ago, JohnDoeVolvo said:

also can someone take a picture of this process?  this is just the diameter of the come correct?

Yup, its just the diameter of the cone, measured from the middle of the surround on one side to the middle of the surround on the other.

For most subs you don't even have to bust out the tape measure since most manufacturers tell you what the cone area of the sub is.  Its called "Sd" and its given in square centimeters, divide that number by 6.4516 to get square inches. 


"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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18 hours ago, Epic said:

I bought a pair of 3 inch full range Daytons to make a soundbar for the living room with, but as im reading, I'd kinda like to try my hand at a T-line...

Do you think these -

https://www.parts-express.com/dayton-audio-pc83-4-3-full-range-poly-cone-driver--295-154

- paired up with a tweeter and a woofer will work in the same enclosure or should I stick to the soundbar with these and make a dedicated woofer for the T line instead?

I haven't used those particular drivers, but you shouldn't need a tweeter with them.  They are designed to be full range.  You will probably want a sub.  If you are going to use a sub there isn't much reason to put the Daytons in a T-line.  You can do a T-line sub then if you want. 


"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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