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Quarter Wave / T-Line tutorial-UPDATED


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NO

You buld the box to the frequency you choose. Ported volume has (almost) nothing to do with the build, other than indicating a "tighter" t-line may be more advantageous...

MickyMcD - "Capable of making some serious trouser flapping volumes at where's-my-testicles frequencies, the Servo-Drives used to be fairly jaw dropping..."

Any time you have have a power wire next to your frame put some rubber hosing (or cut up an innertube) around it. The wire is bound to wiggle (due to driving or flex) and the casing will eventually wear through.

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Would the box need to be to the reccomended ported size? like 2 15's need about 10 cubes so you would just start with the 10cube box and figure in the port frequency/ total cone area of the 2 woofers?

Start on page 1 of this thread......it explains everything :)

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Can someone please help me understand what happens when you try to hit a note that is 4 times the tuning frequency?

E.g. Take a port length of 2.833 meters (9.296 ft.). This gives a quarter wave tuning frequency of 30 hz. This means that at 30 hz, the wave coming out of the port will be 90 degrees out of phase from the front of the sub. At 60 hz, the signal out of the port will be 180 degrees out of phase from the front of the sub. At this frequency the two waves fully complement each other and the enclosure is loudest. Finally, after 270 degrees, or 90 hz, the port stops complementing the sub, the interference becomes destructive. At 120 hz, all the port energy completely cancels out the subwoofer's energy.

If the above calculation's are indeed correct and applicable to the T-line enclosure then the optimum frequency range will be between 90 and 270 degrees of phase shift. To calculate this you take the speed of sound (340 m/s (1115 ft/s) and divide it by the length of your port (2.833 meters (9.296 ft.). Multiplying this value by 0.25 will give you the 90 degree frequency value, and multiplying it by 0.75 will give you your 270 degree frequency value... (30hz - 90hz).

I am curious as to what happens to the sound quality of your T-line when your subwoofer extends beyond it's 270 degree phase shift, all the way back to a full 360 degree shift at e.g 120hz.

Please answer, as I am building A subwoofer enclosure for my room and was really hell-bent on a T-line until I did some calculations.

Sincerely, Cap Woodgate

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I think you are overthinking this. Its for a subwoofer, right? Why are you concerned with anything over 80 Hz? Also, it puts the rear wave in phase with the front.

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I think you are overthinking this. Its for a subwoofer, right? Why are you concerned with anything over 80 Hz? Also, it puts the rear wave in phase with the front.

Well for lower tunings such as 20 hz (which I have the space for) the rear wave's shift by 360 degrees at 60 hz. I want to know If my T-Line will still perform well after that 270 degree point. After all, I would want a frequency response of about 25hz-120hz.

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I was curious how you guys handle these boxes if the subs mounting depth is larger than your line width ... Like I was thinkin of building one for a 10" woofer but the depth is about 7.5" rounded it up to 8" but need my line width to be around 5.5" wide and 11" tall ... So how would you handle that ? Space the sub out or what ?

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I was curious how you guys handle these boxes if the subs mounting depth is larger than your line width ... Like I was thinkin of building one for a 10" woofer but the depth is about 7.5" rounded it up to 8" but need my line width to be around 5.5" wide and 11" tall ... So how would you handle that ? Space the sub out or what ?

3/4 mdf rings..space the sub out. Or inverted.

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Do you have any T line designs for 2 12" SA's, I think fs is like 28-29. Max dimensions 40" W, 30" D, 18" T... Or do you think itd be possible with that amount of space. Id rather pay a little for a design than try to wrap my head around this concept in a short amount of time

Rebuild in progress...

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I was curious how you guys handle these boxes if the subs mounting depth is larger than your line width ... Like I was thinkin of building one for a 10" woofer but the depth is about 7.5" rounded it up to 8" but need my line width to be around 5.5" wide and 11" tall ... So how would you handle that ? Space the sub out or what ?

what Chris Hammer said... or

use a double baffle where you mount the subs.

if the subs mounting depth is 6.50 inches and the line itself is 6 inches, then add another baffle to where you mount the sub. Your subs mounting depth just changed to 5.75 inches. :)......hope this helps !

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I was curious how you guys handle these boxes if the subs mounting depth is larger than your line width ... Like I was thinkin of building one for a 10" woofer but the depth is about 7.5" rounded it up to 8" but need my line width to be around 5.5" wide and 11" tall ... So how would you handle that ? Space the sub out or what ?

Depends where you place the t-line and the sub and port. If they are next to each other then you risk cancellation. If they are separated and/or one of them is downfiring/upfiring/corner loaded then you'll probably receive some below tuning extension.

MickyMcD - "Capable of making some serious trouser flapping volumes at where's-my-testicles frequencies, the Servo-Drives used to be fairly jaw dropping..."

Any time you have have a power wire next to your frame put some rubber hosing (or cut up an innertube) around it. The wire is bound to wiggle (due to driving or flex) and the casing will eventually wear through.

Hammerdown... 1%

no links to outside websites, business related FB/YT pages allowed.

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