long-thin vs fat-short TL - diyAudio
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Old 10th October 2006, 09:50 PM   #1
Henkjan is offline Henkjan  Netherlands
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Default long-thin vs fat-short TL

I am designing a sub with 2 6" TB drivers for a coworker, and am sort of on a crossroad which design, a TL with a long line but narrower (2.4m 1.4-0.6 Sd) or a shorter line with larger xsection (1.65m 3-1Sd). below some graphs from the driver offset sheet

1st the long one, 2nd fat

SPL:
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Old 10th October 2006, 09:52 PM   #2
Henkjan is offline Henkjan  Netherlands
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Old 10th October 2006, 09:54 PM   #3
Henkjan is offline Henkjan  Netherlands
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now woofer displacement
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Old 10th October 2006, 09:57 PM   #4
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Old 10th October 2006, 09:59 PM   #5
Henkjan is offline Henkjan  Netherlands
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and group delay
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Old 10th October 2006, 10:07 PM   #6
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From the response, long version. It'll work better in-room, as room-gain will list the response which is curently rolled off.

Thought about doing an MLTL?
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Old 10th October 2006, 10:08 PM   #7
Henkjan is offline Henkjan  Netherlands
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Old 10th October 2006, 10:13 PM   #8
Henkjan is offline Henkjan  Netherlands
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Quote:
Originally posted by Scottmoose
From the response, long version. It'll work better in-room, as room-gain will list the response which is curently rolled off.

Thought about doing an MLTL?
that was also my thoughts, and added to that a gut feel that the bass would sound better, which I feel is supported by the group delay curve, where the hump is at a lower freqency (probably will use a subsonic filter at 25 or 30 Hz to protect the drivers). also woof displacement is lower in the usable range, which should result in lower distortion. or am I just trying to reason my way into what I feel....

nope, have not considered a MLTL...
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Old 10th October 2006, 10:47 PM   #9
MJK is offline MJK  United States
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I like the 3 to 1 taper design better for the following four reasons.

1. The larger taper is going to raise the frequency of the first harmonic of the tuning frequency relative to the fundamental. There will be more of a frequency spread between the 1/4 wave tuning frequency and the 3/4 wave first harmonic. The higher this frequency the more effective the stuffing is at reducing the ripple, the less stuffing you will need and less impact on the fundamental which you want to keep. I would even consider going shorter with a more severe taper.

2. The rolling off response of the long skinny design will only get worst when stuffing is added and the baffle step comes into play. I am afraid that the bass will be very recessed for this geometry.

3. As far as I am concerned the displacement curves are equivalent. Do you think that the 0.2 mm additional displacement will be a make or break difference for the design? Only if you listen to sine waves, for music I don't think it will matter. I don't put a lot of emphasis on the displacement curve and I work with full range drivers with an Xmax of 1 mm all the time.

4. Same type of comment about the significance of the group delay curve. I don't think that the differences matter much.

Those are my opinions.

Hope that helps,
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Old 11th October 2006, 11:30 AM   #10
Henkjan is offline Henkjan  Netherlands
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1. this is indeed the reason why I am still considering the strong tapered design, would want to use as litthe stuffing as possible

2. not realy an issue as it's gonne be a sub <100Hz only

3. why I do look at it, in the sub region displacement could be an issue as this will also be used for HT, and with the longer design the displacement remains low downto ~30 where with the short design this is ~40Hz

4. noted (don't usually look at GD myself, but many others make it an important design objective)

let me refrase maybe: has anyone done a listening comaprison between a long and short line? because that's what really counts of course
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