long-thin vs fat-short TL

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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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Scottmoose said:
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...
 
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,
 
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
 
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

The displacement is lower but so is the SPL. If you raise the SPL to be equal, I bet the displacements will be very close. Chances are that the bass volume knob will be turned up more on the long thin design.
 
Hi
Just posting here out of curiousity. I have a friend who has designed a couple of good sounding speakers which he has sold commercial in Sweden. His bread of the day is to have a similar bass response as with this thinner line. I heard four versions at his home, same speaker tuned differently. One that sounded strange was with a steep roll off. and the shallower more naturally. Now the steep one sounded congested and "ploppy" if you pardon my poor vocabulary.
Just a thought from my side, GM what's your take on this?

Regards Peter
 
Possibly the abrupt transition from flat into a steep, 24db per octave roll-off, or similar, especially if the design with the shallower roll-off you mention extended downward further, and they often do. Also, notionally flat systems below 100Hz are usually anything but, when room gain is factored in. You design for anechoic flat, and you're going to get a +6db boost in the LF at least, most of the time anyway, making the speaker seem boomy and bass heavy. Without more information on the design though, it's difficult to say.

Martin -good points re the length / stuffing etc., I'd forgotten to consider those. Not been at my best over the last few days. I make no excuses.
 
Hi Scott!
It was a small two-way with Seas 5 inch XP cone + Vifa tweeter about 7L. They were tuned to 60-65 hz as I remember. I had these for about 4 years and wasvery satisfied. Simple serie filter and they were made to play with the room instead against as most commercial speakers are made today. Well, room tuning manufacturers have to live also. a:smash:
Cheers
 
I suppose you mean Monacor BIB's. Well they are alive and kicking! Still my Genelec's collecting dust on a wardrobe. Can't convince myself to sell them. They sound good but BIB's have more soul, so to say. Listened to REM's "The outsiders today" and Michael Stipes voice is really organic and drums fast with authority. Still very pleased by other words.
Have a look at the BIB thread. New plans ongoing.

Cheers
 
peterbrorsson said:
Hi
Just posting here out of curiousity. I have a friend who has designed a couple of good sounding speakers which he has sold commercial in Sweden. His bread of the day is to have a similar bass response as with this thinner line. I heard four versions at his home, same speaker tuned differently. One that sounded strange was with a steep roll off. and the shallower more naturally. Now the steep one sounded congested and "ploppy" if you pardon my poor vocabulary.
Just a thought from my side, GM what's your take on this?

Regards Peter

Greets!

It's very driver/room dependent, but my two fave vented designs are acoustically efficient EBS tuned to the lowest frequency it's likely to be called upon to be reproduced, which works best in a corner (think ~IB with extra gain above Fc), or a high aspect ratio reverse taper (up to 10:1) for the same reasons MJK listed except with a final straight section to mass load it/roll it off to a lower Fb.

Bottom line, better too much acoustic efficiency IMO and EQ it out than boost what isn't there, or worse, be left 'wanting' on special effects.

GM
 
Thanks for reply GM!
Well for sure it's driver/room dependant but here we're talking small speakers while my guess is that your taste goes with the bigger boys. I'm maybe wrong but I still have a feeling that with smaller speakers, it's better to have a shallow and earlier rolloff in the bass. At least in my room(s) and it is also my cup of tea.

Well I've seen an article about EBS but can't recall the principle.
I like IB for sure but neighbors get a little grudgy when some huge magnets suddenly sticks out of their wall.:xeye: l

Cheers
 
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