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Old 18th November 2012, 12:52 AM   #21
GM is offline GM  United States
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FWIW, I looked at this driver in a MLTL awhile back, though it's somewhat larger than 6 ft^3 and tuned lower, but scaling it back a bit and raising tuning to around 22 Hz still seems a viable option and since it's a bit larger than Bjorno's, it's a couple of dBs more efficient down low in a sim.

It's long at 81.75" i.d., so needs at least one fold, but only as wide, deep as required to physically install the driver and vent [~126.83"^2 i.d. to = 6 ft^3 gross or about 5.49 ft^3 net], but being end loaded for both the driver and vent to get max floor boundary gain, this shouldn't be a problem.

The vent would be a 6" i.d. dia. pipe ~8.5" long if laying right on the cab 'floor' or ~12" long if not, so would exit out the side relative to the driver baffle. Might be best to try different lengths in room though since the amount of boundary gain is an unknown.

Sim is minimally damped since the TL action is plenty strong enough to damp the driver, vent, i.e. top, back one side lined with just enough damping to quell any 'hollow' sound and with a typical 80 Hz XO for HT, you can ignore any 'ripple' above this frequency.

GM
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Old 14th December 2012, 03:11 PM   #22
Veke76 is offline Veke76  Finland
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Quote:
Originally Posted by bjorno View Post
Hi,

If you find it necessary: At a small SPL/FR flatness expense: You can tune this ML_TL suggestion even lower than 23 Hz using a Total System Volume less than 5 cu.ft.

If you're interested I let you know the exact amount of required stuffing and the ~damping material density needed, in a few days at most

b
This design started to interest me and tb46 drawings show it's not too big to make. So it's cabable of 117dB or more? A minor change possible? I could use about overall of 128dB+, F15 of 20Hz this would nicely be added by room gain. A normal F3 of 30-35Hz TH/TQWP might work too. Is this spl too much asked from Lab 15?
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Old 14th December 2012, 09:27 PM   #23
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Quote:
Originally Posted by Veke76 View Post
This design started to interest me and tb46 drawings show it's not too big to make. So it's cabable of 117dB or more? A minor change possible? I could use about overall of 128dB+, F15 of 20Hz this would nicely be added by room gain. A normal F3 of 30-35Hz TH/TQWP might work too. Is this spl too much asked from Lab 15?
Off the top of my head you would need 4 Lab 15 subs to reach that kind of spl. The question I have is why do you want that spl?
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Old 14th December 2012, 09:49 PM   #24
tb46 is offline tb46  United States
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Hi duanebrow,

Two of bjorno's MLTL's in parallel into 1pi space (Eg=60), scary stuff :-) :

Regards,
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Old 15th December 2012, 03:27 AM   #25
Veke76 is offline Veke76  Finland
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Originally Posted by tb46 View Post
Hi duanebrow,

Two of bjorno's MLTL's in parallel into 1pi space (Eg=60), scary stuff :-) :

Regards,
Can you post the same with 1 MLTL into 2pi space? Just to compare some designs at Data-Bass

I was also wondering about the s4 s5 duct. It's 280cm^2 and thats same as 6" - 8" diameter port. Also width/height ratio min 9:1 is at close.

Otherwise it's unbelivable how much you can get from 88dB efficient driver!
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Old 15th December 2012, 03:03 PM   #26
tb46 is offline tb46  United States
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Hi Veke76,

See bjorno's Post #7 for the single MLTL into 2pi simulation. The fold I drew up in Post #9 was a general suggestion, the aspect ratio of the duct is 5.64:1 (15.5"/2.75"). I went straight of bjorno's data, and did not enter any end corrections; for any box like this I would suggest a trials box to get a better idea of the stuffing location and density, and so on. If you take this design into AkAbak you can also fiddle with the design some more.

Regards,
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Last edited by tb46; 15th December 2012 at 03:14 PM.
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Old 15th December 2012, 03:23 PM   #27
Veke76 is offline Veke76  Finland
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Ok. I calculated in my head that it would be possible get 124dB from lab 15 but this depends on the design. 117dB in some sims is close what I'm getting from sealed. I'd be interested seeing comparison 73L sealed vs. Bjornos MLTL.
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Old 15th December 2012, 05:00 PM   #28
tb46 is offline tb46  United States
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Hi Veke76,

Sooner or later you'll have to fire up Hornresp. :-)

Regards,
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