MLTL for prototype drivers from China

[Les Hudson]

FATE

I'm fine, thank you. I don't post very often on this forum but I'm always lurking.
Paul

It's funny , I have not been on this site since 2009

 

[Les Hudson]

porting

You have to keep in mind the length of the port and make sure there's enough clearance between its internal end and the opposite panel. You can make the port smaller in diameter and that will allow it to also be shorter, but then the air velocity will be higher at resonance, which increases the likelihood of audible port noise. So, no, I would stick with an internal width of 7", making the external width at 8-1/2" if using 3/4"-thick side panels.
Paul

I have a lot of experience stuffing port ducts in boxes with limited space. I rarely use round ports. Rectangular ports allow for bends. Also as a last resort, the port can be external. I think I may have seen one of your boxes with an external port.

 

[GM]

I will build this model as well. Can you please give me more info on driver placement , port placement , port size , ect. Thank you Greg.

You're welcome!

Hmm, I wrote it up to post.......... Oh well.............

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FWIW, in a 56” i.d. MLTL to get a ~38” seated ear height, I calc’d a ~1.784 ft^3/~38 Hz Fb max flat alignment, though in a sim its ¼ WL vent damping lowers it to ~34 Hz, so falls in-between ya’ll’s designs.

L = 56”
CSA = 55”^2 [recommend either 5.8” x 9.5” or 4.6” x 12”]
zdriver = 18.7”
zport = 44.8”
dport = 2.5”
lport = 3”

All dims i.d. and approximate. Sim based on 0.2 lbs/ft^3 of loose polyfil distributed along its entire length, though prefer lining one side, back and top with 1” acoustic fiberglass insulation down to the vent, then either shorten and/or damp the vents individually to either measure or at least sound flattest in-room at the LP.

GM

 

[pkitt]

I've never used an external port on any of my builds, so it must have been a build by someone else.
Paul

I have a lot of experience stuffing port ducts in boxes with limited space. I rarely use round ports. Rectangular ports allow for bends. Also as a last resort, the port can be external. I think I may have seen one of your boxes with an external port.

 

[Les Hudson]

Sorry it must have been someone else on the PE crew. They were using an exterior port for easy tuning.

 

[Les Hudson]

Paul , your model sounds great . It outperforms the BR. It has increased bass and better extension without the loss of mid/bass. Sounds very linear. You will have a laugh when you see the pics. The cabinets are very unique. They are now in the paint shop and I will post pics once complete. Thanks again for your help.

 

[pkitt]

That's good to hear, Les, and you're welcome. You probably would have been just as happy, maybe happier, if you had built GM's design since he achieved a lower f3 due to the larger box volume. But, since you wanted to compare an MLTL to a BR having the same tuning frequency, I assume this was a bit more interesting and fun.
Paul

Paul , your model sounds great . It outperforms the BR. It has increased bass and better extension without the loss of mid/bass. Sounds very linear. You will have a laugh when you see the pics. The cabinets are very unique. They are now in the paint shop and I will post pics once complete. Thanks again for your help.

 

[Les Hudson]

I'm also building GM's model but in a unique style also. Pics later