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Old 6th March 2008, 05:31 PM   #1
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Location: Appleton, WI
Default GM MLTL fine tuning

I have my GM MLTLs for the Fe127e up on the operating table.

Earlier I was emboldened by doing my first mod to a 50 cent Panasonic 4 in that came from a line array. The line array never worked out well for me after doing all the cutting for 16 speakers on 2 baffles.

So the Panas were sitting in a box.

But this is background to the MLTL which has a measured drawing at
zillaspeak.com

I've been using that design amongst others for years and would rebuild the cabinets in something other than particle board shelving
after some woodworking practice.

But before that. I can experiment on the particle board boxes for several things.

1.) Flush mounting.

I have a crude zip tool that can be used for small routing jobs. I'm willing to try this after trying a suprabaffle that didn't produce much of an effect.


2.) Inside there's just a bit of fiberfill. But Jeff (Zilla) shows a vented box similar to the MLTL that he built with some acoustic foam in the top.

--> GM is this a good notion for the top of the MLTL? I have
received a bunch of that stuff in some returned hard drives from Seagate.

What should be used on the rest of the inside?

The speakers are direct connected and the wire simply exits the back of the cabinet. The wire is solid 24g using the natural resistance tweak.

GM you were right about the port. It's 6 inches and I wouldn't change that. I am trying to figure a way to get the port inside the box and side firing rather than sticking out the bottom. Out the bottom has produced the best effect however.


I have not tried to route square shapes free hand for flush mounting-- only rebating circles. I imagine it's similar to making one of those 'welcome signs' they make at the mall. I have the smallest diameter straight bit I can find.


Then it's on to speaker decoupage and other adventures.

While this is going on I have the BIB and FrankenHarvey set up and playing.
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Old 6th March 2008, 07:37 PM   #2
GM is offline GM  United States
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Default Re: GM MLTL fine tuning

For narrow MLTLs, you need baffle 'wings'. Try them with a total baffle width of 30", then with 14 - 16 ga wire and report back. BTW, I assume you have the wire exit well stuffed with roping caulk or similar to make it airtight.

Hmm, the foam packaging I'm familiar with is closed cell and you need open cell since the former actually reduces net Vb, altering tuning. Regardless, my preference is 1" acoustic fiberglass on the top, one side and back at least down to just below the driver since for a given density it damps much more over a wider BW, ergo usually considerably less can be used. For serious damping I use 'teased' R-19 fiberglass insulation or R-25 Miraflex, the so-called 'itchless' fiberglass.

GM
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Old 6th March 2008, 09:31 PM   #3
jnb is offline jnb  Australia
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Default Re: GM MLTL fine tuning

Quote:
Originally posted by loninappleton
GM you were right about the port. It's 6 inches
Six? I have been using 1/1/8
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Old 6th March 2008, 09:53 PM   #4
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Default Re: Re: GM MLTL fine tuning

Quote:
Originally posted by jnb

Six? I have been using 1/1/8

It's 2x6 in with the pvc port out the bottom-- all the way out to have the total cavity empty. The sound has been very pleasant that way.

Earlier I tried the little ports and it went boomy.

Today I routed for flush mount on one box. Those little tools run too fast. I had smoke and a few hot cinders too. To smoothe the seal, a bit of rope caulk might fill in where the cutout goes a bit wiggly.

Not too sure about the 'wings' GM describes above. That will take more drawings for whomever can do the Sketchup stuff. I can picture wings. I just can't picture them working.

But this is supposed to be the Bodacious Tweakage Final Draught of the thing.



Do you have pics of your build? I cannot recall seeing it.
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Old 6th March 2008, 10:03 PM   #5
jnb is offline jnb  Australia
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Default Re: Re: Re: GM MLTL fine tuning

Quote:
Originally posted by loninappleton
It's 2x6 in with the pvc port out the bottom--
I was going from this
http://www.zillaspeak.com/fostex127eMLTL.asp
Is there a better plan?

Quote:
Not too sure about the 'wings' GM describes above.
I have had good results against a wall.
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Old 6th March 2008, 10:17 PM   #6
GM is offline GM  United States
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Default Re: Re: GM MLTL fine tuning

Quote:
Originally posted by jnb

Six? I have been using 1/1/8
I've done many different sims for the FE127E and Lon's variant is longer/bigger/tuned lower than some.

GM
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Old 6th March 2008, 10:21 PM   #7
GM is offline GM  United States
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Default Re: Re: Re: GM MLTL fine tuning

Quote:
Originally posted by loninappleton

Earlier I tried the little ports and it went boomy.

Not too sure about the 'wings' GM describes above.
OK, do you normally have then near/at a wall or corner?

You add braced flat panels to each side of the baffle to create a mini-false wall (1/4 space loading), like for OB.

GM
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Old 6th March 2008, 10:24 PM   #8
GM is offline GM  United States
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Default Re: Re: Re: Re: GM MLTL fine tuning

Quote:
Originally posted by jnb

I was going from this
http://www.zillaspeak.com/fostex127eMLTL.asp
This is my original T/S max flat alignment and the one I feel is the best vented performer overall in theory and add a sub system if you want more LF gain BW.

GM
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Old 7th March 2008, 04:00 AM   #9
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Default Re: Re: Re: Re: Re: GM MLTL fine tuning

Quote:
Originally posted by GM


This is my original T/S max flat alignment and the one I feel is the best vented performer overall in theory and add a sub system if you want more LF gain BW.

GM

I know mine is unusual at the port.

Go with the expert for a strict interpretation. I'm good with what comes out the port. I just think that inside the box needs a little work plus the eventual driver treatments.

What I wonder is where GM gets all this insulation product living in
Georgia.



I haven't used fiberglass since kits in the 70's. But I'll take the advice about avoiding the closed foam even though it looks kind of neat. If there's itchless fiberglass and I can get a small quantity, I'm willing to try it.

As to placement, the one I was using (I also do the unusual thing of
not using stereo pairs but mix and match) is about a foot out and toed in at the corner of the wall. The driver winds up being at about 41" on the stand with open bottom for the port tube. it looks
pretty much line the drawing above. It's open 2 sides and solid 2 sides.
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Old 7th March 2008, 06:26 AM   #10
GM is offline GM  United States
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Same type businesses you do I imagine. We need it to insulate against the heat. I've only seen Miraflex in large rolls.

GM
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