Dual RL-P18 LLT for my 2000 cu ft HT soon - Page 6 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #51 of 183 Old 06-02-07, 02:43 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

I think that any porosity in MDF might be negligeable. But Plywood really seems stronger but at least double cost!!
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post #52 of 183 Old 06-02-07, 02:48 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Actually, the amount of breathing that an untreated MDF cabinet with veneer, or some other nice finish on the outside does seems like it would be so minimal as to be meaningless compared to the dynamic changes of pressure induced by a subwoofer. I only paint the inside as a "belt & suspenders/chicken soup" type of approach, in that it doesn't cost much, and it may actually help seal any place I miss with glue & caulking.

I certainly wouldn't call it hermetically sealed, unlike Carnac the Magnificent's mayonaise jar kept on the front porch of Funk & Wagnall's house.

Paul
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post #53 of 183 Old 06-02-07, 03:02 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

FOR THOSE INTERESTED IN THE RL-P18 TESTING BY ILKKA, THEY ARE WELLCOME TO CHECK THIS:http://www.hometheatershack.com/foru...html#post38201.

I AM POSTING THIS HERE AS ALTHOUGH IT MAKES SOME TIME ILKKA HAD PROPOSED TO TEST THE WOOFER (AS FAR AS DONATION WOULD COVER THE DRIVER FEES), I JUST NEW TODAY, AS I WAS ONLY LOOKING AT THIS DIY FORUM....SO MAYBE SOME OF YOU JUST DON'T KNOW!
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post #54 of 183 Old 06-02-07, 03:26 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Quote:
According to the modelling softwares, lining the walls does not change the tune but slightly the FR...Anything wrong with it?
I don't think it's bad, it's just that stuffing changes the effective size of the box. I think you can calculate that size change and alter your box size in the modelling software and see what happens.....

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post #55 of 183 Old 06-02-07, 03:33 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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brucek wrote: View Post
I think you can calculate that size change and alter your box size in the modelling software and see what happens.....
brucek
Insulation is supposed to make the box appear bigger, not smaller....That's the issue: How larger??
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post #56 of 183 Old 06-02-07, 05:16 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Cables now...What gauge is required to support 2000 W? Is 16 enough

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post #57 of 183 Old 06-02-07, 06:22 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Well, I'd use 12 or 10 gauge...........
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post #58 of 183 Old 06-02-07, 10:33 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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Thank you for your post , I just need some clarifications pls
What do you mean by dead center?
Do not put a brace exactly in the middle of a panel. A more general statement is that any brace should not divide a panel into 2 (or more) identical sub-panele.

Quote:
How? Pls elaborate, Do you mean that not stuffing would be acceptable?
According to the modelling softwares, lining the walls does not change the tune but slightly the FR...Anything wrong with it?
As far as the frequencies a sub should be producing, damping has no effect. It will thou increase the appartent size of the box. I would not trust a modeler (except maybe MJK within linits) to account properly for the stuffing.

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post #59 of 183 Old 06-02-07, 10:37 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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I think that any porosity in MDF might be negligeable. But Plywood really seems stronger but at least double cost!!
And what proportion of the total cost is that compared to the cost of the driver(s) and the effort you are putting into it?

Unless you are somewhere where the price of wood is out-of-site (ie BB in Western Australia), arguing about the difference in cost of panel material is penny-wise, pound foolish.

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post #60 of 183 Old 06-02-07, 11:19 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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And what proportion of the total cost is that compared to the cost of the driver(s) and the effort you are putting into it?

Unless you are somewhere where the price of wood is out-of-site (ie BB in Western Australia), arguing about the difference in cost of panel material is penny-wise, pound foolish.
This is what I meant by a religous war...

Some people belive that the mass and uniformity of MDF makes for a better speaker, others believe the strength of BB is better and there are even a few lost souls that believe particle board is best. I have been unable to find a definitive answer by someone that has done empirical, objective testing, and until I do, I will use plywood and MDF interchangeably, as in the speakers I am currently building that have a bit of both.

I have thought a little about a test regime. If I can get around to it what I thought I might do is take a driver (I have some HiVi A5+ 5" drivers laying about) build two cabinets that WinISD says is an optimal for sealed with a 1-1/4" MDF baffle. One cabinet would be 13 ply BB and the other MDF with veneer, braced as similar as I can make it. For testing I would;

1) Do freq tests measuring from one meter on axis, and set amplifier for a reasonable level such as 85db.

2) place the mic face down on each of the panels coupling the mic to the panel, and run the same tests.

3) place the mic about 1-2mm away from each panel and re-reun the above tests.

What I would hope to find is if there are any differences.

Paul
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