Dual RL-P18 LLT for my 2000 cu ft HT soon - Page 8 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #71 of 183 Old 06-03-07, 05:42 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Quote:
brucek wrote: View Post
Apple has their own audio class library
CORE Audio is pretty good, and Apple only has so many resources...

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post #72 of 183 Old 06-04-07, 03:39 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

I think I will go for 8" port because of too low a port resonance with a 10" port. Nevertheless, I have noted something weird to me between Winisd and Unibox concerning the ports:

- I think I will do flared ports (both inside and outside).
Winisd says flanged (is it same as flared?).... port length decreases by swiching to flanged
- In Unibox, we have either flush or flared, but port length increases by switching to flared

Could anybody help pls?
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post #73 of 183 Old 06-04-07, 04:14 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

A flared port that has the same basic diameter needs to be longer.

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post #74 of 183 Old 06-04-07, 04:24 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

I thought it is the same length, but you measure from half way down the flare. This means the entire port is longer, but you can use the calculations for a non-flared, by adding this amount.

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post #75 of 183 Old 06-04-07, 04:41 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

If you need say 30" of port length for example, and want to use flared ends, the actual length of the cylindrical port will be less than 30", as half the length of each flare needs to be taken into consideration. If you do not use flared ends, the actual length of the cylindrical port would need to be 30" on its own.

As for MDF vs Plywood, while a more rigid enclosure is always better, realize that a LLT is one of the least demanding subwoofer enclosure applications, as the force created by the driver is spread out over such a large area (large enclosure), meaning lower pressure than say a small sealed sub using the same driver. MDF with bracing every 12" or so should be just fine.


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post #76 of 183 Old 06-04-07, 04:42 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

So why when swiching to Flanged in Winisd, the length decreases?

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post #77 of 183 Old 06-04-07, 04:53 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Hi Steve....Nice to see you around and thanks for your generous help in this world ... The problem I have with MDF is of a complete different nature from strength or SQ.... I don't know how I will get it to my house due to it's weight....I am really not joking, the boxes will be bigger than getting into the lift (yes it is a small one for my private building), and both of them will have to be carried-up through the stairs to the third flour(boxmaker expects them to be 300 Lb+ with 3 layers front baffle) And I do not want to start with scratches or so either
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post #78 of 183 Old 06-04-07, 05:00 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Quote:
So why when swiching to Flanged in Winisd, the length decreases?
I think that member collo has a good site about flares

He says:

The generally accepted adjustment is to subtract half the flare radius from the physical length to obtain the effective length. If both ends of the port are flared, the adjustment is done for each flare.

These ports have a flare radius of about 1 inch, so your design length of 17 inches means you build a port that is 18 inches from end to end.




So if you have a length in WinISD and you add a flare, you need to shorten that length to accomodate the flare length.

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post #79 of 183 Old 06-04-07, 05:05 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Thanks Brucek!! and maybe Unibox takes the flare length into account so that the indicated length of the port increases....This might be the diference.
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post #80 of 183 Old 06-05-07, 03:16 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Guys....The subs arrived today!!!! They are huge....I knew they are, but it is a completely different feel to see them...I must admit I was a bit afraid:holycow: These drivers are for my tiny 1800 cuft room??:raped:

I bought some accessories: 8 binding posts, 15m 14 gauge cable, 8" PVC pipes, and I also ordered the insulation material....(it is 1" corrugated sheets of polyfill....the seller qualified it as an "acoustic sponge"....and it is a sponge material isn't it). see photo.

Tomorrow should begin the fabrication with either 22 mm MDF(veneered maybe) or 18mm plywood (whichever is available), while the insulation material should be received on Thursday....Painting to be applied Thursday/Friday, and Hopefully you should see the first FR Saturday.

Note: 8" are huge really, I don't know how on earth I could hear any shuffing, or reaching core velocity....But concerning the drivers that's another story....I am pretty certain only one driver would reach RL quite easily....We'll see
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