Dual RL-P18 LLT for my 2000 cu ft HT soon - Page 9 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #81 of 183 Old 06-05-07, 03:38 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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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.
Most of the energy transmitted to a box is mechanical coupling from the driver mounted into the box. Internal air pressure -- even in a sub is, at max, 1/3rd of the energy and particularly in a vented box, much less than that,

A larger box means larger panels which are easier to excite... it should be well braced and ideally no 2 subpanels should be the same (in practise thou you will probably have pairs of identically shaped sub-panels on opposing sides of the box). You do want to avoid subpanels that have dimensions close to one another. Given a panel, the best brace orientation is the one that divides it into panels most removed from being square (ie in a floorstander a shelf brace is much less effective than a longitudinal brace. I'd try for sub-panels less than 12" (you only need consider the smaller dimension in a rectangle)

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post #82 of 183 Old 06-05-07, 03:53 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Dave...you complicate things too much...I bet what you're talking about couldn't be perceived without measurments. I have build my car sub with no bracing at all and it is pounding 130+db at listening position.... And it is pretty flat down to 25 Hz. Bracing is good certainly, but IMO not so critical as you think.

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post #83 of 183 Old 06-05-07, 05:21 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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I bet what you're talking about couldn't be perceived without measurments
It is actually easy to hear and hard to measure.


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I have build my car sub with no bracing at all and it is pounding 130+db at listening position.... And it is pretty flat down to 25 Hz.
With typical cabin gain in a car that last is a next to meaningless spec. And i guess if all you are interested in is pounding then the side walls acting as passive radiators would be a good ting.

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Last edited by planet10; 06-06-07 at 03:21 AM.
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post #84 of 183 Old 06-06-07, 03:20 AM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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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
chuffing....No it's not going to happen! Although I have no experience with the 18" RL-p, I have quite a bit with a single and dual 15" RL-p drivers in a leaky 2880 sq ft room.. your gonna have massive headroom. I cant imagine you being in need of more performance/bass, I mean really!!

Cant wait to hear your impression of what just a single unit can dish out, along with all the pics.
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post #85 of 183 Old 06-06-07, 05:14 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Hi Steve and all Friends at HTS

Unfortunately (is it?) I have been used to car bass, of course I will never ask the subs to produce that kind of loud bass though I think they could (because noise floor is much lower at home....and the equivalent of car satisfaction at home would be at -10 db or so for me)....Nevertheless I just want to have clean, deep bass with unvelievable headroom to close this bass upgrade illness forever.

I have been designing the boxes all day, and I have been to a workshop to have the wood cut at night. I found some good 1" MDF instead of the initial 22 mm.

That's all I could do today, I have some photos that will be uploaded later (I'm too tired). I must admit that I did half what I expected with twice more effort than I thought....

Tomorrow will start the assembly and I hope to have them painted on friday. I can't wait to see the results.

I have a quick question for you fellas:
- would you let the speaker cables under or above insulation?

Note: I was quite disappointed with the lack of strength/hardness of MDF (Not that it flexes but it is very easily scratched and corners very easily broken...although I bought the finest I could find)...I don't know if an external layer of veneer would make the box more resistant....Anyway I hope SQ will be worth the use of MDF...

But overall I am happy.

Thanks all!
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post #86 of 183 Old 06-06-07, 05:16 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

Steve_nn,

I promiss to let you have anything I note about a single unit as soon as ready.

Best Regards
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post #87 of 183 Old 06-06-07, 05:44 PM Thread Starter
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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planet10 wrote: View Post
It is actually easy to hear and hard to measure.
Sorry, there's no such thing as "easy to hear and hard to measure"...Ilkka, pls give us your opinion.
Quote:
With typical cabin gain in a car that last is a next to meaningless spec. And i guess if all you are interested in is pounding then the side walls acting as passive radiators would be a good ting.
dave
I am not only interested in "pounding", though this is a very important factor to enjoy a sub IMO. Side walls acting as a radiator is quite an exageration also
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post #88 of 183 Old 06-06-07, 05:59 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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Sorry, there's no such thing as "easy to hear and hard to measure"
Sure there are. Lots of them.

Quote:
Side walls acting as a radiator is quite an exageration also
Not at all.

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post #89 of 183 Old 06-06-07, 06:41 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

I suspect that there are things that are easy to hear, but difficult to measure, without specialized equipment or techniques. For example, measuring a sub's freq response, does not tell you how damped it is, a waterfall plot may help with that.

Regarding the physical logistics of moving a 300# sub, can the final fabrication be done in place? Perhaps the baffle could be separate, and mounted in the room, and of course the drivers and electronics can be mounted in room. Is there any reason not to make two cabinets? If I'm not mistaken (and I quite often am) the volume needed for a dual cabinet is ~twice the size of a single. This would cut the cabinet size in half, making moving a bit easier. A bit more wood is needed, however.

Of course two 150# cabinets wouldn't be as impressive when they crash through the floor to the room below.:raped:

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post #90 of 183 Old 06-06-07, 08:56 PM
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Re: Dual RL-P18 LLT for my 2000 cu ft HT soon

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would you let the speaker cables under or above insulation?
Doesn't matter, I would just be sure you give yourself a little extra on the leads to assist in putting in the driver. A extra 1/2 inch just doesn't cut it.
Quote:
(is it?)
It is!
Quote:
Note: I was quite disappointed with the lack of strength/hardness of MDF (Not that it flexes but it is very easily scratched and corners very easily broken...although I bought the finest I could find)
Working with such large panels can be quite daunting and one needs to factor this in when handling them.. a guy really has to watch the corners. Just do the best you can and everything can be squared up in the end. You might consider rounding all the corners and edges off after it's completed? It's really easy to do.
Quote:
3) reflecting high frequencies at an angle will increase the amount of travel before they will go through the speaker cone, (as opposed to hitting a flat piece of wood and bouncing right back) decreasing their amplitude
I have thought of this, but never tried it.. good idea imo. Since your units are so large, might I suggest you seriously consider this blaser? I think I might even line the braces? I don't mean to be presumptuous, but SQ is everything and things do make a difference. The 600 l unit I built might have benefited from this? I do notice that all the sono LLT's I've built have a slight edge in SQ over my box LLT. It could be attributed to a lot of things I admit, but none the same.. I have thought of this in the past.

Last edited by steve nn; 06-06-07 at 09:08 PM.
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