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Dual RL-P18 LLT for my 2000 cu ft HT soon

31K views 182 replies 19 participants last post by  Blaser 
#1 ·
Final design not completed yet, but I will go for 2 boxes 550-600 L effective, 16 Hz tune, 8" or 10" port, powered by EP 2500, dual 2 ohm configuration.

I am not that good in woodworking, so I am only making the design on paper, but will have the job performed by a carpenter.

I have some variables I would like your advice about:

- MDF or not? If MDF, 16mm, 18mm, or 22 mm? Front baffle will bear both the driver and port.
- Is bracing a must? Never read that anybody made an enclosure without bracing, but I did that for my 4cu ft car sub. and it is rock solid and working very very well, I can even stand on it... no problem. Of course at least the port will be internally supported.
- Insulation: Is it a must? If yes, is 1" fiberglass ok? Should the volume be taken into consideration? I never read someone did...

Your inputs are highly appreciated.

Blaser
 
#75 ·
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.
 
#81 ·
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)

dave
 
#76 · (Edited)
So why when swiching to Flanged in Winisd, the length decreases?
 
#77 ·
Hi Steve....Nice to see you around and thanks for your generous help in this world :T... 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:dumbcrazy::bigsmile::R....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:boxer:(boxmaker expects them to be 300 Lb+ with 3 layers front baffle):surrender: And I do not want to start with scratches or so either:rolleyes:
 
#78 ·
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.

brucek
 
#79 ·
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.
 
#80 ·
Guys....The subs arrived today!!!!:jump: 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:bigsmile:, 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:yes:
 

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#82 ·
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.

Blaser
 
#83 · (Edited)
I bet what you're talking about couldn't be perceived without measurments
It is actually easy to hear and hard to measure.


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.

dave
 
#84 ·
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.:cool:
 
#108 ·
Cant wait to hear your impression of what just a single unit can dish out, along with all the pics.:cool:
Well, Yesterday I tried only one with roughly a 2000 W amp. bridged 8ohms. Indeed the FR is the same approx. But I was very surprized how powerful only a single driver is:raped:.... All the bass notes seemed natural (live), very precise, hits hard when needed and goes really deep when required. Multiple bass notes were not a concern at all!! It was playing simultaneous loud kick drums with background bass notes effortlessly.... When I pushed it hard, I had to go back to the boxes and check if I did not connect the other by error... This sub is a monster.

I played some "50 cent" with a single box and I was hitting 124 db peaks with my digital RS meter:scared:. The amp clipping led was only occasionally slightly blinking, and no severe compression was noted. I can tell you that in my room RL in movies should not be a problem with a single driver....:yes:

If anyone likes me to do anything special, or any special test, I will be happy to:)
 
#85 ·
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....:sweat:

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!
 
#86 ·
Steve_nn,

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

Best Regards
 
#89 ·
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:

Paul
 
#90 · (Edited)
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.:thumbsdown:
It is!:)
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.
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.
 
#91 ·
Hi all,

I have almost completed (painting only still not applied) and performed some listening tests for my project... The initial results are very positive...Photos and FRs will follow most probably tomorrow:yes:

Blaser
 
#93 ·
Hi all,

I have now some time to post some pics and FR.

I ended with a 630 L approx tuned to 13.5 Hz pwered by ???? you'll see:R
 

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#94 ·
Front baffle is dual 25mm thick, with driver flush mounted and port flared externally by 25mm.

1"*1" Braces were used on the walls each 30 cm, and two lateral braces were applied perpendicular to the largest wall 107cm * 70 cm.
 

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#95 · (Edited)
Here is the FR....Red is equalized,more info will come about the design and the T amp soon.
 

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#96 · (Edited)
Before I have any comments I would like to thank each and every one on this forum who has participated in this thread, as well as given precious advice to me. Thanks also to Steve Callas who's famous article was behind this upgrade project, as well as his help.

Special thanks to Ilkka who has help me and teached me how to design a sub. I have been in communication with him for months and he never let me feel anytime he was fed up or so....Thank you Ilkka.

Ilkka was also behind my choice of the T-amp 2400....rated 2000 W into 8 ohms bridged. The manufacturer doesn't tell the 4 ohm power but it was measured and it will be around 2200-2300W RMS at 4 ohs bridged with quite low distrotion.

I am using it bridged at 4 ohms

I have hit 126 db uncorrected in room on some music material today at listening pos...4 m away from subs.

This Amp is weighing 25 Kg net :eek:I got this delivered for less than the price of the Ep-2500...but that's in Egypt. This amp was used in the famous tests by Ilkka.

I will add another one, not because I need more bass, but because I see this amp is a steel for its specs.

More posts will come about my impressions....
 
#97 ·
Here is the FR with mains for music and movie configurations
 

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#100 · (Edited)
Yes, this is both subs running.

Problems solved? yes definitely! That weird difference of 6 db between my left and right at 45-60 Hz is now gone....See the photo and you will understand why I am now feeling what a wall of bass is!!!

I gain 6 db up to 80 Hz compared to a single sub....The sound is amazing so simple as that
 
#99 ·
Here are the mains, see the room effect...
 

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#101 ·
How do I finish them now? They are now used as huge tables and they carry many things...but I want to see a better look than bare MDF!!
 
#103 ·
On thing I have noted and which is quite amazing. With my old sub, I was hitting 115-116 db peaks. Now with the new ones, if I hit 112 db for ex. it seems much louder than say 115 db with the old sub.

Does the deaper bass play a role here?

I feel that a lot more courage is needed to hit 112 db with the new subs than with the old one... It seems a more difficult task (because I feel the sound is much higher....)
 
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