Home Theater Forum and Systems banner

Dual RL-p18 LLT begun

34K views 110 replies 18 participants last post by  Scott S 
#1 ·
Hi Folks,

I've been lurking here for a couple of months now and I guess it's time to start my first post. I have a dedicated theater room which is 14'x21'x8.5' that I built back in November 2003 and currently I have a pair of Definitive Technology BP-2002s behind my perforated 10.5' wide 2.35:1 screen. The BP's have a 12" sub built into them powered by a 125 or 150 watt plate amp. During most movies, the bass seems adequate but during some movies, presumably movies with notable LFE, I can hear the subs distort. I was watching Alien 3 the other day and at the very beginning of the movie, a spaceship pans across the screen and it was the first time I actually tried to lower the volume of the movie. Naturally, my wife or friends don't even notice the problem, but I have been noticing it more and more. I don't have REW setup yet and haven't used my newly aquired SPL meter from Sonnie to check FR and SPLs but I do intend to do that before switching over to the new subs. I'm sure the BP's don't go down as far as I thought they did when I first got them.:hissyfit:

I was considering a dual RL-p15 project but I have been waiting for the RL-p18's and I snagged two at Mike's introductory offer. I figured if one was good, two had to be better. :bigsmile: I received the drivers Thursday and I must say, they are absolutely huge! You can measure 18" with a ruler and try to estimate their size but until you have them sitting in front of you, you just can't imagine how big these things are! Getting the drivers and picking up the 6 pieces of MDF today made me realize that maybe one RL-p18 would have been enough but I am going to press on.:coocoo:

I would have went with an IB, but I don't like the idea of attaching the drivers directly to the structure of the house. I have 1400lbs of sand in my stage area and thought a LLT would be better in my situation. I think the bass traveling through my attic and into the rest of the house would freak my wife out even more than the two large boxes.:scared: At least she will only see the boxes during construction...

I don't have any pix yet but I will try to get some uploaded here as I make a little more progress. I am making two MDF boxes that will each have an internal area of 64.5"x37.5"x16". Each box will have one driver and one port. When I built the theater, I had never heard of LLT subs so I didn't leave gobs of space behind the screen so that is why I only have 16" or so of internal depth for these boxes. If I calculated correctly after bracing and the 8" port I should come in around 550L. I really wanted to go with 650L per box but that would have forced me to move my speakers up too high. Maybe I won't loose as much volume as I calculated...

If anyone can tell me how much volume the RL-p18 is going to take away from my internal volume, I would appreciate it. I will not be countersinking the drivers as I don't care what these boxes look like as they will be totally hidden behind the screen. Also, I am going to use 5/8" closed cell foam to line the inside of the box. Do I subtract the foam volume when calculating effective area? Lastly, should I line the port as well?

-Tom A.
 
See less See more
#44 ·
Can you tell me how long the port is Tom?
It's an 8" diameter port 25 5/8" long, not counting the flare at the end. I used a 3/8" roundover bit for the flare. I was shooting for an effective volume of 550L with a 14.5Hz tuning. Unibox said the port should be 25.94" long. I'm probably gonna be just under 550L by the time it's all done.

Are you using the D4 driver with the two coils in parallel?

brucek
Yes, one D4 driver with dual coils in each box running in parallel. Each driver should see 900 watts per channel into 2 ohms with my Carvin HD1800.

-Tom A.
 
#47 ·
Yes, one D4 driver with dual coils in each box running in parallel
Yeah, I guess the SoundSplinter site show the Re and BL for series coils, so I had to use the trick with WINISD to calculate them when in parallel.

WINISD shows the 8" port at 27.5" inches with one end flared in a 545 liter box tuned at 14.5Hz.

It looks real good at least to my novice playing around. The experts could comment.

Here's SPL of one box with 900 watts applied with a 10Hz, 1st order highpass filter to account for the electronics dropoff down low and a single BFD filter at 48Hz with a cut of -6dB with a Q of 0.7
I guess room gain comes into play and maybe the BFD filter would be less (or none).

SPL

Oscilloscope Text Line Slope Technology



Here's the cone excursion at full power. The Xmax is 27.4, so that looks good to me. It's shows only a bit out of the linear range at full power. The graph goes below Xmax just above 500 watts. That seems good.

EXCURSION @ full power

Text Oscilloscope Line Slope Technology


The velocity exceeds the 5% of speed of sound (~17m/sec) when full power is applied which I'm told is into the chuffing range. But who runs full power. At 500 watts it's about 19 m/sec

VELOCITY

Text Oscilloscope Line Slope Technology


And of course you have two of these monster.

Here's a tip: Don't sit in it when playing full power.

brucek
 
#48 ·
WINISD shows the 8" port at 27.5" inches with one end flared in a 545 liter box tuned at 14.5Hz.
I haven't messed with WINISD much. If it's not too much trouble, can you tell me what tuning I can expect with a 26" port assuming the same 545L?

Here's SPL of one box with 900 watts applied with a 10Hz, 1st order highpass filter to account for the electronics dropoff down low and a single BFD filter at 48Hz with a cut of -6dB with a Q of 0.7
I guess room gain comes into play and maybe the BFD filter would be less (or none).
I don't have a BFD yet. I plan on running it without at first and then pick one up if absolutely necessary. I guess I need to get REW installed so I can measure, huh? I plan on doing a FR on my current pair of Def Tech 2002 (each one has a built in 12" sub) just for kicks. I'm sure the SS's will dig much deeper. :T

Here's a tip: Don't sit in it when playing full power.

brucek
Excellent advice! :T :rofl:

-Tom A.
 
#51 ·
3M adhesive didn't work with closed cell foam

Last week I started to install my 5/8" thick closed cell foam in one of the boxes. I applied it with the "standard" grade 3M adhesive, I believe it is number "77" or something like that. It seemed to work pretty well but after the boxes sat in the garage for a week, I got them out and quite a few of the foam panels were either popping out or had fully popped out. I'm glad I didn't seal the boxes last week like I had hoped to!

So, I re-did the cell foam with button caps that I got at Lowe's. These are basically 1" nails with plastic rings to distribute the force over the foam so that the nail doesn't rip thru.

Here's a pix that shows the cell foam installation with the top lid almost ready to seal up for all eternity:

Vehicle Car Rim Subcompact car Wheel


Note that the picture also shows my super hi tech speaker terminal which consists of 12 guage wire, a hole and liquid nails on both the outside and inside of the box. I figured since the boxes won't be seen, terminals could only cause possible loose connections.

I had some foam left over so I decided why not wrap the port as well:

Furniture Wood


Here's a pix with the baffle screwed and glued. I used almost an entire tube of liquid nails for each baffle. Do you thing I used enough screws? I plan on covering each screw hole and the external seams with either liquid nails or silicone next week. This pix also shows one of the two braces that I added per Rodny's recommendation. I think we all got a good laugh at the "conspiracy theory" but in all seriousness, I think these braces were an extremely good idea...thanks again Rodny! :T

Wood Games


Here's the two boxes on their sides waiting for drivers.

Games Recreation Wood


Lastly, here's a pix taken from inside the driver cutout.

Wood Room Circle Plywood Architecture


-Tom A.
 
#56 ·
It probably wouldn't hurt to trim the foam at the port entry to minimise any risk of turbulence. A sharp knife held at 45 degrees would do the trick
I agree with Collo, you need to cut the foam!
Ok, the pros have spoken :hail: :hail: I will attempt to cut the foam. :bigsmile:

It may be a bit difficult to get to the area to trim it, especially at a 45 degree angle. If I have to cut it rough, how far away from the port opening do you guys think I should cut it?

If I can't reach it well enough to cut it, should I just try to pull that entire piece of foam off?

-Tom A.
 
#53 ·
Here's a pix that shows the cell foam installation with the top lid almost ready to seal up for all eternity:
Does this mean you'll have no access to the inside once you seal this up? The information about the glue was interesting because I would not have guessed that it would fail. In any case, really nice work.

Bob

Never mind about the question. The light just went on and I see what you're doing.
 
#57 ·
The information about the glue was interesting because I would not have guessed that it would fail.
I was quite surprised also. If the foam would have laid perfectly flat, or if I had enough weights on each piece, the adhesive probably would have stuck. That's ok, I don't think the button caps will come undone. :bigsmile:

-Tom A.
 
#58 ·
Are you covering the box with some sort of material??
After I cover the screw holes and any gaps with liquid nails, I plan on painting the area around the driver cutout and the seams of the box black. After that I will apply the same 5/8" closed cell foam that I used on the inside of each box on the baffle, top and sides. This should minimize any sound reflections from bouncing off the box and back through my perfed screen. I currently have Linacoustic 1" thick insulation (HVAC duct liner) on the 3 walls behind my screen.

If you going to paint the box dont forget to use some primer first (the MDF will soak the paint)
No way Rodny...I won't even think about trying to compete with your super smooth glossy finish that you applied to Sonnie's box. :R :surrender:

-Tom A.
 
#61 ·
REW

Today I sealed up the outside of the boxes with liquid nails (inside already sealed with silicone) and I cut a little foam away from the ports per advice in this thread.

Here's the port, it's still not pretty but at least the foam is away from the opening this time.

Circle Audio equipment Electronics Machine Window


I also painted the top and edges of the boxes black...I'll post pics of that another time. I still plan on putting foam on the outsides of the boxes.

I'm off work Monday and plan on taking down my screen and ripping out my speaker stands to make room for these big boxes. :bigsmile:

In preparation for that, I installed REW on the HTPC today and after fighting with input levels and soundcard default input/output devices I at least was able to collect some data on my current setup before I install the RL-p18s. I was only able to measure one of my current subs instead of both because they aren't dedicated subs, they are powered subs internal to each Def Tech 2002. When I hooked up a "Y" from the Galaxy SPL meter to both channels of my Yammy receiver's AUX input, the analog DPL circuit kicked in and played the sound over the center channel. :holycow: So, I just measured the right speaker.

I'm not too sure of my results but here it is:

Text Line Plot Pattern Design


I don't understand why the sound levels are so much higher than my target of 75dB. I set the receiver's volume to give me a reading around 75 dbC on the SPL meter. I watched the meter during the measurement sweep and one time I even set it to fast and max and it only recorded a max level of 83.9 dbC. It sure didn't sound that loud to me but I know bass doesn't sound as "loud" to our ears as higher frequencies. Any ideas or comments?

To make matters worse, here's the same plot but with frequencies down to 2Hz:

Text Line Plot Slope Pattern


There's no way the Def Tech was hitting 118 dbC or so at 2Hz. Is this typical of REW? What am I doing wrong?

I was hoping to get good before and after readings but I'm not so sure it is going to happen. Any ideas would be appreciated before I start taking down the speaker stands Monday. If not, maybe I can get REW working better for the new subs!

-Tom A.
 
#62 ·
Do not take care of the info below 10 Hz, as the SPL meter should not be correct there. I am not familiar with the Galaxy SPL meter, but with the RS meter you have ranges. If this is similar, you have to increase the range and you will have the graphs be shifter lower.

Blaser
 
#63 ·
Re: Dual REL-p18 LLT begun

I don't understand why the sound levels are so much higher than my target of 75dB
Because you likely didn't press the Calibrate SPL button in the Settings panels Mic/Meter tab and then press the button called Set Target Level in the panel called Target Settings (located in the panel left of the graph plot).

Your graph should only be used with a horizontal scale with a minimum of ~12Hz as this is where your response display enters the noise. After that the plot is showing noise that is inversly increased by the meter calibration file. If you leave C-Weight checked it only exacerbates the problem.

See the plots below.

The first plot shows where the impulse response enters the noise floor about -45dB down from the peak level.

The second graph shows where this is consistent with the level of the output entering the noise about -45dB down from the peak (when I incorrectly display down to 2Hz. Once the reading is in the noise and the frequency plot is calculated (from the impulse response) you see the plot rising. Its doing so because the meter calibration file is inversly compensating and creating signal that simply doesn't exist.

The third graph shows where if you have the C-Weight incorrectly turned on, the meter calibration file continues lower and creates an incorrect rising signal that can be misinterpreted as signal. It ain't. Its noise.

Only plot the signal that is above the noise. Which in your case is above 12Hz for this measurement.

Blue Plot Line Text Diagram


Text Plot Line Diagram Design


Text Line Plot Slope Pattern




brucek
 
#64 ·
Re: REW

Because you likely didn't press the Calibrate SPL button in the Settings panels Mic/Meter tab and then press the button called Set Target Level in the panel called Target Settings (located in the panel left of the graph plot).
I previously did press the calibrate SPL button but I definitely did not see the set target levels. That did the trick.

Here's my updated FR of just one of my Def Tech 2002 which have internal side-firing subs. This is the right hand speaker behind my screen in front of the room. The SPL meter is about 18 feet away just behind my primary viewing position at about ear level.

Text Green Blue White Line


Definitely room for improvement! I'm looking forward to getting the RLp's online so I can hopefully show some better graphs! :bigsmile:

...brucek and blaser... Thanks for the help, I do appreciate it! :T Hopefully, I can remember enough of this so that I can post graphs of the RLp-18's under the same conditions.

-Tom A.
 
#65 ·
Can't waid to see the Graphs tjambro
 
#67 ·
Same here! :daydream:
Sorry, no graphs yet but hopefully this weekend or perhaps the next. :whistling: I'm also re-doing my screen frame, so that is gonna take some of my time also and I don't work as fast as I would like. :hissyfit:

Until then, here's some more pics....Sonnie, if I'm posting too many pics please let me know. :bigsmile:

Here's a picture of the boxes in my garage with the older L,C,R stands that had to be removed so the boxes could fit behind the screen:

Loudspeaker Audio equipment Subwoofer Studio monitor Computer speaker


These boxes WILL fit in my room even if I have to cut or scrape the riser coming in the room:

Room Floor House Building Toilet


Here are the boxes in their new home and I hope to never move them again! Note that the 2 2x4's directly in front of the cutouts have been taken down and moved

Room Furniture


I doubt the boxes will move much due to their weight but just in case I bolted them down to the floor:

Textile Room Leather


Ok, these next two pictures show why I should have gotten help putting these massive boxes behind my screen:

Room Furniture Interior design Bed Building

"****, how am I gonna get that box back outta there" :explode:

Room Design Interior design Architecture Furniture

"It's stuck but at least it's almost where it needs to be" :R

I still plan on and believe it or not, there's still enough room to put the 5/8" closed cell foam on the front and outside sides of the boxes. I plan on doing that next weekend and building my new L,C,R speaker stands. I could probably just put the L,C,R speakers on the foam on the top of the boxes but to be safe I'm gonna screw a 12' 2x4 to the back wall and another 12 footer to the screen wall and make little shelves for the L,C,R speakers as well as the Carvin HD1800 amp. I really don't want anything on top of the boxes. Hopefully, I will find time to install the drivers and get them fired up! :praying:

I don't have a picture of the 2 12' 2x4's in my Chevy Cavalier convertible but let's just say it looked tame compared to the two 20' cold rolled steel struts I bought yesterday for the new screen frame and put in the Cavalier! :devil: I brought a hacksaw just in case but I'd much rather cut the strut at home instead of in a parking lot. Note to self: 20 foot strut is much longer than you think and should not be transported in a Cavalier convertible especially during rush hour. :eek: The 2x4's and the steel struts will be painted black so that they can't be seen behind the perforated screen.

-Tom A.
 
#73 ·
Tom, I was under the impression that Open celled foam was better for sound absorption. I'm not trying to pick (maybe a bit, because I'm extremely jealous of your subs ;) ), just wondering if you chose closed cell for a specific reason, or were doing what most of us do, using what you had available. I'm pretty sure that either one will help to deaden the reflections a bit, and you may even want to cover the closed cell with a layer of felt or fabric or something for a little extra damping.
 
#74 ·
Tom, I was under the impression that Open celled foam was better for sound absorption. I'm not trying to pick...
Not a nitpick but a legitimate question. :bigsmile: I honestly don't know the correct answer. I know most acoustical foam sold is open cell but most of it is 2" thick or more. I only have about 3/4" to put some material to deaden the outsides of the boxes. Also according to Collo, whose site is hosted here on the Shack, he thinks closed-cell is better. Here's a link: http://www.subwoofer-builder.com/speaker-stuffing.htm

I figure my options were either no foam or closed cell since it is readily available in smaller thicknesses. I would guess that the closed cell has to be better than none...or at least that's the story I'm sticking to. :R

-Tom A.
 
#77 ·
Fired them up!

Well, here they are:

Wilderness Vehicle Regularity rally Car River


Text Technology Electronic device Font Electronics


Yes, I know the logos aren't centered properly...sorry Mike. :whistling: When I was drilling the holes for the mounts, I didn't even think about the logos...They're gonna be behind the black GOM so it's not like they will be seen anyway. :bigsmile:

I don't have any graphs yet, but I did fire them up this weekend. Wow, is an understatement! :bigsmile: I currently have my screen down for the DIY screen rebuild and the projector is currently in the shop for warranty work. Ever since I bought the Optoma H78DC3 last June, it has two "smudges" that can be noticed during dark scenes. Naturally, only I see it, but I figured with all the work going on this would be a good time to have it fixed.

Anyway, I really need the projector back so I can put in Avia or DVD Essentials to run some pink noise for the sub levels. My receiver omits the sub in the DD pink noise setup. Perhaps REW can do this? If so, would my levels be different with REW's analog output to the Yammy receiver vs. the digital bitstream I normally use? Either way, I doubt I will get a true appreciation for the subs until I can throw a 10.5' image up on the screen. I'll try to get some graphs up in the next few days and I guess that will tell me whether or not I need to purchase a BFD.

I do have a question for you guys; I'm feeding the Carvin HD1800 from the line level output on my Yammy receiver to an Art Clean box which converts the unbalanced RCA line output to a balanced XLR output. The Clean box has it's own gain switch and the Carvin has a gain dial for each channel. I currently have the Clean box at about 50% on the itty bitty dial and the Carvin is set to number 10 IIRC. Number 10 is about half on the Carvin dial. Should I set the Clean Box to max and lower the Carvin more or should the Carvin be near max with the Clean Box dialed down more?

Now for a story you insanely large sub owners will appreciate. Since I converted my den to the current dedicated theater room I have never had my speakers rattle anything in the room. They did rattle the hall closet door in the "old den" when it was closed. The hall closet door came off and the hall closet became my audio rack for the dedicated room. Anywho, like I said no rattles until the RLp-18's came to town! :R

One of the last movies I watched before starting this project was Alien 3. Perhaps not the best of the Alien series but during the first minute or two of the film, a large spaceship slowly pans across the screen with a low rumble. This scene really got my Def Tech's in a tizzy. :hush: It was the only time I ever reached for the volume control. Naturally, by the time I got the remote the scene was over. So I knew I had to try this scene again. I set the Yammy to the same volume level as I normally watch movies which according to the Galaxy meter is only about 90-95 dbC. I had the subs set a few db hot as determined by playing a REW sweep from 10Hz to 200Hz and observing the Galaxy meter. Not real precise, but just to give you an idea. Even though I had no projector, it was obvious when the spaceship came across. I heard a much worse rattle than I did with the Def Tech's. :hissyfit: Of course the rattle wasn't from the front of the room but the rear left corner. Wow!! Naturally, I played it again a couple of times and I thought it was my wall rattling but it turned out to be the tin sign that I have screwed to the DIY wood cabinet door that my popcorn machine sits on. Here's the real funny part, after a couple of times doing this my wife runs in the room and says, "What are you doing, you are rattling the windows in the kitchen!". Yes, I had to play it again and check for myself. While I didn't actually hear the windows rattle, I did see the little stone turtles in my wife's nick-nack display case, which as you probably have guessed by now are on the opposite side of the theater/kitchen wall, dance up and down! I was much more impressed than she was. :devil: I tried to get her to walk around the house with me and take a pre RLp-18 crack inventory but she didn't bite...she said all cracks WILL be blamed on the subs! :yikes: Seriously, these things will have to be respected. :bigsmile:

I was about to install the dedicated 15A circuit for the room but decided to just try it as is first. From the little bit of listening I have done, I doubt I will need more. The subs were just laughing at me and hardly moving at all. I can feel them move if I touch each driver but the only time I really saw them move was when I was doing the 10-200Hz sweep. Of course I had to show my wife and she said...."ouch I can feel that even though I can't hear it". I guess they are working fine, huh? :R

I need to spend more time with them trying to get the levels right and doing some FR before I come to any real conclusions but I'm sure they will fit nicely into the mix. When I converted the den to the theater room, I wish I would have put another layer of sheetrock down, oh well....at least I did put some insulation in the theater/kitchen wall although I guess it doesn't stop stuff from rattling in the kitchen.

-Tom A.
 
#81 ·
Re: Fired them up!

I do have a question for you guys; I'm feeding the Carvin HD1800 from the line level output on my Yammy receiver to an Art Clean box which converts the unbalanced RCA line output to a balanced XLR output. The Clean box has it's own gain switch and the Carvin has a gain dial for each channel. I currently have the Clean box at about 50% on the itty bitty dial and the Carvin is set to number 10 IIRC. Number 10 is about half on the Carvin dial. Should I set the Clean Box to max and lower the Carvin more or should the Carvin be near max with the Clean Box dialed down more?
You should take out the Cleanbox, it has a very poor frequency response.

Max out the gain on the Carvin and adjust the output level on your receiver.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top