Dual RL-p18 LLT begun

[tjambro]

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:



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:



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!



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



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



-Tom A.

[collo]

Lookin' good!

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

[Bob_99]

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.

[Rodny Alvarez]

Good job Tom!!

Are you covering the box with some sort of material??
If you going to paint the box dont forget to use some primer first (the MDF will soak the paint)
I agree with Collo, you need to cut the foam!
Can't wait to see some FRs!!

[SteveCallas]

You will definitely be in for a treat when you fire them up Nice work.

[tjambro]

collo wrote:

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

Rodny Alvarez wrote:

I agree with Collo, you need to cut the foam!

Ok, the pros have spoken I will attempt to cut the foam.

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.

[tjambro]

Bob_99 wrote:

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.

-Tom A.

[tjambro]

Rodny Alvarez wrote:

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.

-Tom A.

[tjambro]

SteveCallas wrote:

You will definitely be in for a treat when you fire them up Nice work.

Thanks Steve. They may not be pretty but I hope they sound good. If not, I'm sure you guys will steer me in the right direction.

I printed out the REW manual tonite and hope to get a FR of my current setup before performing surgery behind my screen to make room for the 2 itty bitty boxes.

-Tom A.

[Rodny Alvarez]

tjambro wrote:

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?

About one inch!

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

[tjambro]

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.



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.

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:



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:



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.

[Blaser]

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

[brucek]

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.









brucek

[tjambro]

brucek wrote:

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.



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

...brucek and blaser... Thanks for the help, I do appreciate it! Hopefully, I can remember enough of this so that I can post graphs of the RLp-18's under the same conditions.

-Tom A.

[Blaser]

Can't waid to see the Graphs tjambro

[Scott S]

Same here!

[tjambro]

blaser wrote:

Can't waid to see the Graphs tjambro

Scott S wrote:

Same here!

Sorry, no graphs yet but hopefully this weekend or perhaps the next. 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.

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

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:



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



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



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



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


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


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

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!

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! 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. The 2x4's and the steel struts will be painted black so that they can't be seen behind the perforated screen.

-Tom A.

[Rodny Alvarez]

That's going to rock your house!!!

[tjambro]

Rodny Alvarez wrote:

That's going to rock your house!!!

Probably not as much as 2 SLLT's with 2 RL-p15's EACH!

-Tom A.

[Blaser]

tjambro wrote:

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.

Will you put the 5/8" closed cell foam on the front and outside sides of the boxes? Why?

Blaser

[Blaser]

tjambro wrote:

Probably not as much as 2 SLLT's with 2 RL-p15's EACH!

-Tom A.

Probably as much

[tjambro]

blaser wrote:

Will you put the 5/8" closed cell foam on the front and outside sides of the boxes? Why?

The boxes are going behind my perforated screen. The black fabric below my screen is acoustically transparent also. So basically the entire front screen wall is acoustically transparent. The idea is that any sound reflected off the ceiling, floor or walls that makes it back behind the screen material should try to be dampened so that it doesn't bounce off the walls behind the screen and go back through the screen to the viewing area. This helps the sound from becoming muddy. I currently have 1" insulation on all the walls behind my screen so I thought I would try to dampen the boxes also so that's the reason for the closed cell foam. I hope I explained that well enough.

-Tom A.

[Owen Bartley]

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.

[tjambro]

Owen Bartley wrote:

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. 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.

-Tom A.

[brandonnash]

MORE PICS AND GRAPHS PICS AND GRAPHS!!!!!

Really good thread.