Dual RL-p18 LLT begun

[Sonnie]

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

You are fine! Looking like it's coming together for you too! I'm eager to hear what you thing about them, as I'm sure most all of us are...

[tjambro]

Well, here they are:





Yes, I know the logos aren't centered properly...sorry Mike. 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.

I don't have any graphs yet, but I did fire them up this weekend. Wow, is an understatement! 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!

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. 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. 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. 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! Seriously, these things will have to be respected.

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?

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.

[Sonnie]

Congrats on getting them installed... Sounds like you will be enjoying them in a large way. I'm sure someone will know about the levels for the Clean Box and amp.

I like that avatar... gives new meaning to the DIY subwoofer headshots.

[tjambro]

Sonnie wrote:

I like that avatar... gives new meaning to the DIY subwoofer headshots.

I figure if your buddy Rodny can sit in his sub, so can I.

Rodny's the President of the SIYS Club:

http://www.hometheatershack.com/foru...html#post33148

-Tom A.

[SteveCallas]

The Carvin HD1800 has high sensitivity for a pro amp, 1V. I'd take the CleanBox out of the loop, you don't need it.

[Ilkka]

tjambro wrote:

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.

[tjambro]

SteveCallas wrote:

The Carvin HD1800 has high sensitivity for a pro amp, 1V. I'd take the CleanBox out of the loop, you don't need it.

Ilkka wrote:

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.

Thanks guys! Should I just buy the RCA to XLR converters at Rat Shack or is there something better I should use?

-Tom A.

[Ilkka]

tjambro wrote:

Thanks guys! Should I just buy the RCA to XLR converters at Rat Shack or is there something better I should use?

-Tom A.

Those or RCA to 1/4" jack converters.

[SteveCallas]

Yeah, RCA to 1/4" would be cheaper and that's what I use. You may need a cheater plug as well going this route, I did.

[Owen Bartley]

Tom, if you're in the mood for another project, you can make a nice adapter cable! (link in sig)

[Sidi_UC]

Nice project sir. Gave me alot of ideas for what I might be gettting into this summer. I've been considering doing a LLT sono tube with the RLP18. Heheh. and furthermore:




hehehehe

[tjambro]

Well Sidi_UC, I hope AsianCat approves of the following plots.

My listening position is about 13-14 feet from the subs and the SPL meter is just behind my primary seating position at about ear level. My Yammy receiver's XO is 90Hz. I have no BFD at this point. I removed the Clean Box as recommended.

Here's the most important plot, the listening position:



Should I be concerned with the dip at 60Hz?

Just in case I cut off the plot at the wrong point, here it is again with the unbelievable lower frequencies shown:




Here's a near field plot. I placed the SPL meter about 12" from the right sub:



It appears that the subs have no trouble with 60Hz, but my room does. Thoughts?

Same plot with the lower unbelievable frequencies shown:



Here is a plot with the SPL meter about 8" from the right hand sub's port:




..and of course the same plot with unbelievably low frequencies:



Am I correct thinking that my "real world" tune is about 13Hz??


I have played with the subs a little, mostly with music as I cannot watch movies yet because my screen is still down...I hope to finish that up this weekend or the next at the latest and my projector is still off for repair. I sent it in under warranty to have what appeared to be two smudges during dark scenes removed. First they told me they couldn't duplicate the problem but then they had the "head service tech" look at it and he determined the DMD chip was bad. I was glad that they found the problem but of course they (Optoma) doesn't stock the TI chips because "they never go bad"....hmm...oh well that just gives me more time to procrastinate on the screen. Once I get the projector back, I'll live with it for a little while and attack the rattles that I get in the kitchen. I think the pictures on the kitchen wall (shared with theater wall) will have to be velcroed to the wall.

So, do you guys think a BFD could help me?

I want to thank everyone for their input and coercing me to press on with this, my first DIY sub/speaker project. I will probably build some new L,C,R's next.


-Tom A.

[Blaser]

Congratulations dude!!

your FR is marvellous, the Dip is not too much of a concern for me. If you want to do something about it, I would suggest either boosting 3-4 db at that Dip, or using a nice Housecurve would to reduce it, or maybe a combination of both!! You would need a BFD then!

But I think that even witout doing anything, that Dip will not be so noticeable.

You cannot know exactly the tune with FRs at listening position, but a nearfield (very close to the woofer) sweep would inform better about the tune. for ex. the sweep at 12" from the right woofer shows approx. the tune. But I would even go closer to the woofer to minimize room interction.

What was the initial design tune?

B Rgds

[tjambro]

blaser wrote:

What was the initial design tune?

Well, originally I was wanting to go about 13-13.5Hz with 600L effective for each box but I scaled that back to 550L effective with a tune of 14.65Hz according to Unibox. If my natural tune is 13Hz, I could live with that.

BTW, I'll be following your massive project.

-Tom A.

[WillyD]

I think Blaser is correct about the near field driver FR showing the tune. The peak output of the port will actually be a couple of Hz below the tuning frequency, so it looks like you hit your target of ~14.5 pretty well.

Looks like a smashing success either way!

[Blaser]

Hey! Do you know/guess how much each of these monsters weigh? How did you move them

[tjambro]

blaser wrote:

Hey! Do you know/guess how much each of these monsters weigh? How did you move them

I would guess each box weighs about 250-300 lbs without the driver. I can tell you I should have got help but I struggled by myself. I had a couple of small rollers that I slid the boxes on to get them in the house. I couldn't lift them over my screen wall but I could tip one end at a time.

To view my struggles, see post 67: http://www.hometheatershack.com/foru...html#post34883

-Tom A.

[SteveCallas]

The response at the listening position, is that with the mains in the loop or no? I'd make sure to test with the mains in the loop and experimenting with different distance values in the processor before even considering a BFD, as that may make the dip at 60hz go away by itself. You'll also want to play around with opening and closing various doors.

[Rodny Alvarez]

Nice job!!

[tjambro]

SteveCallas wrote:

The response at the listening position, is that with the mains in the loop or no?

My original intention was to test just the sub by shutting the front speakers off at the Yammy receiver but I forgot to do so. I re-did one of the sweeps but I didn't notice a change. The Yammy receiver has an "A" and "B" speaker on/off switch but perhaps you cannot shut both speakers off at once? Or, maybe if both are switched off, everything is passed thru the sub? I didn't really spend much time with it, I guess if I wanted to get a true sub only plot, I would have to disconnect the front's at the terminals.

I'd make sure to test with the mains in the loop and experimenting with different distance values in the processor before even considering a BFD, as that may make the dip at 60hz go away by itself.

Good tip, thanks. I'll have to try that. I am currently on hold as I am still awaiting the return of my projector and believe it or not, I still don't have my screen totally rebuilt and up yet. It's a little hard to get motivated when I have no projector to throw images anyway. The metal frame is all done, the screen wall has been tweaked to accommodate the new frame and I have removed the screen material from the old frame and put velcro on it. I just need to put the mating velcro on the metal frame and pull it tight, and re-pull it to I am happy. Then I need to get a buddy to help me set the completed screen frame in the screen wall. I was able to lift the old wood frame in by myself but don't think I will attempt to do the same with the new much heavier metal frame.

You'll also want to play around with opening and closing various doors.

Nope, can't do that, light would enter into the dark abyss. The room is a dedicated theater room with one entrance and no windows. The fire marshal might not approve but it makes for very good movie watching. 12 noon looks just like 12 pm.

-Tom A.

[Sonnie]

Superb job Tom... absolutely superb!

[thxgoon]

I just stumbled upon this thread. Awesome job man! Those frequency response plots are rediculous, wow! Did you post a build thread of your beautiful home theater anywhere? I really like the materials you used on your walls.

[tjambro]

thxgoon wrote:

I just stumbled upon this thread. Awesome job man! Those frequency response plots are rediculous, wow! Did you post a build thread of your beautiful home theater anywhere? I really like the materials you used on your walls.

Thanks thxgoon. I had a build thread over at AVS but it is over 3 yrs. old and I cannot find it anymore. I have some gallery photos of the build over at AVS if you would like to look at them. My user name is the same as here, tjambro. The material on the walls is GOM (Guilford of Maine). It is a sonically transparent fire resistant fabric. I am very happy with it. I have 1" thick insulation behind the fabric from the chair rail down to the floor. Above the chair rail is polyester batting. This has improved the acoustics in my room and I would definitely do it again.

-Tom A.

[Avus_M3]

SteveCallas wrote:

Yeah, RCA to 1/4" would be cheaper and that's what I use. You may need a cheater plug as well going this route, I did.

Is there any issues that could arise from running a cheater plug?

Jesus...that had to be something running down to 2hz? House still together? I imagine you have to be pretty careful running those extreme low freqs?

[tjambro]

Avus_M3 wrote:

Is there any issues that could arise from running a cheater plug?

The biggest issue is that you are bypassing the plug's third prong and are no longer properly grounding the amp. You could use the short ground wire from the cheater plug to make a proper ground. I have not done this, I am simply using the cheater plug. I know this is not the optimal solution but I'm too lazy to go any further with it.

Avus_M3 wrote:

Jesus...that had to be something running down to 2hz? House still together? I imagine you have to be pretty careful running those extreme low freqs?

It really doesn't run down to 2hz, it's more like 8hz or so, look at my first graph at the listening position. You can see the drop in output below 13hz. Having said that, yes I still have to be careful because I could tear parts of the house apart. If i would have known what I know now 3 years ago I would have built the room much sturdier when I did my theater renovation. I just have single wall construction with a single layer of sheet rock. If I was to re-do the room, I would either go with double wall stagered construction (extreme) or at least double or triple layer sheetrock with acoustical caulking.

While I can shake and rattle objects in the bedroom which is at the other end of the house, the kitchen is worst as it borders the theater. I have had to velcro the photos on the kitchen side of the wall because they nearly jump off the nails. But I would never go without my subs, they really do add impact to the experience!

-Tom A.