Diamante Build in DC - Page 6
AVS Top Picks
I got a MiniDSP UIMIK-1. This is what they say about it:
- The unique calibration file is available for download from the product page (http://www.minidsp.com/products/acoustic-measurement/umik-1). Once your UMIK-1 in hand, you will be able to read the unique Serial number from the microphone body and enter it in the text box field of the product page.
- Finally, the UMIK1 is compatible with a wide range of acoustic measurement software being a driverless USB Audio Class compliant device. For those of you learning Acoustic measurements, we recommend REW (Room EQ Wizard) freely available at the following link: http://www.hometheatershack.com/roomeq/. Besides being an easy to use and powerful software, REW also includes unique valuable features when combined with the UMIK-1. They include automatic SPL calibration and discovery. Hoping you enjoy it and remember to donate to REW to support their work!
Thanks for your support and Welcome to the miniDSP community!
At this time I have 2 front channel speakers and 2 subwoofers connected. I have to admit that I'm extremely disappointed with the bass response from the 2 JTR Captivators that I have. I'm not sure if it has anything to do with the settings of the bass management or crossovers somewhere but the subs definitely do not give the visceral impact that I would have expected. The room is not that big (perhaps equalized out to 18' x 30' x 7.5' = 4050 cu. ft. volume) but the bass is very thin. The cabinets shake and the cones move in and out,. but unless I'm sitting on the cases there is no visceral impact. And the drivers seem to be bottoming out when it gets loud. I have REW and will measure what is going on shortly.
My next empirical steps at trouble shooting will be to hook in an old M&K sub that I've had for probably 20 years! See if it is possibly the subwoofers themselves that are the problem. Otherwise, I'm going to take the sub amp out of the equation and just use a pair of channels off my main/surround amplifier to get that amplifier and its DSP module out of the equation.
A query and plea to my Maryland and NoVa theater-building comrades. Asking for a little bit of help. I have my fiberoptic starfield ceiling which needs to be mounted as part of my final push towards finishing the theater. It is four 4' x 10' MDF panels that need to be screwed to the ceiling with a few screws. I basically just need a couple of people to help get the panels up onto the ceiling while I screw them up one at a time. I wouldn't think it would take more than about an hour or two of time. I'm hoping to get this done on Saturday -- either at the 11-3 window or after 5. I will provide pizza and beer/soda and you can help me audition and start tuning the sound system consisting of 7 BG Radia planar ribbon speakers and 2 JTR Captivator subwoofers. I will have a REW system set up for measurement but am still trying to figure out how that works. Someone with experience doing REW measurements would also be very much appreciated!
So, is anyone available and willing to give me a hand this Saturday? You can PM me or send me a message at a1certified at gmail dot com.
Some interesting graphs as I started hooking up speakers. Had a problem with thin, tinny bass. Thought I had a defective sub (or subs). When I hooked them up to measure them, this is what I found:
With crossover set at 80 Hz, there was a pretty big dip between 70-80 Hz. I tried playing around with crossover settings to minimize the dip.
But other settings were worse.
Next I worked a little bit with the parametric EQ in my subwoofer amplifier and got to the blue-green line. Overall tamed the little peak around 34 Hz and smoothed out the region between 70-150 Hz. Still a big dip around 110 Hz. but that is well above the crossover frequency so that will have to wait until I start to tune the main speakers.
The interesting thing started when I added the second subwoofer. This was clearly the explanation for my thin, tinny bass when I initially just hooked everything up and pressed "play":
Adding the second sub (green line) resulted in huge dips around 20 Hz and between 40-90 Hz. At first I thought it might just be a defective sub, but then I thought that maybe there was a phase issue with cancellation and before doing anything radical like pick up this 100 pound subwoofer and put it in a box and put a shipping label on it, I switched the phase of Sub #2. Lo and behold:
The purple line is the result of this measurement. Dips are gone and now I have a new peak between 20-35 Hz.! It was something that simple. I haven't gone back yet to figure out if it was just a wiring error on my part. That is my assumption. But it is always possible that the sub was wired "backwards" internally as well. I will investigate later when I feel like moving those subs around again! You can also appreciate the + 6dB gain in SPL that is expected with the additional sub.
It a little bit of EQ, I moved from the purple line to the burgundy line and have quite a bit smoother response throughout the bass range.
Now, the bass sounds full and musical. With a little boost in amplifier power, you really start to get that punch in the gut feeling from the subs which was entirely absent when I first hooked them up and pressed "play".
Next, the full range speakers.....
I wanted to baseline test of the raw room before any treatments. I went ahead and did a preliminary optimization of the subwoofers since I don't anticipate that they'd be significantly affected by the treatments I have in the room. Based on the waterfall graph, however, it looks like I have relatively little work to be done as far as bass trapping. I was a bit surprised by this. I'm hoping that adding "stuff" into the room helps a little bit, but will solicit opinions on whether some bass traps in my front corners might help?
It looks like I have some ringing at 70 Hz, and 30-40 Hz. I don't I am going to have the energy or resources to try to do anything with the sub 20 Hz stuff.
How low down does the effectiveness of 1" and 2" Linacoustic go to? Clearly there is more ringing above 150 Hz., but that is presumably due to the main speakers and not the subs. As you infer, no sense going crazy with that stuff until I start getting some treatments up around the room. At least I have a baseline to compare to.
The starfield ceiling is still on the ground. I only had two people free yesterday and we did some preliminary work on getting the panels prepared for mounting but didn't have enough hands to actually get them up on the ceiling. Am trying to round up some troops for later this afternoon.
Edited by RossoDiamante - 10/20/13 at 10:06am
- 1,407 Posts. Joined 11/2004
- Location: Silver Spring, MD
- Thumbs Up: 54
- Select All Posts By This User
- 1,756 Posts. Joined 11/2006
- Location: Kansas City
- Thumbs Up: 30
- Select All Posts By This User
After a bit of a hiatus just fiddling, I made some progress tonight. Linacoustic has gone up behind the screen wall. And post Linacoustic measurements show a definite improvement, but a long ways go to. The main problem I've been hearing is uncontrolled reverberation in the midrange and upper frequencies. Makes the sound quite harsh. This was confirmed with RT60 measurements in the 0.9s range. The Linacoustic behind the screen wall made a definite improvement down to the 0.7s range. Still a ways to go until the target of 0.3s.
Baseline in gold, post-Linacoustic in blue
The most gratifying measured change is the significant drop in the RT60. The room's bare drywall lend it an extremely reverberant character. Even this little bit of Linacoustic made a big measured difference in both the amplitude and the shape of the RT60 curve.
The most surprising measured change is the ever so slight improvement in the waterfall decay in the sub-50 Hz. region. I wouldn't have thought simple Linacoustic would have any effect that these low frequencies. Just an extra bonus, I guess.
It was a lot more difficult than I anticipated, but I finally got the starfield ceiling installed. If I had known how difficult this process would have been (let alone how expensive it is), I would have seriously considered skipping it altogether. But now that it is up, I do think that it is a tremendous addition to the atmosphere of the theater. I only question whether it is TOO bright. I only discovered when I read the installation instructions for the illuminator last night that it is not a dimmable system! I was assuming I'd be able to dim it with the Grafik Eye. Once I get black carpet and black on the walls, I hope that it mutes the reflected light enough for it not to be a problem. I will put a call into the manufacturer to see if there are any other options.
The panels still need to be cleaned up, but it is really nice with the lights out. Now I just have to repair the drywall that resulted from the installation of the panels. Then repaint the soffit and then it is time for the trim to be installed. I will also be putting up my baffle wall now that the everything is installed behind the screen wall.
It is from an outfit called FOSI (http://www.fosi.com/). I think they are out of Jersey. It is a premium product with premium support. And a premium price tag unfortunately. I definitely underestimated how difficult it is to hoist up a 4' x 10' panel. I considered a drywall lift, but thought that it might damage the fibers.
This was my equivalent to 2 tons of sandbags....
Speaking of which, I don't seem to have any resonance issues or low frequency reproduction problems so far. I'm debating whether or not I should just open up my riser which is about 4' x' 18' x 1.5' filled with fiberglass and see what it does to the prolonged decay time at around 18 Hz. Since this is technically below the audible range, I don't know if I should bother trying to tune it out. The other area that could use a bit of help is in the 70-150 Hz. range, but I'm hopeful that some corner bass traps behind the screen wall will help with that.
FOSI already uses different levels of tint inside to create the perception of different star distances. Much easier to get the dimming option on the unit. Hopefully it's just a bulb swap and nothing further....hopefully.
Yes, I assume so. There is already a neutral density filter or some such there.
First, I will get the rest of the "dark stuff" in there and see if the natural absorption of the room brings down the light intensity. If it is problematic, I believe I already have the solution.
I spoke with Cyr at FOSI and he told me that the reason the illuminator cannot be on a dimmer is because of the wheel motor and not the light bulb. They currently run off the same power connection. I can open up the illuminator and split the two power leads (one for the motor, one for the bulb), put a dedicated power cord on for the motor and then hook that to a non-dimmed power outlet. Then hook the bulb's power supply to the dimmed circuit attached through the Grafik Eye. I will double check with Lutron to see if I need to do anything special to dim that bulb. I'll probably just do this anyways, now that I think about it, before I close up the screen wall area.
I'm not sure if you've seen the Desert Sunset build, but SM2K's fiber optic star installation starts here: http://www.avsforum.com/t/1314492/desert-sunset-theater-build/330 Not sure if you got the shooting star option, but he had an ingenious little mod to have the star shoot every 15 minutes instead of every minute.
I was starting to construct my baffle wall now that everything behind the screen wall is installed.
So I come down this morning and take a look at what I've done so far:
And I thought of two things.
First, I forgot to leave "holes" in the wall for me to try to use the space behind the baffle wall as a bass trap of sorts. This first question has 2 parts. A) Is it reasonable to believe that a bunch of fiberglass behind the baffle wall might be able to act as a bass trap? Based on the latest waterfall graph, it appears that I could use some help at 40 Hz and between 65-120 Hz. There appears to be more of a decay issue in the upper bass (65-400 Hz) range some of which I'm assuming will get better as I add more Linacoustic on the side and back walls. B) If it is reasonable to believe that I could have an effective bass trap there, does my baffle wall construction (studs - 1/2 plywood - GG - 1/2" drywall - possibly another GG/drywall layer - 2" Linacoustic) pose any sort of impediment to the bass interacting productively with the bass trap behind it if I do not leave "holes" (i.e. an 18" x 18" cutout) in the baffle wall? I'm concerned that with multiple "holes" in the baffle that the integrity of the baffle will be significantly compromised as there is relatively little space around the L/C/R speakers as it is for a continuous baffle. The most reasonable solution I can think of at this time is to make a 6-9" "slot" open at the bottom of the wall.
Second, am I wasting my material and money having Linacoustic behind the baffle wall? I'm assuming that the Linacoustic I'm going to be putting on the front side of the baffle wall will do the same job as the Linacoustic that is currently behind the baffle wall. Between the fact that that there is Linacoustic on the front of the baffle wall and the understanding that higher wavelength frequencies at which the Linacoustic is effective are more effectively blocked by the wall itself, will any of those frequencies actually make it "back there"? Plus, in order for it to make any difference to the sound in the theater itself, it's going to have to reflect off the back wall and go back through the 2" Linacoustic on the front of the baffle wall again before getting into the theater space proper. I'd think that it would be significantly attenuated by that time. I can also put some pink fluffy in the stud spaces on the back of the baffle wall.
A third question now that I have your attention. I have the option of substituting the 2" Linacoustic for a 1" Linacoustic - 3 mil poly - 1" Linacoustic assembly. I have read that the poly helps the Linacoustic act more as a "membrane absorber" with the understanding that somewhat lower frequencies can be absorbed. With a setup like mine where there are going to be many little penetrations (the 3 speakers and the 2 subs) that would preclude being able to have a big sheet of Linacoustic and poly, is this configuration still effective? I'm assuming that the poly sheet should be continuous and not cut up into many pieces to fit in the space like a jigsaw puzzle?
Thanks for your thoughts.
The only confident answer I have for you is that the space behind the wall should have the cheapest insulation in it. Linacoustic back there offers no improvement and is wasted.
That doesn't guarantee that the insulation back there is trapping bass, but it should be there.
That's the conclusion I was arriving at as well. I will strip that off except at the bottom where I will leave a little "slot". I think that would be the least disruptive hack against the various benefits of a baffle wall.
I'm sort of remembering a conversation I had with my speaker manufacturer that said that the speaker, without a baffle wall, would have a peak at either 2500 Hz or 3500 Hz. Interestingly, I don't see that evident in the measurements I've done to date. I will run another set of measurements once I get the rest of my baffle wall up.
The baffle wall complete. Now includes 24" of fiberglass insulation behind the wall. Seems to have improved the acoustics by measurement, but I'm suspicious of how. I will have to re-measure to make myself believe what I saw on the first run through the measurements once the wall was up.
Also starting to clean up the rack.