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Desert Sunset Theater Build - Page 6

post #151 of 1093
well i think the nice thing about andreas leading the way on the rotary build is that he does all the hard engineering work. the rest of us can just order parts from machine shops spec'd out based on his experiments and assemble.

Matt
post #152 of 1093
Quote:
Originally Posted by stockmonkey2000 View Post

I've seen your ported towers and audiovideoholics build which would be essentially an IB with roughly 1-2x vas. That was the reason for my curiosity as to how audiovideoholics build would perform because for IB you want a minimum of 4x vas. If I were to add any additional drivers I would not want to go below that minimum. I also prefer the gradual rolloff of the sealed IB. My prior subs were tuned to 16 hz. I'm not planning on playing these at crazy levels so I should have headroom to EQ for flat response below 10hz. I guess I'll see where I end up after everything is up and running.

well YOU have ME converting mine. I am thinking about cutting my towers down, putting 2 manifolds between my spare room and HT room, and my door will be just like your access panel. I plan on testing with the door sealed shut, sealed IB, and open, 11Hz tune with the 23" x 88" x 4" door way as the port.

I just downloaded all of your awesome pics to show my girlfriend for approval tomorrow. Having taken a closer look, your square access panel appears to be just right for an off the cuff test... once you get comfy and a good feel for your system, Id try it without the panel in place. Only issue though is with 2 of the subs right there, I think they'd cancel out and leak rather than load it as a port....if you could make 2 panels to block the 2 subs...eh... I dont think it would work, and I think you will be more than happy as is!

Again, great work and pics, should help me convince the GF though she knows full well my work wont turn out nice like that
post #153 of 1093
Thread Starter 
Quote:
Originally Posted by kryptonitewhite View Post
well YOU have ME converting mine. I am thinking about cutting my towers down, putting 2 manifolds between my spare room and HT room, and my door will be just like your access panel. I plan on testing with the door sealed shut, sealed IB, and open, 11Hz tune with the 23" x 88" x 4" door way as the port.
At least you would have your room back.

You could probably make a door that is still usable and seals off the backwave but it will take some doing. I'm working out details on my theater door right now.
post #154 of 1093
The door is locked securely shut right now to keep SPL up in the single digits as it is, but i may convert the doorway into a giant port to test IB vs ported IB.
post #155 of 1093
Thread Starter 
Quote:
Originally Posted by kryptonitewhite View Post

The door is locked securely shut right now to keep SPL up in the single digits as it is, but i may convert the doorway into a giant port to test IB vs ported IB.

There is no such thing as a ported IB. That would be like saying a ported sealed box. Once you put the port in, it ceases to be an IB.
post #156 of 1093
I know of one documented IB build, whereby the owner decided to vent the IB at a later date, with a tuned port. Hence the term, ported IB.
post #157 of 1093
Thread Starter 
Yes you can turn an IB into a ported. My only point is that an Infinite Baffle by definition has a rear wave that is in a theoretical infinite space that is totally isolated from the front wave. Once you put in a port to use some of the rear wave it would cease to be an IB and would then be a very large ported subwoofer. Krypto keeps referring to a "Ported IB" when he should be calling it a large ported sub.
post #158 of 1093
As you likely know, within the vented subwoofer type, there are several different variations.

LLT; large low tune
SLLT; super large low tune

An IB, utilizing an attic, crawlspace or similar area as the backspace is typical. However when one designs a tuned port to augment the response (at the expense of all response below tune), a name of ported IB seems appropriate, regardless of technical accuracy in my opinion. When you see it, it's a ported IB. All that said, you're right, it is ported and SLLT is most likely the correct designation.

LLT description. This is an outstanding explanation by guru Steve Callas.

LLT vs. SLLT explanation

The individual that transformed his IB into a SLLT, wanted more impact, feel etc. Oftentimes the IB alignment, is so transparent and clean, that the dramatic reduction in distortion, isn't overwhelming in the short term. The high resolution, transparent nature is more more pleasing over time. Without a peaky response, either inherent or EQ'd in, an IB allows the material throughput to be rendered cleanly, and without un-natural emphasis. This critically damped, low Q response isn't of the "blow you away" variety. However, it doesn't wear thin over time either. Subwoofer subjective terms such as "slam", "impact" etc., are merely descriptors of frequency response characteristics. If the ported IB gave the owner what he desired, that's great. However, below tune, with any vented design, response drops off in a big way, and distortions rise dramatically.

Many contemporary motion picture releases recognize the realism of including infra-sound content down into the low single digits, and this energy helps create a very realistic suspension of disbelief. So if system response down to the 3hz (to cover the LFE specification of 3-120hz), is the desired outcome, even the best vented design can not get you there.

Back OT; I'm looking forward to you integrating and optimizing your IB, and of course your impressions of the IB system.

Good luck
post #159 of 1093
Thread Starter 
I decided against putting the dead vent to exchange air with the rest of the basement in the corner. There will still be a return air vent there. I also realized that I measured something wrong and this corner build-out was bigger than my doorway on the other side of the room. So I decided I would rip it out and drywall this with the rest of the room and put the return air in afterward. This will allow me to use the corner for bass trapping. I should have done it this way to begin with. It would have saved me some trouble.

Before




post #160 of 1093
Thread Starter 
post #161 of 1093
Thread Starter 
Progress has been a bit slow lately. Trying to figure out where all the HVAC is going has taken my time. I do have the outside shell now covered in OSB so it looks like a room now.

Screenwall





Rear Wall

post #162 of 1093
Thread Starter 
I decided it was going to be difficult to hook up to the HVAC supply after the Drywall is in so I went ahead and put in the duct. I'll Cover this with damping material later. I will branch off of this with the AT Core Flex duct from the soundproofing company.



I'll also fill in all the gaps with acoustic caulk.

post #163 of 1093
Thread Starter 
Here is the connection to the return air. I will have one 8 inch return in the left rear corner and a 6 inch return by the door. I kept the one return smaller because this will be in a dead vent in the equipment room. If it turns out to be too small I can increase the size later. I'm hoping the two smaller returns will be sufficient.

I originally cut this return as a 6 inch but am increasing it to 8 inch.



On the left of the door is where the 6 inch return is. Photobucket appears to be having issues so I'll have to update the photo later.
post #164 of 1093
Thread Starter 
Here is the small return by the door.

post #165 of 1093
That first pic, looking forward toward the screenwall,...wonderful. Just a kick ass blank slate from which to continue. I would suggest that you fire up the IB, and check the modal behavior of the room. If you have any main LP placement flexibility, now would be an ideal time to determine where any front to back nulls will reside. It's very likely that you'll have nulls of perhaps 20db or more, at certain distances from the front wall.

Additionally, a side benefit would be determining any subtle buzzes or structure borne vibrations from the IB. Also, I've no idea as to your acoustical savvy, however are you familiar with the 38% rule? Reading this isn't necessary, but looking at the visuals helps a bit. Wes Lachot, studio designer, often writes articles regarding room design, and optimizing acoustic relationships within a space. Also, and much more importantly, is an essential work from Toole is "Getting the Bass Right". It really is a superb piece IMO. I believe I already posted this link before, however in case....

Nice job so far. I know very little wrt HVAC, but it's nice to see progress.


Good luck.
post #166 of 1093
Thread Starter 
I had a discussion with the experts a while back before putting up the walls. I had some flexibility in the length of my theater so I wanted to know if I could avoid problems with my room dimensions. The general consensus is that every room has problems so make the dimensions what you want while avoiding glaring problems like room dimensions at multiples of each other. I did run the room dimensions through the mode calculator at realtraps.com - yes there are modes, but nothing glaring. I'm not sure how it will perform in real life, but I'm sure taking measurements with reflective walls and no treatments, carpet, furniture, concrete floor etc is going to show major problems that will likely be remedied in the future.

I plan to incorporate as much broadband bass trapping as possible. I used superchunk bass traps in each of the corners of my last theater and they provided very good results. I plan to do the same and also incorporate bass trapping where I can in the soffits, behind the screen, and the seating riser.

I do plan to get the subs up and running soon, if nothing just to make sure I do not have any defective drivers. I really hope that is not the case because it may be problematic if Fi does not have parts.
post #167 of 1093
Quote:
Originally Posted by stockmonkey2000 View Post

I'm not sure how it will perform in real life, but I'm sure taking measurements with reflective walls and no treatments, carpet, furniture, concrete floor etc is going to show major problems that will likely be remedied in the future.


My concern would be independent of the impact of any of the items you mentioned. Also, typical super-chunk bass traps aren't ideally suited to address LF anomalies in the octaves I'm referring to (~35-80). Most any room with LF sources along the front wall will have a potential null at some point front-to-back. If you've got flexibility with placement of the primary LP after the fact, this is of no concern now.

The few ways to address these type nulls include distributed sourcing, a Double Bass Array, limp mass membrane or equivalent, ...or flexibility in seating proximity.

Just a thought, nice progress
post #168 of 1093
Thread Starter 
My first row of seating will be about 14' from the screen (on a false wall 2' from the sub baffle wall) This would put seating at 16' from the front wall. the room is 25 wide so this would put the primary listening position (1st row) at 36% of the length from the back wall. I have a bit of flexibility on the front row. I am planning for a 12' wide 2.40:1 scope screen so I'm a bit worried about being too close, but from what I understand it is ok to be a bit closer on a scope screen. I'll have to see how the 12' wide screen fits with my main speakers - I may have to shrink it down a little but will have to play around a bit to be sure. I'll probably have 12' and mask it down later if necessary. That may come in handy if I later decide to have all the speakers behind the screen.
post #169 of 1093
You could help me here. Viewing distances specifically, and the video side of things in general is certainly not my area of interest. However, isn't the 234 formula, whereby;

Optimal viewing distances, x = screen height

2x Closest
3x Optimum
4x Maximum

Are these correct, an the guidelines you're using?


Thanks
post #170 of 1093
Thread Starter 
Quote:
Originally Posted by FOH View Post
You could help me here. Viewing distances specifically, and the video side of things in general is certainly not my area of interest. However, isn't the 234 formula, whereby;

Optimal viewing distances, x = screen height

2x Closest
3x Optimum
4x Maximum

Are these correct, an the guidelines you're using?


Thanks
Never heard of that formula before and not sure how it would hold up for various aspect ratios. I'm basically shooting for a viewing angle of around 40% or so for the first row. That does put me at about 3x the screen height. I got the 40% viewing angle from feedback from Dennis Erksine and other threads.
post #171 of 1093
I thought it was based on ability to resolve individual pixels, but I'm not sure. With greater rez, one can sit closer for greater immersion. I always thought that's what it was based on. There's an ideal distance for any rez, closer and one can delineate pixels, any farther and the additional rez is rendered useless. That said, I'm way out of my wheelhouse,...I was hoping you could school me on this

I know there's a chart on this 234 (my name) rule of thumb. It shows all the different standards, like SMPTE, THX, DOLBY, etc, and illustrates the minimum distances, and most distant seating suggested. If Dennis is on it, I'm sure you're fine. If I stumble across that chart, I'll post it up.

Thanks
post #172 of 1093
Thread Starter 
Didn't get much done over the weekend because I was feeling a bit under the weather. I did get started on the clips and channel for the ceiling.

post #173 of 1093
Cool. Any close up of the clips or a link?
post #174 of 1093
Thread Starter 
I don't have a closeup handy right now but can take one later. My ceiling pic turned out a bit blurry so it's hard to see what is going on. The clips are the whisperclips from the soundproofing company. I took this photo off the website so you can see what they look like.

post #175 of 1093
Thread Starter 
Quote:
Originally Posted by FOH View Post

Cool. Any close up of the clips or a link?

Here are a few close up shots of the clips -





post #176 of 1093
Thread Starter 
I'm about 80% done with the clips and channel. I should finish up tomorrow and then can start on the ceiling.
post #177 of 1093
Nice detail on the clips.
post #178 of 1093
Thread Starter 
Current status on the room.

post #179 of 1093
Thread Starter 
Didn't get much done tonight but did get a bit of the ceiling done.

post #180 of 1093
Thread Starter 
This is the access for the hvac for the floor above.

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