Negatron II

Discussion in 'Listening Room / Home Theater Build Projects' started by Negatron, May 15, 2017.

  1. Negatron

    Negatron Senior Member
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    Thank you. I have to run an AT screen that is retractable in this room...I had hoped to go to a 200" 2.4 AT retractable, but SeymourAV doesn't make one that large, and the I largest one is max budget already. If I am lucky I will have about 6k to spend total. My last HT was a bat cave, and the 195" 2.4 diagonal worked out great, but we cannot use a fixed screen or In would try it again.

    The ones you linked are fixed screen, and would take 100% of my budget. If i was still working the ones you suggested would work, but not on my retirement check.

    I was hoping the 4k Laser hybrid projectors would have come down more so I could afford one. I am thinking around 3k for a screen, and about the same for a projector. Maybe I can find a used screen to save me some money. The shipping is going to be a killer to Mexico, plus 17% duty unless I bring it myself across the border (then it would be free).
     
  2. Matthew J Poes

    Matthew J Poes Staff Writer
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    Ok I forgot you were looking to do such a big screen. That is a REALLY big screen for a home theater and will place limits on what options you have. It would be more than $6000 for the screen.

    Retractable is also tough for this, the best AT materials are not self-supporting or self-tensioning and thus don't work well with retractable systems.
     
  3. Negatron

    Negatron Senior Member
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    The SeymourAV screen is AT, and self tensioning, but I can only get a max of 160" 2.4 screen. that is why I am only going with a 160" screen.
     
  4. Negatron

    Negatron Senior Member
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    I was going to use my 195" screen, and have it retract up the wall, but there are 2 problems..
    !: it would not look good sitting there above the speakers.
    2: it would have to sit almost 4' off the floor as it would have to be above the speakers.
     
  5. Matthew J Poes

    Matthew J Poes Staff Writer
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    Seymour AV has two materials they offer. The XD is self-tensioning and the UF is not. The XD is the older woven type that I mentioned not liking as much. The UF is not self-tensioning, it is more like spandex, but has a smoother look. The XD can cause a moire effect if the grid pattern of the pixels aligns or even slightly aligns with the grid of the material. Seymour AV addressed this by tilting the weave, but that can't be done on the size you want, and....doesn't fix the problem with 4k projectors (nor really fix the problem with 1080p all that well). The UF doesn't have the problem at all. It's also far more acoustically transparent, being more like good speaker cloth.

    I did a contract job a number of years ago testing a number of screen material types for acoustic transparency. The tests were done inside a tiny anechoic chamber that I was loaned for the project. The tests involved a small full range speaker source with a screen material placed .25", .5", 1", and 2" from the source inside the small chamber. It was tested from 300hz to 20khz and is anechoic down to about 800hz, but has a correction file for the response below that. As such, it gives you basically anechoic results down to 20hz (if you like). I was asked to characterize the materials and I found a lot of problems with the course weave fabrics I was sent. This included added non-linear distortion, diffraction, comb filtering, attenuation, and response spikes at the very high frequencies that only showed up sporadically, but only when testing with the material. After 100's of tests, they never showed up unless one of the course materials was in place. While I did find (and generally believe) that this woven material is an improvement over the old perforated vinyl material, it is not acoustically transparent. In fact, technically no material was acoustically transparent, but the materials most like UF were very close. I tested some manufactured materials and various kinds of Spandex. These materials attenuate the sound and cause very slight variation in response, but they actually attenuate higher order distortion by absorbing it at a higher rate than the fundamental, and generally just cause a benign attenuation of HF's. It's as good as it gets at this point.

    https://avscience.com/2015/11/dreamscreen-ultrahd-acoustically-transparent-screens/
    This is a cool new AT material that I've tested a sample of. I don't think its available in a retractable form, but you could always inquire. The material is foreign, so it's possible you could import it to Mexico more easily through the manufacturer rather than AVScience. In any case, that material was the best acoustically and visually that I saw. I would have used it, but it was many times more expensive than what I have. I decided not to spend the money.
     
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  6. Negatron

    Negatron Senior Member
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    Interesting... I have a 195" 2.4 XD that was cut tilted when i purchased the fabric, and I had zero problems with the screen.Maybe I got lucky? I wish I could find someone that made the retractable minus the screen material...otherwise i will have to figure out an acceptable way to mount my fixed 195" screen and retract it if I can not find an acceptable retractable screen.
     
    #106 Negatron, Jun 12, 2018
    Last edited: Jun 12, 2018
  7. Negatron

    Negatron Senior Member
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    If I am able to reuse my screen it def leaves more money for a new projector. I could fly up to see Craig, and bring the projector back on the plane for less than what shipping and Duty would be.
     
  8. Negatron

    Negatron Senior Member
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    I think I have an idea that will work... I put up a set of light blocking curtains, and then...
    1: I take my old screen, build a new frame, cover the back of the screen with black blackout cloth (use the screen as a normal screen not as a AT screen), and mount 2 rails with linear slide bearings to the wall above the windows. This will be electrically lowered.

    2: I then make a 2nd set of curtains to match the first set, and install them to conceal the screen.

    The only problem I see is that the screen can only come down to the the tops of the front channel speakers unless I eliminate the center channel speaker. The speakers are about 3' tall unless I mount them the way they normally go...then they are about 2' tall, and would need to be angled upward.


    What do you think?
     
    #107 Negatron, Jun 13, 2018
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  9. Negatron

    Negatron Senior Member
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    Tonight we went to a small theater, and the screen was above our line of site, and it was ok, but was not a good as when the screen is lower. What made it seem not as good was that the speakers were below the screen instead of behind the screen.
     
  10. Negatron

    Negatron Senior Member
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    I might have a solution... my room is 19' wide, and my old screen is 15' wide, so it means I have 2' per side of space. If I can make a wall mount 3' out from each wall I can run a track on each side To run the screen frame in. Then I need to figure out how to have it go up, and down easily...preferably electric.
     
    #109 Negatron, Jun 17, 2018
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  11. Negatron

    Negatron Senior Member
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    What would be a safe distance to run from the turntable to the phono stage? The phono stage has about 3' of cable to go to the preamp too.
     
  12. Negatron

    Negatron Senior Member
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    Just got word...final walk through this week, and we close on Monday.
     
  13. Negatron

    Negatron Senior Member
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    Looks like I will have some changes as the wife wants to have mirrors on the wall on the loft for her to practice dancing. This means I will no longer have 10' for the audio rack, but maybe 4' max, and still only a little over 2' high. The speakers will still be next to the windows but the doors will not be used behind the speakers (a plus for me), only the glass door to the left will be used. Room darkening curtains will be used, but not black, and a couple of carpets will be used for the floor too...again not black, but grey or blue with some white stripes (best compromise I could get as we will be getting the, from Costco).

    On a 19' wide room, I will have to leave about 3' per side since we will be using the door which opens inward on the left, and we have the fireplace on the right. Not as much as I had wanted. Should I skip The center channel?

    The old JBL speakers which are angled at 45 degrees as I recall will be set up as height channels, and as Auro3d channels. How do I calculate the height of them?

    Would it be best to run side surrounds or rear surrounds, With the heights above them?
     
  14. Negatron

    Negatron Senior Member
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    After talking with my wife...she said I can use the loft wall side which is 19' long instead of the 10' long wall! This means we do not need to install a railing to prevent people from falling as the will not be able to get any closer than 2' from the wall. I love my wife!

    Now I have to decide how to make the rack, as I cannot use that much space without using it for bluray space, and I do not want my whole collection in view. If I box it in it will awkward as the loft top has about a 6" top of Cantera tile... I do not want to have it removed, and have new 2' tiles in its place as it will be a mess.

    To take as little space as possible from her dance floor if it is boxed in...could I vent frontward? Or would it look better to have a open rack design for the equipment, and cabinets on the sides? Cabinets would be faux white like the kitchen cabinets.
     
  15. Negatron

    Negatron Senior Member
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    Update...my wife has given me the whole 19' wall against the balcony. I am going go make the t channel rack in the middle of the wall, and then have some white washed cabinets for the remaining wall area. I had thought about having a 3' x 15" x 15" sub on each end of the loft, but I am not sure it would be any good being above our heads...any ideas?
     
  16. Negatron

    Negatron Senior Member
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    Screenshot_20180711-090634.jpg Screenshot_20180711-085847.jpg Screenshot_20180711-084208.jpgView attachment 8850View attachment 8849View attachment 8849 I am getting a little confused on setting up my height speakers for Auro3d... it says I should have a 30 degree angle (calculated from a standing position)for the mounts, and then aim them at the mlp with a 28-48 degree angle. My JBLs are @ a 20 degree when mounted with the flush mount brackets. With a 19' wide room... how high would I wall mount the speakers, and then how much do I need to change the speaker angle on the brackets...or do I even need to change the speaker bracket angels? I am sorry, but I know zero about Trigonometry which is what I am reading you need to know to calculate this. I will be drilling into our clay walls, and want to get this right the first time. I will not be doing a center height channel(not recommended, but I would like to, or a top (voice of God channel)).
     
    #115 Negatron, Jul 11, 2018
    Last edited: Jul 11, 2018
  17. Negatron

    Negatron Senior Member
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    I did a quick measurement by eye with a makeshift support, protector, and laser, and it looks like the surrounds(bottom of speakers) will be right up against the bottom of the loft.They will have to be angled left to right in the corners, and also the angle up and down might have to be changed...unless I get lucky or do not adhere 100% to the specs. The front heights will be easier as they will mount right above the windows just like I had hoped.

    I am thinking maybe I can make a wooden triangle, and then attach a turnbuckle to it for the top, and bottom to adjust the angles. Does that sound like a good way or do you think it will vibrate loose?
     
    #116 Negatron, Jul 11, 2018
    Last edited: Jul 11, 2018
  18. Matthew J Poes

    Matthew J Poes Staff Writer
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    I don’t see any reason it would vibrate loose. Maybe make sure your anchor points use course screw threads, glue, and/or bolts with lock washers. Take extra steps to prevent it.
     
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  19. Negatron

    Negatron Senior Member
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    So should I use washers, and extra nuts (and/or locktite) so the adjustments do not change on the turnbuckle too?
     
    #118 Negatron, Jul 11, 2018
    Last edited: Jul 11, 2018
  20. Negatron

    Negatron Senior Member
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    I also have a bit of a dilemma as to how close I get to the Auro3d specs. They are for 30 degrees for each front channel from mlp...if I do that it would put my front speakers in each corner angled toward the mlp. The problems are...
    1: The speakers will be outside of the edge of the screen partially.
    2: We were thinking of running the tracks to raise the screen in the corners, and surrounding them with the bass traps, which could be a problem due to the 4' high x 2' wide x 30" deep horns if They are in the corners. Then again it may be easier... I am not sure as the fireplace is 8' 11" from the wall behind the speakers, and sticks out 2'10" from the side wall.
    3: Then there is the problem as to how to make the first reflection panels if the speakers are angled out in the corners vs being 3' from the side walls, and angeled just a bit.

    The horns are K402 horns which will be mounted vertically not horizontally which will give a 60 degree vertical dispersion versus horizontally which would give a 90 degree dispersion. I can go either way. If they are installed vertically I only need to angle them upward a bit in the front where as if I install them horizontally they would need to be installed on 2' high stands which also makes them much harder to conceal if we continue with the idea of concealing them.

    Suggestions?
     
    #119 Negatron, Jul 11, 2018
    Last edited: Jul 11, 2018

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