NXT.......rubbish??....THINK AGAIN!

bobloblob · « **Reply #100 on:** 27 Sep 2009, 04:09 pm »

Hi,
Good answer. I didn't think of the Saran Wrap as complex, though. Just unrolling it and laying it against the Gatorfoam a couple of inches in on both sides, top, and bottom - it clings without glue - mounting it to a frame, then using a hair dryer to tighten up the Saran. I don't think it should dampen the panels, but maybe. This would leave the panels freer to move, rather than fixed at the points where the sticky foam dots are holding it. However, the success of your method speaks for itself.

Each of your panels then is sitting slightly above a frame they are fixed to at several points, a frame whose opening is slightly smaller than the panel?

I like the description of the sound qualities of this speaker you are developing so much that this will derail a future speaker project. I've had tightly-imaging speakers in the past and, apparently unlike most listeners, I find that sort of imaging annoying and unreal. The instruments in a quartet each coming from a softball-sized area...where does that happen in real life?

HenryPercy · « **Reply #101 on:** 28 Sep 2009, 06:15 am »

Quote from: zygadr on 27 Sep 2009, 01:36 pm

The way I see it is that mounting the panels with small foam squares in the corners and 2 on the sides is all that is needed. This works and works well.......very simple, very cheap...and most importantly, does NOT affect or over dampen the panel's resonance at bass frequencies.

With ''voice coil creep'' (voice coil misaligning itself due to the weight of magnet), I have had my panels in the same position for many months now and there has been no audible effects of this.

However, you can see a slight tilt from 90 degrees from the vertical.

Answer...........very simple.........make a panel frame that can be turned upside down twice a year or so. Design it so that the feet of the panel can be removed and mounted at either the top or bottom of the frame

Like I've said though........I am yet to hear any negative sonic degradation to this problem if it will ever occur.

I say go for anything that you think will work. But make it reversible should something go wrong.

We are dealing with an unusual technology here, so going to any complexity may be going in the wrong direction - a mistake that has been made by many high end designers in the past.
Let's not forget that

Sorry, but I've lost track. Are your exciters mounted on a spline, or are they free floating with the panel?

bobloblob · « **Reply #102 on:** 29 Sep 2009, 05:30 pm »

Okay, so here?s what I?m thinking:

Gatorfoam comes in 8' x 4' sheets here. I could make two panels 8' x 2' out of one panel then. To go wider, I'd need to use two panels. Pricey, but not so bad as in Perth. Any thoughts on whether wider would be better? I'm strapped for cash at the moment, but that shouldn't be a problem at all in about six months, when I will have the cash and the space, so if wider is better, I could go for it then. I'm thinking of making near floor-to-ceiling panels, though. I've heard that line arrays work even better if the drivers go all the way to the floor and the ceiling, though I don't know whether this style of speaker would get the same benefit from that as a line array. If there is no benefit, I would rather keep them shorter. From past experiences with my KLH Nines, I know that panel speakers visually dominate a room even when not so tall.

I could make a frame that the panels would overlap by about an inch, so that they could be affixed with sticky foam dots, as described. I could also run a brace from the top down to the floor a couple of feet behind the frame bottom, and run another bit of wood to the brace from the frame, forming a triangle in cross-section, and giving it a tripod base. The exciters would be free-floating.

Overkill? Underkill? Any suggestions?

Bob Law

Donka · « **Reply #103 on:** 29 Sep 2009, 06:21 pm »

Okay, so I have a bunch of exciters and a pack of Gator Board coming my way, however I have a question regarding the adhesive tape.
Do we need to cut rings or circles out of the tape, if so does the 1" wide cover properly to the edges? Also if somebody could verify that I need the 10mil thick version of 3M VHB, not the 5mil or thinner?

Thanks, this looks like a fun easy project after spending many hours the last few weeks building cabinets. Easy is good.

I also had a thought on mounting. Which is more critical to have free-floating the outer edges of the panel or the center. What about a stand that has 2 mounting points down the center-line 1/3 from the top and bottom, leaving the remainder of the panel to do vibrate out to the edges. Sorry if it's a poor idea, NXT is new to me.

FullRangeMan · « **Reply #104 on:** 29 Sep 2009, 09:31 pm »

HI BLOB,
By the little I know, Zygardr others and I agree that a Big NXT panel is better and a lot of NXT exciters is better.
I love Line Arrays, so Iam planing a NXT panel 75cm Wide x 196cm Hi (if I find a GatorFoam vendor here in Brazil), with 9 Dayton exciters in Serie-Pararell for a easy 8 ohms impedance.
The full GatorFoam plate sizes is 48'' x 96'' x 0,187'' and range 60 to 80 dollars in US (see this link http://www.piedmontplastics.com/html/prodname-Gatorfoam-21.htm

HI DONKA,
About the mounting Iam planing no framing mounting for no change FS and the good bass response, Iam planing just to support the GatorFoam panel in a pair of porcelain cables elevators. This is my idea today.
Best

bobloblob · « **Reply #105 on:** 30 Sep 2009, 12:07 am »

I'm curious about the function of width with these panels. Common sense tells me that wider would also help give more bass - however common sense also told people the earth was flat. Anybody do any comparisons on what increasing the width of these panels does?

FullRangeMan · « **Reply #106 on:** 30 Sep 2009, 12:34 am »

Quote from: bobloblob on 30 Sep 2009, 12:07 am

I'm curious about the function of width with these panels. Common sense tells me that wider would also help give more bass - however common sense also told people the earth was flat. Anybody do any comparisons on what increasing the width of these panels does?

Earlie in this thread there is some useful links, that talk about sizes/proportions, I will use one of it (golden ratio 2618=75x196) that is suited for big sizes. These are some links:
http://www.piedmontplastics.com/html/prodname-Gatorfoam-21.htm GatorFoam Vendor
http://www.vxm.com/NXT.html NXT doc by Henry Azima
http://www.aes.org/e-lib/browse.cfm?elib=13645 posicionando e otimizando varios excitadores NXT
http://www.colomar.com/Shavano/spkr_wiring.html Speaker Wiring/Loading Examples
http://www.google.com/patents/about?id=jaYIAAAAEBAJ&dq=dml+speaker patentes DML no Google
http://www.tymphany.com/exciters
http://www.jmaxx.cn/EN/ProductInfo.asp?sID=119&gCateID64 NXT exciter 10W/15W 4 ohms jiming@jmaxx.cn
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-375 price US$16 each
http://www.decibelhifi.com.au/category15_1.htm . . . . export price US$40 each

JeffB · « **Reply #107 on:** 30 Sep 2009, 12:58 am »

I probably have not followed this closely enough, but I was curious about the mounting.
I see two options, and don't know which is better. I am going to use a couple of stick figures and then try to explain these figures.

Design A. Side view. The left vertical bar is a pole attached to a base.
Attached to the pole are four exciters( o ). The exciters are attached to a panel on the right.
|-o|
|-o|
|-o|
|-o|
__ |__

Design B. Side view. Here are 4 exciters( o ) attached to a panel on the right.
The panel is suspended using fishing line ( ] ) from a bar or ceiling above.
___
]
o|
o|
o|
o|

FullRangeMan · « **Reply #108 on:** 30 Sep 2009, 01:29 am »

Quote from: JeffB on 30 Sep 2009, 12:58 am

Dear JEFF,
Iam afraid I no caption well your doubt. Zygadr use the naked panel supported on the floor and on the nearest wall.
The Dayton exciter may be glued at the panel, but Zygadr use double face 3M tape, for clean no dirty fixation. Zygadr do not use the panel mounting in a frame, maybe in the future, the sound is good right now.
Here is some instructive links of the Podium Site and the 6MOONS Test of the Podium speakers.
They have stunning closeup photos, that say all as to position the exciters (in the middle, in line, at equals distances between the exciters, The central point of the panel can not have a exciter fixed on it)
http://www.podium-sound.com/index.shtml?menu=56730A&id=56729 PODIUM SPEAKERS SITE
http://www.6moons.com/audioreviews/podium2/model05.html 6MOONs PODIUM SPEAKERS TEST
The better mounting is a personal choice you will do after listening both or just desing both, I prefer no frame mounting, and no spine column, that the small Dayton exciter do not need. Iam thinking a pair number of exciters is no good, as Zygadr use 7 exciters and Podium use 5 and 7 exciters, by this I will use 9 and not 8 exciters.
Regards

bobloblob · « **Reply #109 on:** 30 Sep 2009, 08:12 am »

Great stuff Ziggy. I'm really glad you did some pioneering here and shared it. I may wind up with shorter panels, but I noticed j gales (I think it was him) wrote earlier that he had not noticed a difference in sound from his panels freestanding and then mounted on a frame.

A frame would let me use taller panels. I mentioned the frame because I reasoned that I could maintain some rigidity with height, placement would be easier, and a triangular brace on only the frame should - and this may not prove true - but should solidify the bass, while making it easier to place in the room. It did so on other large panel speakers, but that remains to be seen with this type of speaker. I plan to use the smallest, and smallest number of, sticky foam mounts necessary. We'll see what the future brings. Visually at least, six feet is a lot more appealing than eight. The advantage to this is that I could always shorten the panels easily.

j gale · « **Reply #110 on:** 30 Sep 2009, 04:07 pm »

Just a few comments. I had 1 panel in a frame and 1 free standing for 2 or 3 days and didn't notice a difference in sound between the 2. The free standing one actually stood on 2 3/4" felt pads so was not damped much by the floor. I notice that my weatherstrip pads are sagging somewhat because of the combined weight of 8 exciters and the panel. I could probably take care of that by letting the panel sit on 1/4" dowells sticking out of the frame at the bottom. I'm thinking of trying it without a frame (just a base piece with a spline configured as a tripod) A 1 and 3/8 inch hole would accept my 2 for $5 exciters to a depth of 3/16". A little silicone adhesive would hold them in place.

:DI would continue the hole through the spline at a smaller diameter because of the vent hole through the magnet. Podium provides damping plugs for the holes. I presume that this can voice the high frequencies . I would also round off the corners of the panel to see if it makes any sonic difference (podium & NXT do this) Visually all you would see is the panel seemingly suspended on nothing.

lcrim · « **Reply #111 on:** 30 Sep 2009, 04:40 pm »

This is a fascinating thread to me.
Ziggy's photos were a huge aid to understanding his setup, it would be very
helpful to post photos of the frames (if used) as well.

bobloblob · « **Reply #112 on:** 30 Sep 2009, 09:30 pm »

Hi j gale,

There is a fundamental problem with foam-backed adnesives in this application: the foam between the adnesive layers has little shear strength. This is also what causes white and yellow glue to fail when the glue joint is not clamped. I can see the dilemma here, where you want to fix the panels to the frame, but don't want to do it rigidly. A much thinner foam would have more resistance to the downward shear force caused by the weight, but would be less flexible. There may be some sticky foams that have more resistance to this type of force, though. I think the ones with adhesive on both sides may be a bit sturdier in this case. Also, the double-sided foam sold in rolls may work a bit better. You can cut a couple of longer strips - a couple of inches or so - to use in a couple of places on the sides of the frame, which should greatly increase the resistance to shearing, and see if it affects the sound. If the longer strips were applied near the top, I would think it would not greatly affect the sound. Looks like you are taking a different approach now, so this may not be helpful.

j gale · « **Reply #113 on:** 30 Sep 2009, 10:32 pm »

Hi Bob, Thanks for your input. I suppose that even a rigid disc given the small area would work. Perhaps eliminating the frame in favor of just a base and spine is a mistake. Podium 'joins the panel to the frame by what they call sound bridges in 4 places non symmetrical. I gather this adds to the bass. I can always change back to a frame. If lopping off the corners is a mistake at worst it costs some more gatorfoam. I have more ideas than time.

It's probably going to take awhile to find out. I wonder what a line of exciters from 1 bottom corner to the opposite top corner as opposed to a vertical line up the centre would be like? Would the varying distances to the edges be beneficial or not? Would bass actually suffer? Would it sound significantly different?

Jim

JeffB · « **Reply #114 on:** 1 Oct 2009, 12:59 am »

I saw an early mention of carbon fiber as a possible panel. I did some internet searching and found this.
http://www.protechcomposite.com/servlet/the-149/carbon-fiber-sheet-panel/Detail
Maybe it is too thin, I have no idea.

I also found this
Benefits (of carbon fiber) include:

* Very high strength to weight ratio
* High resistance to fatigue
* Harmonic dampening characteristics
* Impact resistance
* Low coefficient of thermal expansion
* Resistance to corrosion.

The Harmonic dampening characteristics make we wonder if this is good or bad for a music panel.

FullRangeMan · « **Reply #115 on:** 1 Oct 2009, 01:51 am »

Quote from: JeffB on 1 Oct 2009, 12:59 am

* Harmonic dampening characteristics
The Harmonic dampening characteristics make we wonder if this is good or bad for a music panel.

Dear Jeff,
Zygadr say Carbor Fiber is heavier than GatorFoam and now with this Damping sound chacaracter you said, I think Carbon Fiber is bad to NXT panel, in the 6MOONS tests Mr. Shelley Katz say a good matter for panel must sound like a bell(I think it should sound dry and resonant like a good wood but without the weight of a wood panel).

j gale · « **Reply #116 on:** 1 Oct 2009, 02:02 am »

The sandwich panels there are interesting. Much like podium's panel. Too bad it would cost quite a bit to investigate.

FullRangeMan · « **Reply #117 on:** 1 Oct 2009, 02:11 am »

Quote from: zygadr on 30 Sep 2009, 07:44 am

I believe that the difference is to do with the spacing between the exciters and how many will fit on a certain sized panel within that ''spacing''.

There is something to this spacing of the exciters. I just don't know what. Podium have the right to keep this information secret, and rightfully so.

Dear Zygadr:
How the exciters fit on the panel or on the wood column of the Podium I do not know, but the spacing between the exciters is clearly used a Golden Ratio (1618 or 2618) in relation to height or width, by my eye it is in relation to Widt, but may have others details I do not see.
There is no other size ratio that creates less vibrations and resonances than the Golden Ratio or golden number, it is used in churches for centuries.

I use it on my project, on the sheet paper yet.
Best

JeffB · « **Reply #118 on:** 1 Oct 2009, 04:50 am »

This site
http://www.robotmarketplace.com/marketplace_carbonfiber_cust.html
provides an on-line price and weight calculator to have custom cut sizes for carbon fiber.
I decided to compare weights.
This site provides weight for some gator foam panels
http://buz-line.com/p-491-white-gator-foam-board.aspx
Gator foam: 32"x40"x3/16"(0.1875) is 28 ounces. $16.58 each if bought in a 12 pack.
Carbon fiber: 32"x40"x.015" is 11.27 ounces. $281.60 each.
The carbon fiber sheet is 12.5 times thinner and 60% lighter.

The carbon fiber link in the previous post was for a
22"x66"x0.010" sheet for $179.99, so this would be thinner and lighter still.
Of course if it is too thin, it might not have the required rigidity.
Plus, it appears to be very pricey for just experimenting.

Angaria · « **Reply #119 on:** 1 Oct 2009, 05:09 am »

I wouldn't mind investing in gathering a bunch of materials, if it was clear what the key mechanical properties of the materials were WRT bending waves. Then it's a case of gathering a range and seeing what correlates with the "best" sound.