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

mndbndr · « **Reply #440 on:** 23 Nov 2009, 11:54 am »

Copper clad is printed circuit board material. Unetched. 2 thin copper sheets with fiberglass board in between.

mndbndr · « **Reply #441 on:** 23 Nov 2009, 06:56 pm »

Don't know if this was already posted. I didn't see it. http://www.engr.washington.edu/epp/iwaenc2008/proceedings/contents/papers/9058.pdf

Good read.

Brian

mndbndr · « **Reply #442 on:** 23 Nov 2009, 07:55 pm »

Here is another. http://www.tudelft.nl/live/ServeBinary?id=236fce6e-97a8-456e-9624-726037625b13&binary=/doc/Erwin%20Alles%20thesis%20MSc.pdf

Brian

mkstat · « **Reply #443 on:** 23 Nov 2009, 08:53 pm »

Quote from: mndbndr on 23 Nov 2009, 07:55 pm

Here is another. http://www.tudelft.nl/live/ServeBinary?id=236fce6e-97a8-456e-9624-726037625b13&binary=/doc/Erwin%20Alles%20thesis%20MSc.pdf

Brian

Thank you Brian! This is one of the most interesting papers I've seen so far!

Regards
Markus

bobloblob · « **Reply #444 on:** 25 Nov 2009, 06:34 am »

For anyone using shellac, here are a couple of tips:
Shellac has a short shelf life, and is best used within six months of manufacture, though it may last longer. Refrigeration will extend the life. Often the shellac sitting on a store shelf is past its prime. This has happened to me, and the shellac took much longer to harden, and remained somewhat soft and tacky even after months, never fully hardening. Fresh shellac dries fast and hard. The best way is to buy the flakes and mix as needed. Typically pre-mixed shellac is sold in what is called a 3-lb. cut, which means three pounds of flakes per gallon of alcohol. What we used in the trade was one pound cut, or one pound per gallon. This is thinner and what is usually used in French polishing. It also will probably penetrate into the cardboard fibers better, and stiffen with less weight. Several applications can be done to get to the desired effect, if this is what you are looking for.
Hope this may be useful.

sedge · « **Reply #445 on:** 25 Nov 2009, 04:33 pm »

Have noticed some potential problems with cardboard.
On voice and natural acoustics they sound great but if you play full range material that is very[busy ]sounding, things can get very jumbled , noisy and distorted.
The panel starts resonating all over the place, keep it simple and it sounds fine.
Also found discrepancies with near and far field response. Near field looks good but when you moved back the panel showed a large broad peek at 10 k ,on further investigation, if you moved the microphone around the panel within an inch or two ,you can sea the problem .the corrugation runs vertically and if you run the mic along the corrugation up from the exciter to the edge of the panel, you will sea the frequencies below 10 k drop away ,the 10 k hump stays firm .
So the panel is not peeking as such but is not transferring the rest of the frequencies along the panel,the outer response is bad the inner is good.
Going across the corrugation all the frequencies seem to fall away .
Zygadr if you use the scratch test you can hear what I mean,if you scratch the centre of the panel and put your ear at the top edge along the corrugation you will hear it bright and clear ,if you do the same across the corrugation you will hear it sounding dull.
My conclusion is unless you can use these effects to your advantage ,cardboard does not produce sound equally across the surface.the corrugation blocks sound going across and the panel and helps mainly hf along its length ,If all the frequencies die away together as they move away from the exciter in all directions this seems good to me ,but if different parts of the panel are producing varying frequencies [holding on to some and losing others] far field response will suffer ,near field centre response will look fantastic the rest of the panel will sound like sh*t! depending on where you put your ear !
Any thoughts any one ?

bobloblob · « **Reply #446 on:** 25 Nov 2009, 05:25 pm »

Shellac: if you have mixed it according to most formulas to get a standard brushing shellac, that should be about a three-pound cut, or about 340 grams/liter, by my rusty estimate, and doing a lot of rounding off. So, a one pound cut would be about 113 grams/liter. You can either start this way, or you can add two liters of alcohol to a previously mixed liter of three-pound cut to reduce it to a one-pound cut. No need to be dead accurate on this, as you are only getting different working consistencies here, and a few grams will make no difference. Which way is best to apply I don't know, but I would get a small piece to test it on, and buy a bunch of cheap natural bristle brushes. I always carry my thinned shellac in a squirt bottle because of the way I use it (French polishing). You could conceivably squirt it down betwen the corrugations too, or use a length of vinyl tubing to disperse it inside the cardboard, if you feel like experimenting.

Too bad you can't find a cardboard with the corrugations running perpendicular to the facing paper. They make furniture with cardboard, and it's quite strong, but they cut the cardboard and re-glue it with the corrugations on end instead of lengthwise - sort of like the end-grain blasa discussion.

cardboard chair, using the strength of the corrugations on end:

http://news.cnet.com/2300-13842_3-6233235-1.html

I sat in a similar chair once. It was extremely strong (and comfortable).

fivestring · « **Reply #447 on:** 25 Nov 2009, 07:03 pm »

OK, just briefly, have tried the 3.5mm thick Kapa and 2mm thick corrugated cardboard, the later is quite interesting indeed, but needs a little help (RCL trap). I tried with one exciter, sounds interesting and with this dimension could be used as midrange from cca 200/300 Hz upwards. Kapa is unusable in my view...

3.5mm kapa 50x70cm

2mm cardboard 60x70cm

captainjack115 · « **Reply #448 on:** 27 Nov 2009, 02:10 am »

Everyone is entitled to their opinion.

Have a look at this URL: http://theaudiocritic.com/plog/index.php?op=Default&Date=200608&blogId=1

If we all believed this, we would have dropped this idea. Keep up the R&D guys!

Jack

sedge · « **Reply #449 on:** 27 Nov 2009, 04:16 pm »

Zygadr
You say you are using battery power for your digital amp .are you using 12,24 ,or 36 v.
I had a look on sure elec site but could only sea a 4chanel version with heat sink,not that I mind as this would suite me better[no fan noise as I will be practically sitting on it].
Have you any idea how long the charge lasts playing at normal to loud volumes ?
Sorry for all the questions but it seems a fun project and cheep !
If you have any other suggestions or advice it would be much appreciated ,I got a little exited looking at the web site and had to force myself not to buy it until I new the facts.

fivestring · « **Reply #450 on:** 27 Nov 2009, 05:01 pm »

No need to shout zygadir (that`s what capital letters mean), measurements are much more meaningful as you can imagine, but it`s true that audiocritic measures and listens with the microphones only, while we try to use both, ears and mics.

I`ve just tested some Dibond panels that sound very promising, detailed and smooth at the same time, more so than any panel I`ve come across so far and also measures reasonably flat. I`ve noticed on the impedance curve it is much smoother than say, corrugated cardboard or any other material which is certainly a good sign, meaning the panel resonances seem to be pretty much under control. I have tried 90x29cm 3mm thickness and 90x23cm 2mm thickness, panels are structurally rigid and this is the first material I would like to try in larger dimension with multiple exciters.
I will report some more, right now I`m in a hurry...

sedge · « **Reply #451 on:** 27 Nov 2009, 06:58 pm »

captainjack115
He seems to be saying I measured these and they look bad but I think I could be doing it wrong? :duh:nuff said

captainjack115 · « **Reply #452 on:** 27 Nov 2009, 09:11 pm »

Quote from: fivestring on 27 Nov 2009, 05:01 pm

I`ve just tested some Dibond panels that sound very promising, detailed and smooth at the same time, more so than any panel I`ve come across so far and also measures reasonably flat.

This product looks intersting.

It may improve things from the exciter side, but I'm not sure the foam in the middle will allow the aluminum on the front to make as much improvement.

Certainly deserves a better look.

Jack

captainjack115 · « **Reply #453 on:** 27 Nov 2009, 09:22 pm »

Quote from: sedge on 27 Nov 2009, 06:58 pm

captainjack115
He seems to be saying I measured these and they look bad but I think I could be doing it wrong? :duh:nuff said

[/b]

All I did was point out the URL, nothing more.

My better half has been trying to write a cook book. Her problem with the project is that she cooks with a pinch of this and a dash of that.
Measurements have their place, all I know is she's a great cook!

I think I like the approach taken by Shelley Katz, a good mix of art and engineering.

Jack

captainjack115 · « **Reply #454 on:** 27 Nov 2009, 09:43 pm »

Quote from: zygadr on 26 Nov 2009, 07:06 am

In the mean time,running these panels with CLASS D amplification and BATTERY POWER leaves me speechless.

I played around with that little Dayton amplifer from Parts Express.

I have to admit, the highs were clean and crisp and not in any way too hot.
One day the little amp died, some day I'd like to try a more powerful unit.

Jack

gilbodavid · « **Reply #455 on:** 27 Nov 2009, 09:54 pm »

Hello all. I'm grateful to all your efforts to see if there's another material than gaterfoam, and i'm too busy to get my exciters out yet, but it all looks very promising. I can hear that there are some very experienced speaker builders here who understand measurements in the process, and i fully appreciate Ziggy's banging on about listening tests being the only measurement that matters in the end. i'm sitting listening to 'dipole' Lowthers with my new-to-me 15 yr old preproduction Croft EL34 push-pull amp with seriously expensive ($700 in 1995 i was told) output transformers and it is amazing the quality and levels and depth of bass and absence of any upper mid/lower treble peakiness aa. I'm sorry not to be more involved at this stage, but I can feel progress being made. Thank you again, Cheers, David

irishpatrick33 · « **Reply #456 on:** 28 Nov 2009, 05:19 am »

I would like to say thank you to all the hard work everybody has done, especially ziggy.

I also have a few questions before I take the plunge. And yes I just spent hours reading every post in both forums.

Gatorfoam is still king, correct?
Which color is king, seeing as how they are different?
Does the panel perform better when lifted off the ground?
How exactly is the tape applied?
How are people keeping the panel upright?

el`Ol · « **Reply #457 on:** 28 Nov 2009, 10:14 am »

Quote from: fivestring on 27 Nov 2009, 05:01 pm

I`ve just tested some Dibond panels that sound very promising, detailed and smooth at the same time, more so than any panel I`ve come across so far and also measures reasonably flat.

I had a private conversation with a guy on the other forum and he prefers Dibond to Gatorfoam. I am a bit puzzled that it works so well, since it is quite heavy (2.9 kg/m^2). This makes me think about Lamera Hybrix, a stainless steel "microsandwich", which has 1.5 kg/m^2 in its lightest form. http://www.lamera.se Its middle layer consists of short stainless steel fibers that reach from one cover sheet to the other. I wonder whether this structure alone (with the absence of any damping polymer) provides enough damping.

el`Ol · « **Reply #458 on:** 28 Nov 2009, 10:42 am »

If one was fanatic one could search here:
http://www.matweb.com

svnaudio · « **Reply #459 on:** 28 Nov 2009, 02:52 pm »

Wow!!! You are killing me (us)?!!!! What is it?