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

DanTheMan · « **Reply #640 on:** 11 Jan 2010, 03:21 am »

Quote from: doug s. on 11 Jan 2010, 02:53 am

uh no dan, i think you are mistaken. while it's true that some amps can double their output when its impedance is halved, (tho many cannot, especially tube amps), all this means is you may not have to turn up the wolume on your preamp as much to get 1w to your drivers when run in parallel, and you may have to turn it a bit higher to get 1w when run in series, due to the differing load the amp may see. but 1w is 1w; when a speaker is fed 1w, the increase in spl for adding speakers is as i described above. if you have one driver capable of 90db/1w, running two in series or in parallel will still theoretically give you 93db/1w.

doug s.

That's true, 1 watt is 1 watt. So from that perspective halving the impedance doesn't help you get more efficiency. It just makes your amp see less resistance/reactance. How your amp reacts to that is a matter up to the designer. I get you.

So then how do these panels react to additional exciters? Anyone know?

Dan

akreig2 · « **Reply #641 on:** 11 Jan 2010, 05:14 am »

First of all just wanted to thank Ziggy for the all the work he has already done....ie made my life so much easier. After just about 3 hours of work put in, I have fully functional speakers that would be acceptable in just about any room....aesthetics and a lack of bass always trumps no speakers at all. I mounted 2 exciters in 4 salvaged frame each and ended up with a product that actually is respectable. I so agree that NXT speakers have a mind of their own....ie no amount of actual planning will result in a perfect product...being an engineer i made that mistake

. So by the time i actually got done with producing these i think the cost was under 40 dollars total, not bad for 4 speakers...I ended up sandwiching a hard foam board between the matte and the corrugated cardboard on the rear of the panel....I fell this gave it much better bass. The foam and cardboard are held by four metal pressure bracket that actually allowed me to "sudo tune the frame". I found that with out the large amount of pressure put on the board by the bracket the frame sounded very air and lack mids and bass.

Can anyone see any flaws in this design or significant ways to improve it....thanks

DanTheMan · « **Reply #642 on:** 11 Jan 2010, 07:47 am »

Impressive for your first post.

Nice looking panel and I can't say I see any flaws, but I know nothing about the tech end of these things. I can say I like the idea and the look.

Quote

I so agree that NXT speakers have a mind of their own....ie no amount of actual planning will result in a perfect product...being an engineer i made that mistake .

There is no perfect product, just different levels of quality. I'm sure you realize that in all actuality. I'd like to build something of high quality but only have a faint clue of where to start. Any ideas on what panel features produce higher quality design? Seems you broke many of the guidelines discussed in this thread in developing your panels. Care to share from all your work? What did you try and find? Both will be useful to the community as a whole. Maybe this can lead the rest of us to higher quality designs.

Thanks!

Dan

akreig2 · « **Reply #643 on:** 12 Jan 2010, 01:49 am »

Quote from: DanTheMan on 11 Jan 2010, 07:47 am

Seems you broke many of the guidelines discussed in this thread in developing your panels. Care to share from all your work? What did you try and find? Both will be useful to the community as a whole. Maybe this can lead the rest of us to higher quality designs.

Sorry to hear about the forex....but i had a quick question. Has anyone else tried sandwiching or laminating two materials together. In the frames i made i was originally going to use a hard form core or corragated cardboard. When i mounted both of those panels the problems that were mentioned early throughout this forum and the diy audio ones became very apparent. Either lacking highs or just sounding plain muddy. From there i tried mounting both of the panel on top of each other with the exciters attached to the cardboard... it sound better but still not great. The last and most important thing i found was the securing the board with a high pressure bracket and gluing them together produced a pretty good sound. Without the bracket puting large amounts of pressure on the edges of the panel, the sound quality really sounds airy and lacks any punch, but with the added pressure it sounds pretty full....I guess the best of both worlds?

Large divots and pock market formed where exciters were removed from the foam board from the failed first attempt...so for the prototype of the sandwiched panels i used the damaged panels with the intent on replacing them if it worked. Long story short it worked...but when the damaged foam core was replaced with the fresh foam core boards the quality really took a hit...the low ends really dropped off. After some experimenting i am assuming the pits and pock markets in the foam core somewhat act like the honey comb of the podiums or provide a resonance chamber for the low end waves. Really all I know is that mine sounded better.

Anyways hope this helps and ziggy maybe pressing the gator board and the forex together might result in a superior "material", all i know is it worked in my case

.

j gale · « **Reply #644 on:** 12 Jan 2010, 02:01 am »

Zygadr, Thanks for the info on Forex-Sintra. Here in Canada Sintra comes in 9 different thicknesses, the most common being 3mm and 6mm. The 3 and 6mm are available in 12 colours. I used to screen print on 6mm sintra and remember is as being fairly rigid. With exciters on a spine even the thin stuff should work. I suppose it is good with highs and mids because it is described as "closed cell expanded plastic high density PVC" Your efforts have made me curious enough to want to experiment with larger pieces. I don't think that the price is too bad here.( I'll find out) If this is not the one I think it will be found soon. I see references to honeycomb cardboard etc. I agree that the foam core of the Gatorboard probably damps too much, but even so it's still good enough to be very clear. Others comment on how clear the music is.My biggest problem is lack of time so I won't have any opinions too soon.

j gale · « **Reply #645 on:** 12 Jan 2010, 02:48 am »

Zygadr, Will do. I would dearly like to get hold of a cardboard panel with a honeycomb core. Mother of tone and all that. If it doesn't have the hoped for tone it could be treated with violin lacquer or similar. I've always liked a somewhat damped aluminum as well.

j gale · « **Reply #646 on:** 12 Jan 2010, 03:31 am »

Brandon Wyatt marketing mgr. for Alcan Composites USA said " Thank you for your inquiry about Forex. In N. America it is known as Sintra." The bit about closed cell etc I got from a suppliers web site. I don't know which is wrong but wouldn't be surprised that different thicknesses are offered in Europe given the difference in name. I will check on the Sintra anyway.

DanTheMan · « **Reply #647 on:** 12 Jan 2010, 06:15 am »

http://www.kraftcomb.com/spacers.html

My guess is this stuff is probably the ticket.

Ziggy?

Dan

Russell Dawkins · « **Reply #648 on:** 12 Jan 2010, 08:37 am »

Quote from: zygadr on 12 Jan 2010, 04:00 am

I once spoke to a sound engineer while in my teens and we discussed speaker cones.
I still remember his stern comment on the new wave of cone materials starting to surface at the time and his insistance that I will find out one way or the other that paper sounds best...........no contest.
I thought he was just an old fashioned fool.

I am reminded of a review of an Audio Physic speaker which included a visit to the designer's house.

He had a stack of paper cones on the kitchen table - just the naked cones without surrounds, voice coils or formers - and while sipping his coffee and talking to the writer was idly picking up one cone after the other and letting them fall, listening to the sound signature of each as it hit the table' surface, knowing that a measure of whatever was heard even under these circumstances would be added to the sound being reproduced.

This way he was narrowing his choices.

Similarly, you might be able to speed the choosing of a suitable material by simply tapping and listening, before committing any further time to the process.

mkstat · « **Reply #649 on:** 12 Jan 2010, 09:31 am »

http://www.kueper.dusnet.de/platten/KAPASOUND.HTM

I don't know if this is freely available without NXT licence.

Unfortunately I have not found any further information on this - does anybody personly know an alcan respresentative?

Just the existence of this stuff makes me suspicious that the properties of the available standard foam materials are less than ideal for the use in a DML.

reagards
Markus

el`Ol · « **Reply #650 on:** 12 Jan 2010, 12:20 pm »

When I asked for Forex Classic in Sins, Switzerland I was finally handed over to a local sign maker, after several steps.

mndbndr · « **Reply #651 on:** 12 Jan 2010, 04:09 pm »

While searching for panel material, I ran across this http://www.panelteccorp.com/html/materials.html#ph

PH Series: Phenolic Backer Sheet Honeycomb Panels

The PH series honeycomb panels feature phenolic backer sheet faces and cores of aluminum or paper honeycomb. Backer sheet is available in thicknesses of .020", .032", and .049". Lightweight panels for use where appearance or high strength are not priorities.

PHP
Panel thickness 1/2" to 3" in increments of .02"
FACES: Phenolic backer sheet
CORE: 60-60-15 Kraft paper HC 3/8" cell
PHA
Panel thickness 1/4" to 3" in increments of .002"
FACES: Phenolic backer sheet
CORE: ALH-CG 1/4", 3/8" or 1/2" cell
Applications:

Flat Speaker Components
Stiffener Panels
Graphic Backings
Table and Countertop and Door Blanks
Electronic Whiteboard Backers

Here is a link to the mechanical properties. http://www.panelteccorp.com/html/paper-mechanical-properties.pdf

sedge · « **Reply #652 on:** 13 Jan 2010, 01:17 am »

Oops here I go again.
The metal panels I have been using sound very good to me ,very open and natural sounding with very low coloration,this is with one exciter so far.
The only reason I have not mentioned them is because they are not rigid so will not go low down ,say below 170hz for a large panel,400hz for a small8x24inch panel.
This is not a problem for me as I am quite sure I will be using a low fr driver to supplement whatever panel I end up with [to help with electronic and rock music].
As this forum seems to be, how to build a full range panel ,I thought I would try my other panel [rigid foamcore]with four exciters ,this sounds very good too.
The fr response is rolled off by the caps at 40hz[in too much of a hurry to take them off]but they go all the way up to 20k[there is a bit of a hump in fr between 12-18k] but does not sound bad.I am now building the second panel to assess the overall sound in stereo .
I was comparing the left channel [metal panel] with the right panel [rigid foamcore] ,they both sounded very good - but different .
The left sounding as above ,and the right sounding more like a horn [vibrant and alive with good vocals ,but I am sure I can sometimes hear the panels self noise [hopefully the two panels in stereo, will show this up] I have high hopes for this panel and will be keeping my fingers crossed .
sedge

j gale · « **Reply #653 on:** 13 Jan 2010, 05:20 am »

Zygadr, I would think that the double walled cardboard would be a different animal soundwise. Way more rigid and if as pictured the cores are staggered. Highs should be conducted through much better. I'm going to look for a piece. suppliers here want to sell you 10 sheets. Should be easy to stiffen surface paper as well.

bobloblob · « **Reply #654 on:** 13 Jan 2010, 08:00 am »

Just a passing thought here, which may not prove out in practice.

Corrugated cardboard has real strength in only one direction. Along the length of the corrugation, it is fairly rigid. Across, it bends quite easily, as I’m sure you have noticed. Ribs will stiffen it some in this direction, but it won't have that even rigidity that the honecomb material has. Front to back, the honeycomb material is quite rigid, as the form itself resists flexing. When it is corrugated, however, it’s like having a series of leaf springs, and will offer a tiny bit of cushioning, and most likely absorb high frequencies and lower volumes. If you could find a way to make the internal corrugations rigid, it should work well, I would think.

I’ve seen blocks of corrugated cardboard used as spacers, but the corrugations are front to back rather than up and down, and are not covered on either side, and they are very strong and very rigid. This is what makes some cardboard chairs (the ones that use the corrugations in this manner) so very strong.

I’ve seen rolls of corrugated cardboard which was covered on only one side, which would expose the corrugations so that they could be saturated with something to make them more rigid, leaving the open side to be covered with some sort of paper, which could also be made more rigid. I believe this material is used mostly as a cushioning device inside of packages. Wish I had the time and wherewithal at the moment to try this stuff myself.

Take this for what it’s worth - not much. I would probably give all these different formats of cardboard a try anyway.

bobloblob · « **Reply #655 on:** 13 Jan 2010, 08:03 am »

Doubling the cardboard may help, particularly if the corrugations are perpendicular to each other. This should give the cardboard similar rigidity in two dimensions. It may have the unfortunate consequence of greatly increasing the cushioning effect front to back.

Ray Ogle · « **Reply #656 on:** 14 Jan 2010, 02:22 am »

Here is a patent with a good description of differences in panels.
http://dl.dropbox.com/u/2080812/EP1322135A2.pdf

bobloblob · « **Reply #657 on:** 14 Jan 2010, 04:49 am »

Just a passing thought here, but has anybody tried these exciters as the motors in a linaeum-style driver? Might be fun for anybody with some extra drivers, and probably much easier to find decent material for. It looks as though it may be fairly easy to do a monopole version. Could be wide-range, but little bass, I suspect.

el`Ol · « **Reply #658 on:** 14 Jan 2010, 02:00 pm »

Quote from: bobloblob on 14 Jan 2010, 04:49 am

Just a passing thought here, but has anybody tried these exciters as the motors in a linaeum-style driver?

http://www.zilionis.com/forum/viewtopic.php?t=289

bobloblob · « **Reply #659 on:** 14 Jan 2010, 07:37 pm »

Amazing old radio, but the language loses me. Is that a linaeum-type driver?

I mentioned using these exciters this way because somewhere in an old Speaker Builder magazine there is an article about building a driver for a linaeum-style dual membrane. I think the article appeared before the Linaeums came out, but I'm not sure.

The author removed the cone of a standard cone driver and affixed the membranes to the motor of the now cone-less driver. It occurred to me that the exciters should also be great motors for this style of driver. I just thought that for those who had purchased extra exciters at the buyout price, this might be a fun side project. I don't want to hijack this thread, I just thought that this would be the best place to mention this, since so many of you have now acquired a pile of these exciters.

This may also be a way to add high frequencies to panels that may not transmit them well, while sticking to the same exciters, and perhaps with a little juggling they could be made to blend without using a crossover. Or not. Passing thought.