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

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CXW1219

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3040 on: 13 Oct 2017, 08:20 am »
In all honesty, I do not think graphenes are the way to go at present. There are too many unanswered questions.

It may have load bearing strength, as a monocrystalline monolayer, but what happens to it in the form as a 'bulk' material?

What happens to it if you drop it?

How does it respond to changes in temperature & humidity?

Is it resistant to chemical "attack" (ie: glue)

In short, how does it respond to "home" environment?

Now I am SURE there must be a material scientist out there with the answers to all these questions, and the answers may well show that graphene is indeed ideal for DML panels but my pragmatic view is that easily 'pretty damn good' speakers can be made from 'pretty damn cheap' materials.

Even if one wants to go super exotic, then a 2foot x 4foot carbonfibre/nomex honeycomb sandwich can probably be had for about £500 or less: this would still be pretty much The Bleeding Edge.

Maybe as I get older I hear less (but listen more...?) - and so get less bothered about chasing the tiniest % differences 'fancy' kit/wires/DACs etc bring.

That being said: semitransparent, impossibly thin, rigid floorstanding panels would be insanely cool. Especially if we could use LASERs to drive them.

Ben

crackie

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3041 on: 13 Oct 2017, 09:33 am »
Crackie welcome to the this thread........What I want to know is what is the definition of the word pistonic?.... Dont all drivers have moving coils and or move/vibrate in and out in a pistonic fashion to varying degrees? IF not, when EXACTLY does a driver become pistonic, what excursion levels of Xmax is required for a driver to be labeled as pistonic?

A sub driver aspires to be highly pistonic because it needs that excursion to produce a good amount of bass, while a mid range driver and or tweeter does not aspire nor requires to have a high degree of pistonic/excursion movement, since they are only reproducing the high frequencies.
Thanks for the welcome(s). Apologies for the delay responding.
For the sake of discussion, we can think of a moving coil driver's voice coil and an exciter's voice coil behaving in the same way and responding faithfully to the AC applied at its input. The cone motion on an 'ideal' moving coil driver would faithfully reproduce the input AC signal and apply pressure ( or not ) to the air in front of the cone. State of the art moving coil drivers from people like Accuton, Raidho, SEAS, etc variously use metal alloys, ceramics diamond and are notionally pistonic at the lower end of their bandwidth; they all cease to be pistons at the high end and become non linear. The point at which this happens is easy to determine by reviewing their CSD or distortion characteristics. A good old impedance curve also gives away many clues about non linearity.

Regarding your point about bass drivers needing to be pistonic and midranges/tweeters not needing to be pistonic, I think each transducer should behave pistonically ( over the chosen operating bandwidth ). IMHO the primary reason that different driver materials sound the way they do is due to their breakup behaviour when they are no longer behaving like pistons. When they are not pistonic they become modal, like a DML.

Regarding best panel materials; internal damping is the killer of HF so softer cores are poor.  The best foam cores, such as Rohacell, have very high compressive strength and work well. Honeycombe cores ( aluminium and Nomex ) are better still. Amina and Podium use honeycombs for a reason; I've met Shelley Katz from Podium several times and did some work for him early in the 'layered sound' project; the big Podium products sound great and have received some great reviews. They are very simple things though. High quality Nomex honeycomb cored panels and 4 decent tulip exciters; exciter technology has since moved on and, with a little research, its possible to source similar quality panel materials too. 

DMLs modal panel behaviour cause them to be very labour intensive to measure. Small microphone position and/or distance changes can have significant changes in the measurement. It is conventional to measure a moving coil at 1W/1m somewhere between HF and mid driver axes, this will only give you a small snapshot of a DMLs true output. A polar plot or some form of averaging is needed to really see how a panel is behaving.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3042 on: 18 Oct 2017, 11:47 pm »
In all honesty, I do not think graphenes are the way to go at present. There are too many unanswered questions.

It may have load bearing strength, as a monocrystalline monolayer, but what happens to it in the form as a 'bulk' material?

What happens to it if you drop it?

How does it respond to changes in temperature & humidity?

Is it resistant to chemical "attack" (ie: glue)

In short, how does it respond to "home" environment?

Now I am SURE there must be a material scientist out there with the answers to all these questions, and the answers may well show that graphene is indeed ideal for DML panels but my pragmatic view is that easily 'pretty damn good' speakers can be made from 'pretty damn cheap' materials.

Even if one wants to go super exotic, then a 2foot x 4foot carbonfibre/nomex honeycomb sandwich can probably be had for about £500 or less: this would still be pretty much The Bleeding Edge.

Maybe as I get older I hear less (but listen more...?) - and so get less bothered about chasing the tiniest % differences 'fancy' kit/wires/DACs etc bring.

That being said: semitransparent, impossibly thin, rigid floorstanding panels would be insanely cool. Especially if we could use LASERs to drive them.

Ben

The main issue with Graphene as well as other costly materials is the price....If graphene was cheap people would still try it even if there are many unanswered questions like you've mentioned.......when experimenting one can go through multiple panels before one gets it right to there satisfaction as the experimentation and development process is usually very costly way more so then just building the finalized product/design.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3043 on: 19 Oct 2017, 01:15 am »
Thanks for the welcome(s). Apologies for the delay responding.
For the sake of discussion, we can think of a moving coil driver's voice coil and an exciter's voice coil behaving in the same way and responding faithfully to the AC applied at its input. The cone motion on an 'ideal' moving coil driver would faithfully reproduce the input AC signal and apply pressure ( or not ) to the air in front of the cone. State of the art moving coil drivers from people like Accuton, Raidho, SEAS, etc variously use metal alloys, ceramics diamond and are notionally pistonic at the lower end of their bandwidth; they all cease to be pistons at the high end and become non linear. The point at which this happens is easy to determine by reviewing their CSD or distortion characteristics. A good old impedance curve also gives away many clues about non linearity.

Regarding your point about bass drivers needing to be pistonic and midranges/tweeters not needing to be pistonic, I think each transducer should behave pistonically ( over the chosen operating bandwidth ). IMHO the primary reason that different driver materials sound the way they do is due to their breakup behaviour when they are no longer behaving like pistons. When they are not pistonic they become modal, like a DML.

Regarding best panel materials; internal damping is the killer of HF so softer cores are poor.  The best foam cores, such as Rohacell, have very high compressive strength and work well. Honeycombe cores ( aluminium and Nomex ) are better still. Amina and Podium use honeycombs for a reason; I've met Shelley Katz from Podium several times and did some work for him early in the 'layered sound' project; the big Podium products sound great and have received some great reviews. They are very simple things though. High quality Nomex honeycomb cored panels and 4 decent tulip exciters; exciter technology has since moved on and, with a little research, its possible to source similar quality panel materials too. 

DMLs modal panel behaviour cause them to be very labour intensive to measure. Small microphone position and/or distance changes can have significant changes in the measurement. It is conventional to measure a moving coil at 1W/1m somewhere between HF and mid driver axes, this will only give you a small snapshot of a DMLs true output. A polar plot or some form of averaging is needed to really see how a panel is behaving.

I understand the DML concept thanks for your explanation.....Rohacell seems to be pretty expensive like the nomex honeycomb materials hence why a lot of people wont use it to experiment on....There are 12 types of Rohacell listed on there site ,which one is the best suited for DML panels?

Also since you have worked at Amina, what is the frequency response of the Amina honeycomb panels? Any NXT or Amina white paper/ariticles you care to share with us? Thanks.

CXW1219

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3044 on: 19 Oct 2017, 10:37 am »
Developments:
I have ordered some Nidaplast core...going to vacuum laminate with either silk or paper & epoxy at the weekend Dog/Daughter/Work permitting!
 :icon_lol:

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3045 on: 20 Oct 2017, 12:00 am »
CXW1219, it sounds expensive, what size panel and how much did it cost you? Thanks.

CXW1219

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3046 on: 20 Oct 2017, 05:59 pm »
Not mega:

https://www.ecfibreglasssupplies.co.uk/product/nidaplast-10mm

so about £20 for 1.2x1.2m

Planning on cutting down to A1 size the laminating with silk bonded with West System epoxy.
I have a few metres of very thin shirt material kind of silk... have been experimenting with smaller panels laminated onto cardboard honeycomb.
I have 'perfected' (clearly a relative term...) a reasonable way of making composite sandwiches just using a vacuum cleaner and some big laundry vacuum bags.
These kinda things:

https://www.amazon.co.uk/BOUYA-Compressed-Double-Zipper-Hand-Pump-Bed-linen/dp/B06XRXQJ14/ref=sr_1_1?s=kitchen&ie=UTF8&qid=1508522173&sr=1-1&keywords=BOUYA

So all in all a low cost way of knocking out what I hope will compete with more High End panels...
#fingerscrossed

crackie

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3047 on: 21 Oct 2017, 07:46 pm »
I understand the DML concept thanks for your explanation.....Rohacell seems to be pretty expensive like the nomex honeycomb materials hence why a lot of people wont use it to experiment on....There are 12 types of Rohacell listed on there site ,which one is the best suited for DML panels?

Also since you have worked at Amina, what is the frequency response of the Amina honeycomb panels? Any NXT or Amina white paper/ariticles you care to share with us? Thanks.

For a DML the standard industrial grade (IG ) is fine; the numbers in their product range identify are the material's density. 31 IG is the lowest density and therefore the highest sensitivity for 'our' application. IG51 would fine too. There are many other low mass thermal insulation foams which can work extremely well too.......unfortunately it is often difficult to find them in the optimum thicknesses though. 4-6mm is optimal for large full range panels. 

There are alternative honeycomb panels which cost less than similar Nomex and Aluminium alternatives.
http://www.coretexgroup.co.uk/Honeycombcore.html

Amina's panel standard panel size dictates the response at the low end. There is a high pass to protect the panels and improve power handling; low end is deliberately limited to -3dB at 90Hz. The exciters used are Amina's own designs, are assembled in-house and they aren't available to the public. The specific HF exciter extends HF to above 40Khz. As I mentioned in earlier, excessive internal damping i.e soft cores are the killer of HF.

http://aminasound.com/file-directory/product/loudspeakers/mobius/datasheet/Mobius5_Datasheet.pdf

I don't have any white papers, sorry.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3048 on: 23 Oct 2017, 01:24 am »
For a DML the standard industrial grade (IG ) is fine; the numbers in their product range identify are the material's density. 31 IG is the lowest density and therefore the highest sensitivity for 'our' application. IG51 would fine too. There are many other low mass thermal insulation foams which can work extremely well too.......unfortunately it is often difficult to find them in the optimum thicknesses though. 4-6mm is optimal for large full range panels. 

There are alternative honeycomb panels which cost less than similar Nomex and Aluminium alternatives.
http://www.coretexgroup.co.uk/Honeycombcore.html

Amina's panel standard panel size dictates the response at the low end. There is a high pass to protect the panels and improve power handling; low end is deliberately limited to -3dB at 90Hz. The exciters used are Amina's own designs, are assembled in-house and they aren't available to the public. The specific HF exciter extends HF to above 40Khz. As I mentioned in earlier, excessive internal damping i.e soft cores are the killer of HF.

http://aminasound.com/file-directory/product/loudspeakers/mobius/datasheet/Mobius5_Datasheet.pdf

I don't have any white papers, sorry.

So how does rohacell panel sound compare to that of nomex or aluminum honeycomb panels? Which one do you think sounds better?

How does those cortex honeycomb panels compare with the nomex/aluminum panels in terms of sound quality? Which one do you think sounds better?

So amina panels are more like sat speakers which require a sub for the low end?....wow a exciter that extends to 40khz, now that is the type of exciter I want and need.


crackie

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3049 on: 24 Oct 2017, 07:18 am »
So how does rohacell panel sound compare to that of nomex or aluminum honeycomb panels? Which one do you think sounds better?

How does those cortex honeycomb panels compare with the nomex/aluminum panels in terms of sound quality? Which one do you think sounds better?

So amina panels are more like sat speakers which require a sub for the low end?....wow a exciter that extends to 40khz, now that is the type of exciter I want and need.
The best PMI foams like Rohacell are still behind honeycombs when is comes to compreesion strength; consequently their HF rolls off. Amina's HF exciter does not extend to 40kHz on a Rohacell panel.

Rohacels sound has slightly detail relative to the honeycomb cores; its compressive strenght is not as good. The sound signature of a panel cannot be attributed to the choice of core material alone; a huge number of factors contribute. Core, skin and adhesive all make significant differnces as do the size, mass, aspect ratio, exciter type and exciter position on the panel, suspension method, edge treatment. etc . It would be possible to make a honeycomb panel less detailed than a Rohacell if you deliberately wanted to engineer it to behave that way.

Amina chose the best panel materials they could find and then used some tricks to further enhance and response shape the panels response. These tricks were first developed by NXT and were used in most of Mission's DML products; response shaping can easily be achieved by using a small miniDSP 2x4 today but it is possible to achieve a very flat in room acoustical power response by using this response shaping method. DMLs are already very good in this respect and imho this is why DMLs sound appeals so much.

crackie

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3050 on: 24 Oct 2017, 07:36 am »
So how does rohacell panel sound compare to that of nomex or aluminum honeycomb panels? Which one do you think sounds better?

How does those cortex honeycomb panels compare with the nomex/aluminum panels in terms of sound quality? Which one do you think sounds better?

So amina panels are more like sat speakers which require a sub for the low end?....wow a exciter that extends to 40khz, now that is the type of exciter I want and need.
Apologies, I forgot a couple of points you raised.  The coretex panels' compressive strength is behind the aluminium and Nomex but not by much; the coretex type panels had Mylar skins with a thinn damping scrim in between. I thought they sounded great. Nomex core with Mylar type skins ( Podium ) is excellent and probably my favourite subjectively.

Amina's panels are designed to work in wall, between studs. The size restriction limits the number of modes at the low end; there would be very poor perfomance between 55Hz and 90Hz on a panel that size. Consequently they need subs to work at there best; taking LF away froma DML is always a good thing. I developed the ALF80 and ALF120 subs when I was working there. The 80 is a conventional bandpass but the 120 was fun to do and has some unique stuff going on inside. A home cinema setup with 5 or 7 Amina panels with a 120 is genuinely full range system and sounds great. http://www.insideci.co.uk/reviews/amina-alf120-in-wall-subwoofer-review.aspx

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3051 on: 24 Oct 2017, 08:18 am »
Hey Crackie thanks for all the info appreciate it.....I have a few more questions what is the best adhesive to use and what or where can one purchase the type of mylar skin used on the podiums, thanks.

CXW1219

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3052 on: 28 Oct 2017, 08:59 pm »
Progress Report:
The Nidaplast is a bitch to work with.
 :o
It has a woven polyester material bonded to the honeycomb structure. The reason for this is to aid panel bonding, but I found this a (bad) terrific sink for resin, massively increasing weight compared with the cardboard honeycombs.
Sadly panel adhesion was also a bit sketchy at the edges - causing a lot of 'buzzing'.

There is another V2 paper/nidaplast panel 'in a bag' right now - but I think I screwed up the resin:hardener ratio so this + the onset of seasonal weather may mean my next post is in a months time... :duh:

I have two parallel arms of development going on next:

1. 'Superlight'
Black Diolen 200g Twill Weave ((Cheaper than silk!))
Lantor Soric XF - 3mm

2. 'Natural'
A1 Goatskin Parchment - should go translucent with the resin, will show off the pretty cells of...
(The last of my) Cardboard Honeycomb


Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3053 on: 28 Oct 2017, 10:59 pm »
When choosing ideal panel materials keep these first two things in mind....it needs to be really LIGHT but yet HARD/DENSE at the same time...that is why UHD grade of EPS has worked great for me as its very light but also very stiff.


crackie

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3054 on: 30 Oct 2017, 07:32 am »
Hey Crackie thanks for all the info appreciate it.....I have a few more questions what is the best adhesive to use and what or where can one purchase the type of mylar skin used on the podiums, thanks.
The adhesives used for commercial panel construction are typically supplied in sheet form and require the correct combination of heat, time and pressure during the curing process. Different adhesives are needed for different cores and skins; for example aluminium oxidises in air very quickly and becomes difficult to bond to and some 'polymer' skins have low surface energy and are inherently difficult to bond. This link explains in more detail https://compositesuk.co.uk/system/files/documents/Adhesive%20bonding%20of%20composites_0.pdf

Regarding mylar sheet for skins
http://www.katco.eu/uk/site__1344/

https://www.ebay.co.uk/i/162059123501?chn=ps&dispItem=1&adgroupid=48942490953&rlsatarget=pla-372384701665&abcId=1128946&adtype=pla&merchantid=7105634&poi=&googleloc=1007017&device=c&campaignid=856243387&crdt=0

CXW1219

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3055 on: 13 Nov 2017, 05:04 pm »
(Not lost interest...just moving house soon... with a 'garage' fro panel fabrication :P)

SubOptimal

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3056 on: 20 Nov 2017, 07:33 pm »
Good evening all.
I've just ordered up a pair of Dayton DAEX30HESF-4's.
I have used BMR's a few times in the past before reverting back to traditional cones and domes.
Look forward to making some valued contributions.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3057 on: 6 Dec 2017, 02:00 am »
I just got my 2ft.X4ft. ultra hard density panels so I am excited to start on these bigger panels....although I am a little pissed because 1 of the 5 panels I ordered is slightly damaged as each panel is roughly around $20.00 each. as total cost including shipping is around $125.00.......Also this is clearly the fault of the seller because he did not pack them right as stated on his site....In the future I might have to find another source for high grade quality EPS........I also ordered 22 more exciters from P.E. and waiting for them to arrive so I can start on this new project with the bigger panels.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3058 on: 10 Dec 2017, 01:17 am »
My exciters arrived this week so I am going to try and start my project using the 2ft.X4ft. panels even though I am pretty busy during this holiday season....I tested these raw panels briefly just to hear how they sound, playing the dead can dance track by Mr.Lovegrove and Oh boy it gave me goose bumps with 3D like separation of instruments in that track as if not all the sound is emanating directly from just the two panels...with my smaller panels I would need to use all 5 channels to duplicate the sound presentation of the 2 larger panels.

I am also thinking about up grading my receiver to one with Dolby Atmos/3d just to see if I can take the sound of my panels even further to the next higher level.