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

zygadr · « **on:** 7 Aug 2009, 07:09 am »

I have in my pocession, two DIY, 79''tall by 28 inch wide by 1/4 inch thick prototype NXT panel speakers.

They will soon have a seventh NXT ''exciter'' mounted to the rear of each panel(all in a vertical array, evenly spaced but no one exciter in the exact middle of the panel). Impedance : 4.67ohms.
Due to 7 exciters per panel, I estimate a sensitivity of 95db, maybe a bit more.

For those who are interested, I have followed the design of PODIUM LOUDSPEAKERS in the U.K.

BUT, ........mine are somewhat larger with more exciters per panel than their biggest model(Model1 : 5 exciters per panel).

I have posted on this forum as it is the closest thing that relates to this type of speaker ( sort of).

The panels are made from GATORFOAM which is a polystyrene core sandwiched between a very thin wood fibre composite material known as LUXCELL (a kind of wood veneer ).

The exciters create a DML (DISTRIBUTED MODE LOUDSPEAKER) speaker which is essentially a large surface made to vibrate with random modal excitations.

I am stunned at how good these things sound but it's been a long hard road finding the right panel material and positioning the exciters to obtain optimum fidelity.
They can produce immense bass at times(but not sub woofer like) and have a transparency, speed and midrange resolution to die for.

They still need mounting in frames (no time lately

) so they rest vertically up against the edge(with a piece of spongy foam) of my horn speakers at the moment

I can post some pics. if anyone is interested?

Wind Chaser · « **Reply #1 on:** 7 Aug 2009, 07:23 am »

NXT - that sounds vaguely familiar... were those the Sonic Impact sticky things? I like the sensitivity and impedance. What can you compare the sound of your creation to?

Post the pics.

Viridian · « **Reply #2 on:** 7 Aug 2009, 01:39 pm »

This sounds like fun.

D OB G · « **Reply #3 on:** 8 Aug 2009, 05:32 am »

Hi zygadr,

Off OB topic, but I believe Naim and NXT have a financial relationship. Naim use a round driver in their new Ovator model from about 350 Hz to 20k. Good reports about the sound of the NXTs. Not so good about the conventional (very high quality) woofers.

David

Audiovista · « **Reply #4 on:** 8 Aug 2009, 01:45 pm »

Definitely interested in pictures!

Bob in St. Louis · « **Reply #5 on:** 10 Aug 2009, 08:34 pm »

It's all a bunch of lies until you post pictures.

Bob

jaspal kallar · « **Reply #6 on:** 10 Aug 2009, 11:50 pm »

I've listened to the Podium 0.5 model last year. It took a bit of time to get used to them. I compared the Podiums 0.5s to Quad ESL 2805s, although at a different location and with different components and cabling. So perhaps not a fair comparison. I thought, however, the Podiums 0.5's were better. Alas, they are too large for my room.

Other speakers I compared (most at different hifi shops) included the Zu Tone, Zu Druid ,Martin Logon Summit, Focal Utopia Be, WLM La Scala Monitor, Dynaudio Confidence C1 plus a few others I can't remember off hand. I thought the Podium sounded the best ... more like live music for recorded studio cd's. The Zu Druid I liked alot also (EDIT:even though it was not a full demo with these).

With certain genre (blues, classical and jazz) the Podiums are really good considering their price. I'm hoping Podium come out with a smaller model. YMMV. I know quite alot of people who don't the the Podium sound.

zygadr: What are components and cabling? Also, have you heard the Podium speakers?

Oh yes some pics please !

jaspal.

Angaria · « **Reply #7 on:** 11 Aug 2009, 05:58 am »

for clarification - you're using a bunch of these http://www.amazon.com/Sonic-Impact-Stick-Speaker-SoundPad/dp/B0001HKVKQ ?

which is the same transducer used in the Podium speakers?

fergs1 · « **Reply #8 on:** 11 Aug 2009, 06:23 pm »

Greetings zygadr, can't wait to see piccies.What part of Oz are you in, I'm a coupla hours out of Melb. If possible would love to hear them. cheers fergs

fergs1 · « **Reply #9 on:** 12 Aug 2009, 11:53 am »

Greetings zygadr, yes I'm afraid Perth is a wee bit far. How much did the two sheets of gatorboard cost and also where did you source the exciters in Oz. Good pics, thanks for sharing. Oh and what spacing did you use and how did you affix the exciters. Thanks in advance cheers fergs

panomaniac · « **Reply #10 on:** 14 Aug 2009, 10:27 pm »

Hi Ziggy - good to see you over here!

For those of you who want to play, now is the time. Parts express has some buyout exciters for $5 a pair, that's right, five bucks for 2! Won't kill you to get a few.

Ziggy is using the 5mm Gatorbaord, which I think is is called 3/16th in the US. It's not cheap, but probably a lot better than foamcore. I was wondering if using a standard 48x96" panel cut in 1/2 might be OK? Not as wide as Ziggy's 28" panel, but close.

Bob in St. Louis · « **Reply #11 on:** 14 Aug 2009, 11:02 pm »

Not sure I need another project, but would Luan or Masonite work?
Or is that too heavy?
This sounds like a neat project, but I think I'll pass on this one. I'll be lurking as it looks like fun. aa
Would love to hear one sometime.

Bob

FullRangeMan · « **Reply #12 on:** 15 Aug 2009, 05:07 am »

OK Zygadr, you get my full attention.

I have knew NXT in November1997 in the late Audio (US) magazine, but at this time it was useless to Hi-Fi applications by the low SPL, around 83-85dB. My speaker is a Carver Amazing Silver Edition since 1993, so I love panels.
If you was able to get 95dB the things have evolved since then. Please, inform me somethings about your panels:
1- Do your NXT panel work better with a Tube Amp or a Transistor Amp?
2- There is a sound difference between a number even or odd of exciters?
3- Do there is a max limit to exciters quantity?
4- How about the Bass performance of your panel? How Low it go?
5- How do you connected your exciters (serial, series-parallel etc)?
6- Do these DAYTON NXT exciters are MovingCoil or Piezo electric etc?
7- Do this NXT exciters work fine in a set of eight per panel, serie-parallel for 16ohms tube friendly impedance?
8- I live in Brazil and never see this Gatorfoam on sale here, Laminated Wood panel or acrilyc panel have a good performance?
9- How do you classified your NXT panel sound quality, Mid-Fi, Hi-Fi or Hi-End?
10- Do your NXT panel form a beautiful Stereo SoundStage ?
Thanks for share your impressions, Gustavo

panomaniac · « **Reply #13 on:** 15 Aug 2009, 12:00 pm »

There is a long thread on this project over on DIYAudio.com
Just a few notes I got from reading that old thread are:
Material needs to be both rigid and light. Thus the rather $$ Gatorfoam stuff.
The more drivers, the better.
Larger is better.
Zygadr loves the sound.

FWIW, I bought a pair of these a few years back. Stuck them on everything but the cat. Foamcore maybe worked the best for me, but I didn't try Gatorfoam. Glass was OK, too. But I didn't get a result that was anywhere near Hi-Fi. But I was not using 6 or 7 per side!
So this really needs to be done right and large scale to make it work.

I'm sure that Zygadr will fill in more details.

FullRangeMan · « **Reply #14 on:** 15 Aug 2009, 01:38 pm »

Thanks for your guidances.

doug s. · « **Reply #15 on:** 15 Aug 2009, 06:00 pm »

Quote from: panomaniac on 14 Aug 2009, 10:27 pm

Hi Ziggy - good to see you over here!

For those of you who want to play, now is the time. Parts express has some buyout exciters for $5 a pair, that's right, five bucks for 2! Won't kill you to get a few.

Ziggy is using the 5mm Gatorbaord, which I think is is called 3/16th in the US. It's not cheap, but probably a lot better than foamcore. I was wondering if using a standard 48x96" panel cut in 1/2 might be OK? Not as wide as Ziggy's 28" panel, but close.

parts express has other exciters at $17/pair - 1" woice-coil diameter instead of the 3/4" diameter of the $5/pair wersion. and, it has no bypass cap. also, the 1" wersion has built-in 3m adhesive pads, on both the woice-volis and the plastic housing. think this is a worthwhile improvement?

1" woice coil iteration (w/no hi-pass cap):
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-375

3/4" iteration w/hi-pass cap:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=309-148

doug s.

Russell Dawkins · « **Reply #16 on:** 16 Aug 2009, 07:27 am »

The Dayton version is rated at 6 watts rms, but the cheaper one is rated at 10 wrms. The 3/4" dimension relates to front-to-back depth; both are said to have 1" voice coils in the text.

Since these apparently rely on their own apparently small mass to push the diaphragm to which they're adhered, wouldn't it make sense and increase the efficiency to use some sort of strut down the back like the podium:
http://www.6moons.com/audioreviews/podium2/model05.html
and eliminate (cut off) the spiral plastic legs for less moving mass and better bass response?

I'd be curious to hear how it would sound to make horizontal cuts across the diaphragm to create 7 independent panels in very close proximity, so they would couple acoustically in the bass range and yet not be affected by the vibrations of adjacent transducers.

doug s. · « **Reply #17 on:** 16 Aug 2009, 02:13 pm »

Quote from: Russell Dawkins on 16 Aug 2009, 07:27 am

The Dayton version is rated at 6 watts rms, but the cheaper one is rated at 10 wrms. The 3/4" dimension relates to front-to-back depth; both are said to have 1" voice coils in the text.

Since these apparently rely on their own apparently small mass to push the diaphragm to which they're adhered, wouldn't it make sense and increase the efficiency to use some sort of strut down the back like the podium:
http://www.6moons.com/audioreviews/podium2/model05.html
and eliminate (cut off) the spiral plastic legs for less moving mass and better bass response?

I'd be curious to hear how it would sound to make horizontal cuts across the diaphragm to create 7 independent panels in very close proximity, so they would couple acoustically in the bass range and yet not be affected by the vibrations of adjacent transducers.

it's odd - p/e must have yust changed its info, as now both drivers say:

VCdia: 1" ? Dimensions: 3-1/2" dia. x 3/4".

before, it said, for the cheaper iteration: VCdia: 3/4".

doug s.

FullRangeMan · « **Reply #18 on:** 16 Aug 2009, 06:39 pm »

Thanks for this 6MOONS link, the PODIUM test are very useful, it have many detailed photos, they are real NXT speakers, interesting the 6MOONS text do not mention this! (ERRATA: They say any about NXT).

Dear Zygadr,
As you and other poster wisely say, a good NXT panel must be:
1- LARGE
2- HARD, STIFF
3- LIGHT
For me this 3 qualities are synonyms of CarbonFiber, that may be a expensive panel.
1- Do you try a panel of CarbonFiber??
2- For me have a idea of what I can look here in Brazil, please say me the net weight of your GatorFoam panel?
Thanks, Gustavo

Russell Dawkins · « **Reply #19 on:** 16 Aug 2009, 07:02 pm »

What makes you say they are real NXT speakers? There have been many other drivers/speakers designed along similar lines over the last 35 years at least, to my knowledge.