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

bobloblob · « **Reply #1160 on:** 18 Dec 2010, 07:04 am »

Sedge,

Pictures would be great (and appreciated) if you can do them too...and thanks for this interesting new variation on the theme.

sedge · « **Reply #1161 on:** 18 Dec 2010, 02:49 pm »

Bobloblob
Pictures are a problem at the moment as I have forgotten how to do them, so will have to get my daughter to show me AGAIN!
But there isn’t a lot to see, really just a big white panel with two exciters hanging from up lighter stands.
And to be honest this is not a variation on the theme, I have done nothing different from my other panels except used glue to stick the exciters on, plus the usual damping.
The tape might be alright for flat smooth stickable surfaces, but not rough cut uneven poly with holes in that tends to come unstuck if you are not careful.
When I first heard these panels some time ago ,they sounded crap and sticking paper and tin foil was just making them worse ,no top end and no bottom end ,hence a midrange I thought!.. and an hour later the exciter would fall off.

panomaniac
I am composing GIANT KILLER PANELS PART TWO.
must get it right, in my head firt.
I think my wife has let the dogs into my room AGAIN as one of the panels is lying on it's sides with the exciters ripped off, so I can't do tests with that one for a while

sedge

panomaniac · « **Reply #1162 on:** 18 Dec 2010, 04:23 pm »

Maybe the puppies are trying to tell you something.

bobloblob · « **Reply #1163 on:** 18 Dec 2010, 09:42 pm »

Sedge,

By variation on a theme I just meant that you were doing Zygadr's panels with a slight difference at this point - 2 exciters per panel, smaller panel, which makes them a little different. Nice to read that you are getting good results even with this set-up. How is the bass response? That is where I imagine the biggest difference would be.

Hope you have a Merry Christmas (or whatever holiday you celebrate) and a Happy New Year

sedge · « **Reply #1164 on:** 19 Dec 2010, 10:50 pm »

GIANT KILLER PANELS PART TWO. (in the music room ,no one can hear you scream…………….with joy!)

Since building the first 18 inch wide panel with one exciter, I have made two further panels, one 2ft and one 4ft wide, all 4ft high and 25mm thick, using two exciters per panel.
The t-amp I was using is rated at 8 watts at 8 ohms, if that.
This drove my hifi News test cd with the sound of BIG BEN striking twelve, to realistic levels,I kid you not! Plus the lovely sound of the clockworks clinking and clonking as clear as a bell…..ha ha .
I am sure the neighbours loved it as much as I did.
So I think I can safely say that these panels are very, very efficient.

To make these panels is very easy, and only takes an hour or two If using a hair-dryer,but the hf will not be good until the glue hardens, this takes at least 24 hours, so be patient.
You could do as I do ,and just hang them from a stand ( cheap up lighters, in my case -best sound for me so far), but if you mount the panel in any other way you must make sure you do not restrict the panel movement in any way, or else you will lose dbs and alter fr. So take care.
The glue I have used for the panels is nothing special. It is just that I had a gallon lying around and it sounded good on other panels as damping.
The 2ft by 4ft is probably the easiest size to work on and you can easily cut an 8ft by 4ft sheet into four to fit in the car,if using a van or lorry 8ft by 4ft max !!!I would love to try this and could use it as a projector screen with a higher quality polystyrene. The panels do not shake around as my metal panels used to - its just a thought,so far!
To damp the panels I used a 50 50 mix of water and pva mixed in a 1 lb (400grm or so?) jam-jar ,this should do 2 panels, a thin a coating as possible so the panel is just wetted, if you use too much glue you could over damp the panel but if it is still under damped you can add another thin coat.
If you are doing this on the kitchen table be warned glue will seep through in places .
The panels should be damped on one side only!!! And this is the side the exciters will be glued on, you can use a hair dryer to dry this coat, 15 mins or so, and when dry, its time to glue the exciters on.
I used undiluted pva for the exciters, using a match-stick to apply the glue onto the foot. Try to get a nice mound of glue on the base and also dab the sides of the foot. Make sure none goes into the voice coil.
Just remembered that I used sand-paper to take the shine off the exciter foot and hopefully give a little adhesion.
I also applied a thin coating of undiluted glue about 3 inches in diameter around the fixing position. Not sure if this helped in any way but that’s what I did.
Also using the match-stick, build up a small mound of undiluted glue around the area that the foot will come into contact with the panel. The glue will shrink and hopefully this will help fill the gaps.
You could use the hair-dryer to start the drying process on the panel and the exciter, before sticking them together.
Using glue that does not shrink, so as to fill in the gaps could be an idea at a later date but the sound would have to be checked.
I also placed a little bit of weight on the exciter to give a good bond, enough to push the exciter foot into the panel without damaging the voice coil.

Dry the glue using a hair-dryer, waving it around from all sides. The exciter will eventually get hot ,very hot, but don’t worry.. If you are a little worried that the panel is getting too hot, you could always leave it to dry over night instead, its just that I only had a couple of hours till dinner and my wife had a gun at my head!
So if you have to move them after a couple of hours keep them somewhere with a flat surface and leave them to dry overnight ,you can wire them up ready but they will not sound good until the glue hardens, probably after a day or two.
If you are using two exciters I found it better to have the connections facing each other (on the inside) but it’s your choice.
While I think about it I hope every one has removed the horrible plastic casing with those stick on wobbly feet, if not you have got problems!
AS for the position of the exciters ,I used a one third up from the bottom and a one third down from the top in a centre line, other spacing’s could give a better sound ,or maybe not.
But this position sounded superb so it’s a good start.

Also I rounded off the corners of an experimental panel which I had used to trial the damping
But can’t say that I heard a lot of difference, my mind was on other things at the time and now they are lying on the chair with the exciters ripped off but hopefully I can try again at a later date.

sedge

irishpatrick33 · « **Reply #1165 on:** 20 Dec 2010, 05:38 am »

I had an idea about using an EPS ball as the baffle.

http://www.plasteelcorp.com/

It costs a bit too much for me to attempt an omnidirectional-upward facing-NXT-sphere ($85 for each 30" sphere).

Almost tempted to try using the half-sphere, with the bowl facing up into a 360 degree deflector. This is the typical omnidirectional design nowadays. Like this for instance:

I am even attempted to order some of those other crazy shapes (Cubeoctahedron, Octahedron, Tetrahedron, etc.).

What do you think?

sedge · « **Reply #1166 on:** 21 Dec 2010, 12:09 am »

Bobloblob

The bass response depends on the room and where you place the panels .
In my living room 5m x3 + bay window I was getting a very respectable Fr from 40hz upwards but I could not move the rta mic around the room because I was stretching the cable from the music room.
Later when I had placed them back in the music room ( but not back in the usual position), to see if I could get rid of the 100 to 300 hz suck-out ).
I had the panels 3m apart along the length of the room with me sitting 2m in front.
In this position the Lf was level down to 25 Hz ,but if I moved the mic around lets say 3 ft to the right and 2ft forward there were suck-outs again.
So the room and positioning is everything.you cannot just shove a panel in a room and expect it to sound good. I have got a lot to do to get this room sorted.
But saying that, when I was sitting in the chair in the good position I was treated to a very spacious sound with plenty of Lf .
Fore instance ,I played the sound track from ‘blade runner’ it’s one of my favorites .
The last track ,tears in the rain has what sounds like a loud implosion on it and you are almost sucked in to this,I loved it.
To be honest, when I’m listening to poly panels (and I include the 5mm deep by 40cm square poly panels in this, if used with an Lf unit)I feel I am being drawn into the studio and am hearing the real live performance be It a female voice or a drum kit ,it’s the real thing not HI-FI !

sedge

bobloblob · « **Reply #1167 on:** 21 Dec 2010, 03:25 am »

Sedge-
Wonderful to hear it. Now we have Zygadr's panels, your panels, and pol's wide single-panel to try. Your description of the sound seems similar to what I was hearing when I was running two double KLH Nine panels years ago. They sounded wonderful too, but they were finicky about amplifiers, took up a lot of visual space (each double panel was 4'x6') and were getting old and needing too much maintenance. I've been looking for ways to recreate that sound without the drawbacks and the cost of the new speakers that would sound as good (Maggies, while good, don't cut it for me - and the two people who each bought one set of the KLHs from me were "trading up" from some high-end Maggies). Please keep up this most excellent and fun experiment.

I have the exciters and the desire to do this, but am in the throes of the realty depression here when I really need to sell my home. Everything is in flux at the moment. Arrgghh!

pol_bct · « **Reply #1168 on:** 21 Dec 2010, 10:36 am »

Hello all
I would add my impressions after all the cut&try I did in the last months.
there is a frontiere in the world of sound reproduction, and my opinion is that it is about the surface of radiation. I already talk about this topic , but it seems to be of matter. it lies under 1 square meter (m²) and above.
you can put together the finest transducers and get a very flat response, and low distortion, and clean phase, and constant directivity, but it will always sound like HiFi, because of the small overall surface of radiation.
When you jump above 1m², like I now have 4m², you enter a new world,
sounds are no more projected, they fill the space, walls reflections are still there, but faint and blur. you get lifelike sound image, and aiming at flat responses and low distortions, become less important.

POL

Garytr · « **Reply #1169 on:** 21 Dec 2010, 04:42 pm »

Hi All,
I have several of the PE cheapies and want to try a pair of mid-treble panels with my open baffle subs. I believe I can remove the plastic legs form the exciters easy eneough, and the PVA sounds promising, but where can I purchase the EPS? Density/compressive strength? Thickness? I live in Canada, close to Niagara Falls, so sourcing in the US is fine.

garytr

bobloblob · « **Reply #1170 on:** 21 Dec 2010, 04:54 pm »

POL

I think this relates to an article I read years ago about the difference between listening in the nearfield versus the farfield. It said that the bigger the transducer, the farther away the nearfield listening area will extend. To be in the nearfield of a typical box speaker, one must listen close-up. One of the reasons large panels sound so good is that their near field extends much much farther into the room, but I think the effect relates more to the height of the transducer than the area.

Thsi would mean that the nearfield for your speaker and Zygadr's would cover a greater area than Sedge's. However, Sedge's would have this effect too, just not as far into the room, but much farther than a box speaker would. Sedge may still be in the speaker's nearfield. This is also why typical mini-monitors sound so good as desktop systems, but not so good as room speakers.

The above is all just supposition, of course, since I don't have the acoustics background to support the statements. It is merely what I understood from the article. But yes, it appears that bigger is better.

Bobloblob

pol_bct · « **Reply #1171 on:** 22 Dec 2010, 02:30 pm »

bobloblob
yes, you are right, this is related to nearfield and farfield, but there is more to gain than a simple closeup listening. This has to do with the old & fantasmatic poursuit of point source radiation, it may be interesting from a theoritical view, but in the real world, sources are rarely seen as points, and trying to listen to a symphonic orchestra through a pin hole is a kind of fantasm. An orchester has surface and power, and I think we need the equivalent in sound reproduction to get an acceptable illusion.

POL

Nickolay V · « **Reply #1172 on:** 27 Dec 2010, 01:46 am »

During long time we test NXT speakers (!factory made) with almost all existed type diaphragm materials.
Best of the best result was with Phenolic Paper Honeycomb( Carlsbro nLIGHTn )
("mother-of-tone" ,EXPRESSION, sensitivity,Dynamic Range etc)

irishpatrick33 · « **Reply #1173 on:** 27 Dec 2010, 06:39 am »

OK. Where do you get phenolic paper honeycomb? How much does it cost?

Because a big part of the equation is building a very cheap qualify HiFi speaker.

bobloblob · « **Reply #1174 on:** 27 Dec 2010, 08:12 am »

irishpatrick33-

search for NOMEX - perhaps it is branded differently in some countries, but that is the name in the US.

Forgot to mention, just in case you had not been following the whole thread, that Zygadr and Sedge are using VH grade EPS (expanded polystyrene) of different thicknesses presently, while POL is using corrugated cardboard. NOMEX, the version with phenolic resin coated paper honeycomb, as used in the Podium speakers. is quite expensive. Judging by the results of others here, EPS works very well and is considerably cheaper.

irishpatrick33 · « **Reply #1175 on:** 28 Dec 2010, 05:33 am »

Quote from: bobloblob on 27 Dec 2010, 08:12 am

irishpatrick33-

search for NOMEX - perhaps it is branded differently in some countries, but that is the name in the US.

Forgot to mention, just in case you had not been following the whole thread, that Zygadr and Sedge are using VH grade EPS (expanded polystyrene) of different thicknesses presently, while POL is using corrugated cardboard. NOMEX, the version with phenolic resin coated paper honeycomb, as used in the Podium speakers. is quite expensive. Judging by the results of others here, EPS works very well and is considerably cheaper.

I know. That's kind of my point. Using expensive materials kind of runs contradictory to the whole idea/thread.

bobloblob · « **Reply #1176 on:** 28 Dec 2010, 06:35 am »

irishpatrick33-

I assumed yours was a serious question, which is why I posted what I did. Since I've seen your posts along this thread, I couldn't understand why the inquiry about NOMEX. I guess this is why emoticons exist, though I don't use them either. I think your post appeared before Nikolay's this morning too, since I don't remember seeing Nikolay's when I read yours. Strange - or maybe it's just my age.

Take care

sedge · « **Reply #1177 on:** 28 Dec 2010, 01:33 pm »

NORMEX is too heavy, very technical and expensive.

Styrene has the best EXPRESSION, sensitivity ,dynamic range etc.
‘mother–of-tone’?
All I know is , a poly panel is(a mother of a panel).

sedge

panomaniac · « **Reply #1178 on:** 28 Dec 2010, 03:24 pm »

Actually I'm really intrigued by the foam spheres that Patrick posted. The big ones are $$$, but the 16" could be fun to try. I have a 16" globe, and that's a pretty big sphere. It has more surface area than a 2x2' panel (one side at least.)

Since they are split in 1/2, you could put an exciter in the apex of both and close it up to make a sphere or use them open to hear the difference. It looks like the 16" size includes shipping, over that requires a shipping quote.

sedge · « **Reply #1179 on:** 28 Dec 2010, 09:57 pm »

Panomaniac

If you are hoping that the poly sphere will radiate like a pulsating sphere, you are going to be sadly disappointed .
The affect would be the same if you placed the exciter on the outside edge of a2ft by 2ft flat panel.
The sound would come mostly from a small point on the opposite side of the panel edge.
And yes I have tried this,but after a lot of deep thought and a large pain in my head I decided to give these a miss.
I only mention these things as a warning of all the problems you will face ,and there are more.
On the other hand if you never try you never learn
sede