[zygadr]

Yes, good to hear from you emailtooaj!!
Well done on your panels they will look superb when finished.
Thanks for sharing the fact that closing off or bordering the edges of the panel material is not good for the sound. I did not know this and will have to rethink my mounting method!

You speak of ''foamed 3M tape'', but I have never used that kind of tape. The 3M VHB (very high bond) that I use is not a foam tape........it is clear, thin and ''gummy''........very sticky stuff and is what NXT recommends as the correct tape to use with these exciters.

j gale, It looks as I too will be using cardboard for my panels. I was interested to note that you also felt that the el-cheapo exciters sounded better than the high power Daytons. I thought this too at first. However you may have noticed that the suspension on the Daytons is VERY stiff and it takes quite a while for them to ''break in''. After about 20-30 hours of solid play time, I found that the sound became louder and crisper and quite dynamic........interesting eh?

Anyhow,great to see that experimentation and progress is still being made.It's all worth it in my opinion as these panels have a sound that is truly special.........and.........addictive!!

[b2m]

Concerning the adhesive tape: My guess is you use 3M 9473 because it is better suited for rough surfaces. Given you have a very flat vibrating medium, wouldn't it be better to use very fine sandpaper (1000 to 2500) to flatten and polish the surface of the exciter and use 3M 9460 which is just 0.05mm thick?

[zygadr]

Well the Reboard has not showed up........typical

I have two 30 inch X 65 inch, 4mm single cushion corrrugated cardboard sheets arriving at my home today. They will be the last panels I will be making after hearing what the smaller C.C. panels operating at the moment can do.(incredibly good sound!!).

This time around I am not going down the vertical, evenly spaced exciter positions. I will use the Monacor 4 exciter ratio position as per the link I posted. They will be free mounted at first, then, shortly after, mounted to an odd shaped spine and the panels will be free floating away from the frame work edges.

Not sure whether I will be treating the C.C or not at this stage. Listening tests will be the deciding factor here.
As far as I am concerned,C.C. is even more natural than wood which for some reason had overly bright highs and upper mids.
The C.C. has such a realistic tonal range that it amazes me and I am certain that this is without doubt the panel material to end all panel materials!

I am still asking myself how I went off the rail and disregarded C.C. as a contender for a good sounding panel? I guess my first experience with it was the use of thicker 7mm ''twin'' cushion stuff which clearly indicated what this technology offered in it's unique sound quality.
Of course, there had to be some thing better???? ............and the journey and spending started
Gatorboard, Corflute, E.P.S. and wood were all tried. Gatorboard had no highs (big problem), Corflute did not sound right either, E.P.S. was just too harsh and plastic sounding, wood had the best sound yet, but also had problems and weighed too much.
All this over such a long time only to come back to the simplest and cheapest material : C.C. . Oh well, I guess that's the way that experimentation goes if you are to succeed in finding a solution to the biggest problem with these panels and the associated technology.
Along the way, others have discovered methods to mount the exciters correctly, ways of dampening panel resonances and other minor anomalies..........thanks to all for sharing!

It will be intersting to see how much of a difference the 4 position placement that is indicated in the Monacor/NXT document will make compared to our ususal in-line vertical configuration. I know that using a single Dayton exciter in the number 1 position on a smaller sheet of 3mm C.C. is the best sound I have ever obtained from a one exciter/small panel test. There may be something to these carefully calculated positions...........who knows? ..............we'll soon find out!

[b2m]

As my local carton dealer had no Reboard in stock, jsut something similar, but in 10mm, I resorted to 2.5mm CC, but double cushioned (I guess this is what you call it when both sides are flat, single cushioned is when you can see currogation). I mounted two Daytons according to the monacor paper. I like the sound but am under the impression that there is some room for improvement but can't put my finger on it yet.
I bought some other stuff, too, thicker CC, thinner CC and some kind of plastic, which was really bad.
How does you single cushion CC hold, everything I saw would roll up.

best regards
b2m

[zygadr]

b2m, the twin cushion C.C. is not really much good from my experience. The extra layer kills off a lot of the vibrations that are required for the high frequency output, plus it is also heavier which does not help.Twin cusion is flat on both sides also, but has two internal layers of corrugation - one large and one small. If you don't have flat faces on both sides, then you have something different.

To make things a little more complicated, there is good quality C.C. and poor quality stuff also. The good stuff has a nice brown kraft paper outside where the bad stuff looks a bit bleached in colour.The poor stuff is very soft and easily damaged.

However, as you have 2.5mm thickness, it should sound reasonably good..............what size sheet do you have?

The stuff I have is 4mm thick single layer and is fairly rigid - it can stay upright on it's own without looking like it's going to collapse.Of course the bigger the peice, the more chance of the cardboard bending.However this does not matter when held up in a wooden frame of some sort.

Thicker than 4mm is not recommended and I think it's the thickest single cushion thickness available. You can go thinner but the panel needs to be smaller also. If you have seen C.C. that can be rolled up it is no good - useless.........sounds like one sheet of corrugation with no faces?

I will test the C.C. I have tonight and will report back.

Keep looking for good quality, strong, single cushion 4mm b2m............they use it everywhere.
Here is a link showing the different types of C.C. :

http://theboxman.com.au/stock-choices/

[b2m]

Hey zygadr,

allright, then I misunderstood what single cushion means. So I'am actually using single cushion CC right now, 2.5mm 70cm*100cm. It seems to be of reasonable quality as far as i can tell but it may indeed by a little too big, when I turn my DTA-1 way up songs with lot of bass move the panel around. I'll look for reboard which seems to be stiffer an may be usable at bigger sizes.

We'll see.

[zygadr]

Hi b2m.
The size you have is o.k. The panel moving around is normal as you have not mounted it to a frame yet. The movement actually enhances bass performance.

I'm not sure about the Re-board?..........by all means get some if you can and check if the highs and lows are as good as the C.C.

I peeled back the face of one corner of the Re-board sample I have and noticed the same corrugations as C.C. but in a vertical position, not horizontal. It is very densly packed with these corrugations which are twin cushion, glued side by side all along the face of the board. This makes the density and weight and stiffness considerably higher than C.C.
Now, this can be good and bad : good - because you have a stiff board, bad - the internal corrugations are so dense that they may overdamp the panel? and the weight of the Re-board is creeping up as a result.
Something to be aware of.

[b2m]

I listened to my 70*100cm speaker with two exciters for some days now and I gotta say it is indeed a really fine sound. I just asked for an offer for re-board from my local dealer. If it is at least as good as CC, I'll build two bigger speaker with 4 exciters each for my living room.

We will see!

best regards
b2m

[zygadr]

I have mounted the 4 exciters on the C.C. as per the Monacor placement guide and had a good listen to single and twin cushion sheets.

The single cushion had quite a bit of self-panel noise and had some coloration that was quite noticeable.
The twin cushion was expected to sound ordinary but here is where the surprise came in!

I'm not sure whether the Monacor placement of the exciters was making the difference in producing better sound quality than I have experienced in the past with twin cushion,but the sound was very, very good. There was NO noise that I could detect and definately no ''cardboard'' coloration as was heard on the single cushion sheet.

The whole idea was to compare the single with the twin cushion last night and it wasn't long before I decided to replace the single C.C. with twin C.C. to have a stereo pair.

The twin cushion panels, with the new Monacor exciter positioning produced a very different presentation of the sound : solid, powerful, dynamic, good bass and very natural but not overly prominent highs.........realistic, as heard in the concert hall type sound.I would be quite happy to live with this sort of sound quality.........no problem at all.
Do I need to treat the panels with some type of coating or edge treatment?..........I don't think so.

At the moment the exciters are free mounted and not held with a spine. That will come soon as I work through some ideas I have.

Well, there you have it. It seems that there may be something to the Monacor placement diagram after all as I don't recall having the same quality of sound as a straight vertical exciter placement in the past........especially with twin cushion C.C.

[zygadr]

No comments?..........sort of expected that
Who would have thought that this project would turn around 360 degrees and end up with plain old ''cheap- ass'' C.C. as the panel material of choice? After all..........it's only crappy cardboard, cheap (oh......I aready said that)doesn't look like anything special,and there must be something out there better than this rubbish?!!!

When you sit down in your listening area, turn up the volume and are confronted with this huge open, wide vista of incredibly natural sound that makes you forget about the speakers and the rest of the system, it can't be good can it?
I mean your speakers are only two sheets of common old C.C., so they can't sound any good.....surely?

Having spent at least a couple of hundred dollars on Gatorboard, VH EPS,various thickness Plywood,Corrugated plastic, a big jar of Shellac flakes, and some coatings such as Dammar varnish, Polyurethane varnish and even made my own coating using a home made violin varnish sourced from the internet .......it's come down to C.C.!!!!!.....and it's uncoated and at present unmounted!

I guess those guys on the B.Y.O.B. site were right all the way along. Paper and/or wood has an important role in the world of audio reproduction. At first I was very dubious about their ''Mother of Tone''philosophy, but in the end after all the opposite materials and methods, I have to say that I agree with them.

Where do we go from here?............in my opinion, nowhere (well,.......there may be improvements as time goes by?)

We can now crank up the volume without frying the exciters thanks to the Dayton high power units.As far as I am concerned, we HAVE the panel material - one that is easy to get, very affordable and sounds great.

 I am fascinated and delighted with the sound I am getting. These two peices of C.C. transport me to the concert hall, jazz club or whatever. They do many things that other ''high end'' speakers can only dream of. Are they perfect........no............but they sure come close.

It has been a long journey, but I am proud to say that I started this madness, made a lot of mistakes, made a lot of freinds (and some enemies )and made an affordable panel speaker that rocks with the best of them. :)To all that have contributed with their input and thoughts, I say thank you. Without ideas it would not have been possible.

Here's where it all started : http://www.stereophile.com/hifinews2006/092406popeck/index.html

[b2m]

Hey Zygadr,

well, I read your comment but trying doublecushion CC sounded worse then single cushion in my case. I'm still looking forward to reboard due to the simple fact that it should be easier to use in big dimensions and doesn't need as much reenforcement using a frame. Unless it sounds worse, that is.
I'm happy that you found a speaker that satisfies you. Do you have an idea how to expand the monacor exciter placement for more than 4 exciters? I don't know if this will be necessary, seeing that 4 should be plenty loud, but just in case?

b2m

[zygadr]

Hi b2m.
The difference between the single and double cushion is a trade off : single is slightly louder, a bit clearer, but it's flimsy/bendy nature causes other issues.The double cushion is not as loud, slightly less transparent, but has a ''solidity'' and forceful dynamics with better bass.
It's all to do with the stiffness of the panel which differs between the two.
Also, I don't know if your C.C. has the same, but my stuff has a plane flat side and a slightly raised series of vertical lines or marks on the other. Plus my cardboard sheets have been cut with the internal flutes running up the long/tall side of the sheet.Some sheets I have seen are cut the other way(horizontal flutes). Anyhow, by mounting the exciters on the vertical lines side and the fact that the sheets are cut with the flutes vertical may be two factors that affect the sound quality as a result?
This is pure speculation though.

I too am looking forward to hear your impressions of the Re-board. From the sample I had, it has a totally different sound that I was not too impressed with but who knows........two large sheets may be quite different?

I was also wondering about using more than 4 exciters. I have no idea how to do this however.The Monacor placement has been modelled using NXT's computer software I think. If that's the case, it will be difficult to find out unless the software is purchased and I believe it's expensive and complicated.

Using 4 Exciters in a large room with big panels of C.C goes pretty loud over here and I don't see the need for more at this stage.

[b2m]

Hey zygadr,

thank you for your input once again. It's really hard to come up with explanations on the whole matter, seeing that seemingly everyone here (including me, obviously) has no scientific background in the matter to calculate what material would be best. So we'll stick with thy olde ways and just trial and error, I guess. Maybe I'll land at CC myself, if Reboard doesn't wound up being as good as I hope, I'll just try different CC-types and sizes.

I guess I'll stick with four Exciters and wait until more powerful exciters are on the market to upgrade. At the moment I spend my time thinking about how I can mount the exciters to give them support (on my 2.5mm CC, one already fell off) while I try to keep the panel as freefloating as possible. Are there pictures on how you managed that? To build a complete frame seems like unnecessary work to me. We will see!

[zygadr]

The problem with these heavy,'' plate/foot'' type exciters is that they require a rigid flat surface to adhere to if you are using double sided tape(which should be 3M VHB).
What seems to happen is that as the C.C.(especially 2.5mm)bends each time it is handled or even bends backwards due to the weight of the exciters, they are subject to pressure which causes them to slowly delaminate from the C.C.
This is one of the reasons why I chose the stiffer twin cushion C.C.
With thin plywood, I actually damaged two of the exciters due to the bend in the plywood.

[mkstat]

...

[zygadr]

Thanks for the great link m!
This may come in handy at some stage later

Meanwhile, as the exciters are burning in on my panels, there is more solidity or ''power'' becoming evident. Together with this is an increase in output which I was sort of expecting as was the case with the el-cheapo exciters in the past.
Overall, the sound as mentioned before, remains very natural with no obvious or objectionable tonal aberrations.

I will soon need to construct some form of supporting structure for the exciter magnets and allow the panel to freely hang within some sort of frame.As the exciters are no longer in a straight vertical position, this needs some thinking through

[zygadr]

Added two standard exciters to the recommended placement suggested by Monacor for 4 exciters.The placement had no relation to any software formula placement..........I simply placed the two exciters above and below the Monacor configuration - in the middle of the panel, top and bottom.
Noticed a marked improvement in output and mid/high presence. just goes to show that that the ''el-cheapos still have use use in this project  LOL!!!!

I will be eventually be using the 4 mm single cushion C.C. as it is clearer and lighter than the twin cushion stuff.

As suggested by J gale, the injection of Shellac will do more good than harm................especially as I have come across this little wonder at my electronics store :

[zygadr]

Over 180,000 views on this topic and everyone is silent????....................way to go guys!

[zygadr]

Some of you may be aware and some may not, some know and some refuse to believe. That is your choice of course.

A few years back I started experimenting with a new technology that caused ''bending waves'' to excite a large, lightweight panel of corflute using an old piezo speaker element. This was on another site/forum that were at first, interested and helpful.
As things progressed and proper exciters became available, people started making speakers that produced a sound that was far too good than it should have been. Then came the ''slammers, stirrers and arm chair theorists. One of my own countrymen had nothing constructive to add other than suggest a sexually offensive remark which brought the worst out of me............it made me racist for a short time, purely in anger as I am not racist .......at all!
The result of all this was my ejection from that site. Fair enough, I broke the rules and paid the price.

What does upset me is that all my work and effort was taken for granted by some and totally dismissed by most others as science fiction even though they had not made any attempt to try what I had generously shared with them.

I have had people from all over(including internationally)come and listen to how two lightweight sheets of various materials can sound as good as any panel speaker out there with very little outlay.They walk away in disbelief (looking for hidden woofers and tweeters or other loudspeakers in the ceiling or under the couch)not willing to accept what they have just heard.

It is very important to understand that after so much experimentation, blood, sweat and tears, we DO have a fully working panel loudspeaker system that is easily classified as ''HI-FI'' with the currently available exciters - both high powered and standard.

In my opinion, I achieved what I started out to do.No longer can I listen to forward firing direct radiators (with or without boxes)and horn speakers. They simply sound like ''SPEAKERS'' and there is no mistake in that. The NXT panel sound is, once heard, a sound you will never forget, and will allways go back to again and again.

Rob.

[hblester3]

Ziggy I understand what a break thru this is as I listen to my panels, please do not get upset or discouraged by lack of replies just as you stated the number of views and length of this topic does nothing but show that people are watching some are not vocal or as dedicated as you. It could be that every time I tried something you suggested that I was amazed by the sound. I still have eps panels with six exciters per panel with the exciters mounted to a spine, free floating exciters also mounted on plywood and cardboard. Most that listen can not believe the sound is coming from eps, plywood or cardboard. Others have purchased exciters and started making speakers. You also inspired me to build a gain-clone kit, simply amazing. Keep posting as I don't think you really know how many check this forum every few day to see what is new. As for me will soon will get large pieces of cc and try the Monacro placement.

Hubert
Again THANK YOU!!!