[jeffac]

On ya Jim,

Me bridesmaid ..again.. just when I thought I had THE solution in hand. 

Really fantastic news that you've found that cardboard makes a great panel material, as I have too from my dinky 'single exciter' ones that have had me dancing in the dark on more than the odd occasion. 

Where on earth did you get the 2/4' x 6' double-layered cardboard from. The guy 3 houses down works for 'Visy', Australia's major cardboard manufacturer and I've been thinking of calling in for while to find out what types they make in super-largest sizes. 

Time for a visit. 

And another win for the "mother-of-tone" - paper/wood/non-synthetic - got to be good.

cheers.. jeffac

[vaugi]

vaugi, foamboard is fine and many have used it. I would suggest that corrugated cardboard be used as your first attempt........about 3-6mm in thickness and as large a sheet as you can find(within reason).
Forget the exciters from that ebay product............they are very low powered, compact/slim versions and I would not recommend you wasting your money on them.
Go through Parts Express and get the proper ones even though the freight hurts.

Hi zygadr, thanks very much for the reply, I might hold off to see what these experiments with cardboard bring up and try that way.  Have got someone on board to bring some exciters across to save shipping, so looks like we might be getting on.. Again, thanks for the reply, appreciated.

Vaugi

[j gale]

Jeffac,  Here in Canada movers use double walled and shippers also use it. The supplier has it in sheets 6'1''(the way the flutes run) by about 12'.They just call them pads. Another company Uline offers the same stuff they call 275lb.test double wall in various sizes up to 48"x96". There is also a triple walled 1100 lb test 5/8" thick available. Packaging companies should have these items. One of the reasons that I reduced the number of exciters was the output from just one. I know the sensitivity numbers are bad but even one plays very loud.

[danieljtb]

Hi all  I have been reading this thread with much interest.  I have not decided whether to go with a single driver; the 15 wat 8 ohm, or two of the smaller 10 watt 4 ohm exciters.  i wish that there was a better data sheet including the sensitivity ratings.

a good source for the double walled cardboard is your local piano store.  I checked out their recycle bin and scored a nice 2x5 piece.  they have alot of board there but the rest was triple walled which i thought would be too heavy

A quick question  is there a sonic dissadvantage of wiring in series over against parralel?    If we are using the smaller exciters at 4 ohms and just two of them, series is the only option

[doug s.]

Hi all  I have been reading this thread with much interest.  I have not decided whether to go with a single driver; the 15 wat 8 ohm, or two of the smaller 10 watt 4 ohm exciters.  i wish that there was a better data sheet including the sensitivity ratings.

a good source for the double walled cardboard is your local piano store.  I checked out their recycle bin and scored a nice 2x5 piece.  they have alot of board there but the rest was triple walled which i thought would be too heavy

A quick question  is there a sonic dissadvantage of wiring in series over against parralel?    If we are using the smaller exciters at 4 ohms and just two of them, series is the only option

an amp w/a stiff power supply can handle 2 ohm speakers...

doug s.

[jonners]

A quick question  is there a sonic dissadvantage of wiring in series over against parralel?    If we are using the smaller exciters at 4 ohms and just two of them, series is the only option

 I've just been reading some interesting posts made here on Audiocircle by Paul Hynes. He gives convincing reasons for using parallel connection only, and he actually uses line array speakers where the parallel connection of eight B200 drive units gives an impedance of 0.75 ohms! He has posted a circuit of a power amp that will drive this load.
So the confusing results that apparently arise from adding extra exciters to a panel may be complicated in some cases by the electrical interactions that come about through series connection.

[jeffac]

Jonners,

As a B200 owner and having read Paul's take on the benefits of parallel only driver connection in his 8 x driver OB line array, I was thinking the same thing when I fixed and connected 4 exciters (30 cm spaced, 15 cm spacing top and bottom - not ideal and this will change) to my 120 cm x 75 cm panels last night. It was either fix 2 x 4 ohm PE exciters and hope my Charlize T-amp wouldn't protest against the 2 ohm load, or go 4 with 2 x parallel + series for a 4 ohm load. I went the latter......rushed and brain out of gear. Will try 2 x exciters on the other panel for comparison, maybe spaced similarly to jgale's new big panels with longer (~45 cm) distances to the top and bottom from each.

jgale and danieljtb, thanks for the tips on sources of large double-layered cardboard sheets

Sound of the one panel built last night. First a lower volume, with it positioned further out than my old right-channel panel, sitting on 2 wine bottle corks and propped against a stool, I couldn't make out whether it was working, sound across the panel .. but no apparent point source. At louder vol, sound field large, bass much more pronounced, drums, cymbals, bingos, vocals etc all believable. Only listened to a couple of Jack Johnson tracks as it was late, but very promising so far. 

More after a longer listen and when exciters are stuck onto my other large panel, for stereo. 

cheers.. jeffac

PS. One thing I forgot, whereas on an OB panel, sound cancellation occurs at the panel edges, I found a huge amount of 'quite nice' sound eminating from the openings of the cardboard corrugations at the panel top, apparently amplified because of the 120 cm length of each 'tube' and the small 2-3 m dia opening. Something to consider.. and which might not be ideal. Any thoughts on this?

PPS. Sorry…  the above is balderdash. I wasn't with it after sweating over the panel build in this incessant humidity. Sound cancellation is occurring at the cardboard panel top, it was very loud once my ear was slightly behind the top due to the close proximity of the top exciter. 

[jeffac]

jeffac...........so, .............it finally dried.............thank heaven's for that 

You try and get this stuff to dry overnight when coated inside and outside on a large panel ... under water... well almost, its been that humid here. Well it really only took about 2 full days but I wanted it 'really' dry, and I don't like rushing things.

Good news with scratch and ping tests with shellac, as per my tests and I think I made a comment a while back that pinging treated cardboard with it close to your ear was so loud that it could well cause permanent hearing damage..  so take care folks.

Now the cheap panel material is mostly sorted, who's the brainiac's out there who can work out ideal exciter number and spacing without that PITA expensive software ?  As I just scraped through physics I going to follow jgale's lead on my next panel.

cheers.. jeffac

In West Australia, ''PACK AND SEND'' is a company that has many branches all over Australia:
http://www.packsend.com.au

Getting a couple of 8 X 4 sheets is no problem as they have many smaller retail outlets everywhere.
Two of the above sheets in 6mm double ply is $36.00 (AUS).

If only it was that easy. All local branches here must use a different supplier as they only stock 3.0 m x 1.5 m sheets of "twin cushion" double ply board ($30 AUS), and although apparently very high quality, it's more like 8 mm thick. I'll go check it out but expect it might be a bit on the heavy side. 

[mightym]

Hi Guy's,

I just came upon this thread today, and have been reading here and on the other forum to get caught up. 

Something has occurred to me that may have been already covered, but I will ask and then go back to reading.

Has anyone experimented with added mass to the exciter(s) on a free-mounted ( no spine ) speaker to see if it would extend the bass output?  Possibly using the added mass on only some of the exciters?

If this has already been covered, I'll find out when I get to it, if not what do you others think????

John

[jeffac]

Welcome mightym,

Good idea but with the cheap exciters mostly used to date, without spine attachment, any extra mass hanging off their rear end is going to hasten voice coil sag and thus exciter life, as zygadr has experienced. Spine mounted, however, extra magnet grunt could add a little to bass. However, with larger panels, bass is pretty good from all reports, it's the extreme HF that has been somewhat a challenge, and cardboard now seems to be 'the cheap fix' for this.

cheers.. jeffac

[Russell Dawkins]

I don't have time to read the whole thread to see if this has been proposed before in quite this way, but I have a suggestion for an experiment.

Using corrugated cardboard for economy, make one panel of a representative size but with a frame around it (maybe 1X2) and any number of exciters over three - the more the merrier. Listen to it - record something played through it if you have the technology.

Then... make very narrow cuts between the exciters from one side of the panel to the other, halfway between the exciters so that each section of the panel is driven by one exciter at its approximate center point. Do not change anything about the exciters - same wiring scheme, etc.

Play the same piece of music and listen and, more effectively, record it from the same mic position as before.

My guess is that the bass and midrange is substantially improved.

The reason? Thinking back to the intentional chaotic movement of the panel - since the panel is not moving pistonically at any frequency above bass frequencies, and it may not be very coherent even in the mid bass, each exciter is to an extent fighting the random panel movement created by the other exciters. Splitting the panel the way I suggest will simplify the movement of each section and allow each exciter to perform more efficiently.
The narrow cuts should not create any significant loss in the bass, I don't think - in fact I would expect an increase in level and articulation in the bass range.

Just an educated guess. As I say, with cardboard, all you pay is time.

If this has been brought up already, excuse me.

[jeffac]

Guys,

I had a more relaxed listen to the big panel last night, couple of play throughs of Jack Johnson - On and On - with low bass to loosen up the exciter suspensions, and then on to Harry Manx - Wise and Otherwise followed by Alison Krauss - Lonley Runs Both Ways. Impressions....... the "Mothers of Tone" have landed. 

Bass is there a plenty, mids clear, HF there .... all with great dynamics. Instruments like fiddles and banjos really have natural tones, as with bongos etc, indeed all instrument textures are fantastic and vocals just beautiful. What is really amazing is the natural long decay of sounds, which irrespective of whatever else is being played, just fade naturally into oblivion. And this was still with only one large panel combined with my small single exciter panel and piezo cone panel. jgale ... you must be one happy camper. 

And speaking of piezo tweeter cones, as the corrugations of the cardboard fit a kebab skewer perfectly, these provide a neat and easy way of linking panels together.  So I've just placed a piezo tweeter cone panel on top of the large panel. Unfortunately everyone is still asleep here and the minute, but I can't wait to get a chance for a listen. I think that by the addition of extreme HF is going to be the icing on the cake.   Obviously the added piezo tweeter cone panel is just what I was using before and for testing and I'd trim it down to something smaller, neater and maybe curved and glue the kebab skewers in.

main Floorguard-treated cardboard panel with piezo tweeter cone panel attached

piezo tweeter cone panel lifted to show the kebab skewer attachment method


Unfortunately I'm off camping for the next couple of days so that second panel build to assess them in stereo will have to wait... more excuses 

cheers.. jeffac

PS

Hey jeffac................can you describe ''twin cushion''?..............

Double Wall Corrugated Cardboard Sheet. (also known as Twin Cushion) ...

[mightym]

Ziggy,

#1, Thanks for bringing this to the group ( The whole thing...)

I've come to the party late, I only finished reading the thread here last night.  I have also read much of what was written on the other forum too.

I'm in the process of designing one of these cheapo panels for myself so I can play too.

I'd like to describe my plan and leave it open for comments from the others.

I'll try not to run on and on....






This is what I came up with using Sketchup, it's aprox. 6' tall and the panel dim. is by the golden ratio.  I havent shown corner rounding, but plan on it.  as to panel support, i like the idea of using foam backer, only I plan to use 3/8" round, and inset them into the frame edge and use a couple on each of the 4 sides to retain the panel.  To avoid any voice coil creep the entire assembly can be inverted at intervals and all wire attachments will be to the center of the panel, a simple frame of 3/16th, or 1/4" bent steel that inserts into holes in the top or bottom strecher to support the entire thing ( not shown ).  I've not made a decision yet on panel material, I have a friend in the sign business ( so any of the panels tried thus far should not be a problem to get), but with recent developments Re: corrugated, I'm going to look about and see what's available locally.  I too have read up on the " Mother of Tone", and I'm thinking that since we're audiofools here we should be using C-37 Lacquer, or at the very least Dammar Varnish to stiffen our corrugated.

As to the choice of drivers, I'm poor, so it's the $5/pr. PE's for me. The big Questions that remain in my mind are: Placement, and whether or not to add a piezo to the mix, and where to apply it.

Regarding Placement of the Exciters:
     Have any experiments been done placing the exciters in a Fibonacci sequence, starting from the center and maintaining symmetry either side of the center, with the Piezo, if used, residing in the center.

I plan to use individual Cat 5 wires to hook-up the exciters, in a manner to yield a final impedance as close to 8 Ohms as possible ( I'll be trying a couple of different amps, and the Tubers don't like low impedances ).

That's as far as I've gotten to this point, have I forgotten anything?  Those who've been experimenting, soes this sound like a viable start?  And again thanks to those who've boldly gone where no man......

John

[j gale]

Just a couple of comments. Ziggy get yourself some double layer cardboard!!! Most of your concerns about high frequency detail will vanish. Mightym go with the double layer. It's still only 1/4" or 6mm thick, much more rigid and one layer has the flutes much closer together. I tried the golden ratio as well (pretty close to jeffac's size) I couldn't hear any advantage over my 2'x6' and so went with that because 30" plus width is just too big for my room. The 2 for $5 are the deal of the century. Their low price has nothing to do with quality or performance. I believe that they are probably the best of the lot. I rounded the corners of mine as well and although not a huge difference I believe an improvement. Cat 5 works well but will make noise if not secured. I really believe that cardboard (DOUBLE) is the answer. Natural tone and as Jeffac said decay. Big step up from Gator. Can it be enhanced by treatment? It will be fun to find out. PS I think 4 exciters on a 6' panel is better than 8.

[BowerR64]

Is anyone using these on a surround sound receiver?

Also has anyone tried pushing dimples into the front? like a golfball, maybe in certin spots like the corners that may fade in sound or somthing?

Maybe right in the center infront of the transducer? or what about round foil disks then push the dimples into the panel? might create a tinny cone like spot that may gain some higher frequencies?

[bobloblob]

A comment on Jeffac's panels - bending the sides not only helps provide support for the panels, it stiffens them as though they were mounted in a two-sided frame, so the sides of the panel are no longer free to flap.  This should also mitigate much of the need to round the corners.  Maybe Russell Dawkins' comment about using a frame around the panel may also work, based on Jeffac's success, though if one bends the panels then only a stiffener at top and bottom would be needed to test this out.  Of course, with a tall enough piece of cardboard, if one has the sides bent already, one need only bend the top and bottom edges also to see what effect this has. If the bent edges were fastened to each other also, this would provide the same or more stiffness as a regular frame would.  Keeping the sides constrained should get this operating in more of a DML mode, since there would be no way for the sides to "flap", which would indicate bending waves. 

[mightym]

Mightym go with the double layer. It's still only 1/4" or 6mm thick, much more rigid and one layer has the flutes much closer together. I tried the golden ratio as well (pretty close to jeffac's size) I couldn't hear any advantage over my 2'x6' and so went with that because 30" plus width is just too big for my room. The 2 for $5 are the deal of the century. Their low price has nothing to do with quality or performance. I believe that they are probably the best of the lot. I rounded the corners of mine as well and although not a huge difference I believe an improvement. Cat 5 works well but will make noise if not secured. I really believe that cardboard (DOUBLE) is the answer. Natural tone and as Jeffac said decay. Big step up from Gator. Can it be enhanced by treatment? It will be fun to find out. PS I think 4 exciters on a 6' panel is better than 8.

Thanks for the suggestions.  I am basing my panel mounting on your work, with some minor redesign


3/8" closed cell foam concrete backer rod, let into the frame and slightly compressed to hold the panel, no glue.

I'm going to try the double corrugated, I hope I can find some locally, at a packaging house.  I'd hate to try to ship the stuff, liable to look like a potato chip by the time I got it...

I'll probably go ahead and run the full width, as I have the room where I plan to use these.  I may change my mind when I start to assemble the frames though, they may "grow" and I can make'em narrower easier than makin'em wider.

Do you recall the radius you used in rounding your corners?  After watching the video of the Sand vibrating on the table, it seems a couple inch radius would be sufficient to me.

As to the Cat 5, I planned to wrap it around a dowel like a spring, and then extend the coil to avoid it's acting as an inductor, and keep the wires from flopping about with a 1/2" or so spacing from the panel back. I hope that description conveyed my mental picture, I don't think I can draw it in Sketch-up 

I was actually thinking 5 exciters per panel, the panel will be a little under 6" tall, and with a spacing of 8",13" ( ~ Fibonacci) from center like this


Of course the positioning of the exciters is subject to modification too...

Glad to know the inexpensive exciters will work just fine, I had gathered that from reading the thread, but reinforcement doesn't hurt, if I had to buy the more expensive models, it would delay the project while I scraped up the dough.  I can pick up 6 pr. out of my lunch money. 

On a different topic, how would one wire 5 exciters 4 Ohm exciters to get somewhat close to an 8 Ohm impedance?

John

[BowerR64]

Guys,

I had a more relaxed listen to the big panel last night, couple of play throughs of Jack Johnson - On and On - with low bass to loosen up the exciter suspensions, and then on to Harry Manx - Wise and Otherwise followed by Alison Krauss - Lonley Runs Both Ways. Impressions....... the "Mothers of Tone" have landed. 

Bass is there a plenty, mids clear, HF there .... all with great dynamics. Instruments like fiddles and banjos really have natural tones, as with bongos etc, indeed all instrument textures are fantastic and vocals just beautiful. What is really amazing is the natural long decay of sounds, which irrespective of whatever else is being played, just fade naturally into oblivion. And this was still with only one large panel combined with my small single exciter panel and piezo cone panel. jgale ... you must be one happy camper. 

And speaking of piezo tweeter cones, as the corrugations of the cardboard fit a kebab skewer perfectly, these provide a neat and easy way of linking panels together.  So I've just placed a piezo tweeter cone panel on top of the large panel. Unfortunately everyone is still asleep here and the minute, but I can't wait to get a chance for a listen. I think that by the addition of extreme HF is going to be the icing on the cake.   Obviously the added piezo tweeter cone panel is just what I was using before and for testing and I'd trim it down to something smaller, neater and maybe curved and glue the kebab skewers in.

main Floorguard-treated cardboard panel with piezo tweeter cone panel attached

piezo tweeter cone panel lifted to show the kebab skewer attachment method


Unfortunately I'm off camping for the next couple of days so that second panel build to assess them in stereo will have to wait... more excuses 

cheers.. jeffac

PS
Double Wall Corrugated Cardboard Sheet. (also known as Twin Cushion) ...

Man i hope the Chinese dont see this thread, this could bring a whole new meaning to sound in a box. They could sell a bass cabnet and some transducers and then you use the box for the speakers! lol

[j gale]

Mightym  We have all stayed away from having an exciter at the panel centre based on what we can gather from NXT. It costs nothing to try. I would recommend trying 4 without the centre one 1st, then add it and see what happens. My 4 are wired 2 parallel pairs in series for a nominal 4 ohm. Measuring, the meter says 4.6 ohm for the combination. My 300b mono blocs don't mind. I think it's a pretty stable load. I've mostly used a virtue one tripath amp to play with these. Corner rounding-- I just arbitrarily used a QT or litre paint can as a pattern to run my Knife around. The result looks good.

[mightym]

Mightym  We have all stayed away from having an exciter at the panel centre based on what we can gather from NXT. 

I just arbitrarily used a QT or litre paint can as a pattern to run my Knife around. The result looks good.

Thanks, j gale.

It's on my list to wade through the NXT info, I bookmarked a link earlier in the thread, that kind of technical reading usually makes my eyelids very heavy...

I got quart cans...    ( but I have a compass too)

This just in:  What kind of edge treatments are people using on Corrugated?  None?

John