[BowerR64]

Now i know how that smokin joe off youtube got his sound using that setup he built. He ran the panels threw the sub and adjusted the sub cutoff frequency to fill the gap.

Most subs will go from like 60-120 right? surly his panels could hit 120hz right?

I wasnt sure how he was doing it but i understand now.

Running a surround sound receiver will do somthing like this as well using the "small" speaker setting.

[j gale]

I don't think Smokin Joe is getting any where near the sound that we are. I have an IB sub in my ceiling that will shake the entire house. With my panels I don't need it. I think any edge treatment would only have cosmetic value. Eventually I will try Bud Purvines enable pattern around the edges. I have experienced good changes from that with several drivers. It's another controversy but don't knock it if you haven't heard it for yourself. Many jaws dropped at one of Planet 10's get togethers where identical speakers were compared only difference enable and not. It was blind switching between the two speaker systems because they were covered.

[j gale]

Treating a large piece of cardboard I suppose it could be kept from warping if it was sandwiched between a couple sheets of plywood or mdf, the corrigations  done 1st. and kept there until dry.

[BowerR64]

Ive seen this type of cardboard before and i thought it was maybe 2 things. ! it was recycled cardboard or somthing or 2 it had come from over seas on a boat and was still kinda soggy.

[BowerR64]

Are you guys using more then 1 transducer to change the impedance or does it increase or decrease the sensitivity?

[zobsky]

Using multiple transducers can change the impedance and sensitivity depending on the wiring.

Also, the size of the substrate will affect resonant frequency.

[jeffac]

Gee there's been some good posts in the last couple of days, I should go camping more often

zygadr's - impressions of difficulties/potential benefits of treating cardboard with stiffeners- right on. Take home message, get good quality double-layer cardboard and worry about this later unless curious like me, and as my single layer 4 mm corrugated cardboard was average quality at best and thus treatment was great for stiffening it in this case

jgale - again good advice to make panels, listen, and then if HF is a concern and you're dissatisfied, try a piezo tweeter cone either surface mounted, as I've tried, or mounted behind the panel, as zygadr has tried. They seem to blend absolutely seamlessly either way 

bobloblob - comments on panel edge bend overs as I tried will help panel linearity, both vertical and horizontal, and thus overall rigidity, something to seriously contemplate, both for sonics, and depending on how you indend to mount/frame the panel

jgale - has tried different panel materials, shapes, exciter numbers and spacing – thus my next panel will follow his recommended panel size (1800 mm x 600 mm) and 4 x exciter spacing. And after listening to mine in stereo now for a night/day, since having finally built the second panel, I also like the idea of keeping the panels no more than 600 mm wide to maximize imaging, unless you have a very wide room.

stereo panels, at last, with trimmed piezo tweeter cone panels
4 x exciters parallel series connection for 4 ohm as per jgale, piezo cone wired in parallel
Cat 5 stranded cable strands used for hook up
Just propped up currently with stools and anything the right height on the stool seat to rest squarely behind the second exciter from the top. Gotta do something better soon

super quality 6-7 mm double layer cardboard from Pack&Send
comes in 3 m x 1.5 m sheets ($30AUS) so good for 2 x 1.8m and 2 x 1.2 m panels plus off cuts. Very pleasant folk to deal with over here, sorry to hear that they were a PITA over your way zygadr 


Sound …… friends visited for lunch today, and all they said is WOW, you gotta start making and selling these. And… if you intend making more, can we have these……   

They sound quite different to normal coned speakers.. even in OB, more on this after a bit more familiarity and note taking.

cheers.. jeffac

[mightym]

Good stuff jeffac,

only one question regarding the double corrugated, I was inder the possibly mistaken impression that the corrugations were perpendicular to each other, providing panel stiffening.

Did I just totally miss something in my reading here?

Could we possibly see the backside of your panels too?

John

[BowerR64]

Good stuff jeffac,

only one question regarding the double corrugated, I was inder the possibly mistaken impression that the corrugations were perpendicular to each other, providing panel stiffening.

Did I just totally miss something in my reading here?

Could we possibly see the backside of your panels too?

John

Cool idea, what if you make your own double corrugated and put them perpendicular to each other like you said.

[bobloblob]

I mentioned crossing the cardboard in an earlier post, but I don't think anyone has tried it.  May or may not help, but I think it's worth experimenting with.  I have seen rolls of corrugated cardboard with only one side faced - the corrugations are exposed on one side, givng it flexibility.  Thsi may be easy to bond to a sheet of regular cardboard faced on both sides.  The advantages would be that with the one-sided cardboard it would be easier to saturate the corrugations with a stiffener, and it would reduce the amount of material in the finished panel, since there would be one less face.  Most things used to stiffen the cardboard will also bond the sheets together, so glue won't be needed.  I think the idea of placing the panels between two sheets of plywood or mdf is a good one, but wax paper or something will need to be used to prevent adhesion to the mdf/ply, and the wax or waxpaper will have to be cleaned off the panels afterwards.

The main reason for the stiffening liquid is not so much to decrease the flexibility of the panel over its length and width as it is to decrease the damping factor of the material front to back - in other words, to help transmit sound through the panel.  This is why one would want to get material used to stiffen the cardboard down into the corrugations too.  Length and width rigidity is an added bonus.

Also, I keep having this thought about piezos - has anyone tried just placing one of the lemon-squeezer piezos free-standing behind the a panel, facing up or to the side?  Since nearly all the sound of the instruments is delivered by the exciters and the piezos more or less are giving that sense of "air" or hall ambience, a piezo set behind a panel and unattached may be enough to get the job done.  This is an experiment with no downside, since you don't have to attach or unattach it, and don't have to take it out of its housing.

Godzilla, on other sites, likes to use piezos this way.  Here are two links to how he uses them, and how he improves the sound of his piezos:

http://www.zillaspeak.com/pioneerb20-piezo.asp

http://www.zillaspeak.com/piezo.asp

[mightym]

  I think the idea of placing the panels between two sheets of plywood or mdf is a good one, but wax paper or something will need to be used to prevent adhesion to the mdf/ply, and the wax or waxpaper will have to be cleaned off the panels afterwards.

I would use polyethelyne sheet (what we called Visqueen growing up ) I don't know of anything one might concievably use to stiffen the corrugated that would stick to the plastic.

[bobloblob]

Polyethylene should work well.  I don't know if many have access to large enough sheets.  I'm not sure, but think that some clear packing/weathersealing sheets (as is used to seal motorcycles and pianos in their crates, e.g.) may be polyethylene?  I sometimes use stiff polyethylene film to seal off polyester (aka boat resin) repairs, and it peels off relatively easily.  Epoxy sticks to it somewhat, but will still release with a bit more pressure.  Also not sure, but I think some of the plastic wraps for food may be polyethelene -Saran brand is/was polyester (aka mylar), but I think it is the only one that is.

[mightym]

Polyethylene should work well.  I don't know if many have access to large enough sheets. 

Any big box store has plastic sheets a Lowe's Example:www.lowes.com/pd_16905-18632-RSCC410-25C_4294865824_4294937087?productId=1040769&Ns=p_product_quantity_sold|0#&pl=1&currentURL=/pl_Sheeting%2B5F%2BFilm_4294865824_4294937087_?newSearch=true$ddkey=http:SearchCatalogDisplay$Ns=p_product_quantity_sold|0#

Sorry about the giant link,  UGH.

[BowerR64]

What about leaving the single side courrugated cardboard like it is and glueing it to a single courrugated sheet leaving the one side exsposed at the front.

With the courrugations out i would think that would help move iar some what.

Would be cool to try that and mix them around, say have the corrugation running horizontal in the center and then vertical around the edge like trim or somthing.

[jeffac]

only one question regarding the double corrugated, I was under the possibly mistaken impression that the corrugations were perpendicular to each other, providing panel stiffening.

mightym, all the double-layer cardboard I've seen so far has been made like this... and as jgale has described for the cardboard used for his latest and greatest panels. Envious mate In fact I like the differing thickness laminates (2 mm and 4 mm) with corrugations offset for both rigidity and spreading any resonant frequencies that could establish due to uniformity...  and this is the non-conformists OB thread.... 

o.k :  ...............I give in..............gonna go to Pack and Send and get me some corrugated cardboard sheet

Stay calm Clint and keep that 45 in its holster Fantastic quality cardboard and if anything like the sample I picked up... my guess is it will be absolutely amazing panel material even naked... perfect for the job…. I can't wait to get a sheet of the stuff home, just need to find a way of getting it there in pristine condition.

cheers.. jeffac

[mightym]

I'm not attempting to change the subject here....

I'm also just 'spitballin',  somewhere in the recent past on this thread or the other one "over there", someone was having ~good results with extruded polystyrene foam core material ( IIRC ).

While searching for a double corrugated supplier, I saw rolls of kraft paper, which is basically what corrugated is made from, in different widths, and weights ( thickness of the paper ).

My little mind made note of these two seemingly unrelated tidbits, and I went on about my business.  Well this morning I woke up with this crazy idea, if we're going to try to laminate corrugated anyway, why not laminate the EPS board with a layer of kraft paper on either side, then apply your treatment to the Kraft ?  As above, I'm only spitballin, so don't flame me, but is it worth thinking further, or experimenting?

John

[j gale]

Whoa, back up. I see you guys setting off to build your own cardboard when you haven't even heard the double layer stuff easily available. It's too soon for this discussion. First have a listen to the double untreated.

[jeffac]

A question however, ..............how do you know if it's of superior quality?........is there an easy visual/mechanical way to check, or is it graded?

It is simply beautifully made, as you can see from the pic... dense and smooth cardboard faces and the most rigid thing I've had in my hand since this morning 

Seriously, if near identical in quality to the double-layer CCB that jgale has used for his latest large panels, this will be a large part of the secret to why he is over the moon with their sonic performance. However, so we have the technical side covered as to the HIGHEST QUALITY DLCCB specifications/codes, I'll also ask this here for the 3 m x 1.5 m sheets I can get. Barry at my local P&S outlet still had the box the sheets were packed in ... so maybe this will provide the needed info.

Agree with zygadr and jgale that we have the best MOT panel material now sorted.... so lets stop fretting about this and move on to BEST exciter spacing, mounting and framing solutions, and our job will be done. jgale is leading the way here with his good woodworking skills and ingenuity.  A FEW HAPPY SNAPS WOULD BE NICE JIM. 

cheers.. jeffac

[j gale]

Jeffac,  Looking at the pic you posted of the cardboard edge with the ruler it appears to be exactly what I have. The fairly decent frames I have still have the Gator in them. My cardboard is mounted on some junk material so not worth a pic. I will eventually get something better looking,but not in a hurry. I also want to check on what else is available in the cardboard line here. They have some honeycomb stuff but it's 2.5 cm thick and the honeycomb is coarse. Eventually all of the reasonable possibilities will be tried. I look forward to the impressions of a few others once some more full sized cardboard panels are up and running.

[jeffac]

There certainly is a lot more to cardboard than meets the eye 

From enquiries at Amcor here, it seems to be pretty much made to specifications requested, skin thickness, amount of recycled paper in the blend (less = stronger in general), thinkness, size, etc etc.

So .... very hard to compare. 

I've come across this Xitex dual flute board (patented and only available locally... from what I've read) that looks interesting, very light and very rigid.... apparently... again various types are manufactured to requested specifications


more info here
http://www.amcor.com/products_services/xitex_corrugated_board.html

Paul.. very accommodating guy here.. has offered me "free" samples cut to my liking from a sheet approx 3 m x 1.5 m in size (quality unknown at this stage and he's checking the size for me so I can advise him on the cuts), ready for cutting and pickup Tue next week 

And another couple of links on .... cardboard.... who would have thought cardboard could be so interesting 
http://www.shortrunboxfactory.com.au/boxes.html
http://www.kebet.com.au/specs/materials.php#boardapp
http://books.google.com.au/books?id=Wh_KqCXPn3gC&pg=PA574&lpg=PA574&dq=Xitex+corrugated+board&source=bl&ots=UuWaPiRywY&sig=OdCPG_HgI560dXqjOgeiV-944Mc&hl=en&ei=mihhS8XQIc6TkAXxsdHpCw&sa=X&oi=book_result&ct=result&resnum=6&ved=0CBsQ6AEwBTgK#v=onepage&q=Xitex%20corrugated%20board&f=false

cheers.. jeffac