Not exactly. I have had an idea how to salvage them though.
While patching them up, I have decided to abandon the removeable back idea, and simply cast a concrete back onto them the thickness of the length of the bolts. It will mean working through the front hole, but it should strenghten every thing up.
It looks like I will buy a tin of liquid roof repair and pour it in and roll it round.
Good old blue tack to hold the baffle in untill Im done tweaking them.
While patching them up, I have decided to abandon the removeable back idea, and simply cast a concrete back onto them the thickness of the length of the bolts. It will mean working through the front hole, but it should strenghten every thing up.
It looks like I will buy a tin of liquid roof repair and pour it in and roll it round.
Good old blue tack to hold the baffle in untill Im done tweaking them.
interessting idea, afaik there are two opinions here in diy-speaker-building-germany:
- great idea to dampen + against the "parasitic midrange"
and
- no go because the fumes may/will/can harm the membran/surrounds/glue connecting them etc...
since your speakers are ported and the chp70 are lower priced: go for it!
- no go because the fumes may/will/can harm the membran/surrounds/glue connecting them etc...
Thanks for the heads up on that one. The last thing I want to do is risk trashing the drivers. I will try something else.
My hole cutters had its first blast today to make some plugs for the binding posts to drop into on the back panel. Works a treat. Should have had one of those years ago. Should cast those on tomorrow, and hope they stick.
Still trying to rescue no1, but I have decided to eventually cast two complete new ones with a different mix as soon as I can afford and source the materials.
Thinking of using stone dust in a strong mortar mix.
But these two will do as tempoary boxes for the drivers while I learn a bit more.
I did go shoping for br port tubes yesterday, and realised I might have made a mistake on the size. Allthough I have stated 35mm dia by 100mm approx for a 10 liter enclosure with these drivers. I am not sure if that should be 35mm radious.
I cant remember which post I spotted it in, so if Dave from planet 10 reads this could you confirm whether it should be 35mm dia or radious please.
Thanks for the heads up on that one. The last thing I want to do is risk trashing the drivers. I will try something else.
My hole cutters had its first blast today to make some plugs for the binding posts to drop into on the back panel. Works a treat. Should have had one of those years ago. Should cast those on tomorrow, and hope they stick.
Still trying to rescue no1, but I have decided to eventually cast two complete new ones with a different mix as soon as I can afford and source the materials.
Thinking of using stone dust in a strong mortar mix.
But these two will do as tempoary boxes for the drivers while I learn a bit more.
I did go shoping for br port tubes yesterday, and realised I might have made a mistake on the size. Allthough I have stated 35mm dia by 100mm approx for a 10 liter enclosure with these drivers. I am not sure if that should be 35mm radious.
I cant remember which post I spotted it in, so if Dave from planet 10 reads this could you confirm whether it should be 35mm dia or radious please.
Its ok, I found the post I was looking for,
http://www.diyaudio.com/forums/full-range/183983-help-br-design-chp70.html
It seems it should be 38mm by 98mm
http://www.diyaudio.com/forums/full-range/183983-help-br-design-chp70.html
It seems it should be 38mm by 98mm
It would have been 35mm diameter
What size plumbing pipe is standard? (i know about the larger ones 64/76/104)
dave
After having some gas fitting work done recently I have some 30mm plastic tubing.
This has an internal dia of 28mm. Would it be possable to use this. I can alter my hole cutter to cope with this size.
The on line calculator gives me a length of 129mm. Do you think this small would be prone to chuffing.
This has an internal dia of 28mm. Would it be possable to use this. I can alter my hole cutter to cope with this size.
The on line calculator gives me a length of 129mm. Do you think this small would be prone to chuffing.
Hi there: Suggest making forms that bolt together, thus allowing disassembly for from removal. Both outside and inside forms are made this way in precasting plants. Another possibility is to make the inside form from foam insulation, ( the foam can be removed by disolving it! ). However, residule solvent must be washed out to avoid driver damage. Also small air pockets attach to form work and cause bug holes. Bug holes are normally filled by rubbing with a grout mix. Since concrete is low in tensile strength, reinforcing may be needed, both steel bars, mesh and fiber glass rods are available. regards, Michael
Thanks for the link dave.
Ive double checked every thing, and in some cases, Ive been confusing diameter and radius.
The pipe I have available is actualy 60mm OD with an internal Dia 56mm. If ive used your formular correctly this gives a tube length of only 45mm which I guess is too short.
I will see what else I can find.
I think the confusion came about when I asked a store assistant if they had a 35mm dia port tube and he braught back a tube about 90mm in dia.
Thanks for the addvise on the concrete forms. I had been thinking about creating a fiberglass mold, but as it happens the outer molds worked perfectly well. I do intend to use foam for the inner molds when I recast them as the inner wooden ones caused me a few small problems.
Even though these look terrible, Im completeing them so I can listen to them and it will help me in the subsequent redesign. Perhapse increasing wall thickness, or maybe cast in some strengthening ribs etc.
The only re-enforcing I have included so far is the polypropelene fibers. When I cast the stands, these will definatly need rebars in, as well as mesh probably.
Ive double checked every thing, and in some cases, Ive been confusing diameter and radius.
The pipe I have available is actualy 60mm OD with an internal Dia 56mm. If ive used your formular correctly this gives a tube length of only 45mm which I guess is too short.
I will see what else I can find.
I think the confusion came about when I asked a store assistant if they had a 35mm dia port tube and he braught back a tube about 90mm in dia.
Thanks for the addvise on the concrete forms. I had been thinking about creating a fiberglass mold, but as it happens the outer molds worked perfectly well. I do intend to use foam for the inner molds when I recast them as the inner wooden ones caused me a few small problems.
Even though these look terrible, Im completeing them so I can listen to them and it will help me in the subsequent redesign. Perhapse increasing wall thickness, or maybe cast in some strengthening ribs etc.
The only re-enforcing I have included so far is the polypropelene fibers. When I cast the stands, these will definatly need rebars in, as well as mesh probably.
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Found some on ebay that should be suitable, with a 50mm internal dia, 63.5mm long.
I will adjust them to suit, after ive finalised the actual volume. So I thaught I would redraw them how they should now appear. With some company this time.
I will adjust them to suit, after ive finalised the actual volume. So I thaught I would redraw them how they should now appear. With some company this time.
An externally hosted image should be here but it was not working when we last tested it.
Hi there DH: Reread the thread, noticed that you placed concrete into bax forms on 21SEP 11 and removed on Friday 23SEP11 (time in the form was about 2.5 days+-). Inital set occurs at about 18 to 20 hours (compressive strength is low about 1500+- at thos time). Type I portland cement used in concrete, gains stength slowly, about 75% strength in 7 days and rated strength at 28 days. Type III ( known as high early cement)has about the same conctete compressive strength at 3 days as Type I and 28 day strength at 7 days. Also, curing after placing and throughout the 28 days is essential to gain full rated strength. Curing is best accomplished by moist cure (contineous mist, wet blankets, imersion, etc). Also note that concretre strength is mainly influenced by water to cement ratio at the time of mixing, so adding water to make concrete flow better reduces strength markedly. There are additives widely used to reduce water in the mix and promote flow during placing. High cement content mix is prone to shrinkage cracking. Your project is interesting and the small cast enclosures were fabulous. Glad to hear that you are repairing the first boxes for listening tests, measurements if possible.....regards,Micheal
Thanks Micheal. I did quite a bit of research before hand, and several small test blocks, and as this was my first ever attempt a concreteing, still made all the nube mistakes. I did leave the initial casts in the molds and baged up in polythene, sprayed with water occasionally, for a full 6 days before the exitment got to much. I probably dident post about it emediatly.
I couldent afford any addmixture. The places I tried only sold 5 liter containers, so I tried to do with out. It was following the manufactures instructions for the water content on the first one that caused the flow problems.
Also I used general purpose ready mix which includes 10mm agrigate. This has a habit of settleing out in the bag in storage, and each mix I made had a different ratio.
On about the third night after casting, just after I had gone to bed, there was a sound like an enormous sheet of glass cracking. I guessed what it was, and the second one I cast, with both a higher moisture content, and more cement, judging by the colour, has a hair line shrinkage crack in it. After dribbling a watery mix of pva in it it seems to be repaired, and now ive cast the back panels on it will do for temporary.
I pursivered with the first one, and by removing the inner mold a piece at a time, I was able to fill any voids that showed up. I finished up filling smaller bug holes and the like with a mix of poly filler and pva, which dries very quickly , sands well but is supprisingly tough.
At this stage, it looks like I will have two usable boxes. No 2 is allmost ready for painting, while I wait for the back panel to cure on No1.
Back to the design. In the picture above, I think that the bass ports Ive ordered from ebay look a bit over powering, so I intend to route down the flaired mouth, and inlet it flush with the face of the baffle, like this.
I should be attempting to fit the drivers in the baffles tomorrow, so I will put some more progress pics up then.
Cheers, Dave
I couldent afford any addmixture. The places I tried only sold 5 liter containers, so I tried to do with out. It was following the manufactures instructions for the water content on the first one that caused the flow problems.
Also I used general purpose ready mix which includes 10mm agrigate. This has a habit of settleing out in the bag in storage, and each mix I made had a different ratio.
On about the third night after casting, just after I had gone to bed, there was a sound like an enormous sheet of glass cracking. I guessed what it was, and the second one I cast, with both a higher moisture content, and more cement, judging by the colour, has a hair line shrinkage crack in it. After dribbling a watery mix of pva in it it seems to be repaired, and now ive cast the back panels on it will do for temporary.
I pursivered with the first one, and by removing the inner mold a piece at a time, I was able to fill any voids that showed up. I finished up filling smaller bug holes and the like with a mix of poly filler and pva, which dries very quickly , sands well but is supprisingly tough.
At this stage, it looks like I will have two usable boxes. No 2 is allmost ready for painting, while I wait for the back panel to cure on No1.
Back to the design. In the picture above, I think that the bass ports Ive ordered from ebay look a bit over powering, so I intend to route down the flaired mouth, and inlet it flush with the face of the baffle, like this.
I should be attempting to fit the drivers in the baffles tomorrow, so I will put some more progress pics up then.
Cheers, Dave
Not much of one, but heres two undergoing final filling ready for painting. Its got the back on with the expensive starter bars, and the hole that I made the plugs for with me gadget. Fits like a glove, and ive cast some plasterboard rawl plugs in, wraped in selotape to keep the grout out.
Frightened to death of splintering the bamboo.
Onwards.
An externally hosted image should be here but it was not working when we last tested it.
Frightened to death of splintering the bamboo.
Onwards.
Here it is from the front, with the bamboo test fited in. Ive found out, that you get a better result with these sort of things, if you remove the molds while the concrete is stil a bit green.
In this case, after 6 days it had got a pretty good hold on it, and so you can see where I have used two part epoxy "milliput" to get a clean edge again.
The other one looks lke a wedding cake.
In this case, after 6 days it had got a pretty good hold on it, and so you can see where I have used two part epoxy "milliput" to get a clean edge again.
The other one looks lke a wedding cake.
Got some paint on them, but they need another coat or two. I gave them several coats of a watery mix of pva, inside and out, and its like hardening and temporing for concrete. Really toughens them up.
Heres a pic of the wedding cake just before painting.
and after. Its abit like black board paint, again from the pound shop. I tested it on a small block, and when thoroughly dry is very tough and dosent show finger marks. It does show brush marks though, so I will roller on the final coat with one of those "behind the radiator" rollers, after flatening them out again.
Very difficult to get a picture with my camera, but they have turned out ok.
Cirtainly good enough for listening test.
Still havent routed the baffles yet. Im hopeing the ports turn up soon, so I can finish that job in one go.
Found the links for diy cables, braiding ethernet cable, and will look into making some up for the internal wiring aswell.
Heres a pic of the wedding cake just before painting.
An externally hosted image should be here but it was not working when we last tested it.
and after. Its abit like black board paint, again from the pound shop. I tested it on a small block, and when thoroughly dry is very tough and dosent show finger marks. It does show brush marks though, so I will roller on the final coat with one of those "behind the radiator" rollers, after flatening them out again.
An externally hosted image should be here but it was not working when we last tested it.
Very difficult to get a picture with my camera, but they have turned out ok.
Cirtainly good enough for listening test.
Still havent routed the baffles yet. Im hopeing the ports turn up soon, so I can finish that job in one go.
Found the links for diy cables, braiding ethernet cable, and will look into making some up for the internal wiring aswell.
Thanks for the encuragement. You wouldent believe how many times they nearly went in the skip, and fresh ones cast. But I want to encorporate improvments in the next ones. Pointless unless I have a referance point.
Which leads me on to the next point. Some of you have suggested posting measurements, so while waiting for the rest of it to come together, going through my stuff, if found enough old bits for a diy measurement mic. A old scrap Realistic 33 1060 electret condenser mic, which ive pulled the module from. Its not the recomended Panasonic one, but I think it should do the trick if I can calibrate it. Any tips there would be helpfull.
Ive downloaded a few usefull apps such as Speaker Workshop, and tried to get used to how they work, but building the Wallin jig wont be possable for a bit.
Is there a simple way to calibrate it, without blowing my computer up.
Which leads me on to the next point. Some of you have suggested posting measurements, so while waiting for the rest of it to come together, going through my stuff, if found enough old bits for a diy measurement mic. A old scrap Realistic 33 1060 electret condenser mic, which ive pulled the module from. Its not the recomended Panasonic one, but I think it should do the trick if I can calibrate it. Any tips there would be helpfull.
Ive downloaded a few usefull apps such as Speaker Workshop, and tried to get used to how they work, but building the Wallin jig wont be possable for a bit.
Is there a simple way to calibrate it, without blowing my computer up.
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