I just bought plans for the DR280 and I am still working on my recommended third reading before I start buying supplies.
I'll probably get beat down for this question but here goes...
If I were to actually get my hands on some 24 inch PVC pipe (biggest they make), why not use the PVC for the outer section of the bend in the horn?
Hey, it was just a thought...
Jay
PVC in the DR280
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Bill Fitzmaurice
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It's absurd.
Considering how easy it is to bend the outer section of the horn, why double the weight of the cabs using PVC pipes?!
(Sorry about the European standards. I just don't copy with inch, foot, ounze, gauge etc)
The density of rigid PVC is 1.30-1.58 g/ccm (flexible PVC is 1.16-1.35 g/ccm).
That's at least 1,300 kg/cubic meter.
Birch ply is only ~700 kg/cubic meter.
According to the plans you should use 6 mm ply for the bends. The PVC pipe is 17 mm.
With twice the weight and three times the thickness, that makes the PVC bends six times the weight of the plywood bends!
I don't get it...
Nordskov
Considering how easy it is to bend the outer section of the horn, why double the weight of the cabs using PVC pipes?!
(Sorry about the European standards. I just don't copy with inch, foot, ounze, gauge etc)
The density of rigid PVC is 1.30-1.58 g/ccm (flexible PVC is 1.16-1.35 g/ccm).
That's at least 1,300 kg/cubic meter.
Birch ply is only ~700 kg/cubic meter.
According to the plans you should use 6 mm ply for the bends. The PVC pipe is 17 mm.
With twice the weight and three times the thickness, that makes the PVC bends six times the weight of the plywood bends!
I don't get it...
Nordskov
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Harley
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Re: PVC in the DR280
After Golden Rule #1 which reads "Read the plans through thoroughly at least 3 times, comes Golden Rule # 2 "Don't deviate from the plans - no matter how tempted!"Troutwiz wrote:If I were to actually get my hands on some 24 inch PVC pipe (biggest they make), why not use the PVC for the outer section of the bend in the horn?
Harley
Semi-retired: Former Australia and New Zealand Authorised BFM cab builder.Welcome To Our Little Shop Away From Shop.
You'll quickly learn that Bill's plans are about as easy and thorough as they can possibly be. Most of the designs have been built hundreds of times, and many updates to the plans have been added over time, due to Bill's diligence and due to builders' experiences and ideas. If you just follow the plans to the tee, you'll have the best possible results. If you have any questions or problems along the way, just post here and you will be promptly overwhelmed with help. Remember that the only stupid question is the one that you didn't ask.
Just so you know ... if you keep hanging around here, you're going to quickly learn more about loudspeaker cabinet design than you ever knew existed. Become familiar with Bill's designs, read everything that you can, ask questions, take notes, and keep an open mind. This is a VERY friendly, helpful group, with an amazingly diverse knowledge of all aspects of music gear, so you'll find that this will become an invaluable resource for you, as well as a comfortable place to just hang-out.
You'll quickly learn that Bill's plans are about as easy and thorough as they can possibly be. Most of the designs have been built hundreds of times, and many updates to the plans have been added over time, due to Bill's diligence and due to builders' experiences and ideas. If you just follow the plans to the tee, you'll have the best possible results. If you have any questions or problems along the way, just post here and you will be promptly overwhelmed with help. Remember that the only stupid question is the one that you didn't ask.
Just so you know ... if you keep hanging around here, you're going to quickly learn more about loudspeaker cabinet design than you ever knew existed. Become familiar with Bill's designs, read everything that you can, ask questions, take notes, and keep an open mind. This is a VERY friendly, helpful group, with an amazingly diverse knowledge of all aspects of music gear, so you'll find that this will become an invaluable resource for you, as well as a comfortable place to just hang-out.
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DAVID_L_PERRY
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I would only consider using pvc for the rear reflectors, not the main throat curves..
I have built 2 DR280's using PVC to form the rear butt cheaks with great success.
The reason I looked into this is that I don't like the filling and sanding required to fill in the butt cheeks to the top and btm, and that I had got hold of some PVC ribbed (twin wall) pipe with a 3-4mm wall thickness. The outer ribs required cutting off to fit in the box, done very quickly using a simply hand held grinder.
The build process was no quicker to get to the point where the sides are going on, howevor the top and btm panels do not require any filling and sanding.
I have built 4DR280's, the first pair built using the plans method, the second pair built using the PVC pipe routered into the top and btm panels no cutting and gluing of the infill's required....no filling and sanding required as there is no join to contend with.....
I would certainly build them again using the pipe as the time saved on filling and sanding to me was well worth it. The small weight increase to me was worth it.
Dave
I have built 2 DR280's using PVC to form the rear butt cheaks with great success.
The reason I looked into this is that I don't like the filling and sanding required to fill in the butt cheeks to the top and btm, and that I had got hold of some PVC ribbed (twin wall) pipe with a 3-4mm wall thickness. The outer ribs required cutting off to fit in the box, done very quickly using a simply hand held grinder.
The build process was no quicker to get to the point where the sides are going on, howevor the top and btm panels do not require any filling and sanding.
I have built 4DR280's, the first pair built using the plans method, the second pair built using the PVC pipe routered into the top and btm panels no cutting and gluing of the infill's required....no filling and sanding required as there is no join to contend with.....
I would certainly build them again using the pipe as the time saved on filling and sanding to me was well worth it. The small weight increase to me was worth it.
Dave
3-4 mm wall thickness makes more sense. Still a little heavier than ply, but not much.DAVID_L_PERRY wrote: ... and that I had got hold of some PVC ribbed (twin wall) pipe with a 3-4mm wall thickness...
Dave
And I follow you on the time consuming issue.
Must have been a hell cutting off those ribbs - and a mess too, dust everywhere
Nordskov
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DAVID_L_PERRY
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Cutting off the ribs was very quick using a grinder...very much like a knife through butter....I only trimmed the sides and the back of the ribs where they needed trimming to fit adjoining panels. Dust...yep...but probably no more than any other part of the cutting process using a circular saw...only it was orange....
I must say the only reason I looked at trying this method was to allow the top and btm panels to remain as one piece.
The latest DR250 plans have a very similar method now adopted using pre bent steel/aluminum panels as an add on by Harley, more for mass production runs.
Dave
I must say the only reason I looked at trying this method was to allow the top and btm panels to remain as one piece.
The latest DR250 plans have a very similar method now adopted using pre bent steel/aluminum panels as an add on by Harley, more for mass production runs.
Dave
David, you got me on the "grinder". It's not in my dictionary.
I assume it's the monster with the fast rotating, angled disc mostly made of carbide, used for cutting a variety of materials as; stone, concrete, steel etc.
Am I right?
My brother in law had a bakery where I worked one summer.
One day he went to a conference, and the journeyman and me wanted to surprise him by changing a broken castor on one of the machines.
So we turned the thing on its side and used the grinder to remove the broken castor. We were very proud that we had done it without any complications, and it was not untill we stood back admiring our job, that we noticed something was wrong.
It suddenly struck us that everything in the bakery was covered by a thin, grey layer of dust.
In our eager to show off, we hadn't noticed that tiny bits had been knocked off of the disc and was spread everywhere; bags of white and full grain flour, cream-powder pot, grease pot, dough kneader, yeast box, tables etc. Even in our pants.
Looking back we should have dumped every open bag and can, but we didn't want to lose face. So we spend three hours cleaning everything up.
We didn't get any complaints of broken teeth and the like by our customers. Maybe they were too kind to tell us.
Maybe they couldn't tell the difference from the ordinary bread
We never told him about it, he still doesn't know and never will for sure.
Nordskov
I assume it's the monster with the fast rotating, angled disc mostly made of carbide, used for cutting a variety of materials as; stone, concrete, steel etc.
Am I right?
My brother in law had a bakery where I worked one summer.
One day he went to a conference, and the journeyman and me wanted to surprise him by changing a broken castor on one of the machines.
So we turned the thing on its side and used the grinder to remove the broken castor. We were very proud that we had done it without any complications, and it was not untill we stood back admiring our job, that we noticed something was wrong.
It suddenly struck us that everything in the bakery was covered by a thin, grey layer of dust.
In our eager to show off, we hadn't noticed that tiny bits had been knocked off of the disc and was spread everywhere; bags of white and full grain flour, cream-powder pot, grease pot, dough kneader, yeast box, tables etc. Even in our pants.
Looking back we should have dumped every open bag and can, but we didn't want to lose face. So we spend three hours cleaning everything up.
We didn't get any complaints of broken teeth and the like by our customers. Maybe they were too kind to tell us.
Maybe they couldn't tell the difference from the ordinary bread
We never told him about it, he still doesn't know and never will for sure.
Nordskov
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Bill Fitzmaurice
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Nordskov wrote:David, you got me on the "grinder". It's not in my dictionary.
http://www.bellacinos.com/grinders.htm
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gdougherty
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Thank you for correcting me, Bill. I thought it was some kind of machinery. But I don't see how David used that sandwich to remove the ribs from his pipeBill Fitzmaurice wrote:Nordskov wrote:David, you got me on the "grinder". It's not in my dictionary.
http://www.bellacinos.com/grinders.htm
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DAVID_L_PERRY
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Ok for all you comedians.....
A grinder....
Mine is very similar to this.
The way the pvc pipe was fitted was to router a channel exactly where you would normally cut the butt cheeks.
I dont see how ply would be possibly as it would keep springing out ...
The whole reason I went for PVC was simply that it was a pre-formed radius so I could simply cut it and slide it into place...exactly what Harley has now done with the new DR250 plans only with pre formed Aluminium...
Dave
A grinder....
Mine is very similar to this.
The way the pvc pipe was fitted was to router a channel exactly where you would normally cut the butt cheeks.
I dont see how ply would be possibly as it would keep springing out ...
The whole reason I went for PVC was simply that it was a pre-formed radius so I could simply cut it and slide it into place...exactly what Harley has now done with the new DR250 plans only with pre formed Aluminium...
Dave