I would interested to get feedback on this project.
I'm trying some designs out using CNC routing. Having built the Medallion horn using 'traditional' wood working methods, I decided I needed an easier build....hence CNC.
My plan is to build the horn in slices, using 32mm high density chipboard or MDF. The internal horn path will be coated in a hard resin to minimise sound absorption in the wood.
I also plan to offer the horns for sale via flat packing them. The assembly will be very straight forward, as the horn internals will fit together on 2 or 3 dowels, ensuring 100% alignment. Even the external panels will be aligned this way. There will be no screwing, only gluing. Real wood veneered external MDF panels will be used, or plain MDF for painting. Optional hardwood or ply can be arranged.
In looking at the design, what tweaks would you recommend? I've essentially taken the exact measurements of the BFH and rounded out the entire horn path. There are no straight lines in the internal section at all.
On the drawing, you can see a small line breaking the horn on the left hand side. As the routing procedure will cause a lot of waste, the horn will be made in two section. The line indicates where the break will occur. I'll then turn that lower section up towards the larger section, which will cut the waste down by 50%.
Being able to tweak the size of the compression chamber, I can build the horns to suit different drivers - eg Lowther DX series, or even something like the Fostex 206E. Basically, I want to build speakers that mean people can have access to a quality unit, at an affordable price.
Thoughts/feedback appreciated.
Andrew. Sydney.
I'm trying some designs out using CNC routing. Having built the Medallion horn using 'traditional' wood working methods, I decided I needed an easier build....hence CNC.
My plan is to build the horn in slices, using 32mm high density chipboard or MDF. The internal horn path will be coated in a hard resin to minimise sound absorption in the wood.
I also plan to offer the horns for sale via flat packing them. The assembly will be very straight forward, as the horn internals will fit together on 2 or 3 dowels, ensuring 100% alignment. Even the external panels will be aligned this way. There will be no screwing, only gluing. Real wood veneered external MDF panels will be used, or plain MDF for painting. Optional hardwood or ply can be arranged.
In looking at the design, what tweaks would you recommend? I've essentially taken the exact measurements of the BFH and rounded out the entire horn path. There are no straight lines in the internal section at all.
On the drawing, you can see a small line breaking the horn on the left hand side. As the routing procedure will cause a lot of waste, the horn will be made in two section. The line indicates where the break will occur. I'll then turn that lower section up towards the larger section, which will cut the waste down by 50%.
Being able to tweak the size of the compression chamber, I can build the horns to suit different drivers - eg Lowther DX series, or even something like the Fostex 206E. Basically, I want to build speakers that mean people can have access to a quality unit, at an affordable price.
Thoughts/feedback appreciated.
Andrew. Sydney.
Hi,
Good idea. I am not sure how you would get the flat packs to the USA, UK etc because of costs but throughout OZ should be ok. Possibly an option for overseas users would be to offer to buy the plans to take to their local CNC shop? I know you want to make a couple of dollars but I can't see the shipping thing working IMO.
Since its all going to be joined why use 50mm material? Surely 18mm would be cheaper overall? Or were you thinking less bits to stick together would outweigh that?
Look forward to whats others say.
Good idea. I am not sure how you would get the flat packs to the USA, UK etc because of costs but throughout OZ should be ok. Possibly an option for overseas users would be to offer to buy the plans to take to their local CNC shop? I know you want to make a couple of dollars but I can't see the shipping thing working IMO.
Since its all going to be joined why use 50mm material? Surely 18mm would be cheaper overall? Or were you thinking less bits to stick together would outweigh that?
Look forward to whats others say.
Spacies, thanks.
Yes - there's no plan to ship overseas...however I have given some thought to the CAD plans being made available online. In this regard, I would also offer 'custom' plans whereby a speaker plan will be tailored to suit a particular driver. This process is relatively easy as I would simply size the compression chamber and throat to suit. Then upload the revised CAD file on the net for that customer
On thicknesses, I'n not sure where you got 50mm from. The individual 'slices' will be 32 mm, with the outer panels in 25mm. A 17mm venerred MDF panel can be applied to this subject to what the buyer wants.
Regards
Yes - there's no plan to ship overseas...however I have given some thought to the CAD plans being made available online. In this regard, I would also offer 'custom' plans whereby a speaker plan will be tailored to suit a particular driver. This process is relatively easy as I would simply size the compression chamber and throat to suit. Then upload the revised CAD file on the net for that customer
On thicknesses, I'n not sure where you got 50mm from. The individual 'slices' will be 32 mm, with the outer panels in 25mm. A 17mm venerred MDF panel can be applied to this subject to what the buyer wants.
Regards
Hi atilsley
A couple of points occurred to me....
1. if I understand correctly that you will supply flatpack in sections/slices, wouldn't the flatpack be the same size as the finished cab, or am I misunderstanding?
2. Wouldn't it be possible to supply templates from your CNC rig, to cater for all the guys with router capability??
just a couple of thoughts, I'm not really a horn devotee but your post did intrigue me..
Regards
Ed
A couple of points occurred to me....
1. if I understand correctly that you will supply flatpack in sections/slices, wouldn't the flatpack be the same size as the finished cab, or am I misunderstanding?
2. Wouldn't it be possible to supply templates from your CNC rig, to cater for all the guys with router capability??
just a couple of thoughts, I'm not really a horn devotee but your post did intrigue me..
Regards
Ed
Vitalstates
1. Because of the very large horn mouth of the Big Fun Horn, I will break the routed sections into two. This will cut down on wastage by 50%, plus make the transport easier. Remember, this is a large speaker, and I don't expect to promote it greatly....it's more one for my own use. However, I wish to get to a proof of concept for alternate designs - eg the public domain designs by Lowther etc. A flatpack acousta 115, for example, would be very easy to ship and assemble.
http://www.lowther.com.hk/acousta.htm
2. Yes - I plan to put up the designs on the web, but I'd like to recoup some of my set-up costs. I don't do the actual CAD drawings, so I have to fund that aspect.
On another point - while my passion is horns, the CNC routing enables me to construct all sorts of cabinets. For example, I've been playing around with a design that incorporates a 'standard' bass unit with curved sides and exceptional internal bracing, with a Lowther driver housed in a separate cabinet on top taking care of 200Hz and above. The top cabinet would feature the same curved sides, just a smaller profile. The bass unit would be active with adj cross-over, thus making this type of application very easy for valve lovers to hook up their amps.
Regards
1. Because of the very large horn mouth of the Big Fun Horn, I will break the routed sections into two. This will cut down on wastage by 50%, plus make the transport easier. Remember, this is a large speaker, and I don't expect to promote it greatly....it's more one for my own use. However, I wish to get to a proof of concept for alternate designs - eg the public domain designs by Lowther etc. A flatpack acousta 115, for example, would be very easy to ship and assemble.
http://www.lowther.com.hk/acousta.htm
2. Yes - I plan to put up the designs on the web, but I'd like to recoup some of my set-up costs. I don't do the actual CAD drawings, so I have to fund that aspect.
On another point - while my passion is horns, the CNC routing enables me to construct all sorts of cabinets. For example, I've been playing around with a design that incorporates a 'standard' bass unit with curved sides and exceptional internal bracing, with a Lowther driver housed in a separate cabinet on top taking care of 200Hz and above. The top cabinet would feature the same curved sides, just a smaller profile. The bass unit would be active with adj cross-over, thus making this type of application very easy for valve lovers to hook up their amps.
Regards
The later versions do but the upgrade is $$$$$
Hi Andrew,
You wrote about “your” BFH:
“There are no straight lines in the internal section at all”
Actually you can draw infinitive number of straight lines on internal section - from one side wall to the other. Not to mention that side walls are totally flat and parallel.
Anyway, what made you believe that a spiral horn is better than a horn with straight sections connected by rounded turns? Look at two Carfrae horns – the good one has two straight or almost straight sections.
Have fun plying a pro but don’t quit your day time job yet…
Marek Stojek
You wrote about “your” BFH:
“There are no straight lines in the internal section at all”
Actually you can draw infinitive number of straight lines on internal section - from one side wall to the other. Not to mention that side walls are totally flat and parallel.
Anyway, what made you believe that a spiral horn is better than a horn with straight sections connected by rounded turns? Look at two Carfrae horns – the good one has two straight or almost straight sections.
Have fun plying a pro but don’t quit your day time job yet…
Marek Stojek
Marek, not quite sure whether you're having a go at me or not...this is just a fun hobby for me....but enables me to create great horn speakers for people using a modern easy build process.
I was using nonparallel walls to take the best use of CNC routing. I understand straight lines are ok....but I just wanted to play with the design a little. Plus, there's a theoretical issue re standing waves which my approach minimises.
I have Jim's permission to market the Carfrae LBH, so I'll be using the CNC routing to its fullest in this design.
Any tweaks you'd suggest?
Cheers.
I was using nonparallel walls to take the best use of CNC routing. I understand straight lines are ok....but I just wanted to play with the design a little. Plus, there's a theoretical issue re standing waves which my approach minimises.
I have Jim's permission to market the Carfrae LBH, so I'll be using the CNC routing to its fullest in this design.
Any tweaks you'd suggest?
Cheers.
I learned geometry a long time ago in Polish so sometimes I have a problem understanding.
“I was using nonparallel walls…”
A horn with a rectangle as its cross section has 4 walls. I believe the designs you are trying to improve (LBH, BFH, Hedlund) have 2 parallel (side) walls. Is that right? Are you planning to change that or are you just rounding the corners of the other two walls which are already not parallel?
The walls of Big Carfare Horn are not parallel although it has a rectangular cross section and one can draw straight lines on the horn walls.
“Any tweaks you’d suggest?”
Not exactly a tweak but if you want a good horn ask your neighbor the Azura dude if he has anything left over.
Good luck.
“I was using nonparallel walls…”
A horn with a rectangle as its cross section has 4 walls. I believe the designs you are trying to improve (LBH, BFH, Hedlund) have 2 parallel (side) walls. Is that right? Are you planning to change that or are you just rounding the corners of the other two walls which are already not parallel?
The walls of Big Carfare Horn are not parallel although it has a rectangular cross section and one can draw straight lines on the horn walls.
“Any tweaks you’d suggest?”
Not exactly a tweak but if you want a good horn ask your neighbor the Azura dude if he has anything left over.
Good luck.
That looks great. Can't wait to see some finished speakers! Pictures pictures pictures.
I like your idea and have given some thought to some 3 d structures from plywood. I've made two cones that were supposed to be two halves of a sphere! Ha ha I'm so dumb. Now I don't know what to do with them.
Is it the inside horn that is curvy only? So the curvy horn fits inside a box with the box making up one side of the horn wall?
I've found some local people willing to do the milling on a frugal horn for me for about 5-600 USD. Still kind of expensive but not crazy for a one off project.
P.S.
Don't let people shoot down your dreams. Nay-sayers are a dime a dozen. It's easier to poke holes in balloons than fill them up.
I like your idea and have given some thought to some 3 d structures from plywood. I've made two cones that were supposed to be two halves of a sphere! Ha ha I'm so dumb. Now I don't know what to do with them.
Is it the inside horn that is curvy only? So the curvy horn fits inside a box with the box making up one side of the horn wall?
I've found some local people willing to do the milling on a frugal horn for me for about 5-600 USD. Still kind of expensive but not crazy for a one off project.
P.S.
Don't let people shoot down your dreams. Nay-sayers are a dime a dozen. It's easier to poke holes in balloons than fill them up.
Thanks guys.
Yes - the outer walls are still parallel. so for designs such as Hedlund, FH etc, all the exterior walls are parallel. All internal corners re rounded, and where I can, two isdes will not be parallel.
My own speakers will be the BFH, using DX2 drivers. Outer cabinet walls will be veneered MDF (professionally mounted).
To the question about horn shape -
One design for the Carfrae LBH was for a passive unit, ie no bass modul and amp. The picture you see shows the CNC routered section has a squared off top and back. This makes for any easy build, with no veneering required on curved surfaces....which is a harder job. Remember, my goal is to build horns for people to assemble easily.
For the Hedlund, I can do either rounded top section, or squared off. The Hedlund is interesting because the entire internal workings is machined from one piece...whereas the Carfrae has the smaller internal section, plus the larger horn path...still easy to build though.
I can confim that Jim Carfrae has provided me approval to produce the LBH. I have a 'kit' being worked on now, and working with gent in Athens, Greece to ship a pair to him. Costs are very attractive...especially as I'm just getting started.
Building a small speaker like the Acousta 115 now seems very easy....! The Frugal/Spawn/Dallas/Austin are great speakers which get terrific reviews. I'd like to help people with these as well....provided the designs are in the public domain.
I've also designed a bass horn using 30 individual slices of 32mm MDF CNC sections. The horn exits to the back, with lovely curved side walls. This design could also be adopted for a unique speaker like the new SEAS exotic - http://www.seas.no/index.php?option=com_content&task=view&id=191&Itemid=187
I will be producing photos and a DVD of the build process. I've registered a company name, Creation Audio, and I hope to build a web presence shortly.
Yes - the outer walls are still parallel. so for designs such as Hedlund, FH etc, all the exterior walls are parallel. All internal corners re rounded, and where I can, two isdes will not be parallel.
My own speakers will be the BFH, using DX2 drivers. Outer cabinet walls will be veneered MDF (professionally mounted).
To the question about horn shape -
One design for the Carfrae LBH was for a passive unit, ie no bass modul and amp. The picture you see shows the CNC routered section has a squared off top and back. This makes for any easy build, with no veneering required on curved surfaces....which is a harder job. Remember, my goal is to build horns for people to assemble easily.
For the Hedlund, I can do either rounded top section, or squared off. The Hedlund is interesting because the entire internal workings is machined from one piece...whereas the Carfrae has the smaller internal section, plus the larger horn path...still easy to build though.
I can confim that Jim Carfrae has provided me approval to produce the LBH. I have a 'kit' being worked on now, and working with gent in Athens, Greece to ship a pair to him. Costs are very attractive...especially as I'm just getting started.
Building a small speaker like the Acousta 115 now seems very easy....! The Frugal/Spawn/Dallas/Austin are great speakers which get terrific reviews. I'd like to help people with these as well....provided the designs are in the public domain.
I've also designed a bass horn using 30 individual slices of 32mm MDF CNC sections. The horn exits to the back, with lovely curved side walls. This design could also be adopted for a unique speaker like the new SEAS exotic - http://www.seas.no/index.php?option=com_content&task=view&id=191&Itemid=187
I will be producing photos and a DVD of the build process. I've registered a company name, Creation Audio, and I hope to build a web presence shortly.
I am glad we got the geometry straightened up, but for the benefit of newcomers I would like to clarify the information about designs you are planning to use. With exception of BFH the horns are too small to work as single driver speakers. They need a subwoofer! Hedlund is long enough but the mouth is too small.
Many people like the sound of those horns but it doesn’t change the fact that the boxes were designed for easy built not for the best sound possible.
CNC routing improves horn path a lot but with all the efforts I would go one step further and make the compression chamber round with a round throat on the chamber’s axis. I would make the first foot of the horn straight and use it as a transition from round to square profile. I would use hard wood for compression chamber…
I am not a potential customer as I already made a horn of my dreams.
Many people like the sound of those horns but it doesn’t change the fact that the boxes were designed for easy built not for the best sound possible.
CNC routing improves horn path a lot but with all the efforts I would go one step further and make the compression chamber round with a round throat on the chamber’s axis. I would make the first foot of the horn straight and use it as a transition from round to square profile. I would use hard wood for compression chamber…
I am not a potential customer as I already made a horn of my dreams.
Sigh. Let us cease the pedantry and get off the poor guy's back here. Most bass 'horns' do not maintain horn loading down to Fc, and are a hybrid of QW resonant loading shifting to horn loading as the acoustic impedance match at the mouth improves. In a properly designed one, this is not a big deal, or a cause to wave hands in the air, or predict the end of civilisation as we know it. If you want some pedantry BTW, try this: 99% of BLHs don't have a compression chamber in the generally accepted sense. Well, actually, all of them have: it's called the room they happen to be placed in. The chamber the driver is often, but not invariably, mounted in, is a low-pass filter chamber, making many, unless reactance annulled, analogous to BR cabinets with very large expanding vents. Regarding parallel walls, they are certainly not ideal; however, they are not the end of the world either.
Moving on, rounding off the rest of the horn path will improve efficiency, although you may get a little HF leakage, as the remaining shorter wavelengths will find it easier to pass through the horn path. Don't try rounding off designs like the Fostex Factory boxes, which use an expanding cascade of straight manifolds. They aren't designed the same way as other enclosures so smoothing them out can cause problems.
As a piece of friendly advice, you're edging toward commercial advertising here, so you might want to be a little careful about exactly what is posted. I know it's in a sense trying to help the DIY community, which is probably why the moderators have left it here, but it's in the gray zone, if you take my meaning.
Moving on, rounding off the rest of the horn path will improve efficiency, although you may get a little HF leakage, as the remaining shorter wavelengths will find it easier to pass through the horn path. Don't try rounding off designs like the Fostex Factory boxes, which use an expanding cascade of straight manifolds. They aren't designed the same way as other enclosures so smoothing them out can cause problems.
As a piece of friendly advice, you're edging toward commercial advertising here, so you might want to be a little careful about exactly what is posted. I know it's in a sense trying to help the DIY community, which is probably why the moderators have left it here, but it's in the gray zone, if you take my meaning.
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