Horn Loudspeaker Project.

Dedicated to those large boxes at one end of the room
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Ray P
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#1 Horn Loudspeaker Project.

Post by Ray P »

I've been happily living with a pair of All Fun Horns, designed by Ketil Parow, for around eight years now. I built them myself, some pictures below. The only changes I've made over the years has been some solid core silver wire and an upgrade from Lowther EX3 drive units to EX4s.

So, why am I starting a thread about a new speaker project? I recognise that horn speakers are compromised by folding them into a box with flat panels and have long harboured thoughts about a less compromised version of the same speaker, the optimal corss section for a horn being round of course. Then I came across these, which are very close to what I had in mind;

http://www.arcadianaudio.com/description_style.html

The main difference is that my horns fire into the corners of the room to allow reasonable bass without gong to big. Having said that I have a room that is large enough for something approaching the size of the Arcadians )in the corners) so, freshly enthused I'm thinking why not?

Ray
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Finishing the first speaker 1 - LR.jpg
First Speaker ready for finish- LR.jpg
Internal Structure Almost Complete - LR.jpg
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Audio_Works
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#2

Post by Audio_Works »

Hello Ray,

Great work on those horns.

About the arcadians I didn't understood if you want to go DIY and clone them or you're thinking of purchasing a pair.

I saw on their site the horns are made from fiberglass. I've made horns from fiberglass too but not bass horns, its pretty good material .
It is my opinion that for bass horns in a proper design effect of bends and parallel walls can be reduced almost to no effect.
In the midrange area the effect of the horn on the response can be tamed by using dampening material inside the horn and/or chambers.
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#3

Post by Ray P »

Audio_Works wrote:Hello Ray,

Great work on those horns.

About the arcadians I didn't understood if you want to go DIY and clone them or you're thinking of purchasing a pair.

I saw on their site the horns are made from fiberglass. I've made horns from fiberglass too but not bass horns, its pretty good material .
It is my opinion that for bass horns in a proper design effect of bends and parallel walls can be reduced almost to no effect.
In the midrange area the effect of the horn on the response can be tamed by using dampening material inside the horn and/or chambers.
I don't want to clone the Arcadian speakers (I think they're circa £20K per pair) but to produce a corner horn, as per the All Fun concept, but with a similar round sinuous horn. It's a concept I've mulled over for a few years and have posted previously on aspects of building them.

At the moment I have set out a 2D profile in AutoCad to get a feel for the finished size, layout etc. I'm going to try and master 3D in AutoCad so I visualise them better.

I've build large model yachts as another hobby so am confident of building a plug (male mould) and of working with composites. Attached is a picture of a plug for the hull of a 2metre long catamaran hull that I've been working on.

t is obvious that GRP (fibregalass) presents one possibility for forming the horn profiles, it is rigid, strong enough to be self supporting (i.e. the form won't sag, for example) and can be brought to a good finish (with some hard work) but is it the best compromise when it comes to this application? Other approaches I've considered are papier mache, plaster and laminated mdf and there may be others?

Papier mache can be formed over a plug as per GRP and can be brough to a good finish. If it is thick enough if will be strong enough and you can make s sort of composite papier mache by adding in layers of cotton fabric. Other advantages are that is is relatively cheap in materials but probably quite time=consuming.

Plaster can also be formed over a plug, It can be strengthened with scrim fabric (like the plaster mould they put over youarm if you break it). I think this might be an ideal material, downsides are weight and fragility?

My thinking on MDF is quite different; basically you slice the horn up into horizontal slices and stack them up. The hole(s) in each slice that will make up the horn profile is sized to the smallest diameter for that slice so you would end up with a stepped horn profile, the trick is to fair these steps out as you work up/down the stack. This is likely to be time consuming. MDF isn't the ideal speaker material but can be given a good finish. The end result will be quite heavy.

Anyway, open to observations/ideas/etc.

Ray
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catamaran0003-LR.jpg
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#4

Post by Audio_Works »

I see, well you are a crafty person so im sure wont be much trouble.

I guess first you should finish the design and based on its considerations (dimensions, number of bends etc) choose the best way to build it.

Plaster, interesting idea, a very versatile material. You might run into trouble with the acoustics tho. Resonances, vibrations... its pretty much uncharted waters. I also would be afraid of cracks even with the fabric.

Since you are a CAD user, a 5 axis CNC and lots of plywood could save you a lot of trouble but it's pricey.
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#5

Post by Ray P »

Audio_Works wrote:Since you are a CAD user, a 5 axis CNC and lots of plywood could save you a lot of trouble but it's pricey.
Hence trying to work out 3D in AutoCad - it aint easy!

Ray
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#6

Post by Audio_Works »

It sure ain't, but you can do it.

I'm curious, have you done some acoustic modeling of the horn?
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#7

Post by Andrew »

Audio_Works wrote: I'm curious, have you done some acoustic modeling of the horn?
I would agree, I can't see inside the horn but it looks like they are applying a front horn style design to a BLH, not sure that would work. But then what I call a BLH is actually a BLH/TL so the same rules may not apply.

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#8

Post by Ray P »

Audio_Works wrote:I'm curious, have you done some acoustic modeling of the horn?
,

I have no means of doing any acoustic modelling other than utilising simple horn theory around calculating the profile, throat, etc. Happy to be shown a way though. In fact I'm simply utilising the Big Fun horn profile as my starting point and attempting to produce a horn to that design that is less-compromised than one with flat sides, folded into a box (which is what I already have).

Ray
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#9

Post by Audio_Works »

Many people use Hornresp: http://www.hornresp.net.ms/

Pretty easy to use and i would try it first.

I also recommend Akabak, its not so user friendly but its more powerful in my opinion. http://www.randteam.de/AkAbak/Index.html

Both are free for non-commercial use.
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#10

Post by Ray P »

Andrew wrote:I would agree, I can't see inside the horn but it looks like they are applying a front horn style design to a BLH, not sure that would work. But then what I call a BLH is actually a BLH/TL so the same rules may not apply.

Andrew
Andrew, why should a FLH design be different to a BLH? Surely they are both 'horns', for which the optimal profile cross section is round, that just differ in length etc.

I suspect that you see a lot more round front loaded horn designs not because of a style issue but because of practical considerations; as FLHs tend to be much shorter they are smaller and tend not to be folded and, so, are much easier to make. A typical BLH will have a profile around 3metres long (so not practical to make a straight one) that are large, even when folded so the usual compromise is to have a rectangular cross section that gets folded into a box with parallel sides.

Conceptually the Arcadia design is similar to something like a Hedlund but without the compromises of its flat sides. Aesthetically it is far more attractive than something like a Hedlund.

The difference between my thinking and the Arcadia is the same as the difference between the Hedlund and the Big Horn; the Hedlund horn couples directly to the room through its front facing mouth whereas the Big Fun mouth exits at the rear of the speaker and is designed to utilise the three planes (two walls and the floor) of a room corner as an extension of its horn profile, enabling a shorter profile and smaller mouth,

As I mentioned before, I continue to be very happy with my All Fun horns (slightly smaller brother to the Big Fun) and I want to see if I can get more out of that approach with a round sinuous profile, that, if nothing else will be a fun exercise and should result in a very attractive pair of objects!

Ray
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#11

Post by Ray P »

Another way to think about what I'm working on is a round cross-section version of the Carfrae Big Fun Horn

http://www.audioevidence.com/pdf/Big%20 ... eviews.pdf

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#12

Post by Ray P »

Audio_Works wrote:Many people use Hornresp: http://www.hornresp.net.ms/

Pretty easy to use and i would try it first.

I also recommend Akabak, its not so user friendly but its more powerful in my opinion. http://www.randteam.de/AkAbak/Index.html

Both are free for non-commercial use.
Ah, that's what you meant; yes, have used HornResp but will check out the other one. That's what I meant by horn theory around the throat, profile etc. and I thought you were into something much deeper around modelling the theoretical behaviour of different materials etc. That said, as I'm using the profile data from an established and well-considered design I'mnot spending a lot of time on this aspect but a lot more on the realisation of the less-compromised profile.

Ray
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#13

Post by Andrew »

In a BLH/TL, the compression chamber is a vital component, given all the horns I have heard, I doubt anyone has got it truly right yet in all respects.

If you read MJK (www.quarterwave.com) you will start to get a picture of the problem of how a BLH must, unless its truly huge, transition to a TL below a certain frequency. Also, with two radiation sources you need to make sure what comes out of the mouth are just the frequencies you want; e.g. the low bass, that's the job of the compression chamber. If you don't get this right then the shorter wavelengths interfere between the two sources and the timing of the box is all to pot.

I'm not quite like ILPS who believes all BLH are the spawn of the devil but.....he has a certain point. BLH do scale, authority and all that really well on low power but the timing aspect is harder to get right. It all depends upon what set of compromises you are willing/can make.

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#14

Post by Andrew »

PS. the All Fun, from what I can see of the pictures, looks pretty good.

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#15

Post by Ray P »

Andrew wrote:If you read MJK (www.quarterwave.com) you will start to get a picture of the problem of how a BLH must, unless its truly huge, transition to a TL below a certain frequency. Also, with two radiation sources you need to make sure what comes out of the mouth are just the frequencies you want; e.g. the low bass, that's the job of the compression chamber. If you don't get this right then the shorter wavelengths interfere between the two sources and the timing of the box is all to pot.

I'm not quite like ILPS who believes all BLH are the spawn of the devil but.....he has a certain point. BLH do scale, authority and all that really well on low power but the timing aspect is harder to get right. It all depends upon what set of compromises you are willing/can make.

Andrew
Hi Andrew and thanks for the positive comments about the All Funs in your subsequent post.

I'm familiar with Martin King's work and yes any speaker, of whatever shape, size, approach, material, etc. (i.e. not just BLHs) is just a bunch of compromises. To be honest, I don't claim to be breaking new design ground (not my forte) but to be taking something that I know I like and seeing if I can revisit it to get more out of the design.

I understand the importance of the compression chamber in a BLH design and, interestingly, the volume of the Big Fun chamber doesn't really align with what the theory says it should be. With that in mind I'll be factoring in something that will allow experimentation with the compression chamber, probably with stackable rings that can increase/decrease the volume by making it longer/shorter.

Ray
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