Greetings!
I'm currently using All Fun horns with Lowther EX4 drive units; love what they do but I'm getting the itch to do a Big Fun, but with a difference...
Using the Big Fun tractrix profile I'm thinking of a less compromised solution than rectangular sections folded inside a box; think round profile vaguely resembling a saxophone shape.
Now, I'm confident of being able to build an accurate male plug and I've experience of working in laminates but the area I'm not sure about is what to mould them in from the sonic perspective; obvious possibilities for materials include:
1. Glass Reinforced Plastic (fibreglass)
2. Papier Mache
But I'm not sure of the sonic properties of these materials and whether they would undermine the effort of developing the mould? And, of course, there may be other possibilities for moulding solutions (plaster?).
I know horns like the Azuras are moulded in GRP but they're somewhat smaller?
Any experiences/advice/suggestions gratefully received.
Ray
I'm currently using All Fun horns with Lowther EX4 drive units; love what they do but I'm getting the itch to do a Big Fun, but with a difference...
Using the Big Fun tractrix profile I'm thinking of a less compromised solution than rectangular sections folded inside a box; think round profile vaguely resembling a saxophone shape.
Now, I'm confident of being able to build an accurate male plug and I've experience of working in laminates but the area I'm not sure about is what to mould them in from the sonic perspective; obvious possibilities for materials include:
1. Glass Reinforced Plastic (fibreglass)
2. Papier Mache
But I'm not sure of the sonic properties of these materials and whether they would undermine the effort of developing the mould? And, of course, there may be other possibilities for moulding solutions (plaster?).
I know horns like the Azuras are moulded in GRP but they're somewhat smaller?
Any experiences/advice/suggestions gratefully received.
Ray
One point to keep in mind is that your 'less compromised solution' may actually end up more compromised than the original. The requirements of back-horns are not necessarily the same as those of an unfolded midrange (front) horn. Back horns, like all vented back-loads are only useful over a limited BW, above which you want a fairly rapid acoustic low-pass to prevent the delayed higher frequencies from interfering with the direct radiation of the driver. Smooth curves will have little impact on the LF, where wavelengths are too long to care tuppence about bends, but they tend to promote maximum efficiency at the top of the horn's useful BW -i.e. right where you (more times than not) don't want it. The bends in a folded horn can in fact provide a useful low-pass effect -in some horns they're actually a functional part of the design.
Thanks Scott.
Just goes to show how much I know!
I thought that the compression chamber/throat area acted (along with the basket on the back of the Lowther EX drivers) acted as the acoustic filter but it's obviously not that simple (things seldom are). I think you're telling me that in a smooth rounded horn the higher freq. components that are 'allowed' into the horn could be 'louder' and cause an imbalance in the sound?
I've attached an image of the initial CAD sketch (still under construction so ignore the construction lines around the drive unit housing)...
Just goes to show how much I know!
I thought that the compression chamber/throat area acted (along with the basket on the back of the Lowther EX drivers) acted as the acoustic filter but it's obviously not that simple (things seldom are). I think you're telling me that in a smooth rounded horn the higher freq. components that are 'allowed' into the horn could be 'louder' and cause an imbalance in the sound?
I've attached an image of the initial CAD sketch (still under construction so ignore the construction lines around the drive unit housing)...
An externally hosted image should be here but it was not working when we last tested it.
Well, low pass filter chamber anyway (the room is the compression chamber in a back loaded horn). Yes, that's what it's there for, but in the majority of cases some additional help doesn't go amiss.
Correct, it tends to promote maximum efficiency at the top end of the horn's operating BW, where most of the time you're likely to want less energy. Not necessarily disastrous -there are a few back-horns out there with smooth profiles that seem to be liked well enough -the defunct Gemme Audio Concerti 108 (the Fostex 108ESigma design smoothed out); the Arcadian Audio Pnoe, DIY Hedlund Horn design etc. come to mind. If unwanted midrange leakage is an issue, you could always add some damping to the horn itself. Just something to be aware of.
Correct, it tends to promote maximum efficiency at the top end of the horn's operating BW, where most of the time you're likely to want less energy. Not necessarily disastrous -there are a few back-horns out there with smooth profiles that seem to be liked well enough -the defunct Gemme Audio Concerti 108 (the Fostex 108ESigma design smoothed out); the Arcadian Audio Pnoe, DIY Hedlund Horn design etc. come to mind. If unwanted midrange leakage is an issue, you could always add some damping to the horn itself. Just something to be aware of.
Hello,
looks like that:
http://www.audioevidence.com/images/carfrae_bighorn_small.jpg
i think your presschamber is to large, you need a bit low mids off the horn
to balance it to the driver.
looks like that:
http://www.audioevidence.com/images/carfrae_bighorn_small.jpg
i think your presschamber is to large, you need a bit low mids off the horn
to balance it to the driver.
I agree from the perspective that the back-chamber appears very long in the drawing -there may be an issue with standing waves there, since the physical shape of the chamber affects behaviour, as does the location of the throat in it.
I'm rather more wary however that you actively want low-midrange coming out through the horn. Of course, this depends on what you mean by 'low midrange', but as a rule of thumb, anything > ~300Hz is increasingly problematic. Group delay becomes a major issue as frequency increases, and very obvious as the delayed output from the horn interferes with the direct radiation from the drive unit. If the -3dB mass-corner frequency of the Lowther is still higher than that once any Eq / the output impedance of the amplifier is accounted for, then ideally, you'll need an additional front midrange horn to 'fill in' the gap between the bass horn's upper corner frequency & the driver's mass-corner rolloff. Unless you're willing to put up with a dip in the response -depends how broad & deep it is of course, or said GD by letting the bass horn run up higher -it doesn't bother some people, so YMMV.
I'm rather more wary however that you actively want low-midrange coming out through the horn. Of course, this depends on what you mean by 'low midrange', but as a rule of thumb, anything > ~300Hz is increasingly problematic. Group delay becomes a major issue as frequency increases, and very obvious as the delayed output from the horn interferes with the direct radiation from the drive unit. If the -3dB mass-corner frequency of the Lowther is still higher than that once any Eq / the output impedance of the amplifier is accounted for, then ideally, you'll need an additional front midrange horn to 'fill in' the gap between the bass horn's upper corner frequency & the driver's mass-corner rolloff. Unless you're willing to put up with a dip in the response -depends how broad & deep it is of course, or said GD by letting the bass horn run up higher -it doesn't bother some people, so YMMV.
Gents, I haven't actually defined a filter/compression chamber, the clue is here...
Ray
Ray
Probably a misunderstanding due to the in-exactitude of the English language; I'm not planning to allow anything above 300Hz or so into the horn, just reflecting that it's not a brick wall filter so some mid-range will, presumably, enter the horn. I'm planning to experiment with chamber volume to 'tune' the sound.
Ray
Having the driver in a small circular baffle will affect the frequency response a lot compared to larger baffle (True Audio TechTopics: Diffraction Loss). It is good to get the baffle step increas in driver output to be coordinated with the lowpass of the horn output. Visually the big horn you design is far more interesting than a large box with big openings in the lower part of the side wall as the big fun. From an accoustical point of wiew the main limitations of bass horns are, mouth size, horn lenght and delay and neither of those are adressed by that good looking curves. I do not want to come across in a negative way but do not expect the basshorn to behave fundamentaly different in the bass range if you keep flare, lenght and areas but change the path to smooth curves. A circular cross section is good at reducing panel resonances compared to flat baffles comprising the horn sections but the intrinsic behaviour of the basshorn is not that sensitive to the geometry of the cross section geometry unless you have really odd shapes.
Hello,
before built i would simulate the membran movement and IMP,
then i would think about a double horn,
linear IMP and lowest movement down to 35 Hz
look my newest "small" double horns
http://www.diyaudio.com/forums/full-range/245962-kangling-double-horn-technic.html
http://www.diyaudio.com/forums/full-range/249361-mini-posaune.html
before built i would simulate the membran movement and IMP,
then i would think about a double horn,
linear IMP and lowest movement down to 35 Hz
look my newest "small" double horns
http://www.diyaudio.com/forums/full-range/245962-kangling-double-horn-technic.html
http://www.diyaudio.com/forums/full-range/249361-mini-posaune.html
Thanks for the interest and feedback. Yes, this aspect is something I'm aware of but haven't bottomed-out yet. I haven't discounted some sort of baffle or going for the small round 'pod' approach and experimenting with filters. Remember that the CAD sketch I posted is just my thinking on the horn duct itself (from the perspective of creating a male mould) and doesn't necessarily reflect the outer shape. It has crossed my mind to mould in plaster, sculpting the outer shape...
That's why I chose the BigFun as my starting point; it is, generally, considered to be a 'good' design and should deliver a little more bass extension compared with my smaller AllFun horns (conventionally folded in a box). If I can get that basic BigFun performance but at the same time make something that looks a bit more interesting I would consider that a success. Another aspect of round sections that is a practical bonus is that, in this design, they will fit more snugly into room corners so take up less floor space....
Ray
Hi Horst. I've had a good look around your website and some interesting ideas/designs. I'll be back to study further.
One of my criteria is to use my existing flea-power amplifiers, around 1.5W of SE-OTL per channel. What sort of efficiency/impedance are you achieving with something like your RDH20? The lowther EX4 units I have are amp-friendly 15ohm versions.
I've managed to tie myself up in knots now I've started to consider the baffle step issues around the drive unit mounting/chamber shape.
I understand the basic tenet, that with narrower baffles there is a loss of bass, however, in the BigFun horn type arrangement the bass (at least from around 300Hz downwards) exits the rear of the horn into the corner of the room; presumably essentially unaffected by the baffle step issue?
At point higher up in frequency the output of the lowther will also be unaffected by the baffle step even with a small round baffle.
That leaves us with a 'bit in the middle' where the baffle size (or lack of it) starts to be seen as a fall in output from the lowther before the bass horn kicks in at circa 300Hz, resulting in a dip in the frequency response through the 'bit in the middle'.
Is my thinking so far correct?
Assuming I'm on the right track, I'll need to devise a baffle that is just right to compensate for the dip; suggestions for a simple way of some initial modelling?
Thanks
Ray
I understand the basic tenet, that with narrower baffles there is a loss of bass, however, in the BigFun horn type arrangement the bass (at least from around 300Hz downwards) exits the rear of the horn into the corner of the room; presumably essentially unaffected by the baffle step issue?
At point higher up in frequency the output of the lowther will also be unaffected by the baffle step even with a small round baffle.
That leaves us with a 'bit in the middle' where the baffle size (or lack of it) starts to be seen as a fall in output from the lowther before the bass horn kicks in at circa 300Hz, resulting in a dip in the frequency response through the 'bit in the middle'.
Is my thinking so far correct?
Assuming I'm on the right track, I'll need to devise a baffle that is just right to compensate for the dip; suggestions for a simple way of some initial modelling?
Thanks
Ray
hello, I did the same thing except I did model the horn in 3d. I wish i can find a 3d printer to make this model. the model in the pictues is about 6 ft. tall.
Tony
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I was referring to the human figure in the model as about 6 ft tall. So where can I fine a 3d printer that can print this horn? I could cut sections of the horn and assemble the pieces together. It would still require a large 3d printer. So can it be done?
nautibuoy:
From the size, scope, and difficulty in making your creation you would be better off IMHO making a 3 or 4 way horn system. There would be far less compromise sound wise and easier to build. You would have better overall choices with drivers and waveguides/horns. Check out Volvotreters site, Inlow sound, DIY sound group. With your skills you can make a great speaker system. For dynamics, nothing will beat a front loaded horn system.
From the size, scope, and difficulty in making your creation you would be better off IMHO making a 3 or 4 way horn system. There would be far less compromise sound wise and easier to build. You would have better overall choices with drivers and waveguides/horns. Check out Volvotreters site, Inlow sound, DIY sound group. With your skills you can make a great speaker system. For dynamics, nothing will beat a front loaded horn system.
Regarding the baffle step. To get it you have to have a driver that is more or less omnidirectional at the frequency range in question. So speaker cones are that to some hundred of Hertz. So a baffle that dips in the region where the bass horn comes in is OK.
If you really are in love with the Lowther concider building a short front horn for the driver like Lowther did in the TP-1 But then use bass horn like the Klipsch corner horn below 200 Hz or so. The slam and seemingly endless power reserve of a a pair 15" drivers in corner horns is addictive. The nice thing is also that they sound very dynamic even at really low volumes as well, good for the WAF!
If you really are in love with the Lowther concider building a short front horn for the driver like Lowther did in the TP-1 But then use bass horn like the Klipsch corner horn below 200 Hz or so. The slam and seemingly endless power reserve of a a pair 15" drivers in corner horns is addictive. The nice thing is also that they sound very dynamic even at really low volumes as well, good for the WAF!
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