Hi Max,
convert the mouth area to an equal area circle.
Decide and apply a factor for open air (x1), one boundary (x2), two boundary (x4) and three boundary (x8) loading.
Find the circumferance of that equivalent circle.
Calculate the cut off frequency from Frequency = 340/circumference, from the observation that when the mouth circumference is greater than the wavelength of the pass band frequencies the "horn" follows the design equations.
Scott,
I do not know anything about the quarter wave loading and not enough about horns to argue.
But, please explain your reasoning.
convert the mouth area to an equal area circle.
Decide and apply a factor for open air (x1), one boundary (x2), two boundary (x4) and three boundary (x8) loading.
Find the circumferance of that equivalent circle.
Calculate the cut off frequency from Frequency = 340/circumference, from the observation that when the mouth circumference is greater than the wavelength of the pass band frequencies the "horn" follows the design equations.
Scott,
I do not know anything about the quarter wave loading and not enough about horns to argue.
But, please explain your reasoning.
Depends on the flare. But, to use a very quick example, a QWR with a 1:10 expansion ratio & 79.6in long will resonate at ~60Hz. That's linear expansion, so alterations will muck that up of course. Problem with pure horn theory is that it all tends to go pear-shaped when things are trunkated. Most BLHs are in reality QWRs at the bottom end shifting to horn loading higher up or they'd have to be Kleinhorn sized. That's why Martin King's work has been such a God (well, Martin 😉 ) send.
Max, what's the proposed throat CSA? With that, the horn length and mouth CSA, I can run a full-blown MathCad model on it for you.
Max, what's the proposed throat CSA? With that, the horn length and mouth CSA, I can run a full-blown MathCad model on it for you.
Thanks for the input guys,
Now I'm trying to get working an "Opus" DAC
I'll answer ASAP.
Scott, does CSA stand for circumference area?? Please, try not to use acronyms with your humble narrator
Andrew, factor is difficult: mouth is divided in two; one side is loaded to lateral wall and floor; the other side is loaded to floor and air or maybe a lateral panel (bass trap). I guess x4 would be...
Bye,
M
Now I'm trying to get working an "Opus" DAC
I'll answer ASAP.
Scott, does CSA stand for circumference area?? Please, try not to use acronyms with your humble narrator
Andrew, factor is difficult: mouth is divided in two; one side is loaded to lateral wall and floor; the other side is loaded to floor and air or maybe a lateral panel (bass trap). I guess x4 would be...
Bye,
M
Nothing to be sorry about...my fault, not yours.
Building started 😎
Please try these dimensions for a 2:3 Square Autograph for a ANsuper10:
Throat's CSA= 422cm2
Rear Horn length= 2.1m
Mouth's CSA: 6160cm2.
Throath's CSA can be diminished within certain limits easilly; for example to 366cm2...
Also the mouth can be made wider, wich expands rapidly the CSA.
Many thanks 🙂
M
Building started 😎
Please try these dimensions for a 2:3 Square Autograph for a ANsuper10:
Throat's CSA= 422cm2
Rear Horn length= 2.1m
Mouth's CSA: 6160cm2.
Throath's CSA can be diminished within certain limits easilly; for example to 366cm2...
Also the mouth can be made wider, wich expands rapidly the CSA.
Many thanks 🙂
M
Well now, quick sim here. I don't know the volume of the compression chamber, so I took a guestimate that the surface area of the top and bottom were roughly = 2Sd and it is about 12in tall. It's not massively important for the sub 100Hz regions -it simply determines how high the horn will operate before reachin its upper cut-off point. if you can give me HxWxD dimensions for the chamber Max, again, I can be more accurate. This should be fine for below 100hz though, which is what we're interested in here, right? Oh yes, I also assumed that the flare is ~exponential, which, knowing Tannoy, it should be.
Don't panic -because personally, I thing this is pretty good, especially considering I used no stuffing at all for the sim. One thing's for sure with a horn length like this, a mouth area like this, and a throat area of this size, you're not going to be lacking for LF gain. I imagine some tweaking will be needed in terms of damping the output. The Tannoy drivers are somewhat more sensitive units than the big AN driver so their output is more closely attuned to the horns. No matter though: IMO, it's much better to have too much gain than too little, as you can always damp it down, whereas if you've got too small an enclosure, it's a tricky old thing to boost what you haven't got in the first place. A lesson I learned from GM. Bigger is Better! This should be a very good project indeed IMO.
Without room-gain, F10 is 35Hz. With room lift, I'd expect that to be more like 25Hz. If you take the driver's nominal free air sensitivity, which they attain at about 180Hz as a starting point, then these things maintain that, or above, down to roughly 45Hz, with a -3db point of 40Hz. Again, without room gain. I think these are going to work rather well. 😉 Scott Likes!
Enjoy & let us know how you get on. Must see if someone can draw up a good set of CAD plans -these old Tannoy ones aren't the clearest, and are getting a bit creaky nowadays. I'd beg Dave, but he's enough on at present, especially with all the power lines in his neck of the woods down. Maybe in the new year, if I asked nicely... ;-)
Don't panic -because personally, I thing this is pretty good, especially considering I used no stuffing at all for the sim. One thing's for sure with a horn length like this, a mouth area like this, and a throat area of this size, you're not going to be lacking for LF gain. I imagine some tweaking will be needed in terms of damping the output. The Tannoy drivers are somewhat more sensitive units than the big AN driver so their output is more closely attuned to the horns. No matter though: IMO, it's much better to have too much gain than too little, as you can always damp it down, whereas if you've got too small an enclosure, it's a tricky old thing to boost what you haven't got in the first place. A lesson I learned from GM. Bigger is Better! This should be a very good project indeed IMO.
Without room-gain, F10 is 35Hz. With room lift, I'd expect that to be more like 25Hz. If you take the driver's nominal free air sensitivity, which they attain at about 180Hz as a starting point, then these things maintain that, or above, down to roughly 45Hz, with a -3db point of 40Hz. Again, without room gain. I think these are going to work rather well. 😉 Scott Likes!
Enjoy & let us know how you get on. Must see if someone can draw up a good set of CAD plans -these old Tannoy ones aren't the clearest, and are getting a bit creaky nowadays. I'd beg Dave, but he's enough on at present, especially with all the power lines in his neck of the woods down. Maybe in the new year, if I asked nicely... ;-)
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Oh! Scottmoose, that is an excellent work! 🙂
So for a starting point, based on intuition and wisdom transmited from GR Foutain's spirit, it should be comparable to my, now gone for sale, Tannoy Definition 500, wich had a -3db at 40Hz 🙂
BUT, with the dynamic contrasts and the articulation of the mini Autographs 😎
These would be located on front wall corners, stuck to both lateral walls to expand the mouth and with maybe panels added to the half of the horn that faces innards (medial, in anatomic langue)...so a better LF response is anticipated.
Does F10 mean frequency at -10db?
So, modding the volume/SCA of the compresion chamber will help me cut off lower the upper response and have less midbass garbage going out of the mouths? Sorry, I'm learning here
I have seen somewhere (maybe hylberink's site) that one can put a tranverse wood piece here to "filter" midbass output. Maybe that will be easier?
Well, compresion chamber should be the space that goes immediatelly after the transducer right?
Dimensions will be(from memory) : 24cm*18.66cm*24cm; LESS 864 cm3 and LESS 588cm3, all from oblique reflecting panels...weird chamber. I hope I did not make mistakes.
I if looks strange, tell me...
So, it could be a nice project...I'm building the 1:3 version of this one (half) and I can tell that it is much more easy than the real Autograph to build! 😎
I HATE SQUARE BOXES
Many thanks,
M
PS: 24cm are to be substracted to rear horn length, as these first cm belong to compresion chamber (?)
So for a starting point, based on intuition and wisdom transmited from GR Foutain's spirit, it should be comparable to my, now gone for sale, Tannoy Definition 500, wich had a -3db at 40Hz 🙂
BUT, with the dynamic contrasts and the articulation of the mini Autographs 😎
These would be located on front wall corners, stuck to both lateral walls to expand the mouth and with maybe panels added to the half of the horn that faces innards (medial, in anatomic langue)...so a better LF response is anticipated.
Does F10 mean frequency at -10db?
So, modding the volume/SCA of the compresion chamber will help me cut off lower the upper response and have less midbass garbage going out of the mouths? Sorry, I'm learning here
I have seen somewhere (maybe hylberink's site) that one can put a tranverse wood piece here to "filter" midbass output. Maybe that will be easier?
Well, compresion chamber should be the space that goes immediatelly after the transducer right?
Dimensions will be(from memory) : 24cm*18.66cm*24cm; LESS 864 cm3 and LESS 588cm3, all from oblique reflecting panels...weird chamber. I hope I did not make mistakes.
I if looks strange, tell me...
So, it could be a nice project...I'm building the 1:3 version of this one (half) and I can tell that it is much more easy than the real Autograph to build! 😎
I HATE SQUARE BOXES
Many thanks,
M
PS: 24cm are to be substracted to rear horn length, as these first cm belong to compresion chamber (?)
F10 is final cut-off, the point at which the red line, indicating system performance, meets the dotten blue line, which indicates how the driver would function in an infinite baffle environment. It's past midnight here, so I'll re-check with these dimensions for the the filter chamber later in the morning, after catching up on some rack time.
Filter chambers do a few things, but at a basic level, as you rightly say, they determine the upper cut-off of the horn (mouth size & QW loading determining the lower cut off, otherwise known as Fc). The smaller the chamber, the higher the horns will operatate. Unsurprisingly, the larger the chamber, the lower the horns uppoer cut-off point will be. So yes; a larger chamber will let less through the horns. I'd avoid going to extremes though -anything up to ~200Hz should be fine. Tweaking the chamber volume by adding bags of sand, stuffing etc is a common tweak, as you'll know from personal experience.
Filter chambers do a few things, but at a basic level, as you rightly say, they determine the upper cut-off of the horn (mouth size & QW loading determining the lower cut off, otherwise known as Fc). The smaller the chamber, the higher the horns will operatate. Unsurprisingly, the larger the chamber, the lower the horns uppoer cut-off point will be. So yes; a larger chamber will let less through the horns. I'd avoid going to extremes though -anything up to ~200Hz should be fine. Tweaking the chamber volume by adding bags of sand, stuffing etc is a common tweak, as you'll know from personal experience.
Many thanks for that excellent explanation 
So I need a big chamber to avoid midbass contamination through the horns...i thought it was the other way round
Cheers,
M
So I need a big chamber to avoid midbass contamination through the horns...i thought it was the other way round
Cheers,
M
Hi,
if the area compression ratio from cone : throat is 2:1 or less then the throat opening (>225mm diameter for a 15inch driver) forms a very large proportion of the chamber.
How well does the low pass filter work when the compression ratio is low?
if the area compression ratio from cone : throat is 2:1 or less then the throat opening (>225mm diameter for a 15inch driver) forms a very large proportion of the chamber.
How well does the low pass filter work when the compression ratio is low?
Yeah, good question. 🙂
Compresion chamber and throat's SCAs are comparable here, unless y make some minor tweak.
Compresion chamber and throat's SCAs are comparable here, unless y make some minor tweak.
Should be OK. We'll see what Martin's MathCad sheets say. Haven't had time to run any sims today on the proper chamber volume, but it's not that far removed from my guesstimate, so I doubt there'll be a problem. I'll check in the morning.
Don't worry.
The beauty of this is that I (we) can design and then mod easily the enclosure to our taste...
For example, make compresion chamber slightly bigger and rear horn longer, with wider mouth, to end with a narrower and deeper bass response from it...am I wrong?
Cheers,
M
The beauty of this is that I (we) can design and then mod easily the enclosure to our taste...
For example, make compresion chamber slightly bigger and rear horn longer, with wider mouth, to end with a narrower and deeper bass response from it...am I wrong?
Cheers,
M
Nope, you're quite correct. In a 'real' horn, Fc (lower cut off) is determined purely by mouth size, the upper cut-off of the horn is determined by the volume of the filter chamber, while gain across the passband of operation is set by throat CSA, and path length. The length necessary will vary with the flare selected: tractrix flares require the least length, conical the longest. Exponential falls somewhere in between these two, as does hyperbolic -the former is near the shorter end, the latter near the longer (usually). Flare is chosen for a host of factors -usually lowest distortion married to reasonable length.
In the case of these hybrids (anything under the size of a Kleinhorn is a hybrid to a greater or lesser extent. Lesser, in the case of these monsters) the chamber keeps it's job, but Fc as well as passband gain is / are determined by a mix of mouth area and line length as we're using QW action to help boost the LF and shifting to horn loading higher up the passband of operation. So, increasing mouth area, and line length, will lower Fc, while increasing the size of the filter chamber will narrow the passband of horn operation.
In the case of these hybrids (anything under the size of a Kleinhorn is a hybrid to a greater or lesser extent. Lesser, in the case of these monsters) the chamber keeps it's job, but Fc as well as passband gain is / are determined by a mix of mouth area and line length as we're using QW action to help boost the LF and shifting to horn loading higher up the passband of operation. So, increasing mouth area, and line length, will lower Fc, while increasing the size of the filter chamber will narrow the passband of horn operation.
Dear Scott,
I couldn't have said it better 😀
No, really, thanks for saving me hours of study
If I were to increase chamber volume, I could easily increase its height, as there is plenty of room there.
Best regards,
Mauricio
I couldn't have said it better 😀
No, really, thanks for saving me hours of study
If I were to increase chamber volume, I could easily increase its height, as there is plenty of room there.
Best regards,
Mauricio
If you want the full-blown background to hybrid horn loading, Martin King's site is the place to get it:
http://www.quarter-wave.com/Horns/Horn_Theory.html
Also, Leach's horn paper: http://users.ece.gatech.edu/~mleach/papers/HornPaper/HornPaper.pdf There are some gaps here, but this was the paper which took a lot of guesswork out of horn design. problem is, very few horn designers ever read it.
http://www.quarter-wave.com/Horns/Horn_Theory.html
Also, Leach's horn paper: http://users.ece.gatech.edu/~mleach/papers/HornPaper/HornPaper.pdf There are some gaps here, but this was the paper which took a lot of guesswork out of horn design. problem is, very few horn designers ever read it.
Ah! Yes! that seems a great knowledge base.
The sad part of the story is that so few (if any) will try these babes...the Metronome seems so much easier to build 😀
Though the "square" version is easy enough!
Maybe a dear moderator could send the modding part of this thread to its own thread?
Bye,
M
Hi Scott,
for some reason the PDF keep locking up this PC.
I went back to my old copies (Feb 2006) and searched for Klein in each of the downloads. No luck.
Where do I find the reference to
for some reason the PDF keep locking up this PC.
I went back to my old copies (Feb 2006) and searched for Klein in each of the downloads. No luck.
Where do I find the reference to
or something in that topic that defines the size of a hybrid or a Kleinhorn?
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