# Horn/Transmission line help

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#### Harderror

Ok, so I fully understand horn equations and have now designed and built 2 absolutely fantastic functioning horn systems. I am now trying to design a compromised horn/transmission line as I am tired of having monstrous speakers sitting in my living room.

That said, I am having the hardest time figuring out how to alter the horn calculation (as per MJK) to place my TL resonant frequency at 50 HZ and changing the flare and length of the horn to take up the slack from the Fh down to where the TL action begins. I read MJK over and over and feel like I am beating my head on the wall. I am forever grateful for what he has done but a good deal of what he writes speaks only to mathematicians or phsics geeks. I understand a good deal of what he works with but get mired down by the extreme equations he discusses (such as those he uses Maple to calculate).

So, if anyone can help I would greatly appreciate it! SCOTT?! Thanks in advance!

We need MJK for dummies (ok, not dummies but non physicists/mathematicians.

For someone wanting to explain. I am trying a compromised 50Hz horn (1/16, .5 SD, for the FE 126).

Tom

#### ronc

For someone wanting to explain. I am trying a compromised 50Hz horn (1/16, .5 SD, for the FE 126).

I think its called the Frugal horn or the A126.

I am forever grateful for what he has done but a good deal of what he writes speaks only to mathematicians or phsics geeks.

And?

but get mired down by the extreme equations he discusses (such as those he uses Maple to calculate).
I cant think of many ways you can explain the actions besides math/physics.

I try to present examples of things ppl can relate to, but the actual definations can only be given in math/physics.
Even my methods differ somewhat from Martin as i depend a great deal on vector analysis.

ron

http://fullrangedriver.com/forum/viewtopic.php?id=91

This is about as simple as it gets.

#### hm

Hello,

http://www.fostexspeaker.de/newprods/fe126e.pdf

Xmax 0,35 mm that is nothing, let you show measurements or simulation from the "developer"
if there isn´t any be careful.

Better take a tested enclosure.

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#### planet10

Paid Member
hm said:
Better take a tested enclosure.

I can assure you that both the speakers Ron mentioned have been thoroughly tested. And further Ron has probably the most accurate simulation software for designing horns that exists.

dave

#### hm

show us the simulations and measurements!!

#### ghpicard

hm said:
show us the simulations and measurements!!

FWIW I'll give you my personal view on this respect.

1 - Simulations are just simulations. Well done, within the right context, they help a lot in a design or understanding of phenomena. If not done within the right context they mean nothing or even worse, they are misleading.

2 - Measurements are exactly the same thing, and if not done within a standard or at least very well defined frame of reference, with a specific intention (this is, to demonstrate or show a certain aspect of a system or device), they also could mean nothing.

Besides this is the fact that all things done or discussed in this forum are to be used in real rooms, outside of an anechoic chamber, and with heavily changing contexts. This is to say that I would personally takeany measurement and/or simulation on loudspeakers as merely indicative, except under very specific conditions.

Now, this said, both designs we are discussing here (A126, FH) were built several times and reported as working and working very good, in several different environments and by different persons.
Regarding to Ron and MJK, I personally know neither of them, but the show of their work and the reading on what they express on their many posts speaks for them and to me (personal opinion) they are voices to be listened to in this context.

Now, if you think that measurements and simulations mean everything and other people impressions on the build summed to the designers background mean nothing, please put that clearly this way, and remark it as a personal opinion.

Gastón

#### hm

Hello do know this threats,
about what is real and what not,
main threat:
http://www.diyaudio.com/forums/showthrea...=5&pagenumber=3
changed and stoped questions here
http://www.diyaudio.com/forums/showthrea...=5&pagenumber=1

do you know what dynamic compression is, and what happened
with sound and distrotion, do you know how much Xmax
is needed in a horn?
I think not.

if it works so good, and so many,
why is there no one outside to take a measurement.

Most horns are not built and tested, and if I see a
moderator is there involved, than I think there
is a conflict of interests.

Sorry, you know my side and experience, single driver
with such a low Xmax are going only 0,3 W.

#### Scottmoose

What 'threats', O great God Paranoidus-Supremeus?

Sigh. I would honestly like to be on good terms with you Horst, because I like to be on good terms with everybody, but you seem to have an attitude problem which is nothing to do with language (plenty of people speak far worse English than you and never a problem either way). Your posts are simply rude. You seem to be unable to post anything without rubbishing someone else's speakers. Itpains me to say this, but I think quite a few people around here would be eternally greatful if you'd either a) stop patronising everybody and make a useful post without attacking someone else for a change (go on, you know you want to... it's really not difficult to be polite.) , or b) take your arrogant attitude elsewhere. Most people seem to fall into the second category. Surely you wonder why you don't often get many replies to the threads you occasionally start?

Perhaps we haven't been very clear, so I'll try to be now.

1) We do not require you to tell us how to design speakers.

2) People here are not little children. Please stop addressing everyone as if they are.

3) We have heard of all things such as Xmax, dynamic compression and many others which you don't actually seem to be aware of yourself, such as focused radiation, end correction, the fact that horns do not have to follow a specific flare constant, the use of a folding scheme to attenuate high frequencies, amongst others. So you're in no place to cititicise a design using one or more of these features until you learn about it yourself, and maybe even try it. Please stop, until you have done so.

You don't seem to realise that all speaker design is a compromise, and that those you accept are not those other people accept. And don't try & tell me you don't have any. You're using multiple drivers, so double the cost. There's a compromise straight away. You're going omni with the drivers in several cases. This certainly has its benefits, but it's a compromise too: you reduced maximum acoustic power from the drivers at the listening position, and you're arguably doing something similar at the terminus, which frankly, WRT anything horn related is not a good idea IMO due to the directionality inherent to this type of speaker. The list goes on. And I don't care how low your speakers may go on a graph, unless you live in a shoebox, the bass SPLs will be limited because there's only so much air those 3in cones can shift. That's why people in the days of yore, when sound quality actually mattered, used multiple 12in or 15in drivers (horn loaded) if they could. And so the list continues.

So. We accept different compromises. Typically, though not invariably, one driver. Greater use of boundary reinforcement and focusing of radiation. The use of dedicated woofers to handle the lower octaves (you see, we make the assumption that people are intelligent enough not to need us to tell them that a 4 1/2in cone is not going to play the 32ft rack of a pipe-organ at 105db 15ft away from the speakers). Power handling: speaking for myself, I tend to take the Earl Geddes view -watts at 1m or whatever makes you happy means very little in practice, so citing them is relatively valueless. And so on. You don't like any of that? Fair enough. Not to your taste. But please understand that it can be for other people. Accept it.

Now then. Horns on Frugal-horn which have been built... let's see...

The Frugel-horn (many, many across the globe)
The A126 (ditto)
The A166 (ditto)
Dallas II & III (ditto)
The Daleks (at least 4 to the best of my knowledge)
The Metronomes (too numerous to count the different builds)
Harvey (a couple of dozen so far)Sachiko (couple of dozen & someone even tried to steal the design & flog for \$6,500 a pair)
Chang & Curved Chang (half a dozen)
Half-Chang (about a dozen & the same bloke who tried to steal the Sachiko design also tried to swipe this one & flog them at \$1,750 a pair)

Should I go on with the list?

Now, if I can ask you another question: are all rooms and corners the same?

#### Scottmoose

Tom, you've set yourself a difficult challenge, trying to do a 50Hz hybrid horn for the 126, which frankly isn't an especially easy driver to work with. Small units frequently aren't. The Frugel-horn & Ron's A126, as noted, can do it, no problem, and by reputation, Ed's Horns too. So if acoustic music is your staple diet, then you probably wouldn't need any more.

If you're after setting yourself a challenge to design something from scratch, things get a bit more complicated. Remember, MathCAD is only a modelling tool. It can't design a speaker for you, and you have to be aware of what it does and does not do in modelling terms too. For example, it can't show you the effects of bends, or a specific folding scheme on HF in the horn (nothing available can at present to the best of my knowledge, aside from Ron's own private software). Nor does it fully show the effects of end-correction etc. None of this is to denigrate Martin's work -quite the opposite. It's probably the best suite of all-round software available (I'm keeping my fingers crossed for a new set of front-horn & isobaric sheets, and, if possible, a tapped-horn sheet might be nice too. Akabak & Hornresp are great as far as they go, & have some features Martin's worksheets lack, but I still favour MathCAD.

A few general pointers, because if we went into it in detail, we'd be here 'til next Christmas. Firstly, the 126 really needs a ~optimal hyperbolic with a flare constant just below 0.5 to work well in a pure horn. Even though you're after a hybrid QW / horn, this is still a good indication: a long path with relatively slow initial expansion is a good starting point, which is what all the aforementioned designs have. End-correction is worth having in a compromised horn -it will reduce potential ripple, though the software won't show this fully. Don't go for too small a throat or you'll end up with a ludicrously long path. That was a mistake I used to make. Don't use the Fostex specs BTW -they're way off. Troel Gravesen has some better ones on his site. http://www.troelsgravesen.dk/FE126E.htm Don't make the air-cavity too large -the A126 & Frugel-horn are 2.2 litres which gives a nice blend of loading on the driver & a suitable upper corner-frequency for the cabinet. Smaller & you risk a very 'shut in' sound with a nasal midrange quality. Finally, I'd go for gain. You can always loose what you don't need.

#### hm

Hello Scottmoose,

sorry I can´t understand all,
and didn´t read all, and I won´t disturb a hobby.

But your list and the big sells make me wonder that there
is no measurement at all, more and more.

sorry.

#### ghpicard

hm said:
Hello Scottmoose,

sorry I can�t understand all,
and didn�t read all, and I won�t disturb a hobby.

But your list and the big sells make me wonder that there
is no measurement at all, more and more.

sorry.

I will chime in again... and try to cool things down a little.

The designs Scott refers to are 100% free for everybody for personal use. I would like to add that the BIBs are horns too and there are quite an amount of them already built, also without paying
a single cent for the design.

The lack of measurements is really easy to explain: this specific forum (and other single-driver forums) are mostly populated by people that want and like to build things, but some times don't know how to do that and other times don't care for measurements.
If this were a manufacturer's forum, perhaps I would feel suspicious, but in that case I would be suspicious of the measurements too.

I have to date built two set of horns (fostex recommended spirals and BIB 166s), I have the knowledge to do measurements, you can be certain on that, but simply don't care for measuring them. I don't need to. I like the way they sound and that's it.
I will in some moment make a mic preamp and will do the measurements just out of curiosity to know what I like and to check if my simulations align with what I measure and thus be able to correct the simulations.
But I like my speakers because of how they sound and not because of what they could or couldn't measure.

Gastón

#### Scottmoose

You might have got the wrong idea here Horst -I don't sell anything or make any money at all from the designs on the site. Everything there is free for people to build for their own use. The figures I gave were those a person who stole the designs was trying to sell them for commercially.

As I've said before, I believe your point regarding the measurements is fair enough -certainly if I sold speakers, I would make sure they were measured in a realistic situation. But I'm not selling speakers. I'd still like to be able to build & measure everything I do, but I can't. I don't have the time (PhD), money (none) or facilities (a garage that is flooded for the second time in 6 months, and a 30 year old hand saw is all I have).

However, we've got some of the most advanced software available, of proven accuracy at our disposal, and a lot of experience, plus friends who can advise on other points, so we use it. I promise you, if we were not happy in advance that something would work as intended, it wouldn't be there. There wouldn't be much point in deliberately putting something rubbish on the site would there?

My concern about measurements is that although they're useful, they don't tell you everything, and can in fact be misleading. It depends on how you take them. There wouldn't be any point in putting a corner-horn in an anechoic chamber, because it doesn't have the corners it's designed to use, correct? Measuing a double-horn at 1m is worthless if the wavefronts don't integrate until ~2.5m (depends on the design). And so on. Measuring in-room can be useful, but the problem with that is all rooms are different, so again, a speaker that measures well in one room wouldn't automatically in another. And so on. That's why I only view measurements as another tool, nothing more.

Regards
Scott

#### hm

why not, lets do it like this.

#### Fast1one

hm said:
why not, lets do it like this.
Not very good logic.

Do you have the same room as me? I have 8 foot ceilings, open to a flight of stairs, the kitchen and living room are not separated, 15x25 feet, a counter top in the center, carpet for the living room, linoleum for the kitchen, etc etc...

My point is, the room by far plays the BIGGEST role in the response of the loudspeaker, So unless we all had the EXACT same room (right down to the decor, couches, etc) any real world measurements are futile...

Not saying it ISN'T a bad thing to share, but I can't look at your measurements and expect the exact same output as you had in your environment, more than likely far from it...Measurements are for your own personal gain, to further improve and tweak the loudspeaker in your environment...

Regards,
Sergio

#### Andrewbee

I have built speaker designs from Scott, BIB with fe166esr, Ronc, A166 with same driver and Horst’s Schalmei Sat with the B200 Visaton. They all sound good.
So, whether or not there are measurements and no matter the manner in which they were designed and the compromises deemed acceptable they all work to my ears.

Am I the only one who has built one of Horst’s designs on DIYaudio?

Iirc the plans for the Schalmei Sat cost 10. Euro and the cost of a stamp, to post same.
Certainly worth it to me and I doubt, its making Horst rich.

Scotts designs are free, an even better price.

Which one is “better”? I don’t know.
I know I prefer the B200 in this design to an open baffle.

#### Scottmoose

hm said:
why not, lets do it like this.

Oh deary deary me.

Enough!

Back on topic, re the 126, something I forgot to mention is that if you wish to design your own cabinet Tom, & 50Hz is your goal, some form of boundary loading will be needed if you don't want to end up with a huge cabinet again. Corner-loading is easiest as you can maintain horn action lower -trying to balance QW & horn actions is probably the hardest thing to get right, so the more you can reduce the requirement, the better.

#### Harderror

Wow, I asked for help so I could do what this hobby is about, design. I didn't realize that it would spur responses that seem to me to go against what this hobby is about. I do this hobby not to build other peoples designs but to build mine. Did some of you forget this about your own building? Just because I don't use some custom designed software and have 50 years of knowledge about speaker building doesn't mean that my designs aren't valid. In my early times of speaker building I built some of the designs of other people including the Frugal Horn. Though they are good designs I decided that they were not what I was looking for and to be frank, I felt that if I worked hard I would be able to do better. This is entirely no offense to anyone on this forum or in the speaker buildilng community. I have designed and built two very successful horn systems (on my own) and believe I can do far more. If I want to understand the math in the calculations I don't feel that this is somehow wrong. Has this forum fallen to the point that the only people allowed to discuss the ideas behind design are the established on high designers? I hope not.

Now, no offense to anyone, I know Horst stirred up some of this but I had to vent a bit.

On another note. Scott, I really appreciate your feedback on this. Let me see if I can respond to some of your statement.

Tom, you've set yourself a difficult challenge, trying to do a 50Hz hybrid horn for the 126, which frankly isn't an especially easy driver to work with. Small units frequently aren't. The Frugel-horn & Ron's A126, as noted, can do it, no problem, and by reputation, Ed's Horns too. So if acoustic music is your staple diet, then you probably wouldn't need any more. /

I built the Frugals and didn't like them. Besides, I really love doing this because it is something I do myself. I want to understand to the fullest what goes on in this labyrinth we call a horn. The reason I blew through all the other speaker designs and settled on this one is A. Sound quality. (I believe that you just can't beat it) B. The mystery and the science of why it works. I am so damn fascinated by this that I just can't stop working on it now. I listen to a great deal of Jazz but also a huge amount of very powerful and severe Classical. Therefore, Frugal no and A126 no. The horns i shared with you last year are absolutely fantastic at symphonic as well as Jazz, Rock, you name it, they can handle it. The only problem? They are 2.5 feet deep a foot and a half wide and 4.5 feet tall. They have to be 3.5 feet in to my living room and that is becoming a problem (not that I would get rid of them).

If you're after setting yourself a challenge to design something from scratch, things get a bit more complicated. Remember, MathCAD is only a modelling tool. It can't design a speaker for you, and you have to be aware of what it does and does not do in modelling terms too. For example, it can't show you the effects of bends, or a specific folding scheme on HF in the horn (nothing available can at present to the best of my knowledge, aside from Ron's own private software). Nor does it fully show the effects of end-correction etc. None of this is to denigrate Martin's work -quite the opposite. It's probably the best suite of all-round software available (I'm keeping my fingers crossed for a new set of front-horn & isobaric sheets, and, if possible, a tapped-horn sheet might be nice too. Akabak & Hornresp are great as far as they go, & have some features Martin's worksheets lack, but I still favour MathCAD. /

Well, I am interested in the challenge. I am not using mathcad to design, I am using Martin's writing to design. The basic exponential horn equation has been my starting point from the start.

Mouth (1 / π) x (c / (2 x fc))2

Flare m = (4 π fc) / c

Length ln(Smouth / Sthroat) / m

Then I design the horn and alter measurements until I get a design that I like the looks of in the sim. I get something that looks pretty good and then build it to see what happens. Then I alter things to see if the sound will improve. A lot of trial and error as you well know. I will say though, the design I shared with you ended up blowing everyone away that has heard them. They are my primary pair now with a pair of 300b SETs (that I built) driving them.
Thank you though as that is a great answer. So, I can feel a little less tied to the math and more ready to go with my gut now.
I truly am blown away by Martin's work. I wouldn't be anywhere close to where I am without him. /

Firstly, the 126 really needs a ~optimal hyperbolic with a flare constant just below 0.5 to work well in a pure horn. Even though you're after a hybrid QW / horn, this is still a good indication: a long path with relatively slow initial expansion is a good starting point, which is what all the aforementioned designs have. End-correction is worth having in a compromised horn -it will reduce potential ripple, though the software won't show this fully. Don't go for too small a throat or you'll end up with a ludicrously long path. That was a mistake I used to make. Don't use the Fostex specs BTW -they're way off. Troel Gravesen has some better ones on his site. http://www.troelsgravesen.dk/FE126E.htm Don't make the air-cavity too large -the A126 & Frugel-horn are 2.2 litres which gives a nice blend of loading on the driver & a suitable upper corner-frequency for the cabinet. Smaller & you risk a very 'shut in' sound with a nasal midrange quality. Finally, I'd go for gain. You can always loose what you don't need.

Thank you thank you thank you. This is a great deal of help!

#### Scottmoose

I don't think the 126 is not going to do it mate. Not properly. You pick the tool you need to do the job, and if you're into big classical pieces, at high sound pressure levels, the 126 isn't exactly the unit that springs to mind -it's not quite blood out of a stone, but not far off. Something larger would be preferable & make your own task considerably easier.

Martin's paper is an excellent starting point for people new to horns, but it doesn't cover everything (such as hyperbolic / hypex / conical etc flares), & there are other works out there that will allow better optimisation to a specific drive-unit. Don't get me wrong, I'm not saying don't use it (far from it), just keep in mind that there are other papers too which can be used in combination with it. The heavy artillery are WML, Tom Danley & Earl Geddes. (Ron too I might add, but he hasn't published any papers on the subject AFAIK)

Of particular significance is WML's On the Specifications of Moving Coil Drivers, if you haven't already read it. The math will give you a major headache, but it's worth persevering with it. The equations are set so as to allow you to extract the maximum possible efficiency out of a driver -this has its downsides, but high-gain is usually preferable: just damp what you don't need. You can also download the nifty little programme MLUtil, based on these equations. It's worth still doing some manual work with them though so you can set appropriate upper & lower corner frequencies. The programme with then churn out dimensions which you can then enter into MathCAD & play with. Nice little bit of software & one I use quite a lot. Note these are still based upon the 1 dimensional wave equation (Rayleigh, Webbster etc) which are fine as far as it goes, but, as Earl & Ron point out(and Voigt, to be fair -think of the tractrix), this isn't everything. Wavefronts are not plane.

As I noted above, boundary reinforcement is your friend. If you can corner-load, then so much the better.

Remember, ripple in the frequency response of a compromised horn is caused principally by the terminus size not being large enough (i.e. the horn is acoustically small compared to the wavelengths it's trying to reproduce. The result is a standing wave (supersonic shockwave) which is reflected back from the terminus along the horn-path. The air-cavity behind the driver (we're assuming a typical BLH here) can't filter all of this off, and it modulates the driver, causing the ripples in the response.

There are a few things you can do about this. You can cram it full of damping (not a good idea: microdynamics vanish) make a large back-chamber (won't support the cone as well, so excursion increases & distortion at high SPLs rises. I'll come back to this in a minute though), or use the folding scheme to help. The main problem occurs at higher frequencies, right? A modestly sixed air-cavilty can't get all of them. However, HF hates bends with a passion. Short wavelengths. So, if you introduce a couple of bends near (but not too near) the throat, you will naturally filter off these, leaving only the LF to pass though (longer wavelengths aren't worried about the bends, so long as you don't go crazy & make something that looks like a python with heartburn.

Whatever you do, make sure the minimum length of your horn is 1/4 your target cut-off. For 50Hz, that's roughly 68in (depends on local speed of sound). Ideally, for maximum performance, 1/2 wavelength or greater is needed.

Oh yes: one last thought. (Chambered) back loaded horns = very small bass reflex cabinets with very large vents.

#### ronc

All this is fairly amusing. However any time someone shows passion for something they usually do a better job.

Therefore, Frugal no and A126 no. The horns i shared with you last year are absolutely fantastic at symphonic as well as Jazz, Rock, you name it, they can handle it. The only problem? They are 2.5 feet deep a foot and a half wide and 4.5 feet tall. They have to be 3.5 feet in to my living room and that is becoming a problem (not that I would get rid of them).

When i design anything i aim for a pratical approach, the factors indlude ease of build, cost, size and performance. I used the Austin programming that was developed for the A166 on the A126. Dave (planet 10) brought up the fact of a boxy sound. At first , being who i am and what i do, i wanted to argue the point(after all the math/physics was correct). But when i investigated i realized that one set of values do not apply to all conditions. By investigating i modified the programming and compensated for the falts with an increased baffle area. (Hense the suprabafle (name coined by Dave)). All this shows is i or anybody can be wrong in assumed math or physics. What i am stating (and doing a poor job of it) is math/physics do not include the human element. Simulations and even measurements do not always apply to every condition. However they do lead you in the right direction.
Its almost impossible to have a design of anything that meets all the requirements/conditions/outside influence of any given set of conditions. A F1 car is the fastest vehical on a race track that ever was, but in a 1/4 mile drag race a AA fuler will make it look silly(how many F1 do you see on the road going to get a gallon of milk?). Any broad/narrow range performance of anything will have given comprimises in other aspects.
All i have ever done in any of my audio designs was to give the best overall performance for an average set of requirements and conditions.

ron

#### ronc

Ron too I might add, but he hasn't published any papers on the subject AFAIK)

Lets see,my present assingments are.
1. Design a particulate removal system for FBE (Fusion Bonded Expoxy) for filters.
2. Design a one man portable plasma cutting system that can cut any designed shapes from a steel plate.
3. Design a phased array automated scanning system for the ultrasonic inspection of double joined pipe.
4. Design and install a water cooled laser measurement system to gage the thickenss of steel plate moving on a set of rollers at 2200 degrees F.
5. Answer the day to day technical/engineering problems.

Leaves me very little time to apply to anything.

ron

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