GoodSoundClub - Romy the Cat's Audio Site

Horn-Loaded Speakers
Topic: The quest for insight

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Posted by Blaukopf on 07-04-2015

Hi everybody, after reading RomytheCat's Macondo Setup I am very impressed ( phantastic music room ...) . Presently I have no working horns ( they are boxed), just questions.

First, Romy describes his horns as spherical. Later he names them tractrix. Are some of the profiles of the spherical wave profile ? Bruce Edgar wrote : You will be very disappointed in the bass response with a Tractrix horn. The bass response near the flare frequency cutoff is limited by the throat reactance, which peaks at the flare frequency . The horn is loaded for the most part by the throat resistance. Any reactance loading will reduce the output. In exponential and hyperbolic- exponential bass horns you can cancel out the throat reactance with the back chamber, but with a tractrix horn it is too short and the back chamber doesn't cancel out the throat reactance. Tractrix is great for mid bass and midrange but a terrible choice for bass. Where does the bass frequency start ?

My sims with hornresp show a good loading for a tractrix profile even at 80 Hz cutoff frequency - horn is huge of course. same for a spherical wave profile. How are they different soundwise ?

Can I believe the sim ? The throat radius measures 12 cm for a 15" driver and the mouth has a radius of 68 cm. Since the horn ist shorter ( than an exponential) , I would use it from a higher frequency - 110-120 Hz maybe. Next driver is a 2" DCM50 ( 500Hz up) and a 1" driver from 8000 Hz or a tweeter.

My dilemma : Exponential horns may load better but in a setup I prefer to have the same profile for all horns. Could you give some insight into this thorny question ? PS there were some excellent statements by JLH on push-pull TH ( am building one myself) but the images have unfortunately disappeared.

Thanks to all ! Marc

Posted by Romy the Cat on 07-04-2015

Blaukopf wrote:
First, Romy describes his horns as spherical. Later he names them tractrix. Are some of the profiles of the spherical wave profile?

Yes, they are spherical, wish means not rectangular. Everything but midbass are Tratrix. I do not know what is the “spherical wave profile.”

Blaukopf wrote:
Bruce Edgar wrote : You will be very disappointed in the bass response with a Tractrix horn. The bass response near the flare frequency cutoff is limited by the throat reactance, which peaks at the flare frequency . The horn is loaded for the most part by the throat resistance. Any reactance loading will reduce the output. In exponential and hyperbolic- exponential bass horns you can cancel out the throat reactance with the back chamber, but with a tractrix horn it is too short and the back chamber doesn't cancel out the throat reactance. Tractrix is great for mid bass and midrange but a terrible choice for bass. Where does the bass frequency start ?

Well, Bruce Edgar is right but to understand him literally as some kind of firm postulation would make Bruce Edgar wrong. You need to understand that Bruce Edgar customers are generally idiots and whatever he does and say is targeted for semi-idiotic perception and presume that a person is lacking of any personal practicing and thinking. Yes, the bass response limited by the throat reactance and in long horns you can “cancel” throat reactance with the back chamber. In reality you do not cancel anything but you just balanced it out. Do you think the very same does not take place in short (Tratrix and alike) horns? Absolutely the same process. The effectiveness of the “cancelation” of throat reactance by back chamber is less with Tratrix but at the same time Tratrix is shorter then exponential, the mass of air on the horn is lower and consequentially the amount of the throat reactance per the same cut off is substantially lower. Again, it is not the rule but different degree how throat reactance impact different profiles. The different profiles do have own sounds but it has not so much to do with throat reactance but rather deepens from very many reasons: location of horns, how room modes used, cut off and slope, type of crossover, type of driver, type of loading, exit profile, and so on and so on. I would still do not use Tractrix for bass but where bass frequency start in this context is a subject of debates and specific condition of a given installation. Bruce would say that “you will be disappointed in the bass response with a Tractrix horn” but I would retort it that Tractrix would lose in amplitude response but clearly will in quality of bass. Exponential and Tractrix bass are different if they properly implemented with respect to own topology. Yes the long horn would have “more bass” but it is very much not the final destination.

Blaukopf wrote:
My sims with hornresp show a good loading for a tractrix profile even at 80 Hz cutoff frequency - horn is huge of course. same for a spherical wave profile. How are they different soundwise ?

Again, you are looking for answer of your general question but the question is formulated faulty. I do not care what hornresp shows – trash this piece of crap or talk about it with the Morons from DIYaudio sites. If you appreciate what is done in Macondo and ask about the tractrix profile of 80Hz then I would ask what the hell you doing to use 80Hz tractrix? The 80Hz tractrix my nature of being too long and too large exclude any time alignment. Are you building horns or Sound? With my experience I see absolutely no use of 80Hz tractrix unless it is some kind of super exotic installation, something that you most likely do not plan.

Blaukopf wrote:
My dilemma : Exponential horns may load better but in a setup I prefer to have the same profile for all horns. Could you give some insight into this thorny question ? PS there were some excellent statements by JLH on push-pull TH ( am building one myself) but the images have unfortunately disappeared.

Marc, I do not think that to have the same profile for all horns is proper objective. You do not integrate profile but sound. Trust me if one know what he is doing you can with any profile get good results. I do not know what you are doing and you did not explained in details your ideas in order to solicit any sensible and practical advice. Your debate about short horn vs. long for bass is valid but lacking context. If you are taking about Macondo then it would not be possible to use a long horn for uperbass and it would be a good 2 feet longer and I would not be able to time-align the horns.

Posted by Blaukopf on 07-05-2015

Hello Romy, thank you for the answers. Your horns have a round mouth, but their profile is not spherical. That is the profile of the Avantgarde Horns you formely had - apparentyl you have anayzed them intensively, could you elaborate what problems you found ? Kugelwelle = Spherical Wave profile invented by Klangfilm-Siemens. Not Tractrix, on Wikipedia it is also wrong. My setup is : double tapped horns up to 150 Hz. Midbass-Horn from 150 - 500 Hz, then a 2" CD and a 1" CD.If you use the excel sheet by volvotreter, for a tractrix horn of 80 Hz cutoff the usable frequency starts at 170 Hz, lenght is 93 cm. looking at a horn by JLH it seems that he has added a long tube at the throat - is this to increase bass-loading ? have a nice day ! Marc

Posted by Romy the Cat on 07-05-2015

Blaukopf wrote:
Hello Romy, thank you for the answers. Your horns have a round mouth, but their profile is not spherical. That is the profile of the Avantgarde Horns you formely had - apparentyl you have anayzed them intensively, could you elaborate what problems you found ? Kugelwelle = Spherical Wave profile invented by Klangfilm-Siemens. Not Tractrix, on Wikipedia it is also wrong.

Mark, I do not want to be involved into discussion of what is a true Spherical horn. There is some controversy in there but not on the level you cover the subject. When Klangfilm introduced own profile they did claimed that they have true spherical diffusion but it is only because no one did at that time Tratrix commercially. BTW, even though the Klangfilm profile was “better” from spherical perspective but they never got any spherical results as they did only rectangular horns that are not able to do spherical waves. Anyhow, in my langue when I say that I use spherical horns I mean that I use round short horns. How it complies with Wikipedia I do not care.

Blaukopf wrote:
If you use the excel sheet by volvotreter, for a tractrix horn of 80 Hz cutoff the usable frequency starts at 170 Hz, lenght is 93 cm.

I do not accept the premises of the question. What do you mean: the 80Hz horn with usable frequency starts at 170 Hz? It is not MF horn but upper bass horn and it usable frequency shall not be too far from the horn rate. Also, tractrix horn of 80 Hz, what is it? A tip #1: never think about a horn without a context of the rest of the channels.

Blaukopf wrote:
looking at a horn by JLH it seems that he has added a long tube at the throat - is this to increase bass-loading

Nope, there was nothing was added. It is very straight forward tratrix horn of 38” mouth with very classic profile.

Posted by rowuk on 07-05-2015

Dear blue,
I think that you are reading this site incorrectly.
Romy has done an incredible job of documenting his personal audio travels. Consider this site to be a diary in that respect. It has absolutely nothing to do with DIY, except perhaps as motivation to work on the purpose of our audio travels instead of a roadmap to some theoretical hardware solution. Sure he has spent a lot of time examining his own motivations and results. Much of this is documented here. I am convinced, even if someone duplicated Macondo/Melquiades, the results would be different, perhaps not even satisfactory sound. Most do not know what to do with Bruckner sound.......
It makes no sense to discuss flare rate or calculations from some software as there is no correlation between the math and SOUND. All of those tools only give you "pressure" curves devoid of any sonic behavior. This is perhaps useful to plan how much wood that you need......
If you are interested in Midbass horns, search for them here. There are several interesting threads by people that have built them (including Romy) and documented the results. There are several threads about integration of different horns. After reading them, the nature of questions changes quite a bit because the recipe changes from hardware to sound.
Good luck in your journey. Just about all of the answers are here but they most definitely are not a Bill Of Materials, rather a journey through time.

Posted by Blaukopf on 07-05-2015
fiogf49gjkf0d Romy and rowuk, sorry for asking the wrong questions. Thank you and have a nice day. Marc

Posted by rowuk on 07-05-2015

I am not sure if the questions are wrong. Maybe they are just too early. There are plenty of audio people that pass around opinions as fact. That is a problem and most DIY pride is not in the absolute quality of sound, rather that it works, has wide frequency response and low noise and im some cases looks attractive.
That may be enough for many but there are those that want more. That more does not start with hardware or horn taper.

Posted by Romy the Cat on 07-05-2015
fiogf49gjkf0d Marc, i do not feel that you ask wrong qestions. Let me give an assosiation: what would be the best piano to produce D# minor? Probobly it would be irelevant qestion without knowing the context, dont't you think so? The very much with you questions about horns: are you trying to render an isolated horn project or your playbak has more noble intentions?

Posted by steverino on 07-07-2015

I think the issue is not the questions per se but what Musical result are you looking for? We all have make or break criteria for listening to music through audio systems whether stated or unstated. Experience has shown that you need to define the goal first as clearly as you can, not in terms of the engineering specs (or the room the system will be placed in) but in terms of the result desired. If you want to play Bruckner at concert levels as a main criterion you would be pushed in a different direction than someone who wants to play Baroque music as a main criterion or doom metal or folk music etc etc. If you want to play a great variety of music then you can't optimize for anything but must balance out the system so nothing is played miserably. In sports the decathlon athlete is not as good at any individual sport as dozens of specialists but can do a wide variety better than any specialist. Since you never stated what firm criteria you want from an audio system it is unclear what type of components or their specs would make sense. Also, typical specs don't correlate that well with listening preferences in many cases.

Posted by oxric on 07-07-2015

Blaukopf wrote:
Hi everybody, after reading RomytheCat's Macondo Setup I am very impressed ( phantastic music room ...) . Presently I have no working horns ( they are boxed), just questions.

First, Romy describes his horns as spherical. Later he names them tractrix. Are some of the profiles of the spherical wave profile ? Bruce Edgar wrote : You will be very disappointed in the bass response with a Tractrix horn. The bass response near the flare frequency cutoff is limited by the throat reactance, which peaks at the flare frequency . The horn is loaded for the most part by the throat resistance. Any reactance loading will reduce the output. In exponential and hyperbolic- exponential bass horns you can cancel out the throat reactance with the back chamber, but with a tractrix horn it is too short and the back chamber doesn't cancel out the throat reactance. Tractrix is great for mid bass and midrange but a terrible choice for bass. Where does the bass frequency start ?

My sims with hornresp show a good loading for a tractrix profile even at 80 Hz cutoff frequency - horn is huge of course. same for a spherical wave profile. How are they different soundwise ?

Can I believe the sim ? The throat radius measures 12 cm for a 15" driver and the mouth has a radius of 68 cm. Since the horn ist shorter ( than an exponential) , I would use it from a higher frequency - 110-120 Hz maybe. Next driver is a 2" DCM50 ( 500Hz up) and a 1" driver from 8000 Hz or a tweeter.

My dilemma : Exponential horns may load better but in a setup I prefer to have the same profile for all horns. Could you give some insight into this thorny question ? PS there were some excellent statements by JLH on push-pull TH ( am building one myself) but the images have unfortunately disappeared.

Thanks to all ! Marc

Hi Marc,

After a few years' hiatus, I am presently embarked on a project which is similar to yours and I guess that I have at some point or other in the past considered the same questions you are asking yourself presently.

Of course there are so many different ways to approach the whole project, and Steverino, Rowuk and Romy are probably suggesting that you should formulate clearer what your objectives are before you start to design your ideal acoustic system.

For myself, I think it is a good idea to do your own research and come up with a fairly well formed plan of action before asking too many explicit questions. Designing an acoustic system around horns can only be viewed as a personal journey of discovery, both discovery of existing and new lore, and especially one of self-discovery; so asking too many questions is, counter-intuitively, actually no great help in this quest.

In addition, you will find that very few people have all the answers to the questions that you might be tempted to ask. Very often, even experts can only give 'qualified' answers and often others simply do not have the relevant experience or the same priorities as you. I have learnt more by listening to some well-evolved systems than I could have ever managed from mere research and asking questions.

On the other hand, studying closely the evolution of Romy's system in the early years is, I would suggest, essential reading and might well contain most of the insights that you are currently seeking.

Good luck

Rakesh

Posted by Romy the Cat on 07-08-2015

I think to a great degree making playback is like go hunting. I am not a big hunting proponent and never did it but I just bring it for the sake of association. So, you might go hunt because you love bear’s stakes, need fox skin or appreciate duck’s liver. Or you go hunting become you love endlessly assemble and disassemble your raffle. In first case you need hunting. In second case you are a manic and you need psychologist, as so many people in audio.

Marc, I certainly do not attribute you to any of the classification above and if you feel that I do then please accept my apologies. The question you ask about 80hz Tratrix however did sound a bit like disassembling of AK-47 for a sake of disassembling. I know very little about the material the AK-47’s main spring is made and what the percentage of carbon it has. However, if you would like to know what raffle to take and how to use it in order to shot the fox in eye in order do not damage the precious fur then it might be an interesting discussion where you would be asking different questions.

Rakesh, is partially right. To get a qualified answers people shall have relevant experience, related interests or similar priorities. I made in the past my standing among audio people that I have no interest in audio development unless it serves my priorities. It might make me to appear like a jerk in the eyes of AK-47 collectors but I have the benefits that I do not socialize with those boring Morons. I wish any other person in audio put his or her own experience, interests and priorities ahead of own emblematic audio curiosity, in most cased artificially stimulated audio curiosity I need to note…

Again, sorry that you do not find your answers at this site but I might only assure that the question you ask have no answers at any recourse unless you begin to focus your questions to very individualistic and very egotistic interest. I do not think that I ever left without attention at this site those type of applications.

Posted by Blaukopf on 07-08-2015

Thank you for your replies. The concept is revolving im my head. The material is ready. As soon as time allows, I will go ahead.

In fact, many informations are readily available, I have been reading a lot in the past 2 years. Many decisions are a matter of taste.

Have a pleasant day and thanks again Marc

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