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In the Forum: Horn-Loaded Speakers
In the Thread: Tractrix Bass horn vs Spherical Wave Horn - Bass loading
Post Subject: The quest for insightPosted by oxric on: 7/7/2015
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 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


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