For my experience :OK, it happened again. I recently listened to some large horn speakers. I have periodically done this over many years at various hifi shows. I came away again with the same thoughts. I just don't get them.
Firstly they were clearly highly directional. Unless I was right bang in the firing line on axis they had no high frequencies.
Secondly, mid range seemed over emphasised with a "cuppy" effect. Exactly like the sound you get if you cup your hands around your mouth.
Lastly they were no more dynamic than any other large speaker.
All the same characteristics I have heard previously.
Is it me? Am I biased? Heard the wrong horns? Some rave about horns but it's lost on me.
What are others experiences?
- Opening coverage, a constant one, should be adapted to listening distance, for our room/saloon or even dedicated HC it's 90/80° horizontal and can be arround 60° vertically (our rooms are wider than they are high, and our ears are positioned horizontally, which also defines the plane to which we are most sensitive), and the horn should be EQ’d in the DSP in near field (40/60 cm), to take into account all horn behavior in the baffle but not the room interaction. EQ for room, at listening position, should be done only in the modal field (below 250 Hz more or less in a regular sized room).
- The horn must be CD (Constant Directivity) on the horizontal plane at least, without mid-range narrowing or mid-range beaming to have a 50/50 proportion between direct field and reverberated field that rebounds on walls and goes back in your ears thanks to side walls even if you are in front of the speakers.
- If you are sit down you can use a modern biradial, biradial loses their vertical directivity sooner than a horn CD on both axes, it's different and almost impossible to indicate who is better, but if you listen both sit and stand up, a horn CD on both axes is advised.
Note that the AudioHorn bi-rad has a unusual shape in order to address mid-range narrowing
- Fast opening CD horns (so not the X-Shape for ex) have difficulty to load due to fast opening, regular OS horn are in this case, it's why they are often very big to compensate it but it creates another problem in more that price, the directivity match: at crossover, directivity of horn and woofer should be close or what you describe will happen:
- the "cuppy" effect you describe can be a woofer that opens too wide comparatively to horn, can happen if the horn is not CD/has accident too
- At the reverse, some woofers have a reputation of "empty midrange" just because some peoples cut them too high so the woofer is too narrowing compared to the solution producing HF, at crossover region.
- Be realistic, the compression driver breakup (often after 10 kHz) will push the driver out of plane wave radiation, and temporal behavior will happen. At this moment, the driver more or less stops following the horn profile and it creates accidents. It's not due to the horn, and it's not audible (too high, no "real-life signal" at this frequency, and our ears don’t really catch it). So, being CD is the way, but not ultra high, exciting the driver breakup too much is unnecessary, and moreover, what is present off-axis is no longer present on-axis (the on-axis curve will drop in HF even faster)
It's like the first law of thermodynamics : "Energy cannot be created or destroyed, only transformed from one form to another".
A horn is all about energy distribution, sending it only where it’s needed and avoid wasting or losing it in another form.
The width of the baffle is important too, a baffle is a 180° horn that ends abruptly, the baffle should not be too large (the driver + wood and some cm but no more) otherwise the woofer wavefront will try to follow the baffle and radiate at 180° when it is already narrowing because of its end of pistonic effect.
The best is a not too wide baffle, no need to round-over for the woofer, but for the horn it is mandatory, it can look strange but a woofer midrange narrowing well placed at crossover will help in most cases, if the baffle is too wide the woofer off axis response begin to "shake" on polar plot as there is: End of pistonic effect => 180° baffle => mid narrowing too far so not well placed in frequency. That looks strange but a good baffle is a not too large one: https://audiohorn.net/mid-range-bea...nge-narrowing-as-a-directivity-control-device there is a paragraph about it in this article.
This one respect it, it's an X-Shape X25 with "official" round over with a 8" (I would prefer a WO24P or WO24TX here ^^, it's a SB23NBAC) with a tiny round over, we can see the roundover transition :

Note: Thanks to Back Electromotive Force, it's possible to "push" distortion generated by the woofer breakup higher and allow a perfect midrange reproduction for a relatively big woofer. In practice, it's usually done with a air coil inductor in series to the woofer that will increase inductance in the breakup region and "fix" the VC movement when the membrane breakup moves and creates unwanted voice coil motion. It works only in active speakers, as the air coil inductor should not be bypassed by a parallel component.
In the case of air coil inductor use, it's calculated to replace DSP EQ at the same time, so the SPL remains exactly the same across the whole bandwidth, but distortion is now much lower in the top part of the woofer range.
18Sound AIC (Active Impedance Control) use another approach for the same goal: A fixed secondary coil is mounted on the pole piece, generating a controlled magnetic field that compensates for the nonlinear inductive effects of the primary voice coil. This reduces distortion caused by the variable inductance of the moving coil. In the value chain, the AIC system intervenes earlier, compensating for nonlinear inductive effects at a stage before they affect the overall performance, thereby reducing distortion in the moving coil at an earlier point in the signal path.
It's not horn-related, but it’s important for horn-usage speakers. In particular for the midrange reproduction.
Last edited: