Ok, I blamed the tweeters and MF drivers now the turn of the MF horns. The Mid Frequency Horns (I’ll them “MFH” from now and on) are the stinky like pieces of horn installations, and if they are not done correct then they screw up anything big time The MHF hugely responsible for the crapy sound horns usual blamed for.
There are two most critical zones of sound reproduction that hugely affect out perception of reproduced sound: upper bass and upper midrange. The MFH cover upper midrange and come very close to upper bass. Therefore “how” they cover it is very accentual.
Depth of the MHF regulates the EQ of LF and attenuation of HF and the depth (as a function of a cut-off frequency projected to size of the throat, along with few other parameters) should be properly match with the sonic idiosyncrasy of a chosen driver and the way how the driver/MFH tandem is used in context of the entire installation. The problem in here is that it is very difficult to try the things. After something is done at a certain level of perfection a result should be evaluated and if you need to change something then you have to redo the entire. It is very rare that it possible to extrapolate the result and it is not always perfectly predicable. I spent 3 years of listing different MF drivers in order to tech myself how to interpret the sound of drivers until I reached a point that I learned what to listen in driver while I listen a driver and until I was able roughly predict how a driver will sound in a system by listening a bare compression driver that just sits on a floor, without a horn. However, I never was able to say with more or less degree probability what would happen with different horns.
Let star to talk about the profiles. There are few available parabolic, tractrix, conical, exponential, hyperbolic, combined, forced and few others. All of them produced different efficiency boost and different distortions patter. I know little about distortions or at least I know little how to interpret the contribution of horn distortions to musicality. Different drivers act in different horn’s profile differently and each profile has own “twist”. Perhaps there is a bit of theory behind all of this but I do not know about it. I am just a user who specializes of using playback and I do not build theories around playback but just recognize and use the patterns. Among the horns what I head so far I find that a tractrix MFH, of a half crossover point and +6dB efficiency gain, cut above the primary resonance frequency was something that delivers more predictable and stable result. Tractrix (I, being me, call it tatrix sometimes) is shorter and it produces less “intricate sound” (VERY loaded statement). The Tractrix sound is very easy to handle and well integrateable…. Did I mention that I was talking about the round tatrix horns?
Here we go… the Pandora Box for the MFH about to be opened…
It never came to me why the hell such huge amounts of completely idiotic rectangular MHF were produced. All of those rectangular MFH – big, large, regardless of material, level of implementation, brand or price tag – are garbage and this rectangular shape is a primary reason why horns sound like *** most of the time (I would like to point out that I am taking now about the mid-rage horns only). The rectangular MFH screw up imaging (big time), highly complicate or make impossible a proper integrations, very prone to severe off-axis complications, practically unusable in nearfield, have peculiar roughness and aggressiveness changing with off-axis and have many other obvious and hidden problems. A minor exception might be multi-sell horn, used at very large distance, but the multi-sells are totally different story. Anyhow, the rectangular horns (including the 2-3-4 sell horns) are just a pile of huge horno-foolishness that discredit whole idea or horn loading. Wean I say the MFH is mean explicitly round horns but not all that rectangular junk that the professional, semi-professional and move-oriented companies managed to produce in their past.
The material for the MFH. The material of the MFH is important. However, the important thing is what it does but not what it is. It is quite possible that a specific none-perfect driver, used in a certain way, in context of a specific MFH none-perfect material and specific manufacturing methods might perform quite well. It does not necessarily make the diver material universally good or bad. I experimented with a number of horns and concluded that the best predictably-stable result is possible to get out of a situation when a driver does not communicate with horn -then the drivers’ quality become prominent. However, having personal tangency to high-attitude drivers I would like to see MFH is as “slow” as possible. Paper-made MFH, if they are properly done and heavy enough are great. The lead horns are spectacular! Wooden horns are, if the made form very damped wood are very good and very ease to deal with. Different brands of plastic might be used for MFH and if they done expensive and properly finished then they might be quite good. Ironically most of the commercial horns are made form a light metal (aluminum and so on) and they are very bad. To make those Altec, JBL, Vitavox, WE and so on horn do not ring you would need to dump a Chernobyl Sarcophagus on then to tame them down. Most of the light metal they will sound too obnoxious, not to mention the all of them are rectangular corny-sounding junk. (Actually I use “corny” in here literally :-)
Another important point that coastally neglected and the severely degrade the horn results is the fact that any HF horns and MFH (mouths) should be hanged in open air. Yes, they do recognize boundaries near thier months. If you see a horn that sits inside of a baffle and its month is continuation of any close focal parallel surface then you do not hear the horn but the dirt the bouncing form the baffle at 180 degree. The fantasies that people love to spread about the horns suggesting that MFH has narrow radiations and less sensitively to boundaries are completely groundless. Quite opposite: a properly built horn in context of a properly built installation should be superbly sensitive to anything in the room (The horns are velocity condoled system and therefore with horns you are deep into phase domain and this fact enforces a bunch of special precautions that are not so critical with mass controlled direct radiators. I will cover it further on in “THE PROBLEMS WITH HORNS: TIMING DOMAIN”)
One more common absurdity that widely popular but work very bad for Sound: the attempt of people to make “cool looking” MFH. I understand that you spend more time with your MFH then you do with a breast of your women however the “cool” and shiny MFH screw Sound. The well-polished, glossy horns look great on the pictures and marketing catalogs but they sound “strange”. With complex musical crescendos (and particular at upper mid range) they weep and sound sort of “slips” across the horn. In addition, the well-polished MFH are way more susceptible to let Sound to inherent the signature of the MHF material: more granularity of the horn surface = less influence of the material to the horn. It you take an ultra-light plastic glossy MFH and paint it with a textured paint then it will substantially minimized the coloration of the thin plastic. The best surface for a horn an ultra-soft wood with a lot of wooden hair sticking right into the horn pathway. However, this type of the finishing might be too dumped for the mellow drivers (like Altec for instance). The most optimum all-around is to have a MHF made according to what I call LS+H+St scenario. It means the MFH should have a LOT of soft body and a lot of soft mass with superb damping ability (LS-layer). Then, it comes the H-layers: hard and ultra thin surface crisp. Eventually the St-layer should finish the MFH. The “St” comes form “structured” or some kind of finishing-substitute for the “hair” that I mentioned above. The idea is that Sound should not use horn like absolute bouncing surface but should perceive it in a way in which a good Jewish bagel made: crispy but slightly abrasive outside, however chewy and tender inside.
I sincerely believe that a biggest problem with the MFH is a shortage of people who actually manufacture them. It is NOT complex to make a good horn form whatever material. What is complicated is to make a horn exactly how you need it for a given driver and a given application. Most of the horn-makers make the generic horns and their horns produce too generic result. In order to push the envelop of the horn’s reproduction you should really make your “perfect horn” for your own perfect driver and your unique situation in which you intend to use it. Unfortunately to find a manufacturing house that will listen you is big rarity and mostly it forces people to compromise the means and consequentially to compromise the result. Mostly the manufacturing houses do whatever is comfortable for them to produce and frankly speaking they even there do quite crapy job. I’ve seen a lot of high-paranoia and high-snobbism horns that were done very purely or even very stupidly. I believe that MFH-makers should not sell the generic horns as it completely screw up the idea and is mostly it is the reason why most horn installations sound “as is” instead of how they should.
The next post will combine subject of upper bass drivers and upper bass horns. It will be “THE PROBLEMS WITH HORNS: UPPER BASS”
Please be advised that I recognize bass as something that should be reproduced by 2-3 channels and each channel should have own requirement and sometime even quite distinctive means of reproduction. I DO NOT BELIEVE in the lower bass reproduction by horn loading and there are many reasons why. Therefore. I will not cover in this thread the horn repudiation of lower bass.
Romy the Cat
"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche