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Johan Dreyer wrote:

I call this the "pulsating room effect" Here there is a sensation of the air in the room actually pulsating to the sound.This is not boom but a sense of sheer energy being transmitted.Unlike music simply being played way too loud and being unpleasant this is simply an awareness of the power of a bass instrument and- more remarkable- the air in the recorded space being excited by the instruments(not only bass instruments).We have all heard how ,on a good mid horn , a brass instrument (especially saxophone or trumpet) can simply leave the horn and gigantically excite a room.Exactly like a live instrument next to you can startle by its sheer energy exciting a space( A Trombonist I know calls it "picking up the room").That is what happens on a basshorn too. Again I hear this effect in real life too. I think it is the horn matching the impedance of the drivers to the room

I know this effect but if it happen with bass horns then I do not call it “"pulsating room effect" but I rather call it “+1dB effect”. Some bass horns being placed in their rooms increase the density of pressure faster then the density of sound. It is bizarre concept of mine and no one understands it. Let try to explain it. Density and Pressure of tone has purpose and this purpose is described by artistic value of musical peace. With the expressive intentions of a given composition and the given interpretation there are always inner-reasons what density and what capacity of a note should be. In this case density, capacity and potency of a tone are almost the synonymous. However, not the Pressure. Pressure is an absentminded parameter that has relation to objective deviation of one volume over another but it has no relation to musical intentions. So, when you told that your have that “"pulsating room effect" across full MF range then I had no problem with it – it looks you are getting good sound out there. However, what you said that your have the same effect from basshorn I recognize it as a problem (your friend Trombonist with his "picking up the room" is very much irrelevant because he plays MF-HF instrument). The load a room with a dense, phase-perfect MF is wonderfully and we in a way experience it in “live” sound. (I said “in away” because in “live” sound we have also “space” and unlimited dynamics…., but it another subject) However, in “live” sound we never experience dense bass. Of course I’m talking about Sound of classical music, opera or any acoustic music not about the electrons surrogate).

You would argue, in fact you have said that you have heard this effect in real life too. However, who said the in real life we do not experience the problem with standing waves? The 30% of the sits in Boston symphony, partially near the walls and under the balconies have heavy standing waves problems and they crate that “pressurized bass” that I call “room clipping”. Take a string quartet and put it into a mid size rooms. Make then to play some rhythmic work, like Mozart or Hayden, and walk around them. You will see that at many locations cello will be not only louder but “pressurizing” with that “scuba-diver effect”. Sure it will be the “live” experience but will it be corrects? Not really. Those “clippings”, although they are “life” and “natural”, but they will take place NOT because the musical ideas but ONLY because the mechanical room-condition overriding the Sound. It is not good….

So, what from my point of view what be a duty of a properly performing lower basshorn? A basshorn should pressurize the room and create an environment that allows the MF to be “floated” ATOP of basshorn’s pressuranization. Thy basshorn’s out should act like a high density liquid that would permit the low density liquid (MF and HF) do not sink and to fly freely in a room. However, as soon the LF begin to inflict a listener with own ‘"pulsating room effect" then the value of LF should be minimized (at lest for the given listing position). John, try to reduce LF on your system. I know it is difficult to spend so much efforts and do not hear it. Furthermore you for a week or so will be experience some deficiency of LF. However, you will soon get use to and might dustcover that it does makes sense to keep it down, 0.5-1db below the moment when the "pulsating room effect" from basshorn will manifest itself. The only problem is that moving 6 feet away will change the entire setting for the  “+1dB effect”… 

Johan Dreyer wrote:

The delay thing is a problem.I hear delays higher up as drivers become audible as individual speakers instead of a whole sound.I do not hear this in bass.I think you may be right about the arrays.They may simply create a whole room full of sound that makes the above effect inaudible.On the other hand they quite clearly image left right and depth too so I do not know. But how to hear it? In setup I ran a sine wave at crossover freq through the system and watched the mic response(at listening position) on an oscilloscope figuring I should see 2 spikes in the reproduced sine.I saw none. This is probably nonsense but it made me feel better. I would expect to hear wide ranging instruments to "split in two"at the crossover, but I do not hear that either.Instruments not in one "space" i.e lower notes deep in the horn and the higher component out front? I have not heard that either.Never mind the old tap dance efffect of old WE horns.I think that only happens higher up.Bottom line :neither I nor my friends hear it so I stopped worrying about it. Maybe somebody can.Then I 'll worry again.

I still feel that you shell hear it. You presented a case of time misalignment - when the drivers heard as two deistically different sources. This hardly has to do with time misalignment and has to do with other reasons. The timing misalignment could not be heard this way. The Haas effect and many other things will mask it out. The way to hear the misalignment is to observe imagine and stoppage of decays (Whatever I say in this paragraph is about misalignment in LF, in the HF the misalignment is very simple to spot). What I might suggest you to do is borrowing a digital delay machine. It is dirt-cheep (under $100 and up to 32mSec by 1 mSec) and you can even buy one. Do not expect to get any quality form them but you not need any. All that you need is to delay MF and to observe if the presentation of music will change. I presume it should… at least of was my experience….

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