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A site visitor sent me emails saying:

“Johan Dreyer says he can hear no time delay with his bass horns…”

Well, first of all I disagree with it. The fact that Johan Dreyer can hear no time delay is not an indication that delay is not auditable. Johan might not know what specifically to listen or he says it as he has no options to time align his midbass. I would agree that one need midbass time aligned with fraction of inch precision but, even inch does not a lot of difference.  But a number of feet of differences is not a good idea. I might say a lot about the subject as I have a LOT of experience to deal with various aspects of time misalignment.  However, my objectives are not to criticize Johan’s view but rather to use the examples of his (and others) decisions and implementation to nail down what I would like to do with my own playback. My standing is that to use horns without time alignment is not good. I am not saying that if a meticulous time alignment was not implemented then the playback shall be dynamited. BUT, I feel that if the objectives of meticulous time alignment are preliminary goals during the period when a system is architected then why do not consider the alignment? Johan Dreyer has no ways to hear his playback in time-aligned mode, I still do…

Now about the diagram with different time alignment scenarios that Saturntube posted.

The top row is unquestionably the best way to time align. The alternative might be turning the horn way off – it is not a problem at all. A midbass horn does not have need to fire directly to a listening spot and to be on axis. The midbass horns might be even parallel to the walls shooting to the back and to be locate at arrival- aligned location.  In case of rectangular hors it is even a preferable way to do the things as it would allow to use lower low-pass filter and to remove more HF from the horn. The only exceptions from this I see in the Jessie-type horns. Jessie’s horns are full spherical midbass and made to be hanged in air above the MF in time-aligned position.  In my view it is absolutely perfect way to do the things but I am pretty sure that I will not have bolls to go for such a radical (but beautiful) solution.

The bottom line looks like the proper alignment but it is not, particularly the left image.  The alignment is not a pure geometry but the equalization of time arrival. In left bottom image has diaphragms in equidistant position but the wave needs to travel across the bend of the horn and this time need to be considered.  So, in the left bottom scenario the midbass horn needed to be moved closer to listener…

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