Dear Bill,
This reads to me like you feel it is an unambiguously good idea to cross the horn to the cones at a lower frequency. Why would this be?
Isn't this subjective depending upon the preferences of the listener?
I am reminded of the interesting difference in competing designs of Gary Koh who crosses his ribbon drivers over to his woofer towers at 100Hz versus Flemming Rasmussen who crossed his ribbon drivers over to his woofer towers at 200Hz. This is a fascinating difference of opinion because both speaker systems used to use the exact same ribbon driver. (As a layman and merely a consumer, I think I like the idea of the cones coming in at a higher frequency so you get some dynamic driver oomph a little higher up.)
Each designer has rational reasons for his design preference. I believe there is no objectively correct answer.
As the designer of your loudspeaker system what is your thinking and philosophy here?
Hi Ron,
All great points! Apologies if I am sounding resolutely positive that there is only upside - clearly all such decisions are matter of taste. I have tried a lower crossover point with a plastic horn as a prototype so have exposure to the potential rather than a big gamble.
My view on this conundrum is as follows.
> The driver of the upper horn very much dictates my agenda / plans. The AER driver I use has very solid output in free air down to 90-100hz. This lends itself the *option* of deciding to cross lower if I were to choose to. Clearly this is somewhat an unusual situation for 2 reasons:
1. There aren’t many compression drivers that can get anywhere near 100hz never mind 250hz
2. Horns are bandwidth limited devices meaning that their loading occurs within a defined frequency response based on the chosen mathematical form and size. One can’t normally use a horn over such a bandwidth instead more channels are required. This is very much true of compression drivers where one can’t (usually) cover from 100-20k with one horn. This is why you see the multiple horn channels you see on a big Cessaro for example. The only anomaly is the very large snail horns (WE style) that do indeed get you down to 100hz but they are augmented with a tweeter horn too.
So here we form somewhat of a compromise in going for simplicity and integration of 2 way but accepting we need to cheat a bit. The AER fortunately has extraordinary high frequency output and doesn’t apply that energy in the normal way one would expect with a whizzer cone.
Alternative 2 way options would include a mid bass horn with venting ala Altec operating to circa 500 before transferring to horn or 2 above depending on driver or preference. Obviously many other hybrid options exist too.
So we have talked about the “how” but what about the “why” - well the quality of the output in the AER + horn is so extraordinary for my taste that taking advantage of that quality of sound even lower and to the point where bass becomes non directional is a very useful goal to me. Our ability to determine directionality of bass becomes absent at around 120hz for some people and for most around 100hz. Because of this, each speaker is theoretically becoming more of a point source which I personally think advantageous based on my tests for imaging purposes. In terms of qualitative content, the tonal qualities of voice gets richer and the harmonic content of strings / brass develop a harmonic richness. You might expect that to be opposite - that all those 15 inchers would do that but I didn’t find that.
So hope this sheds light on rationale and intention.
Best wishes