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In the linked there above “Barn Conversion - James' Project” I have expressed my attitude toward low frequency bass. I certainly not “against” bass horn it but have “concerns”. The “open bottom” concept that I invented for myself is always make me to ask a question: how a badly implemented bass horn (and they are unfortunately are always compromised) would perform against the properly implemented infinite baffle (oversized sealed) enclosure.

I certainly would not argue with Johan experiences of building the bass horn, I did not nave them, but I would like for the sake of bass horn education to point out some moment that I found “slippery.”

Johan Dreyer wrote:

… Choose drivers and design the horn for them. Here Altec 515-16G were chosen. Remember you must reach the low midrange so heavy "sub" drivers will not work. Use multiple drivers in parallel-5 per channel in this case. This will keep your horn shorter (3m here) yet maintain full horn loading to 21Hz. Again minimise time delays. Do not use an anterior compression chamber. It will increase efficiency but also distortion and the thin paper cones in these drivers do not like it. With 5 drivers you are already at 110db/W with no anterior chamber. Design a rear chamber for the drivers using reactance annulling.That way youl'll get aflat reponse almost right to your horn cutt-off. Buy an RTA and mic. Use McBean's horn response program to evaluate your design. It came uncannily close to the final measured result …

The link to Johan Dreyer’s installation: http://cgi.audioasylum.com/systems/8608.html

The Altec 515-16G are 37Hz primary air resonance according to the paper and much higher in the reality. I have 4 of 515-16G, 2 brand ne never use and 2 used. My new drivers had 48Hz primary air resonance, I did not measure the used. So, how the 5 Altec 515 drivers can be loaded into a horn and to get 21Hz I have no idea. Even if one would do not use a back chamber and let them to run with open back then I feel a horn can hardly EQ them lower then ~50Hz. Anechoicly. I have no reasons do not believe to Johan that his horn does 21Hz but it is all room gains and not “maintaining the full horn loading”. BTW, nothing wrong with use of room gain, it is very good in fact but let to be accurate to understand what we deal with. Then, the 5 of 515-16G drivers is a very large mouth. I understand that it keep the horn shorted but it also very much reduces the EQ of the horn, making the 515 drivers to ask at the bottom as direct radiators with excessive exertion.

So, looking at all slippery moments I am asking myself: how the approach with above-mentioned Johan‘s horns armed with 515G drivers would compete with a pair or line-arrays in sealed 40-50 cu feet armed with 515-B/E/LFE drivers?

I have no answer to this question but architecturally I prefer the sealed solution direction. I can see 7 reasons why:

1)  “Open Bottom” concept is preserved
2)   Ability to move the LF sources and position it “strategically”
3)   No time-delay problems
4)   Encouraging to use a dedicated upper bass channels
5)   Cylindrical wave its all benefits.
6)   Since it is an “Open Bottom” solution the “open EQ” is available
7)   Ability to mitigate amount if drivers used.

It is what I have atop on my mind. Using horn I defiantly would like to talk about the good bass horns.  Johan Dreyer did not just talk but actually built a pair. Still, if I have a room for the project that I would think hard if I go for bass horns or for the sealed arrays, perhaps with 18 drivers. I, looking at my “7 reasons” do have a preference to sealed boxes. I do not believe in accuracy of bass horns, particularly in context of system integration.

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