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Jessie, at the home page, in the left, within the GoodSoundClub Section there is the “Announcements” item of menu, which will bring you to the thread with the instruction how to upload the images to the site.

Regarding the issues that you are trying to address. You are absolutely right and the throat’s side thickness is a commonly avoided acknowledgment subject. Ironically the throat’s side thickness is not only silent problem with the upper bass horn but also with compression drives. I have seen many of then that have internally a perpendicular surfaces that I personally believe shouldn’t be there. So, what to do with that Red Area?

I do not know. It is possible to make it as a contra-horn introducing a little bell in the opposite direction and making the deriver act as almost a compression driver. However it would essentially minimize the effective diameter of the cone. Sound derives from the perimeter of the driver diaphragm and by masking the outskirt of the driver you will change the driver characteristic. In which direction would it be? I do not think anyone knows… I do not think that there is anyone out there who was able to assess how different drivers with the different diaphragm profile, loaded into the different throat’s holes would sound. theoretically, purely theoretically the slightly larger  driver loaded into a throat create unavoidable front chamber. This front chamber acts as a first order low pass filter and as a resonator chamber with own completely unpredictable sonic qualities. If we add to the mix the reflections from the Red Area then we have a completely erratic behavior. The good part that all of it has to do only for higher frequencies and in your case when the horn will not be doing a lot of HF it might be irrelevant.

If you try to make the horn with 100Hz then the Fs of that driver should be around 1/3 octave below. For such a driver 1000Hz is handle-able but it might already that the driver might have a cone too heavy for 1000Hz. You have to listen it and see how it does. To make the Red Area as right and accusatorily abrasive as probably would be a good idea. Still it would have purely intellectual-logical purpose as I down that the stricture of this surface will be auditable at 500Hz. I ma very much be wrong and I look forward to learn form someone who has data regarding the subject.

Rgs,
Romy the Cat

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