GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Problems with horns: upper bass

Post Subject: About the elliptical mouth upperbass horns.Posted by Romy the Cat on: 8/1/2009

Dominik, Jessie is right - it is irrelevant the precession of your profile if you horn does not go to high into HF. The LF gain of upperbass horn happens in the first half of horn anyhow. I do not insists that I am right but I have a hypothesis that what they “call horn gain” by slow opening profiles happens in fact by lucky creation and amplification by the horn bell the miniature standing waves in the beginning of horns. The slow opening profiles have very slow rate of opening in beginning – the channel is always parallel and I think it creates some minute resonances that become the “extra bass”. This BTW might explain why this extra bass from hyperbolic horn always is very muddy and boomy and need VERY accurate control in order do not be so..

Jessie is partially right that it is not always good idea to get more bass from midbass horn but it is in case if you have more complimentary channels the can hams it. If you have just one upperbass horn and MF channel then you of course would like to get from your horn as much as you can but if go more then 35”-37” upperbass then you might have difficulty to locate it under you MF driver and to keep a nearfield capacity.

This brings the oval profile into the picture, or as I call it elliptical mouth horns. I thought about it before and I do not see a lot of difference. From one perspective you can get with ellipse less imaging problems then you would have with rectangular horn (in the lower MF range of you upperbass horn). You would also would be able to locate your MF driver above the short side of elliptical mouth, prolonging the longer side of ellipse and making the mouth size to have as larger size. Sound good, isn’t it?

However, in reality if you make larger surface of mouth then you need to make the length of the horn larger as well. So, let compare the round 36” horn which would be approximately 36” long (I do not want to circulate it now but I did it in past). Your 400Hz horn in time aligned position will be 18” behind the 36” horn’s mouth, which is manageable in case the upper edge of the upperbass and the lover edge of MF are on the same plane. Now pretend that we made the elliptical mouth with cut off for 15Hz-20Hz lower and our elliptical is let say 36” by 50”. It looks like nothing changed and we found a “free” 20Hz but the horn of the same opening profile would be approximately 10”-15” longer. This makes the very same MF driver to sit 30” behind the upperbass horn’s mouth of the same height. This is a LOT of distance and you will have in this configuration a LOT of MF will bounce from the back of the upperbass horn. So, I feel that for upperbass horn the 32”-38” is a right size/height and it server a good support for MF sections.

The ellipse midbass would be more interesting as would allow shaping the horn accordingly. The ellipse MF is more controversial as the MF horns are small anyhow. I see a benefit for ellipse upperbass if it sits above the MF but then what would be in such case below the MF? The direct radiator bass channel? Possible but I feel it is too valuable location to give it up to bass section, not to mention that you what to position your bass section where it needs to be but not where your MF channel happened to be.

Rgs, Romy

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