Horn questions below tuning frequency

[mackintire]

Just a quick question, Is the behavior of a folded horn (in this case the tuba THT) the same as a sealed box? As I understood it the THT is +3db compared to a sealed box with equal volume at 18hz (not accounting for room gain).

There appears to be a group over at AVS who are using the RS390RF in the THT specifically so they are make the unit more usable below the tuning frequency.

Many of these guys claim they can eq the units pretty flat to 15hz using this driver instead of the Dayton DVC normally recommended.

They also are claiming that the DVC runs out of headroom quicker when driven hard past the tuning point.

Does this sound reasonable or true to you?

[1Michael]

Not really. I am using the RS390HF in my THT and below 20Hz it drops off like a rock. I do not know how anyone is getting any real output below that except for maybe room gain. I don't consider the THT a Sub because of this drop off at 20. I much prefer my sonosub for movies but I prefer the THT for music. I don't know about the DVC because I have not used it...

[mackintire]

I dug farther into this topic last night. In "a room" the THT falls rapidly -10db by 17hz.

It seems some are boosting +8db at 18hz and placing a high pass at 15hz

This seems to achieve what appears as -3db just over 15hz. The only problem is the horn is magnifying the harmonics below the knee. So the debate is whether or not they are getting their desired result. The 5th harmonic is pretty big at that point and the third harmonic is not huge but its there non the less.

[---k---]

Yeah, the one I built with a DVC didn't have audible output below 20hz. I never had time to measure it, but I never heard it where it was supposed to be.

[A9X]

Just a quick question, Is the behavior of a folded horn (in this case the tuba THT) the same as a sealed box? As I understood it the THT is +3db compared to a sealed box with equal volume at 18hz (not accounting for room gain).

Below Fc the driver is going to behave the same as it would baffle mounted in a box the same volume as the rear chamber in the horn.