The Smallest Tapped Horn

[GM]

Originally posted by Patrick Bateman
After what I learned on my Tapped Horn for Dummies thread, I realized that the best driver for a 50hz horn would have an FS in the range of 60-100hz.

Oh really?! Apparently you've forgotten about the info I gave you on BP design awhile back on another thread. FWIW, this example I reposted recently has a ~113 Hz Fs driver: http://www.diyaudio.com/forums/attac...amp=1220547130

So scaling it back to ~50 Hz puts it at ~83 Hz for a similar gain BW...........

GM

[Patrick Bateman]

Could you elaborate on this? The pic you posted of a driver with a FS of 113hz has an F3 of 75hz. That correlates with my recommendation - that a tapped horn with an F3 of 50hz would work well with a woofer that has an FS of 60-100hz.

I'm not trying to argue with you, it's just that your post disagrees with mine, but the pic you posted didn't!

The original poster should clarify the terminology also. When he says "50hz tapped horn", is he referencing the F3 of the enclosure, or the length? The length of a tapped horn is a bit deceptive, since there are multiple entry points.

[GM]

No, my post agrees with you WRT driver Fs choice. My 'surprise' is that as many times as Tom, me and others have posted about the need for a driver with an Fs > FLh in a BLH, TH (not to mention some FLH) alignments that it's just now 'sinking in', especially since I ~'spelled it out' on one of your Unity clone threads IIRC and you apparently had 'gotten it' at the time.

WRT "The length of a tapped horn is a bit deceptive, since there are multiple entry points." It's no different than any other horn, so there's nothing deceptive about it nor does 'multiple entry points' have any affect on calculating its length.

GM

[FlipC]

The driver I was referring to is something I have laying around.
DVC385-88. This is more of trying to learn and understand
the math. The driver in question is a poor choice for most things TBH.
And my apologies on the math. You are right as the length was just over 6 feet and not 13. Not sure where I got that from.

And the 50 Hz would be the length.
BW would be 50-150 Hz.

So is it a general rule that the driver should
have an FS right above the low frequency you are aiming for?

[Patrick Bateman]

Originally posted by FlipC
The driver I was referring to is something I have laying around.
DVC385-88. This is more of trying to learn and understand
the math. The driver in question is a poor choice for most things TBH.
And my apologies on the math. You are right as the length was just over 6 feet and not 13. Not sure where I got that from.

And the 50 Hz would be the length.
BW would be 50-150 Hz.

So is it a general rule that the driver should
have an FS right above the low frequency you are aiming for?

If you're gunning for an F3 I'd recommend a driver with an FS in the neighborhood of 60-100hz.

Any good tapped horn is going to be *significantly* larger than a sealed box, as much as 4-8 times bigger.

Your driver would work nicely in a sealed box that's the size you mentioned. Even making a vented box that small would be undersized. While it's possible to juggle the parameters on a tapped horn so that it would fit in such a small footprint, you'd wind up with a difficult to build box that wouldn't offer any benefits over a simple bandpass box, IMHO.

Your driver would work nicely in a 15hz tapped horn, not a 50hz tapped horn. Maybe even a 10hz tapped horn.

[FlipC]

So how do you figure out Rms and Mmd ?

And man. 10-15Hz...
I guess I could make one within a full size couch!

[Patrick Bateman]

I have a pair of TC Sounds fifteens here, with lots of excursion. I was toying with the idea of a sub bass tapped horn. In order to make it big enough, it would be around 1,200liters!

My idea was to build a raised floor on one part of the living room, put the couch and the rug on top of it, and a couple of steps. So you would be sitting on the subs when you're on the couch.

[FlipC]

Your getting into the crazy territory there.
Like the Italian guy with the basement that is a horn loaded subwoofer.

[GM]

Originally posted by FlipC

DVC385-88.

And the 50 Hz would be the length.
BW would be 50-150 Hz.

So is it a general rule that the driver should
have an FS right above the low frequency you are aiming for?

OK, thanks. These are different specs from both the manufacturer's and DUMAX ones, so are these measured?

Regardless, this is a true sub driver, so wants a ~9.8 - 13.29 Hz low corner and its specs being what they are, it doesn't want to go much over 100 Hz, so even if it was suitable for 50 Hz, it's not ideal for at least 150 Hz. Combined with its relatively high Vas, we're looking at ~600 - 1200 L for this thing to 'strut its stuff', making it ideal for a built-in.

Note that like any horn it won't load all the way down to 50 Hz if it's only 50 Hz long, with a half octave below being a typical length for conic and one octave for expo, but you can start there and use HR's slider optimizer to find the right length, etc., for the intended driver's specs.

Dayton DVC385-86 (295-190) 9.8-96.41 Hz conic TH, 1.0 W corner loaded:

GM

[GM]

Originally posted by FlipC
So how do you figure out Rms and Mmd ?

??? HR calcs them when you load the driver's T/S specs.

GM