What is a tapped horn subwoofer? - diyAudio
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Old 11th May 2012, 09:06 AM   #1
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Default What is a tapped horn subwoofer?

Can someone give me a simple definition of what a tapped horn sub is?

I did a search for examples of them so I'm not looking for links to builds that dont talk about the simple definition of what one is.
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Old 11th May 2012, 11:04 AM   #2
NEO Dan is offline NEO Dan  United States
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A broad generalization would be that the tapped horn is a configuration where the driver radiates energy into the horns throat, a horn which expands along it's length, the tap is where the other side of the same driver's cone is radiating into a portion of the horn typically near the mouth/exit.
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Old 11th May 2012, 11:17 AM   #3
AndrewT is offline AndrewT  Scotland
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A sub-bass or sub-woofer is a speaker designed to deliver output below audible bass frequencies.

By definition these frequencies can be felt, but not heard.

Low bass speakers are generally used to deliver output above the Audible lower frequency limit.

Many commentators get sub & low completely mixed up and interchange them.
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Old 11th May 2012, 03:41 PM   #4
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Quote:
Originally Posted by AndrewT View Post
A sub-bass or sub-woofer is a speaker designed to deliver output below audible bass frequencies.

By definition these frequencies can be felt, but not heard.

Low bass speakers are generally used to deliver output above the Audible lower frequency limit.

Many commentators get sub & low completely mixed up and interchange them.
Low frequencies can be heard, as well as felt, as can easily be verified with a set of headphones.

Less than 80 dB SPL is required for average ears to hear 20 Hz.
At levels approaching 140 dB, low frequencies can be heard through the ears down to a few Hz.

"Sub" means below. A sub-woofer, by definition, is a woofer that is added to provide response below the woofer.
A "woofer" may have response only extending to 100 Hz or so for a small bookshelf speaker, or response reaching flat to 40 Hz or below in many designs.

For the OP, to expand on Neo Dan's explanation of the TH, a TH is a resonant air column effectively using both sides of the speaker cone, which can result in an output around 6 dB more than the same speaker (of the proper parameters) used in a bass reflex cabinet.

Unlike a "normal" horn, the so called TH does not require a large mouth exit to have flat response in it's pass band.

Interference between the front and rear speaker radiation limit TH to a bit over two octave range of reasonably flat response, generally limiting them to "sub woofer" rather than "woofer" usage.

Art Welter

Last edited by weltersys; 11th May 2012 at 03:48 PM.
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Old 11th May 2012, 07:53 PM   #5
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Inaudible lows are not really sub-sonic, they're infra-sonic.
Subwoofers are not sub-sonic, even using the wrong word.
Sub-woofers are more literally sub- to the woofers.

Tapped horns...well...in accessible terms I'll freely invent and use wrong...the general idea starts with a nearly typical bass horn, where the driver's 'primary" output "works" into a small space with a small opening which acts as an acoustical low-pass filter and defines the beginning of the horn throat. As the horn continues expanding along its path, it folds perhaps once or more times so that approx. the 1/2 wavelength distance along the horn the horrn wall is again adjacent to the driver. At that point the opposite-side "secondary" reverse-phase wave of the driver is now IN-phase with the "primary" output which has been delayed by a half-wavelength. In a conventional bass horn, the output of one side of the driver powers the horn and the opposite side of the driver is absorbed in a closed box. In a tapped horn, useful output is derived from both sides of the driver and added in-phase. Somewhat like the port in a bass-reflex reverses phase of the secondaray back-wave secondary output so that it adds supportively, in a TH the horn distance to the 'tap' reverses the phase of the front-wave primary output so the 'tap' adds supportively. Makes intuitive sense, if you consider the delay and phase-change as the sound travels along the horn. I have not thought about exactly how much extra output you get from the technique, but it's significant.

How you introduce the tap, shape, exactly where, how many drivers, etc. lets you use the extra "free" energy of the secondary backwave to advantages that can be traded off for bandwidth or extension rather than just efficiency, much like tuning a bass-reflex for particular objectives.

Does this help at all?
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Old 12th May 2012, 11:17 AM   #6
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How do they compare in size to a typical non-extended bass shelf vented alignment?
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Old 12th May 2012, 12:12 PM   #7
djk is offline djk
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Size is a cube function.

Dropping the response one octave and keeping the efficiency the same requires a box 8x larger.

Dropping the efficiency by 3dB will allow you to make the box half sized.
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Old 12th May 2012, 12:22 PM   #8
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The TH is very well presented at diy level here :-

William Cowan's Homepage

suranjan
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Old 12th May 2012, 03:58 PM   #9
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cyclecamper's explanation is about as good as I've ever seen, emphasizing the wavelength concept over the benefits, if any, of the little horn. He forgot to add that one of the few places that shows appreciable "respect" for this design in this very forum and critics here get messages from moderators if their skeptical posts threaten to arouse disharmony.

OK, at ONE frequency there is some boost, at another frequency there is a cut, and of course, everything in-between. Yes, it kind of resembles bass-reflex in some ways, but then some folks don't like to add resonances to their hifi.

There is much hand-tuning and art in choosing sizes and drivers and so on. Very easy to screw up and get zilch, I've heard. On the other hand, some folks are really impressed and that includes settings requiring loud or low-frequency output... albeit not necessarily quality output.

I don't think I 've ever heard a TH (or a Geddes). Pity. Any in Toronto?

Ben
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Old 12th May 2012, 03:59 PM   #10
tb46 is offline tb46  United States
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Hi,

A starting link on tapped horns @ diyaudio:

Evolution of the Tapped Horn

and another one:

Tapped Horn for Dummies

a good example:

Dual 8" tapped horn = TH-SPUD

and the "monster" thread:

Collaborative Tapped horn project

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