What Is A Tapped Horn Subwoofer?

Norvan Martin
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Subwoofers are designed to reproduce and deliver output at bass frequencies. In this article, we focus on the tapped horn subwoofer designs.

A tapped horn subwoofer is a type of speaker configuration where the driver radiates energy into the horn’s throat, which expands along its length. The ‘tap’ is where the other side of the driver’s cone radiates into a portion of the horn, typically near the mouth/exit. This setup allows the speaker to use both sides of the cone, potentially increasing output.

To explain another way:

A tapped horn subwoofer uses bass radiation from both the front and rear of the driver and combines them at the mouth. This results in greater efficiency, smaller enclosure size, and deeper extension (the distance a woofer moves from rest). The acoustic load on the driver also leads to a lower excursion which then leads to increased maximum SPL and lower distortion

The advantage of using a tapped hirn subwoofer is that tapped horns are good when you are working on a budget and money for drivers and amps is limited. They are also good choices when you need maximum output loudness.

The disadvantage of tapped horn subwoofers is that there is a requirement for DSP filtering to prevent overload at the lower frequencies and remove high Q peaks just outside the pass band or risk a flat response.

What Is A Tapped Horn Subwoofer?

As the name suggests, a tapped horn subwoofer is a subwoofer designed in a way such that the radiations from the rear and front drivers combine, or in a way, are tapped at the mouth of the subwoofer.

The idea has only been brought to light by Tom Danley, though remains very obscure.

Benefits of Tapped Horn Subwoofers

Please see below the list of the advantages of tapped horn subwoofers:

  1. Greater efficiency
  2. Deeper extension
  3. Smaller enclosures
  4. Lower excursion (the distance a woofer moves from rest)
  5. Increased maximum SPL
  6. Lower distortion

How Does A Tapped Horn Subwoofer Work?

A tapped horn subwoofer is a unique loudspeaker that merges features of traditional horn-loaded and bass reflex systems to create powerful sound and low-end tones. Here’s what you need to know:

  1. Basic Design: In this subwoofer, the speaker cone sits not at the very start but partway down the length of a horn. We call this spot the “tap” point.
  2. Use of Both Sides of the Driver: Differing from usual horn designs that use just one side, a tapped horn uses the front and back sides of the cone. The front plays out into the horn at the tap point, while the back plays into another part of the horn.
  3. Path Length and Phase Alignment: The design aims to make sounds from both cone sides work together well. By making the paths for the sound waves equal in length, they join up correctly at the horn’s end, which bumps up the sound.
  4. Efficiency and Low-Frequency Extension: Tapped horn subwoofers stand out because they’re super efficient and churn out very deep sounds. They have smaller boxes than usual horn subwoofers but keep that famous efficiency and ability to hit those low notes.
  5. Frequency Response Characteristics: You can tweak a tapped horn’s sound by adjusting the horn’s shape and length, plus where you place the tap. Designers play with these parts to make the subwoofer hit the best notes for its job.
  6. Acoustic Loading: The horn boosts the speaker driver, meaning it doesn’t have to move as much to pump out a given level of sound. This helps make the most of its power.
  7. Complex Design Considerations: Designing a tapped horn subwoofer can be complex. It requires careful consideration of the horn’s geometry, the driver’s characteristics, and the desired acoustic output. Simulation software is often used to model and refine the design.

In summary, a tapped horn subwoofer uses a unique placement of the driver and a carefully designed horn path to efficiently produce low-frequency sounds. It combines the benefits of horn loading with a more compact enclosure size, making it a popular choice for applications requiring efficient and deep bass reproduction in a relatively small space.

Tapped Horn Subwoofer Plans

There are many tapped horn subwoofer plans as there are subwoofer manufacturers and DIY sub-box designers today.  Some of the most common tapped horn subwoofer plans include:

1.     Eminence Tapped Horn

This is a large 20 Hz tapped horn for 15-inch drivers. The most suitable drivers for this plan are the obsolete Eminence EPS15-500 and the current Kappalite 3015LF, DEFINIMAX 4015LF, or MTX Audio T7515-04.

Eeminence subwoofer design

Eminence subwoofer

 

2.     30 Hz Tangband Tapped Horn

The mini Tangband tapped horn subwoofer has a small 4-times folded tapped horn. The plan fits a 6.5-inch Tangband W6-1139SC or W6-1139SG. An alternative plan to the 30 Hz Tangband is a 6-times folded version provided by Martin.

30 Hz Tangband Tapped Horn

30 Hz Mivoc Tapped Horn

 

3.     30 Hz Mivoc Tapped Horn

Developed by Volker, the 30 Hz Tangband tapped horn plan works well with the budget 10-inch Mivoc AWM104. The plan is estimated to deliver a free air resonance of about 31 Hz at 9mm Xmax.

30 Hz Mivoc Tapped Horn design

30 Hz Mivoc Tapped Horn

4.     38 Hz Tangband Tapped Horn

This is a 6.5-inch tapped subwoofer plan for Tangband W6-1139SC or W6-1139SG. It goes less deep but extends further up.

38 Hz Tangband Tapped Horn design

38 Hz Tangband Tapped Horn subwoofer

5.     38 Hz Double Folded Tangband Tapped Horn

This is also a 6.5-inch tapped horn subwoofer plan. It is suitable for Tangband W6-1139SC or W6-1139SG. The plan uses similar parameters as the 38 Hz Tangband tapped horn with the only difference being that it is folded and less tall.

6.     Conical Midbass Horn

This 77 Hz conical Midbass front horn is designed to fit an Electrovoice EVM15L. The plan has a 500 cm2 throat area (22.4 x 22.4) cm. The horn length is 77.3 cm and the mouth area is 2978 cm2 (45×66.2) cm.

Conical Midbass Horn design

Conical Midbass Horn subwoofer

7.     Tactrix Midbass Horn

This is a 150 Hz Tractrix Midbass front horn subwoofer plan that is meant for the Electrovoice EVM12L driver.

8.     Tractrix Midrange Horn

This subwoofer-tapped horn plan is based on Dr. Bruce Edgar’s Midrange horn article. The design covers a wide range of frequencies from 500 Hz to 5 kHz. It works well with JBL LE5-2 with a speaker offset of 1/4 inch from the baffle. According to Dr. Bruce Edgar’s article, the gap should be filled with air previous foam rubber.

9.     Klipsch Corner Horn

This is a Klipschorn plan adapted from the 1995 Klipsch design and adjusted accordingly. It fits 15-inch bass drivers.

10.10” Lascala Midbass Horn

The plan is also based on the original LaScala. It is however shrunk down by a factor of 0.67 so that it fits a 10-inch. It delivers midrange better than midbass frequencies.

Other tapped horn subwoofer plans include:

  • 15” Tapped Horn EASY subwoofer
  • Tapped horn D18/Subcoop D18 Plan
  • William Cowan’s 18 Hz tapped horn subwoofer plan
  • William Cowan’s 30 Hz tapped horn subwoofer plan

Tapped Horn Subwoofer Designs

Several tapped horn subwoofer designs are efficient and up to the task. Some examples included:

  1. Dual 18 Tapped Horn Design
  2. Danley Tapped Horn Subwoofer designs e.g., TH115, TH112, TH212, TH412, TH812, and THSpud

Tapped Horn Subwoofer Kits

Based on the several tapped horn subwoofer plans and designs, you can assemble various kits for a tapped horn subwoofer. Some of the speaker kits you can use include:

  • Selected speaker chassis
  • Quality screw
  • High-quality crossover components
  • Detailed blueprint for housing and crossover

Depending on the kit you have, you will need:

  • Electric wire
  • Terminals
  • Bass reflex tube and insulation material

It is an inconspicuous monolith that is full of dynamics. Surprisingly, the subwoofer works pretty well with the six-inch model (Omnes Audio SW6.01). You can buy the required wood from a carpenter of your choice or from well-stocked hardware.  

8” Tapped Horn Subwoofers

An excellent example of an 8-inch tapped horn subwoofer is the Monster 8” Diameter Units. It is an 8” tapped bass horn monster woofer from PMR and is a super subwoofer with low QTs, low Fs, high excursion, and high output.

With SAVAGE 8” drivers, they are great Hi-Fi units that sound fast, tight, articulate, and colorless.

18 Tapped Horn Subwoofer

Here are some of the 18 inch tapped horn subwoofers:

  1. THAM 18 – 18” Tapped Horn

This is a Johannes Robin subwoofer design. The build is 18mm plywood and the outer dimensions are 600x800x650. It works well with the B&C18TBx100 driver.

  1. Danely THE TH118 Tapped Horn 18 inch Subwoofer
  2. Martin Audio WLX 18” Horn subwoofer

12 Tapped Horn Subwoofer

12-inch tapped horn subwoofer designs also deliver quality audio performance based on the different use scenarios. Some of the best 12” tapped horn subwoofers include:

  1. MTH-30 12” tapped horn subwoofer
  2. VTC Pro Audio ELS212T Dual 12” tapped horn touring subwoofer; this is available in fixed and touring installation Versions Excellent for all throw distances low distortion with very high SPL, high clarity, Definition & Punch Advanced DLMS4080 Digital Loudspeaker management system.

10 Tapped Horn Subwoofer

10-inch tapped horn subwoofers are much smaller but still very efficient. A good example is the Danley DTS-10 tapped horn subwoofer.

Bass Tapped Horn Subwoofer DIY

An eight-foot-tall bass horn loaded with an 18” subwoofer is an excellent example of a bass-tapped horn DIY subwoofer. It is adapted from the William Cowan design but runs corner to corner as opposed to William Cowan which runs side to side.

DIY Tapped Horn Subwoofer

Building a DIY tapped horn subwoofer is not a detailed process. Most DIY projects are adapted from existing ones with minor adjustments. You can quickly try a DIY-tapped horn subwoofer or have it done by your local carpenter to your preferred specifications.

Folded Tapped Horn Subwoofer

Folded tapped horn subwoofers have the back of the sub placed closer to the horn. This way, the backward motion of the woofer produces a sound that augments the sound produced by the forward motion through the horn.

Folded tapped horn subwoofer designs are commonly used in tweeters and midrange subwoofers. This is generally because lower frequencies have longer wavelengths and require longer horns.

They combine the “megaphone effect” of the horn with the “rearward subwoofer travel sound utilization effect,” making them more efficient. A good example is the Wolfhorn SDX folded tapped horn subwoofer enclosure.

Small Tapped Horn Subwoofers

Small tapped horn subwoofers are similar in plan and design to other tapped horn subwoofers. They are however smaller in size.  

Horn Subwoofers vs Tapped Horn Subwoofers

Unlike normal subwoofers, tapped horn subwoofers do not require a large mouth exit to have a flat response in the pass band region of the frequency range. This is why a properly designed TH can have a flat response within its passband.

In addition, tapped horn subwoofers use the radiation from both the front and rear of the driver and combine them at the mouth.

In addition, tapped horn subwoofers offer about two octaves over a flat response which means they are subwoofers and not woofers

Tapped Horn VS Folded Horn Subwoofers

Both folded horn subwoofers and tapped horn subwoofers are efficient designs for producing deep bass frequencies, but they differ in their structural design and sound propagation methods.

A folded horn subwoofer features a driver positioned at the narrow end (throat) of a horn, with the horn path intricately folding within the cabinet to allow a longer path in a compact space, thus amplifying the sound through the horn’s expanding structure.

In contrast, a tapped horn subwoofer places the driver partway along the horn’s length (the ‘tap’ point), utilizing both sides of the driver to emit sound. This design allows the sound waves from the front and back of the driver to combine constructively, leading to efficient and powerful bass output in a potentially smaller cabinet compared to the folded horn design.

Both designs are known for their ability to produce deep, resonant bass, but they achieve it through different acoustic and physical arrangements.

FeatureFolded Horn SubwoofersTapped Horn Subwoofers
DesignDriver at the throat, with a horn path that folds within the cabinet.Driver placed partway along the horn ('tap' point), using both sides of the driver.
Sound AmplificationAmplifies sound through horn expansion from throat to mouth.Combines sound from both sides of the driver constructively for enhanced output.
EfficiencyHigh efficiency, especially in bass frequencies.Similar high efficiency, often more efficient in a smaller size.
SizeTypically large due to the length of the horn path.Generally more compact than folded horn designs.
Sound CharacteristicsKnown for deep, powerful bass, used often in professional settings.Capable of deep bass with high output and controlled frequency response.
DirectionalityMore directional sound compared to conventional speakers.Directionality varies with design, can be controlled.
Design ComplexityComplex to design, folding the horn within the cabinet is challenging.Complex design, requiring precise calculations for horn geometry and driver placement.
ApplicationsCommon in professional audio, concerts, clubs.Used in both professional settings and by enthusiasts for efficient, deep bass.
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Norvan Martin is the founder of BoomSpeaker.com. He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin