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Category: 20 hz tapped horn

During all my years in the business, I have been on a quest for the ultimate subwoofer. We developed a lot of horns over the years, and continue to do so, because horns have a number of desirable and beneficial properties compared to vented boxes. Other than building individual horns that are absolutely massive, or building a segmented horn comprised of many separate elements that combine to make one massive horn, there was not a practical way to build a subwoofer horn that was portable and would reach a minimum frequency of 30Hz.

I had to look for a more practical way to deliver the deep bass I wanted to incorporate into the horns. Eventually I designed a hybrid box that incorporated a vented section with a long, partially folded horn-loaded section. Although the box was also quite large, heavy and complicated to build, it was smaller and lighter and less complicated than the B-Zero… and it produced massively low bass compared to the B-Zeros.

That particular design was really time-consuming to build, so it was impractical from a size and cost point of view. It did go low but the long horn and the vented section still left something to be desired. What I then did was begin to develop a vented box to see what I could achieve with a highly optimized vented box.

What I got was a really magnificent, musical and ruler-flat subwoofer with massive deep-bass output capabilities and virtually unlimited power handling.

As good as it was, it still lacked the impact I loved about the horn-loaded boxes. In order to deliver both impact and depth I started combining the two types of boxes and found it to be challenging to integrate the two types.

20 hz tapped horn

I could get the super-deep bass I wanted from the vented boxes and I could get the massive impact from the horns but getting them to line up and do it together took a great deal of time, measurement and experimentation. When I finally got them to work together properly, it was magic! Not only do I understand and agree with the love for the impact of horns, I have improved upon it, to make it even more impactful.

Think of it this way, if a lb guy 80 kilogram hit you in the chest with a solid punch, it would be a hard hit, but if that man was lbs kilograms that hit would move you much farther! Why the reference?

To go an octave lower requires four times 4x the power, and displaces four times the air for the same sound pressure level.

If you can extend the power behind that initial hit by an octave, then it effectively hits four times harder because it literally is four times the mass of air behind the hit. This is effectively what we can do with the combination of the horns and vented boxes.

The reason we do it with vented boxes is because to do it with horns would take up more than four times the space and that becomes impractical for both portability and for floor space in a nightclub. Done correctly, horns are awesome and wonderful things, but they have limits. There are three factors that essentially limit a horns performance. The first is its length. For a horn to be effective at 30Hz, it needs to be Therefor, a horn must be long enough to support the expansion of the wave to the lowest frequency you need it to play.

This is the rate at which the area of the horn increases relative to the distance from the throat, or driver. As a general rule, the lower the target cut-off frequency, the slower the horn will flare expand. The combination of the long horn and the slow flare that are necessary to create a quasi-portable horn with good low-frequency sensitivity and relatively flat response demands a lot of folds and a lot of wood.

This makes their construction more complicated and more expensive to build, and makes the boxes heavier and larger.I thought that people who build their own subwoofers were fringe enthusiasts who cared more about building something than about sound quality.

It turns out I was completely wrong. Small cabinet size is a critical constraint. Infinite Baffle IB subwoofers use an enclosure that is nearly infinite in size.

The lowest possible frequency is typically between 18 Hz and 25 Hz. In addition, IB subwoofers can achieve perfectly flat bass response, which is impossible with most other subwoofer designs.

Horns V. Vented Subwoofers

The low frequency threshold of human hearing is about 20 Hz. The reason is simple: these are the frequencies that you can feel. In your chest. In your seat. As with all designs, there are trade-offs. For Infinite Baffle, the first constraint is cone travel. Infinite baffle designs typically use at least two inch woofers, but can use four or more inch woofers. The second drawback to Infinite Baffle subwoofers is low efficiency. Horn speakers a. Basically, the efficiency comes form the megaphone effect.

This speaker design is very common for tweeters and midrange drivers from companies such as Klipsch, but is extremely uncommon for subwoofers. This is because lower frequencies have substantially longer wavelengths that require substantially longer horns. A simple horn subwoofer has a straight horn that gradually expands.

The size makes it unpractical for home theater see photo. A folded horn subwoofer wraps around itself to reduce size similar to a tuba.

Ultimate Home Theater Subwoofer Designs

A folded tapped horn subwoofer has the back of the subwoofer placed near the horn exit, so the backwards motion of the woofer produces sound that reinforces sound produced by the forward motion through the horn. However, most of the efficiency benefits can be realized by using half-length 15 feet or quarter-length 7.

This enclosure size is small enough that it can be integrated into a home theater room, such as a riser under the second row of seating. A conventional subwoofer design requires hundreds of watts to achieve this Sound Pressure Level.The first tapped horn we built was this 60Hz version.

This cut off was chosen for economy of timber and ease of manufacture. It was initially designed around the Eighteen Sound 10W This driver appeared excellent for this application, and the guess was right. Out of all the horns we built, this one had the flattest bandpass and the greatest frequency range, being essentially dead flat from 50 to Hz.

20 hz tapped horn

Here the driver is being moved up the horn, away from the mouth and throat. This plot shows the results of two different drivers being tested in this 60Hz tapped horn. The second tapped horn was essentially a scaled up version of the 60Hz horn. A more suitable driver was chosen for the frequency range of interest.

This horn was used as a subwoofer in my main home system for a while, and now resides in my second system. The output this horn is capable of in a package one person can carry is quite astounding.

This plot shows the results of two different drivers being tested in this 30Hz tapped horn. Red - Peerless Brown - Peerless I now believe this measurement is not correct. Anyone who wants to make a great little tapped horn similar to this one should make a few changes. Combined with a Peerless XLS driver, I measured a flat response from 30 to Hz and more than dB output with W of drive, when firing from a corner.

In half space the maximum output will be around dB at 1M and W. To get a feel for what this is like, it would take four 's in a liter sealed box driven with WRMS to achieve the same output as this liter box with one driver at WRMS.

The tapped horn has more output than the four driver sealed box right down to 20Hz. The Peerless is a very suitable driver in a 30Hz tapped horn, with it's 49Hz resonant frequency, good excursion and strong cone assembly.

Here's a photo into the mouth of the version of the 30Hz Tapped horn. The driver will have to be mounted this way around to fit the magnet in. There has been a lot of discussion on the diyAudio forums on the Collaborative Tapped horn project about modelled versus predicted response of Tapped Horns.

20 hz tapped horn

In this example I will show a model of a 35Hz tapped horn, and compare it to the measured response. Here is the predicted response for this 35Hz Tapped Horn.

20 kHz Catenoidal Tapped Horn (Ti)

The 56V RMS input power level was chosen because this corresponds with the power available from the power amplifier that drives these Tapped Horns. A drawing of the construction of this Tapped Horn. It is a simple single fold horn with a straight sloping driver baffle. No stuffing or lining was used in this construction. The measured response of the Tapped Horn. You can see that the measured response of this tapped horn corresponds very well with the predicted response generated by HornResponse.

The Q of the out of band resonances is slightly lower than predicted. If the horn path was lined with absorbant foam, or similar, the Q of the out of band resonances would have been even lower, also reducing their amplitude. I chose not to line the horn path because the desired final response could be easily obtained with the DCX that was doing crossover duties. In use I was unable to get more than mm of peak-peak excursion from the driver when driven with an amplfier that was close to clipping at peaks of more than W RMS.

When trying a particularly brutal Slayer track with lots of very fast kick drum the smell of hot voicecoils became quite obvious. The thermal limits of the driver became a problem well before the 25mm peak to peak xmax.Usually only drivers which have high efficiency, low Qts 0.

Tapped horn alignments also tend to be more suited to pro audio duty rather than home subwoofer duty, due to the size requirements needed to execute a "proper" tapped horn, where the gain at the higher end of the passband is enough to ensure that any out of band response peaks are not significantly higher than the passband.

Nevertheless, there are several DIY examples of tapped horns with significant out of band response peaks available on the Internet. One of the problems with taking that approach however is that those high out of band response peaks also amplify any harmonic distortion components that happen to occur at the same frequencies, and those cannot be eliminated by those methods. The net required volume will be smaller and you won't have to deal with the out of band response peaks. You will be giving up a bit of efficiency in the process however.

Tapped horns are a bit more complex than transmission lines to design and therefore you should spend a lot of time making sure that your simulation is correct before committing it to wood to make sure that you're not disappointed with the results.

Design Notes: For these design notes, I will step you through the design process for a simple single-expansion tapped horn.

My tool of choice for designing tapped horns is Hornresp.

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There may be better tools out there, but Hornresp is simple to use once you learn how to use it! This is a cheap but decent quality 12" pro audio driver with a nice low Fs and Qts, making it suitable for a number of different designs. The following image shows the parameters for a Hornresp sim of this "classical" type of transmission line. A brief outline of what's shown in the sim above: Ang - for comparison purposes, this shouild always be set at "2.

At this point, we can select "Tools Now, let's see what the predicted response of this sim looks like As is expected with the use of an end-load design like this one, there's this massive notch in the response between Hz and Hz. Now, let's see if we can deal with that notch by using a tapped horn alignment instead.

First, let's change the Hornresp sim to that of a tapped horn. To do this, we're going to add values for S4 and L34, change the L34 expansion to "Par" and change the type of simulation from OD offset driver to TH tapped horn. Let's have a look at what the response looks like, by using Hornresp's Loudspeaker wizard. It should not look much different from the end-loaded transmission line's response, because we haven't really moved the driver to the best location yet to extend the passband.

From this point, we're going to "move" the driver's location into the line, by adjusting the values for L12 and L34, using the simulated schematic as a guide. The result will look something like the diagram below.

Now, we need to adjust the length and taper of the line to achieve the flattest frequency response. To do this, we're going to set the calculation for S2 and S3 to "Auto" by double-clicking where it says "Manual"and basically adjust S1, S4 and L23 and L12 and L34 if necessary until we get something useful, e. Illustrated below is just one possible tapped horn alignment for this particular driver that meets most of these requirements.

The tapped horn alignment illustrated above is large compared to an offset transmission line alignment with the same low frequency extension using the same driver, but it also is quite a bit more efficient. The out of band response peaks are around 6dB above the passband I would aim for them to be no higher than thatand the passband itself is not quite flat, so it's not perfect, but it's a good compromise.Here's my latest project.

This is another sub that I read about over at the AVSforum. The subwoofer enclosure can be bought as a pre-cut kit with the driver purchased seperately. You can also cut the panels yourself and save the cost of the kit which is what I normally do. The kit looked intriguing so I went that route.

For a kit that a couple of DIY'ers put together, I was extremely impressed. It's all CNC cut, panels labled, driver gasket material, speaker wire, ends and terminal were all supplied.

Everything fit together perfectly with no modifications.

20 hz tapped horn

There was even some pre-drilled holes with supplied screws for some of the interior panels. You can literally go from the kit to a working sub in a weekend. I've got mine put together and interior horn painted in a few hours of a Saturday and Sunday.

Next weekend, I'll roundover the corners and paint it.

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Those facts alone make it an impressive feat for this sub to go to 25 Hz. It's the only driver that will work in this box. Hey, I've been busy! The driver is an Exodus Anarchy. Looks like the pics I took with my daughters camera are too big.

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I'll try to resize and post some more later. I primed and painted the small area under the terminals to avoid painting around them later on. The flash caused some funny reflections but it will be flat black when I'm done. Installing the last side with my KP press assembly.

Hopefilly I'll have listening impressions next weekend. I'll pair this with my KP's on my back porch. I forget to add the link at the AVSforum that discusses the sub. It can be found HERE. There's a point in the discussion of the little sub where it's compared to the THT like yours. The little sub actually has the same extention of the THT but naturally won't get as loud due to the smaller driver.

Good question. It takes a little over five 6.Bye bye power compression. What sort of excursion do you see at 1w? It's more like 93 dB. The slight drop around 20 Hz will often be raised by room gain. Excursion peaks at around 29 Hz at 0. By contrast the sealed version has 1mm before EQ - 9 db is needed to get it up to 89 dB to match the tapped horn. So about four times the excursion! A much better way that just adding more power and excursion. To get 89 db from the Exodus Maelstrom 18" in a L sealed box you need 6w or just over 1w in a L vented box.

The sealed box needs 2 kW to achieve dB and so you need 4 kW and two drivers to match the tapped horn. It takes up the same space and you are using more than FIVE times as much power. With a vented version you can match the tapped horn with just under 2 kW and a box around the same size. You get the advantage of a wider bandwidth although the driver is no longer available.

In a conventional system, it ends up being cheaper overall to get a driver like Maelstrom and use a lot of power, say some of those Sanyway Lab Gruppen clones. Cheaper because you don't have to add another amp and two more woofers. However I like to separate bass and sub bass, using brute force for the bottom octave and high sensitivity woofers. The SGR Illuminator is startling in its dynamic output capability and a big part of that is having each set of drivers cover a narrow bandwidth.

They are low sensitivity drivers.

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This kind of setup is ideal for a horn system and for the "musical bass range" above 40 Hz, my system is sealed yet with no EQ boost. One thing that is remarkable about this tapped horn is the lack of box vibration due to the dual opposed mounting.

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The surrounding walls vibrate much more than the box itself, due do the cancellation of mechanical vibration. This is critical for an installed subwoofer.

You can test this out by turning off one driver - the output drops by 6 dB but the vibration increases. All comments are moderated. February 23, How does the sensitivity of tapped horns compare? Here is a simulation to illustrate.Many others will work as well — just give them a try with hornresp.

Except the inner bracing, which were 16mm, the thing is made from 22mm MDF. All connections are glued and screwed. It took me a weekend to build it. This is my old Eminence EPS in place.

Here it is in my room. After errecting it in the corner it still looks large but not as bad as before, when it was laying in the middle of the rool.

8 MTH-30 Tapped Horn Subs outdoor

Paint will be applied in spring and of course, If I still like it then. The mouth points toward the left hand side. In the evening I did some testing.

I heard some music and watched a movie. It sounds very effortless and goes deep down. Great for HT and music. I also made a less tall version of the TH vs. Low end is just a little compromised. Here is the comparison of predicted responses:.

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Plans can be found in the download section. The predicted response: The parameters of the simulation: The excursion simulation: Regarding the room gain I like the idea of EQing the response down and gain some headroom. This gives you an overview on the folding: And this is what it looks like during building: Except the inner bracing, which were 16mm, the thing is made from 22mm MDF. When I brought it into my room first, I thought: Oh my god, this thing is big.

Here is the comparison of predicted responses: Plans can be found in the download section.


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