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A little background first: I’ve been actively involved in the audio community for quite some time, and have built many, many speakers and subwoofers. Full range, multi-way, front loaded horns, rear loaded horns, transmission lines, open baffles, isobaric, you name it. I don’t believe in fancy cables or mystical noise filters, just sound engineering along with repeated listening and measurements. The purpose of this instructable is to demonstrate a different way to build subwoofers, which has become my absolute favorite method for low frequency reproduction: the tapped horn. The tapped horn is a relatively obscure subwoofer arrangement, only recently brought to prominence by Tom Danley. A tapped horn is unlike other horns, in that it uses the radiation from both the front and rear of the driver, and combines them at the mouth.
This allows for many possibilities, including greater efficiency, smaller enclosure size, and deeper extension. One of the greatest benefits a tapped horn exhibits over other arrangements is lower excursion (the distance a woofer moves from rest). Because of the acoustic load placed on the driver, excursion is reduced, leading to increased maximum SPL and lower distortion.
My goal of this instructable was to build a versatile, affordable, small, and high performance tapped horn that someone with reasonable woodworking skills could assemble. Don’t just think of this as another common sealed or bandpass subwoofer tutorial, this is a much different realm, and is also significantly harder to build. It utilizes two 8 inch MCM 55-2421 drivers, which cost $28 each, and perform at a level of drivers costing magnitudes more. Add a sheet of plywood and few bits of hardware, and you have an excellent tapped horn subwoofer for $120.
How much would a tapped horn cost commercially? Well, the most affordable tapped horn sub I know of is the TH-Mini, which runs about $1300 per piece. For less than 1/10th the price, you can see what all the fuss is about. Now, without further delay, let’s make some sawdust! What would I do with a Shopbot? Tom Danley had hinted at offering a kit for a multiway tapped horn speaker, but because of limitations with time and a focus on the professional market, it is something that will not happen. However, he was very supportive of the idea, and offered to license the technology to a third party if they wanted to tackle it.
If I were to get a Shopbot, I would pursue a licensing agreement with Danley Sound Labs to provide these kits at a very low price. It would be my way of giving back to the community for a Shopbot that I didn’t have to pay for. A Shopbot can precisely cut the complex angles and provide the precise alignment that is necessary for such an undertaking, not to mention do it at a rate that would allow production costs to be kept very low. I designed this tapped horn using three different programs: Hornresp (horn response), AkAbak, and Sketchup. All are free, but all have a learning curve, some of which are steeper than others. I won’t go into how to use these programs, as there are tutorials online if you are interested.
If you haven't worked with speakers in the past, you will have to spend some time educating yourself on the various parameters and meanings. If you need any help, or want guidance on where to find info on using HornResp or AkAbak, feel free to ask questions in the comments section! The arrangement of the driver is roughly similar to the TH-Mini, which has the driver on the bottom of the cabinet firing down into the throat.
I designed mine in a similar fashion, as it works well in a cabinet this small. I’ve attached my Hornresp input file, as well as the Sketchup file with a 3D model.
The cabinet is approximately 30”x30”x10”, but the 10” width can be increased to smooth out the response if materials and space allow. Please note that I did not follow the model I made in hornresp exactly. I changed the flare at the end to use as much space/wood as possible. The predicted response won't be far off, subtle changes so far down the horn have little effect. When using a tapped horn, one has to be very careful about low frequencies that are out of the pass band, as excursion rapidly increases. An active high pass filter is what I generally use, but a passive high pass filter would work just as well.
I'll explain later this in greater details later. The MCM 55-2421 can be found online here:you search for the 55-2421 on the MCM website, the price will be $38, but when I search for it in Google shopper, it is only $28. Not sure exactly why, but check to make sure you’re getting the right price.
My total came out to $71.49 for two drivers including shipping. Plywood: I used one 5x5 sheet of Baltic Birch ½” plywood, and one small scrap piece of ¾” plywood for the baffle the drivers mount to. You can use all ½”, I just had the ¾ on hand. Bought this from a local wood company for $44, and it’s high quality void free plywood.
Try not to skimp here, and DO NOT use MDF. A well braced plywood cabinet is superior to one made of MDF, and the additional stiffness is noticeable in both sound quality and overall strength. MDF also contains formaldehyde, which is used as a bonding agent, and cutting this stuff is nasty business.
Even with a respirator, it will get everywhere in most non professional wood shops, and it is simply not a risk worth taking. For a unique look, bamboo plywood can also be used, which I have used in many of the speakers I’ve built. Binding posts: I chose to use a Neutrik speakon connector ($2), as I like the cheap cost, secure connection, and fully insulated design. Feel free to use anything that works for your application.
Wire: I used some extra bits of 16 gauge stranded copper here, but any decent copper wire should be fine, given that it is at least 18 gauge. Glue: I have a large bottle of Titebond II that I use for most woodworking projects, but will also use PL polyurethane adhesive. Achieving a good seal is very important in any horn design, and the expanding nature of polyurethane can be helpful in sealing up any potential voids. $71.49 for the drivers, $44 for plywood, and $2 for the Speakon puts the cost at right under $120. Add a little more if you need glue and use a passive crossover. Now that all the pieces are cut to dimension, it’s time to sketch out how the internal panels fit to the side panels.
I use a straight edge and pencil to sketch how things should look, using my Sketchup drawing as a guide. I just marked the interior corners of the horn path, and line up the pieces as I assemble the horn. One thing that is worth noting is the position of the drivers. In my Sketchup drawing, I only placed them in an approximate location. The exact location of the drivers is important to how the horn operates. We want to maintain a compression ration of approximately 3:1 to 4:1. This ratio is the total area of drivers (each driver is 210cm squared, so 420 total) to area of the horn at the point where the drivers fires into the throat.
So to maintain that ratio, we want to have the drivers centered at point in the throat where the area is around 100cm squared. This will change depending on how wide your cabinet is. If you cut your panels to 9.5” like I did (roughly 25cm), that would mean the drivers should be centered around the point in the horn that is 4cm tall. I simply test fit the baffle piece, measured the point at which the height was 4mm, and made a pencil mark. On each side of this point will be a driver, oriented as close together as physically possible.
Don’t fret about this too much, as I’ve found these drivers can actually handle a variety of ratios without problems. Drill the proper holes for your input connector(s) on the back panel, and the holes for the speaker drivers. I used a circular jig attached to a router to do the large speaker cutouts (7.125” hole for each), and used a roundover bit to smooth the transition from driver to throat (note: only do this on the side facing the bottom). The speakon connector is slightly larger than 7/8', I used a forstner bit to get the approximate size, and reamed it out with a file. I also drilled two small holes in panel A for the wires to connect the input connector to the drivers. Don't forget to seal these with some glue or caulking, we don't want any leaks between chambers!
Now that everything is cut to size, start gluing pieces together. I start with the front panel and top piece, and work my way back, constantly checking to be sure things are square. All internal pieces are glued to one side first, making sure to use plenty of glue to avoid any leaks. A brad nailer can make things go faster, but I just use wood glue and a little patience.
If you cut the pieces with some accuracy, this should be a straightforward process. One all the internal pieces are glued in place, it's time to install the drivers. I use a set of heavy duty screws, but bolts and t-nuts are also often used. When wiring the drivers, the amplifier you are using must be considered. Each driver has a rated impedance of 4 ohms, so you can wire in series for 8 ohms or parallel for 2.
I went with parallel wiring, and have an amplifier that can handle low impedance loads. If you want to add a passive high pass crossover to prevent over excursion out of the pass band (don't ignore this, use either a passive or active filter), it will change depending on how you wire your drivers. In both cases, there is a capacitor in series with the drivers, and a inductor in parallel with them. Here are the values for each wiring scheme:Parallel (2ohm load): 1600uf capacitor, 12.86mH inductorSeries (8ohm load): 400uf capacitor, 51.4mH inductorThese values don't have to be exact, just try to get as close as you can. I've also provided the modelled excursion of the drivers at their rated power.
These drivers have an xmax (maximum one way excursion) of 8mm. As you can see, as you go below the low corner at 40hz, excursion quickly increases. At 30hz, you are above the rated max excursion. A high pass filter greatly reduces the chances of damaging your drivers due to over excursion, so please use them! Wire the drivers to the input connector, seal the holes with caulk/glue, and take a final look at your handiwork: once the other side is glued on, you won't be able to easily access the internal workings!
Apply a generous amount of glue to the edge of all internal pieces, and clamp the final side in place. After patiently waiting for the glue to cure, place the sub in a desirable location (corners will increase the low end response even more), and connect to an appropriate amplifier and high pass filter. Slowly bring the volume up, as long as you wired things properly, you should be able to hear output.
As you crank up the volume, you will soon see just how much. When modeling this in Hornresp, the predicted maximum output was a stunning 122 dB at 40hz!
For two 8 inch drivers in a 130 liter cabinet, that's pretty impressive! I hope you've enjoyed this tutorial, please comment if you build this tapped horn, feedback always appreciated!
Are you still looking for a way to build a full-range (mutli-way is a bit clumsy) tapped horn? It is single 12' subwoofer w/19mm xmax tuned to 17Hz in the tap, with a 10' woofer in a divided ported 'enclosure' also containing a 6' sealed back midrange, and two 3' bullet horn tweeters in a small dead-space 'enclosure'. I use a NADY active 3-wat crossover with subwoofer control between the source and the amps, and the system is stereo tri-amped. I roll the tap off at 100Hz, the 10' off at 250Hz, the mid off at 3500Hz, and let the horn tweeters scream. Iti is positively lethal as a pair of corner stereo speakers, or you can fly them in the corners of a high-bay shop like I do for a more open, concert-y sound aura. I used a spectrum analyzer and a Behringer 31-band stereo concert rig EQ to get it just right. Now, to me, that means on sustain guitar solos, and sudden stops in-song (think KISS Firehouse at the beginning on Alive!
Or Angus' The Jack solo on If You Want Blood, You've Got It), my steel roof trusses ring just a tad, and the whole freaking 38X40X16 room just hums, just like in an arena. I'm pushing a total of around 1,100Wrms, but never all the way up.it's just too much. But I always wanted a sound system that would go louder than I want to listen. I push it to about 108-110dB as measured by an SPL meter in the center of the shop. 110 is a LOT louder thatn 108. But it will hit about 130 @ 20Hz, and it will murder you at 10kHz, something like 133dB. So never all the way.
The knob goes to 11, but my ears say stop at 6 or 7. Best thing is these things are only about 5'X2'X3' each. Heavy, heavy, heavy though. Gantry hooks and airline cable to fly them. Glue a rubber truck-bed mat on the bottom to floor stand them. They don't go down to 10Hz like lilmike's lilWrecker, but they will rock your world.
I am going to try to get them patented, so I can't share the actual plans just yet.but I can give you more hints than I have, and I can tell you that there are some significant hints in this message. So, if you're still pondering it, drop me a note.
Steve Johnson 'If it's too loud, you're too old!' Usually a folded horn refers to a sealed enclosure with an extended, typically 'folded' horn to act as a waveguide to extend frequency response and improve loading and acoustic impedance matching. Though I've never built one, I believe bill fitzmaurices designs are based on folded horns. In addition, there are back loaded horns with the front of the driver radiating into the listening area (often used to increase the frequency response of full rangers in older vintage designs) and the tapped horn like this one which combines both front and back loading with the waveguide effect of the horn as well and frequency reinforcement from the length of the line.
There's a lot to learn about the different designs and sometimes youll find a few designs that overlap a couple different categories of horns or enclosures. I am no speaker builder and I don't know a ton about horn design, but I think I know more than you. I would say:1.
Probably not. A lot of math goes into designed the size and shape of these boxes, and they are calculated based on the driver size. A single 15' driver would probably request at least a different size, and maybe shape too.2. I don't know of any horn subs that people are building out of plywood.
Maybe you could, but your sound would probably suffer. Use MDF if you want to go cheaper, but that will drastically increase your weight. If you are worried about weight, you shouldn't be building a tapped horn sub at all, and you definitely should not be carrying this on your bike.I've been using this sub in my home for a year and a half, built almost entirely to spec by a horn builder in Boulder, CO, and I love it. The only thing different that he did was use a more durable, harder wood, actually salvaged from an old desk. I don't know what kind of wood it is, but the sub is very heavy and rock-solid.I am using probably the same plate amp that one of the users below posted.
It sounds great, especially in a small to medium-sized room. Definitely do not use this in a large room.
Even for a medium sized too, I would probably recommend two of these, or perhaps a different sub. One of the more difficult things with this sub has been playing with the placement. It truly sounds best corner-loaded.
However, I have found that it does not sound that great simply in a corner firing out. It is a very 'directional' sub, and you loose a lot of the bass if you are not standing right in front of it. Best to fire it directly into the corner of a room (either right at the corner or at a right angle to one of the corner walls, which is what I am currently doing, just a few inches from the wall). This way, the bass expands around the room to fill the entire room. If you are doing this, and also because it is a folded horn, you will want to incorporate delay into your speaker tops, as the bass frequencies will be exiting the mouth of the horn after the high frequencies exit the tops.
I use a Behringer external PA crossover (CX-3400) and crossover at about 180 Hz. Really sucks that the plate amp doesn't have a crossover built in, but oh well. The CX-3400 gives me a lot more control with other things too. I am not able to edit my post. Sorry for the spelling mistakes.After thinking more about it, one of these in a medium-sized room in a home would probably be fine. I should mention that I am a deep house & techno DJ, so I play a lot of bass music.
Heavy bass in the 30-40 Hz range is very important to me, and this sub does an excellent job at handling that. However, like I said before, playing my music in a slightly large room with this subwoofer would not suffice.
I would need two of these probably. But if you play a lot of jazz, rock, or other music with significantly less bass, that would probably afford you more wiggle room with this sub.Other notes: including about $100 labor for someone to build it for me, the sub probably cost me about $250 (not including the amp). Pretty great price for what you get. As you can see in the photo, I built it with parties in mind.
I wanted it to be durable, portable (handles), and protected. I realized after two parties in my medium-sized basement space that this sub was not intended for that. It could not handle high SPL deep bass at a loud party. I blew one of the drivers after the second party I think, which was really not a big deal at all, because a new driver was about $30 and not difficult to install. For home listening, this thing is great. For PA applications, go with horn subs built for that. We are currently using Bill Fitzmaurice PA speakers.
Specifically Titan 48 subs with DR280 tops.
Hi,I have been searching for a while and had trouble finding the basics of building a tapped horn or folded horn subwoofer. I have a few questions, any useful links would be appreciated or anyone with experience in building them please add some light.1. What is the key difference's between a tapped horn or folded horn subwoofer?2. How do you model them? Or what is the best way to model them?
(step by step approach would be good)3. Is the sound quality of a properly designed folded or tapped horn subwoofer less or better or equal to a bass reflex cabinet?4. Are specific drivers better than others when it comes to using them in horn loaded subwoofers.If I can get these questions answered, I will be willing to make some saw dust. Originally Posted by DL86Hi,I have been searching for a while and had trouble finding the basics of building a tapped horn or folded horn subwoofer. I have a few questions, any useful links would be appreciated or anyone with experience in building them please add some light.1. What is the key difference's between a tapped horn or folded horn subwoofer?2. How do you model them?
Or what is the best way to model them? (step by step approach would be good)3.
Is the sound quality of a properly designed folded or tapped horn subwoofer less or better or equal to a bass reflex cabinet?4. Are specific drivers better than others when it comes to using them in horn loaded subwoofers.If I can get these questions answered, I will be willing to make some saw dust.1 - There may be some blurring between the two, but a tapped horn has one side of the driver firing into the horn at the 'throat tap' (S2 in hornresp), and the other side at the 'mouth tap' (S3 or S4 in hornresp).2 -flick through the help file to the section on tapped horns. The tapped horn wizard is where you'll do much of your tweaking. Maybe try someone else's input data as a starting point while you're learning.3 - Tapped horns have gotten some very good subjective reviews, both commercial boxes from DSL and diy builds.4 - Yes. For tapped horns it's easiest/most optimal to use a driver with Fs higher than your intended low cutoff of the horn. In my (very limited) experience drivers with higher BL will still produce a flat enough response with horn cutoffs higher than Fs. Depending on your application, you may have trouble finding a driver with correct Fs and enough Xmax.
Originally Posted by brandonnashThe problem I have with the collaborative tapped horn thread is that its done mostly by people that already know about horn subs. I would, probably like dl86, to see a good beginners thread. Maybe a search for horn speakers in general would help to get a starting knowledge?I completely agree.
I kept reading even though I didn't really know the terminology, it started to make sense after a while although I don't think I'd remember now if I tried to read it again.William Cowan's got some information on tapped horns at his site as well, follow the 'Tapped Horn' link on the left. I've been modeling drivers for months in Hornresponse and I've got a list of drivers that I think look suitable for a TH build at least from my limited understanding. I plan on posting them up at some point. I'd love to see some more people try TH's or regular bass horn builds and document them. I just haven't had the time to try one yet.
Aside from the design challenge, actually laying out the path length, angles, folds and designing the enclosure in a compact and well thought out manner could be challenging. I built a 20hz tapped horn with a B&C 15PS100 driver about a year ago. It was my first design/build along with two front loaded horns.IMHO tapped horns are fantastic performers and when I get a bigger space I'll be building more.
The main trouble with them (as someone else noted) is they are very large and heavy, it really takes two people to build them.My build is on page 95 of that huge thread over at DIYaudio and there's even 'napkin' diagram with dimensions.You'll save yourself tons of time if you can just copy someone else build.Erik also has some detailed plans here. Good luck with it!
Originally Posted by RicciThat sort of thing just don't go around here.where's the fun in that? Seriously though for me the problem is nobody has done a build that I'd want to copy yet.After you build your 18' LMS TH, I will copy you and build a smaller version for my 15' LMS.and with that shall begin an unending string of LMS copycat tapped horns. But you, my son, must initiate this epic journey.Seriously, I still am not excited about having to cross an LMS TH at 50Hz or so and lose all that mid bass goodness.
How high up frequency-wise did the TH-50 go cleanly? Originally Posted by RicciThat sort of thing just don't go around here.where's the fun in that?
Seriously though for me the problem is nobody has done a build that I'd want to copy yet.Cowanaudio.com has a 18 hz tapped horn, but I think he used a driver that's not available to the public. He also has no build plans for that one. Most of the builds I have seen for tapped horns are 20-30 hz. For that I could just get multiple cheap drivers in standard boxes and roll with that. Give me a mid teens or lower horn with 125 db and I will be happy.Problem I see with some of them is because of the nature of the enclosure interacting with the driver, xmax may not be reached, but the thermal limits can be reached sooner. That can be hard to deal with if you don't know the limits. Good drivers with stout voice coils shouldn't have a problem though.
Originally Posted by FatawanSeriously, I still am not excited about having to cross an LMS TH at 50Hz or so and lose all that mid bass goodness. How high up frequency-wise did the TH-50 go cleanly?I have to walk before I can run.Remember I only heard the TH50 for a very limited amount of time in an unfamiliar environment. All I can for sure say is that it will get very loud and sounds very clean and uncongested while doing it. Big dynamics. I need more personal time with 4 of them in a small apartment.
I'm not sure how high up the useable response goes. I thought I detected a bit of something going on up top when the crossover was at 100hz, but who knows. It could've been anything really. The poor little bookshelf mains were basically an afterthought at the levels we were pushing the TH50.The Hornresponse models always have quite a bit of hash up top, but then I've seen some actual measurements that look considerably better. I've never built one and only briefly listened to others, so I don't know any more than you do. The guys who have built one say that it is not nearly as bad as the simulations predict and the Danley graphs certainly look good. (Who's to say that the DSL team doesn't have some magical enclosure tricks on a sacred scroll though?).
Originally Posted by RicciI have to walk before I can run.Remember I only heard the TH50 for a very limited amount of time in an unfamiliar environment. All I can for sure say is that it will get very loud and sounds very clean and uncongested while doing it. Big dynamics. I need more personal time with 4 of them in a small apartment. I'm not sure how high up the useable response goes.
I thought I detected a bit of something going on up top when the crossover was at 100hz, but who knows. It could've been anything really. The poor little bookshelf mains were basically an afterthought at the levels we were pushing the TH50.The Hornresponse models always have quite a bit of hash up top, but then I've seen some actual measurements that look considerably better. I've never built one and only briefly listened to others, so I don't know any more than you do. The guys who have built one say that it is not nearly as bad as the simulations predict and the Danley graphs certainly look good. (Who's to say that the DSL team doesn't have some magical enclosure tricks on a sacred scroll though?)I use the term, 'secret sauce' to describe those magical tricks inside the box.
Danley has much sauce, as do Seaton's Terraform XLs. Wizards of Condiments they are!If you look at the second to last graph on the tapped horn page at cowanaudio.com it appears to measure the hash exactly as predicted. I wish he has some more info on his 18Hz model there as well. Originally Posted by VinculumI've been following Myn's THT folded horn thread daily over at Bill Fitzmaurice's forum. He is close to finishing, so I'm excited to hear his impressions.
It doesn't use an uber driver, but interesting none the less since Home Theater is his application and he's coming from an EBS subwoofer.Dr VI was actually caught between doing the THT and a Tapped Horn, notably a TH-SPUD clone using the Danley leaked plans.I'm anxious to hear how the Tuba HT (THT) sounds in contrast to my EBS/LLT. Such designs were all the rage in the Pro audio world years ago, until Mobile PA production companies couldn't find grunts who were willing to move them!along with 100+lbs amplifiers and the like.
We left them in leased venues where they could stay long term. Searching around the older clubs and other dives you can still find them, under stages or stripper poles.( I know of one such place if anyone's interested? Each folded line is nearly 30ft long.) As a built in, such as a stage as someone mentioned earlier, a TH makes good sense IF you have the space. If space is limited and it must be mobile, there's better options for the modern HT IMO.
Originally Posted by mayhem13If space is limited and it must be mobile, there's better options for the modern HT IMO.Agreed, after doing the math I would have no room for a 20 hz horn in my current location. But when I move to a bigger house I will be making one, maby two. TH enclosure's seem like the most logical way of achieving the most out of a single driver, much less THD, less excursion requirements and less power to reach a certain volume level giving you much more headroom. For now my 21' reflex cab and pb-13 ultra provide more bass than I can use, my mains struggle to keep up with that combo. Originally Posted by mayhem13Such designs were all the rage in the Pro audio world years ago, until Mobile PA production companies couldn't find grunts who were willing to move them!along with 100+lbs amplifiers and the like. We left them in leased venues where they could stay long term. Searching around the older clubs and other dives you can still find them, under stages or stripper poles.( I know of one such place if anyone's interested?
Each folded line is nearly 30ft long.) As a built in, such as a stage as someone mentioned earlier, a TH makes good sense IF you have the space. If space is limited and it must be mobile, there's better options for the modern HT IMO.One of the main reasons horns are so popular is because where you previously required 8 traditional aligned cabs (sealed/ported), you can get away with half as many (4) horns giving the same output with less.I know Bill Fitzmaurice horns are extremely light (under 100lbs).I'm building one now to replace my LLT/EBS.