DrWho Posted August 29, 2007 Share Posted August 29, 2007 After reading so much about tapped horns I decided it was time to sit down and build one myself. In an effort to save money, I tried to come up with a version that could take advantage of my Ascendant Audio Assassin 12" drivers. Previously I was running two ported cabinets with one driver in each, tuned to 16Hz. I wanted to use just one driver, but the Assassin doesn't model up very well so I was forced to build a tapped horn that used both. I plugged away at the numbers for a few days until I came across a feasible sized cabinet and ended up with a unit measuring 12" x 30" x 70". It took a total of 3 sheets of plywood, a large box of screws and two canistors of liquid nails. We also managed to find gobs of carpet padding to be used as damping material inside the enclosure. Including the cost of the drivers, I think the entire project cost about $350. I will be posting pictures shortly, but thought I'd share some pics of the design predictions versus the actual outcome. I'm also providing a comparison against the ported cabinets that the drivers were originally mounted in too. So here's the Hornresp program predictions and design criteria: Quote Link to comment Share on other sites More sharing options...
DrWho Posted August 29, 2007 Author Share Posted August 29, 2007 And then here's the measured data of the sub versus the horn. Red = Ported Sub Blue = Tapped Horn Quote Link to comment Share on other sites More sharing options...
DrWho Posted August 30, 2007 Author Share Posted August 30, 2007 The huge dips around 55Hz and 60Hz are room related and should be ignored. The room also exhibits some peakiness in the 40-50Hz region. So basically the passbands from 40-70Hz on both designs are essentially flat. The huge dip at 82Hz I believe is related to a panel resonance inside the cabinet... I think one of the most insane things about this build is how much bracing went into the design and then how much panel vibration there is. It's annoying because the large panel faces in the design don't need to move much to create significant sound so I'll be going through and trying to brace the crap out of everything from the outside now. The raw output is almost scary (a theoretical 130dB with only 350W), but until I get these vibrations taken care of I'm not going to be able to enjoy it fully just yet. In the modelling program I have the woofers wired in series which presents an 8 ohm load to the amplifier. Right now I have each driver being powered by a seperate channel on the amplifier. One thing for sure is that I will need a little filtering to bring down the peaks above the desired passband (~160Hz in the simulation). Also, the sound coming from the horn is noticeably arriving much later than the mains...so I might try to implement some DSP that will provide a delay on the mains to help time-align everything. Anyways, I'm just posting this here in case anyone else wants to persue some tapped hornage and wants to learn from my mistakes. I would be more than interested to help facilitate the design process too. These horns are really cool. Stay tuned for more experiments too...I have a few ideas that might be better than the tapped horns, but I wanted to build a classical version first to gain the experience and limit the amount of unknowns and all that. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted August 30, 2007 Share Posted August 30, 2007 Cool! Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted August 30, 2007 Share Posted August 30, 2007 Can't wait to see the pics. Speaking of tapped horns, did you ever figure out what the capped PVC pipes in the Danley were for? They remind me of the plumbing on some new vehicles air intake. The banufacturers install blind plugged tubes off of the section of air intake plumbing inbetween the air filter box and throttle body. I've always thought that they were for tuning somehow. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted August 30, 2007 Share Posted August 30, 2007 Any nearfield plots? Quote Link to comment Share on other sites More sharing options...
DrWho Posted August 30, 2007 Author Share Posted August 30, 2007 My friend that helped me with the project took pictures on his cell phone, but hasn't gotten them sent to me yet... I am pretty sure that the PVC in the Danley is being used as a Helmholtz resonator to knock out the 110Hz peak in the attached picture. I think it might be the result of a standing wave from the undersized mouth. The gray line in the picture is when the horn is in 1/8 space, and the black line is in 1/4 space. Relative to the lower passband, it's rather annoying to have a peak shift by 6dB when you put the sub in different spots in the room. With a Helmholtz resonator, I think you can knock out that peak which would then allow one to take advantage of a wider passband...making the output up to 200Hz usable. I didn't do any optimization of the following plot, but you can get a pretty flat passband between the low frequency corner and the first huge high frequency dip. Normally, like you see in my design, the first high frequency dip happens around the frequency where that peak is sitting... Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted August 31, 2007 Share Posted August 31, 2007 drwho if you are bracing from the outside might recommend alot of wood clamps? and those nylon tie downs. Quote Link to comment Share on other sites More sharing options...
TheEAR Posted August 31, 2007 Share Posted August 31, 2007 This is exactly the kind of project that would use multi ply Baltic birch sheets,and braced to the grills. Using clamping and a liberal amount of screws in the critical places you would have a dead cabinet. Baltic birch compared to even high quality standard plywood makes a major difference. One feels like a hollow chipboard and the Baltic birch like a MDF material but even more solid. The great thing about these horns,use one 12" woofer with descent displacement and you can get huge output out of an inexpensive driver with no more than 15mm Xmax. This of course if you have a driver designed for the task in its optimal box/horn loading. Post pics,would be great to see the beast. Quote Link to comment Share on other sites More sharing options...
darkside Posted September 6, 2007 Share Posted September 6, 2007 I have no doubt in the solidity of varying materials, but I've beentold they make almost no difference in sound quality, though I stilldon't understand how fiberglass is a viable material, but whatever..... Any pics yet Doc? Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted September 6, 2007 Share Posted September 6, 2007 its airtight and lightweight, good for cars Quote Link to comment Share on other sites More sharing options...
darkside Posted September 6, 2007 Share Posted September 6, 2007 Yeah, but wouldn't it flex under high SPLs? In a car it's usually thin and flexible so wouldn't it have a certain point at which it physically vibrates? Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted September 6, 2007 Share Posted September 6, 2007 rather than bracing, can you use conduit w/ all thread and tie the sides together, like the laScala mod ..? Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted September 6, 2007 Share Posted September 6, 2007 it vibrates but most car speakers have them set or braced against something else, like the carpet of the trunk. Quote Link to comment Share on other sites More sharing options...
TheEAR Posted September 8, 2007 Share Posted September 8, 2007 Dr WHO can you take a pic of your sub,I want to see the gorgeous rosewood finish with bird eye maple inserts....[] Come on...show us your monster horn sub... Quote Link to comment Share on other sites More sharing options...
darkside Posted September 8, 2007 Share Posted September 8, 2007 Ear just wants to criticise your carpentry skills because none of us are at his level of cabinet making....or sarcasm [:#] Quote Link to comment Share on other sites More sharing options...
TheEAR Posted September 8, 2007 Share Posted September 8, 2007 Sarcasm...Jacksonbart is the master. Just check his posts in the Pro...meeeedia section when people say "My third set blew up" Jacksonbart responds..."Stop using the 240V jack !" LOL The world of sarcasm is a grand world. Quote Link to comment Share on other sites More sharing options...
darkside Posted September 8, 2007 Share Posted September 8, 2007 Hmmm definitely [:#] for me now[:S] Quote Link to comment Share on other sites More sharing options...
DrWho Posted September 8, 2007 Author Share Posted September 8, 2007 I seem to recall a certain someone defending himself a while back about not having a digital camera... *cough* theear *cough* *cough* [][][] I have had yet another friend swing by and take pictures who is yet to send them to me so I can post them. How lame is that? But really, there's not that much to see....it's just a small wooden box sitting in the corner of my room. It's annoying really because I need to tear it apart anyway and brace the crap outta everything. I considered doing the threaded rod through the enclosure, but a tapped horn needs to be folded which means I would need to go through 3 panels of wood - none of which are parallel to each other. I simply don't have a drill bit that is 20" long. (Do they even exist?) For what it's worth, I actually built this horn with the intention of throwing it away! [] After all this research on tapped horns, I've dreamt up a few ways that I might improve upon the design. But before I can improve on something, I first need to establish a starting ground to make sure I can do at least the basic tapped horn correctly. The only downside to all this is that the nature of intellectual property prevents me from making any of these details public. I think that's even more lame than my friends with cameras that might as well just not have cameras... But just to brag a little bit....I have found that 23Hz doesn't trigger any of the resonances in the sub, which means I can crank that frequency as loud as my drivers can handle.....which results in over 130dB at the listening position [H] Quote Link to comment Share on other sites More sharing options...
darkside Posted September 8, 2007 Share Posted September 8, 2007 Wow.....don't hurt yourself there Doc. Quote Link to comment Share on other sites More sharing options...
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