oohms Posted September 3, 2017 Posted September 3, 2017 I have always been intrigued by horns, especially in the way they control directivity and reduce the influence of a bad listening room - constant directivity horns in particular. The K402 seems to be the widely regarded pinnacle of CD horns, and going by images of them, fairly simple in design. The only problem is that there are no drawings out there of them, so for me to replicate them to any degree, i would have to scour the net for every bit of information I can find and re-create the best estimation of them that I can. My philosophy is "close enough, where it matters" so I am not after a millimeter perfect copy, but one that is fairly close Some fact finding and guessing based on images reveals that they are: 1002x648x422 WxHxD in mm with flanges of roughly 64 L/R and 57mm T/B (measured by others on the net) Modified tractrix, that I take to be a tractrix starting from the mouth and finishing when the tractrix line intersects with the throat, then that straight line continues to the 2 inch driver opening in the throat - without a change in angle to interface with the compression driver The modified tractrix curve goes for roughly a third of the path length of the horn on the vertical sides, with the straight/tractrix boundary at the same point for both horizontal and vertical sections This led me to come up with a solution using trial and error in CAD, first defining the horn dimensions, then using a tractrix curve spreadsheet to make curves at different frequencies until i found a solution that satisfied the conditions above (I decided not to include flanges in my version) The curved section would be the hardest to build, and i decided to make them out of expanded polystyrene (XPS) foam, cut with a hot wire cutter, similar to what model aircraft builders do to test aerofoils Templates were made, designed to glue onto 16mm MDF of the straight sections: Next, I used the synergy spreadsheet to lazily come up with a cutting list for the straight sided panels - using trial and error to come up with values that would produce a horn of the right size (we are not interested in the secondary expansion) The green values are the put in, the rest are calculated by the spreadsheet Next mitre angles and butt joint angles are calculated using http://jansson.us/jcompound.html I decided to use butt joints with biscuits to line it all up as well as i could A quick test with the compression drivers The wooden blocks are for screwing the compression driver mounting plate onto. In hindsight, I should have glued on longer pieces and flush cut them for a better look Then, it was off to building a foam cutting rig using spring loaded nichrome wire and a 12v power supply - cutting 50mm XPS from bunnings The foam is cut using the blade tilt angle and mitre angle from the website above Glued on to the MDF with polyurethane glue. This cures with moisture, so I made sure to spray both faces with a water bottle and weighed it down as much as I could as the glue expands on drying (Almost like expanding foam) After this, I decided to cover the flat faces of the XPS with 3mm MDF (again, glued with polyurethane and weighted down), to protect and provide better defined edges and corners and to have a smoother and easier to paint surface. Then it was filling time - trialling different fillers from bunnings and to my luck, they all stuck to the sanded XPS. Giving them a test run at a party Then it was on to painting them with an undercoat/sealer, fine filling and sealer again 2 layers of semi gloss black external paint nicely finishes the horns. You can use any kind of paint for these - the flat white finish of the undercoat looked very nice with the flat finish hiding imperfections The back plate was made out of 3mm aluminium, a 2 inch (51mm) hole saw and extra holes for mounting Compression drivers are P.Audio BM-D750 MKII - they seem to be the best value locally obtainable 2 inch drivers from what I could gather Here is the final setup, perched on top of a pair of carpet covered Yamaha S250B 15 inch ported boxes I scored at a bargain - the inspiration for me to start this project How do they sound? Great!! - fantastic imaging, very dynamic. They really do cover the whole room in wonderful sound, and if you sit in the 'sweet spot' they image better than anything I have ever heard. The room has terrible acoustics and is probably too narrow to get the best out of these, but I am not dissapointed Here is a quick youtube recording of the setup, recorded with a Zoom H1 16 2
oohms Posted September 3, 2017 Author Posted September 3, 2017 Driving this setup is a MiniDSP 2x4 integrated into an old sony 5.1 receiver. It is simply connected to the "5.1" inputs internally and fed with power from the unit to reduce external clutter. This is by far the easiest way to run a DSP powered setup while keeping a sensible gain structure and not exposing power amplifiers to potential full line level input. 5
Guest rmpfyf Posted September 3, 2017 Posted September 3, 2017 Nice work! Great audio fun on a budget.
kodomo Posted October 31, 2017 Posted October 31, 2017 you can probably try the two way synergy concept with these. You have the part to hold the woofers in wood. Have you seen that project? It was documented in Klipsch forums and on diyaudio I guess. It was called a 2 way meh. Two 15" woofers and 2" cd on a k402. One of those project I wanted to try. If you can share the plans for your 402 replica, that would be great!
kodomo Posted October 31, 2017 Posted October 31, 2017 Here is that link: https://community.klipsch.com/index.php?/topic/161404-a-k-402-based-full-range-multiple-entry-horn/& and I forgot to say in my last post. Congrats for both the result and the way you did it! Great way to solve problems, enjoyed reading it a lot.
oohms Posted October 31, 2017 Author Posted October 31, 2017 I'm glad you enjoyed it. I have had my eyes on the 'syntripp' project as something to do in the future, using JBL 2453h-sl tweeters - I think it's a good tradeoff between being easier to build and it sounding close enough to the K402 that i'd be satisfied. http://www.diyaudio.com/forums/multi-way/264485-syntripp-2-2-virtual-single-source-horn.html Using foam is probably something i'd change, as it is too difficult to get the perfect finish and it is kind of fragile, even after I finished them
Full Range Posted October 31, 2017 Posted October 31, 2017 Well done What cabinet design is on the bass bin also sensitivity & Htz rating / size of driver
oohms Posted October 31, 2017 Author Posted October 31, 2017 5 hours ago, Full Range said: Well done What cabinet design is on the bass bin also sensitivity & Htz rating / size of driver It's a Yamaha S250B cabinet that somebody carpeted, so 15 inch ported, i'm guessing 100L and 95db/w sensitive (maybe less) and from memory goes down to 35hz in room
Full Range Posted October 31, 2017 Posted October 31, 2017 Should be a good match Definitely need fast and sensitive bass to match the horn
Guest Posted November 1, 2017 Posted November 1, 2017 @Upfront Check this bloke out, wow, what a great DIY horn. To the Maker, well done Mate great work would be excellent
Upfront Posted November 1, 2017 Posted November 1, 2017 [mention=111049]Upfront[/mention] Check this bloke out, wow, what a great DIY horn. To the Maker, well done Mate great work would be excellent Always watching mate [emoji6]@oohms what do you think of the drivers now you've lived with them for a bit?
oohms Posted November 2, 2017 Author Posted November 2, 2017 15 hours ago, Upfront said: Always watching mate @oohms what do you think of the drivers now you've lived with them for a bit? Funnily enough i sold the whole setup to a mate.. he loves it (and i love to visit for listening sessions) The drivers are great for the price.. there is a fair bit of breakup at 15khz but you can EQ it out. If i was to choose another driver, it would be the JBL 2453h-sl 2
Upfront Posted November 2, 2017 Posted November 2, 2017 Funnily enough i sold the whole setup to a mate.. he loves it (and i love to visit for listening sessions) The drivers are great for the price.. there is a fair bit of breakup at 15khz but you can EQ it out. If i was to choose another driver, it would be the JBL 2453h-sl So what are you making now!?!
oohms Posted November 4, 2017 Author Posted November 4, 2017 On 03/11/2017 at 6:00 AM, Upfront said: On 02/11/2017 at 9:39 PM, oohms said: Funnily enough i sold the whole setup to a mate.. he loves it (and i love to visit for listening sessions) The drivers are great for the price.. there is a fair bit of breakup at 15khz but you can EQ it out. If i was to choose another driver, it would be the JBL 2453h-sl So what are you making now!?! I'm taking a break for a little while, but looking at finishing the crossovers for the large 3 ways you can see in some of the photos above.. then maybe a pair of TC9 line arrays or a pair of syntripp unity horns 1
Pia Posted November 9, 2017 Posted November 9, 2017 Would it be possible to get a measured model of the 2 templates you made?
oohms Posted November 9, 2017 Author Posted November 9, 2017 2 hours ago, Pia said: Would it be possible to get a measured model of the 2 templates you made? I'm a bit hesitant to release any CAD files or accurate plans for these as Klipsch seem to have a very fine line between amateurs like us building one off copies for ourselves and people building them easily and/or for profit. This writeup is more about the methodology and some techniques and examples that people can use to make their own speakers/horns/etc. If you are OK at image manipulation software, the notch in the templates should be 16mm deep and the thickness at the thickest point should be 50mm
NBPk402 Posted January 25, 2019 Posted January 25, 2019 Great work! I do not think that Klipsch would do anything as long as you were not making a profit off it. There are lots of plans floating around for the Khorns, La Scalas, and Belles, and they are even in their own forum.
oohms Posted January 26, 2019 Author Posted January 26, 2019 On 25/01/2019 at 4:03 PM, ellisr63 said: Great work! I do not think that Klipsch would do anything as long as you were not making a profit off it. There are lots of plans floating around for the Khorns, La Scalas, and Belles, and they are even in their own forum. Thanks! I have moved on to other projects, and if i was to do another K402, i would improve upon its design You're more than welcome to use any information here to do with as you like
davewantsmoore Posted February 23, 2019 Posted February 23, 2019 On 05/11/2017 at 1:47 AM, oohms said: TC9 line arrays or a pair of syntripp unity horns Hah. Also my next project(s), or inspired by.
JLOP Posted March 5, 2019 Posted March 5, 2019 On 31/10/2017 at 8:09 AM, oohms said: Using foam is probably something i'd change, as it is too difficult to get the perfect finish and it is kind of fragile, even after I finished them Hi oohms I am new to to this forum an wanted to say great build. I am interested to build one but adapted to 2.4 exit of Renkus Heinz SSD5600 drivers, AND with a cutoff frequency in the 150-200 Hz, the driver is announced as going down to 250. How would you do differently than with foam ? BR Jean-Louis, from Luxembourg
davewantsmoore Posted March 5, 2019 Posted March 5, 2019 11 hours ago, JLOP said: SSD5600 Wow. Massive! Set the horn load in relation to the Fs of the driver.... not based on what low frequency extension you desire.
oohms Posted March 11, 2019 Author Posted March 11, 2019 On 05/03/2019 at 10:48 PM, JLOP said: Hi oohms I am new to to this forum an wanted to say great build. I am interested to build one but adapted to 2.4 exit of Renkus Heinz SSD5600 drivers, AND with a cutoff frequency in the 150-200 Hz, the driver is announced as going down to 250. How would you do differently than with foam ? BR Jean-Louis, from Luxembourg I would make the same foam profiles but out of something like plywood laminated together to 50mm thickness - then use the templates to route/plane the curves, but otherwise saw them etc just like the foam
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