| The AudioKarma Econo-Waveguide Speaker [message #67017] |
Tue, 12 April 2011 08:10  |
AudioFred
Messages: 377
Registered: May 2009
Location: Houston
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Illuminati (1st Degree) |
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I'm in the final completion steps of a speaker that shows great promise as a waveguide speaker for audiophiles and HT enthusiasts who are on a very limited budget. It's the AudioKarma Econo-Wavguide speaker, a design that includes a generic woofer crossover so the builder can choose his own woofer, ideally a 10" or 12". A design summary can be found here: http://www.audiokarma.org/forums/showthread.php?t=150939&highlight=econo+waveguide
AudioKarma is orientd toward vintage audio, so many builders have chosen vintage woofers ranging from highly efficient JBL and Altec drivers to relatively inefficient woofers from vintage acoustic suspension designs. I believe this design makes great use of a modern high sensitivity pro woofer such as the Eminence Delta 12LFA, which I selected for this project.
My version is a specialized design because it had to be light enough to be lifted by two people onto a speaker pole for use in my house concerts. This limited the enclosure to plywood construction and a box no bigger than two cubic feet, less than ideal for the Delta 12. If one is building this design for home audio use only I would recommend a 3.5 cu ft box, which would result in greater bass extension. The 2 cu ft box is a good size for HT use since you'll be using a 70hz hi pass filter. Home audio use for my version doesn't absolutely require as subwoofer, but one is highly desirable. If you hear this speaker with a sub you probably will not want to use it without one after that. In keeping with the economy oriented design I'm using a diy sealed sub with a 12" Dayton DVC budget driver and a buyout 150W plate amp.
Total cost of the parts for a pair of speakers, all sourced from Parts Express, is $430. This includes air core inductors, Dayton poly caps, audio quality non inductive resistors, ports, quick disconnects, woofers, compression drivers, waveguides, speaker binding posts, and driver mounting screws - everyting except the wire (which you probably already have) and the enclosures. And now for the good news: If you don't have the ability and equipment to build your own enclosures, this design will fit in the PE 1.6 cu ft flat pack trapezoidal enclosures (#245-324) which sell for $69/ea. The woofer hole is pre cut, so all you need to do with a skilsaw is to cut the port openings and rectangular openings for the tweeter and speaker binding posts.
Here's a picture of an unfinished speaker. I'll be posting details later.
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| Re: The AudioKarma Econo-Waveguide Speaker [message #67019 is a reply to message #67017] |
Tue, 12 April 2011 09:50  |
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Wayne Parham
Messages: 18787
Registered: January 2001
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Illuminati (33rd Degree) |
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Looks good, Fred. I spoke with Evan from time to time and we regularly exchanged emails, so I was sad to hear of his passing.
You know, the Econowave was inspired by my three π / four π matched-directivity loudspeakers. It shares the same design concepts, and even uses my crossover. I was pretty regular on the Econowave thread when it was being developed, since they had chosen to use my crossover topology and because there was so much overlap in design approaches. I helped them understand the way to steer the position of the forward lobe and vertical nulls with crossover slope and driver spacing.
The whole Econowave thing reminds me very much of the early days of the Pi Speakers forum. Ten years ago, I had a lot more time to kick around new drivers, mods and things like that. We used a lot of different drivers and even a handful of different horns. So there was a lot of activity and various directions that people went in. Eventuallly things sort of gelled into a smaller number of highly optimized designs, which are more refined but less DIY-tinker-able. I see this as an evolution path for the Ewave guys too. It has already started going that way, in fact.
Please keep us posed with your progress. I think you'll find a lot in common with the three π loudspeaker. The only real difference is in the drivers you choose. I really like it, and think it is an excellent design. I guess that goes without saying, but there, I said it anyway. 
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| Re: The AudioKarma Econo-Waveguide Speaker [message #67184 is a reply to message #67029] |
Sat, 23 April 2011 07:55 |
Duke
Messages: 297
Registered: May 2009
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Grand Master |
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Looks great, Fred! Very nice job.
I stumbled across that horn on the Parts Express website while researching a bass guitar cab project. The first time I ran a suite of measurements, I thought there was something wrong with my setup. The polars looked too good to be true, so I ran the data again. Nope, it's really that good. Not perfect, but certainly work-with-able (which was not the case for most of the horns I measured). I now use it in most of my speakers.
The horn body itself is a bit resonant and "plasticky" sounding, so I stick some Dynamat to the backside, and that cures it. I also use a bit of blue loc-tite on the threads, just in case it wants to wobble loose from the vibrations. Maybe all of this is covered in the AudioKarma megathread, I dunno; only glanced at a few pages of it.
Again this year I'll be showing a speaker that is conceptually pretty much identical to the 3Pi and Zilch's Econowave. Gee, so much for originality (though mine isn't a deliberate copy). Okay maybe my angley enclosure is original (well, except that NHT did it long before me).
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