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Zilch's AK Design Collaborative - Econowave Speaker

Schumacher ® said:
The waveguide imparts a 1st order rising response on the tweeter, well defined and very uniform over the range from 1500Hz on up. Below that, the tweeter/waveguide rolls off. A 1st order filter complements the natural rising response perfectly, flattening the system response with diminishing distortion levels as frequency goes down.

The two resistor L-pad reduces the impedance variation even further, allowing the single capacitor to do the job without peaking in the transfer function at resonance.

I'm sure someone could add some compensation/EQ to the XO to tame some of what is left to the response variance, but to what end really? This tweeter/waveguide sure does have an overall smoothness to it, staying within a dB or so around reference.
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Outstanding. As Einstein said, "Everything should be as simple as possible, but no simpler".............Great job, I am impressed!:yes:

Russellc
 
juniorJBL said:
Not bad considering well regarded 6" 2-way's start at about 5-$600 a pair.
These should walk all over them!:thmbsp:
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They have the answer to 600 dollar 2-ways also, the Indignia! But I hear ya!
this project is the bomb because anyone evn half way handy can build a very impressive speaker for so little money.:thmbsp:

Russellc
 
donprice said:
We can always call it the pWave instead of eWave. P for premium. Or u for ultimate.

The eWave bang for buck is impressive.

It might be a little while before I swap out the eWaves for the pWaves. Shocking that I'm thinking upgrade when the originals are only 6 weeks old.
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What's even more shocking is that it doesnt end there either! But what fun it is!

Russellc
 
Quite impressive.

The new 5 part crossover is very impressive. If my B&C systems in the trapezoid cabinets were here, I would give it a go, but unfortunately, they are at work. And I have been at home for several days with several more to go while we get the storm damage caused by our leaking Pella windows fixed.

Anyway, extremely nice job. :thmbsp:
 
skywave-rider said:
It's true the bump though only a few dB is in the most sensitive hearing range. I think the problem is that changing the component(s) will shift the forward axis. I still wonder why not use a zobel to take down the spike a the top of the woofer's response, thereby leaving a smoother slope to sum and work with.

Having been a DE250/QSC user for a while I can tell you that if you move around while listening, a few dB bump in the mid-range is moot, because the nulls loom nearby and the response in that region will vary. Nothing will change that given the x-o frequency/spacing.

And in spite of that, it sounds good.
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the resonance of the Kappalite at 2KHz can't really be dealt with using a zobel. It's too narrow a peak. I'm sure that off axis, that peakiness goes away somewhat due to the limited directivity of the woofer at 2KHz. Even so, on axis, the variance over the range is around +- 1dB which is quite good.

For a purist, a LCR trap could be added, increasing the complexity, but reducing the peak at 2KHz. Believe me, I tried varying all the component values, and if you reduce the peak, the cutoff region sinks too much. The trap is the only way I can think of to do it without screwing up the phase/lobing. Raising the inductor, increasing the cap, causes more problems than it solves, and that's because the tweeter slope is predetermined and the woofer is forced to merge with it.

The UWave using the Lambda TD12 wouldn't have that problem as it's response is a bit smoother and more extended. I played with some modeling on it, and you can't get away with a simple LC filter. 3rd order minimum to get a good phase match to the QSC.

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Question for Zilch

If you saw Zaph's blog about waveguide loading the SB Acoustics SB29RDC, the ring radiator seems to have an affinity for a large waveguide, with commendable results.

http://www.zaphaudio.com/blog.html

This tweeter has a sensitivity in the low 90s, plenty to act as the tweeter in the Ewave. If I sent you a pair, would you load them into the QSC and see if they perform as well? Talk about a cheap alternative for the lower sensitivity Ewaves. And they do have good non linear performance as well, which will only be improved by the waveguide loading.

SB29RDCN-C000-4-PE10waveguide-front.jpg


0-15-30-45-60 degrees

SB29RDCN-C000-4-PE10waveguide-0-15-30-45-60.gif


With 5.6uF series capacitor, 15 deg off axis.

SB29RDCN-C000-4-PE10waveguide-15deg-5.6cap.gif


Non-waveguide distortion. Levels at 2KHz would be down another 12dB with the crossover action factored in.

SBAcoustics_SB29RDCN-C000-4-HD.gif
 
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jackgiff said:
The new 5 part crossover is very impressive. If my B&C systems in the trapezoid cabinets were here, I would give it a go, but unfortunately, they are at work.
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I'd be very interested to know if this crossover works with the B&C woofer as well. I do recall (haven't looked it up yet, tho,) that you got a good result with no HF comp cap. It seemed technically anomalous to me at the time, but you have been proven right once again.... :yes:

If I may comment on the horizontal polars in Pete's post above: I am very pleased by how the woofer and waveguide directivities track each other off axis. Wayne told us that's how it would be if we got it right, and it certainly seems as if we did.... :thmbsp:
 
Schumacher ® said:
If you saw Zaph's blog about waveguide loading the SB Acoustics SB29RDC, the ring radiator seems to have an affinity for a large waveguide, with commendable results.
Click to expand...
As one might surmise from my posts on the Tech Talk forum, I am somewhat of a student of mating conventional tweeters to waveguides. Frankly, I believe RCW has a better handle on it than Zaph, with a better result. See Part 3 here, particularly:

http://sound.westhost.com/articles/waveguides1.htm

RCW hangs on the DIY Audio forum, where waveguides are a matter of significant interest and several members have made prototypes and posted results. Geddes suggests that the quasi-spherical source wavefront is not a good match for commercial waveguide profiles designed to work optimally with the planar wavefront of compression drivers. In this context, I believe he suggests that ring radiators are the best hope. RCW seems more focused on ascertaining a profile which does mate with tweeter wavefronts.

In any case, experimenting with available waveguides requires sacrificing them to one extent or another. Although the MCM waveguide is inexpensive, I don't believe Zaph's results exhibit as successful an outcome as some presume. Others are working with Dayton and QSC round waveguides, but Wayne Parham's work, as well as our own here, suggests that the objectives of low crossover frequencies and an optimum forward lobe are not easily accomplished using an axisymmetric round waveguide.

JBL has been using asymmetric (elliptical) waveguides with dome tweeters for 20 years in there TOTL studio monitors and consumer products, and I have posted pics of their successful pro oblate spheroid assembly on Tech Talk:

http://techtalk.parts-express.com/showthread.php?p=1616506#post1616506

While it's unlikely that Geddes will ever admit that Wayne is right, he is pursuing an elliptical design for use with compression drivers, as well. A cursory review of his work reveals ellipticals among his own earlierst OS designs. For my own part, that's the avenue I would be pursuing, and there are several others over on DIY Audio doing exactly that.

Of note:

1) There is an inexpensive (10"?) round QSC waveguide available some are using experimentally.

2) I look with considerable favor upon the rising response of the new DC28F dome silkie as a candidate driver; there's energy there just begging to be spread around.

3) I've heard the DXT and have some. Do we believe diffraction to comprise the optimum means of accomplishing this objective?
 
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Zilch said:
As one might surmise from my posts on the Tech Talk forum, I am somewhat of a student of mating conventional tweeters to waveguides. Frankly, I believe RCW has a better handle on it than Zaph, with a better result. See Part 3 here, particularly:

http://sound.westhost.com/articles/waveguides1.htm

RCW hangs on the DIY Audio forum, where waveguides are a matter of significant interest and several members have made prototypes and posted results. Geddes suggests that the quasi-spherical source wavefront is not a good match for commercial waveguide profiles designed to work optimally with the planar wavefront of compression drivers. In this context, I believe he suggests that ring radiators are the best hope. RCW seems more focused on ascertaining a profile which does mate with tweeter wavefronts.

In any case, experimenting with available waveguides requires sacrificing them to one extent or another. Although the MCM waveguide is inexpensive, I don't believe Zaph's results exhibit as successful an outcome as some presume. Others are working with Dayton and QSC round waveguides, but Wayne Parham's work, as well as our own here, suggests that the objectives of low crossover frequencies and an optimum forward lobe are not easily accomplished using an axisymmetric round waveguide.

JBL has been using asymmetric (elliptical) waveguides with dome tweeters for 20 years in there TOTL studio monitors and consumer products, and I have posted pics of their successful pro oblate spheroid assembly on Tech Talk. While it's unlikely that Geddes will ever admit that Wayne is right, he is pursuing an elliptical design for use with compression drivers, as well. A cursory review of his work reveals ellipticals among his own earlierst OS designs. For my own part, that's the avenue I would be pursuing, and there are several others over on DIY Audio doing exactly that.

Of note:

1) There is an inexpensive (10"?) round QSC waveguide available some are using experimentally.

2) I look with considerable favor upon the rising response of the new DC28F dome silkie as a candidate driver; there's energy there just begging to be spread around.

3) I've heard the DXT and have some. Do we believe diffraction to comprise the optimum means of accomplishing this objective?
Click to expand...

What I was wondering, is if the QSC waveguide could be modified to host the SB29, as it is the waveguide of choice for the Econowave. And as you noted, the ring radiator seems to have the wavefront shape that works with a waveguide. but at only a fraction of the cost of the pro driver, it might make an attractive alternative for a super budget E-wave design.
 
Schumacher ® said:
OH! My mistake.
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Sorry; that's why I responded to your question from more of a theoretical design perspective. Waveguides are quite inexpensive, and there's a host of capable compression drivers under $100 that can do a credible job of tweeting mated with them. That doesn't mean that conventional drivers can't do as well or better; it's constant directivity is the worthy pursuit.

RS28Fs came in today, so I may be doing some experimenting with those on ellipticals here soon.... :yes:
 
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Will the Kappalite woofer with the deluxe crossover work with the Std E-wave (DE220ti and jbl waveguide). Thus being a hybrid Econolux version.
 
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