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Zilch's AK Design Collaborative - Econowave Speaker

quote: One question I can't refrain from asking, is how do you compensate for the huge HF drop in the PSD2002? I looked at the 4 Pi specs, and it isn't there, so you must have some kind of magic to make it essentially flat. Boggles my poor mind.
I wondered this too, so I looked at the plans for the 4PI Wayne sent me. I dont show a specific crossover, I am assuming it is the 1600 hz one shown in his crossover document, with the compensation on the high end? good question.

Russellc
 
Jack,
Is that a conical waveguide I see in your photo?????
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skywave-rider said:
Jack,
Is that a conical waveguide I see in your photo?????
Click to expand...

Relax, it is a silk dome tweeter from Goldwood sound, and costs $9.70 each. I bought the Goldwood stuff cause it was cheap, and to reload these 40 year old speakers was not to make another pair of "keepers", cause they are already keepers. I simply wanted to see if a cheap pair of speakers could be made to sound good, using the principles I have learned so far. And it seems the answer will be a resounding "YES." But the project neither fits with the EconoWave thread, or the Insignia Class thread. It will just be a JackLab project for self edification. And will be most enjoyable.

The tweet will be mounted above the woofer, where it's upper reach will be limited by the overhang above it. That is, if the front baffle can be removed without destroying the cabinets. Like I said, "What the heck was I thinking?" I wanted a pair of speakers which was not just another box. The design may have been forward looking in 1964, but today the way it is built is really questionable.

As Geddes would say, "It is a diffraction horn, not a waveguide."
 
Nice work c. 1964. I think they still look great. Don't bust 'em up.

OK, RELAXING.

Wait a minute, did someone say diffraction horn?
Dirty words!
:D
 
four Pi options

Russellc said:
quote: One question I can't refrain from asking, is how do you compensate for the huge HF drop in the PSD2002? I looked at the 4 Pi specs, and it isn't there, so you must have some kind of magic to make it essentially flat. Boggles my poor mind.
I wondered this too, so I looked at the plans for the 4PI Wayne sent me. I dont show a specific crossover, I am assuming it is the 1600 hz one shown in his crossover document, with the compensation on the high end? good question.
Click to expand...

The four Pi speaker response chart was done with a JBL 2226 woofer and B&C DE250 compression driver. These are the better drivers available as options for this speaker. The other optional drivers available are the Eminence Omega 15 woofer and the PSD2002.

The PSD2002 and the B&C DE250 don't sound that much different but the DE250 is a little smoother. As you could see from my response chart, the DE250 on the H290 with the right top-octave conjugate compensation is ruler flat to just over 18kHz. It has less than 1dB ripple. The PSD2002 doesn't quite reach that high, getting up to about 16kHz and it has about 1.5dB more ripple, mostly in the form of a peak at 8.5kHz. Other than that, the amplitude response is pretty much the same and both drivers sound good.

I have some LMS measurements comparing the two drivers, but they were done indoors near some reflective surfaces so I really need to redo them. They are moderately useful as a comparison between the two, but they give the wrong impression becaue the overall shape has more ripple than what you would get in an anechoic environment. I gated the test signal, but the tweeter was just sitting on the floor and the microphone was not, so a better measurement is in order. The ones I have now are quick and dirty.

I'll make a chart of the four Pi with PSD2002 one of these days soon. It isn't quite as flat as the DE250 version around 8kHz and it rolls off a smidge sooner but still sounds very nice.
 
Thanks Wayne

Wayne,

Thanks for providing your crossover document, I've re-read it today and it is progressively sinking in. :)

Being green to speaker building, I occasionally pester designers to reveal how they approach a problem and make something work. Zilch will confirm that statement.

I have nothing to pester you with at this time, however.

I like the concept of the 4 Pi, in design, options, and look as well.

We're grateful you've weighed-in on this thread.
 
I use the $10 wavefront but with JBL 2416 that I have on hand on open baffle. Very nice indeed.
 

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Russellc, I use 1st order crossover at 1700hz simply because I have the parts on hand.

skywave-rider, as zilch said "Why, so that the imaginary diffraction slot is horizontal rather than vertical,". they sound the same to me either way; and i chose to mount them that way because they fill up the space better and look better visually. the big 15" alnico are vintage rca 9449.
 
cuthien said:
skywave-rider, as zilch said "Why, so that the imaginary diffraction slot is horizontal rather than vertical,". they sound the same to me either way; and i chose to mount them that way because they fill up the space better and look better visually. the big 15" alnico are vintage rca 9449.
Click to expand...

And by that I guess your room is long and narrow....

...yes, that illusive slot...
 
"And by that I guess your room is long and narrow...."

yes, i can get away with that setting due to my small listening room.
 
cuthien said:
Russellc, I use 1st order crossover at 1700hz simply because I have the parts on hand.

skywave-rider, as zilch said "Why, so that the imaginary diffraction slot is horizontal rather than vertical,". they sound the same to me either way; and i chose to mount them that way because they fill up the space better and look better visually. the big 15" alnico are vintage rca 9449.
Click to expand...

Boy, I dont understand enough to know what the effects of horizontal or vertical are. Seems like I remember Zilch helping a fellow member rework a smaller speaker, AR or something into a waveguide with that orientation. In that case, it wouldnt fit any other way if I remember correctly. Who was that? One of these threads. The econowave has spilled into more than one thread as well as forum! I think Zilch's comment was eluding to another's comment/post who was criticizing the inexpensive wavegu................whatever it is, I call it a wave guide because JBL does and I think they know the difference. Right? Your method sure does make box building a lot easier!

Russellc
 
The horn I used in AR2 was specifically designed for vertical orientation.

It has a 70° horizontal and vertical dispersion used that way, as I recall.

It's made by DDS for use in floor monitors.

Using EconoWave like that, you get 50° horizontal x 90° vertical, and the horizontal is somewhat less well controlled....
 
This is how we roll, our own....

Gut 'em up baby. No turnin' back. My kitchenette is my woodshop. I got MDF dust seasoning, yeah.

Re pic, I could step back no further.
:smoke:
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UT, oh....

Who let Skywave have access to power tools here? :nono:

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Ahahahahaha!:banana:
Damn we're good!

I love that.

You demonstrate a steady hand and undeniably advanced technique.
You, my friend, must have those reproduced.
You would, if you were commercially astute.
I will be your distributor.
 
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