Zilch's AK Design Collaborative - Econowave Speaker

Hahahahah!
Or the closer the spacing, the wider the angle between nulls. (Given the same x-over frq.)

So, what did u come up with?

*sigh*

I was afraid there would be math.

I'll attempt to sum up Wayne with the fewest inaccuracies possible:

HF motor behind LF motor = pattern tilted 'upward'

driver centers farther apart = lower crossover F to achieve flat response forward.
Corrolary: higher crossover freq = closer driver spacing to keep nulls out of forward pattern.

Looking at the example given, and assuming that jackgiff's EWG crossover* meets the criteria of the example, overlapping the EWG rim over the rim of a LA woofer results in an 8" c-to-c distance and about a 50 degree arc between nulls.

* assuming the 1K2 LP and 3K HP = approx 2K1 crossover point
 
So what do we want our spacing to be on this?

In my config with a 12" woofer, I have 12" between woofer and horn centers.
About the best you could do with a 12" woofer is roughly 10" spacing basically.

I suspect the answer to that depends on the phase behavior of the crossover in the region where both drivers are working. Also, what freq can be considered the crossover freq.

Based on the assumptions of the paper Wayne pointed to, at 10" center to center and 2K1 crossover frequency you get an angle of =/- 20 degrees off of the center line before the nulls appear (40 degrees total), and that pattern will be angled upward rather than straight forward to an extent depending on how far behind the woofer the HF driver is (not much in the case of a deep woofer and our rather shallow WG).

If this gets through, I'm signing off for a while until the server traffic clears.
I signed up as a Member today to help with expenses in maintaining this site.
 
If the system design places nulls within the pattern, that's a deal breaker. If that happens, nothing else matters. You can have perfectly flat response and zero diffraction, rarefaction, reflection, distortion, no other anomalies whatsoever on the forward axis and if anti-phase nulls form at narrow vertical angles, it is a non-viable design, in my opinion.
Say it like you MEAN it, Wayne! ;)

O.K., so much for my exquisitely ill-informed response on this subject. :p:

I'll redeem myself with this:

What matters is the acoustic crossover frequency, where the drivers overlap, not the electrical filter frequencies. This will vary somewhat depending upon the woofer and lowpass filter used. E'Wave's highpass frequency is set high to compensate for part of the Seleniums' response curve.

I believe the actual acoustic frequency ended up in the 1.6 - 1.8 kHz range; check the measurements early in the thread. To get an absolute answer, I'd have to set up and measure each of these specific combinations, but I think there's a bit more leeway available.

E'Wave's vertical beamwidth is varously spec'd at 40 and 50 degrees depending where you look.... :yes:
 
So Zilch what would you say the center distance should be from Ewave to a 12" driver?
 
David picks up his speakers.

Not EconoWaves, but pretty nice speakers nevertheless. I built these for my nephew, David. He picked them up today and also took a Dynaco system to power them. Also got an Akai AP-307 turntable to play his records. He said he was very happy with everything. It was nice to do a good turn for him.

Now, back to learning CAD.
 

Attachments

  • DavidsNewSystem.jpg
    DavidsNewSystem.jpg
    58.2 KB · Views: 113
  • davidsNewSpeak.jpg
    davidsNewSpeak.jpg
    85.8 KB · Views: 109
There's a bunch of RTA in this thread showing acoustic crossover for Econowave.

I'm reading as we speak, I was thinking though if this project is to be able to be
done by those who have no speaker/little speaker knowledge or equipment then
a basic/standard spacing might be a good thing to post for all to see an adhere to.

Just thinking out loud.
 
Truly, I just popped like 3 Vicadins. (sp?)
So, I may have to check out until tomorrow.
If you can't find the RTA , I'd be happy to help you find everything then.
If u find it, look for the frequency notch when the phase of either driver is reversed. That's your acoustical crossover point. :D

I think you are referring to me:
...those who have no speaker/little speaker knowledge or equipment...

Just thinking out loud.
 
I got that the accoustic xover is basically 1.6K, but what I want the spacing to be?
No clue, it seemed from reading Waynes posts that there could be a spacing of the
drivers to close that causes issues and a spacing to far apart but I'm not sure here.

So really if we have this 1.6k accoustic xover is there a definative spacing we want?
And if so can we post what that might be for all to see?

Mine is pretty much set at 12", not much I can do about it, but for future reference.
 
I got that the accoustic xover is basically 1.6K, but what I want the spacing to be?
No clue, it seemed from reading Waynes posts that there could be a spacing of the
drivers to close that causes issues and a spacing to far apart but I'm not sure here.

So really if we have this 1.6k accoustic xover is there a definative spacing we want?
And if so can we post what that might be for all to see?

Mine is pretty much set at 12", not much I can do about it, but for future reference.

Keg;
Just spitballing here, but looking at the example in the reference paper, they used (IIRC) 16" and 1khz to achieve an angle of 50 degrees, safely outside the horn's vertical dispersion pattern. 1600 hz and 10 inches should achieve the same 50 degree angle. 12 inches should be a little narrower but I can't figure arcsin in my head after 3 beers. Or ever, actually. I would think you're still in good shape at 12 inches but care should be taken with orienting the drivers WRT the listening position to avoid the nulls.
 
Thanks Ross,

From what little I can understand of it (and not much time right now to try) I figured I
was pretty close but was confused on some of the stuff Wayne was explaining I wasn't
to sure if there was a to close and a to far distance to achieve this 50 degrees and if so
what should we shoot for as a to high and to low so we have the "wiggle" room figured out.
 
Thanks Ross,

From what little I can understand of it (and not much time right now to try) I figured I
was pretty close but was confused on some of the stuff Wayne was explaining I wasn't
to sure if there was a to close and a to far distance to achieve this 50 degrees and if so
what should we shoot for as a to high and to low so we have the "wiggle" room figured out.

Well from what I can tell there's a point of diminishing return. As long as the distance is close enough to push the nulls outside the horn's normal pattern there's no point in driving them farther out as there's no acoustic output for them to affect at wider angles.

The ultimate solution to the issue we're discussing is zero center to center distance which is a coaxial design. In that configuration the nulls we're discussing disappear entirely because the path length is the same for all frequencies and angles.

Coaxials are a whole different wormcan, however.
 
On another note how about port placement/arangement?

I know you want a wide enough port to minimize/no chuffing.

I believe you want the port farther away from the woofer verse closer.

How about rear porting verse front porting, if in the rear you can tune the bass quite a
bit by moving closer to a rear boundary and at the frequencies this woofer will produce
you don't want to hear them eminating from the port so a rear port will help that as well.

Is there a plus or minus that truly does make 1 preferred over the other on this type setup?
 
Keg;
Just spitballing here, but looking at the example in the reference paper, they used (IIRC) 16" and 1khz to achieve an angle of 50 degrees, safely outside the horn's vertical dispersion pattern. 1600 hz and 10 inches should achieve the same 50 degree angle. 12 inches should be a little narrower but I can't figure arcsin in my head after 3 beers. Or ever, actually. I would think you're still in good shape at 12 inches but care should be taken with orienting the drivers WRT the listening position to avoid the nulls.

Yeah, 12" will give you 41 degrees, which looks good.
 
Back
Top Bottom