Econowave DSP Aussie built

gainphile

gainphile

Member
Thanks to the great work of people at Econowave AK Design Collaboration :thmbsp: I can afford to try this type of speaker topology. I normally build active dipoles with budget components.

My build will consist of:

Waveguide:
DJCity YD-L033 - HORN ABS RESIN 162X303X107MM. Locally sourced in Melbourne at $20 (pair!).
They look very similar to "Econowave approved" Pyle Pro PH612 and JBL 1" thread-on Progressive Transition, Part# 338800-001.
We'll see.

Drivers:
High: Selenium D220Ti-8, a compression driver
Low: Eminence Beta 12a, 12 inch woofer

The cost of shipping the Seleniums from Partsexpress was quite high for a pair ($74) but there is no other way.
I am getting the Eminence Beta from eBay locally for $100 a pair.

Crossover:
Active, DSP-based. I already have them which has the capability for 4-way. It consists of:
2x MiniDSP Kit RevB (should've gotten RevA instead)
1x Advanced 4-way crossover software.
Hence I have spare 2 channels for my further experiment.

For a 2-way implementation, one MiniDSP Kit would've been enough ($99).

I am normally an analogue XO guy but the DSP is so transparent that I am a convert. It is a very powerful DSP board. Much more capable than DCX2496.

Amps
I have already an 8-Channel Class D Amplifier. They are from Sure Electronics and is great value for money, as in about $15 per channel. Even cheaper than gainclones and little soldering needed :thmbsp:

I am very curious on what the sonics would be, having lived with dipoles for a long time and generally shunning traditional box speakers. I don't think this is traditional at all.

I will post the DSP settings here:
http://gainphile.blogspot.com/2010/11/s15-econowave-dsp.html

S15-1.png
 
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Upon completion of that main unit, this is what I really want to find out.

The ideal and non-achievable response of a loudspeaker in a room is something like this (?)

ideal.png


Ignore "L" and "R" typos. They should have been "R" and "F" respectively.

A dipole loudspeaker response is similar to that, except that it also fires towards the back and it's very difficult if not impossible to have an even polar response in tweeter region. This is the achilles heel of typical dipole implementation like Orion.

So now we have a controlled directivity loudspeaker like Econowave and Gedlee. While the upper frequency is great, like other box speakers it becomes Omni in lower spectrum.

S15a.png



So what if I use dipole subs instead? :scratch2:

S15b.png


Better lower region. But then it also fires to the back. How sensitive are the ears responding to this? Well at least we get the clean, deep dipole sound.


Now we try Cardioid. By using monopole back to back, and delaying the rear woofer electrically we obtain cardioid radiation.

S15c2.png


Looks even closer to the ideal response. I am very curious how it will sound.

But for now... build the Econowave first ! :yes:
 
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A bass drum would be a dipole. But that's not the point in terms of small-room reproduction as the whole idea of stereo reproduction is nothing natural, it is a mechanism to fool the brain that there is a phantom source (a "soundstage"), not left-and-right speakers.

For a cave person to survive, hearing two lions from right and left should not give a phantom image of a lion in the middle!

As a reproduction device it is observed that uniform response is desired in a typical livingroom. Be it Omni, dipole, or cardioid. They illuminate the room with the same spectrum and the brain is able to ignore reflected sound.

In short, with Omni I illuminate the room fully. With dipoles its 4.8 db less to the sides with a bonus of no box storage energy. With this experiment I'm really hopefull that uniform illumination can be obtain to the FRONT only.

Hopefully, at least :scratch2:
 
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Looking forward to seeing how this one goes Andi!

One comment - I think you will find the polar responses a bit different to that. Geddes speakers for example are flat on axis, then off axis you get a lowered shelf. So the treble drops down relative to the midrange, but it's still relatively flat. The current website doesn't show it like it did previously. I think the Econowave is similar.

Just had a look at Linkwitz lab - a bit hard to find frequency response plots!
 
SL doesn't publish plots of the Orions, but there are plenty for Phoenix.

Yes my "plots" above are simplification only.

I am quite familiar with dipole plots and they are perfect up to 1khz no questions. It's 1k above and then the transition to tweeters which are worse then become awful. This is where Econowave will excel.

:)
 
We will never reproduce the same air particles with two loudspeakers in a room. Hence stereo = illusion engine.

Sound radiation is always omni when the wavelength is large compared to radiating surface. A triangle is an omnidirectional radiator although its frequency is in the khz region. That does not mean it cannot be reproduced believably with directional loudspeakers like waveguides or dipoles.
 
This will be a very interesting build, looking forward to the next steps

Didn't know http://www.minidsp.com/, thank you for pointing it out!
Especially their dsp and streamer should get more attention. :yes:
 
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Design axis

In the standard Econowave design, the design axis is mentioned:

"Forward axis = 1" or arctan 1/44 = 1.30° above midpoint between drivers w/D2500Ti-Nd. ".

Where is this exactly if I measure from the centre of the waveguide?

And is the measurement taken at 1m (I see the gating as 5ms) ?

Thanks.
 
The reference point is midway between woofer and waveguide, because, no matter which of their acoustic centers is forward or aft of the other, the system acoustic center is vertically midway between them.

I typically measure at 44", and the forward axis as defined by the maximum inverse null fell at 1" above the midpoint there. ArcTan tells me that's an upward angle of 1.30°.

Where that falls with respect to the waveguide axis depends upon the listening distance: at 88", it's going to be 2" up, and at 176" or 14'-8", 4" up, no? From the center-to-center distance between the drivers, you know how high above midpoint the waveguide axis is.... :yes:
 
Gainphile,

Looks like an interesting project. Having DSP you'll be able to set driver delays right where you want them.

One thing you may not be anticipating is that some of the Sure amplifiers can be a little noisy. Normally no problem with normal speaker efficiency, but if you are driving a 105dB efficient waveguide+compression driver directly through a blocking capacitor, any amplifier noise plays straight out unattenuated. If it becomes a problem you can just add a resistive attenuator ahead of the driver to knock its efficiency down (it will still be able to play louder than the woofer anyway).
 
Zilch said:
The reference point is midway between woofer and waveguide, because, no matter which of their acoustic centers is forward or aft of the other, the system acoustic center is vertically midway between them.

I typically measure at 44", and the forward axis as defined by the maximum inverse null fell at 1" above the midpoint there. ArcTan tells me that's an upward angle of 1.30°.

Where that falls with respect to the waveguide axis depends upon the listening distance: at 88", it's going to be 2" up, and at 176" or 14'-8", 4" up, no? From the center-to-center distance between the drivers, you know how high above midpoint the waveguide axis is.... :yes:
Click to expand...

Thanks. That makes sense. I will use your "standard" so we can compare notes later on.

:)
 
bwaslo said:
Gainphile,


One thing you may not be anticipating is that some of the Sure amplifiers can be a little noisy. Normally no problem with normal speaker efficiency, but if you are driving a 105dB efficient waveguide+compression driver directly through a blocking capacitor, any amplifier noise plays straight out unattenuated. If it becomes a problem you can just add a resistive attenuator ahead of the driver to knock its efficiency down (it will still be able to play louder than the woofer anyway).
Click to expand...

Thanks. Then the plan is to utilise L-Pad and the capacitor for waveguide hump correction. The DSP simply does the XO. I've never built a WG system so there are things to be learnt. I is a leap of faith for me.

From some reading I read that the XO points are 1.2khz LR2 for woofer and 3khz LR2 for the high. This resulted in acoustic 1.8khz LR4.


:)
 
Gainphile -

Looking forward to this, since I have spare amplifier channels available. By "waveguide hump correction" do you mean "CD compensation"?

This might be something that Zilch might ultimately be interested in as an experimenter, what with the cost of inductors and capacitors these days. - Pat
 
Econowave DSP Built !

oh3vU.jpg

Unpainted and unglued at the moment.


Design
The design is loosely based on Standard Econowave.

External dimensions
36.8cm (W) x 60.6cm(H) x 33cm (D). Sealed box.
Basically made from 33cm x 1.8cm cutouts.
Stuffed with pillow fill liberally.

Drivers
High: Selenium D220Ti-8, a screw-on compression driver
Low: Woofer: Eminence Beta 12a - 8 Ohm.

Waveguide:
DJCity YD-L033 - HORN ABS RESIN 162X303X107MM. $20.
This is similar to the Econowave Standard waveguide: JBL 1" thread-on Progressive Transition, Part# 338800-001,
or its clone: Pyle Pro PH612 (partsexpress.com) or Dayton clone

XO: Active, using MiniDSP

High:
High pass filter: 1khz LR4
Horn Notch: 1900hz, -4db, Q=1.4
Gain: -11db
Delay: 0.1ms
Tweeter protect: 68uF non-polar capacitor

Low:
Low pass filter: 1khz LR4
Driver notch 1 : 704hz, -3db, Q=3
Driver notch 2 : 1037hz, -3db, Q=6
Linkwitz transform (note: will depend on box volume & stuffing)
- measured f and Q: f=84.59, Q=0.82
- Target f and Q: f=20hz, Q=0.5. Calculated values:
a0= 1
a1= 1.994770836782980
a2= -0.994777672819971
b0= 1.004151794671880
b1= -1.994713110995730
b2= 0.990683603935339
LT graph


Global (Baffle step compensation):
Shelving low-shelf: 186hz, 6db, Q=1

MEASUREMENT

I encountered dramas with the measurement. My turntable is too small for the speakers (designed for flat dipole baffles). I could not rotate the speakers on its acoustic axis so take this with a grain of salt. I also had to normalise to 0deg. btw. it was unstable enough to fall and smash my window.

0tSKe.jpg


These Econowaves are great speakers :thmbsp:

If you're interested to hear my opinion comparing them with the Dipoles, see my post at DIYAudio.

:yes:
 
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