I had been intrigued by constant directivity loudspeaker topology since reading rave reviews of Geddes speakers (gedlee.com). The cost of building one, however prevented me to have a go. Soon I found out that Zilch and his mates at audiokarma had been measuring impressive commercial waveguides available to the public. This had opened new possibilities.
I have since incorporated the waveguides to my dipoles with somewhat success. Then I also read a rather disturbing find when a group of listeners preferred a Behringer over the Orions which I look up to. The Behringers are in the same school of thought with CD design. Lacking tools, I pulled out my fingers and built these.
Unpainted and unglued at the moment. But sealed well enough.
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.
IMPRESSIONS
I'm in an early stages of understanding these types of speakers. But they are very positive. Let me address my intial skepticm with box speakers first:
- No, these speakers don't sound "boxy".
- No, the bass does not drone as I observed with many commercial designs.
- Yes, the big 12" drivers do reproduce high frequencies fine. Very fine in fact.
Comparing to the Dipoles, these are my first impressions which may or may not change over time:
BASS
The bass is not bad. In fact I thought they are tighter and went deeper than the dipoles although both are shaped to reproduce 20hz Q=0.5. Initially I thought the midbass was missing, but then baffle step compensation fixed it. The dipoles sounds more "even". This is perhaps why the CD speakers need multisub (?).
Score: DRAW
MID-HIGH
The CD speakers reproduce mid-high flawlessly and this manifest in very realistic female vocals. The dipoles have long had issues with high frequency dispersion which is not ideal and is work in progress.
Score: CD Speakers
IMAGING
The presentation of these speakers is definitely different than dipoles. They are more "forceful" to the ears/brain and very focussed. I am not saying the imaging collapses like generic hifi speakers. They are open, but not like dipoles. This was very impressive at first but I grew tired of it over time like in a few days.
I can relate people who owns dipole listening to these types of speakers and gobsmacked by the imaging. But I really don't think it holds well over time. We'll see.
Score: Dipoles
SPL/VOLUME
Although I knew their sensitivity is ridiculously high (97+db), it is only when turning the knob that I knew the effect. They are willing to play at any level long....long .... before my ears gave up.
Comparing to dipoles, however, it is different. When the dipoles volume is turned up they don't "feel" loud but "more envelopment" rather. The CD speakers on the other hand sounds *very loud*. Again, feels like a forceful speakers. I don't know if it is due to pressure source vs. velocity source nature of both speakers.With the same level of comfort, I actually listen to the dipoles louder.
Score: Unsure (CD speakers if mere SPL is the concern)
Not a straight "These speakers are better than those" it seems. The CD speakers are great speakers in a lot of ways and are cheaper to build than the dipoles. But they may be tiring to listen to over time. If I have Home Theatre (which I don't) then these are the speakers which I would choose. These would be the speakers to impress friends.
The dipoles, on the other hand, are very neutral speakers to listen to music to. The mid-high transition needs to be fixed somehow to be on par with the CD. The dipoles would be the speakers to choose for long term listening, which I do (generally 3-4 hours of listening every day).
I will report in a few weeks time should my opinion change. If you have experience with both types of speakers please do post your opinion

I have since incorporated the waveguides to my dipoles with somewhat success. Then I also read a rather disturbing find when a group of listeners preferred a Behringer over the Orions which I look up to. The Behringers are in the same school of thought with CD design. Lacking tools, I pulled out my fingers and built these.

Unpainted and unglued at the moment. But sealed well enough.
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.
IMPRESSIONS
I'm in an early stages of understanding these types of speakers. But they are very positive. Let me address my intial skepticm with box speakers first:
- No, these speakers don't sound "boxy".
- No, the bass does not drone as I observed with many commercial designs.
- Yes, the big 12" drivers do reproduce high frequencies fine. Very fine in fact.
Comparing to the Dipoles, these are my first impressions which may or may not change over time:
BASS
The bass is not bad. In fact I thought they are tighter and went deeper than the dipoles although both are shaped to reproduce 20hz Q=0.5. Initially I thought the midbass was missing, but then baffle step compensation fixed it. The dipoles sounds more "even". This is perhaps why the CD speakers need multisub (?).
Score: DRAW
MID-HIGH
The CD speakers reproduce mid-high flawlessly and this manifest in very realistic female vocals. The dipoles have long had issues with high frequency dispersion which is not ideal and is work in progress.
Score: CD Speakers
IMAGING
The presentation of these speakers is definitely different than dipoles. They are more "forceful" to the ears/brain and very focussed. I am not saying the imaging collapses like generic hifi speakers. They are open, but not like dipoles. This was very impressive at first but I grew tired of it over time like in a few days.
I can relate people who owns dipole listening to these types of speakers and gobsmacked by the imaging. But I really don't think it holds well over time. We'll see.
Score: Dipoles
SPL/VOLUME
Although I knew their sensitivity is ridiculously high (97+db), it is only when turning the knob that I knew the effect. They are willing to play at any level long....long .... before my ears gave up.
Comparing to dipoles, however, it is different. When the dipoles volume is turned up they don't "feel" loud but "more envelopment" rather. The CD speakers on the other hand sounds *very loud*. Again, feels like a forceful speakers. I don't know if it is due to pressure source vs. velocity source nature of both speakers.With the same level of comfort, I actually listen to the dipoles louder.
Score: Unsure (CD speakers if mere SPL is the concern)
Not a straight "These speakers are better than those" it seems. The CD speakers are great speakers in a lot of ways and are cheaper to build than the dipoles. But they may be tiring to listen to over time. If I have Home Theatre (which I don't) then these are the speakers which I would choose. These would be the speakers to impress friends.
The dipoles, on the other hand, are very neutral speakers to listen to music to. The mid-high transition needs to be fixed somehow to be on par with the CD. The dipoles would be the speakers to choose for long term listening, which I do (generally 3-4 hours of listening every day).
I will report in a few weeks time should my opinion change. If you have experience with both types of speakers please do post your opinion