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| Challenge | Requirements | Supplies | Promotion | Subwoofer | Photos | Reviews | ASP | FAQ | Revision 0.1 | Revision 2 | ORION-3 | ORION-4 |



There are three versions of the ORION-3 system that can be built DIY. Sonically they are essentially identical. The three versions of the ORION differ in the woofer driver selection and mechanically in the design of the bass section. The original ORION and its version 3.3 use Peerless made woofers. Newer SEAS made woofers are employed in ORION-3.4. The same SEAS woofers are also used in ORION-3.5, but in a different mechanical configuration. ORION-3.5 is the prototype for the commercially available ORION-4.

ORION-3.3 (April 2011) culminates the ORION project, which started in 2002. The design incorporates elements from v3.2.1 and results of a project to use SEAS 10" woofers for ORION-4 in a W-frame configuration. Applied to the previous ASP design, which uses Peerless 10" XLS  woofers in H-frame configuration, the performance was brought to a similar level of excellence as in ORION-4. Upgrading to v3.3 involves component changes in the ASP. Detailed DIY information is provided to existing ORION owners for free. 

   ORION-3.4 at the Burning Amp Festival 2011

ORION-3.4 (October 2011) employs the SEAS 10" long-throw woofer L26RO4Y instead of the Peerless XLS 830452 in the same H-frame. The new woofer has a larger magnet structure and greater excursion capability than the Peerless unit. ORION-3.4 is sonically equivalent to ORION-4 from Wood Artistry. To benefit from the new woofer's increased output potential requires an amplifier with higher power capability than the 60 W/channel AT6012, such as the AT1806 with 180 W/channel. 

ORION-3.5 (October 2011) uses the new SEAS 10" woofers from v3.4, but they are mounted in a W-frame for force cancellation. This reduces cabinet vibration, which might be transmitted into the floor. Such structure borne energy could be re-radiated from the floor or walls if they are not rigid. ORION-3.5 is the DIY equivalent of ORION-4 from Wood Artistry and a challenge to build.


What is involved in building the ORION?

All three versions of the ORION can be built DIY from the documentation and blank circuit boards that Linkwitz Lab provides. A new ASP circuit board was optimized for currently available leaded capacitors and also provides a balanced input connection. The material cost for building ORION-3.x is around $3,800. Add to this the cost of about 80 hours of your time.

Complete ORION-4 Systems in different choices of wood and finish can be purchased from Wood Artistry. They also offer a complete kit of mechanical parts - and assembled and tested electronics - for you to put together and finish a production like ORION-4 System


| Challenge | Requirements | Supplies | Promotion | Subwoofer | Photos | Reviews | ASP | FAQ | Revision 0.1 | Revision 2 | ORION- 3 | ORION-4 |



Below is the product development story that led to ORION-3.2.1, before ORION-3.3


With Revision 3.1 the filter circuits in the ASP of the ORION+ loudspeaker system have been modified for a perceptually neutral frequency response, top to bottom. The result is increased resolution, spaciousness and dynamic range. The system now fully exploits Revision 2, which was the addition of the rear tweeter resulting in ORION+. Revision 0.1 was the mounting of the midrange driver by its magnet for vibration isolation.

Ever since PLUTO came about I felt challenged by its midrange presentation, which sounded more accurate to me than the ORION's. So I finally started a project to investigate my ORION equalization of 8 years ago. I had designed the speaker for a flat on-axis free-field response as measured outdoors. A flat frequency response tends to sound too bright indoors and my design procedure has been to correct this by listening to program material and then adjusting the tweeter level down until it sounded in balance with the midrange. This then became the nominal tweeter level and the center position for an adjustment potentiometer with a +/-.2.5 dB range.

For Revision 3 I re-measured the baffle mounted midrange driver without 120 Hz and 1.4 kHz crossover filters, but with 400 Hz and 5 kHz notch filters and dipole equalization applied.  I noted the non-flat response above 500 Hz. Correction required a good amount of computer simulation and measurement to arrive at a realizable and satisfactory response curve. The graphs below show the measured acoustic free-field response, on-axis for the midrange driver on the left and the associated driver terminal voltage on the right. The 120 Hz and 1.4 kHz LR4 crossover filters were not engaged.

Measured acoustic free-field response, on-axis of the midrange

Midrange driver terminal voltages (6 dB gain offsets in both graphs)

The midrange to tweeter transition region from 700 Hz to 3 kHz for the 1.4 kHz LR4 crossover was now level with the frequency regions below and above for a flat overall response. Extensive listening tests with known program material that I and Don Barringer (on the East Coast) performed with our modified Orions pointed to about the right level setting for the tweeter, but were otherwise not quite on the mark. When analyzing the theoretical shape of the frequency response curve it seemed obvious that the transition from midrange to tweeter was too steep. We therefore left the tweeter at its flat level setting and started to use shelving lowpass filters to shape the response. Immediately we found great improvement, but it took us many hours of listening to arrive at the -1.7 dB filter, centered at 4.4 kHz and with corner frequencies of 4.0 kHz and 4.9 kHz. Slight changes in center frequency and/or filter attenuation caused disproportionate perceptual changes from dull to hi-fi. Consequently the tweeter level adjustment range has been reduced to +/-1 dB to account for tweeter tolerances, room and personal preferences. 

Change of frequency response with tweeter level adjustment

Response of shelving lowpass filter with tweeter level set to zero (green) and to +/-1 dB 

So now the speaker sounds wonderful - in the literal sense of the word - but why is a flat free-field response not perceived as such in a reverberant environment? It might be related to the multitude of reflections that a speaker like the ORION+ generates with its rear tweeter and wider than dipole-like dispersion in the 1.4 kHz to 4 kHz range. Our hearing sensitivity is different for a frontal sound field compared to a diffuse sound field, where sounds arrive randomly from all angles at the ears. The graph below shows that from 4 kHz to 14 kHz we are more sensitive to the diffuse field in the room and from 1.8 kHz to 4 kHz more sensitive to the direct sound from the loudspeakers, but this is also the region of widest dispersion for the ORION+ and least directional acuity of the ear. I have no good explanation for the desirability of a non-flat response and the particular shape we came up with. 

Furthermore I have no explanation as to why there is a significant audible difference between the two response curves below, which differ by a maximum of 0.17 dB at 5 kHz. The yellow (!) response sounds non-engaging and muted compared to the green response which is used in Revision 3. It certainly points to the importance of consistency and tight tolerances in the manufacture of tweeters in order to duplicate what we found. In two locations and with different speaker setups and environments we have come to the same conclusion about the two curves. You might check this out  after you have updated your ASP.

It makes me wonder whether we have come upon a pivot frequency and level difference that is appropriate for adding instrument harmonics to their fundamentals in the right proportions whenever the Auditory Scene is a reduced scale representation of reality. The volume control determines the scaling factor. With the volume control I set the size and distance of the Auditory Scene. What size is acceptable appears to depend upon the content of the 2 kHz to 4 kHz octave and upon distortion. The ear itself is non-linear and ear canal resonance amplification might trigger unpleasant sensations. I suspect there is some evolutionary purpose for sensing distortion. For whatever reason, the spread between what is plausible and what is artificial to my hearing has widened, both in terms of timbre and spatiality. The highest enjoyable volume level has increased significantly, but it varies between recordings. There remains an overall brightness that can easily turn into shrillness on some voices. It is not clear whether this is due to the loudspeakers, the recordings or our ears. This and the criticalness of the tweeter level adjustment is bothersome to my engineering sensibilities.

Something fundamental had to be going on and I realized it had to be related to the differences between hearing real sources, which exist physically and phantom sources, which only exist in our mind. No direct sound is coming from a phantom source to our eardrums. For stereo reproduction left and right loudspeakers are ideally at +/-30 degree angles. The literature about Head-Related-Transfer-Functions and center loudspeaker versus phantom center gave me  me a clue. We have increasing sensitivity to high frequencies when the real source is at a 30 degree angle, than when it is in front of us. The exact relationship is complicated but there is a broad trend to the sensitivity increase with a slope in the order of 2 dB/decade to 3 dB/decade. Thus a phantom center that is generated by flat left and right loudspeaker signals must have too much high frequency content and should sound bright. A shrill soprano will sound even more shrill when reproduced as a phantom center because the actual sound arrives from left and right angles. Our mind has to form the phantom from those cues at the ear drums and they will be consistent with a very shrill voice in front.

Some listening experiments using the tilt control of my Lexicon DC2 preamp told me that I was on the right track. I could hardly go to bed and sleep that night. I got up at 5 am to design and build a set of down-sloping filters. By 1 pm and after some annoying interruptions, I was ready to sit down and listen. It took less than 2 hours to settle on and check the final curve for any flaws that Don and I were familiar with when we came up with the curve above. Now, the accents were gone or in their natural place. The tonal color was right and the acoustic sizes of different instruments and voices were in right proportion to each other and their environment. It played at higher SPL with ease. The first impression may be non-descript, gray. It may take the brain a little bit to adjust to the new, less spicy diet than what Revision 3.0 was dishing out, but all the flavors are there, some more subtle and for others you will want to increase the volume. It's all in balance once woofer and tweeter levels have been adjusted properly.


The curtain has been opened. The Auditory Scene is almost tangible in its 3-dimensionality and clarity of sonic detail, localization, spaciousness and dynamism. You will probably go through your whole library again and discover sounds and nuances that you were not aware of or could not hear because it takes realistic volume levels to bring them out. 

ORION-3.1 is silent, breathes, roars and whispers. It is a new loudspeaker. 


Upgrade to ORION-3.1

Do I think that it is worthwhile for a happy and satisfied ORION+ or ORION++ owner to implement Revision 3.1? Absolutely! 

For those who assembled the electronics themselves it should not be too difficult an operation. It requires to unsolder and install 28 resistors and 12 capacitors. See your Owner-Support page for details.

For those who bought the assembled and tested crossover/equalizer from us, it becomes a less direct procedure, because Don Barringer, who builds new crossover/equalizers, cannot take on the job of upgrading. Instead it will be handled by Don Naples of Wood Artistry. See your Owner-Support page for details.

Of course any new orders for the crossover/equalizer will meet Revision 3.1 specifications.

I am amazed and pleased by how much more sonic pleasure could be gained from the original ORION platform and its drivers by changing component values on the ASP printed circuit boards. I am no longer puzzled by the need to down-slope the frequency response for stereo listening. 

In summary, Revision 3.1 corrects deviations from a flat on-axis frequency response of the ORION and then adds to the result a high frequency down-slope that makes it easier for a listener's brain to construct plausible phantom sources.



Revision 3 of the ORION is now in its 3rd implementation with Version 2. This became a necessary evolution because the frequency response of the loudspeaker can not be flat for stereo reproduction. The response has to roll down towards higher frequencies, but how? 

A further small change in the 100 Hz to 200 Hz shelving filter frequencies provides an increase in upper and lower bass output for improved overall balance and a reduction in dryness.
I believe that with Version 3.2.1 we have arrived at a clear and even presentation of phantom sources and their context.

Don Barringer, who consistently gave me feedback and inputs, was instrumental  to the acoustic development of the ORION since its beginnings. He wrote A Brief History of the ORION Revisions.


Further thoughts, observations and experiences:

- What are the on-axis and off-axis frequency response requirements for stereo loudspeakers?
- High-frequency down-shelving for ORION-3.0
- What is the optimum polar response for a loudspeaker?
- L-07 Dipole loudspeaker
- Woofer level setting
- Hearing spatial detail in stereo recordings


| Challenge | Requirements | Supplies | Promotion | Subwoofer | Photos | Reviews | ASP | FAQ | Revision 0.1 | Revision 2 | Revision 3 | Revision 4 |


CAUTION: The content of these pages may change without notice as I learn new things or find better descriptions. The designs presented here may change as I make new observations or gain more insight. I see myself as a seeker of truth, though I now know that every person is, and ultimately truth is a construct. There is only this. Maybe what has been done here points you to it. Audio has overwhelmingly been a hobby for me, for my own pleasure and love of music. I enjoy to share what I found and possibly to dispel a few misconceptions. My interest is not on the business side, though I like that my activities pay for my hobbies. You may not agree with some or all aspects of my designs, the approach that I take to them, or the theories. I have no problem with that. Just do not ask me "what would happen if ...". Changes that you make to the designs are for your own pleasure and at your own risk. But if you learn something worthwhile, then please let me know. My DIY projects are not for beginners and it may be necessary for you to buy subassemblies or a turnkey system from Wood Artistry. Please do not ask me for individual help with your DIY difficulties. All my designs have a Support Page. It is listed on the cover or inside of your project documentation. There is an ORION/PLUTO/LX521 Users Group with people who can help you. I respond to every email eventually, but you may not get the answer you want. I consider my writings in these web pages as brief and to the point. I labor over every sentence and word and provide little redundancy. Read thoroughly and maybe more than once. I do not write for the rank beginner, but for those who have been around the block. You may need to study up. The links in my text are for that. I have not been standing still since I started this website in 1999 and with the idea of a brain dump of my previous findings so they would not get lost to the audio community. In 2006, after PLUTO, I thought I would go into a support and maintenance mode. No new design. Stuff happened, more enjoyment to share. The recording and rendering process interests me most at this time. Therefore the LX521. Let's see what it will do.  I could stop now and be content with what has been accomplished.    



What you hear is not the air pressure variation in itself 
but what has drawn your attention
in the streams of superimposed air pressure variations 
at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space
Have they been recorded and rendered sensibly?

Last revised: 02/15/2023   -  1999-2019 LINKWITZ LAB, All Rights Reserved