----- Experience in your own room the magical nature of stereo sound -----

 

 

What's new

 

LX - Store

 

Conversations
with Fitz

 

OPLUG
Forum

 

Basics

The Magic in 2-Channel Sound

Issues in speaker
design

Dipole models

Active filters

Amplifiers etc

Microphone

FAQ's

Loudspeakers

Crossovers

Room acoustics

Stereo Recording and Rendering

Audio production

Conclusions

 

Projects

Your own design

LXmini

LXmini+2

LXstudio

LX521.4

LX521
reference

ORION
challenge

ORION-3.4

PLUTO-2.1

WATSON-SEL

PLUTO+
subwoofer

THOR
subwoofer

PHOENIX
dipole speaker

Three-Box active
system (1978)

Reference
earphones

Surround
sound

Loudspeaker
& Room

 

Resources

Publications

Sound recordings

Links

Other designs

My current setup

About me

Site map

 

HOME

 

------------------
Digital Photo
Processes

 

------------------
The
Sea Ranch

 

------------------
My Daughter
the Jeweler

 

What's new

 

LX - Store

 

Conversations
with Fitz

 

OPLUG
Forum

 

 

 


| Challenge | Requirements | SuppliesPromotion | Subwoofer | Photos | Reviews | ASP | FAQ | Revision 0.1 | Revision 2 | ORION-3 | ORION-4 |
ORION-5 |
| ORION-WA | ORION - EU

 

Frequently asked questions 

Q1 - Where can I hear the ORION?

Q2 - How critical is the speaker placement?

Q3 - Is there another power amplifier choice?

Q4 - How is the ORION different from the PHOENIX?

Q5 - Can I modify the cabinet for straight lines?

Q6 - Why did you not use driver XYZ?

Q7 - What should I use for a center speaker?

Q8 - Are you working on a new design?

Q9 - Is the crossover available with balanced inputs and outputs?

Q10 - What cables and interconnects do you recommend?

Q11 - Can you provide an "upgraded" crossover or "higher quality" drivers?

Q12 - The ORION has noticeable baffle vibrations. Is this a problem?

Q13 - What is the frequency response of the ORION?

Q14 - Could I use a DSP based crossover instead of the ASP?

Q15 - How does the ORION compare to speakers X and Y or Z?

Q16 - Which preamplifier do you recommend for the ORION?

Q17 - Are there areas for "tweaking" the ORION?

Q18 - Will there be a review in one of the large audiophile magazines?

Q19 - With all your claims about the superiority of dipoles why bother with PLUTO?

Q20 - What contributes to the polar response of ORION+?

Q21 - When do I need THOR subwoofers?

Q22 - Is PLUTO more appropriate for my situation than ORION?

 

-------------------------------------------------------------------------------------

 

Q1 - Where can I hear the ORION?

A1 - A number of individuals have volunteered to let you listen to the ORION that they have built. Please contact them first. If none of these volunteers lives anywhere near you, or the cost of travel for an audition becomes unreasonable, then you could try to find an ORION builder who lives closer to you and who would be willing to invite you, a stranger, into his house. But think about it like this: How many BMW owners would be interested in having you come over to test drive their new car, because you cannot decide whether to buy one or not? What is in it for them? Keep that situation in mind when you try to contact someone via the ORION Owners Forum

You could also combine a vacation in Northern California with listening to the ORION by renting the Honeymoon Cottage in Sea Ranch. And then there is the invitation that you come to my house. I live just 10 minutes north of the Golden Gate Bridge outside of San Francisco. There you could also discuss your audio questions and concerns with me, besides hearing the ORION (or PLUTO). Write to me at sl@linkwitzlab.com for an appointment. I still enjoy those demo sessions. 

Consider that when you purchase a commercial speaker in a store, you cannot escape paying for listening, for the dealer's time and his floor space, since that must be recovered by the retail price or the store goes out of business. With the ORION you have options and the cost of an airline ticket could be small compared to the value that you receive with the ORION. 

I understand your desire to hear the loudspeaker before you commit your resources to building or buying it. But even if you do not have a chance to let a listening session convince you first, I can assure you that the ORION is definitely in the very top league of loudspeakers intended for domestic use. It is for people who love music, who know what real, unamplified instruments sound like. Having heard many loudspeakers I would not know which one can surpass the Orion in its blend of overall sound accuracy, independence from the room, and integration of form and function. Ultimately though, you can only hear what is on the recording. The ORION will reveal it in all its glory, without beautification or exaggeration. Now, if your listening experience is primarily based upon listening to music through loudspeakers, rather than familiarity with un-amplified acoustic instruments and live sounds, you might not recognize accuracy immediately. In that case there might well be other speakers that you would prefer, because they have more bass, or highs, or do something else you like. Therefore listening to the ORION would be important, because there is no way for anyone to know whether the ORION matches your mental image of the ideal loudspeaker. But, if live music and acoustic sounds are your reference, then you will not go wrong by selecting the ORION, even if you cannot hear them first.   Top

 

Q2 - How critical is the speaker placement?

A2 - Basically, any dipole speaker needs breathing room around it. Even a conventional box speaker benefits greatly from as much open space around it as possible. When measured from the tweeter of the ORION, the side wall should be at least 2 ft (0.6 m) away, and the wall behind the speaker at least 4 ft (1.2 m). The side wall is not as critical as long as there is a sufficient opening for the acoustic volume flow between front and rear sides of the ORION. This then forms an acoustic pressure null towards the side wall. The wall behind the speaker should be somewhat diffusive to disperse sound that is reflected from it. In addition, the sound path from the speaker to the rear wall and reflected back to the listener is at least twice as long as the direct path from speaker to listener, so that the reflected sound level is far more than 6 dB below the direct sound. It is well below the reverberant sound level in the room to which it contributes. Furthermore, the rear reflected sound arrives at least 8 ms later than the direct sound and does not interfere with the perception of the direct sound. The rear radiation should not be absorbed, though. It is an essential contribution to the dipole polar pattern and power response. The rear radiation becomes part of the reverberant sound.  With a speaker separation of 8 ft (2.4 m), and a listening distance of 8 ft, and a 4 ft (1.2 m) minimum distance to any wall behind the listener, the minimum room size for the ORION becomes 12 ft x 16 ft (3.6 m x 4.8 m). The ORION will not live up to its full potential in rooms smaller than 180 ft2 (17 m2). Likewise, placing the speaker closer to the wall behind it will sacrifice smoothness of response, though it still provides good sound overall.  
As far as the maximum room size is concerned, there is really no limit to it, if the ORION is listened to from typical distances of 8 ft to 20 ft, consistent with speaker separations between 8 ft and 12 ft. The ORION would be misplaced in a ballroom or on a theater stage. The speaker was designed for more close up listening, though at near realistic sound levels. Top

 

Q3 - Is there another power amplifier choice?

A3 - It is important to realize that the power requirements of a fully active and open baffle loudspeaker, like the ORION, are quite different from those of a conventional box speaker. Woofer, midrange and tweeter drivers each have their own power amplifier assigned to them. The amplifier need not have any more output power than what is needed to push the driver to its full cone excursion. Any more power than that can lead to damage of the driver. I recommend the AT6012 amplifier with 60 W of power per driver, which is more than enough for the tweeter and midrange. This amount of power cannot drive the woofer to full excursion at all frequencies. Towards the lower frequencies the maximum output voltage swing limits how far the woofer cone can be driven. At the high frequency end of the woofer range the amplifier's maximum current swing sets the limit. This behavior is preferable since amplifier clipping has no permanent consequences. In practice I have not even heard it. Using a larger amplifier, like the 180 W per channel AT1806, can give up to 5 dB more useable woofer output between 30 Hz and 60 Hz. It can also drive the woofer seriously into its mechanical stops and damage it permanently. Use it at your own risk. 
Both of these amplifiers have very effective input and output protection using photo-resistors and LED light sources. When the input voltage exceeds a threshold level that would drive the output far into clipping, a photo-resistor is instantly light-activated at the amplifier input and the input signal is shut off for a preset length of time and until the input has returned to a safe level. Similarly the amplifier output stages are protected against external short circuits.

Much has been written about the sound of amplifiers in the Hi-Fi Press. Amplifiers can sound different  due to non-linear distortion which generates new spectral components. The typical total harmonic distortion specification is merely a guide post and not a complete measure of amplifier distortion. THD should be below 0.1%, as a starting point, for amplifiers not to sound different from each other. More important is the distortion at low output power levels, below 2 W,  where an amplifier spends most of its time during music reproduction, unless it is for Hard Rock. The crossover distortion of Class A/B amplifiers is impulsive in nature. It is very broadband and easily overlooked in the noise floor of the amplifier output spectrum. It registers low in a THD measurement, but the spectral components add in the time domain. They are responsible for much of the "solid-state sound". Class A amplifiers do not suffer from this inherent problem, but a well designed Class A/B can match their performance in practice.
Amplifiers can also sound different when their relatively high output impedance, or low damping factor, interacts with the combined loudspeaker and speaker cable load impedance to cause a frequency dependent drive signal at the speaker terminals. This is very much an issue with tube power amplifiers and passive crossover networks. The ORION drivers present a simple load to their amplifiers, which are essentially driving the voice coils directly. No inductors or capacitors are in the signal path. Even tube amplifiers could drive the tweeter and midrange, but the woofer presents too difficult a load to their transformer output.

The crossover/equalizer for the ORION was designed under the assumption that all power amplifiers have the same voltage gain from input to output. It is possible to add resistive attenuators at the output of the crossover/equalizers to reduce the input voltage to the power amplifier. Thus, amplifier output voltages can be reduced to equal that of the lowest gain amplifier used. The design of the two-resistor attenuators at the crossover output is up to the ORION builder. My recommendation is to use a multi-channel power amplifier or a set of identical 2-channel amplifiers.  Top

 

Q4 - How is the ORION different from the PHOENIX?

A4 - The PHOENIX is an earlier open baffle design. It consist of a main panel with two 8" midrange drivers in an MTM arrangement and two 12" woofer drivers in separate cabinets for each channel. The ORION was designed to obtain the same sound level capability from a physically smaller and visually more appealing cabinet. This had become possible because I had confirmed that a 24 dB/oct crossover could be used, instead of a 12 dB/oct crossover, between woofer and midrange without any audible effect due to increased group delay. By shifting the crossover frequency from 100 Hz to 120 Hz and using the steeper crossover filters I now needed only a single 8" driver to maintain the same output capability over the midrange. The woofer drivers had to go higher in frequency, but since they are in fixed proximity to the midrange driver there is no placement issue and I could correct electrically for the remaining acoustic offset. The MT arrangement gives a more uniform polar response in the vertical direction and the tweeter sees only one midrange cone cavity that modulates its response. In addition, new drivers had become available that measured slightly lower in non-linear distortion and stored energy and a 10" woofer driver with much more volume displacement than the 12" driver of the PHOENIX.  The sum of this made the ORION possible. I could not have designed it at the time of the PHOENIX. The finished ORION met my goal of size and output when compared to the original PHOENIX. It exceeded it in terms of driver integration, smoothness of response, clarity and overall refinement of sound. 
The PHOENIX design has since been updated with a 24 dB/oct woofer to midrange crossover and far more capable 12" woofer drivers, since the original drivers are no longer available. Consequently the output capability of the revised PHOENIX now exceeds that of the ORION. Having separate woofers, they can be easily doubled up for greater output. I did not redesign the speaker for different midrange and tweeter drivers, leaving it open to experimentation, if you wish. The ORION design is tightly constrained and should not be modified. It is complete in itself and meets its objective exceedingly well, based on my listening experience and in comparisons to other "high-end" loudspeakers. Top 

 

Q5 - Can I modify the cabinet for straight lines?

A2 - The shape of the side panels was derived from acoustic and esthetic considerations. Greater path length is needed between front and rear of the woofers, than between front and rear of the midrange driver to obtain the desired frequency response and voltage sensitivity for each of their ranges. A woofer H-frame tends to have an acoustic resonance at the high end of its frequency range. The shape of the ORION bottom side panel for the woofer is contoured primarily to avoid that resonance and secondarily to please my eyes. Its curvature then transitions into the top side panel section for the midrange. In the crossover frequency range between midrange and tweeter the on-axis and off-axis response is determined by the proper summation of three components: the front and rear radiation from the 8" driver and the radiation from the tweeter. Thus, the cabinet shape and dimensions are critical, because they affect the acoustic path length, or phase, for the summation.
Top and bottom side panels can be replaced by rectangular sections with the bottom rectangle offset forward by 1.75". The measured frequency response will be different. I guess that the audible differences will be slight, if at all noticeable, but have not tested it. The rectangle dimensions are given in the Construction Plans+
No other dimensions must be changed. In particular the width of the cabinet is acoustically critical for the polar and on-axis response. The side panel thickness may be increased from 0.75" to 1", at the most. The rear of the cabinet must remain acoustically open. Top

 

Q6 - Why did you not use driver XYZ?

A4 - One of the objectives for the ORION was to design it as a 3-way system. A 2-way system would have a restricted low frequency range or have insufficient output. A 4-way system would have added complexity and cost, yet not improved the speaker's performance for the intended application. Thus, I looked for tweeter, midrange and woofer drivers that had the necessary volume displacement, polar response in an open baffle, low stored energy, and low non-linear distortion. In addition the drivers must be available world-wide. The Peerless 10" diameter XLS woofer, 830452, has large excursion capability, very low air turbulence noise, relatively low distortion, limits safely, has very low Qts due to a strong motor, and is ruggedly built. The 8" diameter magnesium coned Seas W22EX001 Excel midrange has exceptionally low linear- and non-linear distortion over the 120 Hz to 1400 Hz frequency range used. Since the 8" driver is mounted on an open baffle of carefully designed size it has much wider dispersion at 1400 Hz than the same driver in a closed box with the same frontal baffle. I would have had to use two 6.5" drivers in a less favorable MTM arrangement to obtain the same low frequency volume displacement, yet the the narrower open baffle would have yielded little benefit in off-axis response. The 8" midrange is matched to the Seas T25CF002 Millennium 1" soft dome tweeter, which has a smooth frequency response, low stored energy, wide dispersion and can be crossed over at a low 1400 Hz through 24 dB/oct filters. The low crossover frequency is dictated by the distortion and open baffle response for the midrange driver. A ribbon driver in place of the dome tweeter would have narrower vertical dispersion, could not be crossed over as low in frequency and would be less rugged. The Millennium tweeter uses ferro-fluid in its voice coil gap for improved heat transfer to the pole piece. This reduces thermal compression from continuous high sound and amplifier power output levels which raise the voice coil temperature and thus the coil resistance. For example, a rise in coil temperature from 20 0C to 70 0C (68 0F to 158 0F) would reduce the tweeter output level by about 1.5 dB. Since the midrange driver voice coil is likely to heat too, the tonal balance would essentially remain unchanged and the insufficient increase in output level would not be noticed. 
I consider the drivers used for the ORION to be state-of-the-art. I have not seen, heard and tested drivers that would make me change them, though I keep looking for any worthwhile improvement.  Top

 

Q7 - What should I use for a center speaker?

A7 - I have no Home Theater setup. The ORION can certainly be used for a Home Theater, especially when the THOR subwoofer is added. My primary interest is music reproduction and the arrival of discrete multi-channel audio in the form of SACD and DVD-A was driving me to investigate the center channel issue. I have reported on my findings and have no pressing need for either center or surround speakers. But, PLUTO would be very suitable for such applications because its tonal balance matches closely with the ORION.
 Top 

 

Q8 - Are you working on a new design?

A8 - The ORION incorporates all I learned and know at this time, but I keep scanning the horizon for any further improvements in driver design. I consider the ORION to be a platform that could grow with any such improvements. So I am not working on a new ORION. I have no interest in developing a smaller speaker since I do not see a way to get performance that would satisfy me. I also have no interest in a larger speaker since I personally have no need for it and the ORION can already cover increased volume demands by addition of the THOR. I have pursued, though, a smaller center speaker consisting of the midrange and tweeter section of the ORION. It works well, but I do not find it necessary for my listening satisfaction. My may concern is to make the ORION accessible to a wide audience, not just to DIY enthusiasts. To this end I can offer a flat pack of wood pieces for easy cabinet assembly, partially assembled cabinets or full turn-key systems through working with Wood Artistry. You can also purchase the completely assembled crossover/equalizer and minimize your time and effort of building the ORION yourself. When cost or room size are major issues, then PLUTO would be a worthy alternative to the ORION.  Top

 

Q9 - Is the crossover available with balanced inputs and outputs?

A9 - The assembled crossover/equalizer comes with gold plated RCA Phono input and output connectors that are soldered into the ASP circuit board. It is normally connected to preamplifier and power amplifiers via unbalanced interconnects with RCA Phono-plugs. A balanced version is not available.
If you want to use balanced cables, then add the following:
1 - When driven from a balanced output preamplifier through balanced cables with XLR-male connectors, then plug two XLR-female to Phono-plug adapters, for example Neutrik NA2FPMM, into the crossover/equalizer Left and Right input connectors.
2 - When the power amplifier has balanced inputs and is driven through balanced cables with XLR-female connectors at the crossover/equalizer end, then six XLR-male to Phono-plug adapters (NA2MPMM) must be plugged into the crossover/equalizer output connectors.
If you want to use unbalanced cables, then add the following:
3 - Two XLR-female to Phono-jack adapters (NA2FPMF) at the preamplifier balanced outputs.
4 - Six XLR-male to Phono-jack adapters (NA2MPMF) at the power amplifier inputs.

With the conversion from balanced to unbalanced connections there is no longer protection against hum from ground loops, regardless of cable type used. I have found in practice that hum is not a problem at these high signal level stages, if proper precautions are taken with equipment connection between AC power ground (Neutral) and safety ground (Earth). Details are given in the ORION documentation. 
Reduction of hum and common mode signal rejection is the sole purpose for balanced interconnects. Balanced cables and connections become mandatory when dealing with the low voltage levels put out by microphones and associated low impedance levels. They are not necessary for the relatively large voltage and high impedance level interface between preamplifier and power amplifier. Top

 

 Q10 - What cables and interconnects do you recommend?

A10 - I prefer not to recommend any specific product. Cables can have audible effects and some manufacturers make sure they will, either through unusual electrical parameters and/or by suggestion. Weaknesses in the design of the output-to-input interface are exploited. In any case, sounding different does not automatically mean that you now have a more accurate transfer from electrical to acoustical output. 
Realize that for an active speaker, such as the ORION, each power amplifier merely sees a voice coil, either of the tweeter, midrange or woofer driver, and that is an easy load. With the lack of passive crossover filter components the speaker cable capacitance and inductance will have insignificant influence upon the voltage across the voice coil over its used frequency band.
My guideline for speaker cables is to keep their resistance to less than 0.1 ohm for the roundtrip path of the current. This defines the maximum length of a 2-conductor copper cable for different wire gauges.

Wire gauge Max. length in feet
18 8
16 12
14 20
12 30
8 80

I measured the 16 gauge Megacable from Radio Shack (278-1270) that I use. A 10 foot length has 0.07 ohm resistance, 714 pF of capacitance and 1.9 uH of inductance. The line impedance is 51 ohm. A typical tweeter has a voice coil resistance of 4.7 ohm and 50 uH inductance. At 20 kHz this yields an impedance of about  |4.7 + j6.3| = 7.9 ohm. Add to this the cable inductance of j0.24 ohm, and 0.07 ohm resistance for 10 feet, and the impedance becomes 8.09 ohm. This causes a 7.9/8.09 = 0.98 or 0.17 dB reduction in tweeter output at 20 kHz, which is insignificant.  The cable effect is even less at lower frequencies.

Speaker cables can act as antennas in the AM frequency band and may cause distortion in the output stage of a solid-state amplifier, if strong radio frequency signals are present. In particular, the cable capacitance in conjunction with the inductance of a driver voice coil may form a resonant circuit for these frequencies. The resonance can be suppressed by placing a series R-C circuit of 10 ohm/2 W and 0.33 uF/100 V across the cable terminals at the speaker end. 
    Coaxial interconnects with phono (RCA) plugs tend to pick up radio frequencies in the FM band. The currents that are induced in the cable shield must not be allowed to enter the inside of the coax. This requires a very low resistance connection between the outer conductor of the phono connector and the chassis (signal ground) of the equipment that it plugs into. The continuity and low resistance of the shield is also very important for hum and buzz currents, so that they will not induce a voltage on the center conductor. The technical description for this is the Transfer Impedance of the cable and connectors, which must be in the low milli-ohm range. Unfortunately I have not seen this specification used by the audio industry. An excellent description of the theory and treatment of hum and buzz problems in equipment setups with mixed two and three prong AC plugs is given in AN-004 by Jensen Transformers, Inc. I have not found balanced interconnections to be necessary for the high level circuits past the preamplifier. But sometimes it requires to experiment with AC outlets in different locations to reduce to insignificant level the buzz that one may hear with the ear close to the speaker cone. So, when choosing a coaxial audio interconnect look for good mechanical construction, direct contact between shield and connector, and well plated contact surfaces.  
I find what is needed at Radio Shack. I solder speaker cables to terminal strips on the speaker end and use dual in-line banana plugs on the amplifier end. Top

 

Q11 - Can you provide an "upgraded" crossover or "higher quality" drivers?

A11 - The short answer is: No.
The ORION uses the best parts that I know of, consistent with their application. For example, I use high quality 2% tolerance polypropylene capacitors in the signal path. Any large value electrolytic capacitors are paralleled with smaller value polyester and metal film capacitors in the power supply lines. All resistors are 1% tolerance metal film. Operational amplifiers are Burr-Brown OPA2134 and mostly used as impedance buffers. Many claims are made for "audiophile grade" components. Sometimes there is a place for them. I have used many in Audio Artistry products, but not necessarily for sonic benefit as far as I could tell. Much in high-end audio depends on perception. The parts in the ORION material list were not selected by price, or blessing from some audio authority, but strictly on their suitability for the job. The drivers were selected  for application in an open baffle, which implies different demands, and for low distortion. I do not know of better units, but if I see and hear something, I will investigate. Top

 

Q12 - The ORION has noticeable baffle vibrations. Is this a problem?

A12 - The speaker is relatively light at 60 lb and you can feel the top baffle vibrate during high volume levels of sound. The vibration is primarily in reaction to the momentum of the moving cones (m1 v1 = m2 v2). The whole cabinet rocks back and forth, so-to-speak. Since it is all open, the resulting air movement is dipolar in nature, where front and rear radiation tend to cancel. Accelerometer measurements showed only a mild amount of energy storage around 170 Hz, which is probably due to the 8" driver basket and magnet structure and its mounting to the panel. The elastic glue joint between driver mounting panel and dress panel forms a constrained damping layer to minimize any radiation off the baffle. The side panels move only front-to-back which does not contribute to the sound. Box speakers have similar front-to-back vibrations, but in addition the cabinet surfaces flex in and out as a result of extremely high internal sound pressure level and structure borne energy transfer from the drivers. The resulting box panel vibrations are usually resonant with Q>10, leading to stored energy, which is then slowly released. Box speakers can easily radiate more sound at certain frequencies off their wall surfaces than off their driver cones. It can be a major component in the sound of a box speaker. I have tested for, but not found, any audible effects due to the vibrations of the ORION cabinet. There is nothing to be gained from making the speaker more massive. The baffles are essentially sound ducts and could be made of any material with sufficient strength to hold the drivers. Top

 

Q13 - What is the frequency response of the ORION?

A13 - I do not show frequency response measurements, because I have no single set of data that fully describes the speaker. The on-axis response is flat, but that tells very little about how the speaker will sound in your room. It has approximately a cos(a), or figure-of-eight, polar response and that is very important for good bass response, reduced lateral reflections, and consistent timbre in any room.  I measure frequency response at 1 inch from the drivers, at 60" from the cabinet, at 0 degrees on the tweeter axis, at 0 degrees on the midrange axis, half way between the two, with the cabinet outdoors on a tower 10 feet off the ground, with the cabinet on the ground, at 30, 45, 60 and 180 degrees off-axis on the tower, the bass response with the cabinet on the ground at the speaker opening, at 80" from the cabinet, with the cabinet 2 feet off the ground, and many other measurements, as necessary. I measure the raw frequency response of each drivers on the baffle in free-space, the equalized response, the midrange and tweeter combination, the woofer and midrange combination at different elevations and vertical angles, the overall frequency response with different time windows and frequency response smoothing, and so on. All this forms a large matrix of data, that I have learned to interpret for its audible significance. I do not measure indoors for design purposes. The measurement time window is either too short to obtain the correct balance between low and high frequencies, or too long to know what is the room and what is the speaker. I do not measure waterfall plots, which contain many processing artifacts, but I measure shaped toneburst responses for time domain information. I do not measure the "step response", because it is an audibly meaningless test. Just study the loudspeaker measurement data in Stereophile Magazine and note the frequent inconsistencies in their interpretation and their correlation to what the reviewer heard. It takes many more and different response measurements to describe a speaker and to make predictions about its performance in different rooms.
See also my Letter to the Editor in response to the Stereophile review of the Magneplanar MG3.6/R.   Top   

 

Q14 - Could I use a DSP based crossover instead of the ASP?

A14 - It should certainly be possible to obtain the same sonic performance from a custom designed digital crossover/equalizer as is obtained from the analog circuitry of the ORION. One might even remove the phase distortion of the 1400 Hz crossover, and maybe also the phase distortion of the 120 Hz crossover, but not of the 20 Hz highpass. I strongly doubt that the removal of phase distortion will have anything more than very subtle audible effects on the reproduction of program material, if any at all, though I know that phase distortion can be audible under certain conditions and for certain test signals. I have done my own tests of the audibility of practical woofer-to-midrange and midrange-to-tweeter crossovers with slopes of up to 24 dB/oct. Also, I have heard linear phase speakers, but could not detect special merits or characteristics that distinguished them from speakers with well executed allpass crossovers.
You may be drawn to one of the off-the-shelf DSP units, because they allow you to avoid the assembly of the specific electronic filter circuits for the ORION and you could quickly program and experiment with a great variety of crossover functions and equalizations. But if you do not have the capability of making anechoic acoustic measurements of on-axis and off-axis frequency response, then you will not see all the effects of your filters and you may base your design decisions on insufficient data. Still, polar frequency response is only one of the parameters that make the ORION. I doubt that ultimately you will obtain the same dynamic signal range, low distortion and noise floor as with the ASP, especially if you are new to digital signal processing and have to work around the limitations of these commercial units. If you want to experiment with digital crossover/equalizers you could make it an interesting learning exercise, though, to compare the analog and digital filter versions of the ORION. I would be interested in what you find.  Top  

 

Q15 - How does the ORION compare to loudspeakers X and Y or Z?

A15 - You apparently are familiar with those speakers, or consider them a reference, or have formed some opinion about them. To get an idea of where I place the ORION you might read the Design of Loudspeakers page. The Sound Reproduction page explains my design priorities and the importance I give to the motto "True to the Original". The ORION was designed to work optimally in normal living spaces without any specific acoustic treatment other than your normal "stuff of life". The Room Acoustics page goes into technical detail about that feature. Since I did not confine myself by business considerations, I had the freedom to express with the ORION the best that I had learned in over 30 years of loving pursuit.  Top

 

Q16 - Which preamplifier do you recommend for the ORION?

A16 - I have no specific product recommendation other than that your preamplifier should have very low distortion, less than 0.01% total harmonic distortion plus noise at 1 V output, that its frequency response extends at least from 5 Hz to 50 kHz, and that it must have remote volume control capability. Setting the correct volume level from the listening position becomes mandatory for a speaker with the performance of the ORION. I consider any modern preamplifier that does not have remote volume control as incompletely designed and would question its justification. Of course having a remote is by itself no guarantee of a good design either. A preamplifier should sound neither warm nor hard and be simply transparent. I would have a preference for solid-state gear over tubes. Though a good tube preamp would be indistinguishable in its sound from a good solid-state preamp, the tube gear will deteriorate over time and require maintenance. Fortunately it is easy to design a decent preamp so your risk of hearing any signature is low, if you choose a product within the above boundaries. 
I use a Lexicon DC-2 as my main preamplifier, but it does not have surround outputs for SACD and DVD-A. For those I added a Harman/Kardon DPR 1001 hoping that the people who had a hand in the DSP design of the Lexicon also influenced the HK products and that seems to be the case. If I had to replace my current setup, then I would seriously look at the Adcom GFP-715.  Top

 

Q17 - Are there areas for "tweaking" the ORION?

A17 - Yes and no. It seems that everyone has some idea of how to "improve" a loudspeaker's sound. It is not too difficult to change the sound subtly by exploiting weaknesses in the interface between power amplifier and speaker or between different pieces of equipment. But such sonic changes, if they really exist and are not just imagined, should not automatically be taken as improvements in accuracy, but merely as the effect of a slight frequency response adjustment. Whether the accuracy has been improved depends on the recording and can only be determined by extended listening and comparison to a live acoustic reference. Thus, after you have bought or built the ORION and lived with it for a while, so that you have listened to many different recordings, you might try to determine whether the woofer and tweeter level settings are truly optimum for the given set of drivers with the adjustment potentiometers set to their center position as during ASP circuit test.. The sensitivity of woofer, midrange or tweeter driver could have up to +/- 0.5 dB manufacturing variation. The adjustment range of the potentiometers is +/-2.5 dB with tick marks in 0.5 dB increments. A 0.5 dB level change can be audibly quite significant even for the woofer when listening over a longer time period and it may not manifest in the frequency range that has been changed. The listening room sound absorption behavior plays a role too in the overall balance of sound. This is added reason for experimenting with the level settings. Just be careful to set neither tweeter nor woofer level too high. One should not be aware of a speaker's bass or highs until the program material asks for it. Too many speakers draw attention to their "good" high and low frequency response when uncalled for. 
Since the introduction of the ORION there have been subtle changes to the frequency response, especially with Revision 0.1, the midrange driver mounting. These changes are too small to really show in an acoustic response measurement, but they were deemed important based on listening. They are documented for ORION owners and relate to the depth, frequency and Q of the 400 Hz notch filter and the shelving lowpass used for midrange dipole equalization in the ASP. 
The ORION was designed for power amplifiers with very low output impedance such that the combined amplifier and speaker cable damping factor (DF = 8 ohm / Zout) is greater than 50. In such case a Zobel network across the tweeter terminals to compensate for the rising voice coil impedance with frequency has no audible effect. For a much higher output impedance (DF < 10) the Zobel would cause a slight high frequency roll-off, or possibly some other effect if the amplifier's frequency response is load dependent. Using even higher output impedance amplifiers is definitely going to change the speaker's frequency response and likely to increase its non-linear distortion. Speaker cables can act as antennas for AM broadcasting and power amplifier output devices can be susceptible to radio frequency interference causing intermodulation distortion. A resonance damping network across the driver terminals may reduce such effect when living in areas of high RF field strength. (See FAQ10)
"Tweaking" the sound can be exciting or an exercise in frustration and never ending experimentation. I consider the ORION design solid enough so that tweaking beyond adjusting the level potentiometers will yield little improvement in accuracy. Top

 

Q18 - Will there be a review in one of the larger audiophile magazines?

A18 - I doubt that any of the popular magazines like Stereophile, The Absolute Sound, Hi-Fi News and Record Review or their clones in various countries would review the ORION, or even guide their readers to this website. These magazines usually require that a new loudspeaker be available in no fewer than 20 stores, probably as indication that the product is for real, and also to keep their readers from complaining that the reviewed product is not accessible to them. I have seen exceptions to this requirement, but if they were made for the ORION, they might be of benefit to the readers but not to the magazine. Actually it would cost the magazine money and time since I have not invested in an inventory of speakers for temporary or long-term loan to reviewers. Like everyone else, a reviewer either would have to build or buy the ORION. This runs totally against industry practices where a reviewer is courted in every way. Still, I invite any prospective reviewer to first come and visit me to spend time listening and talking. I had a few nibbles from reviewers but exchanges broke off quickly when it became apparent that an ORION would not just show up at their door steps. There is much unusual design practiced in the ORION and some of it runs against common audiophile wisdom as propagated by those magazines. So a visit would also be important for the reviewer to decide if he/she wants to even touch the ORION and all the background information that necessarily would go with it, since this might not be in the best interest of the magazine. After all, a magazine is in business to make money. Linkwitz Lab does not even advertise in one. On the contrary, the performance of the ORION and the information that could be gleaned from this website might actually cast serious doubt in the minds of readers about the true relevance of many products amongst the multitudes of accessories, cables, interconnects, amplifiers and loudspeakers that are advertised and promoted in the magazine's pages. Why would a reviewer want to stir up dust or point out that the Emperor has no clothes? 
Loudspeakers like ORION or PLUTO and the information on this website are inconvenient realities and do not serve a purpose for mainstream audiophile magazines. This might change if their readers ask for a review of these speakers and their origin. But, if you are waiting for a "big time review" of the ORION, do you think that it would have more credibility than the many spontaneous and unsolicited reviews that you can find on the web, or are you just curious what a "professional" reviewer has to say?    Top

 

Q19 - With all your claims about the superiority of dipoles why bother with PLUTO?

A19 - A very large contributor to the naturalness of sound from the ORION is the uniformity of its off-axis or power response, since this sound is heard via room reflection and reverberation in addition to the direct sound coming from the speaker. If this is true, then any other speaker with uniform off-axis response should also sound natural in a room. An omni-directional, monopole or acoustic point source is another form of loudspeaker that can be built with uniform off-axis frequency response over a very wide frequency range, from bass to the tweeter. I had heard such speakers and was impressed how they disappeared and imaged precisely when set up in a room with good acoustics. A point source requires acoustically small radiators and having seen and tested some promising small drivers I designed and built the PLUTO as an experiment and to prove the above claim for the ORION. I was actually surprised how similar the two very different loudspeakers sounded, provided that I listened to PLUTO from a closer distance to reduce the increased contribution of the room to its sound. This small speaker should be looked at as a "near-field monitor" in terms of its placement, but capable of a wide dynamic range and neutral sound reproduction with superior imaging. The direct sound of the ORION reaches deeper into the room and provides a degree of realism that cannot be obtained with the size and much less expensive drivers used for PLUTO. Thus it belongs where room size or budget do not allow for the ORION, or when small center and surround speakers are needed which match the timbre of the ORION. 
    I believe that the non-uniform polar response of a typical box loudspeaker, which is omni-directional at low frequencies and becomes increasingly more forward directional with increasing frequency, distorts the reproduced auditory scene and is recognized as a generic loudspeaker sound. A subject worth study is 'Auditory Scene Analysis' (e.g. Bregman) and how it might relate to loudspeakers and sound reproduction in a room.   Top

 

Q20 - What contributes to the dipole polar response of ORION+?

A perfect dipole generates sound pressure that varies as p = cos(angle) for different directions. Thus at 0 degrees p = 1 or 0 dB. At +/-45 degrees off axis the pressure is 3 dB down, at 60 degrees it has decreased to -6 dB, and at 90 degrees there is no radiation. The shape of the polar response is like two tennis balls that touch each other.

A practical dipole like the Orion+ follows this pattern quite closely in the horizontal plane, but deviates from it in the vertical plane due to driver spacing and layout. Thus, horizontally, from the lowest bass frequencies up to about 400 Hz you have perfect dipole behavior. The open baffle is small compared to the radiated wavelength over this frequency range. Front and rear radiation interact freely causing the characteristic 6 dB/octve highpass response which is corrected in the ORION crossover/equalizer.
Above 400 Hz the baffle is no longer acoustically small and the 8" midrange driver begins to beam. Also the driver's frequency response to the rear begins to roll off. These changes cause additional phase shift and affect how front and rear radiation add on-axis. The polar response actually widens. There is still cancellation of radiation to the sides, but these regions are pointing slightly backwards. The widening radiation pattern is unlike what you would get from the same 8" driver in a closed box where it would begin to beam increasingly as frequency goes up.
As you approach the 1.4 kHz crossover the front and rear tweeters begin to control the polar pattern, matching up well with the open midrange. Even above 4 kHz, as the front and rear dome tweeters begin to beam, you still have a dipolar pattern. The interaction between front and rear radiation occurs now only at increasingly larger off-axis angles. There is still cancellation at 90 degrees and eventually no more radiation from either tweeter towards 90 degrees for the highest frequencies.

Looking at it another way, the horizontal directivity index of the Orion+ starts out at 4.8 dB in the bass, wiggles somewhat around this value between 400 Hz and 4000 Hz and then smoothly increases to about 10 dB at the highest frequencies. This is significantly less overall directivity change than from a conventional box loudspeaker which starts out with 0 dB directivity at low frequencies and tends towards 13 dB at the top end, changing from omni-directional to forward beaming. Thus the off-axis frequency response is not flat and therefore room reflections cannot be copies of the direct sound. Also there are often significant steps in the directivity index in the crossover region between midrange and tweeter. 
(See also the power response examples for open baffle and box loudspeakers and versus piston diameter)

The vertical polar pattern of the ORION+ is dipolar but not perfectly. In general it is narrower and particularly so in the transition region between midrange and tweeter drivers due to their physical separation. Much of the above explanation can be derived from the measured frequency response data for the open baffle Phoenix loudspeaker system, though this loudspeaker has an MTM driver arrangement and only a forward firing tweeter. ORION+ evolved from the Phoenix.

 

Q21 - When do I need THOR subwoofers?

The subwoofers increase the output volume capability below 50 Hz. The ORION and THOR combination maintains the same frequency response as ORION by itself. I recommend to start out with ORION.  Add THOR later when you find that you bottom the woofers on your preferred program material at high volume levels. But, if you know that the system will be primarily used to watch action movies, then for sure add THOR to left and right ORION. If you listen a lot to organ music, or like to impress your friends with trucks and helicopters shaking your living room, then again add THOR's. I recommend to use the AT1802 for maximum volume capability. The bridged AT6012 amplifiers will clip sooner, but you have them sitting idle while you use this amplifier for the ORION. I have THOR's in my system ready for demonstration, but I have found that I do not turn on the AT1802 for my kind of listening, though I play music at reasonably high volume levels.

 

Q22 - Is PLUTO more appropriate for my situation than ORION?

If you have neither the money nor the room (>280 ft2 or >26 m2) to place the ORION properly away from walls, then PLUTO will be the most balanced and accurate sounding loudspeaker you can find.
If you have a large  room but not the money for ORION, then PLUTO is at its best. What you give up compared to ORION is maximum volume level and imaging precision when you sit farther away than the separation between the loudspeakers. I have demonstrated PLUTO at a Tonmeister Convention in Germany in a very large and reverberant office space. These professionals were astounded about the imaging, spatial detail and naturalness of their sound, especially because coming from an omni-directional source, which they had deemed unusable for monitoring and mix evaluation.  

 

 



| Challenge | Requirements | SuppliesPromotion | Subwoofer | Photos | Reviews | ASP | FAQ | Revision 0.1 | Revision 2 | ORION-3 | ORION-4 |
| ORION-WA | ORION - EU

 

 

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: 09/07/2017   -  1999-2017 LINKWITZ LAB, All Rights Reserved