Chris A

I'm late to the party. Nevertheless... I'd recommend taking a look at "affect bias" mentioned in Thinking, Fast and Slow, pg. 103 by Daniel Kahneman (the 2002 Nobel prize winner in Economics--for decision sciences). Also, I recommend Rational Choice in an Uncertain World (1999) by Hastie and Dawes for a more "operational" viewpoint. This has a very deleterious effect in the design of any system of any size, resulting in the types of systems that we see everywhere today, i.e., an example-rich environment of consistently poor decision making...and resulting poor outcomes. It's also essential reading in the rise and fall of business organizations (business cultures all have their unique sets of spoken and unspoken heuristics and biases that vary even within their own organizations). A list of cognitive biases can be found here: https://en.wikipedia.org/wiki/List_of_cognitive_biases It's a long list. A few of those have application to the present topic. Chris

See: Corner Speaker Placement excerpts PWK.pdf You're describing cases #1 to #2 almost exactly. Note that the rule of thumb is that below the room's Schroeder frequency (usually ~200 Hz), the 1/4 wavelength cancellation frequency is also dominant as measured from the floor to the bottom of the loudspeaker. Chris

I play Jean-Luc Ponty (demastered) tracks weekly. I started listening to Jean-Luc with his Civilized Evil album, where I believe he really hit his stride for the remaining albums he's produced. Here's an anthology that will give you an idea of his offerings. I'll start you at the second disc of this anthology (about 1979). The albums beyond this point are what I believe that define Mr. Ponty's real contribution to the genre: Another favorite that's still played quite often--Billy Cobham's Crosswinds: This album features John Abercrombie on guitar, the Brecker brothers on sax and trumpet, George Duke on keyboards, Garnet Brown on trombone, and Lee Pastora on latin percussion, in addition to Cobham on drums. I find this album to be far more listenable than Cobham's Spectrum, which I also play occasionally. I recommend especially The Pleasant Pheasant, Heather, and Crosswinds. Jeff Beck's Blow by Blow is a classic fusion album (so is Wired, but this is much less played in my house). I don't generally play Miles Davis fusion albums, but I do play those associated with Davis during that time: Return to Forever (their Blu-Ray video is spectacular) and the first two albums of the Mahavishnu Orchestra (John McLaughlin and Billy Cobham, et al.). Birds of Fire seems to have taken on a cult status: Jaco Pastorius's Jaco is also a cult classic (much better to listen to after demastering to reverse the bass attenuation found on distributed discs). Marcus Miller's Silver Rain is quite good. Hiromi Uehara's ("Hiromi") albums are absolutely spectacular (all of them): Bela Fleck and the Flecktones Flight of the Cosmic Hippo is also well known among the audiophile community. This album is much better after demastering to restore the bass lines. That's just the fusion artists off the top of my head that I play quite often. There are many others... Chris

Since this is the "Objective-Fi" subforum, and subjective assessments are not allowed for this tiny slice of the much larger Computer Audiophile/Audiophile Style forum, I think the following is allowable (as someone will doubt let me know if it isn't): I am strongly reminded of Peter Azcel (RIP) and his The Audio Critic, who was trying to do what this Objective-Fi subforum is also attempting to do: to separate hi-fi audio reproduction engineering from that slippery slope that some try to endear to us as "subjectivism" (a nice word for a very not-terribly-useful subject). Randi was merely a bystander to the audiophilia world. But he was an important figure, I believe, as witnessed by the large number of frauds that were trying to lie to their audiences about their magic tricks being "real". Randi didn't mumble about that subject and caught many film flam artists red handed. Moving away from that particular subject (and film flam men)--I think that the OP here is trying to make the connection to "audiophilia". Randi was perhaps less successful in this area, but Aczel was more successful. Here is an interesting excerpt from Aczel: Aczel's probably most published article is a "golden oldie": The 10 Biggest Lies in Audio. While I don't currently agree with all that he said, i.e., some measurable stuff has been discovered since Aczel wrote it that gives some different perspectives on some of Aczel's 10 points, but precious few items have really changed. But I do understand and generally accept his points--especially the basis of his objections to "audiophilia subjectivist" claims. I think he's more than just right, I think he's more than justified in his polemics on the subject. It seems that pseudoscience and pure BS has become generally fashionable in much of today's news. I find that it isn't useful, though, without repeatable measurements to back up the "subjective psychoacoustics" claims that subjectivists cling to with all their hands, fingernails, feet, and teeth (which we are able to talk about in this subforum without interference). I've found that no one can agree on anything if everything is opinion--like art critics. The need to repeatably measure and tie to the psychoacoustics is real and is the only way I know that we make actual progress in the world--as evidenced by a few hundred years of using measurements to separate fantasy from facts that can be reproduced anywhere. It's made a difference in what we call "living", like nothing else. Chris

Perhaps a few comments on the subject of distortion sources and interactions might be illuminating: Harmonic distortion (HD) is related to modulation distortion (MD), of which there are both AM and FM sources of modulation distortion. Many people are not aware of the sound of modulation distortion, but it is in fact the sound of opaqueness or muddiness that you hear when loudspeakers having very small diameter direct radiating woofers have when played at higher volume levels. The harmonics generated (as seen in the figure below) by the loudspeaker are also turned into both AM and FM distortion sidebands around the higher frequencies being simultaneously produced ("f2" as shown below). AM distortion comes from the nonlinearities of direct radiator drivers playing both high level bass and midrange-treble frequencies at the same time, where the electrical motor (voice coil beginning to leave its magnetic field at the ends of its travel. The suspension also begins to stiffen (like a spring with spring factor "K"--a stiffening spring). The net effect is modulation sidebands on either side (in the frequency domain) of the higher frequencies being produced. This is the dominant modulation distortion type in low frequency drivers. All modulation distortion sidebands are non-harmonic to both the lower and higher frequencies produced, so their "just detectable distortion" (JDD) levels are typically much lower than harmonic distortion (HD). FM distortion, also called Doppler distortion, in loudspeaker drivers produces additional sidebands on either side of the higher frequencies being played, just like AM distortion, except that the sideband frequencies that are produced are generally different than AM distortion, shown above. One interesting source on FM distortion audibility comes from Keith Howard. This is the dominant modulation distortion type found in higher frequency drivers, and is directly proportional to the bandwidth of the frequencies handled by a driver. The sources of modulation distortion in acoustic drivers can be seen in the following Klippel-generated table--some of which is a little more advanced in terms of this discussion. "HD" is harmonic distortion, "IMD" is FM distortion, and "AMD" is AM distortion. A good discussion on the sources of harmonic and modulation distortion can be found here (Klippel). Group delay (GD)...the first derivative of phase with respect to frequency: Group delay is a noted distortion source that is almost completely ignored in manufacturer's data (except perhaps some studio monitor manufacturers), but when combined with full-range controlled directivity loudspeakers and control of early reflections from within the first 2-3 feet from the loudspeakers, combine to form a different audible presentation from the loudspeakers: increased perception of bass, elimination of harshness (especially for non-multitrack recorded recordings, such as jazz, classical, folk genres), and much greater listener involvement in the recordings. Below is a notional group delay audibility threshold plot vs. frequency gleaned from another audio forum that's useful for comparing against your own REW measurements in-room (because you're probably not going to see these specifications from manufacturers--you have to measure them for yourself): As can be seen there is good agreement in audible perception levels between 500 and 5000 Hz, but is more speculative below 500 Hz. The plot above closely follows personal experience in terms of GD audibility levels. Phase distortion: Little is published in the realm of phase distortion audibility (i.e., total phase shift vs. frequency) under conditions of controlled early reflections and/or full-range loudspeaker directivity, it has been shown that total phase shifts exceeding 90 degrees over the 200-10,000 Hz band can be sensed in detracting from the clarity of the loudspeaker's presentation. ref: Griesinger presentation on Clarity (especially slides 16-19). Noted sources of phase distortion include ported bass bin cabinets and crossover filters, particularly higher order crossovers. There are other forms of distortion not discussed above (notably compression and power/directivity distortion) but note that the choice of loudspeaker type/configuration tends to lock-in these other forms of distortion. Chris

Here is a typical mastering EQ curve used on a particular album (Siamese Dream by Smashing Pumpkins, 1993): As you can see, even the mastering/mixing people can significantly unbalance the on-axis response of the loudspeakers in-room to achieve the effect they are seeking with the instrumentation they're working with. Chris

I'm not sure how we got from my above discussion to here, I'll address your questions... In most of these instances, upturned bass and treble SPL response is a reaction to typical mastering of music (i.e., making the tracks sound louder via attenuation of bass response below 100 Hz) and also a response to narrowing of polar response of the tweeters, and broadening of polars below 1 kHz. Additionally, if you draw a straight line across the untrained listeners curve, you will see a drop out in response in the midbass (generally 100-300 Hz) and midrange (300-1000 Hz) that is typical for those listeners trying to self-correct in-room midbass decay issues ("muddiness") and loss of polar control via direct radiating bass (woofer) loudspeakers. This is partly due to the music tracks themselves (and what they are listening to) and part loudspeaker power response issues. If you've never heard a loudspeaker that can control its polars below 1000 Hz in-room, you might not have experienced the effect of full range controlled directivity in-room and the effect that has on desired loudspeaker EQing. So, by my response above, it's usually not that simple of an "on-axis SPL response" by itself. It has even more to do with the off-axis response and the music tracks being played (and the genre of music, i.e., its instrumentation, etc.). Most audio enthusiasts miss this point: the full-range loudspeaker directivity effect on listeners desired on-axis SPL response. Chris

Beginning discussion on loudspeaker requirements/capabilities interactions: This is an area that I believe results in the different types of loudspeakers we see in home hi-fi and commercial marketplaces, and (candidly) this is where I had intended to focus the discussion when I started this thread. There were preliminary discussions on this subject, above, but were necessarily brief in order to also fill in some conceptual gaps in knowledge that I believe most hi-fi enthusiasts simply do not see or haven't considered. First, let's start with the biggest constraints on acoustic performance: Small size and expected shape of the loudspeaker enclosure overall (i.e., "WAF" and "MAF" [M=man]), and Cost constraints on the finished product--which turn into price categories for offered loudspeaker models. Note that these two design constraints actually work to significantly and severely limit the acoustic performance of the loudspeakers in home hi-fi applications today. If you were able to transport yourself back to the late 1940s when home hi-fi was kicking off for the first time, if you were to show most of today's loudspeaker models to loudspeaker engineers practicing in the 1940s, they'd laugh at them as "atrociously undersized and entirely the wrong shape and configuration for hi-fi performance". This is useful to remember when talking about hi-fi loudspeakers today. Contrary to the general thought that "we know a lot more about loudspeaker technology today", most of the physical and measurable psychoacoustic factors that govern loudspeaker design today were largely already known by 1949. What's changed today is buyer expectations...in terms of size, shape and cost (and willingness to severely compromise loudspeaker acoustic performance in order to meet the two constraints mentioned above even if they have accommodated to the sound of these ultra-small boxes). If you look at the highest-priced "high end" loudspeakers--they are large and most of them are also not shaped like shoeboxes. Instead, they are usually require similarly large rooms to be placed into--to function at their intended levels. Unlike virtually all other discussions of loudspeakers within the home hi-fi enthusiasts marketplace, for the purposes of this particular discussion, it will be assumed that the starting focus or emphasis here is on acoustic performance over form factor and miniature size (the two constraints shown above). Additionally, the cost of the loudspeakers is not something that you would likely find in a lineup of Audio Science Review forum tests (i.e., the lowest cost models available from the major brands). Loudspeaker performance discussed here will begin toward a larger size and higher performing in terms of lower distortion (distortion as defined above). As the subject evolves further down the road, we can talk about smaller size (but not until higher fidelity sound reproduction loudspeakers are first discussed in detail. So the for purposes of requirements interactions, I'll repeat a figure from the top of this thread for reference: Note the three major areas identified here: transfer function (i.e., SPL and phase response), freedom from distortion, and directivity. Just like Hofman's Iron Law, if we put a particular emphasis on transfer function response (usually focused on-axis only), we typically give up low distortion--especially modulation distortion which is all inharmonic in nature and therefore most objectionable to listeners)--and directivity control. We tend to end up with small direct radiating loudspeakers of the "monkey-coffin" variety, of which there are literally thousands of extant example models (and companies based on this requirements emphasis). The curious thing about this loudspeaker performance area is that this one responds the most easily to DSP correction methods and IIR/FIR filtering techniques. If we combine small size with loudspeakers designed for transfer function linearity, we get the vast majority of direct radiating loudspeaker designs found today. But we also get one other trade off: low efficiency (via Hofman's Iron Law) that limits the allowable dynamic range of the loudspeaker to significantly below that of most real music found today, particularly that of multitrack-recorded (i.e., built on the mixing board) amplified music. Even music performed via large unamplified ensembles, such as orchestras and wind symphonies have too much dynamic range for small loudspeakers to reproduce without severe and limiting modulation and compression distortion severely limiting the reproduced dynamic range and clarity. Some other loudspeaker types that prioritize transfer function linearity are dipole radiating film-type loudspeakers, such as electrostatics and dynamic-membrane types (e.g., "Magnepan"). The usually trade away low modulation distortion and controlled directivity. (In fact, dipoles have the added fun of the owners having to deal with a backwave radiating field via their listening room design in order to rectify the phase relative of the backwave at lower frequencies to that of front-wave in order to avoid significant listening position cancellations.) If we instead first focus on low distortion, particularly modulation (inharmonic) and compression distortion, then the size of the loudspeakers typically grows to that which is required to easily avoid the nonlinearities of small diaphragms moving air relative to their wavelengths, and in particular, the use of "acoustic transformers": acoustic waveguides or horns to reduce moving mass effects and other sources of modulation distortion, i.e., the sources coming from low acoustic efficiencies of direct radiating drivers without acoustic transformers. Higher efficiencies are the flip side of avoiding modulation distortion at realistic playback levels. Lastly, if we focus on full-range loudspeaker directivity in-room (as evidenced via Toole's and Olive's own performance factors), we find ourselves again in the realm of acoustic waveguides/horns to control the polar acoustic output (otherwise called "power response" or integrated SPL over output angles). So for the above, all other things being equal (and loudspeakers are not severely undersized via major constraint #1 detailed above), the approach to create both low distortion and controlled directivity loudspeakers is via use of waveguides/horns. This is, in fact, the way that electrodynamic loudspeakers were first designed--for cinema use (starting approximately in 1930 via the WE horns, then the Shearer Horn system, then later the Voice of the Theater (VOTT) systems from Altec-Lansing. These had the added bonus of not requiring large amounts of electric power, which was expensive during the tube/valve amplifier era. So, depending on where you put your emphasis (threshold requirements performance levels), you get entirely different loudspeaker designs. Next up: the effects of DSP transfer function linearization/crossover filtering and acoustics computer modeling on opening up the design space of hi-fi loudspeakers. Chris

Some process-based information on what takes place in loudspeaker development at larger corporations: Generally speaking, most DIY loudspeaker efforts involve buying the drivers and putting them into DIY boxes, then generating passive crossover networks that stitch the overall SPL response together (for better or worse), sometimes going as far as adding notch filters (attenuating) to smooth the SPL response. Usually little is done to minimize growth across the crossover interference bands, unless using a third-party deconvolver upstream of the amplifier to flatten the on-axis phase response. As far as a loudspeaker engineer is concerned (and depending on the capabilities of the enterprise they work for), drivers can either be selected like catalog items (with significant developmental testing required as well as incoming inspection QA lots to ensure that the properties of the drivers don't change with production). So as such, many/most loudspeaker engineers not involved with driver development, and select drivers based on their needs and on measurements (i.e., the source of the performance defects are not investigated). Parameters measured include: SPL and phase response (high and low drive levels)--looking especially for resonances in the drivers or the box Directivity vs. frequency (horizontal, vertical) Harmonic and modulation distortion, compression distortion Input electrical impedance response Power handling and voice coil/passive crossover heating/temperatures Box/enclosure design -- perhaps using miniature accelerometers to measure bending/resonance modes, etc. Subjective listening trials to catch anything that wasn't caught in the above list of performance capabilities The thresholds for each capability is usually company dependent and price-range dependent, i.e., lower priced loudspeakers generally having less stringent performance thresholds. If the company produces cone/dome type drivers and/or compression drivers, etc., the situation is different in that there is usually a team doing custom drivers and a separate team doing the balance of the loudspeaker development. Many companies design their loudspeakers such that one driver is custom, and perhaps the other drivers are catalog items or other off-the-shelf non-developmental items. The custom driver parameters are usually picked to preclude DIY or third party assembly of the loudspeakers (in order to assure that the consumers do not try to bypass the higher prices charged by the company for the finished loudspeaker models. [This is especially true now that very good freeware or other low-cost measurement applications and low cost calibrated measurement microphones are available, as are low cost/high performance DSP crossovers that can be used to eliminate the passive crossovers used on most consumer-grade loudspeakers (i.e., trading the requirement of mono-amping the loudspeakers with bi-amping or multi-amping). In particular, this practice has been creeping steadily upward in recent years, awaiting a more general realization that DSP crossovers and multi-amping provide much higher in-room fidelity than stock passive crossovers.] If the company produces its own drivers, then many more tests are performed by the integration team (the loudspeaker designers) on the received developmental drivers in order to provide feedback to the driver design team(s) to iterate their designs. Lastly, the loudspeakers can be sent off to get EASE-type data gathered from a third-party testing firm anechoic chamber or Klippel NFS-type system. This is especially true of loudspeakers built for commercial use. Chris

I use the term "waveguide" mostly because so many audiophiles here have trouble with the term "horn". I think that Bjorn's book helps to bridge some of that divide: https://hornspeakersystems.info/ https://www.parts-express.com/high-quality-horn-loudspeaker-systems--500-032 It's a good update on Beranek's "Acoustics" and Olson's "Acoustical Engineering" texts. The theory portion of the above book (i.e., the last ~40% of the book) looks good and is useful in terms of theoretical considerations and current analysis developments, but is a little thin in terms of current high performance horn design which I think Bjorn is trying to market himself as well as other companies with their own offerings. The front portion of the above book is a comprehensive look at the development of horn-based loudspeakers over time since the beginning of home hi-fi loudspeakers appeared in the 1920s (and before). Note that horn design developments over the last 20-30 years, i.e., since 1990-2000, have eclipsed the performance of those horns designed before that time. There are a lot of poorly performing horns out there that exist from before that time. But this thread is not about horns/waveguides exclusively...it's about loudspeaker requirements as viewed from a large company loudspeaker engineer's perspective. Chris

The last major category of loudspeaker acoustic requirements (as opposed to non-acoustic requirements) is directivity: The biggest issues that I see with directivity requirements/capabilities can be grouped under the three major subheadings above: directivity at higher frequencies (generally above 1-2 kHz, but this can extend down to ~500 Hz), and low frequency directivity (below the higher frequency directivity regime). Additionally, there are issues with coverage: 90 degrees horizontally (-6 dB) above the room's Schroeder frequency--typically taken to be ~200 Hz seems to be a sweet spot. This typically limits the vertical coverage to about 60 degrees in order to avoid pattern flip at lower frequencies, without introducing massive amounts of diffraction into the mix. Lastly, there are issues regarding the smoothness of directivity response (i.e., frequency-dependent directivity). There are often large directivity mismatches at the crossover interference bands, and these play havoc with the design of effective crossover schemas and with (calibrated) subjective assessments of sound quality--as detailed in Toole's and Olive's articles. In practice, directivity issues interact with other performance issues (as do most other performance parameters highlighted above). The discussions that I plan to pursue at this point will be related to how these performance requirements/capabilities interact with each other and are therefore loudspeaker configuration-dependent and are highly affected by non-performance considerations, such as cost and form factor/size. Too often, available acoustic performance is traded away without much discussion because of fears of meeting appearance thresholds from non-engineering functions within large corporations/enterprises--notably marketing/sales organizations who are often not driven by the acoustic performance of the loudspeakers, but rather their appearance. Next up: discussion of loudspeaker requirements/capabilities interactions. Chris

I'm really not sure what your needs are, but I'm pretty sure that what you intend and what I'm currently working on are not coincident. I would recommend that you start a separate thread on the exact subject (which looks like random measurements). (As the OP) this thread is clearly focused on something other than your expectations. Chris

Expanding the distortion hierarchy... (We'll get to directivity next after the distortion hierarchy is discussed.) Here, the story begins to get a little more interesting-in my view. Notice that I've "double dipped" on phase/impulse distortion here vs. the transfer function hierarchy, but perhaps choosing one place or the other would be the next step in finalizing the rolled-up hierarchy. The light blue background indicates that these performance capabilities are correctable using signal processing. There have been a few attempts to using DSP to correct harmonic and other transient distortion (David Gunness being a notable author), but general purpose applications and hardware to accomplish significant performance enhancements in this area are not generally available--nor free as of this writing. I'll put that discussion on the "we'll check on that later" pile. In general, to get lower harmonic distortion, drivers and waveguides (or cabinets housing the drivers in the case of direct radiating) need to be selected carefully. Same thing for modulation distortion. (Note that modulation distortion is ~16-20 dB lower in well-designed waveguides vs. using the same drivers in direct radiating mode--most people get that one wrong.) Interestingly, most DIY loudspeaker designs that I I've seen usually pay lip service to harmonic distortion, and virtually no one that I've seen even acknowledge modulation distortion figures. (Note also that Klippel NFS systems produce AES standard reports for modulation distortion.) Here also, I've captured the voice coil heating here in compression distortion. Passive crossover network heating is not captured here. There are a technology-dependent factors shown here (waveguides, reflex ports) but are not exhaustive. Chris

Not in my house.

Note that I own no stock in Danley and have no other financial interests with them, nor do I own any stock in any other loudspeaker company or have any financial interests in any of them. I sell no products and charge no one for my services. Chris