[bummrush]

Even balance  and clarity

[FullRangeMan]

Such was the case at the April 2015 Axpona audio show in Chicago.  90% of the rooms all sounded similar - artificial/cartoonish: life turned into a poster of only primary colors without hue, tone, or texture.

This is the xover effect, after the music signal pass the xover
parts the resulting signal have no harmonics and micro tonal info.
These delicate electric signal are time aligned each other.
All the micro Volts signal are lost as heat in the xover parts.

Some xovers are built to work best at hi power handling.
The final result are a hi-fi speaker, expensive and synthetic
sound, it will sound nice just with Electronica music.
Seems you are ready for a good full range speaker.

[JLM]

This is the xover effect, after the music signal pass the xover
parts the resulting signal have no harmonics and micro tonal info.
These delicate electric signal are time aligned each other.
All the micro Volts signal are lost as heat in the xover parts.

Some xovers are built to work best at hi power handling.
The final result are a hi-fi speaker, expensive and synthetic
sound, it will sound nice just with Electronica music.
Seems you are ready for a good full range speaker.

I'm just trying to learn.  By the way about 12 years ago I commissioned good single driver speakers, Brines Acoustics M18-F200.  They are floor standing transmission lines using the "mighty", now discontinued, Fostex F200A driver (not your typical Fostex: 90 dB/w/m, 8 ohms, 30 - 20,000 Hz, 109 dB peak at 1 meter, AlNiCo magnet that provides a full bodied sound).

[Freo-1]

This is the xover effect, after the music signal pass the xover
parts the resulting signal have no harmonics and micro tonal info.
These delicate electric signal are time aligned each other.
All the micro Volts signal are lost as heat in the xover parts.

Some xovers are built to work best at hi power handling.
The final result are a hi-fi speaker, expensive and synthetic
sound, it will sound nice just with Electronica music.
Seems you are ready for a good full range speaker.

While I think you raise some valid points about crossovers, there is no free lunch.  Single driver speakers certainly have some good points, but, they also have issues as well.  It's very hard to get good LF from a single driver without using very large enclosures.  There are issues with dispersion, and HF linear performance.  The mid-range can be very special indeed.

I think there are a number of two way monitors available that can sound excellent, with only having to deal with crossover for one narrow frequency range.  Extreme LF can be achieved with subwoofers.  Active speakers can effectively mitigate crossover issues.

[G Georgopoulos]

A room can make a speaker tone sound different (scientifically,yes)...
so i guess you can't ever reproduce the sound of a theater unless you put
a ruler flat speaker into that theater.
 

[FullRangeMan]

I'm just trying to learn.  By the way about 12 years ago I commissioned good single driver speakers, Brines Acoustics M18-F200.  They are floor standing transmission lines using the "mighty", now discontinued, Fostex F200A driver (not your typical Fostex: 90 dB/w/m, 8 ohms, 30 - 20,000 Hz, AlNiCo magnet that provides a full bodied sound).

Nice, I was unknow what speaker you have.
STM the major compromise from FR are limited power handling,
it may be associated to low sensitivity sometimes.

[ACHiPo]

Freo-1,

Boy all that seems so right, but the ATC prices are all so wrong ($4990/pair for the cheapest active ATC, the small 2-way SCM20ASL PRO MK2).   

Perhaps, but they continue to be on my list of desired speakers based on years and years of rave reviews and endorsements.

[FullRangeMan]

At low sensitivity, 4 ohms, hi price Sonus Faber may be a alternative.
Mainly a used Concerto Domus floorstanding, very transparent sound, bass alot and a small smart xover.
Hi WAF acceptance with real leather and wood finisches.

[Mag]

I primarily listen for transparency and clarity of a recording (I re-master my own recordings) when a recording is transparent and clear I can get very good results.

I then listen for presence, like the band is right in your room only on a smaller scale. Presence is an element I hear at concerts even when the band sounds like crap. It has to do with bass vibes that let you know you are there.

Scale of the recording can be made to sound large just by cranking the volume. But that would have the neighbours complaining as I wouldn't be able to contain the bass vibe to just my home.

So I settle for a smaller scale that has the realism of the real thing. Then I just immerse myself in the stereo imaging and enjoy the music.

[Duke]

I like lots of air. I like hearing instruments... Don't care about off axis response at all. What I like to hear is a room that is lively with reverb and lots of good air around the instruments...[emphasis Duke's]

Even if you only listen in the sweetspot, as long as you're not listening nearfield or outdoors, most of the sound that reaches your ears started out as "off-axis response".   So I think it matters more than you're giving it credit for.   

*  *  *  *

For many years I had the good fortune to live with various pairs of SoundLab fullrange electrostats.  This gave me the opportunity to investigate the influence that arrival time of the reflections has on perception.  I did not conduct controlled blind testing so consider the following observations to be anecdotal.

SoundLabs have exceptionally uniform radiation patterns, transitioning from the familiar dipole figure-8 in the bass region to a pair of roughly 90-degree lobes, front-and-back, across the rest of the spectrum - in other words, very nearly fullrange constant directivity.   And the rear radiation was spectrally identical to the front radiation, so the reflected backwave energy was inherently spectrally correct.

I experimented with positioning the speakers different distances out from the front wall (that is, the wall behind them).   What this was doing is, changing the time delay before the arrival of all that additional spectrally-correct reverberant energy.   I investigated this so I could offer qualified advice to customers on how the SoundLabs would work given their particular setup constraints, and/or how to deal with less-than-ideal situations.

I got very good results with the SoundLabs about 5 feet in front of the wall, and 7 feet was even better.  Three feet was about the practical minimum; at 2 feet or less, the backwave started to become more detrimental than beneficial, and absorbing it was a net improvement.   The detriment was to both imaging and timbre.   

Now I'm not the only one who has made similar observations.   Magnepans are conceptually similar to the Sound Labs (fullrange dipoles that generate a spectrally correct backwave), and you'll find that Maggie owners report best results with their speakers well out into the room.

The underlying theme seems to be that the timing of the backwave energy's arrival is very important, and longer delays are better than shorter ones, within the limits of practical placement in a home listening room. 

We don't see this discussed much because only a few speaker designs give you the option of significantly delaying the arrival of a major portion of the reflected energy.   So we have studies that look at the first reflections of various conventional speakers, but none that I know of examining the implications of path-length-induced time delay on the backwave of a dipole or bipole. 

Anyway in my opinion, one part of "getting the reverberant field right" would involve taking advantage of the psychoacoustic mechanism we see at play in the preference dipole owners have for a fairly long time delay between the first-arrival sound and the onset of the backwave energy. 

There is another significant psychoacoustic mechanism that can be taken advantage of in the course of "getting the reverberant field right", and it has to do with the direction that the (preferably late-onset) reverberant energy arrives from, but that's a more complicated topic with even less information out there, anecdotal or otherwise.

[poseidonsvoice]

Wonderful post Duke, thank you. Can you comment on something else? As far as controlling directivity is concerned:

1) What is your view on the importance of preserving the directivity pattern between let's say a woofer and a tweeter in a waveguide at the crossover? Is this much harder to do without a waveguide?  If without a waveguide, is it harder to preserve the directivity patterns as you transition from mid woofer to midrange to tweeter to super tweeter, as we see so often in these polar plots?

2) What is your view on achieving narrow (90 degree or +\- 45 degrees) vs wider but still controlled directivity? What are advantages and disadvantages of both?

3) Which one is more important to achieve, question 1 or question 2?

4) How low of a frequency should one aim in controlling directivity? 1khz? 500Hz? 250Hz?

5) How important is a flat DI versus a smoothly rising DI (from say 1khz to 20khz) as long as the DI is at least 6dB?

6) Relative to controlling directivity in the horizontal axis, how important is it to control directivity in the vertical axis?

7) How does all of the above impact room treatment at the 1st reflection points on the side wall, ceiling, floor, and front wall? What real world experience have you had (irrespective of measurements)? How does this affect image specificity vs sound staging and spaciousness?

For the purposes of simplicity, let's just preferably discuss frequencies above Schroeder, above 300Hz.

I'm sorry these questions sound like a final exam questionnaire! I'm not trying to test but trying to learn more as well as provide some basis for this thread which I feel has veered off topic somewhat.

Best,
Anand.

[Duke]

Wonderful post Duke, thank you. Can you comment on something else? As far as controlling directivity is concerned:

Thank you very much, Anand.  Having some idea of where you're coming from, that means a lot to me. 

It might take me a few posts and/or a few days to reply to all, I'm just starting to do the last-minute pre-RMAF mad dash...

1) What is your view on the importance of preserving the directivity pattern between let's say a woofer and a tweeter in a waveguide at the crossover? Is this much harder to do without a waveguide?  If without a waveguide, is it harder to preserve the directivity patterns as you transition from mid woofer to midrange to tweeter to super tweeter, as we see so often in these polar plots?

One of the secrets to a "seamless" crossover is radiation pattern matching in the crossover region.  The ear is not very good at hearing phase shift or a change in materials, but it is very good at hearing a loudness change, and since the off-axis energy contributes significantly to perceived loudness, we're pretty good at hearing that as a discontinuity, right smack in the crossover region.

It's almost never possible to pattern-match without some sort of waveguide on the tweeter, but it is possible to make a least-bad compromise between an on-axis dip at the bottom end of the tweeter's passband, and an off-axis flare in the same region.   Visually what stands out in normalized off-axis curves like the ones in Stereophile is usually the dip at the top of the midwoofer's passband, but sonically what stands out is the peak just above that dip, at the bottom end of the tweeter's passband, so that's what I usually speak in terms of.

I think it would be easier to do a wide-dispersion speaker with decent off-axis behavior with a bunch of decreasing-diameter cones 'n' domes than it would be to do a well-controlled, Geddes-esque pattern speaker. 

2) What is your view on achieving narrow (90 degree or +\- 45 degrees) vs wider but still controlled directivity? What are advantages and disadvantages of both?

Only the 90 degree pattern really does that "super wide sweet spot" thing when you criss-cross the axes in front of the listening position.  I think that's just too cool to pass up.  I don't know how many of my customers actually use that, but it's there if they want to.  Also the reduced amount of energy in the early reflections helps image stability and coherence. 

With a wider pattern, we get more energy out into the reverberant field and so we have a richer presentation, with more of the feel of being enveloped in the acoustic space of the performance.  And since you stipulated controlled directivity for the wider-pattern speaker, we'd also get less net discrepancy between the first-arrival sound and the power response.  I dig both of those attributes too!

Being of the unreasonable sort who wants to eat his cake and have it too, in my most ambitious designs I try to get the best of both worlds by using a directional main array plus a secondary array tailored and aimed with the reverberant field in mind.

[G Georgopoulos]

It's all in the reverberation of the room... 

[JLM]

The elephant normally IS the room.  Yes, we primarily hear the interaction of speaker and room, but specifically how does the speaker interacts with the room?

As I understand, controlled directivity only allows for a single first reflected side wall sonic ray (frequencies above the Schroeder frequency act like rays) if the speakers are aimed to cross in front of the listener.  If the room is wide enough and the speakers are spread out far enough that reflected sound will be delayed by 10 milliseconds (travel 11 feet farther than the direct wave to the listener) so the brain can separate the two.  Keep in mind that the direct wave, if from the right speaker, will in in line and received primarily by the listener's right ear and the side wall reflected sound will be in line and received primarily by the left ear.  This effect of separating what we hear in one ear versus the other is what allows stereo imaging/soundstaging to be heard. 

In practice center soundstage can be lost if the speakers are spread too far out, OTOH in narrow rooms effective wide-band sound absorption (located at first side wall reflection points) can help reduce the first side wall reflections.  In my 8ft x 13ft x 21ft room I've obtained the best results with speakers crossing in front of the listening position 7ft apart and 6ft from the front wall, listening 9ft from the front wall, and use of GIK 244 panels at first side wall reflection points.  This makes for a slightly altered Cardas near-field setup.  With speakers any further apart and the center of the soundstage collapses (which develops along the front wall). 

With controlled directivity, none of the first sonic rays hit the front wall and if you listen at least 6 feet from the back wall the sounds reflecting off of it will have the 10 millisecond delay that the brain needs to differentiate the direct and reflected sounds.  So vertical reflections are less important for imaging, but like all reflections play an important part in providing spaciousness (or reverberant field as Duke says) versus listening in an anechoic chamber.  Keep in mind that all this is meant to make imaging easier to hear imaging, not that it can't be done by other means to varying degrees.

[FullRangeMan]

The elephant normally IS the room.  Yes, we primarily hear the interaction of speaker and room, but specifically how does the speaker interacts with the room?

I dont know this answer but also important is how the brain listen the room/speaker.
We primarily hear the interaction speaker/room IF the room is live, if the room is too stuffy we listen the speaker first.

[JLM]

I dont know this answer but also important is how the brain listen the room/speaker.
We primarily hear the interaction speaker/room IF the room is live, if the room is too stuffy we listen the speaker first.

Psychoacoustics is a fascinating field of study that way too few of us (myself included) know much about.  But I've been in a couple of anechoic chambers (the ultimate "stuffy" setting and it's too weird to enjoy.  Have also been in a 4 different geodesic domes that had the opposite effects (you could hear a whisper from across the room, but in the center everything has an echo and at the right frequency the resonance was overpowering). 

Didn't really want to room acoustics (wrong circle), but the speaker/room interaction does play into what sonic attributes we primarily listen to.

[jtwrace]

but the speaker/room interaction does play into what sonic attributes we primarily listen to.

Hence the reason to buy speakers that deal with this very well....

[Duke]

Didn't really want to room acoustics (wrong circle), but the speaker/room interaction does play into what sonic attributes we primarily listen to.

Arguably the most basic thing a speaker has to get right is the tonal balance, but because tonal balance is very much a room-interaction thing (since most of what we hear is reflected energy), right off the bat we're swimming in the "deep end" if we dive into the question of which sonic attributes matter the most.   So what looks like a tangent is just going deep into one of the basics, in my opinion anyway. 

[jtwrace]

Hence the reason to buy speakers that deal with this very well....

Arguably the most basic thing a speaker has to get right is the tonal balance, but because tonal balance is very much a room-interaction thing (since most of what we hear is reflected energy), right off the bat we're swimming in the "deep end" if we dive into the question of which sonic attributes matter the most.   So what looks like a tangent is just going deep into one of the basics, in my opinion anyway. 

Which relates to my post.  Correct? 
 
 

[Duke]

Which relates to my post.  Correct?

In my opinion, absolutely!