138 replies to this topic

[genek]

One thing wide dispersion assures that listeners with narrow dispersion speakers can't appreciate, you can enjoy the stereophonic effect over a much wider area of your listening room. This means several people can enjoy it at the same time and you are not constrained to sit in one specific spot. I've been listening to my speakers with an ear towards the apparent width of the soundstage, something I rarely pay attention to and it can be remarkably wide. Of course my speakers don't merely radiate flat to 90 degrees and more, they compensate for the hf absorption of the walls so that the reflections are almost flat too. It's an added benefit I hadn't considered. As I've said, I don't find it particularly important personally.

This is probably the single most important distinction I have noticed about my 2ax's and 3a's compared to other speakers I've listened to, perhaps because unlike frequency response/tonal balance, adjusting my tone controls doesn't do diddly to increase or decrease it. I've never managed to sit close enough to a live source to be able to distinguish the relative locations of individual instruments, but even from the back of the hall I can tell if the enture orchestra appears to be getting up from their seats and wandering back and forth across the front of my living room just because I got up from my chair. I've not had the experience of trying a mutli-tweeter setup, but if the effect is to improve the "everyone stays put" effect even more, from my point of view that could only be better.

[Zilch]

It seems to me that once you've accepted that a multi-tweeter arrangement is acceptable for improving dispersion, it would be simpler and more cost effective to just use more of them than to design one from scratch that is so novel and where the possibilities of new problems would emerge. That's what Allisoon did in LST. Hard to understand why he didn't stick with that notion in his own speaker line. One thing wide dispersion assures that listeners with narrow dispersion speakers can't appreciate, you can enjoy the stereophonic effect over a much wider area of your listening room. This means several people can enjoy it at the same time and you are not constrained to sit in one specific spot.

Nope, that screws it up, actually.

I've never managed to sit close enough to a live source to be able to distinguish the relative locations of individual instruments, but even from the back of the hall I can tell if the entire orchestra appears to be getting up from their seats and wandering back and forth across the front of my living room just because I got up from my chair. I've not had the experience of trying a mutli-tweeter setup, but if the effect is to improve the "everyone stays put" effect even more, from my point of view that could only be better.

Read up on the precedence effect, and Toole's a good place to get the facts. It can be manipulated over a limited, but wide, image rendition zone, a trompe l'oreille, as it were. The primary variables are phase and level. There's only one "true" sweet spot by phase, but level can effectively broaden it and low IACC early reflections add spice. I've linked several times now how to do it, and there's a major clue to a proven approach right up font in the "recycling center" ZilchLab pic I posted @ #21. Two major clues are shown, actually, but the second one is in the background and hard to see; I thoroughly documented both several years ago over on LHF. Spraying the room with wide dispersion from multiple tweeters doesn't get there....

[soundminded]

Nope, that screws it up, actually.


Read up on the precedence effect, and Toole's a good place to get the facts. It can be manipulated over a limited, but wide, image rendition zone, a trompe l'oreille, as it were. The primary variables are phase and level. There's only one "true" sweet spot by phase, but level can effectively broaden it and low IACC early reflections add spice. I've linked several times now how to do it, and there's a major clue to a proven approach right up font in the ZilchLab pic I posted. There's two major clues, actually, but the second one is in the background and hard to see there; I thoroughly documented both several years ago over on LHF. Spraying the room with wide dispersion from multiple tweeters doesn't get there....

Zilch, I'm not talking about one of those ring radiator bullet tweeters like an 075, I'm talking about something designed with high fidelity music reproduction in mind...like those Audax 3/8" polys I like so much. Maybe the bullet tweeters could find new life as a sonic weapon for use against Somali pirates.

[Zilch]

Zilch, I'm not talking about one of those ring radiator bullet tweeters like an 075, I'm talking about something designed with high fidelity music reproduction in mind...like those Audax 3/8" polys I like so much. Maybe the bullet tweeters could find new life as a sonic weapon for use against Somali pirates.

The bullet tweeter is most appropriately employed for stripping wallpaper, actually, though sonic weaponry deserves further investigation for combating piracy, yes. Do you see one in the pic?

Those more conventional jobs certainly had wide-enough dispersion, and of course they also did not have any of the horizontal interference effects that happened with the two-panel versions.

WAIT! Those are of no consequence, remember...?

Response curves are shown for each driver individually so as to eliminate interference patterns which have little to do with true power output, and which are inaudible in the reverberant field of a listening room.

http://www.classicsp...r...ost&id=4887

At least I am not afraid to post messages under my real name.

Now, Howard, you promised Ken you weren't going to do this anymore, remember? Having short-term memory issues, are you?

The forum is well aware of why you post under your real name, and it's now quite apparent, in your particular case, that may not be all so good an approach as you presume....

[genek]

Spraying the room with wide dispersion from multiple tweeters doesn't get there....

One pair of dome tweeters has done the job well enough for my needs for many years now, albeit only for sources in front of me. Maybe some other scheme could do it better, but one principle I learned long ago that has simplified my life considerably is when to draw a line at "well enough" and stop. I am curious to see what's going to happen now that I'm in the process of adding several more channels to my living room for cinema purposes, and if I'm going to like the result when applied back to music or if I'll end up turning off all those extra channels and reverting to stereo when listening with the TV turned off.

[Zilch]

Please, Howard, look at Toole Fig. 16.6 b] and c] again, and think about it a bit from the perspective of generating an accurate ipsilateral first reflection.

Geddes suggests, "Forget it; it's the contralateral we want for enhanced ASW...."

[kkantor]

Yeah, I know I promised.

However, I still find it odd that a guy who is tooting his horn as loud as you (thousands of posts, remember, with suggestions that we come over to your other site locations to read what you have to say there) would not want to attach his real name to his work. Of course, one advantage to not using your real name is that later on, down the line, if you are proven to be a fool you do not have to worry about your real-world status. Nobody can laugh at you out there where people actually live if nobody knows your real name.

I post under my real name, because that is my name and I am not afraid to hang my opinions on it. If I were still in the audio journalism business (and it looks like The Sensible Sound is not goint to be revived, and I had no intention of writing for the new magazine, anyway) or trying to sell books (they are all OP, and I no longer get royalties) I could see where me using my real name would look like shameless self promotion - and for money, yet. However, I am retired, so that is not an issue.

What is at issue is personal integrity, and as I noted above I am not afraid to hang my opinions (even if they someday are proved to be in error) on my real name.

Howard Ferstler

A big part of "personal integrity" is doing what you say.

-k

[Zilch]

Here's a pair of Karma Indignias at tweeter height and on acoustic center between them at 42". In this instance, "reverberant" begins with the floor bounce (the first reflection) at 8.42 ms. The quasi-anechoic window is 5.25 ms wide, and latency is 3.17 ms. The sum (Violet) is unwindowed.

Let's you and them fight.

[See my beer bottle there? ]

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[Carlspeak]

YIKES! Got horns?? I surmize from the photo in post #27 of all the e-wave mods your bias clearly lies with horns. Are these all your 'babies' Zilch? That seems like a lot of hardware for someone who has a 'grille cloth emporioum'.

With each bounce, the intensity is diminished not only by the absorptive and diffusive qualities of the surface or object doing the reflecting, but also the increased path length getting to the listener. Draw the ray diagrams for your listening room to analyze this. Your dominant reverberant field is fiction.

The path of the first reflection from a speaker like AR3a is shown in Toole's Fig. 16.6. Toed-in such that the direct comes from 0° on-axis, and the reflection comes from -73° off-axis outboard. Alternatively, from flat against the front wall, the listener listens from 23° inboard and the reflection comes from 50° outboard. The intensities and spectral content of these off-axis sources are shown in Allison & Berkovitz.


Imagine that if you like, Howard, but it's make believe your talking here. AR3a's directivity is easily calculated from the Allison & Berkovitz data, and flat at Q=2 it's not; far from it, in fact.


You're talking to the guy with 100 CD waveguides, and presume he can't do it better? I can build a LST equivalent in approximately 27 seconds here with true, flat, uncontaminated constant directivity to 180° beamwidth and beyond. Yet you suppose nobody else has done this? It's routine in sound reinforcement, actually, and I have suggested how you might try it yourself at home for peanuts.


I do believe Ken got that; he also suggested why it likely failed.

You've been hyping your Allisons for 20 years now; the reverberant field dog don't hunt anymore....

[Zilch]

YIKES! Got horns?? I surmize from the photo in post #27 of all the e-wave mods your bias clearly lies with horns. Are these all your 'babies' Zilch? That seems like a lot of hardware for someone who has a 'grille cloth emporioum'.

That pic from over three years ago represents the culmination of "Quick and Dirty," a one-year-long pursuit of contemporary waveguide technology in comparison to horns, most all JBL, chronicled in LHF's first mega-thread, which grew so large during that time period it had to be split and indexed to fit in the database. I endured far worse abuse in the course of documenting that early work than has ever been mustered anywhere else, and was invited to leave on multiple occasions before the forum founder and administrator stepped in and added a DIY forum to accommodate such endeavors, which has now grown to the verge of eclipsing the original technical advice forum, formerly the site's primary focus, in popularity.

The good, the bad, the ugly, and the beautiful of what I did is available for perusal and reference, and despite moving elsewhere to pursue other endeavors, I remain the site's #2 most prolific (and to some, it's most infamous) contributor. The roots of E'Wave are clearly apparent in that pic and the thread itself. I am proud of what I did there, which has aged respectably over the intervening years, and freely share what I learned during the course of my tenure in LHF loudspeaker design boot camp with any who care to appreciate it. The quest for knowledge continues full tilt to this day, and I have many new friends worldwide to show for the effort....

[soundminded]

YIKES! Got horns?? I surmize from the photo in post #27 of all the e-wave mods your bias clearly lies with horns. Are these all your 'babies' Zilch? That seems like a lot of hardware for someone who has a 'grille cloth emporioum'.

Look in the back of it and you will see its tail. But be very careful not to turn around and lean over it its presence. If you do, you might wind up with a pitchfork in your rear channels.

[speaker dave]

Those more conventional jobs certainly had wide-enough dispersion, and of course they also did not have any of the horizontal interference effects that happened with the two-panel versions. They imaged better. However, the super-wide-radiating jobs, with their outputs being powerful to 135 degrees off axis, managed to bounce a huge amount of wide-bandwidth sound off of the front wall in a very immediate manner (remember, the two-panel jobs, as well as some of the single-panel jobs were designed to be located right up against the front wall to keep the woofer close enough to get away from mid-bass cancellation artifacts) and this tended to make them extremely spacious, as those reflections were subsequently bounced off of the side walls after the more direct signals were also bounced. Wide and spacious sounding as the more conventional systems were, the two-panel jobs were spacious in the extreme. Even Julian Hirsch admitted that he liked the effect, as did (and do) a number of the Allison fan club and other members of the wide-dispersion group. Those speakers have a kind of unique sound that few conventional speakers can duplicate.

Howard Ferstler

One thing to think about in this whole discussion of "what radiation pattern", "how wide a dispersion" is that, in the end, we are only marginally shifting the ratio of direct to reflected energy at a given point in the room. I know from experience that the waveguides that Zilch is a proponent of would have a d.i. of about 10dB (that is typical d.i. number of a 90 by 90 degree horn). If a front firing speaker has perfect omnidirectional radiation then it would have a d.i. of 3dB. A system with drivers on more than one face can have a lower d.i. and in fact a configuration such as a Bose 901 has effectively a negative d.i. Still, the difference of 7 dB for the two conventional systems would be similar to moving out to a little more than twice the listening distance from the more directional system. That is, the strength of the direct field relative to the reverberent could be set to any desired value by choosing your listening distance from either type of system. If you want a direct field dominated, very focused sound then sit closer. If you want the speakers to disappear and have a diffuse sound field, then back away from the system.

We know that this is the case, that leaning in towards our speakers gives a more detailed sound, sitting farther away a more diffuse sound. Based on this, how can anyone argue that a given dispersion pattern is right in absolute terms, anymore than it is right to prefer a seat in the balcony over a seat towards the front of the concert hall? That Dick Small and Neville Thiele seemed to favor a more direct sound field over a diffuse one is again a matter of taste rather than absolutes. Toole in his book talks of a number of "professional listeners" (studio workers) who, when comparing some diffuse speakers to some with more directional radiation, claimed that they would need the more directional systems to do their work, but might enjoy listening to the diffuse systems at home.

The argument regarding what exact frequency response the room reflections need to have (that it needs to be as flat as the direct sound) is an old but unproven one. I know that Daniel Queen was a big proponent of that but I don't think he offered any proof beyond "it ought to be a good thing". Certainly the notion that power response needs to be flat has been discredited by numerous experiments. The best test, as I quoted in another thread, was when Lipshitz and Vanderkooy experimented with independently manipulating the direct field and reverberent field from a speaker system. They strongly concluded that flat power response achieved by distorting the direct field was wrong (as you acknowledged, Howard) and that even achieving flat power response without distorting the direct field led to a system that was too bright.

If you look at Toole's early paper on rank ordering a group of 16 speakers, you will see that 3 of the top 4 systems in his blind listening test have significant holes in their total radiated power, Several lesser ranked speakers have both flatter and smoother total radiated power. The only conclusion to be drawn from this is that smooth and flat axial response is more important than smooth or flat power response.

David

[Zilch]

Look in the back of it and you will see its tail. But be very careful not to turn around and lean over it its presence. If you do, you might wind up with a pitchfork in your rear channels.

The spit has already been adeptly administered.

[The rotisserie is next.... ]

*******

I'm not finding where you asked for the data I posted at #42, but does the reverberant field CSD tell us anything about the nature of ZilchLab, the room?

Clearly, from the frequency responses, it is not significantly altering the spectral balance above the transition frequency....

[Zilch]

What is more interesting is the name of the speaker. Where do the people who design and market such items come up with those kinds of names, and what kind of individual would feel comfortable telling his friends that he owns a pair of Karma Indignias?

About 40 DIYers thus far, and Indignias are now receiving wider exposure elsewhere.

If you had read the thread, you'd know that the name derives from a serendipitous slip of the Zilchster's middle finger, AKA, "the bird."

Another open source design collaborative, there's no need to go madly clicking that one too, now, Howard; it's doing quite well presently, with its mere 946 posts and 42,461 views....

[Zilch]

1. It seems logical to me that one would want the broad-bandwidth radiating angle of any speaker system to be close to the same from top to bottom.

It's fundamental: bass is different, y'know -- wavelength, standing waves, room modes, nulls, transition frequency, all that stuff....

[Zilch]

I see the picture. What it lacks is additional arrows showing multiple reflections.

Speaker Dave has explained this to you, if I may paraphrase, "We don't listen with 22 ears."

Tell us again how important the medial front-wall reflection from ultra-wide dispersion speakers is, please, the ones you have damped with the drape there.

If you weren't running 7.1, I'd be suggesting you look up the absorptivity of wood paneling....

[soundminded]

Speaker Dave has explained this to you, if I may paraphrase, "We don't listen with 22 ears."

Tell us again how important the medial front-wall reflection from ultra-wide dispersion speakers is, please, the ones you have damped with the drape there.

If you weren't running 7.1, I'd be suggesting you look up the absorptivity of wood paneling....

Zilch, it must have occurred to even you that the only difference between listening to speakers in one room as opposed to another, or from being located in one position in the same room as opposed to another, or from an anechoic chamber for that matter is the reverberant field created by the room boundaries. Since it is common experience that the same speakers sound different from room to room, spot to spot, you don't need a mountain of data to come to the conclusion that the reverberant sound field is an overwhelming factor in practically any room and its specific nature bears heavily on what you will hear. It should also lead you to the conclusion that unless sound systems are engineered to compensate for these differences, no two sound systems will sound alike or for that matter even the same sound system rearranged in the same room will sound different. Yet knowing this, people who design these systems pay lip service at best to this inescapable fact. This leads to the inevitable conclusion that all of the words written about them notwithstanding and however successful their marketing was or how people like them, as an engineering effort to achieve a specific result they are all failures because the people who engineer them are clueless. Good engineers do not go into this field, it simply isn't important enough or challenging enough to warrant wasting an engineering career on. It's the reason I didn't.

[Zilch]

Zilch, it must have occurred to even you that the only difference between listening to speakers in one room as opposed to another, or from being located in one position in the same room as opposed to another, or from an anechoic chamber for that matter is the reverberant field created by the room boundaries.

There is no reverberant field of the nature found in large spaces such as concert halls as posited by Allison using the Beranek model and full-tilt embraced by Howard.

You're quick to assert that audio engineering has failed because the models are wrong, yet you rush to the front line to defend this outmoded one, long since repudiated?

Read the book.

[This is a diversionary tactic, obviously. You WANT everyone else to remain clueless to the very core.... ]

[soundminded]

There is no reverberant field of the nature found in large spaces such as concert halls as posited by Allison using the Beranek model and full-tilt embraced by Howard.

You're quick to assert that audio engineering has failed because the models are wrong, yet you rush to the front line to defend this outmoded one, long since repudiated?

Read the book.

[This is a diversionary tactic, obviously. You WANT everyone else to remain clueless to the very core.... ]

First of all, I am the first to agree that the revereberant sound fields in a home listening room have nothing in common with the reverberant fields of concert halls. Nothing. the implied assertion by Dr. Bose that somehow his direct reflecting 901 can reproduce concert hall acoustics is ludicrous.

But it is you who have consistently dismissed the importance of reverberant fields in listening rooms in the subjective performance of loudspeakers. That is clearly not the case as I have demonstrated by pointing out the reality that the same loudspeakers never sound the same in different rooms or in different locations in the same room.

I stick with my assertion that the engineering effort that has gone into studying loudspeaker performance and achieving a consistent goal within the restrictions of what such as device is capable of given the limitations of recordings is a miserable and failed engineering effort which in no way justifies the cost of most loudspeaker systems on the market today. And I re-assert my contention that the career possibilities open to anyone with an engineering education today given the many exciting avenues available to it would make it foolish to waste it on this unimportant and unchallenging area. It does make a fine hobby though.

[Zilch]

First of all, I am the first to agree that the revereberant sound fields in a home listening room have nothing in common with the reverberant fields of concert halls. Nothing. the implied assertion by Dr. Bose that somehow his direct reflecting 901 can reproduce concert hall acoustics is ludicrous.

And neither can wide dispersion. Villchur, Allison and Bose merely sing different renditions of the same '70s "Live Performance" song.

But it is you who have consistently dismissed the importance of reverberant fields in listening rooms in the subjective performance of loudspeakers. That is clearly not the case as I have demonstrated by pointing out the reality that the same loudspeakers never sound the same in different rooms or in different locations in the same room.

It's not coming from an imaginary isotropic integrating reverberant field, and assuming it is leads to erroneous conclusions which are unproductive, at best, but more commonly, detrimental to sonic quality.

What does Ken mean when he says "get beyond the fusion/coloration time" here:

http://www.classicsp...amp;#entry80050