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In Reply to: RE: Immersive posted by Duke on October 25, 2016 at 10:29:12
Would you care to name (or allude to) one or two of the "relatively few" speakers that come close to accomplishing this feat?Of course, you need not mention any of your own designs. For instance, I can recall how VMPS (now defunct) used to offer rear-firing or top-firing "ambience tweeters" as an add-on option for use with some of their loudspeakers. What do you think of Brian Cheney's old idea?
Also, in a "two stream paradigm" design, are the high-frequencies the most important part of the spectrum to get right? Is there, in fact, a "most important part" of the spectrum?
Edits: 10/25/16Follow Ups:
Dipoles positioned well out into the room meet the "Two Streams" criteria, as long as the spectral balance of the backwave is the same as that of the frontwave. Most omnis are going to have significant early sidewall interactions, unless the room is really big.I prefer to use controlled-pattern bipoles optimized for this application, for instance with the "rear" set of drivers firing from the floor up at the ceiling, which makes them more forgiving of placement near the "front" wall. Credit to James Romeyn for his "Late Ceiling Splash" idea, which I use with his permission. Credit also to Earl Geddes for something he taught me about the reverberant field.
In my opinion a speaker system's native off-axis response has to be taken into account if you want to add some additional drivers that would only cover part of the spectrum. Like if a speaker already has an off-axis flare at the lower end of the tweeter's range (where the tweeter's pattern is much wider than the midwoofer's), that would probably not be a good place to add a lot of additional reverberant energy. One reason why I shoot for fairly constant directivity with both sets of drivers is so that they "play nicely together", without putting too much reverberant energy into any part of the spectrum.
Rear-firing tweeters are usually added with the intention of correcting the reverberant field's relative level of upper frequency, to offset beaming of the front-firing tweeter. Imo this is definitely worth doing, but it isn't really a true "Two Streams" system even if you pull the speakers well out into the room.
I don't know how low in frequency you'd need to go with the rear-firing drivers. It probably depends somewhat on what the front woofer is doing, but I would guess you'd want to go down to at least 200 Hz. The "on axis" response of the rear-firing drivers would be of academic interest only; it is the power response that matters, along with enough directivity to keep sidelobes from becoming effectively "early reflections" in the midrange region.
Non-dipole speakers that meet the "Two Streams" criteria: Sonus Faber's expensive "Aida" uses what looks like a built-in rear-firing mini-monitor, and their "The Sonus Faber" model (now discontinued I think but it was their top of the line) had something similar that could be aimed to either side. ESP's new "Double Bass" speaker uses dual arrays firing in different directions. I think Definitive Technology still make bipolars. Imo the ESP "Double Bass" sounds absolutely magnificent. It's probably the best direct-radiator speaker I've heard, and is among the best speakers I've heard of any type.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Edits: 10/25/16 10/25/16 10/25/16 10/25/16 10/25/16
You say that the Prismas use "pattern control", which would seem to imply that their dispersion pattern is superior to that of more typical front-firing speakers. Or, is this simply another way of saying that the Prismas are optimized for placement near walls or corners?
Edits: 10/26/16
The rear-firing tweeter on the Prisma is compensation for the rectangular front horn's radiation pattern, which is narrower in the vertical plane than in the horizontal.
When I match up the horizontal radiation patterns of the woofer and horn in the crossover region, the reverberant field is "cheated" by the rectangular horn's narrower pattern in the vertical (which isn't necessarily all bad, as it reduces floor and ceiling interaction, and allows closer vertical center-to-center spacing of woofer and horn). The rear-firing tweeter adds just enough energy to the reverberant field to make up for the shortfall. The critical timing cues, as far as imaging goes, are all in the first-arrival sound.
Adding an essentially full-range rear-firing (or up-firing) section is a somewhat expensive proposition, both in drivers and in cabinetry. I've explored several driver options and settled on a part custom, part off-the-shelf solution which should allow me to do a Two Streams floor-stander in the same general price ballpark as the Prisma. It will have enough adjustability that against-the-wall placement will be feasible, and maybe even corner placement.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
OK, I'm guessing that your Prisma product page needs updating because the current specs make no mention of a "rear-firing tweeter"...Can you post pics of the new style Prisma speakers?
Edits: 10/27/16
You're right! Somehow the info on the rear-firing tweeter got dropped. Thanks for letting me know!
The "entry level Two Streams" speaker won't be a Prisma variant, it'll be its own thing. Soon as I have a production pair ready I'll take pictures, but I have a bit more prototyping to do first.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
I'm sure your new speaker will be at least as interesting as the Prisma is, or was.
IMO, your best looking speaker (so far) was the Jazz Module from several years ago. Any plans on going back to the circular horn shape?
I would prefer to reply to you privately, but your profile doesn't accept e-mails. Could you e-mail me?
Thanks!
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Email sent.
Good discussion so far. No offense to anyone, but 'audiophiles' are generally not knowledgeable in room acoustics nor the ear/brain hearing system. This often leads to inappropriate choices of loudspeakers for their listening environment. It's no wonder why "person A" says a speaker sounded excellent, and "person B" thinks they're so-so.As I've been preaching for 40 years, some speakers sound good in some rooms, and other speakers sound good in other rooms. On top of that, it also depends on the listener's preference: listening chair, or wide area coverage.
But an important fact which hasn't been mentioned in this thread is the fact that not all instruments radiate their sound in the same manner. A trumpet sounds very different at different angles from a flute or a timpani or a clarinet or the human voice. Yet, current technology limits us to reproducing all instruments via a single radiation pattern, which is not normal.
Lastly, someone here mentioned multi-channel systems. Back in 1975, I attempted to design a massively multi-channel system which would create a more believable and natural sound field. The big problems were installing and managing seven front channels and 30 or so ceiling, left, right and rear channels.
:)
Edits: 10/26/16
"But an important fact which hasn't been mentioned in this thread is the fact that not all instruments radiate their sound in the same manner. A trumpet sounds very different at different angles from a flute or a timpani or a clarinet or the human voice. Yet, current technology limits us to reproducing all instruments via a single radiation pattern, which is not normal."
Assuming the recording has captured a good representation of the reverberant energy of these different instruments, I think a good Two Streams setup has a better chance than most systems of delivering that reverberant energy in a convincing manner. This probably sounds counter-intuitive, as at first glance it looks like we're adding "more listening room" sound to the presentation, but I think the ear/brain system can do a better job of picking out the reverberant energy on the recording when it's presented this way, rather than only coming from the front of the speakers. See my post linked below, which offers some anecdotal evidence of this.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
They can do a reasonably good job, if the back wave is defused and the timing is right.
I used to have Snell B Minors, that had a rear firing tweeter. It did add a fair amount of air to the music but that's a little different.
Jack
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