Page 1 of 4 1234 LastLast
Results 1 to 10 of 39

Thread: Controlled directivity speakers

  1. #1
    Member Sponsor [WBF Founding Member] rblnr's Avatar
    Join Date
    May 2010
    Location
    NYC/NJ
    Posts
    1,833

    Controlled directivity speakers

    Most of you probably know this -- these are speakers designed to take the room out of the equation -- the radiation pattern above 100 - 200 hz usually is cardioid or heart shaped. The goal is to greatly reduce or eliminate the first reflections from the sidewalls and floor and ceiling. The reflections that do hit your ear are later in time and blur the sound less.

    Amphion, Gradient, Emerald Physics are some dynamic speakers that work this way, some horns works this way and some planars have a limited dispersion window or a null on either side as well. Some speakers have shallow waveguides on the tweeters that go part of the way toward controlled directivity and also increase efficiency.

    I own a pair of Amphion Ions and have heard Gradients several times -- the clarity and imaging you hear almost jumps out at you. Now there are other aspects that contribute to the success of each of these -- time alignment, open baffle design, first order crossover, dipole bass to name a few -- but the sound is very distinctive and true.

    As most rooms are untreated, and to the manufacturer, unpredictable, I wonder why more speakers aren't designed this way. Seems to make a lot of sense. Any ideas?

  2. #2
    WBF Technical Expert (Speaker & Acoustics) [Technical Expert] Mark Seaton's Avatar
    Join Date
    May 2010
    Location
    Chicago, IL
    Posts
    296
    Quote Originally Posted by rblnr View Post
    Most of you probably know this -- these are speakers designed to take the room out of the equation -- the radiation pattern above 100 - 200 hz usually is cardioid or heart shaped. The goal is to greatly reduce or eliminate the first reflections from the sidewalls and floor and ceiling. The reflections that do hit your ear are later in time and blur the sound less.
    Controlled directivity has become the latest buzzword used equal or more often by those who don't understand the realities as those who do.

    Some friends just did some comparisons with some quality speakers with very high directivity and were quickly sobered by the reality that it doesn't give you a free pass on the setup. Improved directivity *reduces* the early reflections and can greatly help with clarity, intelligibility and the audibility of natural decay in instruments and sounds.

    It can make a bad room sound less bad, and changes how the speakers interact with the room possibly changing where you might want to direct your first efforts in acoustic treatment. It won't "take the room out of the equation," but rather reduce the significance of the effect.

    Quote Originally Posted by rblnr View Post
    As most rooms are untreated, and to the manufacturer, unpredictable, I wonder why more speakers aren't designed this way. Seems to make a lot of sense. Any ideas?
    It's harder and requires much more understanding and measurement to get useful results. There are often more pitfalls in the various methods which need to be navigated to not destroy the many things home audio enthusiasts enjoy in the process of achieving more controlled directivity. The biggest hurdle faced is really the integration of the multiple devices used...

    Cardioids and dipoles allow a bit more flexibility, but by definition, most efforts to control directivity require minimum sizes to control above a given frequency. That required size almost insures significant spacing between one device and another in a 2, 3 or 4 way system. This spacing creates hurdles in maintaining smooth off axis response and can create strong lobes which make placement of a speaker more fickle. A good example would be old-school multi-way horns where many efforts had good performance per section, but the integration of the whole was always a major hurdle.

    As usual, blind pursuit of one metric can result in significant compromises in other very important qualities.

  3. #3
    [WBF Founding Member] kach22i's Avatar
    Join Date
    Apr 2010
    Location
    Ann Arbor, Michigan
    Posts
    974
    Quote Originally Posted by Mark Seaton View Post
    It won't "take the room out of the equation," but rather reduce the significance of the effect.
    Still, it would seem like a move in the right direction and does not require us to wear 3D glasses.
    George, Architect
    M/L Aerius + Tubes + Vinyl

  4. #4
    Member Sponsor [WBF Founding Member] rblnr's Avatar
    Join Date
    May 2010
    Location
    NYC/NJ
    Posts
    1,833
    Controlled directivity has become the latest buzzword used equal or more often by those who don't understand the realities as those who do.

    Some friends just did some comparisons with some quality speakers with very high directivity and were quickly sobered by the reality that it doesn't give you a free pass on the setup. Improved directivity *reduces* the early reflections and can greatly help with clarity, intelligibility and the audibility of natural decay in instruments and sounds.
    Didn't mean to suggest it's a free pass or no brainer. And some manufacturers have been at it for a long time, flavor of the month status notwithstanding.

    The speakers from Amphion and Gradient I've heard pull it off well. Difficulties acknowledged, the approach makes a ton of sense to me.

    Mark, can you elaborate on this:
    most efforts to control directivity require minimum sizes to control above a given frequency. That required size almost insures significant spacing between one device and another in a 2, 3 or 4 way system. This spacing creates hurdles in maintaining smooth off axis response and can create strong lobes which make placement of a speaker more fickle. A good example would be old-school multi-way horns where many efforts had good performance per section, but the integration of the whole was always a major hurdle.
    and btw, are you Chicago based? Am a native and go there all the time. Would love to hear your stuff if you're set up for that.

  5. #5
    WBF Technical Expert (Speaker & Acoustics) [Technical Expert] Mark Seaton's Avatar
    Join Date
    May 2010
    Location
    Chicago, IL
    Posts
    296
    Quote Originally Posted by kach22i View Post
    Still, it would seem like a move in the right direction and does not require us to wear 3D glasses.
    Absolutely. Sorry to be a bit of a wet blanket earlier.

    The point I should have more directly made is to check out speakers claiming such with interest, and quickly find out exactly what the manufacturer actually means by "controlled directivity."

    Cardioids and dipoles are the only ways to really shape directivity over the entire bandwidth, where most speakers shift toward full spherical radiation below some frequency. Where that happens and the nature of that transition from having directivity and not is a huge determinant in the realized benefits from a designers efforts to control directivity. Yes, talking about designs is much less exciting being a realist.

    Quote Originally Posted by rblnr View Post
    Didn't mean to suggest it's a free pass or no brainer. And some manufacturers have been at it for a long time, flavor of the month status notwithstanding.

    The speakers from Amphion and Gradient I've heard pull it off well. Difficulties acknowledged, the approach makes a ton of sense to me.
    My comments above weren't meant to imply it wasn't a very important and worthwhile goal. My point was to not transfer your experience with a few products talking about controlled directivity to all waving the flag. The few mentioned are much more the exception than the rule in the larger market.

    Mark, can you elaborate on this:
    most efforts to control directivity require minimum sizes to control above a given frequency. That required size almost insures significant spacing between one device and another in a 2, 3 or 4 way system. This spacing creates hurdles in maintaining smooth off axis response and can create strong lobes which make placement of a speaker more fickle. A good example would be old-school multi-way horns where many efforts had good performance per section, but the integration of the whole was always a major hurdle.
    Any horn, line or spaced set of drivers creating directivity in some or multiple axis will only do so above the frequency where the spacing is significant vs. the wavelength of the frequency being reproduced. As a general approximation, you find the start of forward directivity around and above the frequency where the spacing or size is around 1/2 wavelength (ex ~13.5" @ 500Hz or ~6.75" @ 1kHz) and the system is fully omnidirectional below roughly 1/8 wavelength (ex <125Hz for 13.5" or <250Hz for 6.75"). There are plenty of other variables relating to exactly how they behave in this range and above, including boundaries like the floor, but it is a very useful reality check to keep in mind, especially when we realize that similar directivity around 125Hz comes with dimensions of 54" (4.5 FEET!).

    A dipole or cardioid works from a somewhat different perspective, where you essentially trade off efficiency/output for size to get directivity from smaller devices.

    and btw, are you Chicago based? Am a native and go there all the time. Would love to hear your stuff if you're set up for that.
    I live at the north edge of the city and our office/warehouse is just outside of the NW city limits in Morton Grove. We don't yet have a demo system at our shop, but do have many customers who welcome demonstrations. Best bet is to post on our forum noting what you are interested in hearing or give us a call. There are some very nice systems with Catalysts in Michigan, near Atlanta, in the SF Bay Area, with SubMersives in in many places. Hopefully later this summer we'll have some better local options to have a listen. You are certainly welcome to come by and see what we're up to.

  6. #6
    Site Founder And Administrator Steve Williams's Avatar
    Join Date
    Mar 2010
    Location
    Coto De Caza, California on the 13th fairway of the south golf course
    Posts
    25,939
    Mark

    I wish I understood what you were saying. Great to see you posting here. You need to come to our BAAS mtg on June 27
    Steve Williams
    aka oneobgyn
    There's ALWAYS another Steve Williams BUT there's only "oneobgyn"
    International Distributor of Center Stage Feet and owner of PitchPerfect Sound (www.pitchperfectsound.com)
    Dealer Lamm Electronics
    My System

  7. #7
    WBF Technical Expert (Speaker & Acoustics) [Technical Expert] Mark Seaton's Avatar
    Join Date
    May 2010
    Location
    Chicago, IL
    Posts
    296
    Quote Originally Posted by Steve Williams View Post
    Mark

    I wish I understood what you were saying. Great to see you posting here. You need to come to our BAAS mtg on June 27
    Hi Steve,

    I don't believe I'll be in the area on the 27th, but I will be in the area in the next month or two for another meet in Berkeley. Hopefully you might be able to make that one this year. I will keep an eye on the BAAS meetings as it's not all that hard to get out to the area with many friends customers out there.

    As for understanding the above, the first concept of importance is wavelength. Sound propagates at a known speed through air plus/minus a small % for variations in temp, humidity and barometric pressure. The frequency tells us how often the pressure goes from zero-max-zero-min-zero and starts over again. 100Hz is 100 of these full cycles per second (=Hertz). 1000Hz is 10x as many of these cycles per second. Since sound propagates, a fixed distance will be covered during each cycle of max-min and back to zero. This distance is known as wavelength. Here is a simple image where you can visualize the relative increase and decrease of air pressure over distance for a constant sine wave. The top waves are of course for lower frequencies, and the lower waves are higher frequencies:


    Many things in acoustic behavior are directly related to wavelength or a fractional wavelength (1/2, 1/4 and 1/8th most commonly). Resistive treatments must be a significant fraction of a wavelength from a boundary (often thickness from the wall) to be effective. This is why 2" thick panels don't have much effect on the 108" wavelength of 125Hz.

    Similar ratios come into play with speaker operation. What we commonly call "beaming" of larger drivers or tweeters is this exact effect. 16kHz has a wavelength of ~0.85". A 1" or larger tweeter will be more directional at this high frequency where it is radiates without any directionality at 1/10th this frequency (1.6kHz) as the tweeter is very small as compared to this lower frequency. As with most things in sound, everything is relative.

    A bit easier to follow?

  8. #8
    Site Founder And Administrator Steve Williams's Avatar
    Join Date
    Mar 2010
    Location
    Coto De Caza, California on the 13th fairway of the south golf course
    Posts
    25,939
    definitely Mark

    It is refreshing for me to follow you and the growth of your company as all reports are nothing short of remarkable.
    Steve Williams
    aka oneobgyn
    There's ALWAYS another Steve Williams BUT there's only "oneobgyn"
    International Distributor of Center Stage Feet and owner of PitchPerfect Sound (www.pitchperfectsound.com)
    Dealer Lamm Electronics
    My System

  9. #9
    [WBF Founding Member] audioguy's Avatar
    Join Date
    Apr 2010
    Location
    Near Atlanta, GA but not too near!
    Posts
    2,573
    Steve: If you are planning on attending CEDIA this year (in Atlanta), let's set up a time for you to come by and hear Mark's speakers in a 2 channel environment (and HT if you wish)

  10. #10
    Member Sponsor [WBF Founding Member] rblnr's Avatar
    Join Date
    May 2010
    Location
    NYC/NJ
    Posts
    1,833
    Mark --

    Appreciate the primer. Obviously there's no free lunch anywhere. Like everything else, there is not necessarily a best technology, it's the quality of implementation that counts. I'd be interested to hear the what and whys of the initial design choices that go into your speakers. I'll make a point to listen to them.
    Last edited by rblnr; 06-10-2010 at 08:17 AM.

Page 1 of 4 1234 LastLast

Similar Threads

  1. A cool gadget for your yard: web controlled sprinkler
    By amirm in forum Home Automation & Remote Control Forum
    Replies: 7
    Last Post: 04-22-2015, 09:44 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •